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   3923773篇
  免费   298691篇
  国内免费   6721篇
耳鼻咽喉   56459篇
儿科学   124521篇
妇产科学   105559篇
基础医学   565288篇
口腔科学   112365篇
临床医学   361162篇
内科学   750001篇
皮肤病学   83435篇
神经病学   319525篇
特种医学   151345篇
外国民族医学   1277篇
外科学   590348篇
综合类   89536篇
现状与发展   13篇
一般理论   1604篇
预防医学   317160篇
眼科学   93777篇
药学   294113篇
  13篇
中国医学   7546篇
肿瘤学   204138篇
  2018年   42179篇
  2017年   31996篇
  2016年   35717篇
  2015年   40343篇
  2014年   57705篇
  2013年   87768篇
  2012年   119339篇
  2011年   126902篇
  2010年   75480篇
  2009年   71427篇
  2008年   119457篇
  2007年   127296篇
  2006年   128505篇
  2005年   124889篇
  2004年   120146篇
  2003年   115575篇
  2002年   113247篇
  2001年   175052篇
  2000年   180580篇
  1999年   152791篇
  1998年   45606篇
  1997年   40445篇
  1996年   40025篇
  1995年   38339篇
  1994年   35741篇
  1993年   33556篇
  1992年   121603篇
  1991年   118646篇
  1990年   115297篇
  1989年   111099篇
  1988年   102943篇
  1987年   101099篇
  1986年   95452篇
  1985年   91714篇
  1984年   69278篇
  1983年   59096篇
  1982年   35805篇
  1981年   32060篇
  1979年   64982篇
  1978年   46086篇
  1977年   38689篇
  1976年   36874篇
  1975年   39093篇
  1974年   47666篇
  1973年   45380篇
  1972年   42889篇
  1971年   40136篇
  1970年   37355篇
  1969年   35161篇
  1968年   32294篇
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
141.
142.
143.
144.
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   
145.
146.
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   
147.
The present study aimed at measuring seropositivities for infection by Ascaris suum and Toxocara canis using the excretory/secretory (E/S) antigens from Ascaris suum (AES) and Toxocara canis (TES) within an indigenous population. In addition, quantification of cytokine expressions in peripheral blood cells was determined. A total of 50 Warao indigenous were included; of which 43 were adults and seven children. In adults, 44.1% were seropositive for both parasites; whereas children had only seropositivity to one or the other helminth. For ascariosis, the percentage of AES seropositivity in adults and children was high; 23.3% and 57.1%, respectively. While that for toxocariosis, the percentage of TES seropositivity in adults and children was low; 9.3% and 14.3%, respectively. The percentage of seronegativity was comparable for AES and TES antigens in adults (27.9%) and children (28.6%). When positive sera were analyzed by Western blotting technique using AES antigens; three bands of 97.2, 193.6 and 200.2 kDas were mostly recognized. When the TES antigens were used, nine major bands were mostly identified; 47.4, 52.2, 84.9, 98.2, 119.1, 131.3, 175.6, 184.4 and 193.6 kDas. Stool examinations showed that Blastocystis hominis, Hymenolepis nana and Entamoeba coli were the most commonly observed intestinal parasites. Quantification of cytokines IFN-γ, IL-2, IL-6, TGF-β, TNF-α, IL-10 and IL-4 expressions showed that there was only a significant increased expression of IL-4 in indigenous with TES seropositivity (p < 0.002). Ascaris and Toxocara seropositivity was prevalent among Warao indigenous.  相似文献   
148.
149.
150.
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   
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