全文获取类型
收费全文 | 36619篇 |
免费 | 5567篇 |
国内免费 | 3224篇 |
专业分类
电工技术 | 1639篇 |
技术理论 | 1篇 |
综合类 | 5061篇 |
化学工业 | 3247篇 |
金属工艺 | 3625篇 |
机械仪表 | 2996篇 |
建筑科学 | 5665篇 |
矿业工程 | 3278篇 |
能源动力 | 3242篇 |
轻工业 | 662篇 |
水利工程 | 3352篇 |
石油天然气 | 2704篇 |
武器工业 | 1356篇 |
无线电 | 1163篇 |
一般工业技术 | 3664篇 |
冶金工业 | 1474篇 |
原子能技术 | 590篇 |
自动化技术 | 1691篇 |
出版年
2024年 | 174篇 |
2023年 | 558篇 |
2022年 | 1275篇 |
2021年 | 1371篇 |
2020年 | 1489篇 |
2019年 | 1131篇 |
2018年 | 1115篇 |
2017年 | 1454篇 |
2016年 | 1727篇 |
2015年 | 1753篇 |
2014年 | 2462篇 |
2013年 | 2378篇 |
2012年 | 3292篇 |
2011年 | 3237篇 |
2010年 | 2382篇 |
2009年 | 2443篇 |
2008年 | 2136篇 |
2007年 | 2752篇 |
2006年 | 2383篇 |
2005年 | 1942篇 |
2004年 | 1573篇 |
2003年 | 1242篇 |
2002年 | 953篇 |
2001年 | 854篇 |
2000年 | 651篇 |
1999年 | 504篇 |
1998年 | 407篇 |
1997年 | 355篇 |
1996年 | 294篇 |
1995年 | 223篇 |
1994年 | 214篇 |
1993年 | 139篇 |
1992年 | 138篇 |
1991年 | 83篇 |
1990年 | 83篇 |
1989年 | 48篇 |
1988年 | 24篇 |
1987年 | 27篇 |
1986年 | 22篇 |
1985年 | 7篇 |
1984年 | 14篇 |
1983年 | 7篇 |
1982年 | 13篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 13篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1959年 | 10篇 |
1951年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
151.
TheStabilityofRunge-KuttaMethodsforSystemsofDelayDifferentialEquations¥WANGXiaobiao;LIUMingzhu(王晓彪)(刘明珠)(Dept.ofMathematics,Har... 相似文献
152.
Linear stress analysis without body force can be easily carried out by means of the boundary element method. Some cases of linear stress analysis with body force can also be solved without the domain integral. However domain integrals are generally necessary to solve the linear stress problems with complicated body forces. This paper shows that the linear stress problems with complicated body forces can be solved approximately without the domain integral. In order to solve these problems, the domain is divided into small areas using contour lines of body force. In these areas, the distributions of body force are assumed approximately to satisfy the Laplace equation. 相似文献
153.
Wei Xiao-lin Institute of Mechanics Chinese Academy of Sciences Beijing China IVD. Stuttgart University Pfaffenwaldring D Stuttgart Germany Tian Wen-dong Wang Jian-min Sheng Hong-zhi Institute of Mechanics Chinese Academy of Sc 《水动力学研究与进展(B辑)》2001,(1)
NOTATIONSA Areaofinlet ,m2a Centrifugalacceleration ,m2 /si Gridofaxialdirectionml MaximumgridnumberofradialdirectionQ Fluidmassrate ,m3/sRc Maximumradiusofcyclone ,mRe Reynoldsnumberr Dimensionlessradialdistancet Dimensionlesstimeu Dimensionlessaxialveloc… 相似文献
154.
155.
六通管是石油化工设备及压力管道中的重要元件,传统的制作及连接方法是在集流管上开孔,然后将支管插入并焊接而成或采用锻制的方法制成。采用挤压的方法制作六通管,将其与支管对接焊接。并通过试验及数值模拟对该结构的安全性进行了研究,实践证明,这种挤压六通管的强度性能优于普通的焊接六通管,可以广泛应用于工业生产。 相似文献
156.
