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   277835篇
  免费   3326篇
  国内免费   1304篇
电工技术   4800篇
综合类   519篇
化学工业   40249篇
金属工艺   11123篇
机械仪表   8414篇
建筑科学   6406篇
矿业工程   1575篇
能源动力   6966篇
轻工业   22455篇
水利工程   3035篇
石油天然气   5781篇
武器工业   43篇
无线电   33487篇
一般工业技术   56434篇
冶金工业   50867篇
原子能技术   7489篇
自动化技术   22822篇
  2021年   2151篇
  2019年   2060篇
  2018年   3574篇
  2017年   3670篇
  2016年   3897篇
  2015年   2484篇
  2014年   4346篇
  2013年   11965篇
  2012年   7061篇
  2011年   9699篇
  2010年   7528篇
  2009年   8747篇
  2008年   9090篇
  2007年   9129篇
  2006年   7801篇
  2005年   7246篇
  2004年   7197篇
  2003年   6972篇
  2002年   6713篇
  2001年   6844篇
  2000年   6476篇
  1999年   6760篇
  1998年   16296篇
  1997年   11578篇
  1996年   8915篇
  1995年   6843篇
  1994年   6013篇
  1993年   6051篇
  1992年   4395篇
  1991年   4180篇
  1990年   4073篇
  1989年   4056篇
  1988年   3750篇
  1987年   3387篇
  1986年   3392篇
  1985年   3739篇
  1984年   3460篇
  1983年   3217篇
  1982年   3024篇
  1981年   3038篇
  1980年   3030篇
  1979年   2829篇
  1978年   2869篇
  1977年   3141篇
  1976年   4096篇
  1975年   2417篇
  1974年   2380篇
  1973年   2398篇
  1972年   2018篇
  1971年   1781篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The quality-estimation and decision-making criteria based on the values of error possibility likelihood measures, error necessity likelihood, error possibility confidence, and error necessity confidence are considered. The criteria are formulated for the adequacy of an uncertain fuzzy (UF) model and conclusions based on the UF model for the object under investigation and the UF observation model.  相似文献   
992.
Space asymptotic theory is shown to be a suitable model for the study of pulsed experiments in neutron multiplying systems. After a short revisitation of the basic aspects of space asymptotic theory applied on the Laplace transformed one-group transport equation, the full solution is derived. It is shown how results are exact in representing localized pulse propagation in the first portion of the transient, until the boundary is reached by the neutron signal, since it propagates with a finite velocity. Approximate models are then derived starting from the exact formulation and the BN method is used to account for anisotropy effects. Numerical results are presented for one-dimensional systems, discussing the physical phenomena and noting the distortions introduced by approximate models, which may then turn out to be inadequate for the simulation of realistic pulsed experiments situations.  相似文献   
993.
994.
This social research project investigated community receptivity to using rainwater and greywater as alternative domestic water sources. It was focused in the Ku-ring-gai local government area in northern Sydney, and involved a household questionnaire followed by community leader interviews and resident focus groups. Trends, such as a prolonged drought and increasing population, compound the current crisis and concern facing Sydney's available water supply. Substitution of domestic potable water has been promoted as part of the solution. The research results revealed that community receptivity was highest for external uses, such as watering gardens and flushing toilets, and progressively decreased with increasing personal contact. Receptivity to greywater reuse fell more rapidly with the community believing there was a higher health risk associated with its use. Gender and cultural background were revealed as significant variables and give insight into the design of strategies to target these demographic groups. This evidence provides a reliable stocktake of current receptivity revealing that the community has good awareness and positive association with water reuse for many household activities. This now needs to be harnessed through programs targeted at developing skills, resources and motivation for new water reuse practices and technologies across diverse social groupings.  相似文献   
995.
Wideband miniature G-shaped antenna for dual-band WLAN applications   总被引:1,自引:0,他引:1  
A wideband miniature G-shaped coplanar waveguide fed dual-band antenna for a wireless local area network (WLAN) is proposed. The proposed antenna has good radiation pattern and can provide two separate measured impedance bandwidths of 0.55 GHz (about 22.9% centred at 2.42 GHz) and 2.85 GHz (about 50.9% centred at 5.60 GHz), so that it easily covers the required bandwidths for WLAN operation. This design results in a small antenna size of 22 times 18.5 mm with the ground plane regarded as part of the antenna structure.  相似文献   
996.
Listed are the grades of heat-resistant adhesives developed under the Andrianov’s scientific guidance at the All-Russia Institute of Aviation Materials on the basis of organosilicon polymers.  相似文献   
997.
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   
998.
Characterizing the impact of variability on circuit performance measurements (delay, power, and signal integrity) is necessary to avoid chip failure. The authors present a comprehensive methodology for analyzing the impact of device and metal variations on the power supply noise, and hence the signal integrity, of on-chip power grids.  相似文献   
999.
The authors review the progress in the RARDE (Royal Armament Research and Development Establishment) electromagnetic gun (REMGUN) program. They cover research on both railgun and LIA (linear induction accelerator) technology, including work on modeling, projectile/barrel interactions armatures, switching, and instrumentation. They also describe the major research facilities. Progress is reported in the identification and development of single-shot switches, integrated switch/barrel concepts, armatures and pulse power supplies as well as the integration of railgun components. LIA research has concentrated on launcher design and projectile/barrel interactions, highlighting the problems of pulse power systems for this form of electromagnetic launcher  相似文献   
1000.
A simple measurement method for the absolute Raman scattering cross-section of an optical fibre is presented. This method does not require a high power pump laser and it measures the fibre directly. It is also shown that the calculation of the cross-section depends on the fibre structure, such as its refractive index profile and the differential attenuation between the pump wavelength and Raman wavelength.<>  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