全文获取类型
收费全文 | 271268篇 |
免费 | 2462篇 |
国内免费 | 665篇 |
专业分类
电工技术 | 5075篇 |
综合类 | 229篇 |
化学工业 | 37994篇 |
金属工艺 | 14466篇 |
机械仪表 | 11446篇 |
建筑科学 | 6153篇 |
矿业工程 | 2014篇 |
能源动力 | 5739篇 |
轻工业 | 18240篇 |
水利工程 | 3327篇 |
石油天然气 | 5364篇 |
武器工业 | 8篇 |
无线电 | 29807篇 |
一般工业技术 | 58670篇 |
冶金工业 | 42733篇 |
原子能技术 | 6060篇 |
自动化技术 | 27070篇 |
出版年
2021年 | 1606篇 |
2019年 | 1570篇 |
2018年 | 10864篇 |
2017年 | 11458篇 |
2016年 | 7393篇 |
2015年 | 2320篇 |
2014年 | 3166篇 |
2013年 | 8996篇 |
2012年 | 7614篇 |
2011年 | 15111篇 |
2010年 | 13341篇 |
2009年 | 12972篇 |
2008年 | 12814篇 |
2007年 | 14846篇 |
2006年 | 5658篇 |
2005年 | 8721篇 |
2004年 | 6934篇 |
2003年 | 6503篇 |
2002年 | 5170篇 |
2001年 | 4723篇 |
2000年 | 4713篇 |
1999年 | 4750篇 |
1998年 | 11384篇 |
1997年 | 8124篇 |
1996年 | 6424篇 |
1995年 | 4683篇 |
1994年 | 4304篇 |
1993年 | 4099篇 |
1992年 | 3238篇 |
1991年 | 3098篇 |
1990年 | 2871篇 |
1989年 | 2951篇 |
1988年 | 2835篇 |
1987年 | 2398篇 |
1986年 | 2309篇 |
1985年 | 2715篇 |
1984年 | 2505篇 |
1983年 | 2346篇 |
1982年 | 2090篇 |
1981年 | 2203篇 |
1980年 | 2029篇 |
1979年 | 2124篇 |
1978年 | 2120篇 |
1977年 | 2366篇 |
1976年 | 3189篇 |
1975年 | 1833篇 |
1974年 | 1761篇 |
1973年 | 1773篇 |
1972年 | 1443篇 |
1971年 | 1339篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
152.
Fractal error for detecting man-made features in aerial images 总被引:3,自引:0,他引:3
A technique is proposed for aiding photointerpreters in detecting man-made features in aerial reconnaissance images. The technique, which uses a metric called fractal error, is based on the observed propensity of natural image features to fit a fractional Brownian motion model. Man-made features usually do not fit this model well, and consequently the fractal error metric may be used as a discriminant function for detecting man-made scene features 相似文献
153.
154.
155.
María P. Albano Liliana B. Garrido 《Journal of Materials Synthesis and Processing》2002,10(4):211-218
Si3N4powders coated with 6 wt% Y2O3and 4 wt% Al2O3were prepared by coprecipitation. The resulting powders were dispersed in water at different pH values and with addition of various amounts of ammonium polyacrylate (NH4PA) to produce 32 vol% slips. The influence of the amount of NH4PA solution added and pH on the rheological properties of 32 vol% coated Si3N4slips were studied. In addition, the sintered density of cast samples was determined and related to the degree of slip dispersion. The adsorption of the NH4PA on the coated particle surface was rather high and the surface became saturated near 0.86 mg/m2at pH 9.2. High NH4PA concentrations (1.7–3 wt%) were necessary to obtain well dispersed 32 vol% coated Si3N4slips at pH 9.2. The best stabilization was obtained with the addition of 2.3 wt% NH4PA; in this condition, the viscosity reached a minimum value of 35 mPa.s at 100 s–1. The slip viscosity increased with increasing pH from 9.2 to 10.2. Slips with low viscosities gave a more dense packing of cast samples and consequently higher sintered density values. 相似文献
156.
Bagdonavicius V.B. Gerville-Reache L. Nikulin M.S. 《Reliability, IEEE Transactions on》2002,51(1):27-31
Applications of the additive accumulation of damages (AAD) or the accelerated failure time (AFT) and the proportional hazards (PH) models in accelerated life testing with step-stresses are discussed. A new model including AAD and PH models is proposed. It is more reasonable than the PH model and wider then the AAD model. Constructing the maximum likelihood function is discussed 相似文献
157.
Metal Science and Heat Treatment - 相似文献
158.
A. A. Konstantinov N. V. Kurenkov A. B. Malinin T. E. Sazonova S. V. Sepman 《Atomic Energy》1989,67(3):696-698
Translated from Atomnaya Énergiya, Vol. 67, No. 3, pp. 215–216, September, 1989. 相似文献
159.
160.