全文获取类型
收费全文 | 241263篇 |
免费 | 2641篇 |
国内免费 | 428篇 |
专业分类
电工技术 | 4299篇 |
综合类 | 259篇 |
化学工业 | 39370篇 |
金属工艺 | 9379篇 |
机械仪表 | 7396篇 |
建筑科学 | 5444篇 |
矿业工程 | 1391篇 |
能源动力 | 5152篇 |
轻工业 | 24812篇 |
水利工程 | 2485篇 |
石油天然气 | 5092篇 |
武器工业 | 32篇 |
无线电 | 25047篇 |
一般工业技术 | 44773篇 |
冶金工业 | 45344篇 |
原子能技术 | 5958篇 |
自动化技术 | 18099篇 |
出版年
2021年 | 2108篇 |
2019年 | 2018篇 |
2018年 | 3488篇 |
2017年 | 3426篇 |
2016年 | 3690篇 |
2015年 | 2246篇 |
2014年 | 3901篇 |
2013年 | 10184篇 |
2012年 | 6147篇 |
2011年 | 8297篇 |
2010年 | 6546篇 |
2009年 | 7232篇 |
2008年 | 7583篇 |
2007年 | 7712篇 |
2006年 | 6887篇 |
2005年 | 6045篇 |
2004年 | 5815篇 |
2003年 | 5598篇 |
2002年 | 5673篇 |
2001年 | 5560篇 |
2000年 | 5382篇 |
1999年 | 5302篇 |
1998年 | 12570篇 |
1997年 | 8895篇 |
1996年 | 6856篇 |
1995年 | 5329篇 |
1994年 | 4735篇 |
1993年 | 4624篇 |
1992年 | 3667篇 |
1991年 | 3387篇 |
1990年 | 3592篇 |
1989年 | 3472篇 |
1988年 | 3303篇 |
1987年 | 2895篇 |
1986年 | 2932篇 |
1985年 | 3373篇 |
1984年 | 3219篇 |
1983年 | 2892篇 |
1982年 | 2738篇 |
1981年 | 2821篇 |
1980年 | 2719篇 |
1979年 | 2624篇 |
1978年 | 2684篇 |
1977年 | 2948篇 |
1976年 | 3805篇 |
1975年 | 2368篇 |
1974年 | 2242篇 |
1973年 | 2376篇 |
1972年 | 1970篇 |
1971年 | 1858篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Douay M. Xie W.X. Taunay T. Bernage P. Niay P. Cordier P. Poumellec B. Dong L. Bayon J.F. Poignant H. Delevaque E. 《Lightwave Technology, Journal of》1997,15(8):1329-1342
A comprehensive survey of photosensitivity in silica glasses and optical fiber is reviewed. Recent work on understanding the mechanisms contributing to germanium or aluminum doped fiber photosensitivity is discussed within the framework of photoelastic densification models 相似文献
42.
The capacitive idling converters derived from the Cuk, SEPIC, Zeta, and flyback topologies allow soft commutation of power switches without the need for additional circuitry, making it possible to increase the switching frequency while maintaining high efficiency 相似文献
43.
We present the design of E-kernel, an embedding kernel on the Victor V256 message-passing partitionable multiprocessor, developed for the support of program mapping and network reconfiguration. E-kernel supports the embedding of a new network topology onto Victor's 2D mesh and also the embedding of a task graph onto the 2D mesh network or the reconfigured network. In the current implementation, the reconfigured network can be a line or an even-size ring, and the task graphs meshes or tori of a variety of dimensions and shapes or graphs with similar topologies. For application programs having these task graph topologies and that are designed according to the communication model of E-kernel, they can be run without any change on partitions connected by the 2D mesh, line, or ring. Further, E-kernel attempts the communication optimization of these programs on the different networks automatically, thus making both the network topology and the communication optimization attempt completely transparent to the application programs. Many of the embeddings used in E-kernel are optimal or asymptotically optimal (with respect to minimum dilation cost). The implementation of E-kernel translated some of the many theoretical results in graph embeddings into practical tools for program mapping and network reconfiguration in a parallel system. E-kernel is functional on Victor V256. Measurements of E-kernel's performance on V256 are also included 相似文献
44.
This research was supported under project No. 6.02.02/128-93 as part of the state scientific-technical program on future information
technologies and systems by the Ukrainian State Committee, of Science and Technology. 相似文献
45.
46.
47.
F. Cioffi E. M. Cohen Richard Badick 《Drug development and industrial pharmacy》1993,19(14):1741-1746
Carstensen and Rhodes1 have suggested that when, in stability programs, assays cannot be performed immediately after the protocol-designated storage time, then freezing them until such a time when assays can be performed would be a reasonable manner to retain the protocol schedule. They caution, however, that such a procedure may not be valid for dissolution data. The article to follow deals with real-time data showing that such a process is feasible for Nalidixic Acid tablets (and presumably for other tablets as well), and that, furthermore, the dissolution pattern would seem to be “frozen” as well. 相似文献
48.
An extended logistic model with a varying asymptotic upper bound for long-range peak demand forecasting is described. The model has been applied to a typical fast growing system, the Saudi Consolidated Electric Company. The forecasts are compared with actual demands and with those obtained from classical forecasting methods. The model gave relatively accurate peak demand forecasts compared with other classical methods. The model with a single load observation is capable of producing several peak demand forecasts corresponding to different levels of maximum temperature and various levels of social activity. The forecasts produced by the model were also stable irrespective of the length of the ex-post simulation period 相似文献
49.
E. Smith 《Journal of Materials Science》1993,28(4):880-884
The criterion for crack growth instability in an elastic-softening material that is subjected to displacement control loading conditions is examined. A theoretical analysis of the model of a solid containing two symmetrically situated deep cracks and with tensile loading of the remaining ligament, defines the criterion for crack growth instability. The criterion is expressed in terms of the material's softening characteristics and the solid's geometrical parameters. The analysis covers the complete spectrum of material behaviour from the case where the softening zone is very small to the case where instability does not occur until the softening zone traverses the ligament between the crack tips. 相似文献
50.