全文获取类型
收费全文 | 102794篇 |
免费 | 12666篇 |
国内免费 | 5717篇 |
专业分类
电工技术 | 14004篇 |
技术理论 | 18篇 |
综合类 | 7816篇 |
化学工业 | 18224篇 |
金属工艺 | 3636篇 |
机械仪表 | 4371篇 |
建筑科学 | 12194篇 |
矿业工程 | 2370篇 |
能源动力 | 17033篇 |
轻工业 | 3174篇 |
水利工程 | 2035篇 |
石油天然气 | 3087篇 |
武器工业 | 820篇 |
无线电 | 7214篇 |
一般工业技术 | 11242篇 |
冶金工业 | 4543篇 |
原子能技术 | 1995篇 |
自动化技术 | 7401篇 |
出版年
2024年 | 596篇 |
2023年 | 2208篇 |
2022年 | 3571篇 |
2021年 | 3965篇 |
2020年 | 4136篇 |
2019年 | 3791篇 |
2018年 | 3264篇 |
2017年 | 3788篇 |
2016年 | 4199篇 |
2015年 | 4189篇 |
2014年 | 6753篇 |
2013年 | 6930篇 |
2012年 | 7196篇 |
2011年 | 8169篇 |
2010年 | 6213篇 |
2009年 | 6306篇 |
2008年 | 5800篇 |
2007年 | 6424篇 |
2006年 | 5341篇 |
2005年 | 4482篇 |
2004年 | 3672篇 |
2003年 | 3268篇 |
2002年 | 2818篇 |
2001年 | 2345篇 |
2000年 | 2036篇 |
1999年 | 1595篇 |
1998年 | 1379篇 |
1997年 | 1115篇 |
1996年 | 985篇 |
1995年 | 785篇 |
1994年 | 654篇 |
1993年 | 549篇 |
1992年 | 474篇 |
1991年 | 371篇 |
1990年 | 329篇 |
1989年 | 271篇 |
1988年 | 214篇 |
1987年 | 159篇 |
1986年 | 127篇 |
1985年 | 141篇 |
1984年 | 143篇 |
1983年 | 89篇 |
1982年 | 92篇 |
1981年 | 43篇 |
1980年 | 49篇 |
1979年 | 28篇 |
1978年 | 15篇 |
1977年 | 13篇 |
1959年 | 20篇 |
1951年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
The applicability of the identical elements (IE) model of arithmetic fact retrieval (T. C. Rickard, A. F. Healy, & L. E. Bourne, 1994) to cued recall from episodic (image and sentence) memory was explored in 3 transfer experiments. In agreement with results from arithmetic, speedup following even minimal practice recalling a missing word from an episodically bound word triplet did not transfer positively to other cued recall items involving the same triplet. The shape of the learning curve further supported a shift from episode-based to IE-based recall, extending some models of skill learning to cued recall practice. In contrast with previous findings, these results indicate that a form of representation that is independent of the original episodic memory underlies cued-recall performance following minimal practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
93.
LNG冷量优化集成利用技术 总被引:7,自引:1,他引:6
我国将相继在沿海地区建成多个LNG接收站,每年将进口数以千万吨计的LNG,同时携带数着巨额冷量,而这些冷量可用于发电、空气分离、制造干冰、低温冷库等众多领域。基于国外LNG冷量利用现状,指出我国即将展开和实施此项技术还存在着:过程火用损较大,缺乏系统、全面的LNG冷量利用技术的研发指导机制,以及宏观调控力度薄弱等问题,进而提出了发展LNG冷量的集成利用方案,可为此类技术的研发利用提供新思路。以福建即将进口的LNG为例,模拟了空气分离与干冰制备的集成工艺流程,结果表明:福建每年进口的260×104t LNG可以冷却290×104t空气,相当于60000 m3/h的氧气制备规模,还可以生产100×104t的干冰,其过程火用损较小;其剩余的高温位冷量可应用于低温冻结库或冰灯等项目,这对主体装置的实施效果和过程火用损的影响较小。该技术的优点在于可灵活控制冷却空气的液化率,基本不用冷却循环水,流程简单,设备投资少,能耗低等。 相似文献
94.
The performance of the energy consumption of an electronic valve and a classical thermostatic valve has been compared when these expansion valves are adopted in a vapour compression plant subjected to a cold store. The main aim is to verify experimentally which type of expansion valve would be preferable from energy point of view when a classical thermostat or a fuzzy logic algorithm are used as the control system for the refrigeration capacity. The fuzzy logic‐based control is able to modulate continuously the compressor speed through an inverter. The results show that with a fuzzy algorithm, the thermostatic expansion valve allows an energy saving of about 8% in comparison with the electronic valve. When on–off control is used, the electric energy consumption obtained both with the electronic valve and with the thermostatic valve is comparable. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
95.
96.
Gas/liquid mass transfer has been investigated using a stirred vessel gas/liquid contactor using non‐Newtonian media and carbon dioxide as absorbent and gas phase, respectively. The volumetric mass transfer coefficients at different operational variables have been determined. Non‐Newtonian media (liquid phase) were prepared as aqueous solutions of sodium carboxymethyl cellulose salt. The influence of the rheological properties, polymer concentration, stirring rate, and gas flow rate on mass transfer was studied for these liquid phases. Kinematic viscosity and density experimental data were used to calculate the average molecular weight corresponding to the polymer employed. The Ostwald model has been used to fit the rheological behavior of aqueous solutions of the polymer employed as absorbent phase. Reasonably good agreement was found between the predictions of the proposed models and the experimental data of mass transfer coefficients. 相似文献
97.
98.
G. Casalbore‐Miceli M.C. Gallazzi S. Zecchin N. Camaioni A. Geri C. Bertarelli 《Advanced functional materials》2003,13(4):307-312
Voltammetric and spectrophotometric measurements of poly(3,3″‐dipentoxy‐3′‐dicyanoethenyl‐2,2′:5′,2″‐terthiophene) (polyCN) films, in connection with other experimental evidence, reveal a normal oxidative, but a peculiar reductive behavior consisting of trapping of the negative charge during the cathodic scan. Another interesting property of polyCN films is the tendency to form strong intramolecular and intermolecular associations, probably charge‐transfer (CT) complexes. These properties could account for the fact that the photovoltaic performance does not improve when polyCN is blended with a polythiophene donor. 相似文献
99.
Hiroshi Takamatsu Hikaru Yamashiro Nobuo Takata Hiroshi Honda 《International Journal of Refrigeration》2003,26(6):79
Heat and mass transfer in a falling film vertical in-tube absorber was studied experimentally with LiBr aqueous solution. The presented results include the effect of solution flow rate, solution subcooling and cooling water temperature on the absorption in a smooth copper tube 16.05 mm I.D. and 400 mm long. The experimental data in the previous report for a 1200-mm-long tube was also re-examined and compared. It was demonstrated by the observation of the flow in the tube that the break down of the liquid film into rivulets leads to deterioration of heat and mass transfer at lower film Reynolds number or in longer tubes. An attempt to evaluate physically acceptable heat and mass transfer coefficients that are defined with estimated temperature and concentration at the vapor–liquid interface was also presented. 相似文献
100.
Dvoryankin V. F. Dikaev Yu. M. Kudryashov A. A. Sokolovskii A. A. 《Measurement Techniques》2003,46(8):806-809
A method is described for determining the instantaneous effective energy of x-ray tube brehmsstrahlung by means of two semiconductor detectors employing epitaxial GaAs structures and a measurement circuit, which together determine the effective energy with an error of 5% in the range 20–80 keV in the presence of nonlinearity in the detector response. 相似文献