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   6128篇
  免费   441篇
  国内免费   3篇
电工技术   78篇
综合类   5篇
化学工业   1603篇
金属工艺   87篇
机械仪表   163篇
建筑科学   216篇
矿业工程   24篇
能源动力   233篇
轻工业   1288篇
水利工程   40篇
石油天然气   24篇
无线电   286篇
一般工业技术   948篇
冶金工业   227篇
原子能技术   29篇
自动化技术   1321篇
  2024年   22篇
  2023年   68篇
  2022年   266篇
  2021年   312篇
  2020年   199篇
  2019年   238篇
  2018年   289篇
  2017年   271篇
  2016年   271篇
  2015年   246篇
  2014年   290篇
  2013年   586篇
  2012年   455篇
  2011年   521篇
  2010年   409篇
  2009年   350篇
  2008年   327篇
  2007年   246篇
  2006年   195篇
  2005年   163篇
  2004年   117篇
  2003年   109篇
  2002年   111篇
  2001年   47篇
  2000年   45篇
  1999年   42篇
  1998年   55篇
  1997年   41篇
  1996年   27篇
  1995年   48篇
  1994年   18篇
  1993年   18篇
  1992年   13篇
  1991年   17篇
  1990年   13篇
  1989年   14篇
  1988年   9篇
  1987年   7篇
  1986年   5篇
  1985年   8篇
  1984年   11篇
  1983年   9篇
  1982年   4篇
  1981年   5篇
  1980年   4篇
  1979年   8篇
  1978年   5篇
  1977年   5篇
  1976年   5篇
  1975年   9篇
排序方式: 共有6572条查询结果,搜索用时 15 毫秒
1.
2.
Software and Systems Modeling - Many model transformation scenarios require flexible execution strategies as they should produce models with the highest possible quality. At the same time,...  相似文献   
3.
Food Science and Biotechnology - The enzymatic activity and partial characterization of proteases from Bromelia karatas fruits were evaluated and compared with Bromelia pinguin proteases. The...  相似文献   
4.
This paper discusses the convenience of using two-dimensional (2-D) coding techniques for the compression of electrocardiogram (ECG) signals. These signals present a very clear periodicity that can be exploited by the use of a 2-D time/frequency transform to decorrelate it as much as possible. A brief theoretical approach is given to justify the use of this technique, and a comparison is made between a 2-D and a one-dimensional (1-D) uniform quantization scenarios. The influence of the error as well as the frame size on the estimation of the fundamental period is studied.  相似文献   
5.
Studied how 26 senior managers and 47 senior professional technical staff (recently repatriated) of 4 US owned multinational organizations viewed their international posting, specifically with respect to career path satisfaction. Results of satisfaction scales indicate that many Ss felt under-prepared for their international assignment. It is suggested that a comprehensive international employee development program should assess, provide feedback, and coach individuals on career path, culture shock and adjustment, and performance issues prior, during, and on return from the expatriate assignment. Results suggest that opportunities exist for individual and organizational intervention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
6.
7.
Atmospheric corrosion of reference metals in Antarctic sites   总被引:1,自引:0,他引:1  
This paper presents the results obtained at three Antarctic test sites participating in the “Ibero-American Map of Atmospheric Corrosiveness” (MICAT), a project on atmospheric corrosion carried out during the period 1988–1994 at some 70 sites distributed across 12 countries of the Latin-American region, Spain and Portugal. The three Antarctic sites are located near the coastline.The singular climatic characteristics of Antarctic regions are related with the purity of the air, the absence of rainfall and the formation of ice on the metallic surface during an important part of the exposure time. However, electrochemical activity is possible below ice layers. This situation affects the structure and morphology of corrosion product films and the resulting corrosion rates of metallic surfaces.  相似文献   
8.
BACKGROUND: Simultaneous removal of sulfur, nitrogen and carbon compounds from wastewaters is a commercially important biological process. The objective was to evaluate the influence of the CH3COO?/NO3? molar ratio on the sulfide oxidation process using an inverse fluidized bed reactor (IFBR). RESULTS: Three molar ratios of CH3COO?/NO3? (0.85, 0.72 and 0.62) with a constant S2?/NO3? molar ratio of 0.13 were evaluated. At a CH3COO?/NO3? molar ratio of 0.85, the nitrate, acetate and sulfide removal efficiencies were approximately 100%. The N2 yield (g N2 g?1 NO3?‐N consumed) was 0.81. Acetate was mineralized, resulting in a yield of 0.65 g inorganic‐C g?1 CH3COO?‐C consumed. Sulfide was partially oxidized to S0, and 71% of the S2? consumed was recovered as elemental sulfur by a settler installed in the IFBR. At a CH3COO?/NO3? molar ratio of 0.72, the efficiencies of nitrate, acetate and sulfide consumption were of 100%, with N2 and inorganic‐C yields of 0.84 and 0.69, respectively. The sulfide was recovered as sulfate instead of S0, with a yield of 0.92 g SO42?‐S g?1 S2? consumed. CONCLUSIONS: The CH3COO?/NO3? molar ratio was shown to be an important parameter that can be used to control the fate of sulfide oxidation to either S0 or sulfate. In this study, the potential of denitrification for the simultaneous removal of organic matter, sulfide and nitrate from wastewaters was demonstrated, obtaining CO2, S0 and N2 as the major end products. Copyright © 2008 Society of Chemical Industry  相似文献   
9.
10.
Abstract: Environmental justice advocates have recently focused attention on cumulative exposure in minority neighborhoods due to multiple sources of pollution. This article uses U.S. EPA's National Air Toxics Assessment (NATA) for 1996 to examine environmental inequality in California, a state that has been a recent innovator in environmental justice policy. We first estimate potential lifetime cancer risks from mobile and stationary sources. We then consider the distribution of these risks using both simple comparisons and a multivariate model in which we control for income, land use, and other explanatory factors, as well as spatial correlation. We find large racial disparities in California's “riskscape” as well as inequalities by other factors and suggest several implications for environmental and land use policy.  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