全文获取类型
收费全文 | 29937篇 |
免费 | 3572篇 |
国内免费 | 2511篇 |
专业分类
电工技术 | 2236篇 |
技术理论 | 1篇 |
综合类 | 3388篇 |
化学工业 | 966篇 |
金属工艺 | 3465篇 |
机械仪表 | 1623篇 |
建筑科学 | 1686篇 |
矿业工程 | 564篇 |
能源动力 | 671篇 |
轻工业 | 444篇 |
水利工程 | 629篇 |
石油天然气 | 607篇 |
武器工业 | 141篇 |
无线电 | 3392篇 |
一般工业技术 | 2806篇 |
冶金工业 | 1436篇 |
原子能技术 | 258篇 |
自动化技术 | 11707篇 |
出版年
2024年 | 79篇 |
2023年 | 266篇 |
2022年 | 461篇 |
2021年 | 494篇 |
2020年 | 699篇 |
2019年 | 635篇 |
2018年 | 641篇 |
2017年 | 908篇 |
2016年 | 1078篇 |
2015年 | 1128篇 |
2014年 | 1977篇 |
2013年 | 2082篇 |
2012年 | 2312篇 |
2011年 | 2330篇 |
2010年 | 1940篇 |
2009年 | 2176篇 |
2008年 | 2081篇 |
2007年 | 2330篇 |
2006年 | 2034篇 |
2005年 | 1718篇 |
2004年 | 1426篇 |
2003年 | 1258篇 |
2002年 | 1027篇 |
2001年 | 973篇 |
2000年 | 734篇 |
1999年 | 604篇 |
1998年 | 460篇 |
1997年 | 391篇 |
1996年 | 303篇 |
1995年 | 264篇 |
1994年 | 219篇 |
1993年 | 179篇 |
1992年 | 146篇 |
1991年 | 120篇 |
1990年 | 109篇 |
1989年 | 113篇 |
1988年 | 69篇 |
1987年 | 44篇 |
1986年 | 25篇 |
1985年 | 20篇 |
1984年 | 17篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1981年 | 14篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1964年 | 8篇 |
1963年 | 9篇 |
1961年 | 8篇 |
1955年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
91.
92.
Fadwa T. Eljack Ahmed F. Abdelhady Mario R. Eden Frederico B. Gabriel Xiaoyun Qin Mahmoud M. El-Halwagi 《Computers & Chemical Engineering》2005,29(11-12):2304
Decoupling the constitutive equations from the balance and constraint equations allows for reformulating a conventional forward problem into two reverse problems. The first reverse problem is the reverse of a simulation problem, where the process model is solved in terms of the constitutive (synthesis/design) variables instead of the process variables, thus providing the synthesis/design targets. The second reverse problem (reverse property prediction) solves the constitutive equations to identify unit operations, operating conditions and/or products by matching the synthesis/design targets. Visualization of the problem is achieved by employing recently developed property clustering techniques, which allows a high-dimensional problem to be visualized in two or three dimensions. The clusters by definition satisfy intra-stream and inter-stream conservation through linear “mixing” rules, which allows for the development of consistent additive rules along with their ternary representation. 相似文献
93.
94.
95.
Chenn-Jung Huang Wei-Kuang Lai Sheng-Yu Hsiao Hao-Yu Liu Rui-Lin Luo 《International Journal of Wireless Information Networks》2004,11(3):131-146
In this paper, a routing protocol which utilizes the characteristics of Bluetooth technology is proposed for Bluetooth-based mobile ad hoc networks. The routing tables are maintained in the master devices and the routing zone radius for each table is adjusted dynamically by using evolving fuzzy neural networks. Observing there exists some useless routing packets which are helpless to build the routing path and increase the network loads in the existing ad hoc routing protocols, we selectively use multiple unicasts or one broadcast when the destination device is out of the routing zone radius coverage of the routing table. The simulation results show that the dynamic adjustment of the routing table size in each master device results in much less reply time of routing request, fewer request packets and useless packets compared with two representative protocols, Zone Routing Protocol and Dynamic Source Routing. 相似文献
96.
The Role of Network Topologies in the Optical Core of IP-over-WDM Networks with Static Wavelength Routing 总被引:3,自引:0,他引:3
Freire Mário M. Rodrigues Joel J.P.C. Coelho Rui M.F. 《Telecommunication Systems》2003,24(2-4):111-122
In this paper, we present a performance analysis of network topologies for the optical core of IP-over-WDM networks with static wavelength routing. The performance analysis is focused on regular degree four topologies, and, for comparison purposes, degree three topologies are also considered. It is shown that the increase of the nodal degree from three (degree three topology with smallest diameter) to four (degree four topology with smallest diameter) improves the network performance if a larger number of wavelengths per link is available. However, the influence of wavelength interchange on the nodal degree gain is small. The performance of regular degree four topologies with smallest diameter is also compared with the performance of mesh–torus topologies (which are also degree four topologies), and it is shown that the blocking probability of degree four topologies with smallest diameter is about two orders of magnitude lower than the blocking probability of mesh–torus topologies. It is also presented a performance comparison of WDM-based networks with nodal degrees ranging from two to five and it is shown that the increase of the nodal degree from two to three leads to high nodal degree gains, while de increase of the nodal degree from four to five leads to low nodal degree gains. These results show that degree three and degree four topologies are very attractive for use in the optical core of IP-over-WDM networks. 相似文献
97.
Children's perceived attachments with parents, and family cohesion and adaptability were examined as predictors, mediators, and moderators in the parental problem drinking-child outcomes link. A total of 216 6- to 12-year-olds (110 boys, 106 girls) participated. Data were obtained from children and their mothers, fathers, and teachers. A higher level of family cohesion and adaptability functioned as (a) a robust protective factor against adjustment and cognitive difficulties otherwise associated with problem drinking and (b) a mediator of adjustment problems. Children's perceptions of attachments to mothers and fathers were consistent predictors of behavioral, social, and cognitive problems and further moderated relations between problem drinking and child functioning. The results support that child-parent and family functioning variables act as either pathways and/or vulnerability and protective factors for children exposed to a high-risk environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
98.
99.
一个改进的单抓钩周期性排序模型及其在自动化学处理线中的应用 总被引:1,自引:0,他引:1
计算机控制的抓钩广泛用于自动化学处理线的工件的运送。抓钩的排序直接影响系统的生产率,抓钩排序的目标是对运送进行排序以极大化生产率。当某工序处理时间非常长时,该工序成为瓶颈。为了去除该瓶颈,系统可以为该工序设计多个处理槽,这称为“多重处理槽”问题。本文提出一个改进的混合整数规划模型以求解有“多重处理槽”的单抓钩周期性排序问题的最优解。实例表明所提出的方法是有效的。 相似文献
100.