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   2418655篇
  免费   200946篇
  国内免费   4402篇
耳鼻咽喉   34962篇
儿科学   73974篇
妇产科学   63743篇
基础医学   340564篇
口腔科学   68606篇
临床医学   220445篇
内科学   478276篇
皮肤病学   48896篇
神经病学   205380篇
特种医学   97373篇
外国民族医学   886篇
外科学   367853篇
综合类   56846篇
现状与发展   1篇
一般理论   1023篇
预防医学   194486篇
眼科学   56441篇
药学   180366篇
  7篇
中国医学   4409篇
肿瘤学   129466篇
  2018年   25253篇
  2017年   19567篇
  2016年   21481篇
  2015年   24306篇
  2014年   34939篇
  2013年   52903篇
  2012年   71920篇
  2011年   75776篇
  2010年   44386篇
  2009年   42621篇
  2008年   71904篇
  2007年   76344篇
  2006年   77134篇
  2005年   75206篇
  2004年   72370篇
  2003年   69952篇
  2002年   69008篇
  2001年   112885篇
  2000年   116916篇
  1999年   98837篇
  1998年   28430篇
  1997年   26008篇
  1996年   25866篇
  1995年   25035篇
  1994年   23522篇
  1993年   21862篇
  1992年   79675篇
  1991年   76653篇
  1990年   73814篇
  1989年   71031篇
  1988年   66075篇
  1987年   65012篇
  1986年   61560篇
  1985年   58620篇
  1984年   44463篇
  1983年   37880篇
  1982年   23196篇
  1981年   20594篇
  1980年   19270篇
  1979年   41424篇
  1978年   29117篇
  1977年   24474篇
  1976年   22919篇
  1975年   24036篇
  1974年   29727篇
  1973年   28134篇
  1972年   26282篇
  1971年   24198篇
  1970年   22791篇
  1969年   21126篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
62.

Researchers have highlighted numerous sociocultural factors that have been shown to underpin human appearance enhancement practices, including the influence of peers, family, the media, and sexual objectification. Fewer scholars have approached appearance enhancement from an evolutionary perspective or considered how sociocultural factors interact with evolved psychology to produce appearance enhancement behavior. Following others, we argue that evidence from the field of evolutionary psychology can complement existing sociocultural models by yielding unique insight into the historical and cross-cultural ubiquity of competition over aspects of physical appearance to embody what is desired by potential mates. An evolutionary lens can help to make sense of reliable sex and individual differences that impact appearance enhancement, as well as the context-dependent nature of putative adaptations that function to increase physical attractiveness. In the current review, appearance enhancement is described as a self-promotion strategy used to enhance reproductive success by rendering oneself more attractive than rivals to mates, thereby increasing one’s mate value. The varied ways in which humans enhance their appearance are described, as well as the divergent tactics used by women and men to augment their appearance, which correspond to the preferences of opposite-sex mates in a heterosexual context. Evolutionarily relevant individual differences and contextual factors that vary predictably with appearance enhancement behavior are also discussed. The complementarity of sociocultural and evolutionary perspectives is emphasized and recommended avenues for future interdisciplinary research are provided for scholars interested in studying appearance enhancement behavior.

  相似文献   
63.
64.
65.
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   
66.
67.
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   
68.
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