全文获取类型
收费全文 | 13699篇 |
免费 | 988篇 |
国内免费 | 735篇 |
专业分类
电工技术 | 211篇 |
综合类 | 988篇 |
化学工业 | 2726篇 |
金属工艺 | 806篇 |
机械仪表 | 380篇 |
建筑科学 | 615篇 |
矿业工程 | 711篇 |
能源动力 | 609篇 |
轻工业 | 708篇 |
水利工程 | 203篇 |
石油天然气 | 4414篇 |
武器工业 | 166篇 |
无线电 | 412篇 |
一般工业技术 | 879篇 |
冶金工业 | 626篇 |
原子能技术 | 114篇 |
自动化技术 | 854篇 |
出版年
2024年 | 56篇 |
2023年 | 183篇 |
2022年 | 353篇 |
2021年 | 390篇 |
2020年 | 442篇 |
2019年 | 334篇 |
2018年 | 311篇 |
2017年 | 394篇 |
2016年 | 407篇 |
2015年 | 389篇 |
2014年 | 647篇 |
2013年 | 916篇 |
2012年 | 812篇 |
2011年 | 904篇 |
2010年 | 688篇 |
2009年 | 731篇 |
2008年 | 626篇 |
2007年 | 762篇 |
2006年 | 849篇 |
2005年 | 734篇 |
2004年 | 602篇 |
2003年 | 588篇 |
2002年 | 536篇 |
2001年 | 475篇 |
2000年 | 377篇 |
1999年 | 341篇 |
1998年 | 290篇 |
1997年 | 245篇 |
1996年 | 208篇 |
1995年 | 180篇 |
1994年 | 123篇 |
1993年 | 87篇 |
1992年 | 68篇 |
1991年 | 61篇 |
1990年 | 75篇 |
1989年 | 52篇 |
1988年 | 25篇 |
1987年 | 29篇 |
1986年 | 26篇 |
1985年 | 17篇 |
1984年 | 17篇 |
1983年 | 8篇 |
1982年 | 12篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1977年 | 3篇 |
1964年 | 5篇 |
1957年 | 3篇 |
1956年 | 3篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
A complete mathematicalhumerical model is proposed, in order to simulate the performance characteristics of a novel concept of a drying heat pump based on the theory of minimum energy cyclcs. The drying heat pump involvcs vapour condensation in a Lava1 nozzle. removal of the liquid phase in a supersonic separator as well as compression of the working medium. which is superheared vapour. 相似文献
42.
Void formation and growth in a class of compressible solids 总被引:1,自引:0,他引:1
A new class of compressible elastic solids, which includes the Blatz-Ko material as a special case, is proposed. A closed-form solution is constructed and studied for a bifurcation problem modeling void formation in this class of compressible elastic solids. The relation between the void-formation condition and the material parameters is obtained analytically. An energy comparison of the void-formation deformation and the homogeneous expansion deformation is carried out. 相似文献
43.
华北盆地南缘大地电磁测深资料地质解释及大别山推覆体成因探讨 总被引:1,自引:0,他引:1
根据新近在大别山北麓获得的四条大地电磁测深剖面可以看出,该区地下介质的电性恃征具了明显的纵向上分层、横向上分块的特点。纵向上目上而下分为9个电性层.均有确定的地质属性。其中:第二和第九电性层为本区低阻标志层;第三和第六电性层为相对高阻层;第八电性层为高阻率电阻率高达1000Ω·m以上);第四、第五、第七电性层既有高阻、又有低阻分布.情况比较复杂。■向上的电性分块结构与本区的凸、凹相间的构造格局相对应。这四条大地测深剖面,均反映本区在5~15km深处有一个面积达15000km~2的连续低阻层(第九电性层).电阻率仅有1~3Ω·m。经分析,认为此低阻层可能是一个区域性的主滑脫面,是形成大別山推覆体由北向南的运动面. 相似文献
44.
45.
本文通过对带钢窄边线状裂纹缺陷的金相显微组织观察和扫描电镜与能谱分析,确定了带钢窄边线状裂纹缺陷的形成原因,并针对原因提出了相应的预防措施,有效地控制了带钢窄边线状裂纹缺陷的重复发生。 相似文献
46.
张立鉴 《电脑编程技巧与维护》2012,(14):61-62,65
针对数据库备份、数据库恢复的概念、技术原理和方法等方面进行了分析和探讨。事实证明,通过借助于网络信息技术、数据库处理技术、网络存储等技术有助于实现企业信息系统的数据库备份与恢复。 相似文献
47.
In recent years, there has been a considerable growth of application of group technology in cellular manufacturing. This has led to investigation of the primary cell formation problem (CFP), both in classical and soft-computing domain. Compared to more well-known and analytical techniques like mathematical programming which have been used rigorously to solve CFPs, heuristic approaches have yet gained the same level of acceptance. In the last decade we have seen some fruitful attempts to use evolutionary techniques like genetic algorithm (GA) and Ant Colony Optimization to find solutions of the CFP. The primary aim of this study is to investigate the applicability of a fine grain variant of the predator-prey GA (PPGA) in CFPs. The algorithm has been adapted to emphasize local selection strategy and to maintain a reasonable balance between prey and predator population, while avoiding premature convergence. The results show that the algorithm is competitive in identifying machine-part clusters from the initial CFP matrix with significantly less number of iterations. The algorithm scaled efficiently for large size problems with competitive performance. Optimal cluster identification is then followed by removal of the bottleneck elements to give a final solution with minimum inter-cluster transition cost. The results give considerable impetus to study similar NP-complete combinatorial problems using fine-grain GAs in future. 相似文献
48.
提出以视觉跟踪为基础并引入通信进行多机器人的编队控制方法,根据需要编写了一种新的通信协议,采用闭环l-Φ实现编队算法.这种多机器人编队控制避免了视觉系统的局限,能够更好地在复杂未知环境中协作完成任务,解决了编队控制的无反馈和实时性不高的问题,使得机器人能够准确迅速地进行跟踪和通信编队,一起顺利达到目标点.试验结果证明了该方法的有效性. 相似文献
49.
We present a simple and fast algorithm to test the thermodynamic stability and determine the necessary chemical environment for the production of a multiternary material, relative to competing phases and compounds formed from the constituent elements. If the material is found to be stable, the region of stability, in terms of the constituent elemental chemical potentials, is determined from the intersection points of hypersurfaces in an (n−1)-dimensional chemical potential space, where n is the number of atomic species in the material. The input required is the free energy of formation of the material itself, and that of all competing phases. Output consists of the result of the test of stability, the intersection points in the chemical potential space and the competing phase to which they relate, and, for two- and three-dimensional spaces, a file which may be used for visualization of the stability region. We specify the use of the program by applying it both to a ternary system and to a quaternary system. The algorithm automates essential analysis of the thermodynamic stability of a material. This analysis consists of a process which is lengthy for ternary materials, and becomes much more complicated when studying materials of four or more constituent elements, which have become of increased interest in recent years for technological applications such as energy harvesting and optoelectronics. The algorithm will therefore be of great benefit to the theoretical and computational study of such materials. 相似文献
50.