全文获取类型
收费全文 | 281544篇 |
免费 | 3242篇 |
国内免费 | 1022篇 |
专业分类
电工技术 | 4220篇 |
综合类 | 2458篇 |
化学工业 | 40009篇 |
金属工艺 | 12689篇 |
机械仪表 | 9040篇 |
建筑科学 | 6928篇 |
矿业工程 | 1853篇 |
能源动力 | 6227篇 |
轻工业 | 20616篇 |
水利工程 | 3519篇 |
石油天然气 | 4381篇 |
武器工业 | 8篇 |
无线电 | 32171篇 |
一般工业技术 | 55744篇 |
冶金工业 | 39788篇 |
原子能技术 | 5337篇 |
自动化技术 | 40820篇 |
出版年
2021年 | 1614篇 |
2019年 | 1581篇 |
2018年 | 16742篇 |
2017年 | 15742篇 |
2016年 | 12547篇 |
2015年 | 2380篇 |
2014年 | 3301篇 |
2013年 | 9145篇 |
2012年 | 8100篇 |
2011年 | 16166篇 |
2010年 | 13649篇 |
2009年 | 11757篇 |
2008年 | 13045篇 |
2007年 | 14088篇 |
2006年 | 5691篇 |
2005年 | 6386篇 |
2004年 | 6093篇 |
2003年 | 6018篇 |
2002年 | 5060篇 |
2001年 | 4754篇 |
2000年 | 4755篇 |
1999年 | 4792篇 |
1998年 | 11449篇 |
1997年 | 8160篇 |
1996年 | 6461篇 |
1995年 | 4697篇 |
1994年 | 4294篇 |
1993年 | 4089篇 |
1992年 | 3238篇 |
1991年 | 3103篇 |
1990年 | 2877篇 |
1989年 | 2955篇 |
1988年 | 2841篇 |
1987年 | 2401篇 |
1986年 | 2311篇 |
1985年 | 2719篇 |
1984年 | 2508篇 |
1983年 | 2353篇 |
1982年 | 2092篇 |
1981年 | 2204篇 |
1980年 | 2032篇 |
1979年 | 2128篇 |
1978年 | 2125篇 |
1977年 | 2366篇 |
1976年 | 3189篇 |
1975年 | 1835篇 |
1974年 | 1761篇 |
1973年 | 1773篇 |
1972年 | 1444篇 |
1971年 | 1340篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
151.
Girgis A.A. Makram E.B. Cline M.L. Jr. Fortson H.S. Jr. 《Power Systems, IEEE Transactions on》1992,7(4):1584-1590
The authors present a successful model of industry/university cooperation in establishing a strong power system curriculum in both the graduate and undergraduate level. Numerous long-term and short-term research projects have been developed to satisfy the university mission and to tackle challenging problems facing the power industry. A unique structure for the Clemson University Electric Power Research Association (CUEPRA) has been established to promote electric power system research and to meet the need for a working communication link between the power industry and the academic community. The power industries involvements in the power program at Clemson University and the strategic improvements that have been accomplished in research and education are outlined 相似文献
152.
153.
B Cribier 《Canadian Metallurgical Quarterly》1998,125(6-7):389-392
154.
Type testing for fault currents for medium-voltage circuit breakers rated at 15 kV to 72.5 kV is addressed. The ANSI designation of a new class of definite-purpose circuit breakers capable of switching transformer secondary faults and the introduction of the requirement for short-line-fault tests for breakers rated 72.5 kV and below have increased the difficulty of performing type tests in a testing laboratory. It is concluded that synthetic testing using the parallel current injection circuit is described in ANSI C37.081 provides the best available method for proving these complex requirements for medium-voltage circuit breakers 相似文献
155.
The author reviews encryption algorithms and standards, how they compare, how they differ, and where they are headed. Attention is given to secret-key cryptosystems, public-key cryptosystems, digital signature schemes, key-agreement algorithms, cryptographic hash functions, and authentication codes. Applications considered are secure electronic mail, secure communications, directory authentication and network management, banking, and escrowed encryption 相似文献
156.
157.
158.
159.
Analytical solution of a system of nonlinear measuring equations of a 12-pole microwave reflectometer was obtained. Criteria for selecting a true solution in the general case were developed and the analysis was conducted for a number of particular cases that may generate practical interest. 相似文献
160.
B. S. Bokshtein D. V. Vaganov S. N. Zhevnenko 《The Physics of Metals and Metallography》2007,104(6):564-570
Surface tension of pure copper and its alloys with Sn has been measured at 1000°C in a hydrogen atmosphere. Surface tension of a free surface equaled 1.81 N/m for pure copper, and 1.55, 1.38, and 1.28 N/m for the alloys with 0.05, 0.22, and 0.33 at % Sn, respectively; surface tension at grain boundaries equaled 0.5 N/m for pure copper, and 0.36, 0.3, and 0.23 N/m for the alloys, respectively. Based on these data, the concentration dependence of tin absorption at a free surface and grain boundaries has been calculated. Parameters of Sn absorption at grain boundaries and a free surface of copper have been compared with those of Sb and Bi. 相似文献