全文获取类型
收费全文 | 34439篇 |
免费 | 2945篇 |
国内免费 | 2150篇 |
专业分类
电工技术 | 4296篇 |
技术理论 | 1篇 |
综合类 | 3784篇 |
化学工业 | 1492篇 |
金属工艺 | 1207篇 |
机械仪表 | 3269篇 |
建筑科学 | 1267篇 |
矿业工程 | 1116篇 |
能源动力 | 769篇 |
轻工业 | 824篇 |
水利工程 | 952篇 |
石油天然气 | 811篇 |
武器工业 | 636篇 |
无线电 | 2974篇 |
一般工业技术 | 2108篇 |
冶金工业 | 1309篇 |
原子能技术 | 129篇 |
自动化技术 | 12590篇 |
出版年
2024年 | 105篇 |
2023年 | 299篇 |
2022年 | 566篇 |
2021年 | 711篇 |
2020年 | 960篇 |
2019年 | 713篇 |
2018年 | 638篇 |
2017年 | 933篇 |
2016年 | 1021篇 |
2015年 | 1247篇 |
2014年 | 2178篇 |
2013年 | 2233篇 |
2012年 | 2513篇 |
2011年 | 2561篇 |
2010年 | 1987篇 |
2009年 | 1984篇 |
2008年 | 2028篇 |
2007年 | 2383篇 |
2006年 | 2117篇 |
2005年 | 1906篇 |
2004年 | 1545篇 |
2003年 | 1406篇 |
2002年 | 1206篇 |
2001年 | 1046篇 |
2000年 | 852篇 |
1999年 | 698篇 |
1998年 | 530篇 |
1997年 | 520篇 |
1996年 | 433篇 |
1995年 | 359篇 |
1994年 | 355篇 |
1993年 | 241篇 |
1992年 | 231篇 |
1991年 | 184篇 |
1990年 | 126篇 |
1989年 | 128篇 |
1988年 | 117篇 |
1987年 | 67篇 |
1986年 | 66篇 |
1985年 | 44篇 |
1984年 | 59篇 |
1983年 | 37篇 |
1982年 | 40篇 |
1981年 | 24篇 |
1980年 | 25篇 |
1979年 | 31篇 |
1978年 | 11篇 |
1977年 | 21篇 |
1976年 | 15篇 |
1975年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
勘探地球物理技术最新进展——2002年SEG年会综述Ⅱ:解释与压力预测 总被引:4,自引:4,他引:0
孙建国 《勘探地球物理进展》2003,26(2):148-159
根据2002年SEG年会部分论文编译而成,包括解释技术和压力预测技术。概要性地介绍了偏移成像技术;新属性技术;自动地震相分析技术;油气检测技术;储层反演技术和2种实用的压力预测技术。 相似文献
82.
天津钢铁有限公司引进了瑞士Concast公司6机6流方、圆坯连铸机及相关技术,文章简要介绍了Concast连铸机的自动控制系统的特点和功能。 相似文献
83.
鲜飞 《现代表面贴装资讯》2006,5(6):58-61
SMT设备要达到最大的产量,必须要考虑生产线的效率。点胶机是SMT生产线中的重要设备,因此提高点胶机的生产效率具有十分重要的意义。本文以CAMALOT 5000系统为例,介绍了点胶机离线编程软件的设计与开发中的思想、方法和经验,本文着重探讨了坐标数据的处理和转换,同时针对基于点胶系统优化的TSP问题进行了分析和研究,对程序优化进行了系统分析设计,并编程实现了基本方案。最后在CAMALOT 5000系统上使用本解决方案,大幅度提高了生产效率,证明了本解决方案的优越性和高效性,也为其他SMT设备的离线编程软件的设计提供了一种可参考的思路。 相似文献
84.
武钢第二炼钢厂连铸坯喷号机自动控制系统 总被引:1,自引:0,他引:1
对武钢第二炼钢厂连铸坯喷号机自动化控制景统配置、网络通讯、伺服控制系统进行了阐述;经运行考验证明系统性能提高、稳定可靠。 相似文献
85.
介绍光电被动感应控制开关模块工作原理,研究开发了一种基于被动感应控制原理的自动冲水控制装置,总结比较了主动感应控制与被动感应控制的优缺点及其应用特点。 相似文献
86.
