全文获取类型
收费全文 | 354784篇 |
免费 | 86491篇 |
国内免费 | 59274篇 |
专业分类
电工技术 | 43375篇 |
技术理论 | 1篇 |
综合类 | 40418篇 |
化学工业 | 44571篇 |
金属工艺 | 36798篇 |
机械仪表 | 18934篇 |
建筑科学 | 25255篇 |
矿业工程 | 19996篇 |
能源动力 | 12767篇 |
轻工业 | 38904篇 |
水利工程 | 12521篇 |
石油天然气 | 18601篇 |
武器工业 | 6027篇 |
无线电 | 47418篇 |
一般工业技术 | 43584篇 |
冶金工业 | 13370篇 |
原子能技术 | 3864篇 |
自动化技术 | 74145篇 |
出版年
2024年 | 3819篇 |
2023年 | 7657篇 |
2022年 | 12565篇 |
2021年 | 15599篇 |
2020年 | 15266篇 |
2019年 | 21679篇 |
2018年 | 23175篇 |
2017年 | 25368篇 |
2016年 | 24398篇 |
2015年 | 26662篇 |
2014年 | 27075篇 |
2013年 | 28362篇 |
2012年 | 30529篇 |
2011年 | 27668篇 |
2010年 | 25472篇 |
2009年 | 22376篇 |
2008年 | 20630篇 |
2007年 | 19734篇 |
2006年 | 16642篇 |
2005年 | 14351篇 |
2004年 | 14246篇 |
2003年 | 10715篇 |
2002年 | 10018篇 |
2001年 | 8951篇 |
2000年 | 7785篇 |
1999年 | 5666篇 |
1998年 | 4436篇 |
1997年 | 3906篇 |
1996年 | 3684篇 |
1995年 | 3714篇 |
1994年 | 3021篇 |
1993年 | 2790篇 |
1992年 | 2701篇 |
1991年 | 1965篇 |
1990年 | 1548篇 |
1989年 | 1450篇 |
1988年 | 1091篇 |
1987年 | 345篇 |
1986年 | 314篇 |
1985年 | 217篇 |
1984年 | 150篇 |
1983年 | 115篇 |
1982年 | 156篇 |
1981年 | 182篇 |
1980年 | 155篇 |
1976年 | 225篇 |
1975年 | 204篇 |
1972年 | 235篇 |
1971年 | 127篇 |
1960年 | 205篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
Z. S. Peng Z. Q. Hua Y. N. Li J. Di J. Ma Y. M. Chu W. N. Zhen Y. L. Yang H. J. Wang Z. X. Zhao 《Journal of Superconductivity》1998,11(6):749-754
Bi-based superconductors are of great interest in high-temperature superconductors. We describe what is believed to be the first synthesis of these materials using the Pechini process, a low-temperature synthetic method that often yields inorganic oxide of excellent phase purity and well-controlled stoichiometry. Using this process, it has been possible to synthesize phase-pure Bi-2223 phase by calcining the appropriate polymeric precursors in air at 800°C for several hours. The superconductivity studies show that the Pechini-synthesized materials appear to offer high-quality performance. 相似文献
993.
Abstracts are not published in this journal
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
994.
A finite-difference numerical method of solution for the unsteady, incompressible Navier-Stokes equations using primitive variables is presented. The rate form of the equation of state is used for the calculation of pressure. This form of the equation of state is well-suited for use with the unsteady form of the conservation equations (mass, momentum and energy). An implicit algorithm is used for the time integration for greater numerical stability. This method is used to solve a known benchmark problem in steady-state natural convection as a test of steady-state accuracy. The results of the simulation are compared to the benchmark. 相似文献
995.
996.
双重孔隙介质的碳酸盐岩油藏在稳定注水采油后岩块系统还存在大量剩余油,而不稳定注水方法可在一定程度上提高水驱油效率。室内物理模型实验、数值模拟计算及现场试验结果一致表明:在碳酸盐岩油藏注水开发后期采用衰竭式降压开采,周期注水等不稳定注水方式,能够提高水驱油效率,改善油藏开发效果,获得良好的经济效益。 相似文献
997.
Activitibs of Si in binary Cu-Si and ternary Cu-Ti-Si melts were measured at 1 550℃ by using a method of chemical equilIbrium between gas and liquid. The activity interaction coefficients of Si in the melts have been determined from the experimental data (lny = -5.69. s = 6.69. P2: = -26.22. E; =-43.96) and activity interaction coefficients of Ti in binary Cu-Ti melt at 1550℃ has been estimated from Sommer's data based on the regular solution model (lny =-1 .10. : = 2.95.p:=-2.10). 相似文献
998.
999.
1000.
Buildings are usually subject to a variety of stochastic influences. Though the deterministic approach to building thermal modelling is widespread, it cannot easily model the effects of such influences, and a different approach might be better. In this study, stochastic models are derived which describe the thermal behaviour of a full-scale room exposed to the naturally occurring disturbances of climate (temperature, solar irradiance, infiltration), occupancy and appliance usage. A Box-Jenkins time series analysis technique is employed, and univariate stochastic models are fitted to the internal and external air temperature series. The models are validated by comparing the observed temperature with values forecasted ahead (in steps of 1 h) by the models, over a 36-h period; agreement was found to be good. It is concluded that the stochastic modelling approach can be applied successfully to the thermal analysis of a building's behaviour, thereby affording a method which accounts for random influences in a compact model format. The technique has particular relevance to advanced model-based control implemented via ‘intelligent’ digital controllers and building energy management systems, and its application in this respect is discussed. 相似文献