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   21344篇
  免费   1584篇
  国内免费   62篇
耳鼻咽喉   419篇
儿科学   732篇
妇产科学   447篇
基础医学   3095篇
口腔科学   507篇
临床医学   2230篇
内科学   4291篇
皮肤病学   360篇
神经病学   2260篇
特种医学   984篇
外国民族医学   1篇
外科学   2755篇
综合类   272篇
现状与发展   1篇
一般理论   14篇
预防医学   1356篇
眼科学   484篇
药学   1323篇
中国医学   52篇
肿瘤学   1407篇
  2023年   108篇
  2022年   201篇
  2021年   398篇
  2020年   280篇
  2019年   361篇
  2018年   381篇
  2017年   318篇
  2016年   434篇
  2015年   472篇
  2014年   635篇
  2013年   982篇
  2012年   1255篇
  2011年   1318篇
  2010年   803篇
  2009年   669篇
  2008年   1180篇
  2007年   1187篇
  2006年   1124篇
  2005年   1208篇
  2004年   1008篇
  2003年   974篇
  2002年   906篇
  2001年   388篇
  2000年   360篇
  1999年   331篇
  1998年   247篇
  1997年   195篇
  1996年   194篇
  1995年   175篇
  1994年   169篇
  1993年   150篇
  1992年   213篇
  1991年   213篇
  1990年   210篇
  1989年   195篇
  1988年   176篇
  1987年   189篇
  1986年   178篇
  1985年   157篇
  1984年   151篇
  1983年   154篇
  1982年   162篇
  1981年   170篇
  1980年   156篇
  1979年   156篇
  1978年   129篇
  1977年   142篇
  1976年   121篇
  1974年   149篇
  1973年   108篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
91.
Angiogenic factors prepared from rat Walker 256 mammary carcinoma, (TAF) and activated mouse peritoneal macrophages (MAF), were tested for their ability to stimulate vascularization during healing. They were applied to one of a pair of bilaterally symmetrical, autologous, isotopic, full thickness skin grafts in mice. Blood flow to treated and untreated graft pairs was compared by their uptake of injected 86Rb Cl, at 3 and 7 days after grafting. No difference was detected after treatment with either agent. We conclude that while angiogenic factors are important in vascularization during healing, this normally occurs at a near maximal rate and cannot be further enhanced.  相似文献   
92.
OBJECTIVE: To investigate the retraction time, forces, and torques applied to the football helmet during removal of the face mask with different face-mask removal tools. DESIGN AND SETTING: Subjects retracted the face mask of a football helmet mounted to a force platform in a laboratory setting. They removed a standard face mask by cutting or removing (or both) the lateral plastic loop straps using 4 different tools: the Trainer's Angel (TA), FM Extractor (FM), power screwdriver (SD), and Quick Release System (QR) in a counterbalanced fashion. SUBJECTS: Eighteen certified athletic trainers participated in this study. MEASUREMENTS: We started measuring time when the subject picked up the tool and ended when the face mask was in a fully retracted position. Maximum forces and torques were measured from the force platform during the retraction process. RESULTS: The SD and QR retracted the face mask significantly faster than the TA and FM. Forces producing superior-inferior translation were least with the SD. The SD and QR produced less lateral translation and rotation and lateral flexion moment than the TA and FM. The FM produced less torque in the lateral flexion moment than the TA. CONCLUSIONS: Tools that removed the loop straps (SD, QR) were faster and produced less force and torque on the helmet than the tools that cut through the loop straps (TA, FM).  相似文献   
93.
Peripheral Tolerance as a Multi-Step Mechanism   总被引:10,自引:0,他引:10  
  相似文献   
94.
95.
96.
Chronic distal spinal muscular atrophy (Chronic DSMA, MIM (*)607088) is a rare autosomal recessive disorder characterized by a progressive motor weakness and muscular atrophy, predominating in the distal parts of the limbs. A form of Chronic DSMA gene has been previously mapped to chromosome 11q13 in the 10.3 cM interval defined by loci D11S1889 and D11S1321. By linkage analysis in 12 European Chronic DSMA families, we showed that a disease gene maps to chromosome 11q13.3 (Z(max)=6.66 at theta=0.00 at the DSM4 locus) and suggested that this condition is genetically homogeneous. Recombination events allowed us to reduce the genetic interval to a 2.6 cM region, telomeric to the IGHMBP2 gene, excluding this gene as the disease causing gene in Chronic DSMA. Moreover, partial linkage disequilibrium was found between three rare alleles at loci D11S1369, DSM4 and D11S4184 and the mutant chromosome in European patients. Analysis of the markers at these loci strongly suggests that most Chronic DSMA chromosomes are derived from a single ancestor. Refinement of the Chronic DSMA locus will hopefully allow to test candidate genes and lead to identification of the disease-causing mutations.  相似文献   
97.
Liver biopsy material of 22 in the serum HBsAg positive patients was tested with the fluorescent antibody technique for the localization of HBcAg and HBsAg in the liver tissue. Comparative studies were done with the following tissue preparation techniques: Cryostat technique, freeze drying, freeze substitution, cold ethanol paraffin embedding technique (SAINTE MARIE) and isolated liver cells. The investigations revealed the following results: 1. No HB-components could be detected with the cold ethanol paraffin embedding technique and freeze substitution. 2. Using the cryostat technique HBsAg could be demonstrated in 16/22 (cytoplasmatic localization) and HBcAg in 8/22 (nuclear localization). 3. With freeze drying HBsAg and HBcAg could be found in the same cases. The excellent tissue preparation allowed a correct localization of the HB-components to the cell structure. 4. In comparison to cryostat sections in isolated liver cells HBcAg could be demonstrated in 11/16 and HBcAg in 8/8 cases.  相似文献   
98.
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   
99.
Six different group C adenovirus transformed hamster cell lines were employed to produce tumors in hamsters. The sera from these animals were then used to immunoprecipitate [35S]methionine-labeled adenovirus induced tumor antigens from virus infected and transformed cells. Collectively, these sera detect 14 virus induced tumor antigens. Based upon the regions of the adenoviral genome present and transcribed in each of the transformed cell lines, an estimated position of the genomic map location responsible for the induction of each of the tumor antigens or viral early proteins was determined. These sera were also employed to follow the synthesis of the adenovirus proteins during productive infection and in transformed cells. Based upon this analysis the tumor antigens can be divided into two groups, early and delayed early proteins, depending upon the time after infection that a protein was synthesized and detected by immunoprecipitation. A comparison of the Ad2 and Ad5 early proteins produced in virus infected and transformed cells indicated that several proteins have different apparent molecular weights that are serotype specific but independent of the species of host cell employed.  相似文献   
100.
Meningococcal pneumonia   总被引:1,自引:0,他引:1  
  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