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   982178篇
  免费   77959篇
  国内免费   1931篇
耳鼻咽喉   14870篇
儿科学   28859篇
妇产科学   27907篇
基础医学   142075篇
口腔科学   29589篇
临床医学   85462篇
内科学   186438篇
皮肤病学   20554篇
神经病学   82508篇
特种医学   40306篇
外国民族医学   171篇
外科学   154360篇
综合类   25148篇
现状与发展   2篇
一般理论   300篇
预防医学   73839篇
眼科学   23214篇
药学   73143篇
中国医学   1782篇
肿瘤学   51541篇
  2018年   9992篇
  2016年   9528篇
  2015年   10256篇
  2014年   13891篇
  2013年   21800篇
  2012年   29073篇
  2011年   31093篇
  2010年   17949篇
  2009年   15734篇
  2008年   29842篇
  2007年   32262篇
  2006年   31866篇
  2005年   31431篇
  2004年   30554篇
  2003年   29746篇
  2002年   28711篇
  2001年   40149篇
  2000年   41963篇
  1999年   33979篇
  1998年   10438篇
  1997年   9555篇
  1996年   9267篇
  1995年   8663篇
  1994年   8357篇
  1992年   27240篇
  1991年   26592篇
  1990年   26093篇
  1989年   25162篇
  1988年   23638篇
  1987年   23378篇
  1986年   22123篇
  1985年   21668篇
  1984年   16969篇
  1983年   14470篇
  1982年   9349篇
  1981年   8655篇
  1980年   8107篇
  1979年   17107篇
  1978年   12490篇
  1977年   10586篇
  1976年   9666篇
  1975年   10500篇
  1974年   12963篇
  1973年   12410篇
  1972年   11751篇
  1971年   10912篇
  1970年   10420篇
  1969年   10098篇
  1968年   9100篇
  1967年   8422篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
Analyzing functional species’ characteristics (species traits) that represent physiological, life history and morphological characteristics of species help understanding the impacts of various stressors on aquatic communities at field conditions. This research aimed to study the combined effects of pesticides and other environmental factors (temperature, dissolved oxygen, dissolved organic carbon, floating macrophytes cover, phosphate, nitrite, and nitrate) on the trait modality distribution of aquatic macrofauna communities. To this purpose, a field inventory was performed in a flower bulb growing area of the Netherlands with significant variation in pesticides pressures. Macrofauna community composition, water chemistry parameters and pesticide concentrations in ditches next to flower bulb fields were determined. Trait modalities of nine traits (feeding mode, respiration mode, locomotion type, resistance form, reproduction mode, life stage, voltinism, saprobity, maximum body size) likely to indicate pesticides impacts were analyzed. According to a redundancy analysis, phosphate -and not pesticides- constituted the main factor structuring the trait modality distribution of aquatic macrofauna. The functional composition could be ascribed for 2–4 % to pesticides, and for 3–11 % to phosphate. The lack of trait responses to pesticides may indicate that species may have used alternative strategies to adapt to ambient pesticides stress. Biomass of animals exhibiting trait modalities related to feeding by predation and grazing, presence of diapause form or dormancy, reproduction by free clutches and ovoviviparity, life stage of larvae and pupa, was negatively correlated to the concentration of phosphate. Hence, despite the high pesticide pollution in the area, variation in nutrient-related stressors seems to be the dominant driver of the functional composition of aquatic macrofauna assembly in agricultural ditches.  相似文献   
32.
33.
34.
Lasers in Medical Science - Studies reported the harmful effects of 2,4-D on body tissues, provoking changes in the anatomy and physiology of the kidneys, liver, and testicles. Thus, the objective...  相似文献   
35.
Background: Poor anger regulation is considered a risk factor of aggression in individuals with mild or borderline intellectual disabilities. Psychomotor therapy (PMT) targets anger regulation through body- and movement-oriented interventions. This study aims to inform practitioners on efficacy and research-base of PMT in this population.

Method: This systematic review evaluated nine studies which met inclusion criteria in terms of participants, intervention procedures, outcomes and certainty of evidence.

Results: Seven studies revealed a substantial reduction of aggressive behaviour or anger. Certainty of evidence was rated inconclusive in most cases due to absence of experimental control.

Conclusions: We can conclude that body-oriented PMT, involving progressive relaxation and meditation procedure “Soles of the Feet”, is a promising approach. However, the paucity of studies and methodological limitations preclude classifying it as an evidence-based practice. This suggests stronger methodological research and research aimed at PMT’s mechanisms of action (e.g., improved interoceptive awareness) is warranted.  相似文献   

36.
37.
38.
39.
40.
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   
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