全文获取类型
收费全文 | 32707篇 |
免费 | 3631篇 |
国内免费 | 1876篇 |
专业分类
电工技术 | 4700篇 |
技术理论 | 4篇 |
综合类 | 3569篇 |
化学工业 | 1239篇 |
金属工艺 | 560篇 |
机械仪表 | 2218篇 |
建筑科学 | 4261篇 |
矿业工程 | 1288篇 |
能源动力 | 1438篇 |
轻工业 | 1714篇 |
水利工程 | 2048篇 |
石油天然气 | 1043篇 |
武器工业 | 864篇 |
无线电 | 3017篇 |
一般工业技术 | 3148篇 |
冶金工业 | 1670篇 |
原子能技术 | 453篇 |
自动化技术 | 4980篇 |
出版年
2024年 | 134篇 |
2023年 | 475篇 |
2022年 | 824篇 |
2021年 | 1044篇 |
2020年 | 1075篇 |
2019年 | 935篇 |
2018年 | 950篇 |
2017年 | 1040篇 |
2016年 | 1387篇 |
2015年 | 1318篇 |
2014年 | 2181篇 |
2013年 | 2450篇 |
2012年 | 2345篇 |
2011年 | 2683篇 |
2010年 | 1991篇 |
2009年 | 1995篇 |
2008年 | 1864篇 |
2007年 | 2189篇 |
2006年 | 1957篇 |
2005年 | 1592篇 |
2004年 | 1328篇 |
2003年 | 1151篇 |
2002年 | 917篇 |
2001年 | 775篇 |
2000年 | 661篇 |
1999年 | 498篇 |
1998年 | 411篇 |
1997年 | 330篇 |
1996年 | 290篇 |
1995年 | 242篇 |
1994年 | 228篇 |
1993年 | 140篇 |
1992年 | 123篇 |
1991年 | 77篇 |
1990年 | 90篇 |
1989年 | 70篇 |
1988年 | 80篇 |
1987年 | 59篇 |
1986年 | 37篇 |
1985年 | 28篇 |
1984年 | 33篇 |
1983年 | 29篇 |
1982年 | 14篇 |
1981年 | 15篇 |
1980年 | 12篇 |
1979年 | 10篇 |
1965年 | 23篇 |
1964年 | 13篇 |
1957年 | 11篇 |
1956年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
91.
本文对CIMS装配线和拆卸线的可靠性问题进行研究。文中分析了它们的运行状况,求出了两种生产线的稳态可用度,并用一个例子加以说明。 相似文献
92.
In a survey of the practical wind energy resource present in the Tayside Region of Scotland it was estimated that over 1500 km2 of land is suitable for wind energy development in the Region after consideration of a range of physical, technical and institutional factors. Wind speed data for this survey was obtained from the Energy Technology Support Unit (ETSU) UK Wind Speed Data Package. To verify the wind speeds obtained from the ETSU package a representative sample of sites in and around the identified areas of potential in Tayside were modelled for mean annual wind speed using the Wind Atlas Analysis and Application Program (WAsP). The wind speeds for the sites obtained from the WAsP analysis were compared with those obtained from the ETSU UK Wind Speed Data Package and conclusions drawn as to the reliability of the Tayside wind energy survey and the general applicability of the ETSU package for broad wind energy resource assessment. 相似文献
93.
The analysis of recently collected wind data at five sites in Saudi Arabia namely, Dhulum, Arar, Yanbu, Gassim and Dhahran is presented. The five sites represent different geographically and climatologically conditions. The data collected over a period spanned between 1995 and 2002 with different collection periods for each site. Daily, monthly and frequency profiles of the wind speed at the sites showed that Dhulum and Arar sites have higher wind energy potential with annual wind speed average of 5.7 and 5.4 m/s and speeds higher than 5 m/s for 60 and 47% of the time, respectively. The two sites are candidates for remote area wind energy applications. The costal site's, i.e. Yanbu and Dhahran wind speed data indicated that the two sites have lower annual wind speed averages and wind blows at speed higher than 5 m/s during afternoon hours. That makes the two sites candidates for grid connected wind systems for electrical load peak shaving. The data of Gassim site showed that the site has the lowest wind energy potential compared to the others. The annual energy produced by a Nordex N43 wind machine is estimated to be 1080, 990, 730, 454 and 833 MWh for Dhulum, Arar, Yanbu, Gassim and Dhahran, respectively. The analysis showed that the estimated annual energy produced by the machine based on 10 min averaged data is 2.5% higher than the estimated energy based on 30 min averaged data. 相似文献
94.
