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   7976篇
  免费   662篇
  国内免费   78篇
耳鼻咽喉   70篇
儿科学   363篇
妇产科学   189篇
基础医学   995篇
口腔科学   155篇
临床医学   721篇
内科学   1882篇
皮肤病学   82篇
神经病学   914篇
特种医学   447篇
外科学   819篇
综合类   177篇
一般理论   2篇
预防医学   864篇
眼科学   129篇
药学   360篇
肿瘤学   547篇
  2021年   81篇
  2019年   60篇
  2018年   98篇
  2017年   84篇
  2016年   76篇
  2015年   98篇
  2014年   159篇
  2013年   215篇
  2012年   298篇
  2011年   289篇
  2010年   199篇
  2009年   208篇
  2008年   316篇
  2007年   337篇
  2006年   305篇
  2005年   308篇
  2004年   271篇
  2003年   333篇
  2002年   285篇
  2001年   281篇
  2000年   278篇
  1999年   257篇
  1998年   135篇
  1997年   144篇
  1996年   122篇
  1995年   122篇
  1994年   92篇
  1993年   103篇
  1992年   229篇
  1991年   233篇
  1990年   215篇
  1989年   210篇
  1988年   190篇
  1987年   194篇
  1986年   148篇
  1985年   180篇
  1984年   120篇
  1983年   89篇
  1982年   77篇
  1981年   81篇
  1980年   57篇
  1979年   130篇
  1978年   93篇
  1977年   66篇
  1976年   70篇
  1975年   67篇
  1974年   72篇
  1973年   58篇
  1972年   71篇
  1966年   52篇
排序方式: 共有8716条查询结果,搜索用时 15 毫秒
71.
72.
Clinical signs of botulism were observed in a group of eight cats, four of which died, after being fed pelican carrion. Clostridium botulinum type C was isolated from one cat. The microorganism and its toxin were found in the pelican. This is apparently the first report of natural botulism in cats.  相似文献   
73.
We present a girl with mild manifestations of the Brachmann-de Lange syndrome (BDLS) with gradual change of the phenotype. Her findings support the hypothosis of variability of the phenotypic spectrum of the disorder.  相似文献   
74.
Differential expression of adhesion molecules and chemokine receptors has been useful for identification of peripheral blood memory lymphocyte subsets with distinct tissue and microenvironmental tropisms. Expression of CCR4 by circulating memory CD4(+) lymphocytes is associated with cutaneous and other systemic populations while expression of CCR9 is associated with a small intestine-homing subset. CCR5 and CXCR3 are also expressed by discrete memory CD4(+) populations in blood, as well as by tissue-infiltrating lymphocytes from a number of sites. To characterize the similarities and differences among tissue-infiltrating lymphocytes, and to shed light on the specialization of lymphocyte subsets that mediate inflammation and immune surveillance in particular tissues, we have examined the expression of CCR4, CXCR3, and CCR5 on CD4(+) lymphocytes directly isolated from a wide variety of normal and inflamed tissues. Extra-lymphoid tissues contained only memory lymphocytes, many of which were activated (CD69(+)). As predicted by classical studies, skin lymphocytes were enriched in CLA expression whereas intestinal lymphocytes were enriched in alpha(4)beta(7) expression. CCR4 was expressed at high levels by skin-infiltrating lymphocytes, at lower levels by lung and synovial fluid lymphocytes, but never by intestinal lymphocytes. Only the high CCR4 levels characteristic of skin lymphocytes were associated with robust chemotactic and adhesive responses to TARC, consistent with a selective role for CCR4 in skin lymphocyte homing. In contrast, CXCR3 and CCR5 were present on the majority of lymphocytes from each non-lymphoid tissue examined, suggesting that these receptors are unlikely to determine tissue specificity, but rather, may play a wider role in tissue inflammation.  相似文献   
75.
During embryonic development, a large number of cells die naturally to shape the new organism. Members of the caspase family of proteases are essential intracellular death effectors. Herein, we generated caspase-2-deficient mice to evaluate the requirement for this enzyme in various paradigms of apoptosis. Excess numbers of germ cells were endowed in ovaries of mutant mice and the oocytes were found to be resistant to cell death following exposure to chemotherapeutic drugs. Apoptosis mediated by granzyme B and perforin was defective in caspase-2-deficient B lymphoblasts. In contrast, cell death of motor neurons during development was accelerated in caspase-2-deficient mice. In addition, caspase-2-deficient sympathetic neurons underwent apoptosis more effectively than wild-type neurons when deprived of NGF. Thus, caspase-2 acts both as a positive and negative cell death effector, depending upon cell lineage and stage of development.  相似文献   
76.
77.
78.
After experimental infection with Mycoplasma pneumoniae, 42% of 67 volunteers developed a threefold or greater rise in antibody in nasal secretions as measured by radioimmunoprecipitation. Development of an antibody increase in sputum was detected more often, i.e., in 73% of the volunteers. Each of the antibody increases involved immunoglobulin (Ig) A. Twelve rises in IgG antibody were detected in the specimens which exhibited a rise in IgA antibody. In almost every instance the rise in IgA antibody exceeded that seen with IgG antibody. Analysis of the response to experimental challenge with M. pneumoniae of volunteers with different levels of preexisting respiratory tract IgA antibody suggested that this secretory antibody was related to host resistance to M. pneumoniae disease. Further, respiratory tract IgA antibody appeared to be more directly related to host resistance than was antibody in serum.  相似文献   
79.
In order to differentiate between malignant pleural mesothelioma and adenocarcinoma of the lung, the glycoconjugate profiles of 6 reactive mesothelial lesions, 23 mesotheliomas (17 epithelial, 1 desmoplastic, 2 biphasic, and 3 fibrous types), and 28 well-differentiated pulmonary adenocarcinomas were evaluated with the use of 8 lectins in addition to anti-carcinoembryonic, anti-keratin and anti-epithelial membrane antigen. Formalin-fixed, paraffin-embedded tissues were stained with the avidin-biotin peroxidase complex method. Reactions of wheat germ (WGA) and peanut (PNA) agglutinin with neuraminidase treatment lectins were positive in 5 of 6 (83%) and 3 of 6 (50%) cases, respectively, in reactive mesothelial lesions. Thirteen of 23 (57%) malignant mesotheliomas of the pleura showed a positive reaction for WGA and PNA with neuraminidase treatment; other lectins were low-positive, below 9%. In contrast, pulmonary adenocarcinomas showed positive reactions in 27 of 28 cases (96%) for PNA, 26 of 28 (93%) for Ricinus communis (RCA-I), 25 of 28 (89%) for WGA, and 22 of 28 (79%) for succinylated WGA (SucWGA). The findings suggest that malignant pleural mesothelioma and pulmonary adenocarcinoma have consistent and distinct glycoconjugate profiles, and that stains for RCA-I and SucWGA may be useful for differential diagnosis.  相似文献   
80.
The development of a microtiter solid-phase radioimmunoassay for the detection of Vibrio cholerae enterotoxin and heat-labile Escherichia coli enterotoxin is described. The test is based on the immunological similarity between V. cholerae toxin and E. coli heat-labile toxin. The assay is easy to perform, quantitative, and at least as sensitive and specific as the Y-1 adrenal cell system.  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