全文获取类型
收费全文 | 14554篇 |
免费 | 573篇 |
国内免费 | 573篇 |
专业分类
电工技术 | 604篇 |
综合类 | 507篇 |
化学工业 | 1246篇 |
金属工艺 | 981篇 |
机械仪表 | 2100篇 |
建筑科学 | 817篇 |
矿业工程 | 317篇 |
能源动力 | 666篇 |
轻工业 | 245篇 |
水利工程 | 71篇 |
石油天然气 | 199篇 |
武器工业 | 148篇 |
无线电 | 983篇 |
一般工业技术 | 1503篇 |
冶金工业 | 406篇 |
原子能技术 | 132篇 |
自动化技术 | 4775篇 |
出版年
2024年 | 14篇 |
2023年 | 146篇 |
2022年 | 236篇 |
2021年 | 297篇 |
2020年 | 295篇 |
2019年 | 272篇 |
2018年 | 279篇 |
2017年 | 349篇 |
2016年 | 385篇 |
2015年 | 518篇 |
2014年 | 738篇 |
2013年 | 803篇 |
2012年 | 751篇 |
2011年 | 1091篇 |
2010年 | 729篇 |
2009年 | 870篇 |
2008年 | 903篇 |
2007年 | 978篇 |
2006年 | 866篇 |
2005年 | 893篇 |
2004年 | 704篇 |
2003年 | 622篇 |
2002年 | 501篇 |
2001年 | 354篇 |
2000年 | 349篇 |
1999年 | 313篇 |
1998年 | 294篇 |
1997年 | 226篇 |
1996年 | 187篇 |
1995年 | 131篇 |
1994年 | 129篇 |
1993年 | 120篇 |
1992年 | 77篇 |
1991年 | 54篇 |
1990年 | 46篇 |
1989年 | 40篇 |
1988年 | 42篇 |
1987年 | 18篇 |
1986年 | 19篇 |
1985年 | 10篇 |
1984年 | 16篇 |
1983年 | 12篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
A real-time road pricing system in the case of a two-link parallel network is proposed in this paper. The system that is based on a combination of Dynamic Programming and Neural Networks makes “on-line” decisions about road toll values. In the first phase of the proposed model, the best road toll sequences during certain time period are calculated off-line for many different patterns of vehicle arrivals. These toll sequences are computed using Dynamic Programming approach. In the second phase, learning from vehicle arrival patterns and the corresponding optimal toll sequences, neural network is trained. The results obtained during on-line tests are close to the best solution obtained off-line assuming that the arrival pattern is known. 相似文献
72.
微光CCD摄像器件综合特性的分析与比较 总被引:3,自引:1,他引:2
CCD的优良特性使其在微光电视技术领域得到了广泛运用。本文对各种微光CCD摄像器件的综合特性例如信噪比、探测率、动态范围与计数模式等进行了详细的研究与对比,并得出基本结论。 相似文献
73.
74.
The axisymmetric Laplace equation is solved numerically to extract contact-angle data for a flat liquid/vapor interface contacting a submerged hemispherical solid. The liquid/vapor interface is treated as a membrane, with a membrane tension equal to the surface energy of the liquid. By measuring the vertical displacement of the membrane and the projected contact area the membrane makes with the hemisphere, the contact angle and correspondingly the driving force for motion of the contact line can be measured. We show that characteristic receding and advancing contact angles can be obtained by measuring the contact radii formed upon initial contact between the interface and hemisphere and final contact just prior to detachment of the interface, respectively. Use of the technique is illustrated with a model experiment involving the contact of an air/water interface with a poly(methyl methacrylate) surface. 相似文献
75.
76.
The macromolecular structure of coals thermally treated at 35°C, 100°C and 150°C was investigated by dynamic penetrant transport in thin coal sections. The effects of temperature, carbon content in coal, and penetrant type on the transport mechanism were investigated. Dynamic swelling studies showed that penetrant transport into coal is a function of the average molecular weight between crosslinks, Mc. The penetrant transport mechanism at low activity is Fickian diffusion. The transport mechanism deviates from Fickian diffusion to anomalous transport, when the carbon content in coal and penetrant activity increase. Variations of the diffusion coefficients and relaxation constants were determined using a diffusion/relaxation coupled model. 相似文献
77.
78.
Process optimisation and optimal control of batch and continuous drum granulation processes are studied in this paper. The main focus of the current research has been: (i) construction of optimisation and control relevant, population balance models through the incorporation of moisture content, drum rotation rate and bed depth into the coalescence kernels; (ii) investigation of optimal operational conditions using constrained optimisation techniques; (iii) development of optimal control algorithms based on discretized population balance equations; and (iv) comprehensive simulation studies on optimal control of both batch and continuous granulation processes. The objective of steady state optimisation is to minimise the recycle rate with minimum cost for continuous processes. It has been identified that the drum rotation-rate, bed depth (material charge), and moisture content of solids are practical decision (design) parameters for system optimisation. The objective for the optimal control of batch granulation processes is to maximize the mass of product-sized particles with minimum time and binder consumption. The objective for the optimal control of the continuous process is to drive the process from one steady state to another in a minimum time with minimum binder consumption, which is also known as the state-driving problem. It has been known for some time that the binder spray-rate is the most effective control (manipulative) variable. Although other possible manipulative variables, such as feed flow-rate and additional powder flow-rate have been investigated in the complete research project, only the single input problem with the binder spray rate as the manipulative variable is addressed in the paper to demonstrate the methodology. It can be shown from simulation results that the proposed models are suitable for control and optimisation studies, and the optimisation algorithms connected with either steady state or dynamic models are successful for the determination of optimal operational conditions and dynamic trajectories with good convergence properties. 相似文献
79.
单片机系统的动态加密技术 总被引:2,自引:0,他引:2
单片机系统产品的加密和解密技术永远是一个矛盾的统一体。然而 ,为了更好的保护好自己的单片机技术成果和知识产权 ,加大解密成本 ,研究新型加密技术仍是保护成果的主要手段之一。文中在讨论了传统的单片机系统加密和解密技术的基础上 ,提出一种实用而有效的动态加密技术的实现方案。 相似文献
80.