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   1616篇
  免费   224篇
  国内免费   19篇
耳鼻咽喉   28篇
儿科学   74篇
妇产科学   20篇
基础医学   136篇
口腔科学   51篇
临床医学   238篇
内科学   342篇
皮肤病学   118篇
神经病学   61篇
特种医学   141篇
外科学   214篇
综合类   123篇
现状与发展   30篇
一般理论   4篇
预防医学   99篇
眼科学   20篇
药学   61篇
中国医学   4篇
肿瘤学   95篇
  2024年   18篇
  2023年   181篇
  2022年   17篇
  2021年   27篇
  2020年   62篇
  2019年   32篇
  2018年   64篇
  2017年   48篇
  2016年   49篇
  2015年   66篇
  2014年   92篇
  2013年   68篇
  2012年   44篇
  2011年   48篇
  2010年   87篇
  2009年   97篇
  2008年   46篇
  2007年   63篇
  2006年   39篇
  2005年   29篇
  2004年   23篇
  2003年   39篇
  2002年   29篇
  2001年   26篇
  2000年   33篇
  1999年   42篇
  1998年   36篇
  1997年   53篇
  1996年   45篇
  1995年   39篇
  1994年   35篇
  1993年   37篇
  1992年   12篇
  1991年   13篇
  1990年   15篇
  1989年   38篇
  1988年   25篇
  1987年   19篇
  1986年   8篇
  1985年   17篇
  1984年   6篇
  1983年   4篇
  1982年   9篇
  1981年   11篇
  1980年   12篇
  1978年   5篇
  1976年   13篇
  1975年   11篇
  1974年   5篇
  1973年   5篇
排序方式: 共有1859条查询结果,搜索用时 15 毫秒
71.
72.
73.
Background: Restoration of spontaneous circulation after cardiopulmonary resuscitation in cardiac arrest patients does not always signal a completely successful outcome. Functional deficiencies of the nervous system are found in many survivors of cardiac arrest. Objectives: To study the effects of dopamine-induced elevated blood pressure on the hemodynamics, oxygen metabolism, and cerebral resuscitation in different perfusion conditions in a resuscitated animal model. Methods: There were 18 pigs included in the study. Ventricular fibrillation (VF) was induced with a programmed electrical stimulation device. After 4 min of untreated ventricular fibrillation followed by 9 min of CPR, 12 animals were resuscitated successfully, and were then randomly assigned to either the study group (dopamine group) or the control group (normal perfusion group). All animals in the two groups received normal saline through continuous intravenous guttae for 4 h at a rate of 15 mL/kg/h. In the study group, dopamine was added to raise the animals' blood pressure. Four hours of intensive monitoring was performed for all study animals. Finally, 24-h evaluation of neurological function was conducted in surviving animals in accordance with the standard of the Cerebral Performance Category Score. Results: In animals in the dopamine group, the cardiac output, mean aortic pressure, coronary perfusion pressure, oxygen delivery, and oxygen consumption were higher than those found in the animals in the normal perfusion group (p < 0.05). Oxygen metabolism was remarkably improved in animals in the dopamine group. Furthermore, cerebral perfusion was better in the dopamine group than in the control group and thus, results of the evaluation of nervous system function were better in animals treated with dopamine (p < 0.05). Conclusions: Dopamine improved systemic perfusion, cerebral blood supply, and oxygen metabolism after successful resuscitation from VF in a porcine model. All of these factors have profound effects on the cerebral resuscitation.  相似文献   
74.
75.
Epstein-Barr virus lymphoproliferation after bone marrow transplantation   总被引:16,自引:7,他引:16  
We review 15 cases of secondary B-cell lymphoproliferative disorders that occurred among 2,475 patients who received allogeneic bone marrow transplants (BMTs) at the Fred Hutchinson Cancer Research Center (Seattle) between 1969 and 1987. The histopathologic findings in 14 of the 15 patients spanned a wide spectrum of lymphoproliferative lesions. One patient had features characteristic of angioimmunoblastic lymphadenopathy. Epstein-Barr virus (EBV) genomic sequences were identified by Southern blot analysis in each of the 13 patients evaluated. Ten of the 12 lesions evaluated originated in donor cells. In two patients, who had mixed chimerism after transplantation, the lesions originated in host cells. The combined evidence from immunoglobulin light chain staining and the analysis of immunoglobulin heavy chain gene rearrangement indicated that the lesions in most patients represented polyclonal proliferations that gave rise to clonal subpopulations. The results indicate an overall actuarial incidence of 0.6% for this complication in BMT recipients. Anti-CD3 monoclonal antibody (MoAb) treatment of acute graft-v-host disease (GVHD) and T cell depletion of the donor marrow were statistically significant risk factors, and GVHD appeared to play a contributing role, particularly in the setting of human leukocyte antigen (HLA) disparity. Two patients had no identifiable risk factors. Prophylaxis or treatment with acyclovir had no detectable effect in the patients; all but two died with uncontrolled lymphoproliferation.  相似文献   
76.
Angiotensin II has been implicated in the progression of diabetic retinopathy, which is characterized by altered microvasculature, oxidative stress, and neuronal dysfunction. The signaling induced by angiotensin II can occur not only via receptor-mediated calcium release that causes vascular constriction, but also through a pathway whereby angiotensin II activates NADPH oxidase to elicit the formation of reactive oxygen species (ROS). In the current study, we administered the angiotensin II receptor antagonist candesartan (or vehicle, in untreated animals) in a rat model of type 1 diabetes in which hyperglycemia was induced by injection of streptozotocin (STZ). Eight weeks after the STZ injection, untreated diabetic rats were found to have a significant increase in tissue levels of angiotensin converting enzyme (ACE; p < 0.05) compared to non-diabetic controls, a 33% decrease in retinal blood flow rate (p < 0.001), and a dramatic increase in p22phox (a subunit of the NADPH oxidase). The decrease in retinal blood flow, and the increases in retinal ACE and p22phox in the diabetic rats, were all significantly attenuated (p < 0.05) by the administration of candesartan in drinking water within one week. Neither STZ nor candesartan induced any changes in tissue levels of superoxide dismutase (SOD-1), 4-hydroxynonenal (4-HNE), or nitrotyrosine. We conclude that one additional benefit of candesartan (and other angiotensin II antagonists) may be to normalize retinal blood flow, which may have clinical benefits in diabetic retinopathy.  相似文献   
77.

