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   17221篇
  免费   270篇
  国内免费   31篇
电工技术   198篇
综合类   19篇
化学工业   2025篇
金属工艺   377篇
机械仪表   345篇
建筑科学   517篇
矿业工程   66篇
能源动力   307篇
轻工业   1228篇
水利工程   97篇
石油天然气   122篇
无线电   1523篇
一般工业技术   2389篇
冶金工业   6738篇
原子能技术   159篇
自动化技术   1412篇
  2022年   81篇
  2021年   108篇
  2019年   107篇
  2018年   141篇
  2017年   103篇
  2016年   95篇
  2015年   113篇
  2014年   231篇
  2013年   576篇
  2012年   316篇
  2011年   424篇
  2010年   345篇
  2009年   352篇
  2008年   465篇
  2007年   452篇
  2006年   437篇
  2005年   397篇
  2004年   325篇
  2003年   371篇
  2002年   316篇
  2001年   324篇
  2000年   316篇
  1999年   456篇
  1998年   1941篇
  1997年   1193篇
  1996年   829篇
  1995年   554篇
  1994年   495篇
  1993年   532篇
  1992年   286篇
  1991年   257篇
  1990年   265篇
  1989年   229篇
  1988年   244篇
  1987年   223篇
  1986年   209篇
  1985年   265篇
  1984年   208篇
  1983年   206篇
  1982年   208篇
  1981年   190篇
  1980年   212篇
  1979年   129篇
  1978年   138篇
  1977年   297篇
  1976年   426篇
  1975年   142篇
  1974年   126篇
  1973年   108篇
  1970年   83篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
At times, people keep their emotions from showing during social interactions. The authors' analysis suggests that such expressive suppression should disrupt communication and increase stress levels. To test this hypothesis, the authors conducted 2 studies in which unacquainted pairs of women discussed an upsetting topic. In Study 1, one member of each pair was randomly assigned to (a) suppress her emotional behavior, (b) respond naturally, or (c) cognitively reappraise in a way that reduced emotional responding. Suppression alone disrupted communication and magnified blood pressure responses in the suppressors' partners. In Study 2, suppression had a negative impact on the regulators' emotional experience and increased blood pressure in both regulators and their partners. Suppression also reduced rapport and inhibited relationship formation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
32.
D. P. Phillips, T. E. Ruth, and L. M. Wagner (1993) reported that 1969-1990 California mortality data show that Chinese Americans are particularly vulnerable to diseases that Chinese astrology and traditional Chinese medicine associate with their birth years. For example, because fire is associated with the heart, a Chinese person born in a fire year (such as 1937) is more likely to die of heart disease than is a Chinese person born in a nonfire year. However, many diseases were excluded from this study, some diseases that were included have ambiguous links to birth years, and the statistical tests were indirect. A more complete statistical analysis and independent California mortality data for the years 1960-1968 and 1991-2002 did not replicate the original results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
33.
34.
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   
35.
36.
37.
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   
38.
The literature provides little information on high-speed, high-normal-load, plain linear bearings, although the case for two rigid surfaces in relative linear motion can readily be solved by assuming squeeze action resistance. A new genus of internal combustion engines based on the Stiller-Smith mechanism incorporates connecting rods constrained by linear bearings, with the central normal load on the rod restricted by an oil film. A general analysis takes into account the bending of the rod, when the distributed oil film pressure resists the distributed load on the elastic rod. Design charts result that yield the dimensionless velocity at which the rod sinks in the oil as a function of the dimensionless load and the bearing clearance, and predict the deflection of the beam. The rod clearance history simulations for the Stiller-Smith engine compare favourably with computations for the rigid beam, confirming the analysis technique.  相似文献   
39.
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   
40.
The nave of Santa Maria Novella, a Dominican church in Florence Italy is representative of a Florentine Gothic system of construction. This system, consisting of domical rib vaults on square nave bays, high side aisles, and crypto-buttressing, differs substantially from the French high Gothic system of even-level-crown rib vaults on rectangular bays, with flying buttresses over relatively low aisles. An investigation into the structural aspects of the Florentine Gothic construction system reveals that the domical vaults increase the longitudinal thrust and reduce the transverse thrust, which may require additional precautions to be taken during construction, but entails a less elaborate buttressing system. The domical vaults are found to perform well structurally, with an absence of tensile stresses, and are more suitable for a square bay. In general, the structural system of the nave of Santa Maria Novella is found to be the product of carefully considered structural design, which may be accepted as an alternative to the French Gothic construction system.  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