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   87701篇
  免费   1100篇
  国内免费   408篇
电工技术   806篇
综合类   2322篇
化学工业   12302篇
金属工艺   4822篇
机械仪表   3084篇
建筑科学   2494篇
矿业工程   574篇
能源动力   1223篇
轻工业   4021篇
水利工程   1315篇
石油天然气   352篇
武器工业   1篇
无线电   9479篇
一般工业技术   16908篇
冶金工业   3162篇
原子能技术   270篇
自动化技术   26074篇
  2022年   45篇
  2021年   67篇
  2020年   58篇
  2019年   81篇
  2018年   14522篇
  2017年   13446篇
  2016年   10050篇
  2015年   671篇
  2014年   359篇
  2013年   490篇
  2012年   3311篇
  2011年   9651篇
  2010年   8450篇
  2009年   5736篇
  2008年   6959篇
  2007年   7973篇
  2006年   282篇
  2005年   1372篇
  2004年   1245篇
  2003年   1271篇
  2002年   648篇
  2001年   157篇
  2000年   249篇
  1999年   137篇
  1998年   148篇
  1997年   105篇
  1996年   132篇
  1995年   66篇
  1994年   65篇
  1993年   62篇
  1992年   58篇
  1991年   58篇
  1989年   43篇
  1988年   41篇
  1987年   37篇
  1986年   38篇
  1985年   39篇
  1984年   54篇
  1983年   48篇
  1982年   41篇
  1981年   36篇
  1980年   36篇
  1968年   45篇
  1966年   45篇
  1965年   44篇
  1959年   35篇
  1958年   37篇
  1957年   36篇
  1955年   63篇
  1954年   68篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
101.
The aim of this paper is to propose new organizational factors that might explain the differences in the extent and the speed of IT adoption. With this in mind, we carried out an analysis of 16 cases in the pharmaceutical distribution sector in Spain. The results indicate that there are certain intangible assets that favour the introduction and development of IT. Among these are a frank and fluid communication between departments and members of the organization, low levels of conflict, the explicit support of top management towards IT adoption and learning and creative skills of IT-staff. In addition to these factors, we found others that we propose as catalysts of IT adoption. Among these we might mention the special relationship between the member-clients and the company in the case of cooperative firms.  相似文献   
102.
103.
104.
Khartoum     
Ian Haywood 《Cities》1985,2(3):186-197
Khartoum is the capital of a country whose creation resulted more from colonial politicians' desires for straight boundaries than from local social or political realities. This profile traces Khartoum's history of growth and planning legislation since its establishment as an administrative capital at the turn of the century. The city, developed from three separate towns, grew rapidly after independence as administrative functions grew and industrial development started. However, lack of an effective mechanism for planning and control of the city's growth has meant that a pattern of sprawling low-density land uses has developed, with inadequate services and deteriorating environmental standards. What planning control does exist operates through land-use zoning and building byelaws, though often arbitrarily applied. Planning problems are exacerbated by high population growth rates and national economic problems.  相似文献   
105.
In a prospective study of adolescent depression, adolescents (N?=?1,508) were assessed at Time 1 and after 1 yr (Time 2) on psychosocial variables hypothesized to be associated with depression. Most psychosocial variables were associated with current (n?=?45) depression. Formerly depressed adolescents (n?=?217) continued to differ from never depressed controls on many of the psychosocial variables. Many of the depression-related measures also acted as risk factors for future depression (n?=?112), especially past depression, current other mental disorders, past suicide attempt, internalizing behavior problems, and physical symptoms. Young women were more likely to be, to become, and to have been depressed. Controlling for the psychosocial variables eliminated the gender difference for current and future but not for past depression. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
106.
A trade-off analysis on the cost and system packaging metrics of an electronic product aimed at the commercial/retail industry has been carried out. By comparing the system cost and packaging metrics with those of comparable consumer products, we have determined that there is opportunity for significant cost, size, and weight reduction of the overall electronics packaging system. These include the use of fine pitch IC packages, smaller discrete components, denser PCB wiring technology, double sided IC package surface mount, surface mount connectors, and improved plastics for the product housing. The analysis concluded that PCB area reduction of 40%, using a single PCB instead of three boards, reduction in board cost of over 50% and product weight reduction of over 28% are possible using available technologies.  相似文献   
107.
A high performance liquid chromatography method is described for the determination of diclofenac sodium, its related compounds and degradation products in commercial sources of raw materials and solid dosage forms. This method is specific, accurate and stability indicating. The method employs a reverse-phase octylsilane (C18) column with a mobile phase composed of acetonitrile/methanol/pic B-6 (25:25:50) and detection at 229 nm. The method resolves six principal related compounds with quantitation in the range 0.3-1.5%. Assay recoveries by spiking commercial formulations with diclofenac sodium were 99.64 ± 1.30%. Drug content in several commercial formulations are reported. Accelerated stability tests were conducted on raw materials and drug products and 1-(2,6-dichlorophenyl)-2-indolin-2-one was identified for the first time as a degradation product in solid dosage forms which are stressed under humidity and heat.  相似文献   
108.
Discusses controversies surrounding the work of B. F. Skinner's influence on various theories of human and animal behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
109.
110.
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