全文获取类型
收费全文 | 25284篇 |
免费 | 2961篇 |
国内免费 | 1805篇 |
专业分类
电工技术 | 1794篇 |
综合类 | 3096篇 |
化学工业 | 3666篇 |
金属工艺 | 1366篇 |
机械仪表 | 1949篇 |
建筑科学 | 3767篇 |
矿业工程 | 1012篇 |
能源动力 | 1417篇 |
轻工业 | 812篇 |
水利工程 | 1609篇 |
石油天然气 | 1166篇 |
武器工业 | 313篇 |
无线电 | 2144篇 |
一般工业技术 | 2677篇 |
冶金工业 | 772篇 |
原子能技术 | 614篇 |
自动化技术 | 1876篇 |
出版年
2024年 | 93篇 |
2023年 | 327篇 |
2022年 | 664篇 |
2021年 | 730篇 |
2020年 | 859篇 |
2019年 | 727篇 |
2018年 | 704篇 |
2017年 | 986篇 |
2016年 | 963篇 |
2015年 | 1051篇 |
2014年 | 1415篇 |
2013年 | 1687篇 |
2012年 | 1881篇 |
2011年 | 1941篇 |
2010年 | 1459篇 |
2009年 | 1522篇 |
2008年 | 1472篇 |
2007年 | 1731篇 |
2006年 | 1504篇 |
2005年 | 1268篇 |
2004年 | 1060篇 |
2003年 | 875篇 |
2002年 | 768篇 |
2001年 | 659篇 |
2000年 | 593篇 |
1999年 | 478篇 |
1998年 | 404篇 |
1997年 | 380篇 |
1996年 | 330篇 |
1995年 | 288篇 |
1994年 | 251篇 |
1993年 | 170篇 |
1992年 | 157篇 |
1991年 | 137篇 |
1990年 | 139篇 |
1989年 | 100篇 |
1988年 | 75篇 |
1987年 | 47篇 |
1986年 | 38篇 |
1985年 | 29篇 |
1984年 | 22篇 |
1983年 | 6篇 |
1982年 | 16篇 |
1981年 | 9篇 |
1980年 | 14篇 |
1979年 | 3篇 |
1973年 | 2篇 |
1965年 | 2篇 |
1959年 | 3篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
91.
The influence of irreversibility of finite-rate heat transfer on the performance of an absorption refrigerator is investigated using an endoreversible cycle model with continuous flow. The cooling rate is adopted as an objective function for refrigerator optimization. The maximum cooling rate and the corresponding coefficient of performance are derived. The optimal performance with respect to heat transfer areas of the refrigerator is analysed. In addition, certain significant conclusions are reached. 相似文献
92.
93.
P. T. Tsilingiris 《国际能源研究杂志》1991,15(9):723-730
The paper describes the calculation of the beam solar radiation transmission across the uniform salinity upper convecting zone (UCZ) and the salinity stratified gradient zone (GZ), when the extinction coefficient is not only wavelength but also salinity-concentration dependent, assuming that the effect of scattering to be negligible. The results are useful in determining the effects of dissolved salt ions on pure water transmission, at least according to the existing measured data in the literature. 相似文献
94.
Y. C. Wu Darning Feng W. F. Koch 《Journal of research of the National Institute of Standards and Technology》1991,96(6):757-762
Ionic interactions in the two systems NaCl-HEPES (N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid) and NaCl-MOPSO (3-(N-Morpholino)-2-hydroxypropanesulfonic acid) have been studied in terms of their mutual influence on the respective activity coefficients of each component. Activity coefficients for each component of the two systems and for corresponding buffers are calculated from emf measurements of solutions containing NaCl, the aminosulfonic acid, and its conjugate base in a NalSE/solution/AgCl-Ag cell at 5, 15, 25, and 37 °C. 相似文献
95.
A compact lumped‐element equivalent circuit model of two‐layer integrated spiral inductors on silicon substrates is developed in this article. Based on this proposed model, excellent agreements are achieved between the measured and simulated S‐parameters for different inductors. Also, both self‐ and mutual inductances of two‐layer inductors are accurately extracted, and their overall performances are understood clearly. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 148–153, 2003. 相似文献
96.
A computer model was extended and adapted to simulate the hygrothermal behavior of building envelope-wood components. The model was used to predict moisture movement in wood planks forming the decks of nonvented flat roofs insulated with cellulose. The gradient of water potential was considered as the driving force for moisture movement in wood. The model required the determination of convective heat- and mass-transfer coefficients, the sorption curves, the effective water conductivity for different wood species, and the hygrothermal conditions within the assembly to characterize the mass-conservation equation. Once these parameters were integrated in the computer model, this approach was then validated by carrying a simulation of the drying process of wood planks using experimental data from a large-scale test. 相似文献
97.
本文针对辽河东部凹陷油燕沟中生界火山岩的具体特征,采用纵波波速的比值——“龟裂系数”裂缝分析法[1,2,3],研究了火山岩裂隙发育程度。综合龟裂系数裂缝分析及其他方法发现,该区中生界火山岩有效储集层的测井相特征主要表现为低密度、低中子、高声波时差和高伽马值等特征。此法的关键在于根据不同火山岩的岩性,选用合适的岩石骨架参数,在此基础上利用测井约束地震反演计算火山岩的层速度,进而计算出龟裂系数,然后根据已钻至火山岩井孔的测井相特征编制出火山岩预测厚度图。 相似文献
98.
99.
100.
本文用不同的测试技术和方法测定了锗酸铋(BGO)单晶的比热(300~800K)热膨胀系数(100~1100K)和导温系数(140~700K),进而导出了 BGO 单晶不同温度下的导热系数、定容比热、德拜温度和格虑内森数。本文还对 BGO 单晶热物理性质的变化规律作了理论解释。 相似文献