首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   26822篇
  免费   1810篇
  国内免费   117篇
耳鼻咽喉   227篇
儿科学   707篇
妇产科学   449篇
基础医学   3913篇
口腔科学   366篇
临床医学   2532篇
内科学   6469篇
皮肤病学   693篇
神经病学   2221篇
特种医学   975篇
外国民族医学   3篇
外科学   3819篇
综合类   293篇
一般理论   28篇
预防医学   1978篇
眼科学   501篇
药学   1642篇
  1篇
中国医学   57篇
肿瘤学   1875篇
  2022年   113篇
  2021年   343篇
  2020年   229篇
  2019年   368篇
  2018年   438篇
  2017年   300篇
  2016年   363篇
  2015年   431篇
  2014年   636篇
  2013年   968篇
  2012年   1414篇
  2011年   1567篇
  2010年   980篇
  2009年   991篇
  2008年   1501篇
  2007年   1672篇
  2006年   1661篇
  2005年   1775篇
  2004年   1609篇
  2003年   1529篇
  2002年   1521篇
  2001年   410篇
  2000年   339篇
  1999年   404篇
  1998年   423篇
  1997年   381篇
  1996年   339篇
  1995年   309篇
  1994年   294篇
  1993年   265篇
  1992年   317篇
  1991年   305篇
  1990年   271篇
  1989年   266篇
  1988年   257篇
  1987年   230篇
  1986年   242篇
  1985年   245篇
  1984年   212篇
  1983年   201篇
  1982年   228篇
  1981年   238篇
  1980年   191篇
  1979年   143篇
  1978年   138篇
  1977年   144篇
  1976年   125篇
  1975年   114篇
  1974年   102篇
  1973年   94篇
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
991.

Aims/hypothesis

The double-blind Trial Comparing Cardiovascular Safety of Insulin Degludec vs Insulin Glargine in Patients with Type 2 Diabetes at High Risk of Cardiovascular Events (DEVOTE) assessed the cardiovascular safety of insulin degludec. The incidence and rates of adjudicated severe hypoglycaemia, and all-cause mortality were also determined. This paper reports a secondary analysis investigating associations of severe hypoglycaemia with cardiovascular outcomes and mortality.

Methods

In DEVOTE, patients with type 2 diabetes were randomised to receive either insulin degludec or insulin glargine U100 (100 units/ml) once daily (between dinner and bedtime) in an event-driven, double-blind, treat-to-target cardiovascular outcomes trial. The primary outcome was the first occurrence of an adjudicated major adverse cardiovascular event (MACE; cardiovascular death, non-fatal myocardial infarction or non-fatal stroke). Adjudicated severe hypoglycaemia was the pre-specified secondary outcome. In the present analysis, the associations of severe hypoglycaemia with both MACE and all-cause mortality was evaluated in the pooled trial population using time-to-event analyses, with severe hypoglycaemia as a time-dependent variable and randomised treatment as a fixed factor. An investigation with interaction terms indicated that the effect of severe hypoglycaemia on the risk of MACE and all-cause mortality were the same for both treatment arms, and so the temporal association for severe hypoglycaemia with subsequent MACE and all-cause mortality is reported for the pooled population.

Results

There was a non-significant difference in the risk of MACE for individuals who had vs those who had not experienced severe hypoglycaemia during the trial (HR 1.38, 95% CI 0.96, 1.96; p = 0.080) and therefore there was no temporal relationship between severe hypoglycaemia and MACE. There was a significantly higher risk of all-cause mortality for patients who had vs those who had not experienced severe hypoglycaemia during the trial (HR 2.51, 95% CI 1.79, 3.50; p < 0.001). There was a higher risk of all-cause mortality 15, 30, 60, 90, 180 and 365 days after experiencing severe hypoglycaemia compared with not experiencing severe hypoglycaemia in the same time interval. The association between severe hypoglycaemia and all-cause mortality was maintained after adjustment for the following baseline characteristics: age, sex, HbA1c, BMI, diabetes duration, insulin regimen, hepatic impairment, renal status and cardiovascular risk group.

Conclusions/interpretation

The results from these analyses demonstrate an association between severe hypoglycaemia and all-cause mortality. Furthermore, they indicate that patients who experienced severe hypoglycaemia were particularly at greater risk of death in the short term after the hypoglycaemic episode. These findings indicate that severe hypoglycaemia is associated with higher subsequent mortality; however, they cannot answer the question as to whether severe hypoglycaemia serves as a risk marker for adverse outcomes or whether there is a direct causal effect.

