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   19453篇
  免费   487篇
  国内免费   43篇
电工技术   297篇
综合类   29篇
化学工业   2841篇
金属工艺   357篇
机械仪表   425篇
建筑科学   740篇
矿业工程   39篇
能源动力   402篇
轻工业   2174篇
水利工程   193篇
石油天然气   35篇
无线电   1982篇
一般工业技术   2843篇
冶金工业   4916篇
原子能技术   221篇
自动化技术   2489篇
  2022年   178篇
  2021年   301篇
  2020年   167篇
  2019年   258篇
  2018年   309篇
  2017年   288篇
  2016年   349篇
  2015年   238篇
  2014年   412篇
  2013年   846篇
  2012年   711篇
  2011年   889篇
  2010年   666篇
  2009年   651篇
  2008年   738篇
  2007年   736篇
  2006年   582篇
  2005年   590篇
  2004年   490篇
  2003年   474篇
  2002年   440篇
  2001年   392篇
  2000年   387篇
  1999年   463篇
  1998年   1622篇
  1997年   1024篇
  1996年   759篇
  1995年   514篇
  1994年   446篇
  1993年   453篇
  1992年   222篇
  1991年   209篇
  1990年   214篇
  1989年   214篇
  1988年   218篇
  1987年   160篇
  1986年   169篇
  1985年   223篇
  1984年   152篇
  1983年   130篇
  1982年   113篇
  1981年   139篇
  1980年   132篇
  1979年   132篇
  1978年   87篇
  1977年   161篇
  1976年   224篇
  1975年   85篇
  1974年   66篇
  1973年   81篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
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   
62.
I. Aidos    N. Kreb    M. Boonman    J.B. Luten    R.M. Boom    A. Van  Der Padt 《Journal of food science》2003,68(2):581-586
ABSTRACT: A pilot plant used for upgrading herring byproducts into fish oil was analyzed on its operational efficiency and product quality. The temperature of the heat exchanger and the speeds of the pump and the 3-phase decanter were varied according to a 23 fractional factorial design. The initial amount of oxidation products present in the crude oil, its storage stability, and the yields from the different obtained products were determined. Multivariate data analysis of the advanced screening stage showed that T had neither influence on the quality nor on the yield in contrast to D and MP (P < 0.05). Process optimization results showed that the quality of the oil was influenced by an interaction effect between the speed of the MP and the D. Oils processed with the highest MP speed were the most stable during storage.  相似文献   
63.
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   
64.
Solar cells are the most commonly used devices in customer products to achieve power autonomy. This paper discusses a complementary approach to provide power autonomy to devices on a human body, i.e., thermoelectric conversion of human heat. In indoor applications, thermoelectric converters on the skin can provide more power per square centimeter than solar cells, particularly in adverse illumination conditions. Moreover, they work day and night. The first sensor nodes powered by human heat have been demonstrated and tested on people in 2004-2005. They used the state-of-the-art 100-muW watch-size thermoelectric wrist generators fabricated at IMEC and based on custom-design small-size BiTe thermopiles. The sensor node is completed with a power conditioning module, a microcontroller, and a wireless transceiver mounted on a watchstrap  相似文献   
65.
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   
66.
Recent years have witnessed major governmental initiatives regarding critical infrastructure protection (CIP). During that same time, critical infrastructures (CIs) have undergone massive institutional restructuring under the headings of privatization, deregulation and liberalization. Little research has gone into understanding the interactions between these two developments. In this article, we outline the consequences of institutional restructuring for the changing ways in which CIs ensure the reliability and security of their networks and services. Neither Normal Accident Theory nor High‐Reliability Theory can account for reliability under these conditions. We then investigate the implications of these findings for CIP.  相似文献   
67.
A comprehensive model for the recrystallization kinetics is proposed which incorporates both microstructure and the textural components in the deformed state. The model is based on the single-grain approach proposed previously. The influence of the as-deformed grain orientation, which affects the stored energy via subgrain size and sub-boundary misorientation, is taken into account. The effects of the deformed grain geometry, the nucleation-site density, and the initial grain size prior to deformation on the recrystallization kinetics are assessed. The model is applied to the recrystallization kinetics of a cold-rolled AA1050 alloy.  相似文献   
68.
69.
Pin&Play: the surface as network medium   总被引:2,自引:0,他引:2  
Integrating appliances in the home through a wired network often proves to be impractical: routing cables is usually difficult, changing the network structure afterward even more so, and portable devices can only be connected at fixed connection points. Wireless networks are not the answer either: batteries have to be regularly replaced or changed, and what they add to the device's size and weight might be disproportionate for smaller appliances. In Pin&Play, we explore a design space in between typical wired and wireless networks, investigating the use of surfaces to network objects that are attached to it. This article gives an overview of the network model, and describes functioning prototypes that were built as a proof of concept.  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