全文获取类型
收费全文 | 43492篇 |
免费 | 4842篇 |
国内免费 | 3440篇 |
专业分类
电工技术 | 3266篇 |
技术理论 | 8篇 |
综合类 | 6436篇 |
化学工业 | 2958篇 |
金属工艺 | 982篇 |
机械仪表 | 2627篇 |
建筑科学 | 4050篇 |
矿业工程 | 1458篇 |
能源动力 | 1441篇 |
轻工业 | 596篇 |
水利工程 | 1365篇 |
石油天然气 | 1086篇 |
武器工业 | 1038篇 |
无线电 | 5116篇 |
一般工业技术 | 5062篇 |
冶金工业 | 2346篇 |
原子能技术 | 490篇 |
自动化技术 | 11449篇 |
出版年
2024年 | 168篇 |
2023年 | 699篇 |
2022年 | 930篇 |
2021年 | 1191篇 |
2020年 | 1387篇 |
2019年 | 1287篇 |
2018年 | 1332篇 |
2017年 | 1580篇 |
2016年 | 1667篇 |
2015年 | 1714篇 |
2014年 | 2535篇 |
2013年 | 3130篇 |
2012年 | 2859篇 |
2011年 | 3226篇 |
2010年 | 2571篇 |
2009年 | 2672篇 |
2008年 | 2716篇 |
2007年 | 2886篇 |
2006年 | 2627篇 |
2005年 | 2299篇 |
2004年 | 1839篇 |
2003年 | 1531篇 |
2002年 | 1332篇 |
2001年 | 1076篇 |
2000年 | 952篇 |
1999年 | 807篇 |
1998年 | 638篇 |
1997年 | 568篇 |
1996年 | 456篇 |
1995年 | 456篇 |
1994年 | 392篇 |
1993年 | 324篇 |
1992年 | 291篇 |
1991年 | 215篇 |
1990年 | 180篇 |
1989年 | 205篇 |
1988年 | 150篇 |
1987年 | 81篇 |
1986年 | 97篇 |
1985年 | 79篇 |
1984年 | 72篇 |
1983年 | 57篇 |
1982年 | 57篇 |
1981年 | 45篇 |
1980年 | 38篇 |
1979年 | 33篇 |
1978年 | 33篇 |
1977年 | 28篇 |
1964年 | 29篇 |
1955年 | 36篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
双螺杆反应挤出模型的研究 总被引:5,自引:0,他引:5
详细研究了双螺杆中反应挤出聚合物的动力学模型、流动模型和传热模型。通过实验得到了双螺杆反应器中聚合物的停留时间分布及平均停留时间。 相似文献
43.
MODELING LIQUID MASS TRANSFER IN HIGEE SEPARATION PROCESS 总被引:1,自引:0,他引:1
Correspondence concerning this paper should be addressed to Professor Richard S.H. Mah. Hsien-Hsin Tung is now affiliated with Department of Chemical Engineering, California Institute of Technology
Penetration theory is used to describe the liquid mass transfer in Higee separation process. Within a possible range of effective areas, it is shown that the predicted mass transfer coefficients are in reasonable agreement with the estimated mass transfer coefficients. The estimated coefficients were calculated from the experimental data and the possible effective areas. Hence it is concluded the penetration theory is generally applicable to describe liquid mass transfer in Higee separation process. The comparison also suggests that liquid mixing at the junctions of packing materials may be more complete in Higee process than in traditional process. 相似文献
Penetration theory is used to describe the liquid mass transfer in Higee separation process. Within a possible range of effective areas, it is shown that the predicted mass transfer coefficients are in reasonable agreement with the estimated mass transfer coefficients. The estimated coefficients were calculated from the experimental data and the possible effective areas. Hence it is concluded the penetration theory is generally applicable to describe liquid mass transfer in Higee separation process. The comparison also suggests that liquid mixing at the junctions of packing materials may be more complete in Higee process than in traditional process. 相似文献
44.
马云辉 《微电子学与计算机》1998,15(6):48-51
本文采用信号流图法设计了一种基于OTA的三输入一输出多功能电压模滤波器新电路,该电路由五个OTA和两个接地电容构成,合理选择输入电压可实现低通、高通、带通、带阻及全通滤波功能。文章还对电路进行了MOS管级的计算机仿真,其结果表明所提出的电路方案正确有效。 相似文献
45.
