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   10249篇
  免费   583篇
  国内免费   32篇
  2024年   16篇
  2023年   105篇
  2022年   318篇
  2021年   542篇
  2020年   330篇
  2019年   421篇
  2018年   452篇
  2017年   327篇
  2016年   468篇
  2015年   530篇
  2014年   633篇
  2013年   797篇
  2012年   844篇
  2011年   726篇
  2010年   440篇
  2009年   354篇
  2008年   443篇
  2007年   443篇
  2006年   389篇
  2005年   384篇
  2004年   298篇
  2003年   252篇
  2002年   227篇
  2001年   110篇
  2000年   98篇
  1999年   80篇
  1998年   60篇
  1997年   31篇
  1996年   36篇
  1995年   41篇
  1994年   26篇
  1993年   28篇
  1992年   47篇
  1991年   42篇
  1990年   46篇
  1989年   42篇
  1988年   44篇
  1987年   33篇
  1986年   30篇
  1985年   37篇
  1984年   33篇
  1983年   27篇
  1982年   21篇
  1981年   26篇
  1980年   13篇
  1979年   16篇
  1978年   19篇
  1977年   14篇
  1976年   22篇
  1975年   17篇
排序方式: 共有10000条查询结果,搜索用时 153 毫秒
901.
902.
903.
904.
905.
906.
907.
This study was conducted to identify environmental and human health risks caused by Balarood Dam, in construction phrase. The first step, all risk-generating factors were identified using a Delphi Questionnaire. Afterwards, the identified criteria were prioritized once using the Analytical Hierarchy Process (AHP) method and then by the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). Due to the complex and uncertain nature of decision-making in times of risk, it was necessary to use more than one weighting method to ensure accuracy of weights. The results from AHP and TOPSIS revealed a mismatch in priorities; therefore, an integration method was presented blending Mean-Rank, Borda, and Copeland methods. According to the TOPSIS results, factors including cut and fill, explosion, and transportation, were first to third highest-priority risk-generating factors, respectively. Considering the results from the AHP method, factors cut and fill, drilling, and explosion were identified as first to third top-priority risk-generating factors, respectively. The results obtained from the integration method suggested that cut and fill, explosion, and drilling are the most important environmental risks at construction phase. As a general conclusion, different weighting methods can lead to different results by which the fate of a decision may be changed and it is essential to control final scores by applying more than one weighting method.  相似文献   
908.
We investigated the protective effect of caffeic acid phenethyl ester (CAPE) on cyclophosphamide‐induced hemorrhagic cystitis in rats in comparison with 2‐mercaptoethane sulfonate (MESNA). Forty male rats were randomized into four groups: group 1 (control), group 2 (cyclophosphamide), group 3 (cyclophosphamide + MESNA), group 4 (cyclophosphamide + CAPE). Cyclophosphamide injection increased malondialdehyde levels indicating oxidative stress, whereas CAPE and MESNA ameliorated malondialdehyde levels in the bladder (p < 0.05). Only catalase activities were decreased significantly in both groups (cyclophosphamide + MESNA and cyclophosphamide + CAPE, p < 0.05). Pretreatment with CAPE (p < 0.01) resulted in a significant decrease in nitric oxide levels when compared with the cyclophosphamide group. When we consider the studies that show the critical importance of increased nitric oxide levels in pathogenesis of cyclophosphamide‐induced hemorrhagic cystitis, we suggest that it would be more beneficial to use MESNA with CAPE to prevent histological damage.  相似文献   
909.
910.
To date, six candidate genera of anaerobic ammonium‐oxidizing (anammox) bacteria have been identified, and numerous studies have been conducted to understand their ecophysiology. In this study, we examined the physiological characteristics of an anammox bacterium in the genus ‘Candidatus Jettenia’. Planctomycete KSU‐1 was found to be a mesophilic (20–42.5°C) and neutrophilic (pH 6.5–8.5) bacterium with a maximum growth rate of 0.0020 h?1. Planctomycete KSU‐1 cells showed typical physiological and structural features of anammox bacteria; i.e. 29N2 gas production by coupling of 15NH4+ and 14NO2?, accumulation of hydrazine with the consumption of hydroxylamine and the presence of anammoxosome. In addition, the cells were capable of respiratory ammonification with oxidation of acetate. Notably, the cells contained menaquinone‐7 as a dominant respiratory quinone. Proteomic analysis was performed to examine underlying core metabolisms, and high expressions of hydrazine synthase, hydrazine dehydrogenase, hydroxylamine dehydrogenase, nitrite/nitrate oxidoreductase and carbon monoxide dehydrogenase/acetyl‐CoA synthase were detected. These proteins require iron or copper as a metal cofactor, and both were dominant in planctomycete KSU‐1 cells. On the basis of these experimental results, we proposed the name ‘Ca. Jettenia caeni’ sp. nov. for the bacterial clade of the planctomycete KSU‐1.  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