Introduction

The incidence of symptomatic catheter-related deep vein thrombosis (DVT) in cancer patients remains unclear and there is a lack of reliable data on the risk factors of PICC-related DVT.

Materials and Methods

We performed a retrospective cohort study of consecutive cancer patients who received an ultrasound guided PICC line for the administration of chemotherapy. Univariable and multivariable logistic regression analyses were performed to identify risk factors for symptomatic PICC-related DVT.

Results

In total, 340 cancer patients obtained PICC lines for the administration of chemotherapy. Of these patients, 19 (5.6%; 95% CI: 3.6-8.6) developed symptomatic PICC-related DVT. Factors previously associated with catheter-related DVT, including side of catheter placement, lumen size, tip location, need for repositioning, and number of insertion attempts, were not significant determinants in our analysis. Patients with diabetes were three times more likely to develop PICC-related DVT (OR 3.0, p = 0.039), while the presence of COPD and metastatic cancer also increased the odds (OR 3.3, p = 0.078 and OR 2.3, p = 0.083 respectively). Diabetes remained a significant risk factor after adjustment for effect of metastases and COPD (OR 3.175, p = 0.039). Further, the presence of metastases was a significant predictor (OR 3.34, p = 0.024) in our multivariable model.

Conclusions

Symptomatic PICC-related DVT are frequent in cancer patients receiving chemotherapy. Previously described factors associated with catheter-related thrombosis were not predictive of PICC-related DVT in our study. Diabetes, advanced disease and COPD appear to increase the risk of developing PICC-related DVT in chemotherapy patients.  相似文献   
78.
Fitness levels of middle aged martial art practitioners   总被引:1,自引:0,他引:1       下载免费PDF全文
OBJECTIVES: To quantify and compare fitness levels of middle aged practitioners of soo bahk do (SBD; a Korean martial art similar to karate) with those of sedentary subjects. METHODS: Eighteen volunteers, 14 men and four women (aged 40-60 years), participated. Nine sedentary subjects (mean age 46.7 years) and nine SBD practitioners (mean age 46.8 years) were matched for sex and age. All subjects participated in a one day battery of fitness tests. The following dependent variables were tested: body composition, balance, flexibility, quadriceps strength, grip strength, muscle endurance, and aerobic capacity. RESULTS: All dependent variables were analysed using paired t tests. Body composition (% body fat) for the SBD group was 18.9% v 30.8% for the sedentary group (p = 0.004). The SBD group was able to balance for 61.8 seconds v 26.2 seconds for the sedentary group (p = 0.02). The result for the sit and reach flexibility test was 22.3 cm for the SBD group v 10.4 cm for the sedentary group (p = 0.01). The number of push ups performed in one minute was 47.0 for the SBD group v 18.6 for the sedentary group (p = 0.0003), and the number of sit ups performed was 66.1 for the SBD group and 37.3 for the sedentary group (p = 0.00006). Aerobic capacity was 41.0 ml/kg/min v 31.1 ml/kg/min for the sedentary group (p = 0.04). Quadriceps strength was 99.5% (peak torque/body weight) v 83.0% for the sedentary group (p = 0.02). Only grip strength was not significantly different. CONCLUSIONS: There were significant differences between the groups for most of the physical fitness tests. The SBD practitioners displayed greater aerobic capacity, balance, flexibility, muscle endurance, and strength, and less body fat than the sedentary controls matched for age and sex. SBD can be considered an excellent form of exercise for the promotion of fitness in adults. Health professionals should be aware that there are alternative methods to traditional exercise that can increase the physical fitness and health of the middle aged population.  相似文献   
