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   27170篇
  免费   782篇
  国内免费   32篇
电工技术   333篇
综合类   13篇
化学工业   5972篇
金属工艺   530篇
机械仪表   467篇
建筑科学   1181篇
矿业工程   333篇
能源动力   654篇
轻工业   1740篇
水利工程   227篇
石油天然气   245篇
无线电   1744篇
一般工业技术   4170篇
冶金工业   6355篇
原子能技术   270篇
自动化技术   3750篇
  2022年   192篇
  2021年   417篇
  2020年   269篇
  2019年   356篇
  2018年   426篇
  2017年   372篇
  2016年   496篇
  2015年   396篇
  2014年   625篇
  2013年   1673篇
  2012年   950篇
  2011年   1216篇
  2010年   933篇
  2009年   986篇
  2008年   1165篇
  2007年   1073篇
  2006年   985篇
  2005年   893篇
  2004年   755篇
  2003年   720篇
  2002年   716篇
  2001年   491篇
  2000年   400篇
  1999年   470篇
  1998年   495篇
  1997年   464篇
  1996年   507篇
  1995年   462篇
  1994年   467篇
  1993年   446篇
  1992年   440篇
  1991年   281篇
  1990年   417篇
  1989年   399篇
  1988年   342篇
  1987年   411篇
  1986年   356篇
  1985年   445篇
  1984年   467篇
  1983年   402篇
  1982年   379篇
  1981年   303篇
  1980年   305篇
  1979年   363篇
  1978年   305篇
  1977年   243篇
  1976年   230篇
  1975年   247篇
  1974年   218篇
  1973年   225篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Primer walking of cloned DNA is a standard research tool. It has been used in the past to determine the sequence of individual clones of interest. With the expansion of DNA sequencing capacity the need to be able to walk larger numbers of clones has become necessary. Our laboratory is a mid-sized genomics facility. In conjunction with the Advanced Biomedical Computing Center (ABCC) we have developed methods for automating the primer selection, DNA sequencing, contig assembly and sequence analysis for clones arrayed in microtiter format. This approach has allowed us to walk 475 clones (five microtiter plates) selected from a cDNA library.  相似文献   
122.
Professional psychologists are increasingly likely to encounter opportunities to work with patients and families facing end-of-life issues. Psychologists can provide psychological assessment, intervention for patients and families, consultation with and support of health care team members, grief therapy, and program development and evaluation. Psychological services are useful for healthy individuals who wish to make thoughtful plans about their own future care, patients with life-limiting illnesses, families stressed by providing end-of-life care, bereaved individuals, and health care providers who face issues of burnout and strain. Several challenges for psychologists working in end-of-life care are noted, including training, development of clear roles, and reimbursement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
123.
Defends the practice of modifying reprints of journal articles to amend typographical and other errors that can affect meaning. A standard should be developed for dealing with such errors by hand writing corrections, including a list of errata, or issuing professionally corrected reprints with the notation that corrections have been made. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
124.
Almond preferences were produced by giving rats a mixture of almond and sucrose (Experiments 1-4) or saccharin (Experiment 4). A subsequent extinction procedure consisted of either repeated 2-bottle almond versus water tests (Experiment 1) or repeated exposure to almond alone (Experiments 2-4). The main independent variable was whether access to food following a session was given immediately, 30 min later, or 120 min later. No effect of extinction was found in any experiment. An important finding was that varying the delay until food access had no detectable effect. It was concluded that inadvertent flavor-food associations do not maintain preference for the flavor under extinction conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
125.
We cross-sectionally examined the relationship between age, optic disc area, refraction, and gender and optic disc topography and retinal nerve fiber layer (RNFL) measurements, using optical imaging techniques. One eye from each of 155 Caucasian subjects (age range 23.0-80.8 y) without ocular pathology was included. Measurements were obtained by using the Heidelberg Retina Tomography (HRT), the GDx Nerve Fiber Analyzer, and the Optical Coherence Tomograph (OCT). The effects of age were small (R2 < 17%) and were limited to specific HRT, GDx, and OCT parameters. Disc area was significantly associated with most HRT parameters and isolated GDx and OCT parameters. Refraction and gender were not significantly associated with any optic disc or RNFL parameters. Although effects of age on the optic disc and RNFL are small, they should be considered in monitoring ocular disease. Optic disc area should be considered when cross-sectionally evaluating disc topography and, to a lesser extent, RNFL thickness.  相似文献   
126.
This paper gives an account of ‘left’ and ‘progressive’ economic development politics and policy in Sheffield and Chicago in the early 1980s. The origins of these policies in activist work and grassroots organizing, and the leadership of John Benington and David Blunkett in Sheffield and of Robert Mier and Harold Washington in Chicago are characterized and briefly compared.  相似文献   
127.
128.
The Republicans took control of both houses of Congress in November of 1994 for the 1st time in 42 yrs. Although the magnitude of the Clinton Administration's proposed Health Security Act may well have triggered fears of overcontrol, it is clear that the delivery of psychological care will be changed dramatically by the combined forces of federal and state health reform. R. J. Resnick, President of the American Psychological Association, has appointed the Task Force on Education and Training for Work in Organized Delivery Systems to look at how psychological health care is provided in the new and evolving systems, and to examine how current training programs prepare new psychologists to practice in and around organized health care systems. Dr. Resnick is similarly concerned about standardization of training, training in nontraditional areas of competence, and increased federal recognition and funding of training in psychology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
129.
130.
The effects of celebrity self-disclosure of HIV seropositivity on perceptions of HIV and AIDS were investigated. AIDS-related interest and knowledge measures were collected from 468 men before and after basketball star Earvin "Magic" Johnson's self-disclosure of HIV seropositivity. Increased interest in AIDS paralleled media coverage of the announcement, with the most substantial effects occurring within 2 wks. Perceived impact of the disclosure was greatest among African-American men and men who had not previously known someone with HIV/AIDS. Celebrity self-disclosure appears to affect perceptions through mechanisms similar to those involved in personally knowing someone infected with HIV. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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