46.
电流模式n阶传输函数的OA-OTA实现 总被引:1,自引:0,他引:1
马云辉 《固体电子学研究与进展》2002,22(3):294-296,360
提出了一种新的实现任意 n阶电流模式传输函数的网络结构。该电路仅含运算放大器 (OA)和运算跨导放大器 (OTA)有源器件 ,因而适于全集成。适当设置 OTA的跨导值能实现任意高阶传输函数 ,且传输函数的系数可独立调整。文中推导了滤波器的设计公式 ,并给出了截止频率为 1 0 0 k Hz的三阶巴特沃斯低通滤波器实例 ,PSPICE仿真结果表明所提电路及设计公式是正确的 相似文献
47.
本文在弱闪烁条件下,利用广泛适用于星际闪烁、行星际闪烁和电离层闪烁的薄相屏理论,以行星际闪烁为算例,对薄相屏闪烁进行了数值分析。结果表明:垂直于介质运动方向上的不规则结构的大小对闪烁有着重要的影响,直接表现在频谱的变化趋势和振荡幅度的不同。尤其是当小于Fresnel尺度时,数值计算表明此时没有闪烁发生。 相似文献
48.
天线方向图的复射线仿真 总被引:1,自引:0,他引:1
根据复射线理论,利用复源点高斯波束场来模拟天线的远场方向图。本文提出三种模拟方法,即主瓣匹配法,峰值匹配法和逐点匹配法,给出了多种方向图的仿真结果。数值分析和优化结果表明,复射线峰值匹配法是一种精确实用的天线方向图仿真技术。 相似文献
49.
Energy minimization and design for testability 总被引:6,自引:0,他引:6
Srimat T. Chakradhar Vishwani D. Agrawal Michael L. Bushnell 《Journal of Electronic Testing》1994,5(1):57-66
The problem of fault detection in general combinational circuits is NP-complete. The only previous result on identifying easily testable circuits is due to Fujiwara who gave a polynomial time algorithm for detecting any single stuck fault inK-bounded circuits. Such circuits may only contain logic blocks with no more thanK input lines and the blocks are so connected that there is no reconvergent fanout among them. We introduce a new class of combinational circuits called the (k, K)-circuits and present a polynomial time algorithm to detect any single or multiple stuck fault in such circuits. We represent the circuit as an undirected graphG with a vertex for each gate and an edge between a pair of vertices whenever the corresponding gates have a connection. For a (k, K)-circuit,G is a subgraph of ak-tree, which, by definition, cannot have a clique of size greater thank+1. Basically, this is a restriction on gate interconnections rather than on the function of gates comprising the circuit. The (k, K)-circuits are a generalization of Fujiwara'sK-bounded circuits. Using the bidirectional neural network model of the circuit and the energy function minimization formulation of the fault detection problem, we present a test generation algorithm for single and multiple faults in (k, K)-circuits. This polynomial time aggorithm minimizes the energy function by recursively eliminating the variables. 相似文献
50.
This paper analyses the collaborative design ofa high-technology product, a neuromagnetometerused in the analysis of the activity of thehuman cortex. The producer, Neuromag Company istrying to transform the device from a basicresearch instrument into a means of clinicalpractice. This transition is analyzed as asimultaneous evolution of the product,producer-user network and user activities. Thenetwork is analyzed as a network of activitysystems. Each activity has a historicallyformed object and a motive of its own, as wellas a system of cultural means and expertise. Weuse these to explain and understand theinterests and points of view of the actors inrelation to the product and the contradictionsof the producer-user network. It is suggestedthat the emerging user needs of collectiveactors must be analyzed at three levels. At thefirst level, the use value of the product, itscapacity of solving the vital problems andchallenges of developing user activities, ischaracterized. The second-level analysisconcerns the creation and development of thenecessary complementary tools and services thatmake the implementation and use of the productpossible. This task presupposes collaborationbetween several communities of the innovationnetwork. The third level is the situatedpractical use of the product. In ourexperience, it is advantageous that researcherscontribute with their data to a dialogue inwhich the user needs are articulated. 相似文献