Trial registration

ClinicalTrials.gov NCT01959529
  相似文献   
992.
PURPOSE: National Surgical Adjuvant Breast and Bowel Project Protocol R-03 was designed to determine the worth of preoperative chemotherapy and radiation therapy in the management of operable rectal cancer. METHODS: Thus far, 116 patients of an eventual 900 with primary operable rectal cancer have been randomized to receive multimodality therapy to begin preoperatively (59 patients) or identical therapy beginning after curative surgery (57). All patients received seven cycles of 5-fluorouracil (FU)/leucovorin (LV) chemotherapy. Cycles 1 and 4 through 7 used a high-dose weekly FU regimen. In Cycles 2 and 3, FU and low-dose LV chemotherapy was given during the first and fifth week of radiation therapy (5,040 cGy). The preoperative arm (Group 1) received the first three cycles of chemotherapy and all radiation therapy before surgery. The postoperative arm (Group 2) received all radiation and chemotherapy after surgery. Primary study end points included disease-free survival and survival. Secondary end points included local recurrence, primary tumor response to combination therapy, tumor downstaging, and sphincter preservation. RESULTS: Overall treatment-related toxicity was similar in both groups. Although seven preoperative patients had events after randomization that precluded surgery, eight events occurred during an equivalent follow-up period in the postoperative group. No patient was deemed inoperable because of progressive local disease. Sphincter-saving surgery was intended in 31 percent of Group 1 patients and 33 percent of Group 2 patients at the time of randomization. Such surgery was actually performed in 50 percent of the preoperatively treated patients and 33 percent of the postoperatively treated patients. The use of protective colostomy in patients undergoing sphincter-sparing surgery and the development of perioperative complications in all surgical patients were similar in both groups. There was evidence of tumor downstaging in evaluable patients under-going preoperative therapy, with 8 percent of Group 1 patients having had a pathologic complete response. CONCLUSION: These data do suggest that the preoperative chemotherapy and radiation therapy regimen used are, at least, as safe and tolerable as standard postoperative treatment. There is presently a trend to tumor downstaging and sphincter preservation in the preoperative arm. Whether this arm will have greater or lesser survival and long-term toxicity awaits the completion of this relevant study.Supported by National Cancer Institute Grants U10-CA-12027 and U10-CA-37377 and American Cancer Society Grant R-13.Read at the meeting of The American Society of Colon and Rectal Surgeons, Seattle, Washington, June 9 to 14, 1996.  相似文献   
993.
BACKGROUND: Patients with cirrhosis and tense ascites treated by paracentesis alone have a decrease in effective arterial blood volume after ascites removal. Although intravenous albumin is effective in preventing paracentesis induced decreased arterial blood volume, its clinical use is controversial. As paracentesis induces arteriolar vasodilation which plays a role in the development of decreased effective arterial blood volume, administration of a vasoconstrictor (terlipressin) could prevent circulatory alterations due to paracentesis. AIMS: To perform a pilot study comparing the effects of terlipressin and albumin on effective arterial blood volume in patients with cirrhosis treated by paracentesis for tense ascites. METHODS: Twenty patients with cirrhosis and tense ascites were randomly assigned to be treated by either paracentesis and terlipressin or paracentesis and albumin. Terlipressin (3 mg) or albumin (8 g/l of removed ascites) were administered on the day of paracentesis. Effective arterial blood volume was assessed by measuring plasma renin concentrations at baseline and on the day of hospital discharge (4-6 days after treatment). Decreased effective arterial blood volume was defined as an increase in plasma renin concentrations on the day of hospital discharge of more than 50% of baseline values. RESULTS: Irrespective of the treatment group, mean values for plasma renin concentrations at hospital discharge did not differ from their respective baseline values (p=0.10). Baseline plasma levels of renin concentrations did not differ between the terlipressin and albumin groups (p=0.61). Changes from baseline in plasma renin concentrations did not differ between groups (p=0.39). Three patients in the terlipressin group and three in the albumin group developed decreased arterial blood volume. CONCLUSIONS: This randomised pilot study suggests that terlipressin may be as effective as intravenous albumin in preventing a decrease in effective arterial blood volume in patients with cirrhosis treated by paracentesis for tense ascites.  相似文献   
994.
Mitochondrial injury in steatohepatitis   总被引:9,自引:0,他引:9  