A globally convergent algorithm for transportation continuous network design problem 总被引:2,自引:0,他引:2
The continuous network design problem (CNDP) is characterized by a bilevel programming model, in which the upper level problem
is generally to minimize the total system cost under limited expenditure, while at the lower level the network users make
choices with regard to route conditions following the user equilibrium principle. In this paper, the bilevel programming model
for CNDP is transformed into a single level convex programming problem by virtue of an optimal-value function tool and the
relationship between System Optimum (SO) and User Equilibrium (UE). By exploring the inherent nature of the CNDP, the optimal-value
function for the lower level user equilibrium problem is proved to be continuously differentiable and its derivative in link
capacity enhancement can be obtained efficiently by implementing user equilibrium assignment subroutine. However, the reaction
(or response) function between the upper and lower level problem is implicit and its gradient is difficult to obtain. Although,
here we approximately express the gradient with the difference concept at each iteration, based on the method of successive
averages (MSA), we propose a globally convergent algorithm to solve the single level convex programming problem. Comparing
with widely used heuristic algorithms, such as sensitivity analysis based (SAB) method, the proposed algorithm needs not strong
hypothesis conditions and complex computation for the inverse matrix. Finally, a numerical example is presented to compare
the proposed method with some existing algorithms. 相似文献
87.
The molten iron allocation problem (MIAP) is to allocate molten iron from blast furnaces to steel-making furnaces. The allocation needs to observe the release times of the molten iron defined by the draining plan of the blast furnaces and the transport time between the iron-making and steel-making stages. Time window constraints for processing the molten iron must be satisfied to avoid freezing. The objective is to find a schedule with minimum total weighted completion time. This objective reflects the practical consideration of improving steel-making efficiency and reducing operation cost caused by the need for reheating. Such a problem can be viewed as a parallel machine scheduling problem with time windows which is known to be NP-hard. In this paper, we first formulate the molten iron allocation problem as an integer programming model and then reformulate it as a set partitioning model by applying the Dantzig–Wolfe decomposition. We solve the problem using a column generation-based branch-and-price algorithm. Since the subproblem of column generation is still NP-hard, we propose a state-space relaxation-based dynamic programming algorithm for the subproblem. Computational experiments demonstrate that the proposed algorithm is capable of solving problems with up to 100 jobs to optimality within a reasonable computation time. 相似文献
88.
除沫器自动冲洗装置的设计及应用 总被引:1,自引:0,他引:1
本文针对Ⅰ效二次蒸汽折流板式除沫器需定时冲洗的实际情况,设计了一套冲洗间隔灵活可调的自动冲洗装置,该装置结构简单、工作可靠,易于实现,有一定的实用价值。 相似文献
89.
Saumya K. Debray 《Software》1993,23(12):1337-1360
Janus is a language designed for distributed constraint programming. This paper describes QD-Janus, a sequential implementation of Janus in Prolog. The compiler uses a number of novel analyses and optimizations to improve the performance of the system. The choice of Prolog as the target language for a compiler, although unusual, is motivated by the following: (i) the semantic gap between Janus and Prolog is much smaller than that between Janus and, say, C or machine language—this simplifies the compilation process significantly, and makes it possible to develop a system with reasonable performance fairly quickly; (ii) recent progress in Prolog implementation techniques, and the development of Prolog systems whose speeds are comparable to those of imperative languages, indicates that the translation to Prolog need not entail a significant performance loss compared to native code compilers; and (iii) compilation to Prolog can benefit immediately from a significant body of work on, and implementations of, parallel Prolog systems. Our experience indicates that translation of logic programming languages to Prolog, accompanied by the development of good program analysis and optimization tools, is an effective way to quickly develop flexible and portable implementations with good performance and low cost. 相似文献
90.
Qidong Cao Mark A. Mcknew 《International Journal of Flexible Manufacturing Systems》1994,6(2):155-172
A new optimization model is discussed for the design of cellular manufacturing systems. It is based on an integer programming formulation that updates some other models by eliminating redundant machine assignment and cost coefficients dependent on cell configuration. To reduce computational burdens, a simplified integer programming model and a decomposition algorithm are proposed. Several computer solutions were performed to evaluate the performance of the new model. The computational results are discussed. 相似文献