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   2348篇
  免费   136篇
  国内免费   27篇
耳鼻咽喉   28篇
儿科学   53篇
妇产科学   45篇
基础医学   276篇
口腔科学   59篇
临床医学   211篇
内科学   625篇
皮肤病学   27篇
神经病学   99篇
特种医学   80篇
外科学   394篇
综合类   82篇
一般理论   1篇
预防医学   146篇
眼科学   22篇
药学   175篇
中国医学   22篇
肿瘤学   166篇
  2023年   16篇
  2022年   72篇
  2021年   112篇
  2020年   60篇
  2019年   84篇
  2018年   90篇
  2017年   56篇
  2016年   71篇
  2015年   72篇
  2014年   109篇
  2013年   113篇
  2012年   200篇
  2011年   186篇
  2010年   90篇
  2009年   84篇
  2008年   141篇
  2007年   115篇
  2006年   136篇
  2005年   133篇
  2004年   103篇
  2003年   85篇
  2002年   75篇
  2001年   35篇
  2000年   33篇
  1999年   46篇
  1998年   20篇
  1997年   12篇
  1996年   18篇
  1995年   6篇
  1994年   13篇
  1993年   8篇
  1992年   12篇
  1991年   16篇
  1990年   15篇
  1989年   11篇
  1988年   12篇
  1987年   11篇
  1986年   7篇
  1985年   15篇
  1984年   3篇
  1983年   3篇
  1981年   1篇
  1980年   2篇
  1979年   1篇
  1978年   3篇
  1972年   1篇
  1970年   1篇
  1966年   1篇
  1965年   1篇
  1964年   1篇
排序方式: 共有2511条查询结果,搜索用时 23 毫秒
21.
In the present study, two of the probable an umor marine compounds, manzamine A and sarcophine, were screened using benzo[a]pyrene (BP)-derived DNA adduct formation in MCF-7 cells as intermediary biomarker. Briefly, MCF-7 cells were treated with the compounds for 24 h followed by treatment with BP (0.5 μM). After 24h incubation, cellular DNA was isolated and analyzed for BP-derived DNA adducts by 32P-postlabeling technique. Manzamine A and sarcophine increased the BP-DNA adducts by 2 to 4-folds. Further, manzamine A (50 μM) substantially down regulated the expression of p53 while sarcophine (50 μM) slightly induced the level of p21. The residual DNA repair ability was almost completely abolished by manzamine A while sarcophine was ineffective. Based on our preliminary results, these compounds may be classified as potential genotoxic.  相似文献   
22.
23.
24.
Abstract

The leaf oils of eight Cinnamomum. species (C. rhyncophyllum. Miq., C. microphyllum. Ridl., C. pubescens. Kochummen, C. mollissimum. Hook. f., C. impressicostatum. Kosterm, C. scortechinii. Gamb., C. sintoc. Bl., and C. cordatum. Kosterm) were investigated for their larvicidal and adulticidal activities against Aedes aegypti. (Aedes aegypti Lynn) and Aedes albopictus. (Aedes albopictus Skuse). Acute mortalities of the fourth instar larvae and the adult mosquitoes were determined according to the standard WHO methods. Among the essential oils studied, the leaf oils of C. rhyncophyllum., C. microphyllum., C. pubescens., C. mollissimum., and C. impressicostatum. showed significant effects against the larvae of Ae. aegypti. and Ae. albopictus. with concentrations that caused 50% mortality (LC50) values of less than 12.8 and 11.8 µg ml?1, respectively. The essential oils that showed strong larvicidal effects also demonstrated relatively strong adulticidal effects on the mosquitoes after 3 h exposure with LC50 values ranging from 133.0 to 243.0 µg ml?1 against Ae. aegypti. and from 118.0 to 194.0 µg ml?1 against Ae. albopictus.. The efficacy of the oils toward the larvae and adult mosquitoes of both species was nonselective as the LC50 values showed little variation. The chemical composition of the oils was investigated by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). This study suggested that the essential oils containing high levels of benzyl benzoate and benzyl salicylate exhibited strong insecticidal activities against the larvae and adult mosquitoes.  相似文献   
25.
26.
27.
28.
Abstract

This study examined Type A and Type B differences in job performance, psychosomatic complaints, and career progression among white-collar employees (N = 218) in a field setting. Significant differences were found between Type A's and Type B's in quality of performance, effort exerted at the job, and psychosomatic complaints. Employees' cultural background and sex moderated some of the relationships observed in the study. Implications of the findings for future research on the topic are discussed.  相似文献   
29.
Mannitol is commonly used to lower intracranial and intraocular pressures. Large doses/massive infusions of mannitol have been found to be associated with acute renal failure (MI-ARF), that is, osmotic nephrosis. While many researchers have reported individual experiences with this pathology, we felt that there is need of an updated comprehensive review of all reported cases with elaboration of etiology, pathogenesis, diagnosis and management plan for MI-ARF. The purpose of the present communication is to share our own experience with MI-ARF, to review the effect of mannitol on kidney function and to highlight the dynamics of MI-ARF with considerations for the cautious use of mannitol in patients with risk factors for kidney diseases.  相似文献   
30.
ObjectiveWe conducted a systematic review and dose–response meta-analysis of prospective studies to summarize findings on the associations between intakes of soy, soy isoflavones, and soy protein and risk of mortality from all causes, cancers, and cardiovascular diseases.MethodsOnline databases were systematically searched to identify relevant articles published earlier than May 2018. We applied restricted cubic splines using random-effects analysis to assess dose–response associations. Between-study heterogeneity was assessed by I2 value and Cochrane Q test. Potential publication bias was assessed by visual inspection of funnel plots and Begg regression test.ResultsIn total, 23 prospective studies with an overall sample size of 330,826 participants were included in the current systematic review and the meta-analysis. Soy/soy products consumption was inversely associated with deaths from cancers (pooled relative risk 0.88, 95% CI 0.79 to 0.99; P=0.03; I2=47.1%, 95% CI 0.0% to 75.4%) and cardiovascular diseases (pooled effect size: 0.85, 95% CI 0.72 to 0.99; P=0.04; I2=50.0%, 95% CI 0.0% to 77.6%). Such significant associations were also observed for all-cause mortality in some subgroups of the included studies, particularly those with higher quality. In addition, higher intake of soy was associated with decreased risk of mortality from gastric, colorectal, and lung cancers as well as ischemic cardiovascular diseases. Participants in the highest category of dietary soy isoflavones intake had a 10% lower risk of all-cause mortality compared with those in the lowest category. We also found that a 10-mg/day increase in intake of soy isoflavones was associated with 7% and 9% decreased risk of mortality from all cancers and also breast cancer respectively. Furthermore, a 12% reduction in breast cancer death was indicated for each 5-g/day increase in consumption of soy protein. However, intake of soy protein was not significantly associated with all-cause and cardiovascular diseases mortality.ConclusionsSoy and its isoflavones may favorably influence risk of mortality. In addition, soy protein intake was associated with a decreased risk in the mortality of breast cancer. Our findings may support the current recommendations to increase intake of soy for greater longevity.  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