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   40363篇
  免费   4275篇
  国内免费   2707篇
耳鼻咽喉   294篇
儿科学   515篇
妇产科学   456篇
基础医学   4726篇
口腔科学   839篇
临床医学   5230篇
内科学   5909篇
皮肤病学   429篇
神经病学   1849篇
特种医学   1458篇
外国民族医学   17篇
外科学   4295篇
综合类   6876篇
现状与发展   12篇
一般理论   15篇
预防医学   2964篇
眼科学   1331篇
药学   3962篇
  57篇
中国医学   2389篇
肿瘤学   3722篇
  2024年   165篇
  2023年   763篇
  2022年   1803篇
  2021年   2344篇
  2020年   1721篇
  2019年   1492篇
  2018年   1516篇
  2017年   1371篇
  2016年   1282篇
  2015年   1918篇
  2014年   2398篇
  2013年   2229篇
  2012年   3109篇
  2011年   3398篇
  2010年   2173篇
  2009年   1828篇
  2008年   2204篇
  2007年   2134篇
  2006年   2171篇
  2005年   1838篇
  2004年   1336篇
  2003年   1148篇
  2002年   961篇
  2001年   833篇
  2000年   787篇
  1999年   817篇
  1998年   521篇
  1997年   478篇
  1996年   368篇
  1995年   321篇
  1994年   323篇
  1993年   185篇
  1992年   236篇
  1991年   188篇
  1990年   152篇
  1989年   195篇
  1988年   133篇
  1987年   137篇
  1986年   62篇
  1985年   71篇
  1984年   46篇
  1983年   30篇
  1982年   26篇
  1981年   26篇
  1980年   19篇
  1979年   26篇
  1978年   11篇
  1977年   5篇
  1975年   9篇
  1974年   10篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
胆总管的矢状断层解剖研究   总被引:1,自引:0,他引:1  
刘树伟  王凡 《解剖学杂志》1993,16(5):391-394
在30套成人腹部连续矢状断层标本上,胆总管与下腔静脉主要出现于R2-R3断层;胆总管胰腺段与胰头的关系有部分包埋,完全包埋及胰腺后型;十二指肠大乳头集中出现于R3断层;胆总管的行程有4种形式。文内还探讨了矢状断层里胆总管各段的毗邻及识别标志。  相似文献   
42.
本文通过28例正常人及28例癌症病患者的头发的分析,得出癌症病患者的头发区别于正常人的头发的特征是:癌症病患者的头发中含有微量元素As、Ni、Mn。  相似文献   
43.
肺动脉高压是多种因素导致的内皮功能受损所致,病理机制的研究进展为治疗开辟了新思路,提出了如钾离子通道开放剂、内皮素受体拮抗剂、蛋白激酶C抑制剂、PDE-5抑制剂和血栓素抑制等治疗方法.  相似文献   
44.
45.
Thickening of the tubular basement membrane (TBM) occurs in diabetic nephropathy, but the effects of high glucose on the functional aspects of proximal tubular epithelial cells are not clearly understood. In the present study, we examined the effects of elevated glucose concentrations on (a) integrin expression by human proximal tubular epithelial cells (HK-2) and integrin-mediated interactions with type IV collagen (colIV) and laminin, major components of TBM; (b) the expression of matrixins/matrix metalloproteinases (MMPs), which is regulated by integrins; and (c) the expression of tissue inhibitors of metalloproteinases (TIMPs). HK-2 cells cultured in 25 mM glucose underwent a reduction of the expression of alpha3, beta1, alpha(v)beta3, and alpha5 integrin subunits, with a concomitant increase of the alpha2 subunit, compared with cells grown in 5 mM glucose. Adhesion experiments demonstrated that high glucose led to increased cell adhesion on either colIV or laminin. Experiments of competition of adhesion using anti-integrin antibodies indicated that HK-2 cells in 5 mM glucose used mainly alpha(v)beta3 and alpha5beta1 integrins to adhere to colIV, whereas in 25 mM glucose they additionally used alpha2beta1. In the case of laminin, a beta1-mediated adhesion was observed when HK-2 cells were in 5 mM glucose, whereas in 25 mM glucose, alpha2beta1 and alpha(v)beta3 were also involved. Elevated glucose concentrations resulted in decreased expression of MMP-9 and MMP-2, whereas an increase in TIMP-1 and a decrease in TIMP-2 expression were observed. We also examined which integrins mediated the expression and secretion of matrixins MMP-2 and MMP-9. Ligation of alpha3beta1 with mAbs resulted in induction of MMP-2 expression and secretion, whereas antibody ligation of alpha(v)beta3 led to down-regulation of MMP-9. The above data implicate integrins of proximal tubular epithelial cells in the regulation of MMPs and in the development of TBM thickening in diabetic nephropathy.  相似文献   
46.
