全文获取类型
收费全文 | 13512篇 |
免费 | 1024篇 |
国内免费 | 39篇 |
专业分类
耳鼻咽喉 | 82篇 |
儿科学 | 244篇 |
妇产科学 | 237篇 |
基础医学 | 1936篇 |
口腔科学 | 433篇 |
临床医学 | 1748篇 |
内科学 | 2666篇 |
皮肤病学 | 275篇 |
神经病学 | 1114篇 |
特种医学 | 568篇 |
外科学 | 1976篇 |
综合类 | 86篇 |
一般理论 | 2篇 |
预防医学 | 1197篇 |
眼科学 | 243篇 |
药学 | 844篇 |
中国医学 | 34篇 |
肿瘤学 | 890篇 |
出版年
2023年 | 79篇 |
2022年 | 82篇 |
2021年 | 226篇 |
2020年 | 157篇 |
2019年 | 221篇 |
2018年 | 281篇 |
2017年 | 259篇 |
2016年 | 250篇 |
2015年 | 234篇 |
2014年 | 360篇 |
2013年 | 516篇 |
2012年 | 702篇 |
2011年 | 751篇 |
2010年 | 373篇 |
2009年 | 334篇 |
2008年 | 611篇 |
2007年 | 623篇 |
2006年 | 588篇 |
2005年 | 519篇 |
2004年 | 507篇 |
2003年 | 449篇 |
2002年 | 423篇 |
2001年 | 360篇 |
2000年 | 445篇 |
1999年 | 381篇 |
1998年 | 174篇 |
1997年 | 135篇 |
1996年 | 128篇 |
1995年 | 130篇 |
1994年 | 120篇 |
1993年 | 114篇 |
1992年 | 321篇 |
1991年 | 328篇 |
1990年 | 324篇 |
1989年 | 269篇 |
1988年 | 250篇 |
1987年 | 283篇 |
1986年 | 264篇 |
1985年 | 209篇 |
1984年 | 208篇 |
1983年 | 183篇 |
1982年 | 99篇 |
1981年 | 81篇 |
1979年 | 124篇 |
1978年 | 88篇 |
1977年 | 81篇 |
1975年 | 76篇 |
1974年 | 75篇 |
1973年 | 81篇 |
1970年 | 72篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Risk factors for parvovirus B19 infection in pregnancy 总被引:3,自引:0,他引:3
Valeur-Jensen AK Pedersen CB Westergaard T Jensen IP Lebech M Andersen PK Aaby P Pedersen BN Melbye M 《JAMA》1999,281(12):1099-1105
Context Parvovirus B19 infection during pregnancy has been associated with fetal death. However, the incidence of and risk factors for infection in pregnant women have not been well studied. Objectives To estimate a pregnant woman's risk of infection with parvovirus B19 in epidemic and endemic situations and to study risk factors for infection. Design Population-based cohort study conducted between November 1992 and June 1994. Setting Three regions in Denmark. Participants A total of 30,946 pregnant women from a consecutive and population-based screening. Main Outcome Measures Specific IgG antibodies in serum samples obtained in the first trimester of pregnancy and from the newborn infant to assess past infection and seroconversion. Information on family structure, educational background, socioeconomic status, and pregnancy outcome was obtained from national registers. Results Based on 30,946 serum samples, 65.0% of pregnant women had evidence of past infection. Annual seroconversion rates among susceptible women during endemic and epidemic periods were 1.5% (95% confidence interval [CI], 0.2%-1.9%) and 13.0% (95% CI, 8.7%-23.1%), respectively. Baseline seropositivity was significantly correlated with increasing number of siblings, having a sibling of the same age, number of own children, and occupational exposure to children. Risk of acute infection increased with the number of children in the household as follows: 0 children odds ratio (OR), 1 (reference); 1 child OR, 3.17 (95% CI, 2.24-4.49); 2 children OR, 5.47 (95% CI, 3.55-8.45); 3 or more children OR, 7.54 (95% CI, 3.80-14.94). Having children aged 6 to 7 years resulted in the highest rate of seroconversion among mothers (6.8%; OR, 4.07; 95% CI, 1.89-8.73). Compared with other pregnant women, nursery school teachers had a 3-fold increased risk of acute infection (OR, 3.09; 95% CI, 1.62-5.89). Population-attributable risk of seroconversion was 55.4% for number of own children and 6.0% for occupational exposure. Conclusions The risk of infection is high for susceptible pregnant women during epidemics and associated with the level of contact with children. Nursery school teachers have the highest occupational risk, but most infections seem to be the result of exposure to the woman's own children. 相似文献
992.
