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   714篇
  免费   61篇
  国内免费   208篇
  2024年   2篇
  2023年   52篇
  2022年   46篇
  2021年   62篇
  2020年   37篇
  2019年   33篇
  2018年   24篇
  2017年   17篇
  2016年   26篇
  2015年   43篇
  2014年   53篇
  2013年   40篇
  2012年   50篇
  2011年   47篇
  2010年   37篇
  2009年   38篇
  2008年   29篇
  2007年   46篇
  2006年   45篇
  2005年   34篇
  2004年   23篇
  2003年   22篇
  2002年   39篇
  2001年   19篇
  2000年   12篇
  1999年   12篇
  1998年   11篇
  1997年   7篇
  1996年   13篇
  1995年   6篇
  1994年   7篇
  1993年   7篇
  1992年   9篇
  1991年   6篇
  1990年   6篇
  1989年   3篇
  1988年   3篇
  1987年   1篇
  1985年   4篇
  1984年   4篇
  1983年   4篇
  1982年   1篇
  1981年   2篇
  1974年   1篇
排序方式: 共有983条查询结果,搜索用时 281 毫秒
41.
42.

Purpose

To compare the outcomes of femtosecond laser-assisted cataract surgery (FLACS) with those of conventional phacoemulsification surgery (CPS) for age-related cataracts.

Methods

A comprehensive literature search of PubMed, EMBASE, and the Cochrane Controlled Trials Register was conducted to identify randomized controlled trials (RCT) and comparative cohort studies comparing FLACS with CPS. Endothelial cell loss percentage (ECL%), central corneal thickness (CCT), corrected and uncorrected distant visual acuity (CDVA and UDVA), and mean absolute error (MAE) of refraction were used as primary outcomes. Secondary outcomes included surgically induced astigmatism (SIA), mean effective phacoemulsification time (EPT), phacoemulsification power and circularity of the capsulorhexis.

Results

Nine RCTs and fifteen cohort studies including 4,903 eyes (2,861 in the FLACS group and 2,072 in the CPS group) were identified. There were significant differences between the two groups in ECL% at one week, about one month and three months postoperatively, in CCT at one day, about one month postoperatively and at the final follow-up, in CDVA at one week postoperatively, and in UDVA at the final follow-up. Significant differences were also observed in MAE, EPT, phacoemulsification power, and the circularity of capsulorhexis. However, no significant differences were observed in CDVA at one week postoperatively or in surgically induced astigmatism.

Conclusions

Compared to CPS, FLACS is a safer and more effective method for reducing endothelial cell loss and postoperative central corneal thickening as well as achieving better and faster visual rehabilitation and refractive outcomes. However, there is no difference in final CDVA and surgically induced astigmatism between the two groups.  相似文献   
43.
44.
45.
46.
景观感知作为自然教育非常重要的组成部分,其研究内容受到广泛关注,但现有研究仍处于初步阶段,未对自然教育环境设计起到应有的支撑作用。从景观感知角度,综合环境教育学、环境心理学及行为心理学等相关理论,对基于景观感知的自然教育环境的营建提出了针对性原则及策略,并着重探讨影响景观感知的设计要素。首次从景观感知角度对自然教育环境设计进行探讨,对自然教育环境的营建具有指导意义。 关键词:风景园林;自然教育;景观感知  相似文献   
47.
Bromodomain-containing protein 4 (BRD4) is a new therapeutic target for the treatment of diseases including cardiovascular diseases, cancer, inflammation and central nervous system (CNS) disorders. In this study, we introduced the pharmacophore of fibrates to a BRD4 inhibitor, RVX-208, to design dual-active hypolipidemic compounds, and found that some of new analogues showed favorable hypolipidemic activities. Synthetic accessibility towards this class of compounds optimized RVX-208 as well as would supply more thoughts on hypolipidemic drugs.  相似文献   
48.
In this study, the effects of carbon source, nitrogen source, and metal ions on cell growth and Bacillus aryabhattai β-amylase production in recombinant Brevibacillus choshinensis were investigated. The optimal medium for β-amylase production, containing glucose (7.5?g·L?1), pig bone peptone (40.0?g·L?1), Mg2+ (0.05?mol·L?1), and trace metal elements, was determined through single-factor experiments in shake flasks. When cultured in the optimized medium, the β-amylase yield reached 925.4?U mL?1, which was 7.2-fold higher than that obtained in the initial medium. Besides, a modified feeding strategy was proposed and applied in a 3-L fermentor fed with glucose, which achieved a dry cell weight of 15.4?g L?1. Through this cultivation approached 30?°C with 0?g·L?1 initial glucose concentration, the maximum β-amylase activity reached 5371.8?U mL?1, which was 41.7-fold higher than that obtained with the initial medium in shake flask.  相似文献   
49.
50.
Interactions between plants and soil microbes can strongly influence plant diversity and community dynamics. Soil microbes may promote plant diversity by driving negative frequency‐dependent plant population dynamics, or may favor species exclusion by providing one species an average fitness advantage over others. However, past empirical research has focused overwhelmingly on the consequences of frequency‐dependent feedbacks for plant species coexistence and has generally neglected the consequences of microbially mediated average fitness differences. Here we use theory to develop metrics that quantify microbially mediated plant fitness differences, and show that accounting for these effects can profoundly change our understanding of how microbes influence plant diversity. We show that soil microbes can generate fitness differences that favour plant species exclusion when they disproportionately harm (or favour) one plant species over another, but these fitness differences may also favor coexistence if they trade off with competition for other resources or generate intransitive dominance hierarchies among plants. We also show how the metrics we present can quantify microbially mediated fitness differences in empirical studies, and explore how microbial control over coexistence varies along productivity gradients. In all, our analysis provides a more complete theoretical foundation for understanding how plant–microbe interactions influence plant diversity.  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