全文获取类型
收费全文 | 426273篇 |
免费 | 17638篇 |
国内免费 | 8975篇 |
专业分类
电工技术 | 14649篇 |
技术理论 | 13篇 |
综合类 | 13797篇 |
化学工业 | 66554篇 |
金属工艺 | 23858篇 |
机械仪表 | 19753篇 |
建筑科学 | 18783篇 |
矿业工程 | 7838篇 |
能源动力 | 9020篇 |
轻工业 | 24618篇 |
水利工程 | 7232篇 |
石油天然气 | 19695篇 |
武器工业 | 1415篇 |
无线电 | 44616篇 |
一般工业技术 | 74855篇 |
冶金工业 | 38959篇 |
原子能技术 | 9074篇 |
自动化技术 | 58157篇 |
出版年
2023年 | 3567篇 |
2022年 | 7352篇 |
2021年 | 10036篇 |
2020年 | 7614篇 |
2019年 | 6625篇 |
2018年 | 22157篇 |
2017年 | 22010篇 |
2016年 | 18424篇 |
2015年 | 9805篇 |
2014年 | 12537篇 |
2013年 | 17743篇 |
2012年 | 19484篇 |
2011年 | 27160篇 |
2010年 | 23203篇 |
2009年 | 20475篇 |
2008年 | 21257篇 |
2007年 | 21386篇 |
2006年 | 13525篇 |
2005年 | 12906篇 |
2004年 | 10014篇 |
2003年 | 9098篇 |
2002年 | 7953篇 |
2001年 | 7142篇 |
2000年 | 7053篇 |
1999年 | 7400篇 |
1998年 | 10499篇 |
1997年 | 8092篇 |
1996年 | 6589篇 |
1995年 | 5124篇 |
1994年 | 4393篇 |
1993年 | 4020篇 |
1992年 | 3306篇 |
1991年 | 3110篇 |
1990年 | 2974篇 |
1989年 | 2778篇 |
1988年 | 2686篇 |
1987年 | 2440篇 |
1986年 | 2453篇 |
1985年 | 2420篇 |
1984年 | 2321篇 |
1983年 | 2220篇 |
1981年 | 2259篇 |
1979年 | 2298篇 |
1978年 | 2455篇 |
1977年 | 2454篇 |
1976年 | 3121篇 |
1975年 | 2260篇 |
1974年 | 2316篇 |
1973年 | 2348篇 |
1972年 | 2158篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
V. I. Shtykov 《Power Technology and Engineering (formerly Hydrotechnical Construction)》1998,32(8):459-462
Conclusions 1. Use of dewatering systems based on voidless drainage is most effective when dewatering slightly permeable soils in regions
with a deep seasonal frost.
2. Two-story drainage with the upper and lower stories spaced 30 m apart accelerates the discharge of gravitational water
from the arable layer. Results of observations on two-story drainage in experimental-production sections indicated that it
discharges 2 – 3.8 times more water than systematic tubular drainage with an interdrain spacing of 10 m and a 0.2-m thick
three-dimensional filter of a sandy-gravelly mixture.
3. It is recommended to use crushed stone and porous-clay gravel with a fineness of 10 – 20 mm as a filler. In that case,
protection of the drain filler is, as a rule, required only from the intrusion of soil from above during construction in cohesive
soils with a plasticity indexW
p≥7.
4. seepage rate in a voidless drain should be lower than the scouring velocity for the soil in which the voidless drainage
is placed. In the opposite case, it is necessary to lower the grade of the drains or select a filler gradation such that the
seepage rate in the drain be lower than the scouring velocity.
Translated from Gidrotekhnicheskoe Stroitel’stvo, No. 8, pp. 41–43, August, 1998. 相似文献
22.
23.
24.
A systematic and straightforward procedure is developed for the synthesis and analysis of transformer-isolated power converters. The procedure can be used to determine the ranges of duty-ratio over which the transformer-isolated power converters of a given class can be operated without transformer saturation. The procedure can also be used to study the dependence of the power converter switch stresses on duty-ratios. This information is useful in the selection of the transformer-isolated power converter most suitable for a given application and in the design of this power converter with minimum switch stresses, high power density, and low cost 相似文献
25.
Metal Science and Heat Treatment - 相似文献
26.
27.
28.
Yu. I. Berdyshev 《Journal of Computer and Systems Sciences International》2006,45(4):526-531
An algorithm for construction of the reachability domain by the given time instant ? for a nonlinear third order system under the condition of preliminary approach to a predefined point is proposed. All possible cases of location of this point in the motion plane of the system for different values of the time instant ? are studied. 相似文献
29.
30.
The maintenance of the MACRO (a Monopoles, Astrophysics and Cosmic Ray Observatory), a large-area detector that will be used to search for rare constituents or phenomena in cosmic radiation penetrating deep underground, is addressed. A real-time expert system for diagnosing detector and data acquisition system anomalies, which is based on the NEXPERT commercial tool, is described. It performs online diagnosis and, if an abnormal condition is identified, takes the appropriate action to reduce the unavailability of the apparatus. The data acquisition system is CAMAC-based, and the sensor modules, which gather the significant values for diagnosis, are implemented in the VME crate 相似文献