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   361566篇
  免费   20729篇
  国内免费   558篇
耳鼻咽喉   5056篇
儿科学   11732篇
妇产科学   11567篇
基础医学   53585篇
口腔科学   10049篇
临床医学   29180篇
内科学   72081篇
皮肤病学   7923篇
神经病学   26792篇
特种医学   13078篇
外国民族医学   43篇
外科学   55517篇
综合类   8045篇
现状与发展   1篇
一般理论   186篇
预防医学   25547篇
眼科学   8178篇
药学   25178篇
中国医学   1026篇
肿瘤学   18089篇
  2021年   3302篇
  2019年   3399篇
  2018年   5645篇
  2017年   3870篇
  2016年   4365篇
  2015年   5467篇
  2014年   6579篇
  2013年   10144篇
  2012年   14782篇
  2011年   15027篇
  2010年   8691篇
  2009年   7433篇
  2008年   13406篇
  2007年   14431篇
  2006年   14466篇
  2005年   13768篇
  2004年   12994篇
  2003年   12068篇
  2002年   11518篇
  2001年   14770篇
  2000年   15568篇
  1999年   12347篇
  1998年   3225篇
  1997年   2936篇
  1996年   2788篇
  1995年   2687篇
  1994年   2450篇
  1992年   8430篇
  1991年   8559篇
  1990年   8329篇
  1989年   8151篇
  1988年   7367篇
  1987年   7121篇
  1986年   6782篇
  1985年   6585篇
  1984年   4852篇
  1983年   4175篇
  1982年   2545篇
  1979年   4470篇
  1978年   3265篇
  1977年   2766篇
  1976年   2537篇
  1975年   2856篇
  1974年   3385篇
  1973年   3388篇
  1972年   3123篇
  1971年   2961篇
  1970年   2851篇
  1969年   2594篇
  1968年   2541篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
In the current immunosuppressive therapy era, vessel thrombosis is the most common cause of early graft loss after renal transplantation. The prevalence of IgA anti–β2-glycoprotein I antibodies (IgA-aB2GPI-ab) in patients on dialysis is elevated (>30%), and these antibodies correlate with mortality and cardiovascular morbidity. To evaluate the effect of IgA-aB2GPI-ab in patients with transplants, we followed all patients transplanted from 2000 to 2002 in the Hospital 12 de Octubre prospectively for 10 years. Presence of IgA-aB2GPI-ab in pretransplant serum was examined retrospectively. Of 269 patients, 89 patients were positive for IgA-aB2GPI-ab (33%; group 1), and the remaining patients were negative (67%; group 2). Graft loss at 6 months post-transplant was significantly higher in group 1 (10 of 89 versus 3 of 180 patients in group 2; P=0.002). The most frequent cause of graft loss was thrombosis of the vessels, which was observed only in group 1 (8 of 10 versus 0 of 3 patients in group 2; P=0.04). Multivariate analysis showed that the presence of IgA-aB2GPI-ab was an independent risk factor for early graft loss (P=0.04) and delayed graft function (P=0.04). There were no significant differences regarding patient survival between the two groups. Graft survival was similar in both groups after 6 months. In conclusion, patients with pretransplant IgA-aB2GPI-ab have a high risk of early graft loss caused by thrombosis and a high risk of delayed graft function. Therefore, pretransplant IgA-aB2GPI-ab may have a detrimental effect on early clinical outcomes after renal transplantation.  相似文献   
5.
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   
6.
7.
8.
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   
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