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   5095篇
  免费   11篇
电工技术   10篇
化学工业   272篇
金属工艺   2篇
机械仪表   23篇
建筑科学   6篇
矿业工程   2篇
能源动力   9篇
轻工业   461篇
水利工程   2篇
石油天然气   1篇
无线电   33篇
一般工业技术   74篇
冶金工业   4171篇
原子能技术   8篇
自动化技术   32篇
  2022年   10篇
  2021年   11篇
  2020年   10篇
  2017年   12篇
  2016年   16篇
  2015年   10篇
  2014年   10篇
  2013年   79篇
  2012年   15篇
  2011年   19篇
  2010年   18篇
  2008年   11篇
  2007年   16篇
  2006年   13篇
  2004年   11篇
  2003年   14篇
  1999年   121篇
  1998年   1240篇
  1997年   700篇
  1996年   471篇
  1995年   267篇
  1994年   256篇
  1993年   271篇
  1992年   46篇
  1991年   81篇
  1990年   57篇
  1989年   88篇
  1988年   84篇
  1987年   84篇
  1986年   71篇
  1985年   41篇
  1984年   16篇
  1983年   21篇
  1982年   33篇
  1981年   41篇
  1980年   58篇
  1979年   19篇
  1978年   41篇
  1977年   134篇
  1976年   297篇
  1975年   34篇
  1974年   20篇
  1973年   18篇
  1972年   23篇
  1971年   21篇
  1970年   18篇
  1969年   9篇
  1967年   10篇
  1966年   10篇
  1965年   14篇
排序方式: 共有5106条查询结果,搜索用时 31 毫秒
71.
72.
73.
74.
75.
76.
77.
Northern Plains Indians (N = 200) completed the Indian Specific Health Risk Appraisal and measures assessing beliefs about risk factors and personal risk. Participants rated personal risk optimistically, judged their risk factor standing as superior to that of their peers, and neglected to consider risk factor standing when appraising personal risk. Moreover, participants were often not improving their standing on risk factors they considered relevant to their health. Such biases in health beliefs may prevent health interventions from being successful.  相似文献   
78.
An agile manufacturing workcell design   总被引:1,自引:0,他引:1  
This paper introduces a design for agile manufacturing worked Is intended for light mechanical assembly of products made from similar components (i.e., parts families). We define agile manufacturing as the ability to accomplish rapid changeover from the assembly of one product to the assembly of a different product. Rapid hardware changeover is made possible through the use of robots, flexible part feeders, modular grippers, and modular assembly hardware. The division of assembly, feeding, and unloading tasks between multiple robots is examined with prioritization based upon assembly time. Rapid software changeover will be facilitated by the use of a real-time, object-oriented software environment utilizing graphical simulations for off-line software development. An innovative dual VMEbus controller architecture permits an open software environment while accommodating the closed nature of most commercial robot controllers. These agile features permit new products to be introduced with minimal downtime and system reconfiguration.  相似文献   
79.
80.
OBJECTIVE: To determine the risk of developing high grade anal squamous intraepithelial neoplasia (HG-AIN) in relation to HIV infection and immunosuppression, after controlling for the effects of human papillomavirus (HPV) infection. DESIGN: Prospective cohort study of 158 HIV-seropositive and 147 HIV-seronegative homosexual men presenting to a community-based clinic with initially negative anal cytologic and colposcopic findings. METHODS: Subjects completed self-administered questionnaires, underwent cytologic screening, and standardized unaided and colposcopic examination of the proximal anal canal for presence of abnormalities suggestive of AIN. Anal specimens were screened for HPV DNA. RESULTS: HG-AIN developed in eight (5.4%) and 24 (15.2%) HIV-seronegative and -seropositive men, respectively. Risk of HG-AIN among HIV-seronegative men was associated with detection of anal HPV types 16 or 18 by Southern transfer hybridization (STH), detection of HPV 16 or 18 at the lower levels by polymerase chain reaction but not by STH, and with number of positive HPV tests; HG-AIN risk among HIV-seropositive men was associated with detection of HPV 16 or 18 only by STH, detection of HPV types other than 16 or 18, CD4 count < or = 500 x 10(6)/l, and number of positive HPV tests. HIV-induced immunosuppression remained an independent predictor of HG-AIN after adjusting for type and level of detection of HPV; HIV infection predicted HG-AIN risk after adjustment for number of positive HPV tests. CONCLUSIONS: The association of HG-AIN with HIV, independent of HPV type, level of HPV detection and number of positive HPV tests, suggests that this increased risk cannot be entirely explained by an effect of HIV on HPV detection. Future studies focusing on factors more specific to the local microenvironment in the anal canal should help clarify these issues.  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