全文获取类型
收费全文 | 226428篇 |
免费 | 3491篇 |
国内免费 | 738篇 |
专业分类
电工技术 | 3900篇 |
综合类 | 376篇 |
化学工业 | 33388篇 |
金属工艺 | 8724篇 |
机械仪表 | 6647篇 |
建筑科学 | 5538篇 |
矿业工程 | 1433篇 |
能源动力 | 5551篇 |
轻工业 | 20676篇 |
水利工程 | 2482篇 |
石油天然气 | 4164篇 |
武器工业 | 17篇 |
无线电 | 24409篇 |
一般工业技术 | 44585篇 |
冶金工业 | 44663篇 |
原子能技术 | 5219篇 |
自动化技术 | 18885篇 |
出版年
2021年 | 2174篇 |
2020年 | 1627篇 |
2019年 | 1949篇 |
2018年 | 3386篇 |
2017年 | 3346篇 |
2016年 | 3563篇 |
2015年 | 2502篇 |
2014年 | 3885篇 |
2013年 | 10490篇 |
2012年 | 6201篇 |
2011年 | 8177篇 |
2010年 | 6575篇 |
2009年 | 7289篇 |
2008年 | 7520篇 |
2007年 | 7517篇 |
2006年 | 6321篇 |
2005年 | 5835篇 |
2004年 | 5425篇 |
2003年 | 5302篇 |
2002年 | 4899篇 |
2001年 | 4948篇 |
2000年 | 4854篇 |
1999年 | 5153篇 |
1998年 | 13627篇 |
1997年 | 9414篇 |
1996年 | 7334篇 |
1995年 | 5264篇 |
1994年 | 4744篇 |
1993年 | 4519篇 |
1992年 | 3395篇 |
1991年 | 3253篇 |
1990年 | 3022篇 |
1989年 | 3119篇 |
1988年 | 2987篇 |
1987年 | 2559篇 |
1986年 | 2451篇 |
1985年 | 2919篇 |
1984年 | 2673篇 |
1983年 | 2489篇 |
1982年 | 2207篇 |
1981年 | 2366篇 |
1980年 | 2207篇 |
1979年 | 2235篇 |
1978年 | 2220篇 |
1977年 | 2607篇 |
1976年 | 3713篇 |
1975年 | 1905篇 |
1974年 | 1841篇 |
1973年 | 1875篇 |
1972年 | 1484篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
Metal Science and Heat Treatment - 相似文献
152.
A mixed mode digital/analog special purpose VLSI hardware implementation of an associative memory with neural architecture is presented. The memory concept is based on a matrix architecture with binary storage elements holding the connection weights. To enhance the processing speed analog circuit techniques are applied to implement the algorithm for the association. To keep the memory density as high as possible two design strategies are considered. First, the number of transistors per storage element is kept to a minimum. In this paper a circuit technique that uses a single 6-transistor cell for weight storage and analog signal processing is proposed. Second, the device precision has been chosen to a moderate level to save area as much as possible. Since device mismatch limits the performance of analog circuits, the impact of device precision on the circuit performance is explicitly discussed. It is shown that the device precision limits the number of rows activated in parallel. Since the input vector as well as the output vector are considered to be sparsely coded it is concluded, that even for large matrices the proposed circuit technique is appropriate and ultra large scale integration with a large number of connection weights is feasible. 相似文献
153.
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
154.
155.
156.
157.
158.
An investigation into the effects of pressure (helium gas) on the isothermal fluid behavior includes: (1) the effect of pressure on the rate of melting and coking as evidenced by the rate constants k(melt) and k(coke); (2) the effect of pressure on the energies of activation of melting and coking; (3) the effects of pressure on the characteristic times; (4) the effects of pressure on the maximum isothermal fluidity. Results from the effects of pressure on k(melt) revealed that it was generally the high total sulfur, low nitrogen, low reactives/mineral matter ratio, medium rank coals which show the greatest increase in k(melt), whereas the highest rank coals show the least decrease in k(coke). The energies of activation of melting and coking were not significantly affected by pressure. The investigation also reveals increases or decreases in the respective times of softening, maximum fluidity, resolidification and total time of fluid behavior under isothermal pressurized conditions. There appears the possibility that these shifts may be rank dependent. Additionally, the lower rank coals show the largest relative increase in their fluidities when subjected to pressure. Empirical relationships were derived in order to quantitatively predict the maximum isothermal fluidity for most (fluid) coals at a given pressure. 相似文献
159.
160.
Emmerich M.T.M. Giannakoglou K.C. Naujoks B. 《Evolutionary Computation, IEEE Transactions on》2006,10(4):421-439
This paper presents and analyzes in detail an efficient search method based on evolutionary algorithms (EA) assisted by local Gaussian random field metamodels (GRFM). It is created for the use in optimization problems with one (or many) computationally expensive evaluation function(s). The role of GRFM is to predict objective function values for new candidate solutions by exploiting information recorded during previous evaluations. Moreover, GRFM are able to provide estimates of the confidence of their predictions. Predictions and their confidence intervals predicted by GRFM are used by the metamodel assisted EA. It selects the promising members in each generation and carries out exact, costly evaluations only for them. The extensive use of the uncertainty information of predictions for screening the candidate solutions makes it possible to significantly reduce the computational cost of singleand multiobjective EA. This is adequately demonstrated in this paper by means of mathematical test cases and a multipoint airfoil design in aerodynamics. 相似文献