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   1729506篇
  免费   136905篇
  国内免费   4126篇
耳鼻咽喉   24398篇
儿科学   55360篇
妇产科学   49860篇
基础医学   251322篇
口腔科学   50093篇
临床医学   155281篇
内科学   330671篇
皮肤病学   37401篇
神经病学   138935篇
特种医学   67988篇
外国民族医学   462篇
外科学   264099篇
综合类   44939篇
现状与发展   2篇
一般理论   634篇
预防医学   136487篇
眼科学   41007篇
药学   127394篇
  3篇
中国医学   3369篇
肿瘤学   90832篇
  2018年   16837篇
  2016年   15083篇
  2015年   17235篇
  2014年   24006篇
  2013年   36720篇
  2012年   48758篇
  2011年   51509篇
  2010年   30576篇
  2009年   28800篇
  2008年   48373篇
  2007年   51920篇
  2006年   52115篇
  2005年   50585篇
  2004年   49463篇
  2003年   47436篇
  2002年   45928篇
  2001年   75265篇
  2000年   76950篇
  1999年   64910篇
  1998年   19052篇
  1997年   17381篇
  1996年   17249篇
  1995年   16411篇
  1994年   15566篇
  1993年   14592篇
  1992年   53741篇
  1991年   52726篇
  1990年   51828篇
  1989年   50065篇
  1988年   46141篇
  1987年   46085篇
  1986年   43295篇
  1985年   42112篇
  1984年   32064篇
  1983年   27440篇
  1982年   16836篇
  1981年   15378篇
  1979年   31168篇
  1978年   22531篇
  1977年   18998篇
  1976年   17799篇
  1975年   18957篇
  1974年   23286篇
  1973年   22422篇
  1972年   20922篇
  1971年   19456篇
  1970年   18392篇
  1969年   17510篇
  1968年   15978篇
  1967年   14526篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Vaskulitiden     
  相似文献   
62.
Red cell exchange (RCE) is a common procedure in adults with sickle cell disease (SCD). Implantable dual lumen Vortex (DLV) ports can be used for RCE in patients with poor peripheral venous access. We performed a retrospective cohort study of RCE procedures performed in adults with SCD. The main objective of the study was to compare the inlet speed, duration of procedures and rate of complications performed through DLV ports to those performed through temporary central venous and peripheral catheters. Twenty‐nine adults with SCD underwent a total of 318 RCE procedures. Twenty adults had DLV ports placed and 218 procedures were performed using DLV ports. Mean length of follow‐up after DLV port placement was 397 ± 263 days. Six DLV ports were removed due to infection and 1 for malfunction after a mean of 171 ± 120 days. Compared to temporary central venous and peripheral catheters, DLV port procedures had a greater rate of procedural complications, a longer duration, and a lower inlet speed (all P < 0.01). When accounting for the maximum allowable inlet speed to avoid citrate toxicity, 40% of DLV port procedures were greater than 10% below maximum speed, compared to 7 and 14% of procedures performed through temporary central venous and peripheral catheters (P < 0.0001). In conclusion, DLV ports can be used for RCE in adults with SCD, albeit with more procedural complications and longer duration. The smaller internal diameter and longer catheter of DLV ports compared to temporary central venous catheters likely accounts for the differences noted. J. Clin. Apheresis 30:353–358, 2015. © 2015 Wiley Periodicals, Inc.  相似文献   
63.
64.
The catechol-O-methyltransferase (COMT) enzyme is a major determinant of prefrontal dopamine levels. The Val158Met polymorphism affects COMT enzymatic activity and has been associated with variation in executive function and affective processing. This study investigated the effect of COMT genotype on the flexible modulation of the balance between processing self-generated and processing stimulus-oriented information, in the presence or absence of affective distractors. Analyses included 124 healthy adult participants, who were also assessed on standard working memory (WM) tasks. Relative to Val carriers, Met homozygotes made fewer errors when selecting and manipulating self-generated thoughts. This effect was partly accounted for by an association between COMT genotype and visuospatial WM performance. We also observed a complex interaction between the influence of affective distractors, COMT genotype and sex on task accuracy: male, but not female, participants showed a sensitivity to the affective distractors that was dependent on COMT genotype. This was not accounted for by WM performance. This study provides novel evidence of the role of dopaminergic genetic variation on the ability to select and manipulate self-generated thoughts. The results also suggest sexually dimorphic effects of COMT genotype on the influence of affective distractors on executive function.  相似文献   
65.
Preimplantation genetic diagnosis (PGD) was originally developed to diagnose embryo-related genetic abnormalities for couples who present a high risk of a specific inherited disorder. Because this technology involves embryo selection, the medical, bioethical, and legal implications of the technique have been debated, particularly when it is used to select features that are not related to serious diseases. Although several initiatives have attempted to achieve regulatory harmonization, the diversity of healthcare services available and the presence of cultural differences have hampered attempts to achieve this goal. Thus, in different countries, the provision of PGD and regulatory frameworks reflect the perceptions of scientific groups, legislators, and society regarding this technology. In Brazil, several texts have been analyzed by the National Congress to regulate the use of assisted reproduction technologies. Legislative debates, however, are not conclusive, and limited information has been published on how PGD is specifically regulated. The country requires the development of new regulatory standards to ensure adequate access to this technology and to guarantee its safe practice. This study examined official documents published on PGD regulation in Brazil and demonstrated how little direct oversight of PGD currently exists. It provides relevant information to encourage reflection on a particular regulation model in a Brazilian context, and should serve as part of the basis to enable further reform of the clinical practice of PGD in the country.  相似文献   
66.
67.
68.
A 42‐year‐old man presented with a viral prodrome and tested positive for influenza A. He rapidly deteriorated developing cardiogenic shock, rhabdomyolysis, and acute kidney injury. Patient improved 1 week later with supportive measures including vasopressors, inotropes, and an intraaortic balloon pump. We report this case as it highlights the discordance between echocardiographic ventricular wall thickening as a result of myocardial edema, and electrocardiographic findings at presentation, with a reversal in findings at time of resolution. Additionally, there was some suggestion of a regional pattern to the reduced longitudinal strain.  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