I. S. Haldorsen M. Vesterhus H. Ræder D. K. Jensen O. Søvik A. Molven P. R. Njølstad 《Diabetic medicine》2008,25(7):782-787
Aims Hepatocyte nuclear factor 1B (HNF1B) gene mutation carriers have a systemic disease characterized by congenital malformations in the urogenital tract, diabetes mellitus of maturity‐onset diabetes of the young type and dysfunction of the liver and exocrine pancreas. We aimed to investigate pancreatic structure and exocrine function in carriers of HNF1B mutations. Methods We studied five subjects from two families with the previously reported mutation R137_K161del and the novel mutation F148L in HNF1B. All patients underwent computed tomography (CT) and magnetic resonance cholangiopancreatography (MRCP). We measured faecal elastase and serum vitamins D and E. Results One of the mutation carriers reported abdominal symptoms. All five subjects had faecal elastase deficiency, three had vitamin D deficiency and two had vitamin E deficiency. Neither CT nor MRCP depicted tissue corresponding to the pancreatic body and tail in the five mutation carriers, indicating agenesis of the dorsal pancreas. The head of the pancreas was slightly atrophic but had normal X‐ray attenuation at CT in all patients. Conclusions Agenesis of the pancreatic body and tail and pancreatic exocrine dysfunction are parts of the phenotype in HNF1B mutation carriers. This strengthens the evidence for a critical role of HNF1B in development and differentiation of at least the dorsal pancreas. 相似文献
993.
K W Garey S L Pendland V T Huynh T H Bunch G M Jensen K J Pursell 《Pharmacotherapy》2001,21(7):855-860
Infections caused by Cunninghamella bertholletiae, an opportunistic fungal organism, have an extremely high mortality rate. A fatal case of C. bertholletiae fungal pneumonia occurred in a man who had received an allogeneic bone marrow transplant. Aggressive debridement and high-dose liposomal amphotericin B failed to eradicate the infection. Right lung tissue samples obtained during lobectomy were assayed for amphotericin B concentrations by high-performance liquid chromatography, and minimum inhibitory concentration (MIC) determinations of amphotericin B against C. bertholletiae were determined by the macrobroth dilution method. The MIC for the isolate of C. bertholletiae was 4 microg/ml. Amphotericin B lung concentrations averaged 9.5 microg/ml (range 3.7-13.8 microg/ml), with a corresponding serum trough concentration of 0.9 microg/ml. To our knowledge, this is the first reported case of amphotericin B concentrations measured at the site of infection in a patient with a pulmonary Cunninghamella infection, together with a corresponding MIC of the organism. The patient's death, which occurred despite aggressive debridement and high amphotericin B lung concentrations, highlights the need for novel strategies to treat infections caused by invasive molds such as C. bertholletiae. 相似文献
994.
Brent P. Forester Yosef A. Berlow David G. Harper J. Eric Jensen Nicholas Lange Michael P. Froimowitz Caitlin Ravichandran Dan V. Iosifescu Scott E. Lukas Perry F. Renshaw Bruce M. Cohen 《NMR in biomedicine》2010,23(3):242-250
Evidence suggests that mitochondria undergo functional and morphological changes with age. This study aimed to investigate the relationship of brain energy metabolism to healthy aging by assessing tissue specific differences in metabolites observable by phosphorus (31P) MRS. 31P MRSI at 4 Tesla (T) was performed on 34 volunteers, aged 21–84, screened to exclude serious medical and psychiatric diagnoses. Linear mixed effects models were used to analyze the effects of age on phosphorus metabolite concentrations, intracellular magnesium and pH estimates in brain tissue. A significant age associated decrease in brain pH (?0.53% per decade), increase in PCr (1.1% per decade) and decrease in PME (1.7% per decade) were found in total tissue, with PCr effects localized to the gray matter. An increase in beta NTP as a function of age (1% per decade) approached significance (p = 0.052). There were no effects demonstrated with increasing age for intracellular magnesium, PDE or inorganic phosphate. This study reports the effects of healthy aging on brain chemistry in the gray matter versus white matter using 31P MRS measures of high energy phosphates, pH and membrane metabolism. Increased PCr, increased beta NTP (reflecting ATP) and reduced pH may reflect altered energy production with healthy aging. Unlike some previous studies of aging and brain chemistry, this study examined healthy, non‐demented and psychiatrically stable older adults and specifically analyzed gray‐white matter differences in brain metabolism. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
995.
Bo Feldt-Rasmussen Kirsten Nørgaard Tonny Jensen Elisabeth Mathiesen Torsten Deckert 《Acta diabetologica》1990,27(2):173-179
Summary Which comes first when developing clinical diabetic nephropathy, the blood pressure rise or the increasing urinary albumin
excretion? This issue is discussed based on recent literature of studies in humans with Type 1 (insulin-dependent) diabetes
mellitus. We conclude that hypertension has a central role in the progression of diabetic nephropathy and has deleterious
effects on the life expectancy of patients who already have signs of diabetic renal disease in terms of elevated urinary albumin
excretion. However, blood pressure is preceded by small increments of urinary albumin excretion rates, an indicator of a universally
increased vascular leakiness, and thus does not seem to be the cause of diabetic nephropathy. 相似文献
996.
