全文获取类型
收费全文 | 205882篇 |
免费 | 2413篇 |
国内免费 | 565篇 |
专业分类
电工技术 | 3509篇 |
综合类 | 141篇 |
化学工业 | 31821篇 |
金属工艺 | 10265篇 |
机械仪表 | 7010篇 |
建筑科学 | 3994篇 |
矿业工程 | 2161篇 |
能源动力 | 4631篇 |
轻工业 | 12873篇 |
水利工程 | 2920篇 |
石油天然气 | 7726篇 |
武器工业 | 22篇 |
无线电 | 21497篇 |
一般工业技术 | 45169篇 |
冶金工业 | 34381篇 |
原子能技术 | 6620篇 |
自动化技术 | 14120篇 |
出版年
2021年 | 2049篇 |
2019年 | 1998篇 |
2018年 | 3678篇 |
2017年 | 3716篇 |
2016年 | 3998篇 |
2015年 | 2232篇 |
2014年 | 3781篇 |
2013年 | 8737篇 |
2012年 | 5677篇 |
2011年 | 7213篇 |
2010年 | 5854篇 |
2009年 | 6486篇 |
2008年 | 6609篇 |
2007年 | 6491篇 |
2006年 | 5569篇 |
2005年 | 5116篇 |
2004年 | 4629篇 |
2003年 | 4553篇 |
2002年 | 4366篇 |
2001年 | 4472篇 |
2000年 | 4184篇 |
1999年 | 4198篇 |
1998年 | 10183篇 |
1997年 | 7181篇 |
1996年 | 5500篇 |
1995年 | 4131篇 |
1994年 | 3597篇 |
1993年 | 3838篇 |
1992年 | 2983篇 |
1991年 | 2995篇 |
1990年 | 2890篇 |
1989年 | 2852篇 |
1988年 | 2865篇 |
1987年 | 2509篇 |
1986年 | 2568篇 |
1985年 | 2854篇 |
1984年 | 2687篇 |
1983年 | 2554篇 |
1982年 | 2300篇 |
1981年 | 2269篇 |
1980年 | 2345篇 |
1979年 | 2359篇 |
1978年 | 2382篇 |
1977年 | 2487篇 |
1976年 | 2876篇 |
1975年 | 2188篇 |
1974年 | 2068篇 |
1973年 | 2166篇 |
1972年 | 1940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.
992.
Hemagglutinins present in Amaranthus leucocarpus seed meal were extracted with saline buffer and nutritive value was estimated by PER, NPR as well as Digestible Energy Consumption Evaluations. Protein digestibility was determined both in vitro and in vivo. Trypsin inhibitor activity was also determined. Saline-extracted Amaranth meal had significantly higher PER and NPR values than whole meal (p<0.05). There were no significant differences in digestible energy (Kcal/day/ animal) and protein consumption (g/day/animal) between diets (p<0.05). A. leucocarpus improves in nutritive value after the saline extraction procedures and has a good potential as a complementary food due to its lysine content. In addition purified agglutinin may be a useful biochemical. 相似文献
993.
Holstein heifer calves from selected and control lines were treated with growth hormone-releasing factor to determine whether the magnitude of the pituitary growth hormone response is associated with genetic potential for milk yield. Cows in the selected line were bred to highest Predicted Difference milk sires available each year, while control line cows were bred to bulls that were average for 1964 milk production. Eight calves from each line of similar age (206 to 210 days) and weight (205 kg average) were injected intravenously with .1 microgram/kg growth hormone-releasing factor. Dams' first lactation 305-day mature equivalent records were 10,192 +/- 495 kg for selected calves and 6,908 +/- 376 kg for control calves. Before treatment, GH tended to be higher in selected than control calves (mean +/- SE: selected = 7.5 +/- 1.8, control = 4.6 +/- .4 ng/ml). After injection, peak GH were reached within 20 min and were similar in selected and control calves, averaging 66 +/- 16 and 73 +/- 13 ng/ml, respectively. Results indicate that the magnitude of the growth hormone response to growth hormone-releasing factor is not related to future performance of dairy calves. 相似文献
994.
An experimental investigation on the nature of reverse current of silicon power pn-junctions 总被引:5,自引:0,他引:5
At this time, little importance is given to the surface component of reverse leakage current of silicon pn-junctions although reliability issues reveal device blocking weakness when performing at high voltage and temperature. Junctions which have almost the same perimeter but different area have been realized and their reverse current has been measured at room temperature and high temperature both for standard recovery and fast recovery (gold-doped or electron irradiated) pn-junctions. It is shown that for standard recovery junctions the surface component of the reverse current is the primary component from room temperature up to above 150/spl deg/C and has influence on reaching high permissible working voltages. For gold-doped or electron irradiated junctions, the bulk component is dominant at high junction temperature, but it is shown that a comparatively negligible surface component can impose lower reverse working voltages or lower junction operation temperature. The surface component may be a cause of limitation on the operation of power silicon diodes at high reverse voltage above 175-200/spl deg/C junction temperature. 相似文献
995.
Narayanaswami C. Kamijoh N. Raghunath M. Inoue T. Cipolla T. Sanford J. Schlig E. Venkiteswaran S. Guniguntala D. Kulkarni V. Yamazaki K. 《Computer》2002,35(1):33-41
Nearly four years in development, the IBM Linux watch contains a complete computer system that runs Linux, displays X11 graphics, and has wireless connectivity. The system fits in a case that could pass as a slightly unusual analog timepiece with a somewhat odd shape and an extraordinarily brilliant face. The developers have created two versions of the watch, one with an organic light-emitting diode display and the other with a liquid crystal display. Still considered a research prototype, the watch already runs some personal information management applications, and it can communicate with PCs, PDAs, and other wireless-enabled devices, viewing condensed e-mail and directly receiving pager-like messages. Eventually, users will be able to access various Internet-based services, such as up-to-the-minute information about weather, traffic conditions, the stock market, and sports 相似文献
996.
N. V. Lubkov 《Automation and Remote Control》2002,63(9):1524-1532
Calculation relations were obtained and step-by-step procedures were developed in order to model failures of given multiplicities in system elements and random sojourns of the semi-Markovian process in various states, as well as to construct variational series. These procedures can be used to design simulation systems of various destinations. 相似文献
997.
A group parity prediction scheme which can be used for concurrent testing of linear feedback shift register circuits is described. 相似文献
998.
999.
On navigating between friends and foes 总被引:1,自引:0,他引:1
Kiryati N. Bruckstein A.M. 《IEEE transactions on pattern analysis and machine intelligence》1991,13(6):602-606
The problem of determining the optimal straight path between a planar set of points is considered. Each point contributes to the cost of a path a value that depends on the distance between the path and the point. The cost function, quantifying this dependence, can be arbitrary and may be different for different points. An algorithm to solve this problem using an extension of the Hough transform is described. The range of applications includes straight-line fitting to a set of points in the presence of outliers, navigation, and path planning. The proposed extended Hough transform can be tuned to equivalent to well-known robust least-squares techniques, and allows efficient, approximate M -estimation 相似文献
1000.
S. O. Slesarevskii A. M. Belavskii M. N. Korotenko V. S. Lyubarskii V. P. Pavlenko V. A. Snigerev A. V. Tkachenko 《Atomic Energy》1989,67(5):853-855
Translated from Atomnaya Énergiya, Vol. 67, No. 5, pp. 358–359, November, 1989. 相似文献