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   2688篇
  免费   358篇
  国内免费   20篇
耳鼻咽喉   57篇
儿科学   67篇
妇产科学   45篇
基础医学   340篇
口腔科学   69篇
临床医学   380篇
内科学   519篇
皮肤病学   89篇
神经病学   143篇
特种医学   84篇
外科学   301篇
综合类   29篇
一般理论   4篇
预防医学   451篇
眼科学   168篇
药学   212篇
中国医学   3篇
肿瘤学   105篇
  2021年   32篇
  2020年   35篇
  2019年   49篇
  2018年   46篇
  2017年   55篇
  2016年   38篇
  2015年   40篇
  2014年   51篇
  2013年   103篇
  2012年   126篇
  2011年   162篇
  2010年   71篇
  2009年   62篇
  2008年   125篇
  2007年   127篇
  2006年   117篇
  2005年   121篇
  2004年   126篇
  2003年   140篇
  2002年   136篇
  2001年   80篇
  2000年   80篇
  1999年   78篇
  1998年   30篇
  1997年   21篇
  1996年   21篇
  1992年   49篇
  1991年   45篇
  1990年   63篇
  1989年   56篇
  1988年   43篇
  1987年   50篇
  1986年   38篇
  1985年   41篇
  1984年   33篇
  1983年   21篇
  1982年   30篇
  1980年   22篇
  1979年   34篇
  1978年   32篇
  1975年   19篇
  1974年   24篇
  1973年   33篇
  1972年   24篇
  1971年   29篇
  1970年   42篇
  1969年   22篇
  1968年   30篇
  1967年   24篇
  1966年   24篇
排序方式: 共有3066条查询结果,搜索用时 328 毫秒
101.
The nucleotide sequences of 27 T-cell receptor beta cDNA clones isolated from a human peripheral lymphocyte library were determined and compared to five additional published sequences. These cDNA clones represent 22 distinct T-cell receptor beta-chain variable region (V beta) gene segment sequences, which fall into 15 different V beta gene subfamilies, each containing six or fewer members. From this analysis, we estimate that the repertoire of expressed human V beta genes is less than 59, apparently much smaller than the immunoglobulin heavy chain and light chain variable region (VH and VL) repertoires. Variability plots comparing these human V beta regions with each other and with published mouse V beta regions provide evidence for only four hypervariable regions homologous to those seen in comparisons of immunoglobulin V regions. Somatic hypermutation appears to be used infrequently, if at all, in these V beta genes.  相似文献   
102.
The class I genes of the major histocompatibility complex of the mouse can be divided into two categories: those encoding the transplantation antigens and those encoding the Qa and Tla antigens. The inbred BALB/c mouse has 28 potential Qa/Tla genes. The sites of tissue expression, developmental regulation, and functions of these genes are virtually unknown. We have used the technique of exon shuffling to construct hybrid genes between each of three Qa region genes (Q5, Q7, and Q8) and two other class I genes (H-2Ld and Q6). The hybrid genes have been transfected into mouse L cells, in which intact transplantation antigen genes generally are expressed and in which intact Qa genes generally are not expressed. Analysis of expression of the hybrid gene constructs indicates that the 5' half of two of the Qa genes (Q5 and Q8) can readily be expressed in the context of a hybrid molecule, whereas the 3' half prevents cell-surface expression. The exon shuffling approach described here will be useful in characterizing Qa/Tla genes and in identifying or producing new reagents to study the Qa/Tla gene products, their tissue distribution, their developmental stages of expression, and, ultimately, their functions.  相似文献   
103.
Myelin basic protein (MBP) or helper T cells reactive against MBP induce an autoimmune disease, experimental allergic encephalomyelitis, in B10.PL and PL/J inbred mice. In both strains, virtually the entire repertoire of MBP-specific T cells recognize an N-terminal peptide fragment in the context of the I-Au molecule encoded by the major histocompatibility complex (MHC) and utilize a very limited set of T-cell receptor genes. To delineate the nature of the trimolecular complex, consisting of the T-cell receptor, MBP-peptide fragment, and MHC molecule (I-Au), we have synthesized 13 variants of the 9-mer N-terminal immunodominant peptide differing at residue 4 and studied their immune recognition in vitro and in vivo. These substitutions have a striking range of effects on T-cell activation, ability to bind to the MHC molecule, and initiation of immune responses in vivo. An understanding of the autoimmune peptide/MHC/T-cell receptor interactions allowed us to design variant 9-mer peptides that have high affinity for an MHC molecule and are effective in blocking experimental allergic encephalomyelitis, possibly through two distinct mechanisms, peripheral T-cell tolerance and the inhibition of binding of the encephalitogenic peptide to the MHC molecules.  相似文献   
104.
D A Weiner  E C Schick  W B Hood  T J Ryan 《Chest》1978,74(2):133-138
Four patients underwent exercise testing because of a history of pain in the chest; all four developed marked elevation of the S-T segment only during recovery after exercise. Three of the four patients showed ST-segment depression during exercise, but ST-segment elevation was absent until two or more minutes after cessation of exercise. ST-segment elevation after exercise was accompanied by hypotension in three patients and by ventricular arrhythmias in one. Subsequent coronary angiographic studies revealed normal or minimally diseased coronary arteries in two patients and significant coronary lesions in the other two. Review of the literature shows that contrary to the prevailing belief, over half of the patients with Prinzmetal's variant angina have electrocardiographic changes diagnostic of ischemia during exercise testing. Over half of the patients with abnormal findings on tests during exercise display ST-segment elevation as a manifestation of ischemia; however, delayed ST-segment elevation of the type seen in these four patients is distinctly uncommon, having previously been described in only three individual case reports. The pathophysiology of this response is uncertain but may relate to rapid alterations in the autonomic balance during recovery after exercise.  相似文献   
105.

Background  

Wound infections are a common complication of surgery that add significantly to the morbidity of patients and costs of treatment. The global trend towards reducing length of hospital stay post-surgery and the increase in day case surgery means that surgical site infections (SSI) will increasingly occur after hospital discharge. Surveillance of SSIs is important because rates of SSI are viewed as a measure of hospital performance, however accurate detection of SSIs post-hospital discharge is not straightforward.  相似文献   
106.
Antimicrobial susceptibility was analyzed for 354 typhoidal Salmonella isolates collected during 1999–2012 in the Netherlands. In 16.1% of all isolates and in 23.8% of all isolates that showed increased MICs for ciprofloxacin, the MIC for azithromycin was increased. This resistance may complicate empirical treatment of enteric fever.  相似文献   
107.
108.
109.
110.
Journal of Thrombosis and Thrombolysis - Heparin-induced thrombocytopenia (HIT) is a rare adverse drug reaction. The anti-PF4 antibody assay (ELISA) is utilized to assist in the clinical evaluation...  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