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   5222篇
  免费   335篇
  国内免费   13篇
耳鼻咽喉   35篇
儿科学   232篇
妇产科学   118篇
基础医学   567篇
口腔科学   72篇
临床医学   314篇
内科学   1257篇
皮肤病学   106篇
神经病学   589篇
特种医学   287篇
外科学   848篇
综合类   14篇
一般理论   1篇
预防医学   268篇
眼科学   32篇
药学   397篇
中国医学   11篇
肿瘤学   422篇
  2023年   53篇
  2022年   37篇
  2021年   114篇
  2020年   90篇
  2019年   114篇
  2018年   247篇
  2017年   186篇
  2016年   205篇
  2015年   213篇
  2014年   238篇
  2013年   330篇
  2012年   335篇
  2011年   258篇
  2010年   190篇
  2009年   157篇
  2008年   234篇
  2007年   201篇
  2006年   179篇
  2005年   187篇
  2004年   171篇
  2003年   136篇
  2002年   125篇
  2001年   108篇
  2000年   74篇
  1999年   114篇
  1998年   41篇
  1997年   17篇
  1995年   20篇
  1994年   17篇
  1992年   117篇
  1991年   120篇
  1990年   96篇
  1989年   83篇
  1988年   89篇
  1987年   78篇
  1986年   74篇
  1985年   65篇
  1984年   45篇
  1983年   35篇
  1980年   24篇
  1979年   49篇
  1978年   28篇
  1976年   20篇
  1974年   17篇
  1973年   29篇
  1971年   17篇
  1970年   17篇
  1969年   22篇
  1968年   17篇
  1967年   18篇
排序方式: 共有5570条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
Is interleukin 2 a neuromodulator in the brain?   总被引:5,自引:0,他引:5  
A bidirectional flow of information exists between the CNS and the neuroendocrine and immune systems, representing an important homeostatic mechanism in the body. Lymphokines and other products of immunocompetent cells seem to play a crucial role in this communication and seem to exert powerful effects on neurones in the brain. In this article, Giuseppe Nisticò and Giovambattista De Sarro describe the central effects following interleukin 2 (IL-2) microinfusion into several areas of the rat brain. The locus coeruleus seems to be the main site in the brain through which IL-2 exerts soporific effects. In addition, the possible transducing mechanisms coupling IL-2 receptor stimulation and the electroencephalogram (EEG) spectrum power responses elicited from the locus coeruleus seem to involve stimulation of specific receptors coupled to adenylate cyclase through a Gi protein.  相似文献   
6.
7.
Gardner's syndrome (GS) is a hereditary disorder inherited as autosomal dominant with complete penetrance and variable expression. GS is a variant of familial adenomatous polyposis characterized by extracolonic manifestations including osteomas, dental anomalies, and epidermoid cysts. The association between GS and endocrine abnormalities has been well documented but a direct pituitary involvement has never been reported. We present a case of oral and maxillofacial manifestations in an adult patient affected by GS associated with growth hormone deficiency, a hitherto unreported association. The possible pathogenic mechanisms are discussed.  相似文献   
8.
ReProComet: a new in vitro method to assess DNA damage in mammalian sperm.   总被引:1,自引:0,他引:1  
The increasing request of chemical safety assessment demands for the validation of alternative methods to reduce the resort to animal experimentation. Methods that evaluate reproductive toxicity are among those requiring the largest use of animals. Presently, no validated in vitro alternative exists for the assessment of reproductive toxicity. Mammalian sperm are sensitive targets of DNA-reactive chemicals, which form premutagenic adducts. Here, we propose a new method based on comet assay to detect DNA damage induced by potential germ cell mutagens in bull sperm available from assisted reproduction practices. In somatic cells, chemical-induced adducts can be revealed by comet assay that detects DNA breaks produced during adduct repair. Mature sperm, however, are devoid of repair enzymes, and adducts are processed only after fertilization. For this reason, comet assay is not sensitive to detect DNA lesions induced in sperm by most chemicals. To overcome such limitation, we developed a modified comet assay based on the addition of a protein extract from HeLa cells to agarose-embedded sperm on microscopic slides. To test the method, sperm were treated in vitro with methyl methanesulfonate (MMS) or melphalan (MLP) and comet assay was conducted both with and without protein supplementation. No effect of MMS or MLP was detected without protein supplementation; on the contrary, a clear-cut dose-dependent effect was measured after addition of the cell extract. These results represent a proof of concept of a novel in vitro mutagenicity test on sperm that could offer a promising approach to complement previously validated in vivo germ cell genotoxicity assays.  相似文献   
9.
Several neurodegenerative diseases, including motor neuron disease (MND), are characterized by formation of abnormal cytoskeleton-derived inclusions which contain ubiquitin (Ubq). We have studied the distribution of Ubq in 26 cases of MND with light and electron microscopic immunocytochemistry. Ubiquitin-positive inclusions were found in neurons of anterior horns in most cases of amyotrophic lateral sclerosis (ALS) but were not present in other forms of MND. Ubiquitin immunoreactivity was observed in 10-15 nm intraneuronal filaments, which were not stained by antibodies to neurofilaments, and on dense bodies of dystrophic neurites throughout the neuropil of anterior horns and pyramidal tracts. Data analysis showed a trend toward lower percentage of Ubq-positive neurons in cases with longer duration of illness or lower number of neurons. A high percentage of Ubq-positive inclusions occurred in cases with an aggressive clinical course, suggesting that ubiquitination takes place at early stages of the disease.  相似文献   
10.
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