全文获取类型
收费全文 | 20481篇 |
免费 | 1022篇 |
国内免费 | 472篇 |
专业分类
电工技术 | 655篇 |
技术理论 | 1篇 |
综合类 | 1700篇 |
化学工业 | 3941篇 |
金属工艺 | 463篇 |
机械仪表 | 759篇 |
建筑科学 | 1859篇 |
矿业工程 | 428篇 |
能源动力 | 459篇 |
轻工业 | 2205篇 |
水利工程 | 270篇 |
石油天然气 | 325篇 |
武器工业 | 73篇 |
无线电 | 806篇 |
一般工业技术 | 2833篇 |
冶金工业 | 974篇 |
原子能技术 | 143篇 |
自动化技术 | 4081篇 |
出版年
2024年 | 62篇 |
2023年 | 205篇 |
2022年 | 294篇 |
2021年 | 390篇 |
2020年 | 452篇 |
2019年 | 453篇 |
2018年 | 423篇 |
2017年 | 551篇 |
2016年 | 608篇 |
2015年 | 630篇 |
2014年 | 1157篇 |
2013年 | 1721篇 |
2012年 | 1321篇 |
2011年 | 1610篇 |
2010年 | 1193篇 |
2009年 | 1193篇 |
2008年 | 1025篇 |
2007年 | 1274篇 |
2006年 | 1056篇 |
2005年 | 879篇 |
2004年 | 802篇 |
2003年 | 686篇 |
2002年 | 605篇 |
2001年 | 477篇 |
2000年 | 362篇 |
1999年 | 342篇 |
1998年 | 301篇 |
1997年 | 250篇 |
1996年 | 190篇 |
1995年 | 197篇 |
1994年 | 145篇 |
1993年 | 118篇 |
1992年 | 105篇 |
1991年 | 71篇 |
1990年 | 71篇 |
1989年 | 78篇 |
1988年 | 81篇 |
1987年 | 50篇 |
1986年 | 47篇 |
1985年 | 58篇 |
1984年 | 73篇 |
1983年 | 89篇 |
1982年 | 93篇 |
1981年 | 30篇 |
1980年 | 30篇 |
1979年 | 21篇 |
1978年 | 19篇 |
1977年 | 17篇 |
1959年 | 5篇 |
1955年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
A Method to Measure Emissions from Dryers with Diffuse Leakages, Using Evaporated Water as a Tracer 总被引:2,自引:0,他引:2
This paper describes a novel method to measure emission from dryers. The method resolves the known difficulties caused by diffuse emissions, and also solves the problems associated with high moisture content of the drying medium. The basic idea is to use water vapor to determine the exhaust flow, while a dry ice trap is used both to preconcentrate emitted VOCs and to determine the moisture content of the drying medium. 相似文献
3.
An experimental procedure was developed to study directly the process by which liquid bridges between small particles in a granule form and solidify. The evolution of saturated solutions of such pharmaceutical excipients as lactose and mannitol in a liquid bridge was studied on a system situated on a microscope slide. Solidification and crystallization kinetics and phase composition during and immediately following bridge formation were observed directly. It was shown that bridges on the microscope slide and in the granule behave very much the same regardless of the different length and diffusion-scales of the two systems.We found that solid bridge formation takes place in several consecutive but distinct steps. In the case of lactose, considerable shrinkage of the initial liquid bridge takes place prior to the onset of crystallization. Further bridge solidification at ambient conditions occurs via simultaneous crystallization and vitrification within minutes. As a result, a “solid” bridge usually contains both a crystalline and a non-crystalline phase, the crystalline phase being predominately α-lactose monohydrate. Most of the non-crystalline phase eventually converts to crystalline β-lactose but the process may take many hours or even days. Results for this process are compared for samples obtained from different manufacturers of commercially available lactose. In the case of mannitol, different polymorphic forms crystallize as the drying/crystallization process progresses. A formed “solid” bridge usually contains several polymorphs of mannitol. The relevance of the behavior of the two model systems (pure lactose and pure mannitol) to a real granulation and tabletting process is discussed. 相似文献
4.
