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   157744篇
  免费   31495篇
  国内免费   2445篇
耳鼻咽喉   5268篇
儿科学   5477篇
妇产科学   2551篇
基础医学   3992篇
口腔科学   1664篇
临床医学   27101篇
内科学   48909篇
皮肤病学   7655篇
神经病学   15247篇
特种医学   6581篇
外科学   42162篇
综合类   279篇
现状与发展   72篇
预防医学   7145篇
眼科学   3387篇
药学   1401篇
中国医学   29篇
肿瘤学   12764篇
  2024年   691篇
  2023年   4818篇
  2022年   1256篇
  2021年   3200篇
  2020年   6076篇
  2019年   2228篇
  2018年   7490篇
  2017年   7425篇
  2016年   8497篇
  2015年   8539篇
  2014年   15603篇
  2013年   15736篇
  2012年   5706篇
  2011年   5805篇
  2010年   10487篇
  2009年   14366篇
  2008年   6026篇
  2007年   4301篇
  2006年   6759篇
  2005年   4053篇
  2004年   3290篇
  2003年   2309篇
  2002年   2348篇
  2001年   4075篇
  2000年   3337篇
  1999年   3487篇
  1998年   3714篇
  1997年   3549篇
  1996年   3434篇
  1995年   3279篇
  1994年   2008篇
  1993年   1618篇
  1992年   1580篇
  1991年   1573篇
  1990年   1249篇
  1989年   1372篇
  1988年   1197篇
  1987年   985篇
  1986年   1001篇
  1985年   835篇
  1984年   640篇
  1983年   583篇
  1982年   557篇
  1981年   436篇
  1980年   381篇
  1979年   387篇
  1978年   384篇
  1977年   441篇
  1975年   315篇
  1972年   341篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
981.
Hepatitis B (HB) vaccine is very promising for the prevention of HB infection. There exist, however, some non-responders to current vaccination trials. In this study, taurine, parotin and lithium were selected as adjuvants which can be administered orally. The mechanisms of these three materials as adjuvants and their effects on HB vaccine were investigated in mice. For instance, taurine induced polyclonal antibody production and exhibited adjuvant activity. Although taurine did not have any activity on the proliferation of thymocytes nor stimulate IL-2 production, taurine did induce IL-1 production by macrophages. It was considered that taurine-induced IL-1 would play an essential role in the proliferation and differentiation of B cells. Parotin also induced polyclonal antibody production and exhibited adjuvant activity. These effects of parotin were not affected even if macrophages or T cells were depleted, and parotin itself had an IL-1-like activity. Therefore, it was considered that parotin acted directly on B cells by its IL-1-like activity and mitogenic activity, resulting in the proliferation and differentiation of B cells. Lithium induced neither polyclonal antibody production, nor IL-1 or IL-2 production. However, when given with an antigen, lithium activated the humoral immune system, resulting in the augmentation of antibody production. Oral administration of taurine, parotin and lithium were capable of restoring antibody responses to HB surface antigen (HBsAg) in HBsAg-nonresponder mice. Furthermore, taurine, parotin and lithium enhanced the adjuvant effects of aluminium contained in the present HB vaccine. These observations indicate that use of these oral adjuvants may open new perspectives in the field of human HB vaccination.  相似文献   
982.
Nodular aggregates of histiocytes and eosinophils, described as "histioeosinophilic granulomas," were found in the capsules and septa of 29 of 63 nonneoplastic thymuses (45 per cent) removed from patients with myasthenia gravis. The configurations and cytologic appearances of the lesions resembled those of eosinophilic granuloma, but a combination of morphologic, immunohistochemical, and ultrastructural studies failed to demonstrate a Langerhans' cell component in these lesions. This heretofore unrecorded thymic lesion might represent the thymic counterpart of a pleural process that has been described as "reactive eosinophilic pleuritis" in patients with spontaneous pneumothorax and was probably induced by diagnostic pneumomediastinum performed prior to thymectomy. It is of interest, however, that the presence of these granulomas was correlated with an increased probability of remission of myasthenic symptoms following thymectomy.  相似文献   
983.
984.
Gastrointestinal somatostatinomas are rare. Only 56 cases with duodenal origin have been reported in the literature. The long-term course of an untreated tumor like this is unknown. We report a case of a male patient who lived 30 yr with an untreated metastatic duodenal somatostatinoma. This case suggests that a duodenal somatostatinoma may be of low malignant potential and that expectancy when treating this tumor might be indicated.  相似文献   
985.
986.
987.
A series of T-cell-specific monoclonal antibodies (Leu-1, Leu-2a, and Leu-3a) and B-cell-specific monoclonal antibody (HLB-1) were used to detect the localization and intensity of infiltration of lymphocyte subpopulations and T-cell subsets in frozen sections of 17 patients with the oral cancer. The vast majority of the lymphocyte infiltrates in the oral cancer tissues were reactive with Leu-1. In contrast, B cells were detectable with HLB-1 in only 2 of 17 cases. Leu-2a-positive cells were dominant in four cases, whereas Leu-3a positive cells were dominant in only three cases. In seven cases, both cells infiltrated to the same degree. Leu-2a positive cells tended to be dominant in the cases with earlier clinical stages.  相似文献   
988.
This study examined the effects of acute high-intensity and moderate-intensity exercise on Ca2+-stimulated adenosine triphosphatase (ATPase) activity and the Ca2+ and ATP dependence of Ca2+-ATPase of the sarcoplasmic reticulum (SR) in the soleus muscle. The rats were run on 10% grade at 50 m min(-1) or 25 m min(-1) until fatigued (avg. time to exhaustion 2.8 and 87.7 min, respectively). The catalytic activities of SR Ca2+-ATPase were significantly depressed immediately after both types of exercise. Kinetic analyses demonstrated that the Ca2+ affinity of Ca2+-ATPase was elevated by both types of exercise adopted in the present investigation whereas the increase in the ATP affinity was brought about by only high-intensity exercise. These results suggest that exhaustive exercise may induce in slow-twitch muscle fibre the environmental changes, which adversely affect SR Ca2+-ATPase activity and can overcome the positive influence arising from the increase in the Ca2+ and/or ATP affinities of SR Ca2+-ATPase.  相似文献   
989.
990.
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