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   47452篇
  免费   3533篇
  国内免费   1968篇
耳鼻咽喉   168篇
儿科学   838篇
妇产科学   492篇
基础医学   6847篇
口腔科学   507篇
临床医学   3701篇
内科学   13427篇
皮肤病学   638篇
神经病学   3162篇
特种医学   911篇
外国民族医学   2篇
外科学   3710篇
综合类   5200篇
现状与发展   5篇
预防医学   2831篇
眼科学   878篇
药学   6122篇
  7篇
中国医学   1530篇
肿瘤学   1977篇
  2023年   469篇
  2022年   908篇
  2021年   1175篇
  2020年   1163篇
  2019年   1833篇
  2018年   1805篇
  2017年   1620篇
  2016年   1590篇
  2015年   1750篇
  2014年   2856篇
  2013年   3307篇
  2012年   2604篇
  2011年   2895篇
  2010年   2182篇
  2009年   2106篇
  2008年   2097篇
  2007年   2301篇
  2006年   2027篇
  2005年   1776篇
  2004年   1563篇
  2003年   1447篇
  2002年   1221篇
  2001年   1095篇
  2000年   931篇
  1999年   842篇
  1998年   719篇
  1997年   772篇
  1996年   579篇
  1995年   578篇
  1994年   500篇
  1993年   379篇
  1992年   334篇
  1991年   262篇
  1990年   201篇
  1989年   179篇
  1988年   151篇
  1987年   131篇
  1985年   466篇
  1984年   568篇
  1983年   454篇
  1982年   419篇
  1981年   408篇
  1980年   366篇
  1979年   324篇
  1978年   280篇
  1977年   210篇
  1976年   249篇
  1975年   251篇
  1974年   199篇
  1973年   175篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Data on the prevalence of antibody to hepatitis C virus among 278 subjects in an institution for the mentally handicapped were analysed by risk factors. A prevalence of 4% was found, higher than blood donors belonging to the same area (1.4%). No differences in prevalence with regard the length of residence, age, sex, degree of retardation or for presence of HBV markers were observed.  相似文献   
62.
丙型肝炎(HC)86例,经临床观察发现其临床特点是:①潜伏期长短不一,长者120d短者26d,平均40.5±14.5d。②起病缓慢而隐匿。③病状轻,体征不明显,病程长。④肝功能损害程度与症状、体征不一致,往往不能及时诊治。⑤肝功能恢复慢,ALT、AST有持续升高或反复异常。⑥治疗:用治疗肝炎的常用药物仅对改善症状有一定作用,对缩短病程及肝功能恢复无效。  相似文献   
63.
Ca(++)-dependent monoclonal antibody specific to gamma-carboxyglutamic acid (Gla) domain of protein C was produced. It did not cross-react to the other vitamin K-dependent plasma proteins but to protein C of the other species. Using this monoclonal antibody, PC01, rabbit (170 micrograms), rat (60 micrograms) and mouse (40 micrograms) protein Cs were isolated from 100 ml of their plasma by affinity chromatography. All of these protein Cs were two chain form linked by disulfide bond as well as human protein C and activated by thrombin-thrombomodulin complex. Rat and mouse protein Cs showed similar characters to human protein C. On the other hand rabbit protein C had different M(r) of heavy and light chains and showed lower anticoagulant activity compared with human protein C.  相似文献   
64.
黄健  茆林 《疾病控制杂志》2003,7(5):431-432
目的 探讨丙型肝炎患mIL-2R表达水平及其临床意义。方法 用生物素-链酶亲和素法对56例抗-HCV阳性患外周血单个核细胞(PBMC)进行植物血凝素(PHA)诱导前后mIL-2R的的检测。结果 急、慢性丙型肝炎患静息状态mIL-2R表达水平,诱导状态mIL-2R表达水平分别与正常对照相比,差异均有显性。结论 丙型肝炎患体内存在明显的细胞免疫功能紊乱,T细胞活化障碍,并与肝病的慢性化有关。  相似文献   
65.
Interferon therapy is used widely for chronic hepatitis C but only a minority of treated patients achieve a long-lasting sustained response. We have developed, by logistic regression, a mathematical model to estimate the probability of sustained response in an individual patient with chronic hepatitis C when treated with interferon-α (IFN-α). The model, which includes age, sex, disease duration, pretreatment serum γ-glutamyl-transpeptidase, alanine aminotransferase and virus genotype, was developed from a database of 307 patients and validated in a new set of 200 patients. It performed well as goodness-of-fit ( P = 0.71 and P = 0.15 in the development and test sample, respectively) and discrimination (area under receiver operating curve = 0.79 in the development and 0.78 in the test sample, respectively). This model may provide decision support in the treatment of chronic hepatitis C with IFN-α.  相似文献   
66.
