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   25185篇
  免费   532篇
  国内免费   33篇
电工技术   284篇
综合类   40篇
化学工业   3084篇
金属工艺   287篇
机械仪表   404篇
建筑科学   1014篇
矿业工程   60篇
能源动力   508篇
轻工业   2293篇
水利工程   291篇
石油天然气   35篇
武器工业   1篇
无线电   1893篇
一般工业技术   2778篇
冶金工业   9704篇
原子能技术   169篇
自动化技术   2905篇
  2023年   79篇
  2022年   186篇
  2021年   316篇
  2020年   167篇
  2019年   243篇
  2018年   303篇
  2017年   282篇
  2016年   333篇
  2015年   296篇
  2014年   464篇
  2013年   763篇
  2012年   777篇
  2011年   1051篇
  2010年   741篇
  2009年   773篇
  2008年   803篇
  2007年   796篇
  2006年   644篇
  2005年   641篇
  2004年   578篇
  2003年   541篇
  2002年   491篇
  2001年   389篇
  2000年   355篇
  1999年   597篇
  1998年   3333篇
  1997年   2003篇
  1996年   1284篇
  1995年   788篇
  1994年   722篇
  1993年   721篇
  1992年   266篇
  1991年   243篇
  1990年   269篇
  1989年   253篇
  1988年   271篇
  1987年   184篇
  1986年   183篇
  1985年   240篇
  1984年   160篇
  1983年   117篇
  1982年   134篇
  1981年   154篇
  1980年   126篇
  1979年   113篇
  1978年   104篇
  1977年   236篇
  1976年   327篇
  1975年   99篇
  1974年   78篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Document caching and connection caching are extensively studied problems. In document caching, one has to maintain caches containing documents accessible in a network. In connection caching, one has to maintain a set of open network connections that handle data transfer. Previous work investigated these two problems separately while in practice the problems occur together: In order to load a document, one has to establish a connection between network nodes if the required connection is not already open. In this paper we present the first study that integrates document and connection caching. We first consider a very basic model in which all documents have the same size and the cost of loading a document or establishing a connection is equal to 1. We present deterministic and randomized online algorithms that achieve nearly optimal competitive ratios unless the size of the connection cache is extremely small. We then consider general settings where documents have varying sizes. We investigate a FAULT model in which the loading cost of a document is 1 as well as a BIT model in which the loading cost is equal to the size of the document.  相似文献   
62.
The effect of cyclic stressing on the strength of single lap adhesive joints has been studied and a considerable reduction in strength observed when the maximum stress exceeds about 40% of the ultimate tensile strength, but whether or not a true endurance limit exists is not proven. Fallacies are shown in some of the techniques which have been proposed for studying the fatigue behaviour of adhesive joints.  相似文献   
63.
Excessive power supply noise during test can cause overkill. This article discusses two models for supply noise in delay testing and their application to test compaction. The proposed noise models avoid complicated power network analysis, making them much faster than existing power noise analysis tools. can cause performance degradation and  相似文献   
64.
65.
66.
This work discusses the potential of three multistage zeolite drying systems (counter-, co-, and cross-current) with a varying number of stages. The evaluation showed that for 2-4 stages with heat recovery the efficiency of the systems ranges between 80 and 90%. Additionally, by introducing a compressor, the latent heat in the exhaust air from the regenerator is recovered and used to heat the inlet air for an additional drying stage. As a result, for the counter-current drying system and compressor pressure 1.5-2 bar, a maximum energy efficiency of 120% is achieved, which results in halving the energy consumption compared to conventional drying systems.  相似文献   
67.
An unpackaged microchip is used as the sensing element in a miniaturized gaseous proportional chamber. This letter reports on the fabrication and performance of a complete radiation imaging detector based on this principle. Our fabrication schemes are based on wafer-scale and chip-scale postprocessing. Compared to hybrid-assembled gaseous detectors, our microsystem shows superior alignment precision and energy resolution, and offers the capability to unambiguously reconstruct 3D radiation tracks on the spot.  相似文献   
68.
A current assisted photonic demodulator for use as a pixel in a 3-D time-of-flight imager shows nearly 100% static demodulator contrast and is operable beyond 30 MHz. An integrated tunable sensitivity control is also presented for increasing the distance measurement range and avoiding unwanted saturation during integration periods. This is achieved by application of a voltage on a dedicated drain tap showing a quenching of sensor sensitivity to below 1%  相似文献   
69.
A product line architecture is a single specification capturing the overall architecture of a series of closely related products. Its structure consists of a set of mandatory elements and a set of variation points. Whereas mandatory elements are part of the architecture of every product in the product line architecture, variation points precisely define the dimensions along which the architectures of individual products differ from each other.The increased use of product line architectures in today's software development projects poses several challenges for existing testing techniques. In this paper we discuss those challenges and discuss what we believe are opportunities for addressing them.  相似文献   
70.
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