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   15259篇
  免费   217篇
  国内免费   30篇
电工技术   192篇
综合类   8篇
化学工业   2028篇
金属工艺   369篇
机械仪表   342篇
建筑科学   528篇
矿业工程   63篇
能源动力   307篇
轻工业   1220篇
水利工程   90篇
石油天然气   118篇
无线电   1527篇
一般工业技术   2349篇
冶金工业   4779篇
原子能技术   160篇
自动化技术   1426篇
  2022年   85篇
  2021年   103篇
  2019年   103篇
  2018年   139篇
  2017年   111篇
  2016年   99篇
  2015年   108篇
  2014年   230篇
  2013年   585篇
  2012年   308篇
  2011年   426篇
  2010年   346篇
  2009年   344篇
  2008年   457篇
  2007年   448篇
  2006年   444篇
  2005年   389篇
  2004年   326篇
  2003年   364篇
  2002年   310篇
  2001年   328篇
  2000年   315篇
  1999年   387篇
  1998年   1332篇
  1997年   838篇
  1996年   603篇
  1995年   423篇
  1994年   379篇
  1993年   403篇
  1992年   277篇
  1991年   240篇
  1990年   260篇
  1989年   214篇
  1988年   218篇
  1987年   203篇
  1986年   196篇
  1985年   249篇
  1984年   208篇
  1983年   205篇
  1982年   200篇
  1981年   178篇
  1980年   191篇
  1979年   129篇
  1978年   136篇
  1977年   236篇
  1976年   316篇
  1975年   135篇
  1974年   125篇
  1973年   107篇
  1970年   83篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
11.
We study learning of predicate logics formulas from “elementary facts,” i.e. from the values of the predicates in the given model. Several models of learning are considered, but most of our attention is paid to learning with belief levels. We propose an axiom system which describes what we consider to be a human scientist's natural behavior when trying to explore these elementary facts. It is proved that no such system can be complete. However we believe that our axiom system is “practically” complete. Theorems presented in the paper in some sense confirm our hypothesis.  相似文献   
12.
13.
Cinematic primitives for multimedia   总被引:5,自引:0,他引:5  
The development of robust frameworks in interactive multimedia for representing story elements to the machine so that they can be retrieved in multiple contexts is addressed. Interactive multimedia is discussed as a user-directed form of storytelling, and the nature of cinematic storytelling is examined. It is proposed that content can be represented in layers. This model for layered information will allow programs to take advantage of the relation between cinematic sequences and the world they represent. The collection of content by the camera and microphone is considered in this context. The use of the methodology to build meaningful, context-rich sequences is discussed  相似文献   
14.
Hydroelectric generators of less than 20 kilowatts can be in remote areas served only by a single-phase line. For high efficiency and low cost, a three-phase induction generator should be used. This three-phase generator can operate with balanced voltages and currents when the ``phase-splitting' circuit uses two capacitors connetted to two different single-phase voltage sources.  相似文献   
15.
News section     
David Smith 《AI & Society》1991,5(4):360-361
  相似文献   
16.
Complex and highly distorted line drawings are produced by subjects attempting the Rey Complex Figure test, a clinical test of neuropsychological assessment. However, the marking scheme conventionally employed can be subjective and unreliable. In this paper, the first stages in automating this scoring system are investigated using a robust technique to locate a reduced set of scoring sections and a knowledge-based system that employs spatial metrics and fuzzy approximation techniques. Testing the technique using clinical data produced encouraging results that support the argument that this is a feasible approach for implementing a fully automated system, and that in its current state, can be immediately applied in a semi-automated system.  相似文献   
17.
Segmental colonic transit has been measured in 101 patients. Two MBq of 111Indium absorbed on resin pellets and encapsulated in an enteric coated capsule was given at 7 00 am. Hourly images during the first day, and three images during each subsequent day were acquired for up to three days. Using all scan and patient data the scans were categorised in one of the five patterns of colonic transit: normal, rapid, right delay, left delay, or generalised delay. The geometric centres and per cent activity at each time point was compared between the five groups of colonic transit patients to find the best time for imaging and so to distinguish the five groups. During the first day, early images did not help in diagnosis of patterns of transit, however, in the later images (six hours onwards after the ingestion of the activity) the rapid transit groups could be identified. Images at 27 and 51 hours were both required to distinguish all five groups of patients from each other. Only in the 'normal' transit patients was there some excretion of the activity during the course of the second day, otherwise there was no difference in the images taken in the course of a day (second or third day). A simplified protocol requires a minimum of three images to distinguish all five patterns of colonic transit. The activity should be ingested in the morning (7 00 am) and the first image taken at the end of the working day (8-10 hours after ingestion), the second image on the morning of the second day, and the third image during the course of the third day. This simple protocol would provide all the clinically relevant information necessary for correct classification of the colonic transit.  相似文献   
18.
19.
20.
The ActA protein is an essential determinant of pathogenicity that is responsible for the actin-based motility of Listeria monocytogenes in mammalian cells and cell-free extracts. ActA appears to control at least four functions that collectively lead to actin-based motility: (1) initiation of actin polymerization, (2) polarization of ActA function, (3) transformation of actin polymerization into a motile force and (4) acceleration of movement mediated by the host protein profilin.  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