Fentanyl and the interleukin-6 response to surgery   总被引:12,自引:0,他引:12  
It has been suggested that large doses of opioids may suppress the interleukin-6 response to surgery. We examined the effects of the supplementation of inhalational anaesthesia with either 3 or 15 μg.kg−1 fentanyl on the circulating interleukin-6, interleukin-8, C-reactive protein, cortisol and glucose concentrations in 16 patients undergoing pelvic surgery. In both groups, surgery evoked the expected glucose, cortisol and interleukin-6 response but no increase in interleukin-8 was detected. There were no significant differences between the two groups. We conclude that the supplementation of inhalational anaesthesia with conventional doses of opioids does not modify the cytokine response to surgery.  相似文献   
67.
In the presence of spiperone to block the 5-HT1A-mediated inhibition of pyramidal cell activity, 5-hydroxytryptamine (serotonin, 5-HT) produces a rapid transient increase in amplitude of the extracellularly recorded population spike from area CA1 of the hippocampus. Intracellular recording techniques in area CA1 of rat hippocampal slices were used to identify the ionic mechanism and to characterize the 5-HT receptor mediating this excitatory response to 5-HT. Most of the experiments were conducted in the presence of spiperone to block the 5HT1A hyperpolarization. Since spiperone also has high affinity for 5-HT2 receptors, any response mediated by 5-HT2 receptors would also be blocked. Bath perfusion of the slice with 5-HT increased the rectification of pyramidal cells in the subthreshold region, increased the resistance, and increased the amplitude of subthreshold excitatory postsynaptic potentials (EPSPs) to initiate spike firing. The 5-HT2,1C-selective agonist DOI mimicked this effect of 5-HT, and the 5-HT2,1C antagonist ketanserin (1 microM) blocked the effect of DOI. There was no change in the amplitude of the slow afterhyperpolarization (sAHP) or the amplitude of evoked inhibitory postsynaptic potentials (IPSPs). The increase in rectification and EPSP amplitude by 5-HT occurred even in the presence of the 5-HT4-selective antagonist BRL 24924 to prevent the decrease in amplitude of the sAHP by 5-HT. We conclude that 5-HT produces a fast excitatory response by increasing subthreshold conductance in CA1 hippocampal pyramidal cells. The identity of the receptor mediating this response was not conclusively identified, but resembled the 5-HT1C receptor.  相似文献   
68.
69.
We compared the effectiveness of Ca2+ entering by Na+/Ca2+ exchange with that of Ca2+ entering by channels produced by membrane depolarization with K+ in inducing catecholamine release from bovine adrenal chromaffin cells. The Ca2+ influx through the Na+/Ca2+ exchanger was promoted by reversing the normal inward gradient of Na+ by preincubating the cells with ouabain to increase the intracellular Na+ and then removing Na+ from the external medium. In this way we were able to increase the cytosolic free Ca2+ concentration ([Ca2+]c) by Na+/Ca2+ exchange to 325 ± 14 nM, which was similar to the rise in [Ca2+]c observed upon depolarization with 35 mM K+ of cells not treated with ouabain. After incubating the cells with ouabain, K+ depolarization raised the [Ca2+]c to 398 ± 31 nM, and the recovery of [Ca2+]c to resting levels was significantly slower. Reversal of the Na+ gradient caused an −6-fold increase in the release of noradrenaline or adrenaline, whereas K+ depolarization induced a 12-fold increase in noradrenaline release but only a 9-fold increase in adrenaline release. The ratio of noradrenaline to adrenaline release was 1.24 ± 0.23 upon reversal of the Na+/Ca2+ exchange, whereas it was 1.83 ± 0.19 for K+ depolarization. Reversal of the Na+/Ca2+ exchange appeared to be as efficient as membrane depolarization in inducing adrenaline release, in that the relation of [Ca2+]c to adrenaline release was the same in both cases. In contrast, we found that for the same average [Ca2+]c, the Ca2+ influx through voltage-gated channels was much more efficient than the Ca2+ entering through the Na+/Ca2+ exchanger in inducing noradrenaline release from chromaffin ceils. This greater effectiveness of membrane depolarization in stimulating noradrenaline release suggests that there is a pool of noradrenaline vesicles which is more accessible to Ca2+ entering through voltage-gated Ca2+ channels than to Ca2+ entering through the Na+/Ca2+ exchanger, whereas the adrenaline vesicles do not distinguish between the source of Ca2+.  相似文献   
70.
The binding of human complement components C3, C5 and C9 to the surface of the infective larvae of the nematode parasites Toxocara canis and Trichinella spiralis, by the alternative pathway, was examined by direct and indirect immunofluorescence on the intact parasites. This showed that although C3 bound to both nematodes, they differed markedly in the binding of C5 and C9; C5 bound only minimally to T. spiralis, and C9 binding to this parasite was barely detectable. In contrast, both early and late components bound to T. canis to a high density, comparable to, or in excess of, the binding of these components to the infective larvae of the trematode Schistosoma mansoni. The lack of binding of the post-C3 components to T. spiralis did not correlate with enhanced binding of the control protein, Factor H.  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