孤东油田极浅海区域新发现几个边际油藏。其中垦东401块水深-2m,距陆地2.7km,为稀油、疏松砂岩油藏,试油获14~25t/d工业油流。在三维地震、测井约束地震反演、数值模拟和油藏经营管理评价基础上编制了产能建设方案,通过修筑海公路、人工岛、丛式井组、大位移水平井、采用数据采集与控制的远程测控和紧急关断技术,能够无人职守、遥测遥控,整体实现了海油陆采。有效动用地质储量233×104t,钻井12口,建成年产油4×104t能力,累产油8.6×104t。目前在垦东12人工岛上钻打了26口井,推广了海油陆采经验。 相似文献
157.
Guang R. Gao 《Parallel Computing》1987,4(3):305-321
A new method of classification for numerical stability of parallel algorithms is proposed based on the theoretical foundation of forward error analysis. It partitions the algorithms according to their asymptotic stability—a measure introduced to relate the limiting behavior of the stability to the size of the problem. Using this method, the stability aspect of the pipelined solution technique for first-order and second-order linear recurrences—the core of a tridiagonal linear equation solver—is studied. In particular, it shows that the pipelined solution method of the first-order linear recurrences has the same degree of stability as the commonly used sequential evaluation algorithms. The stability problems of sequential and pipelined solution methods of the second-order linear recurrences are also studied. 相似文献
158.
应用非线性kε湍流模式,采用非正交曲线坐标系下求解三维NS方程的非交错网格有限体积方法,数值模拟了充分发展条件下,三角形排列无限棒束间通道内,不同的几何参数(P/D),雷诺数(Re)下的流动和传热问题。给出了不同参数下的速度和温度分布以及湍流二次流动,分析了几何参数、雷诺数及二次流对棒束内流动和传热特性的影响,得到了不同参数下通道的摩擦系数和Nuselt数,并与经验关系式作了比较 相似文献
159.
Eugene Fiume† 《Computer Graphics Forum》1995,14(1):47-58
The main preoccupations of research in computer-aided geometric design have been on shape-specification techniques for polynomial curves and surfaces, and on the continuity between segments or patches. When modelling with such techniques, curves and surfaces can be compressed or expanded arbitrarily. There has been relatively little work on interacting with direct spatial properties of curves and surfaces, such as their arc length or surface area. As a first step, we derive families of parametric piecewise polynomial curves that satisfy various positional and tangential constraints together with arc-length constraints. We call these curves isometric curves. A space curve is defined as a sequence of polynomial curve segments, each of which is defined by the familiar Hermite or Bézier constraints for cubic polynomials; as well, each segment is constrained to have a specified arc length. We demonstrate that this class of curves is attractive and stable. We also describe the numerical techniques used that are sufficient for achieving real time interaction with these curves on low-end workstations. 相似文献
160.
T. S. Lee S. B. Lee J. M. Kim J. S. Kim S. H. Suh J. H. Song I. H. Park S. U. Kim M. J. Park 《Journal of Electronic Materials》1995,24(9):1057-1059
In order to improve the Zn homogeneity along the axial direction of CdZnTe boule, we have employed a modified Bridgman technique
using a (Cd, Zn) alloy source in communication with the melt, whose temperature has been gradually changed from 800 to 840°C
during growth. Electron probe microanalysis (EPMA) measurements of Zn composition in the boule shows an excellent homogeneity
of Zn along the axis of the CdZnTe boule compared with results in a boule grown by using a fixed source temperature. We have
performed a numerical simulation to obtain the approximate temperatures of additional heating and cooling needed to improve
the radial Zn homogeneity. CdZnTe boule has been grown by seeded vertical Bridgman furnace with two zones of heater and cooler.
Ultraviolet/visible spectroscopic measurements of Zn composition over the length of the boule indicate that the radial distribution
of Zn composition is very homogeneous in the body region of the boule, where the radial variation of Zn composition is ±0.0005. 相似文献