全文获取类型
收费全文 | 253040篇 |
免费 | 4027篇 |
国内免费 | 1046篇 |
专业分类
电工技术 | 4386篇 |
综合类 | 202篇 |
化学工业 | 37313篇 |
金属工艺 | 8252篇 |
机械仪表 | 7299篇 |
建筑科学 | 6809篇 |
矿业工程 | 541篇 |
能源动力 | 7273篇 |
轻工业 | 28706篇 |
水利工程 | 2126篇 |
石油天然气 | 1853篇 |
武器工业 | 5篇 |
无线电 | 33543篇 |
一般工业技术 | 46361篇 |
冶金工业 | 46794篇 |
原子能技术 | 3401篇 |
自动化技术 | 23249篇 |
出版年
2021年 | 1820篇 |
2020年 | 1355篇 |
2019年 | 1677篇 |
2018年 | 2583篇 |
2017年 | 2606篇 |
2016年 | 2903篇 |
2015年 | 2178篇 |
2014年 | 3682篇 |
2013年 | 12014篇 |
2012年 | 6800篇 |
2011年 | 9714篇 |
2010年 | 7495篇 |
2009年 | 8435篇 |
2008年 | 8965篇 |
2007年 | 8968篇 |
2006年 | 8328篇 |
2005年 | 7517篇 |
2004年 | 7232篇 |
2003年 | 7120篇 |
2002年 | 6613篇 |
2001年 | 7048篇 |
2000年 | 6346篇 |
1999年 | 6854篇 |
1998年 | 16501篇 |
1997年 | 11456篇 |
1996年 | 8656篇 |
1995年 | 6569篇 |
1994年 | 5735篇 |
1993年 | 5600篇 |
1992年 | 4004篇 |
1991年 | 3784篇 |
1990年 | 3561篇 |
1989年 | 3388篇 |
1988年 | 3293篇 |
1987年 | 2600篇 |
1986年 | 2497篇 |
1985年 | 3170篇 |
1984年 | 2806篇 |
1983年 | 2561篇 |
1982年 | 2352篇 |
1981年 | 2397篇 |
1980年 | 2202篇 |
1979年 | 2051篇 |
1978年 | 1882篇 |
1977年 | 2186篇 |
1976年 | 2731篇 |
1975年 | 1585篇 |
1974年 | 1491篇 |
1973年 | 1561篇 |
1972年 | 1147篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Many media processing applications create a load that varies significantly over time. Hence, if such an application is assigned a lower processing-time budget than needed in its worst-case load situation, deadline misses are likely to occur. This problem can be dealt with by designing media processing applications in a scalable fashion. A scalable media processing application can run in multiple qualities, leading to correspondingly different resource demands. The problem we consider is to find an accompanying quality control strategy, which minimizes both the number of deadline misses and the number of quality changes, while maximizing the quality of processing. We present an initial approach to the above problem by modeling it as a Markov decision process (MDP). Our model is based on measuring relative progress at milestones. Solving the MDP results in a quality control strategy that can be applied during runtime with only little overhead. We evaluate our approach by means of a practical example, which concerns a scalable MPEG-2 decoder. 相似文献
102.
103.
D. Vignolles D. Smirnov G. Rikken B. Raquet H. Rakoto C. Proust M. Nardone J. Léotin F. Lecouturier M. Goiran O. Drachenko J. M. Broto L. Brossard A. Audouard 《Journal of Low Temperature Physics》2003,133(1-2):97-120
An overview over past and present activities and future developments at the Toulouse pulsed magnetic field facility is given, both as far as technical developments of the infrastructure, as well as low temperature physics performed at the LNCMP are concerned. 相似文献
104.
105.
The selector activated sludge (SAS) systems are known to prevent excessive growth of filamentous microorganisms responsible for bulking sludge, but these systems were hardly ever modelled. This study aimed to develop a model capable of predicting rapid substrate removal in the SAS systems. For this purpose, the Activated Sludge Model No. 3 (ASM3) was extended with three processes (adsorption, direct growth on the adsorbed substrate under aerobic or anoxic conditions). The modified ASM3 was tested against the results of batch experiments with the biomass originating from two full-scale SAS systems in Germany. The endogenous biomass was mixed with various readily biodegradable substrates (acetate, peptone, glucose and wastewater) and the utilisation of substrate (expresses as COD) and oxygen uptake rates (OURs) were measured during the experiments. In general, model predictions fitted to the experimental data, but a considerable number of kinetic (5) and stoichiometric (2) parameters needed to be adjusted during model calibration. The simulation results revealed that storage was generally a dominating process compared to direct growth in terms of the adsorbed substrate utilisation. The contribution of storage ranged from 65-71% (Plant A) and 69-92% (Plant B). 相似文献
106.
107.
108.
109.
Yang C.W. Fang Y.K. Lin C.S. Tsair Y.S. Chen S.M. Wang W.D. Wang M.F. Cheng J.Y. Chen C.H. Yao L.G. Chen S.C. Liang M.S. 《Electronics letters》2003,39(21):1499-1501
A novel technique to form high-K dielectric of HfSiON by doping base oxide with Hf and nitridation with NH/sub 3/, sequentially, is proposed. The HfSiON gate dielectric demonstrates excellent device performances such as only 10% degradation of saturation drain current and almost 45 times of magnitude reduction in gate leakage compared with conventional SiO/sub 2/ gate at the approximately same equivalent oxide thickness. Additionally, negligible flatband voltage shift is achieved with this technique. Time-dependent dielectric breakdown tests indicate that the lifetime of HfSiON is longer than 10 years at V/sub dd/=2 V. 相似文献
110.
N. Jongen M. Donnet P. Bowen J. Lemaître H. Hofmann R. Schenk C. Hofmann M. Aoun‐Habbache S. Guillemet‐Fritsch J. Sarrias A. Rousset M. Viviani M.T. Buscaglia V. Buscaglia P. Nanni A. Testino J.R. Herguijuela 《化学工程与技术》2003,26(3):303-305
The synthesis of powders with controlled shape and narrow particle size distributions is still a major challenge for many industries. A continuous Segmented Flow Tubular Reactor (SFTR) has been developed to overcome homogeneity and scale‐up problems encountered when using batch reactors. Supersaturation is created by mixing the co‐reactants in a micromixer inducing precipitation; the suspension is then segmented into identical micro‐volumes by a non‐miscible fluid and sent through a tube. These micro‐volumes are more homogeneous when compared to large batch reactors leading to narrower size distributions, better particle morphology, polymorph selectivity and stoichiometry. All these features have been demonstrated on single tube SFTR for different chemical systems. To increase productivity for commercial application the SFTR is being “scaled‐out” by multiplying the number of tubes running in parallel instead of scaling‐up by increasing their size. The versatility of the multi‐tube unit will allow changes in type of precipitate with a minimum of new investment as new chemistry can be researched, developed and optimised in a single tube SFTR and then transferred to the multi‐tube unit for powder production. 相似文献