Rich diet and lack of exercise are causing a surge in obesity, insulin resistance and steatosis, which can evolve into steatohepatitis. Patients with non-alcoholic steatohepatitis have increased lipid peroxidation, increased tumour necrosis factor-alpha (TNF-alpha) and increased mitochondrial beta-oxidation rates. Their in-vivo ability to re-synthesize ATP after a fructose challenge is decreased, and their hepatic mitochondria exhibit ultrastructural lesions, depletion of mitochondrial DNA and decreased activity of respiratory chain complexes. Although the mechanisms for these effects is unknown, the basal cellular formation of reactive oxygen species (ROS) may oxidize fat deposits to cause lipid peroxidation, which damages mitochondrial DNA, proteins and cardiolipin to partially hamper the flow of electrons within the respiratory chain. This flow may be further decreased by TNF-alpha, which can release cytochrome c from mitochondria. Concomitantly, the increased mitochondrial fatty acid beta-oxidation rate augments the delivery of electrons to the respiratory chain. Due to the imbalance between a high electron input and a restricted outflow, electrons may accumulate within complexes I and III, and react with oxygen to form the superoxide anion radical. Increased mitochondrial ROS formation could in turn directly oxidize mitochondrial DNA, proteins and lipids, enhance lipid peroxidation-related mitochondrial damage, trigger hepatic TNF-alpha formation and deplete antioxidants, thus further blocking electron flow and further increasing mitochondrial ROS formation. Mitochondrial dysfunction plays an important role in liver lesions, through the ROS-induced release of both biologically active lipid peroxidation products and cytokines. In particular, the up-regulation of both TNF-alpha and Fas triggers mitochondrial membrane permeability and apoptosis. The ingestion of apoptotic bodies by stellate cells stimulates fibrogenesis, which is further activated by lipid peroxidation products and high leptin levels. Chronic apoptosis is compensated by increased cell proliferation, which, together with oxidative DNA damage, may cause gene mutations and cancer.  相似文献   
995.
Twenty-three chronic alcoholics were investigated by means of pulmonary function studies. All 23 patients had respiratory symptoms. Clinically, 21 (91 per cent) of 23 patients were diagnosed as having chronic bronchitis, and 14 patients (60 per cent) had dyspnea. The maximal mid-expiratory flow and single breath diffusing capacity for carbon monoxide (SBDCO) were abnormal in 16 (70 per cent) and 14 (61 per cent) patients, respectively. Twenty-two of 23 patients had one or more abnormal function. The total lung capacity, residual volume, vital capacity, 1 second forced expiratory volume and SBDCO progressively declined with increasing alcohol consumption. An attempt was made to separate the pulmonary effects of alcohol from (1) the effects of previous pulmonary infections, (2) the effects of cigarette smoking, and (3) the effects of cirrhosis of the liver. The data suggest that either alcohol itself through some unknown mechanism may be a causative agent in producing lung disease or that alcohol makes a higher percentage of the population susceptible to the harmful effects of cigarette smoking.  相似文献   
996.
Modified vaccinia virus Ankara (MVA), developed >30 years ago as a highly attenuated candidate smallpox vaccine, was recloned from a 1974 passage and evaluated for safety and immunogenicity. Replication of MVA is impaired in most mammalian cells, and we found that mice with severe combined immunodeficiency disease remained healthy when inoculated with MVA at 1,000 times the lethal dose of vaccinia virus derived from the licensed Dryvax vaccine seed. In BALB/c mice inoculated intramuscularly with MVA, virus-specific CD8+ T cells and antibodies to purified virions and membrane protein components of the intracellular and extracellular infectious forms of vaccinia virus were induced in a dose-dependent manner. After one or two inoculations of MVA, the T cell numbers and antibody titers equaled or exceeded those induced by percutaneous injection of Dryvax. Antibodies induced by MVA and Dryvax were neutralizing and inhibited virus spread in cultured cells. Furthermore, vaccinated mice were protected against lethal intranasal challenge with a pathogenic vaccinia virus. B cell-deficient mice unable to generate antibodies and beta2-microglobulin-deficient mice unable to express MHC class I molecules for a CD8+ T cell response were also protectively vaccinated by MVA. In contrast, mice with decreased CD4 or MHC class II expression and double-knockout mice deficient in MHC class I- and II-restricted activities were poorly protected or unprotected. This study confirmed the safety of MVA and demonstrated that the overlapping immune responses protected normal and partially immune-deficient animals, an encouraging result for this candidate attenuated smallpox vaccine.  相似文献   
997.

