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   296644篇
  免费   17614篇
  国内免费   428篇
耳鼻咽喉   4230篇
儿科学   10412篇
妇产科学   10250篇
基础医学   44999篇
口腔科学   7502篇
临床医学   24195篇
内科学   55907篇
皮肤病学   6369篇
神经病学   21011篇
特种医学   11629篇
外国民族医学   43篇
外科学   46846篇
综合类   7806篇
现状与发展   1篇
一般理论   162篇
预防医学   19925篇
眼科学   6981篇
药学   20993篇
中国医学   788篇
肿瘤学   14637篇
  2018年   3645篇
  2017年   2692篇
  2016年   3113篇
  2015年   3503篇
  2014年   4612篇
  2013年   7239篇
  2012年   9127篇
  2011年   9497篇
  2010年   6169篇
  2009年   5560篇
  2008年   8715篇
  2007年   9551篇
  2006年   9400篇
  2005年   8987篇
  2004年   8685篇
  2003年   8188篇
  2002年   7773篇
  2001年   13327篇
  2000年   13661篇
  1999年   11425篇
  1998年   3026篇
  1997年   2793篇
  1996年   2641篇
  1995年   2550篇
  1994年   2344篇
  1992年   8319篇
  1991年   8456篇
  1990年   8268篇
  1989年   8079篇
  1988年   7316篇
  1987年   7080篇
  1986年   6726篇
  1985年   6520篇
  1984年   4767篇
  1983年   4120篇
  1982年   2471篇
  1979年   4430篇
  1978年   3232篇
  1977年   2735篇
  1976年   2506篇
  1975年   2838篇
  1974年   3355篇
  1973年   3364篇
  1972年   3119篇
  1971年   2951篇
  1970年   2841篇
  1969年   2589篇
  1968年   2540篇
  1967年   2374篇
  1966年   2268篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
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   
13.
14.
15.
16.
Pharmaceutical Chemistry Journal - Three extracts were produced from the above-ground part of the meadowsweet Filipendula ulmaria (L.) Maxim. using water, 40% ethanol, and 70% ethanol. Comparative...  相似文献   
17.
18.
19.
20.
Objective: Report efficacy findings from three clinical trials (one phase 2 and two phase 3 [OPUS-1, OPUS-2]) of lifitegrast ophthalmic solution 5.0% for treatment of dry eye disease (DED).

Research design and methods: Three 84-day, randomized, double-masked, placebo-controlled trials. Adults (≥18 years) with DED were randomized (1:1) to lifitegrast 5.0% or matching placebo. Changes from baseline to day 84 in signs and symptoms of DED were analyzed.

Main outcome measures: Phase 2, pre-specified endpoint: inferior corneal staining score (ICSS; 0–4); OPUS-1, coprimary endpoints: ICSS and visual-related function subscale (0–4 scale); OPUS-2, coprimary endpoints: ICSS and eye dryness score (EDS, VAS; 0–100).

Results: Fifty-eight participants were randomized to lifitegrast 5.0% and 58 to placebo in the phase 2 trial; 293 to lifitegrast and 295 to placebo in OPUS-1; 358 to lifitegrast and 360 to placebo in OPUS-2. In participants with mild-to-moderate baseline DED symptomatology, lifitegrast improved ICSS versus placebo in the phase 2 study (treatment effect, 0.35; 95% CI, 0.05–0.65; p?=?0.0209) and OPUS-1 (effect, 0.24; 95% CI, 0.10–0.38; p?=?0.0007). Among more symptomatic participants (baseline EDS ≥40, recent artificial tear use), lifitegrast improved EDS versus placebo in a post hoc analysis of OPUS-1 (effect, 13.34; 95% CI, 2.35–24.33; nominal p?=?0.0178) and in OPUS-2 (effect, 12.61; 95% CI, 8.51–16.70; p?<?0.0001).

Limitations: Trials were conducted over 12 weeks; efficacy beyond this period was not assessed.

Conclusions: Across three trials, lifitegrast improved ICSS in participants with mild-to-moderate baseline symptomatology in two studies, and EDS in participants with moderate-to-severe baseline symptomatology in two studies. Based on the overall findings from these trials, lifitegrast shows promise as a new treatment option for signs and symptoms of DED.  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