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   24356篇
  免费   1327篇
  国内免费   316篇
耳鼻咽喉   472篇
儿科学   343篇
妇产科学   272篇
基础医学   4330篇
口腔科学   568篇
临床医学   2007篇
内科学   4702篇
皮肤病学   903篇
神经病学   1811篇
特种医学   1543篇
外科学   2957篇
综合类   160篇
现状与发展   1篇
一般理论   5篇
预防医学   1087篇
眼科学   456篇
药学   2107篇
中国医学   286篇
肿瘤学   1989篇
  2023年   149篇
  2022年   512篇
  2021年   819篇
  2020年   405篇
  2019年   570篇
  2018年   652篇
  2017年   530篇
  2016年   730篇
  2015年   1093篇
  2014年   1302篇
  2013年   1447篇
  2012年   2164篇
  2011年   2048篇
  2010年   1174篇
  2009年   1056篇
  2008年   1456篇
  2007年   1367篇
  2006年   1143篇
  2005年   1015篇
  2004年   872篇
  2003年   758篇
  2002年   649篇
  2001年   576篇
  2000年   474篇
  1999年   402篇
  1998年   204篇
  1997年   148篇
  1996年   140篇
  1995年   137篇
  1994年   100篇
  1993年   93篇
  1992年   150篇
  1991年   158篇
  1990年   126篇
  1989年   149篇
  1988年   134篇
  1987年   142篇
  1986年   119篇
  1985年   114篇
  1984年   79篇
  1983年   68篇
  1982年   50篇
  1981年   60篇
  1980年   49篇
  1979年   54篇
  1978年   58篇
  1977年   57篇
  1976年   39篇
  1975年   36篇
  1973年   34篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
A flat depressed early colon cancer (FDEC) is characterized by non-polypoid growth pattern, no association of adenomatous tissues and a tendency of even small lesions toward submucosal invasion and lymph node metastasis. It supports de novo carcinogenesis of colorectal cancer, although most colorectal cancers arise in pre-existing adenoma (adenoma-carcinoma sequence). There have been few reports of small depressed cancers because of the difficulty in colonoscopic detection and the rapid development to ulcerating advanced cancers. We report a case of flat depressed early colon cancer confined to mucosa detected by indigo carmine contrast colonoscopy.  相似文献   
62.
63.
Leukodystrophies are a heterogeneous group of heritable disorders characterized by abnormal brain white matter signal on magnetic resonance imaging (MRI) and primary involvement of the cellular components of myelin. Previous estimates suggest the incidence of leukodystrophies as a whole to be 1 in 7,000 individuals, however the frequency of specific diagnoses relative to others has not been described. Next generation sequencing approaches offer the opportunity to redefine our understanding of the relative frequency of different leukodystrophies. We assessed the relative frequency of all 30 leukodystrophies (associated with 55 genes) in more than 49,000 exomes. We identified a relatively high frequency of disorders previously thought of as very rare, including Aicardi Goutières Syndrome, TUBB4A‐related leukodystrophy, Peroxisomal biogenesis disorders, POLR3‐related Leukodystrophy, Vanishing White Matter, and Pelizaeus‐Merzbacher Disease. Despite the relative frequency of these conditions, carrier‐screening laboratories regularly test only 20 of the 55 leukodystrophy‐related genes, and do not test at all, or test only one or a few, genes for some of the higher frequency disorders. Relative frequency of leukodystrophies previously considered very rare suggests these disorders may benefit from expanded carrier screening.  相似文献   
64.
65.
To isolate novel genes regulating neural induction, we used a DNA microarray approach. As neural induction is thought to occur by means of the inhibition of bone morphogenetic protein (BMP) signaling, BMP signaling was inhibited in ectodermal cells by overexpression of a dominant-negative receptor. RNAs were isolated from control animal cap explants and from dominant-negative BMP receptor expressing animal caps and subjected to a microarray experiment using newly generated high-density Xenopus DNA microarray chips representing over 17,000 unigenes. We have identified 77 genes that are induced in animal caps after inhibition of BMP signaling, and all of these genes were subjected to whole-mount in situ hybridization analysis. Thirty-two genes showed specific expression in neural tissues. Of the 32, 14 genes have never been linked to neural induction. Two genes that are highly induced by BMP inhibition are inhibitors of Wnt signaling, suggesting that a key step in neural induction is to produce Wnt antagonists to promote anterior neural plate development. Our current analysis also proves that a microarray approach is useful in identifying novel candidate factors involved in neural induction and patterning.  相似文献   
66.
This report describes an 11 month old female baby with features of pentasomy X. A molecular and cytogenetic evaluation revealed that her karyotype was 49,XXXXX and her extra X chromosomes were of maternal origin. She has muscular hypotonia, mental retardation, a cleft palate, mild hydrocephalus as a result of dilatation of both lateral ventricles, hyperextensible elbow joints, proximal radioulnar synostosis, clinodactyly of the fifth finger, valgus of the feet, and small hands and feet. In addition, she has a persistent pupillary membrane and congenital chorioretinal atrophy. The pathogenesis of pentasomy X is not clear at present, but it is thought to be caused by successive maternal non-dysjunctions.  相似文献   
67.
68.
To determine the content of thyroglobulin in oxyphilic cells of the thyroid, which have been considered as non-thyroglobulin producing cells, the degree of stainability of the various oxyphilic cells for thyroglobulin was compared with that of non-oxyphilic follicular cells in either same or different lesion. A total of 13 oxyphilic lesions, including three follicular adenomas containing oxyphilic cell nodules, four pure oxyphilic cell adenomas, and six Hashimoto's thyroiditis were compared with 16 of non-oxyphilic lesions such as, seven follicular adenomas, four chronic lymphocytic thyroiditis, and five Graves' disease. Many oxyphilic cells stained positively for thyroglobulin regardless of their morphologic variation, but less intensely than the usual follicular cells in follicular adenomas, chronic lymphocytic thyroiditis, and Graves' disease. The stainability of oxyphilic cells for thyroglogulin did not show any significant correlation with morphologic features, whereas in follicular adenomas, the non-oxyphilic follicular cells forming microfollicles stained less strongly for thyroglobulin than the same cells lining large mature follicles in a reproducible way. With above findings, we concluded that oxyphilic cells maintain the functional activity in terms of thyroglobulin synthesis, although the content of the thyroglobulin is less than that of non-oxyphilic colloid forming follicular cells.  相似文献   
69.
70.
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