全文获取类型
收费全文 | 263961篇 |
免费 | 3252篇 |
国内免费 | 828篇 |
专业分类
电工技术 | 5172篇 |
综合类 | 336篇 |
化学工业 | 37881篇 |
金属工艺 | 10328篇 |
机械仪表 | 8534篇 |
建筑科学 | 6340篇 |
矿业工程 | 1131篇 |
能源动力 | 6497篇 |
轻工业 | 23198篇 |
水利工程 | 2616篇 |
石油天然气 | 3934篇 |
武器工业 | 69篇 |
无线电 | 34975篇 |
一般工业技术 | 50599篇 |
冶金工业 | 47559篇 |
原子能技术 | 5446篇 |
自动化技术 | 23426篇 |
出版年
2021年 | 2082篇 |
2019年 | 2072篇 |
2018年 | 3520篇 |
2017年 | 3568篇 |
2016年 | 3773篇 |
2015年 | 2342篇 |
2014年 | 4113篇 |
2013年 | 11534篇 |
2012年 | 6676篇 |
2011年 | 9062篇 |
2010年 | 7120篇 |
2009年 | 7969篇 |
2008年 | 8862篇 |
2007年 | 8782篇 |
2006年 | 7990篇 |
2005年 | 7319篇 |
2004年 | 7037篇 |
2003年 | 6852篇 |
2002年 | 6466篇 |
2001年 | 6542篇 |
2000年 | 6238篇 |
1999年 | 6334篇 |
1998年 | 14362篇 |
1997年 | 10348篇 |
1996年 | 8189篇 |
1995年 | 6476篇 |
1994年 | 5780篇 |
1993年 | 5644篇 |
1992年 | 4605篇 |
1991年 | 4254篇 |
1990年 | 4116篇 |
1989年 | 3842篇 |
1988年 | 3672篇 |
1987年 | 3218篇 |
1986年 | 3111篇 |
1985年 | 3665篇 |
1984年 | 3450篇 |
1983年 | 3075篇 |
1982年 | 2904篇 |
1981年 | 3006篇 |
1980年 | 2802篇 |
1979年 | 2691篇 |
1978年 | 2525篇 |
1977年 | 2975篇 |
1976年 | 3583篇 |
1975年 | 2343篇 |
1974年 | 2335篇 |
1973年 | 2340篇 |
1972年 | 1858篇 |
1971年 | 1755篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A study was made of energy expenditures and factual nutrition of the workers engaged in synthetic leather manufacture. Antropometric measurements were also taken. Based on the study of daily energy expenditures, the calculations were made of the optimal requirements of the main substances and energy. The actual nutrition of the workers was found to provide the necessary caloricity covering energy expenditures. However, definite shortcomings were revealed in the structure of the foods consumed, namely insufficient intake of vegetable fats, the prevalence of simple sugars in the structure of carbohydrate component, insufficient intake of vitamins A, B1 and folacin. According to the antropometric measurements 30,4% of the examined workers were obese. 相似文献
992.
993.
994.
B. I. Venzel' E. A. Egorov V. V. Zhizhenkov V. D. Kleiner 《Journal of Engineering Physics and Thermophysics》1985,48(3):346-350
The method of proton magnetic resonance is used to determine the melting point of ice particles in the pores of monodisperse porous glasses ranging from 10 to 1000 Å in radius.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 48, No. 3, pp. 461–466, March, 1985. 相似文献
995.
S. D. Pol’skikh 《Pattern Recognition and Image Analysis》2006,16(1):33-36
An approach to the reconstruction problem of undistorted images of objects observed through randomly inhomogeneous media is
considered. The approach is based on the solution to the integral equation of the first kind (convolution equation) with an
unknown kernel and inaccurately defined right-hand side. It is demonstrated that the procedure for the construction of an
inverse operator needed for the solution is determined by the minimization of the nonlinear regularizing multiextremum functional,
which takes into account the a priori data regarding the positive intensity distribution in the image of an object. The analysis
of the structure of the multiextremum functional is presented. The estimates of the reconstructed images that correspond to
the global and local extrema are studied. The results of a numerical experiment on the reconstruction of the optical image
of an object observed through the turbulent atmosphere are presented. 相似文献
996.
D. O'Connor 《International Journal of Dairy Technology》2007,60(4):300-302
997.
998.
Probabilistic parameters related to the total loss of off-site power at the Chalk River Nuclear Laboratories (CRNL) are derived from site specific data. Because of weather related seasonal dependency a periodic power failure frequency model has been adopted. 相似文献
999.
1000.
Barry D. Solomon 《Energy Policy》1985,13(1):97-101
The prospects for rapid near-term development of a synfuel industry in the USA have decreased, due to depressed world oil prices, synfuel project cost overruns, and the lukewarm support of the Reagan administration. Nonetheless, socioeconomic and environmental impact analysis studies can provide valuable information for determining the regional welfare effects of proposed projects. The author discusses the results of a regional econometric analysis of the synfuel projects planned for Western Kentucky, which focuses on environmental impacts, and reveals the inevitable trade-offs that would accompany synfuel development. Some policy issues are briefly reviewed, especially that of efficient energy pricing. 相似文献