The focus of this paper lies in the practical aspects of voice over IP communication. VoIP configurations in the H.323 standard will be presented briefly. Following that, the fundamental protocol procedure of H.323 communication will be briefly explained. A further part of the paper will address the subject QoS (quality of service), and present the common measurement methods used in QoS. Results gained from experiments conducted in a VoIP environment will then follow. The investigations concentrate primarily on the load behavior of voice packets in relation to important parameters of this service. The results obtained are presented and evaluated in diagrams. The paper concludes with a summary. 相似文献
5.
An experimental technique together with a numerical model is proposed with which the diffusion coefficient and the sorption isotherm of water in paint can be measured. Inside a closed vessel, paint films are on stainless-steel plates. Water is present as water vapour in the air and in the paint. After blowing dry or wet air through the vessel for some time, the situation moves to a new equilibrium. The relative humidity of the air inside the vessel is measured as a function of time. From fitting the theoretical/numerical model against the experimental values, follow the diffusion coefficient and the sorption isotherm of water in the paint. The results show large scattering. When the independently measured sorption isotherm is used as an input parameter in the model, the fitting procedure gives much smaller scattering for the diffusion coefficient. 相似文献
6.
Mohammed Farid 《Chemical engineering science》2003,58(13):2985-2993
A model was developed to predict the change in droplet mass and temperature when it is exposed to hot air, as in spray drying of droplets containing solids. The droplet was assumed first to undergo sensible rapid heating with no mass change. Then the droplet experiences some shrinkage, with no temperature change but rapid mass losses, followed by a period of crust formation with a significant change in droplet mass and temperature and finally a short period of sensible heating of the dried particle. The model, unlike previous models, accounts for shrinkage and for the temperature distribution in the droplet. It provided a good prediction for the change in droplet temperature and mass for some of the experimental measurements available in the literatures. 相似文献
7.
Matthew R. James 《国际强度与非线性控制杂志
》1994,4(6):791-806
》1994,4(6):791-806
In this paper we present a numerical method for estimating the current state of a nonlinear control system. We use finite differences to discretize a modified version of the finite-time observer equations in James. The discretized equations are simple and easily programmed. The convergence and accuracy of the scheme is proved, and the scheme enjoys a number of important properties: availability of rate of convergence estimates, good robustness characteristics, and the ability to handle certain types of discontinuities in the observations. The major disadvantage is that the number of grid points required increases exponentially with the number of state dimensions. 相似文献
8.
Takeshi Nakajo 《Quality and Reliability Engineering International》1993,9(2):111-119
Work system improvements are implemented in various manufacturing processes to prevent problems caused by human errors. However, they are almost always applied to problems which have already occurred. This paper examines a method of identifying latent human errors existing within the work systems beforehand. A procedure for applying failure mode and effect analysis to this identification problem was defined based on over 1000 empirical errors: a work system decomposition criterion and fundamental error modes for listing latent human errors, and then applied to three practical manufacturing processes in order to evaluate its effectiveness. 相似文献
9.
S. ReppA. Sadiki C. SchneiderA. Hinz T. LandenfeldJ. Janicka 《International Journal of Heat and Mass Transfer》2002,45(6):1271-1285
This work aims to compare numerical results obtained by using the Monte Carlo composition-PDF method and a presumed-β-PDF in order to reveal their effects on the prediction of flow and scalar fields in swirling confined methane diffusion flame. Using the intrinsic low dimensional manifolds method for modelling the chemistry and a second moment closure for the turbulence, it is shown that both PDF-methods provide a similar accuracy level of the prediction of mean quantities. While the presumed-β-PDF performs using reasonable computational efforts, the Monte Carlo-PDF allows to capture well the turbulence-chemistry interaction and strong finite-chemistry effects such as local extinction. 相似文献
10.