B Feldt-Rasmussen T Jensen H Dieperink T Mandrup-Poulsen J Nerup K Bendtzen V Andersen E Kemp P P Leyssac 《Diabetic medicine》1990,7(5):429-433
Renal function was studied in 18 patients with Type 1 diabetes mellitus. All were participating in the Canadian-European randomized placebo-controlled cyclosporin trial in newly diagnosed Type 1 diabetic patients, nine being randomized to placebo, and nine to cyclosporin A. During treatment for 12 to 18 months, cyclosporin A caused significant reductions in the glomerular filtration rate (before drug withdrawal, cyclosporin 97 +/- 18 vs placebo 125 +/- 16 ml min-1 1.73-m-2, p less than 0.05), renal plasma flow (454 +/- 83 vs 536 +/- 70 ml min-1 1.73-m-2, p less than 0.05), and lithium clearance (17 +/- 3 vs 28 +/- 5 ml min-1 1.73-m-2, p less than 0.05). The fractional proximal reabsorption was increased (0.82 +/- 0.03 vs 0.78 +/- 0.03, p less than 0.05), and the fractional distal sodium reabsorption reduced (0.88 +/- 0.03 vs 0.94 +/- 0.02, p less than 0.05). These results are in accordance with the hypothesis that the nephrotoxic effect of cyclosporin A results from a preferential constriction of afferent glomerular vessels. One year after withdrawal of the drug, all variables were similar in the two groups, except for blood glucose control which was worse in the cyclosporin A treated group. When corrected for differences in blood glucose control it appeared that in three out of nine patients glomerular filtration rate had not completely returned to the reference range of the placebo group. We conclude that the nephrotoxic side-effects of cyclosporin A treatment for 1 year are reversible. There are, however, signs of minor and perhaps chronic renal injury. 相似文献
997.
Holger C. Eberle Kai Nassenstein Christoph J. Jensen Thomas Schlosser Georg V. Sabin Christoph K. Naber Oliver Bruder 《European radiology》2010,20(1):73-80
We compared four-dimensional guide-point modelling left ventricular function analysis (4DVF) results of cine images in four short-axis and two long-axis slices acquired in a single breath-hold, obtained with the temporal parallel acquisition technique (TPAT), with standard left ventricular function (LVF) analysis results determined by the summation of discs method, in patients who had recently suffered myocardial infarction. Despite wall motion abnormalities, 4DVF yields results for left ventricular ejection fractions and end-diastolic and end-systolic volumes that are in excellent agreement with standard LVF analysis results in these patients. A shortened cardiac magnetic resonance (CMR) protocol using single breath-hold cine image acquisition could facilitate the assessment of left ventricular function soon after myocardial infarction in critically ill patients who are unable to comply with the multiple breath-holds required for standard LVF analysis. 相似文献
998.
L. Christiansen A. Bygum A. Jensen F. Brandrup K. Thomsen M. Hørder N. E. Petersen 《Scandinavian journal of clinical and laboratory investigation》2013,73(7):611-616
Decreased uroporphyrinogen decarboxylase (UROD) activity is a characteristic feature of the most common of the porphyrias, porphyria cutanea tarda (PCT). A subgroup of the clinically overt PCT cases is associated with mutations in the gene encoding UROD and inherited as an autosomal-dominant trait. In this study, DNAs from 53 Danish PCT patients were subjected to genetic analysis for UROD mutations using denaturing gradient gel electrophoresis. Eleven genetic variations, seven of which are possible disease causing, were identified. All but one of these mutations were previously unknown, lending further support to the assumption that PCT is a heteroallelic disease. Only 11% of the examined patients were previously recognized as familial PCT cases. However, possible disease-related UROD mutations were identified in 24% of the examined patients, indicating that genetic analysis of PCT patients may improve differentiation between familial and sporadic PCT cases. 相似文献
999.
1000.
R J Kanas J L Jensen G W DeBoom 《Journal of the American Dental Association (1939)》1986,113(3):441-442
The oral signs and symptoms of acute leukemia include gingival hypertrophy, gingival hemorrhage, petechiae and ecchymoses, mucosal ulceration, paresthesia, tooth pain, and oral infections. This case was unusual in that the diagnosis of acute leukemia was made only after a biopsy specimen of tissue protruding from the socket of a recently extracted tooth disclosed malignant cells suggestive of leukemia or lymphoma. The diagnosis of epulis granulomatosa should be made only after clinical, radiographic, and microscopic studies have been performed to rule out a malignant process. 相似文献