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   305210篇
  免费   17990篇
  国内免费   477篇
耳鼻咽喉   4318篇
儿科学   10538篇
妇产科学   10690篇
基础医学   46045篇
口腔科学   7705篇
临床医学   25153篇
内科学   57815篇
皮肤病学   6433篇
神经病学   21583篇
特种医学   11852篇
外国民族医学   43篇
外科学   48102篇
综合类   7963篇
现状与发展   2篇
一般理论   161篇
预防医学   20345篇
眼科学   7098篇
药学   21521篇
中国医学   872篇
肿瘤学   15438篇
  2021年   2501篇
  2019年   2561篇
  2018年   3961篇
  2017年   2916篇
  2016年   3341篇
  2015年   3818篇
  2014年   5000篇
  2013年   7688篇
  2012年   9715篇
  2011年   10146篇
  2010年   6556篇
  2009年   5933篇
  2008年   9194篇
  2007年   10009篇
  2006年   9825篇
  2005年   9412篇
  2004年   9072篇
  2003年   8518篇
  2002年   8122篇
  2001年   13550篇
  2000年   13853篇
  1999年   11582篇
  1998年   3071篇
  1997年   2845篇
  1996年   2671篇
  1995年   2580篇
  1994年   2377篇
  1992年   8396篇
  1991年   8518篇
  1990年   8326篇
  1989年   8131篇
  1988年   7361篇
  1987年   7098篇
  1986年   6750篇
  1985年   6552篇
  1984年   4783篇
  1983年   4139篇
  1982年   2482篇
  1979年   4444篇
  1978年   3238篇
  1977年   2744篇
  1976年   2514篇
  1975年   2846篇
  1974年   3358篇
  1973年   3374篇
  1972年   3130篇
  1971年   2955篇
  1970年   2847篇
  1969年   2586篇
  1968年   2543篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
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   
3.
4.
5.
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   
6.
7.
8.
9.
10.
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