Objectives

This study sought to describe the current practices and compare outcomes according to the use of balloon aortic valvuloplasty (BAV) or not during transcatheter aortic valve replacement (TAVR).

Background

Since its development, aortic valve pre-dilatation has been an essential step of TAVR procedures. However, the feasibility of TAVR without systematic BAV has been described.

Methods

TAVR performed in 48 centers across France between January 2013 and December 2015 were prospectively included in the FRANCE TAVI (Registry of Aortic Valve Bioprostheses Established by Catheter) registry. We compared outcomes according to BAV during the TAVR procedure.

Results

A total of 5,784 patients have been included in our analysis, corresponding to 2,579 (44.6%) with BAV avoidance and 3,205 (55.4%) patients with BAV performed. We observed a progressive decline in the use of BAV over time (78% of procedures in 2013 and 49% in the last trimester of 2015). Avoidance of BAV was associated with similar device implantation success (97.3% vs. 97.6%; p = 0.40). TAVR procedures without BAV were quicker (fluoroscopy 17.2 ± 9.1 vs. 18.5 ± 8.8 min; p < 0.01) and used lower amounts of contrast (131.5 ± 61.6 vs. 141.6 ± 61.5; p < 0.01) and radiation (608.9 ± 576.3 vs. 667.0 ± 631.3; p < 0.01). The rates of moderate to severe aortic regurgitation were lower with avoidance of BAV (8.3% vs. 12.2%; p < 0.01) and tamponade rates (1.5% vs. 2.3%; p = 0.04).

Conclusions

We confirmed that TAVR without BAV is frequently performed in France with good procedural results. This procedure is associated with procedural simplification and lower rates of residual aortic regurgitation.  相似文献   
998.
The functional capacities of granulocytes in patients with chronic granulocytic leukemia are still a subject of controversy, probably due to the heterogeneity of the abnormalities observed from patient to patient. For a better definition of these abnormalities, 14 patients with untreated chronic granulocytic leukemia were studied. The patients were divided into three groups on the basis of the functional activities of their phagocytosing granulocytes. In four patients (group I), the granulocytes were normal in respect to particle ingestion, nitroblue tetrazolium (NBT)-stimulated reduction, cyanide-insensitive oxygen (O2) consumption, superoxide anion (O2-)-stimulated production, hydrogen peroxide (H2O2) production, and iodination. They also had a normal myeloperoxidase (MPO) content. In four patients (group III), the granulocytes were significantly defective in all of these activities. In the six remaining patients (group II), all the initial metabolic steps of the phagocytosing granulocytes (ingestion, NBT reduction, O2 consumption, O2-production, H2O2 production) were normal, as were the MPO content of the granulocytes, while iodination was strikingly decreased. These metabolic features suggested a degranulation defect which was observed ultrastructurally in the only patient studied among these six. The phagocytosing granulocytes of this patient did not degranulate and no deposits of MPO activity were seen in the phagosomes.  相似文献   
999.
Patch–clamp recordings of CA1 interneurons and pyramidal cells were performed in hippocampal slices from kainate- or pilocarpine-treated rat models of temporal lobe epilepsy. We report that γ-aminobutyric acid (GABA)ergic inhibition in pyramidal neurons is still functional in temporal lobe epilepsy because: (i) the frequency of spontaneous GABAergic currents is similar to that of control and (ii) focal electrical stimulation of interneurons evokes a hyperpolarization that prevents the generation of action potentials. In paired recordings of interneurons and pyramidal cells, synchronous interictal activities were recorded. Furthermore, large network-driven GABAergic inhibitory postsynaptic currents were present in pyramidal cells during interictal discharges. The duration of these interictal discharges was increased by the GABA type A antagonist bicuculline. We conclude that GABAergic inhibition is still present and functional in these experimental models and that the principal defect of inhibition does not lie in a complete disconnection of GABAergic interneurons from their glutamatergic inputs.  相似文献   
1000.
OBJECTIVE: To determine whether patient's sex influences the severity of rheumatoid arthritis (RA) in terms of clinical severity or need for treatments. METHODS: This was a retrospective, single-center study. We compared 133 male patients with 133 female patients presenting with RA and matched for disease duration. Data collection included demographic characteristics, pattern of joint involvement, extraarticular manifestations, medical treatment, and joint surgery. Biological measures, HLA genotypes, Larsen radiological scores on radiographs of hands and feet, and Health Assessment Questionnaire (HAQ) results were obtained. RESULTS: Mean disease duration was 7.4 +/- 6.9 years. Concerning clinical pattern of involvement, sicca syndrome was more frequent in women than in men (p = 0.0003). There were no significant differences concerning absence or presence of at least one disease associated gene (HLA-DRB1*01 or *04) in our patients; however, women more often carried 2 disease associated genes (21% vs 11%). No other difference in clinical, biological, or radiological indicators was noted between the 2 populations. Concerning treatment, there was no difference for large joint arthroplasties; female patients underwent significantly more distal joint arthrodesis, 6.7% vs 1.5% (p = 0.03); they were prescribed slightly more disease modifying drugs, 3.33 vs 2.83 (p = 0.04); and showed a trend toward more large joint arthrodesis, 15% vs 7.5% (p = 0.05), and metacarpophalangeal joint arthroplasties, 5.2% vs 0.7% (p = 0.08). CONCLUSION: When patients are matched for RA duration, sex has little effect on the disease pattern and severity, yet women undergo more distal joint surgery.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号