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   115758篇
  免费   7093篇
  国内免费   827篇
耳鼻咽喉   1271篇
儿科学   3358篇
妇产科学   2694篇
基础医学   15621篇
口腔科学   2893篇
临床医学   9235篇
内科学   25937篇
皮肤病学   2515篇
神经病学   10588篇
特种医学   4147篇
外国民族医学   24篇
外科学   16787篇
综合类   1787篇
一般理论   51篇
预防医学   7093篇
眼科学   2029篇
药学   9073篇
  3篇
中国医学   601篇
肿瘤学   7971篇
  2023年   565篇
  2022年   1306篇
  2021年   2393篇
  2020年   1472篇
  2019年   2192篇
  2018年   2700篇
  2017年   1982篇
  2016年   2055篇
  2015年   2431篇
  2014年   3221篇
  2013年   4595篇
  2012年   6291篇
  2011年   6493篇
  2010年   4054篇
  2009年   3633篇
  2008年   5657篇
  2007年   5855篇
  2006年   5578篇
  2005年   5364篇
  2004年   5482篇
  2003年   5334篇
  2002年   5187篇
  2001年   4150篇
  2000年   4105篇
  1999年   3386篇
  1998年   1284篇
  1997年   1005篇
  1996年   930篇
  1995年   887篇
  1994年   780篇
  1993年   720篇
  1992年   1994篇
  1991年   1965篇
  1990年   1680篇
  1989年   1640篇
  1988年   1500篇
  1987年   1346篇
  1986年   1318篇
  1985年   1167篇
  1984年   860篇
  1983年   797篇
  1982年   489篇
  1981年   414篇
  1979年   647篇
  1978年   465篇
  1977年   415篇
  1975年   484篇
  1974年   527篇
  1973年   499篇
  1972年   457篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
Cationic block copolymers spontaneously assemble via electrostatic interactions with DNA molecules in aqueous solution giving rise to micellar structures that protect the DNA from enzymatic degradation both in vitro and in vivo. In addition, we have previously shown that they are safe, not immunogenic and greatly increased antigen-specific CTL responses following six intramuscular inoculations of a very low dose (1 μg) of the vaccine DNA as compared to naked DNA. Nevertheless, they failed to elicit detectable humoral responses against the antigen. To gain further insight in the potential application of this technology, here we show that a shorter immunization protocol based on two DNA intramuscular inoculations of 1 μg of DNA delivered by these copolymers and a protein boost elicits in mice broad (both humoral and cellular) and long-lasting responses and increases the antigen-specific Th1-type T cell responses and CTLs as compared to priming with naked DNA. These results indicate that cationic block copolymers represent a promising adjuvant and delivery technology for DNA vaccination strategies aimed at combating intracellular pathogens.  相似文献   
72.

Background  

Total hip arthroplasty is a successful surgery, that fails at a rate of approximately 10% at ten years from surgery. Causes for failure are mainly aseptic loosening of one or both components partially due to wear of articular surfaces and partially to design. The present analysis aimed to identify risk factors and quantify their effects on aseptic failure.  相似文献   
73.
A survey was performed on the radiotherapy practice of malignant pleural mesothelioma in The Netherlands and Belgium in 2002. Thirty-eight out of 47 centres (81%) responded. Prophylactic radiotherapy to intervention sites is given by 32/38 (84%) centres, with all centres offering palliative radiation. For both prophylactic and palliative indications, all centres use hypo-fractionated schedules. The present study shows that in the radiotherapy community in The Netherlands and in Belgium, a de facto consensus exists that both prophylactic and symptomatic radiotherapy to intervention sites of malignant pleural mesothelioma are effective and that hypo-fractionated schedules should be used.  相似文献   
74.
75.
Two new T cell subsets may be involved in allergic rhinitis (AR) pathogenesis: Th17 and T regulatory cells, mainly producing IL-17 and TGF-β respectively. Successful Sublingual Immunotherapy (SLIT) induces relevant immunological changes, thus the aim of this study was to evaluate serum IL-17 and TGF-β levels in AR patients treated with SLIT for 2 years. Patients' blood samples were collected before initiating SLIT (baseline), three months after the end of the first pre-seasonal SLIT course, and at the end of the second pre-seasonal course. IL-17 was detectable only in the most severe allergic patients. SLIT significantly induced an increase in serum TGF-β levels. There was moreover a significant relationship between TGF-β and symptom severity and drug use at the end of the study. Therefore, this study provides clinically relevant evidence that two pre-seasonal SLIT courses may significantly affect serum TGF-β levels.  相似文献   
76.
OBJECTIVE: The effects of major lung resections on cardiac function in the medium and long term have not been thoroughly evaluated. We have studied right heart function with serial Doppler echocardiography in patients undergoing lobectomy and pneumonectomy during 4 years of follow-up after surgery. METHODS: Thirty-six patients undergoing lobectomy and 15 receiving pneumonectomy were evaluated with one- and two-dimensional Doppler standard transthoracic echocardiography before surgery and 1 week, 3 months, 6 months, 1 year, and 4 years postoperatively. We have studied the right midventricular diastolic diameter (RVDD), the right ventricle free wall thickness, the tricuspid valve insufficiency (TVI) and regurgitation jet (TRJ), and the pulmonary artery systolic pressure (PASP). RESULTS: None of the patients died within the first postoperative year. After lobectomy there were no significant modifications of any variable at any time. RVDD progressively increased after pneumonectomy (26.5+/-2.2mm preoperatively vs 34.3+/-7.6 at 4 years; p<0.001). Four years after surgery all patients undergoing pneumonectomy had moderate TVI while only 55% of patients receiving lobectomy showed it (low grade in 50% and moderate in 5%). In this group of patients PASP increased from 26.1+/-2.6 mmHg preoperatively to 34.3+/-7.6 mmHg at 4 years (p<0.00001). CONCLUSIONS: Right ventricle modifications are clearly evident after pneumonectomy and even if they do not show a clear clinical impact they should not be neglected.  相似文献   
77.
78.
79.
80.
We studied the effects of dipyridamole and RA-642 on the production of superoxide anions and on oxygen radicals-induced lipid peroxidation in lens tissue homogenates from normal rats and rats given dipyridamole or RA-642 intraperitoneally. Superoxide production was evaluated by phenazine methosulphate (PMS)-induced nitroblue tetrazolium (NBT) reduction and lipid peroxidation by ferrous sulfate and ascorbic acid (FeAs)-induced malondialdehyde (MDA) production. Dipyridamole and RA-642 showed an inhibitory effect on both assays in the experiments with lens tissue homogenates from untreated or treated rats. The extent of inhibition, however, was significantly higher in pyrimidopyrimidinic-treated rats (range of inhibition at different times of incubation was 18% versus 23-57% for dipyridamole and 14% versus 73-80% for RA-642 in the assay of MDA production, and 10% versus 33-37% for dipyridamole and 2.5% versus 11-32% for RA-642 in the assay of NBT reduction). Concentrations of dipyridamole and RA-642 in lens tissue from treated animals could not be determined (less than 0.001 micrograms/mg of tissue). Although both compounds inhibited lipid peroxidation induced by oxygen free radicals, the mechanism of action might include the role of adenosine as a mediator.  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