全文获取类型
收费全文 | 32241篇 |
免费 | 2507篇 |
国内免费 | 1209篇 |
专业分类
电工技术 | 825篇 |
综合类 | 2007篇 |
化学工业 | 11409篇 |
金属工艺 | 1032篇 |
机械仪表 | 682篇 |
建筑科学 | 1941篇 |
矿业工程 | 839篇 |
能源动力 | 3123篇 |
轻工业 | 2309篇 |
水利工程 | 360篇 |
石油天然气 | 4860篇 |
武器工业 | 184篇 |
无线电 | 689篇 |
一般工业技术 | 3487篇 |
冶金工业 | 838篇 |
原子能技术 | 235篇 |
自动化技术 | 1137篇 |
出版年
2024年 | 129篇 |
2023年 | 526篇 |
2022年 | 1008篇 |
2021年 | 1200篇 |
2020年 | 1139篇 |
2019年 | 954篇 |
2018年 | 746篇 |
2017年 | 952篇 |
2016年 | 912篇 |
2015年 | 886篇 |
2014年 | 1604篇 |
2013年 | 1855篇 |
2012年 | 2268篇 |
2011年 | 2304篇 |
2010年 | 1840篇 |
2009年 | 1770篇 |
2008年 | 1541篇 |
2007年 | 1962篇 |
2006年 | 1803篇 |
2005年 | 1629篇 |
2004年 | 1376篇 |
2003年 | 1278篇 |
2002年 | 1030篇 |
2001年 | 902篇 |
2000年 | 780篇 |
1999年 | 685篇 |
1998年 | 559篇 |
1997年 | 453篇 |
1996年 | 384篇 |
1995年 | 296篇 |
1994年 | 260篇 |
1993年 | 205篇 |
1992年 | 154篇 |
1991年 | 122篇 |
1990年 | 109篇 |
1989年 | 68篇 |
1988年 | 46篇 |
1987年 | 36篇 |
1986年 | 37篇 |
1985年 | 24篇 |
1984年 | 21篇 |
1983年 | 11篇 |
1982年 | 15篇 |
1981年 | 5篇 |
1980年 | 12篇 |
1977年 | 4篇 |
1964年 | 5篇 |
1957年 | 3篇 |
1956年 | 3篇 |
1951年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
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
102.
103.
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
104.
Shuya Liang Miaomiao Wang Jun Wang Guanzhi Chen 《Chembiochem : a European journal of chemical biology》2021,22(22):3184-3189
To overcome high toxicity, low bioavailability and poor water solubility of chemotherapeutics, a variety of drug carriers have been designed. However, most carriers are severely limited by low drug loading capacity and adverse side effects. Here, a new type of metal-drug nanoparticles (MDNs) was designed and synthesized. The MDNs self-assembled with Fe(III) ions and drug molecules through coordination, resulting in nanoparticles with high drug loading. To assist systemic delivery and prolong circulation time, the obtained MDNs were camouflaged with red blood cell (RBCs) membranes (RBCs@Fe-DOX MDNs) to improve their stability and dispersity. The RBCs@Fe-DOX MDNs presented pH-responsive release functionalities, resulting in drug release accelerated in acidic tumor microenvironments. The outstanding in vitro and in vivo antitumor therapeutic outcome was realized by RBCs@Fe-DOX MDNs. This study provides an innovative design guideline for chemotherapy and demonstrates the great capacity of nanomaterials in anticancer treatments. 相似文献
105.
106.
107.
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
108.
109.
分析并列举了离子交换膜在使用过程中鼓泡的原因,阳极液质量浓度;pH值;阴极液质量浓度;电流密度;开停车及盐水质量等因素都可以造成膜鼓泡,形成针孔。提出了相应的预防措施。 相似文献
110.
我国烧碱生产技术概况 总被引:2,自引:0,他引:2
介绍了我国氯碱行业近几年来的发展情况:分析了我国烧碱生产的工艺技术现状。指出了为缩短与世界先进国家的差距需要加快开发关键设备和高性能的离子膜,加强管理。 相似文献