79.

Background/Objectives

The Trail‐Making Test (TMT), which is commonly used to measure executive function, consists of two components (TMT‐A and TMTB). There is a lack of normative TMT data for Chinese elderly adults. This study aimed to evaluate the validity of the TMT in screening for cognitive impairment.

Design

2,294 Chinese‐speaking adults aged 50 to 85: 1,026 with normal cognition (NC), 462 with mild cognitive impairment (MCI), 108 with Alzheimer's disease (AD), 113 with vascular mild cognitive impairment (VaMCI), 121 with vascular dementia (VaD), 282 with uncertain types of dementia, and 15 with mixed dementia. Receiver operating characteristic curve analysis was performed to test the ability of TMT scores to differentiate between NC and cognitive impairment.

Results

Age, education, and sex were significantly associated with TMT completion time. The TMT‐A exhibited sensitivity of 77.8% and specificity of 92.0% with cut‐off value of 98.5 seconds for discriminating AD from NC. The TMT‐B had sensitivity of 83.3% and specificity of 91.8% with a cut‐off value of 188.5 seconds for discriminating AD from NC. The TMT‐A had sensitivity of 85.7% and specificity of 81.6% for discriminating NC from VaD with a cut‐off value of 77.5 seconds, and the TMT‐s had sensitivity of 81.6% and specificity of 83.9% with a cut‐off value of 147.5 seconds. The TMT had less sensitivity distinguishing MCI from NC.

Conclusion

The Chinese version of the TMT is reliable for detecting AD or VaD but poor at distinguishing MCI from NC.  相似文献   
80.
Fifty-two of 175 (30%) survivors of allogeneic marrow transplantation developed chronic graft-versus-hose diseases (GVHD). Five with limited chronic GVHD had an indolent clinical course with involvement of only the skin and liver. Forty-seven with extensive chronic GVHD had an unfavorable multiorgan disorder that resembled several autoimmune diseases. Thirteen patients with extensive disease (group I) were not treated and only 2 survive with Karnofsky scores >- 70%. Mortality resulted from infections and morbidity from sica syndrome, pulmonary and hepatic insufficiency, scleroderma-like skin disease, and contractures. Another 13 (group II) received a median of 8 mo prednisone and/or a brief course of antithymocyte globulin, and 3 survive without disability. The other 21 (group III) were treated with a combination of prednisone (1.0 mg/kg/q.o.d.) and either cyclophosphamide, procarbazine, or azathioprine (all 1.5 mg/kg/day) for a median of 13 mo. Combination therapy was well tolerated with only modest myelotoxicity. Fifteen in group III had a good and 4 a fair response to treatment while 2 with no response died. Azathioprine and prednisone was the most effective regimen. All therapy has been discontinued in 12 group III patients: GVHD returned in 5 (including 2 who died in spite of retreatment) while 7 remain free of GVHD for a median of 11 (range 6-30) mo observation. Only I group III survivor is disabled and 16 of the original 21 are alive 2-4 yr after transplant with Karnofsky scores of 70%-100%. Thus, combination immmunosuppression appears to favorably affect and, in some cases, premanently arrest the adverse natural course of extensive chronic GVHD.  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