In the framework of joint effort between the Nuclear Energy Agency (NEA) of OECD, the United States Department of Energy (US DOE), and the Commissariat a l'Energie Atomique (CEA), France a coupled three-dimensional (3D) thermal-hydraulics/neutron kinetics benchmark for VVER-1000 was defined. The benchmark consists of calculation of a pump start-up experiment labelled V1000CT-1 (Phase 1), as well as a vessel mixing experiment and main steam line break (MSLB) transient labelled V1000CT-2 (Phase 2), respectively. The reference nuclear plant is Kozloduy-6 in Bulgaria. The overall objective is to assess computer codes used in the analysis of VVER-1000 reactivity transients. A specific objective is to assess the vessel mixing models used in system codes. Plant data are available for code validation consisting of one experiment of pump start-up (V1000CT-1) and one experiment of steam generator isolation (V1000CT-2). The validated codes can be used to calculate asymmetric MSLB transients involving similar mixing patterns. This paper summarizes a comparison of CATHARE and TRAC-PF1 system code results for V1000CT-1, Exercise 1, which is a full plant point kinetics simulation of a reactor coolant system (RCS) pump start-up experiment. The reference plant data include integral and sector average parameters. The comparison is made from the point of view of vessel mixing and full system simulation. CATHARE used a six-sector multiple 1D vessel thermal-hydraulic model with cross flows and TRAC used a six-sector, 18-channel coarse-mesh 3D vessel model. Good agreement in terms of integral parameters and inter-loop mixing is observed. 相似文献
95.
A practical approach to develop a more realistic fault-tree model with a consideration of various conditions endured by a human operator is proposed. In safety-critical systems, the generation failure of an actuation signal is caused by the concurrent failures of the automated systems and an operator action. These two sources of safety signals are complicatedly correlated. The failures of sensors or automated systems will cause a lack of necessary information for a human operator and result in error-forcing contexts such as the loss of corresponding alarms and indications. It is well known that the error-forcing contexts largely affect the operator's performance. An automated system which consists of multiple processing channels and complex components is also affected by the availability of the sensors. This paper proposes a condition-based human reliability assessment (CBHRA) method in order to address these complicated conditions in a practical way. We apply the CBHRA method to the manual actuation of the safety features such as a reactor trip and auxiliary feedwater actuation in Korean Standard Nuclear Power Plants. Even the human error probability of each given condition is simply assumed, the application results prove that the CBHRA effectively accommodates the complicated error-forcing contexts into the fault trees. 相似文献
96.
97.
农业重组微生物生物安全研究进展 总被引:2,自引:2,他引:0
综述了近年来农业重组微生物的研究现状和进展 ,详细介绍农业重组微生物环境释放的监控方法以及对环境的冲击作用 ,对一些有关生物安全研究的热点问题进行了探讨 相似文献
98.
99.
As IC devices scale down to the submicron level, the resistance-capacitance (RC) time delays are the limitation to circuit
speed. A solution is to use low dielectric constant materials and low resistivity materials. In this work, the influence of
underlying barrier Ta on the electromigration (EM) of Cu on hydrogen silsesquioxane (HSQ) and SiO2 substrates was investigated. The presence of a Ta barrier not only improves the adhesion between Cu and dielectrics, but
also enhances the crystallinity of Cu film and improves the Cu electromigration resistance. The activation energy obtained
suggests a grain boundary migration mechanism and the current exponent calculated indicates the Joule heating effect. 相似文献
100.