全文获取类型
收费全文 | 20822篇 |
免费 | 2139篇 |
国内免费 | 1389篇 |
专业分类
电工技术 | 1834篇 |
技术理论 | 1篇 |
综合类 | 2716篇 |
化学工业 | 3387篇 |
金属工艺 | 644篇 |
机械仪表 | 1198篇 |
建筑科学 | 2113篇 |
矿业工程 | 871篇 |
能源动力 | 993篇 |
轻工业 | 1448篇 |
水利工程 | 1015篇 |
石油天然气 | 1820篇 |
武器工业 | 238篇 |
无线电 | 960篇 |
一般工业技术 | 1627篇 |
冶金工业 | 865篇 |
原子能技术 | 345篇 |
自动化技术 | 2275篇 |
出版年
2024年 | 67篇 |
2023年 | 221篇 |
2022年 | 431篇 |
2021年 | 523篇 |
2020年 | 573篇 |
2019年 | 550篇 |
2018年 | 490篇 |
2017年 | 601篇 |
2016年 | 743篇 |
2015年 | 729篇 |
2014年 | 1061篇 |
2013年 | 1214篇 |
2012年 | 1456篇 |
2011年 | 1497篇 |
2010年 | 1145篇 |
2009年 | 1173篇 |
2008年 | 1105篇 |
2007年 | 1493篇 |
2006年 | 1308篇 |
2005年 | 1191篇 |
2004年 | 981篇 |
2003年 | 906篇 |
2002年 | 790篇 |
2001年 | 687篇 |
2000年 | 578篇 |
1999年 | 512篇 |
1998年 | 417篇 |
1997年 | 379篇 |
1996年 | 285篇 |
1995年 | 261篇 |
1994年 | 197篇 |
1993年 | 158篇 |
1992年 | 147篇 |
1991年 | 113篇 |
1990年 | 82篇 |
1989年 | 82篇 |
1988年 | 70篇 |
1987年 | 42篇 |
1986年 | 16篇 |
1985年 | 17篇 |
1984年 | 6篇 |
1983年 | 11篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1977年 | 3篇 |
1959年 | 2篇 |
1956年 | 2篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
101.
基于BP网络的设备状态分类器的设计 总被引:4,自引:0,他引:4
介绍了在Matlab6.5的神经网络工具箱中,开发基于BP网络的设备状态分类嚣的方法和要点,给出了仿真结果,并以实例验证了该分类器在设备故障诊断中的有效性。 相似文献
102.
103.
Solubility of dimethyl-2,6-naphthalene dicarboxylate in acetic acid, N,N-dimethylfonnamide, N,N-dimethyl acetamide, dimethyl sulphoxide, and N-methyl-2-ketopyrrolidine were determined using a dynamic method. The measured systems were correlated by UNIFAC group contribution method. A new main group (aromatic ester, ACCOO) was defined to express the activity coefficients of the aromatic ester. New interaction parameters of the ACCOO group were expressed as the first-order function of temperature and were determined from the experimental data. The calculated results for the new interaction parameters were satisfactory. The measured systems were also correlated with the Wilson and 2-h models, and the results were compared with those of the UNIFAC model. 相似文献
104.
Jung-Han Kimn Marcus Sarkis 《Computer Methods in Applied Mechanics and Engineering》2007,196(8):1507-1514
Overlapping balancing domain decomposition methods and their combination with restricted additive Schwarz methods are proposed for the Helmholtz equation. These new methods also extend previous work on non-overlapping balancing domain decomposition methods toward simplifying their coarse problems and local solvers. They also extend restricted Schwarz methods, originally designed to overlapping domain decomposition and Dirichlet local solvers, to the case of non-overlapping domain decomposition and/or Neumann and Sommerfeld local solvers. Finally, we introduce coarse spaces based on partitions of unity and planes waves, and show how oblique projection coarse problems can be designed from restricted additive Schwarz methods. Numerical tests are presented. 相似文献
105.
压裂预处理技术的现场实施与评价 总被引:5,自引:1,他引:4
通常,压裂目的层的储层特征、物性及生产史差异较大,为保证压裂施工成功并取得较好的压裂效果,进行油层预处理十分必要。介绍了酸预处理、前置液氮预处理、柴油十互溶剂混合液预处理3种技术,阐述了各种预处理方法的目的及适应性,介绍了各种预处理技术在现场取得的效果,提出了各种预处理技术的适用条件及常用做法。 相似文献
106.
报道了用二 (2 乙基己基 )二硫代磷酸为萃取剂 ,以正庚烷为稀释剂萃取铟的热力学研究。在In2 (SO4 ) 3+Na2 SO4 +D2 EHDTPA +n C7H1 6 +H2 O体系中 ,在温度 2 78.15~ 3 0 3 .15K和离子强度 0 .1~ 2 .0mol·kg- 1 范围内 ,以Na2 SO4 为支持电解质 ,测定了萃取平衡水相中In3+浓度和pH值。计算了萃取反应的标准平衡常数K0 ,并得到经验公式logK0 =43 .93 -5 3 68.5 4 T -0 .0 699T ,同时计算了萃取反应的其他热力学量 ,并指出了焓和熵都是此萃取过程的推动力 相似文献
107.
A procedure based on K?tter’s equation is developed for the evaluation of bearing capacity factor Nγ with Terzaghi’s mechanism. Application of K?tter’s equation makes the analysis statically determinate, in which the unique failure surface is identified using force equilibrium conditions. The computed Nγ values are found to be higher than Terzaghi’s value in the range 0.25–20%, with a diverging trend for higher values of angle of soil internal friction. A fairly good agreement is observed with other solutions which are based on finite difference coupled with associated flow rule, limit analysis, and limit equilibrium. Finally, the comparison with available experimental results vis-à-vis other solutions shows that, computed Nγ values are capable of making a reasonably good prediction. 相似文献
108.
提出了一个新的矩形非协调混合元格式,把它应用于Stokes问题的数值逼近,得到了最优的误差估计. 相似文献
109.
110.
Pareto multi-criteria decision making 总被引:1,自引:0,他引:1
The paper concerns design governed by multiple objective criteria, which are conflicting in the sense of competing for common resources to achieve variously different performance objectives (financial, functional, environmental, esthetical, etc.). A multi-criteria decision making (MCDM) strategy is proposed that employs a tradeoff-analysis technique to identify compromise designs for which the competing criteria are mutually satisfied in a Pareto-optimal sense. The MCDM strategy is initially developed for the case of design governed by n = 2 objective criteria. It is then extended to design governed by n > 2 objective criteria, by introducing the concept of primary and aggregate criteria. It is proved that, from among the theoretically infinite number of feasible designs forming the Pareto front for a design problem governed by n independent objective criteria, there exists a unique Pareto-compromise design that represents a mutually agreeable tradeoff between all n criteria. This remarkable result is illustrated for a flexural plate design governed by n = 2 criteria, a bridge maintenance-intervention protocol design governed by n = 3 criteria, and a media centre envelop design governed by n = 11 criteria. 相似文献