全文获取类型
收费全文 | 697275篇 |
免费 | 8284篇 |
国内免费 | 1652篇 |
专业分类
电工技术 | 12344篇 |
综合类 | 601篇 |
化学工业 | 106335篇 |
金属工艺 | 30545篇 |
机械仪表 | 22304篇 |
建筑科学 | 15743篇 |
矿业工程 | 5057篇 |
能源动力 | 17181篇 |
轻工业 | 53190篇 |
水利工程 | 8201篇 |
石油天然气 | 18037篇 |
武器工业 | 50篇 |
无线电 | 73122篇 |
一般工业技术 | 145137篇 |
冶金工业 | 125660篇 |
原子能技术 | 17764篇 |
自动化技术 | 55940篇 |
出版年
2021年 | 6697篇 |
2020年 | 4907篇 |
2019年 | 6375篇 |
2018年 | 11345篇 |
2017年 | 11337篇 |
2016年 | 11901篇 |
2015年 | 7621篇 |
2014年 | 12753篇 |
2013年 | 31072篇 |
2012年 | 19513篇 |
2011年 | 26155篇 |
2010年 | 20718篇 |
2009年 | 23219篇 |
2008年 | 23696篇 |
2007年 | 23144篇 |
2006年 | 19712篇 |
2005年 | 17924篇 |
2004年 | 17355篇 |
2003年 | 17113篇 |
2002年 | 16181篇 |
2001年 | 16228篇 |
2000年 | 15236篇 |
1999年 | 15478篇 |
1998年 | 37707篇 |
1997年 | 26932篇 |
1996年 | 20535篇 |
1995年 | 15645篇 |
1994年 | 13743篇 |
1993年 | 13613篇 |
1992年 | 10166篇 |
1991年 | 9769篇 |
1990年 | 9741篇 |
1989年 | 9389篇 |
1988年 | 8759篇 |
1987年 | 8050篇 |
1986年 | 7854篇 |
1985年 | 8621篇 |
1984年 | 8158篇 |
1983年 | 7417篇 |
1982年 | 6947篇 |
1981年 | 7118篇 |
1980年 | 6864篇 |
1979年 | 6902篇 |
1978年 | 6878篇 |
1977年 | 7781篇 |
1976年 | 9760篇 |
1975年 | 6064篇 |
1974年 | 5908篇 |
1973年 | 5985篇 |
1972年 | 5116篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Colour is the most widely used attribute in image retrieval and object recognition. A technique known as histogram intersection has been widely studied and is considered to be effective for color‐image indexing. The key issue of this algorithm is the selection of an appropriate color space and optimal quantization of the selected color space. The goal of this article is to measure the model performance in predicting human judgment in similarity measurement for various images, to explore the capability of the model with a wide set of color spaces, and to find the optimal quantization of the selected color spaces. Six color spaces and twelve quantization levels are involved in evaluating the performance of histogram intersection. The categorical judgment and rank order experiments were conducted to measure image similarity. The CIELAB color space was found to perform at least as good as or better than the other color spaces tested, and the ability to predict image similarity increased with the number of bins used in the histograms, for up to 512 bins (8 per channel). With more than 512 bins, further improvement was negligible for the image datasets used in this study. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 265–274, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20122 相似文献
992.
The use of a sequential linear complementarity problem (SLCP) algorithm for finding a global minimum of bilinear programming problem (BLP) or a concave quadratic program (CQP) is examined. The algorithm consists of solving a sequence of linear complementarity problems (LCP). A branch-and-bound method is also considered in this study. This algorithm is based on the reformulation of a BLP into an LCP with a linear function to minimize. Computational experience with small and medium scale BLPs and CQPs indicates that the SLCP algorithm is quite efficient in finding a global minimum (or at least a solution that is quite near the optimum), but it is, in general, unable to establish that such a solution has been found. An algorithm to find a lower-bound for the BLP can overcome this drawback in some cases. Furthermore the SLCP algorithm is shown to be robust and compares favorably with the branch-and-bound method and another alternative technique. 相似文献
993.
994.
E. L. Zil'berbrand A. A. Kozhushko V. I. Polozenko G. S. Pugachev A. B. Sinani 《Strength of Materials》1991,23(9):1007-1010
The process of interaction of a ductile projectile with a many times harder brittle target is analyzed in the 500–1000 m/sec range of velocities. The effect of hardness of the target and its fragmentation on the penetration depth is shown.Translated from Problemy Prochnosti, No. 9, pp. 60–62, September, 1991. 相似文献
995.
996.
997.
998.
999.
1000.
The electronic band structure of ZrO2 is calculated for the fluorite structure using the self-consistent augmented-plane-wave method in the muffin-tin approximation. The crystal charge density is then site decomposed by fitting Slater orbitals to the wave functions in the muffin tins. The resultant charge densities for Zr4+ and O2− are then used in the Gordon-Kim method to derive pair potentials, from which a number of structural, elastic, and thermodynamic properties are calculated and compared with experimental results and similar calculations for MgO. 相似文献