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   5936篇
  免费   151篇
  国内免费   206篇
电工技术   137篇
综合类   40篇
化学工业   754篇
金属工艺   288篇
机械仪表   88篇
建筑科学   141篇
矿业工程   17篇
能源动力   94篇
轻工业   312篇
水利工程   15篇
石油天然气   331篇
武器工业   13篇
无线电   351篇
一般工业技术   616篇
冶金工业   2497篇
原子能技术   42篇
自动化技术   557篇
  2022年   47篇
  2021年   85篇
  2020年   44篇
  2019年   60篇
  2018年   86篇
  2017年   83篇
  2016年   86篇
  2015年   91篇
  2014年   118篇
  2013年   178篇
  2012年   181篇
  2011年   290篇
  2010年   245篇
  2009年   245篇
  2008年   253篇
  2007年   226篇
  2006年   272篇
  2005年   230篇
  2004年   238篇
  2003年   189篇
  2002年   235篇
  2001年   195篇
  2000年   155篇
  1999年   179篇
  1998年   181篇
  1997年   172篇
  1996年   119篇
  1995年   130篇
  1994年   137篇
  1993年   144篇
  1992年   97篇
  1991年   52篇
  1990年   98篇
  1989年   100篇
  1988年   72篇
  1987年   60篇
  1986年   66篇
  1985年   54篇
  1984年   51篇
  1983年   45篇
  1981年   56篇
  1979年   40篇
  1978年   35篇
  1977年   37篇
  1976年   32篇
  1975年   41篇
  1974年   34篇
  1971年   79篇
  1970年   41篇
  1968年   35篇
排序方式: 共有6293条查询结果,搜索用时 10 毫秒
1.
屈平 《世界电信》2004,17(8):3-5
量子密码技术被认为是绝对安全的加密技术。近年来,在美国、德国、日本和中国,相关研究都取得了明显进展。2004年6月,世界上第一个量子密码通信网络在美国马萨诸塞州剑桥城正式投入运行,标志着这一技术迈上了新台阶。据相关机构估算,量子保密通信系统一旦商用,将形成高达10亿美元的市场。  相似文献   
2.
Presents the 2002 Annual Report of the American Psychological Association. Directorate Reports, the President's Address, and Treasurer's Report are included. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
3.
Martha J. Farah.     
Recognizes Martha J. Farah for rigorous empirical and theoretical analysis of visual cognition, in which understanding of normal function and analysis of neurological deficits illuminate and strengthen one another. Applying diverse experimental techniques within an integrated approach to the study of mind and brain, she has sharpened and helped to answer fundamental questions about how humans generate and manipulate visual images, recognize objects, and attend to positions in space. Along with a citation, a biography is presented for Farah, as well as a bibliography of her works. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
4.
Lists the officers, boards, committees, and representatives of the American Psychological Association (APA) for 1993, including members of the Council of Representatives and their terms of office as well as APA-affiliated regional, state, provincial, and territorial psychological associations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
5.
Acknowledges and thanks a list of American Psychological Association members who contributed to the work of the Committee on Accreditation by serving on site visiting teams and participating in other accreditation activities during the 1994–1995 academic/training year. (0 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
6.
7.
Addressing the still open question of the prebiotic origin of sequential macromolecules (peptides, nucleic acids) on the primitive Earth, we describe a molecular engine (the primary pump), which works at ambient temperature and continuously generates, elongates and complexifies sequential peptides. This new scenario is based on a cyclic reaction sequence, whose keystep is the activation of amino acids into their N‐carboxyanhydrides (NCA) through nitrosation by NOx. This process could have taken place on tidal beaches; it requires a buffered ocean, emerged land and a nitrosating atmosphere. With the help of geochemical studies and computer simulations of atmosphere photochemistry, we show that the primitive Earth during the Hadean may have satisfied all these requirements. © 2001 Society of Chemical Industry.  相似文献   
8.
Provides the biography of Dante Cicchetti and announces that he has received the APA Award for Distinguished Senior Career Contributions to Psychology in the Public Interest (2004) for his seminal role in bridging theory, research, and practice by fostering the emergence and coalescence of the field of developmental psychopathology. A selected bibliography is also provided. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
9.
An optical nondestructive strain measurement technique was performed to analyze the mechanical deformation induced by an electrical field within the insulating materials. Poly(ethylene naphthalene 2,6‐dicarboxylate) (PEN) films were then subjected to constant electrical fields right up to their electrical breakdown. The experimental technique made it possible to follow the various stages of the mechanical behavior of PEN in real time. The final breakdown occurred in the observation zone and the related mechanical deformation was captured. A “margarita” structure was observed with a hole at the center. The experimental results indicated that the level of the induced‐mechanical deformations depended on the local environment. We defined two different zones representing the inside and the outside of the damaged area. The induced‐deformations were larger in the damaged zone. It was also observed that deformations increased when the sample had a lower degree of crystallinity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   
10.
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