Human chromosome 2 was formed by the head-to-head fusion of two ancestral chromosomes that remained separate in other primates. Sequences that once resided near the ends of the ancestral chromosomes are now interstitially located in 2q13-2q14.1. Portions of these sequences had duplicated to other locations prior to the fusion. Here we present analyses of the genomic structure and evolutionary history of >600 kb surrounding the fusion site and closely related sequences on other human chromosomes. Sequence blocks that closely flank the inverted arrays of degenerate telomere repeats marking the fusion site are duplicated at many, primarily subtelomeric, locations. In addition, large portions of a 168-kb centromere-proximal block are duplicated at 9pter, 9p11.2, and 9q13, with 98%-99% average sequence identity. A 67-kb block on the distal side of the fusion site is highly homologous to sequences at 22qter. A third ~100-kb segment is 96% identical to a region in 2q11.2. By integrating data on the extent and similarity of these paralogous blocks, including the presence of phylogenetically informative repetitive elements, with observations of their chromosomal distribution in nonhuman primates, we infer the order of the duplications that led to their current arrangement. Several of these duplicated blocks may be associated with breakpoints of inversions that occurred during primate evolution and of recurrent chromosome rearrangements in humans.  相似文献   
47.
应用透射电镜和图象分析方法,对电针后大鼠中缝大核突触前终扣内突触囊泡的数量以及突触前终扣内容物的量的变化进行了研究。结果表明:电针后,中缝大核突触前终扣内圆形清亮囊泡和颗粒囊泡的数量明显减少,突触囊泡聚集并向突触活性带集中。图象分析结果:电针后,突触前终扣内容物的量较对照组明显减少,而且内容物分布不均匀并在突触膜附近集中。本实验为针刺镇痛的理论研究提供了形态学依据。  相似文献   
48.
HLA-A2 subtypes (A*0201 - *0212) were determined by oligotyping in HLA-A2 positive samples from four populations (Han Chinese, Dai Chinese, Caucasoids from Germany and Turkish individuals from Kayseri)(see table).

Two different findings can be concluded from this study: 1) Significant HLA-A*02 allelic variations found in four populations. A*0207 is the predominant A*02 allele in the Dai population and absent in the German Caucasian and the Turkish population. In contrast, A*0201 is the most prevalent allele in the Caucasian, Turkish and Han Chinese group. We also found a high proportion of A*0206 and A*0207 in Han Chinese. 2) A strong association has been found between A*0207 and HLA-B46 and DR9 in the Dai minority population. This haplotype is also found in Han Chinese. Three DNA samples from Turkish and one from the Dai population are presently being sequenced because the reaction pattern was out of the expected (Supported by SFB 217)  相似文献   

49.
We investigated the effects of the purified catalytic subunit (C subunit) of the cAMP-dependent protein kinase (A-kinase) on the cardiac Na+ channel currents. Single Na+ channel currents in guinea-pig ventricular myocytes were recorded using the patch clamp technique of the inside-out configuration. Application of C subunit decreased the peak average current and slowed the current decay, effects which were caused by decrease in the open probability of Na+ channels and increase in the first latency, whereas the unitary current amplitude and mean open times were not affected. We conclude that the cardiac Na+ channel is directly modulated by phosphorylation process through A-kinase.  相似文献   
50.
Helicobacter pylori (HP) infection induces expression of IL-8 and IL-10 in benign gastric epithelium. This study compared the expression of cytokines in CD4+ and CD8+ lymphocyte subsets of peripheral blood lymphocytes (PBL), benign mucosal lymphocytes (ML), and tumor infiltrative lymphocytes (TIL) as well as in the benign and malignant epithelial cells of the same patient, with respect to the presence of HP infection, lymph node metastases, and tumor histologic type. The mRNA of the cytokines was measured by a semiquantitative RT-PCR method. The levels were ranked and compared using the Wilcoxon sign-ranked test. Compared with CD8+ ML, the CD8+ TIL expresses higher levels of IL-6 and IL-8 but lower level of IL-4 in patients with lymph node metastases. In patients with HP infection, expression of IL-8 and IL-10 was higher in the gastric carcinoma cells than in the benign epithelial cells while expression of IL-6 and IL-8 were higher in CD8+ TIL than CD8+ ML. Overexpression of IL-8 in HP associated gastric carcinomas suggested that they might have arisen from HP-infected epithelial cells.  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