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   2236037篇
  免费   183383篇
  国内免费   4137篇
耳鼻咽喉   31753篇
儿科学   71185篇
妇产科学   64699篇
基础医学   319722篇
口腔科学   66561篇
临床医学   197757篇
内科学   431924篇
皮肤病学   47128篇
神经病学   182083篇
特种医学   89897篇
外国民族医学   633篇
外科学   342673篇
综合类   58681篇
现状与发展   5篇
一般理论   771篇
预防医学   174750篇
眼科学   52493篇
药学   168476篇
  3篇
中国医学   4259篇
肿瘤学   118104篇
  2018年   20607篇
  2015年   21096篇
  2014年   29433篇
  2013年   44918篇
  2012年   60610篇
  2011年   63830篇
  2010年   37606篇
  2009年   35723篇
  2008年   60808篇
  2007年   64956篇
  2006年   65389篇
  2005年   63771篇
  2004年   62810篇
  2003年   60218篇
  2002年   58651篇
  2001年   99720篇
  2000年   102758篇
  1999年   87292篇
  1998年   24766篇
  1997年   22643篇
  1996年   22525篇
  1995年   21743篇
  1994年   20545篇
  1993年   19315篇
  1992年   72791篇
  1991年   70727篇
  1990年   69220篇
  1989年   66864篇
  1988年   62547篇
  1987年   61558篇
  1986年   58573篇
  1985年   56698篇
  1984年   43005篇
  1983年   36963篇
  1982年   22556篇
  1981年   20361篇
  1980年   19017篇
  1979年   42074篇
  1978年   29693篇
  1977年   25028篇
  1976年   23337篇
  1975年   24903篇
  1974年   30693篇
  1973年   29421篇
  1972年   27340篇
  1971年   25742篇
  1970年   23909篇
  1969年   22780篇
  1968年   20674篇
  1967年   18874篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
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   
62.
63.
64.
65.
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   

66.

Background

Resistin is an immunometabolic mediator that is elevated in several inflammatory disorders. A ligand for Toll-like receptor 4, resistin modulates the recruitment and activation of myeloid cells, notably neutrophils. Neutrophils are major drivers of cystic fibrosis (CF) lung disease, in part due to the release of human neutrophil elastase- and myeloperoxidase-rich primary granules, leading to tissue damage. Here we assessed the relationship of resistin to CF lung disease.

Methods

Resistin levels were measured in plasma and sputum from three retrospective CF cohorts spanning a wide range of disease. We also assessed the ability of neutrophils to secrete resistin upon activation in vitro. Finally, we constructed a multivariate model assessing the relationship between resistin levels and lung function.

Results

Plasma resistin levels were only marginally higher in CF than in healthy control subjects. By contrast, sputum resistin levels were very high in CF, reaching 50–100 fold higher levels than in plasma. Among CF patients, higher plasma resistin levels were associated with allergic bronchopulmonary aspergillosis, and higher sputum resistin levels were associated with CF-related diabetes. Mechanistically, in vitro release of neutrophil primary granules was concomitant with resistin secretion. Overall, sputum resistin levels were negatively correlated with CF lung function, independently of other variables (age, sex, and genotype).

Conclusions

Our data establish relationships between resistin levels in the plasma and sputum of CF patients that correlate with disease status, and identify resistin as a novel mechanistic link between neutrophilic inflammation and lung disease in CF.  相似文献   
67.
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