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   13007篇
  免费   907篇
  国内免费   69篇
耳鼻咽喉   76篇
儿科学   259篇
妇产科学   185篇
基础医学   1893篇
口腔科学   109篇
临床医学   1797篇
内科学   3221篇
皮肤病学   253篇
神经病学   1157篇
特种医学   582篇
外国民族医学   3篇
外科学   1938篇
综合类   36篇
一般理论   6篇
预防医学   578篇
眼科学   197篇
药学   860篇
中国医学   22篇
肿瘤学   811篇
  2023年   86篇
  2022年   134篇
  2021年   399篇
  2020年   209篇
  2019年   323篇
  2018年   388篇
  2017年   272篇
  2016年   282篇
  2015年   359篇
  2014年   503篇
  2013年   631篇
  2012年   1021篇
  2011年   1107篇
  2010年   553篇
  2009年   534篇
  2008年   822篇
  2007年   836篇
  2006年   803篇
  2005年   773篇
  2004年   706篇
  2003年   667篇
  2002年   635篇
  2001年   178篇
  2000年   170篇
  1999年   152篇
  1998年   132篇
  1997年   111篇
  1996年   85篇
  1995年   57篇
  1994年   51篇
  1993年   57篇
  1992年   97篇
  1991年   84篇
  1990年   68篇
  1989年   75篇
  1988年   76篇
  1987年   64篇
  1986年   63篇
  1985年   55篇
  1984年   38篇
  1983年   37篇
  1982年   25篇
  1981年   21篇
  1980年   24篇
  1979年   19篇
  1978年   19篇
  1976年   17篇
  1975年   28篇
  1973年   18篇
  1967年   20篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
A total of 431 consecutive patients from the Midi Pyrenees area with acute hepatitis with unknown etiology in 2001-2002 were tested for the presence of immunoglobulin G-class (IgG) anti-hepatitis E virus (HEV) antibodies. Forty-six (10.7%) had anti-HEV IgG, and the results were questionable for a further 17 (3.9%). Real time PCR based on TaqMan detection was used to identify HEV genome fragments in the serum of patients with positive or questionable anti-HEV serology. HEV RNA was found in 25.4% of cases. All amplification products were sequenced and analyzed. Phylogenetic analysis revealed that all the strains were genotype 3. In conclusion, virological and epidemiological data indicate that genotype 3 viruses are circulating in the south west part of France (Midi-Pyrenees) in patients with acute hepatitis and who have not visited recently areas in which HEV is endemic.  相似文献   
42.
43.
The calf muscle metabolism of 7 patients with stable chronic respiratory failure (PaO2 below 65 Torr) was studied using 31P NMR spectroscopy. NMR spectra were acquired at rest, during the course of 360 pedal movements at 20, 35 and 50% of the maximal voluntary contraction (MVC) and during recovery. Eight normal aged-matched subjects served as a control group. In resting muscle, no significant differences were observed between both groups as regards intracellular pH, inorganic phosphate/phosphocreatine (Pi/PCr) and beta-ATP/PCr + Pi + phosphomonoester (PME) ratios. Although effective power outputs were similar for both groups at each work level, patients exhibited a higher Pi/PCr ratio than healthy controls (3.19 +/- 1.01 vs 0.49 +/- 0.05 at 50% MVC; p less than 0.01) and a lower pHi (6.65 +/- 0.11 vs 7.06 +/- 0.02 at 50% MVC; p less than 0.01). Moreover, PCr resynthesis during recovery was slower in patients than in control subjects (t1/2 PCr = 1.26 +/- 0.30 vs 0.47 +/- 0.05 min; p = 0.01). These results suggest impairment of aerobic capacity in a non-ventilatory working muscle, probably due to hypoxemia in patients with chronic respiratory failure.  相似文献   
44.
An inhibitor of the cytotoxic functions (ICF) mediated by human immunodeficiency virus (HIV)- or HLA-specific cytotoxic T lymphocytes, natural killer and lymphokine-activated killer (LAK) cells is secreted by CD8+CD57? T lymphocytes, a subset expanded during infection with HIV and after bone marrow transplantation. We previously showed an apparent molecular mass of 20–30 kDa for this soluble glycosylated concanavalin A-binding inhibitor which is distinct from known cytokines. Here, we report a characterization of the mechanism of action of this CD8+CD57+ ICF. We show that the ICF-induced inhibition of LAK cell cytolytic activity is transient, with a spontaneous recovery of cytolytic potential after 18 h. When testing interactions of ICF with a large set of cytokines we found that the ICF-mediated inhibition of cytotoxic functions is antagonized by two cytokines: recombinant interleukin (rIL)-4 and recombinant interferon (rIFN)-γ. Finally, we show that ICF acts at the level of cytolytic effector cells, where it induces a significant increase of cyclic AMP (cAMP) level. In contrast, no modification of either cell surface antigen expression or of target/effector cell conjugate formation could be evidenced. Addition of rIL-4 and rIFN-γ reverses such an increase of cAMP levels and in parallel restores the cytolytic activity. Altogether, these data demonstrate that the glycoprotein ICF produced by CD8+CD57+ cells (1) inhibits cell-mediated cytotoxicity by sensitizing cytolytic effector cells to the cAMP pathway, and (2) is part of a cytokine network controlling cell-mediated cytotoxic functions.  相似文献   
45.
Three cases of nephroblastoma presented "egg-shell" peripheral calcifications of pseudocystic appearance of radiology. These peripheral lesions are compared with the more commonly reported central calcifications. Their pathology is unknown and they lack prognostic significance of any importance. As for all nephroblastomas the diagnosis is based on straight abdomen images, intravenous urography, ultrasound and computed tomography. Differential diagnosis is basically from renal adenocarcinoma in children, the latter often exhibiting similar calcifications, the distinction between the two types of tumor depending on age of onset. These calcified lesions are non-specific findings and various diagnoses are discussed.  相似文献   
46.
Prevention Science - Screening is an essential prevention practice for a number of health conditions. However, screening coverage remains generally low. Studies that investigate determinants of...  相似文献   
47.
48.
49.
50.
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