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   2134篇
  免费   50篇
  国内免费   1篇
电工技术   28篇
综合类   3篇
化学工业   315篇
金属工艺   30篇
机械仪表   44篇
建筑科学   82篇
矿业工程   8篇
能源动力   33篇
轻工业   183篇
水利工程   10篇
石油天然气   2篇
无线电   266篇
一般工业技术   300篇
冶金工业   657篇
原子能技术   20篇
自动化技术   204篇
  2023年   18篇
  2022年   24篇
  2021年   39篇
  2020年   21篇
  2019年   26篇
  2018年   30篇
  2017年   31篇
  2016年   44篇
  2015年   38篇
  2014年   39篇
  2013年   84篇
  2012年   64篇
  2011年   86篇
  2010年   71篇
  2009年   69篇
  2008年   78篇
  2007年   71篇
  2006年   56篇
  2005年   69篇
  2004年   31篇
  2003年   28篇
  2002年   44篇
  2001年   41篇
  2000年   27篇
  1999年   45篇
  1998年   157篇
  1997年   106篇
  1996年   79篇
  1995年   52篇
  1994年   46篇
  1993年   44篇
  1992年   28篇
  1991年   31篇
  1990年   36篇
  1989年   37篇
  1988年   26篇
  1987年   22篇
  1986年   20篇
  1985年   19篇
  1984年   14篇
  1983年   17篇
  1982年   13篇
  1981年   17篇
  1980年   12篇
  1979年   17篇
  1978年   21篇
  1977年   14篇
  1976年   26篇
  1971年   19篇
  1970年   14篇
排序方式: 共有2185条查询结果,搜索用时 15 毫秒
51.
Life-cycle inventories were compiled to characterize natural resource requirements and environmental emissions associated with the sourcing and production of selected, detergent-grade surfactants and surfactant feedstocks. Petrochemical surfactant types examined were linear alkylbenzene sulfonate, alcohol sulfate (AS), alcohol ethoxylate (AE) and alcohol ethoxylate sulfate (AES). Oleochemical surfactants derived from palm oil, palm kernel oil and inedible tallow were AS, AE, AES and (for palm oil and tallow) methyl ester sulfonate. It was determined that natural resource requirements were primarily related to the source of feedstock and secondarily to surfactant type. Likewise, the composition and mass of atmospheric, aqueous and solid emissions were principally determined by feedstock source. Energy requirements varied as a function of both feedstock and surfactant type. The inventories do not support fundamental shifts in surfactant usage or feedstock sourcing on the basis of environmental concerns, as no single surfactant or feedstock was identified as superior across all resource and emissions criteria examined. The data provide baselines for evaluating opportunities for resource optimization, pollution prevention and waste minimization within each production technology surveyed.  相似文献   
52.
Results obtained with the commercial test-set "GOD-UV" (Dr. Haury, München) are reported. This method permits the determination of serum-glucose within 3 minutes. The procedure is satisfactory in normal and hyperglycaemic patients. In the hypoglycaemic state, however, there is a danger of misinterpretation. The glucose oxidase-UV is compared with the hexokinase reaction.  相似文献   
53.
Questions are often raised regarding the effectiveness and value of treatment programs for children and families. Recently, programs have been increasingly held accountable for services offered. In response, the member agencies of IARCCA have developed a comprehensive outcome measurement program. This article describes the project, focusing on the conditions that led to its inception and how the measurement plan was developed. In addition, the article includes information on the selection of personnel, measurement instruments, and methods and on the process of data collection. Summary results are provided, including how these results are utilized to improve services. Finally, the continued expansion and future directions of the Outcome Project are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
54.
Using methodological extensions to adapt extreme programming (XP) for major projects offers a high security and reliability without limiting software development's advantages. The authors describe their use of XP extensions that focus on development's planning and controlling aspects, demonstrating that a suitably adapted agile development process is applicable to long-term, large-system projects.  相似文献   
55.
This paper describes the results of a microscopic treatment of carrier-carrier scattering effects in the optical gain and refractive index spectra of a quantum-well semiconductor laser structure. The approach uses the Semiconductor Maxwell Bloch equations to describe the interaction between the carriers and the laser field, in the presence of many-body Coulomb interactions. Coulomb correlation effects are treated at the level of quantum kinetic theory in the Markovian limit. This approach shows the presence of nondiagonal Coulomb correlation contributions, in addition to the familiar diagonal contributions giving rise to polarization dephasing  相似文献   
56.
Design for six sigma through robust optimization   总被引:5,自引:1,他引:5  
The current push in industry is focused on ensuring not only that a product performs as desired but also that the product consistently performs as desired. To ensure consistency in product performance, “quality” is measured, improved, and controlled. Most quality initiatives have originated and been implemented in the product manufacturing stages. More recently, however, it has been observed that much of a product’s performance and quality is determined by early design decisions, by the design choices made early in the product design cycle. Consequently, quality pushes have made their way into the design cycle, and “design for quality” is the primary objective. How is this objective measured and met? The most recent quality philosophy, also originating in a manufacturing setting, is six sigma. The concepts of six sigma quality can be defined in an engineering design context through relation to the concepts of design reliability and robustness – probabilistic design approaches. Within this context, design quality is measured with respect to probability of constraint satisfaction and sensitivity of performance objectives, both of which can be related to a design “sigma level”. In this paper, we define six sigma in an engineering design context and present an implementation of design for six sigma – a robust optimization formulation that incorporates approaches from structural reliability and robust design with the concepts and philosophy of six sigma. This formulation is demonstrated using a complex automotive application: vehicle side impact crash simulation. Results presented illustrate the tradeoff between performance and quality when optimizing for six sigma reliability and robustness.  相似文献   
57.
58.
Measurement of cell volume in living epithelial cells has become an important technique in studies of membrane transport processes that function in cell volume regulation. Planimetry of video images of optical sections enables the measurement of the cross sectional area of each section. Cell volume is calculated from the measured area of each section and the known focus displacements. In the past the measurement of cross section area has been done by manual positioning of a cursor superimposed on the video image. Each experiment generates approximately 200 images in which two or more cells may be analysed. We have developed a computer-based method that uses one image as a template, and allows automated area determination of successive images by template matching and digital image processing. This new method is comparable to the older method in speed and accuracy, but requires much less effort from the experimenter.  相似文献   
59.
60.
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