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   334497篇
  免费   19715篇
  国内免费   538篇
耳鼻咽喉   4569篇
儿科学   11233篇
妇产科学   11052篇
基础医学   49922篇
口腔科学   8129篇
临床医学   27857篇
内科学   63129篇
皮肤病学   6886篇
神经病学   24985篇
特种医学   12859篇
外国民族医学   43篇
外科学   52978篇
综合类   8203篇
现状与发展   2篇
一般理论   194篇
预防医学   23079篇
眼科学   7947篇
药学   23470篇
中国医学   899篇
肿瘤学   17314篇
  2021年   3071篇
  2019年   3022篇
  2018年   4589篇
  2017年   3359篇
  2016年   3776篇
  2015年   4304篇
  2014年   5837篇
  2013年   8857篇
  2012年   11757篇
  2011年   12270篇
  2010年   7700篇
  2009年   6977篇
  2008年   11238篇
  2007年   12263篇
  2006年   11955篇
  2005年   11508篇
  2004年   11104篇
  2003年   10445篇
  2002年   9877篇
  2001年   13686篇
  2000年   13968篇
  1999年   11789篇
  1998年   3454篇
  1997年   3172篇
  1996年   3004篇
  1995年   2849篇
  1994年   2633篇
  1992年   8526篇
  1991年   8634篇
  1990年   8412篇
  1989年   8215篇
  1988年   7471篇
  1987年   7217篇
  1986年   6852篇
  1985年   6652篇
  1984年   4901篇
  1983年   4273篇
  1982年   2658篇
  1979年   4510篇
  1978年   3337篇
  1977年   2844篇
  1976年   2588篇
  1975年   2920篇
  1974年   3426篇
  1973年   3420篇
  1972年   3171篇
  1971年   2991篇
  1970年   2874篇
  1969年   2610篇
  1968年   2562篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Potential for widespread transmission of HIV/AIDS among American Indian (AI) adolescents exists, yet no evidence-based interventions (EBIs) have been adapted and evaluated with this population. Intensive psychoeducation may improve knowledge and decision-making which could potentially translate to reductions in HIV risk behaviors. A peer group randomized controlled comparison of an adapted EBI vs. control was delivered over an eight-day summer basketball camp in one reservation-based tribal community to adolescents ages 13–19. Outcome data were gathered immediately post-camp and at 6 and 12 months follow-up. Self-selected peer groups were randomized to intervention (n = 138) or control (n = 129) conditions for a total sample of 267 participants (56.2% female), mean age 15.1 years (SD = 1.7). Intervention participants had better condom use self-efficacy post-camp (Adjusted Mean Difference [AMD] = ?0.75, p < 0.005) and at 6 (AMD = ?0.44, p < 0.005) and 12 months (AMD = ?0.23, p < 0.05) follow-up. Intervention participants also had higher HIV prevention and transmission knowledge (post-camp: AMD = 0.07, p < 0.01; 6 months: AMD = 0.06, p < 0.01) were more likely to believe condoms prevent sexually transmitted infections (post-camp: RR = 1.41, p < 0.005; 6 months: RR = 1.34, p < 0.05), to talk with an adult about HIV/AIDS (post-camp: RR=1.78, p < 0.005; 6 months: RR = 1.14, p < 0.005), had higher partner negotiation efficacy related to substance use during sex (post-camp: AMD = 0.37, p < 0.01), and were more likely to intend to use a condom (post-camp: RR = 1.39, p < 0.01). The adapted intervention had short- and medium-term impacts on AI adolescent risk for HIV/AIDS, but attenuated at 12 months. Intervention delivery through a community-based camp is feasible and acceptable with strong retention. Additional study is needed to evaluate the adapted intervention's impact on sexual risk behaviors and if booster sessions and parent involvement translate to long-term impacts.  相似文献   
3.
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   
4.
5.
6.
7.
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   
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