全文获取类型
收费全文 | 155353篇 |
免费 | 13332篇 |
国内免费 | 6805篇 |
专业分类
电工技术 | 6640篇 |
技术理论 | 10篇 |
综合类 | 14124篇 |
化学工业 | 26588篇 |
金属工艺 | 8152篇 |
机械仪表 | 5404篇 |
建筑科学 | 20560篇 |
矿业工程 | 8409篇 |
能源动力 | 7253篇 |
轻工业 | 9799篇 |
水利工程 | 20511篇 |
石油天然气 | 12442篇 |
武器工业 | 595篇 |
无线电 | 5666篇 |
一般工业技术 | 12115篇 |
冶金工业 | 9112篇 |
原子能技术 | 1886篇 |
自动化技术 | 6224篇 |
出版年
2024年 | 567篇 |
2023年 | 2337篇 |
2022年 | 3681篇 |
2021年 | 4570篇 |
2020年 | 4856篇 |
2019年 | 4275篇 |
2018年 | 3802篇 |
2017年 | 4613篇 |
2016年 | 4987篇 |
2015年 | 5046篇 |
2014年 | 8931篇 |
2013年 | 9099篇 |
2012年 | 10949篇 |
2011年 | 11053篇 |
2010年 | 8259篇 |
2009年 | 8713篇 |
2008年 | 7759篇 |
2007年 | 10241篇 |
2006年 | 9571篇 |
2005年 | 8761篇 |
2004年 | 6998篇 |
2003年 | 6595篇 |
2002年 | 5624篇 |
2001年 | 4616篇 |
2000年 | 3946篇 |
1999年 | 3086篇 |
1998年 | 2317篇 |
1997年 | 1893篇 |
1996年 | 1574篇 |
1995年 | 1385篇 |
1994年 | 1043篇 |
1993年 | 825篇 |
1992年 | 655篇 |
1991年 | 482篇 |
1990年 | 421篇 |
1989年 | 402篇 |
1988年 | 270篇 |
1987年 | 248篇 |
1986年 | 178篇 |
1985年 | 178篇 |
1984年 | 162篇 |
1983年 | 99篇 |
1982年 | 65篇 |
1981年 | 46篇 |
1980年 | 47篇 |
1979年 | 50篇 |
1978年 | 22篇 |
1977年 | 29篇 |
1976年 | 23篇 |
1975年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
31.
Stephen J. Allen Pauline A. Brown 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,62(1):17-24
The adsorption of the three metal ions, copper, cadmium and zinc in single component and multi-component mixtures in aqueous solutions by lignite is reported. A comparison is made between the single component saturation uptake and the multi-component uptakes. The isotherms indicate a competitive uptake with copper being preferentially absorbed by the lignite in multi-component solutions. The isotherms are plotted to obtain the Langmuir constants, the Freundlich constants and the Redlich–Peterson constants. Lignite is shown to possess an affinity for the metal ions which make its use as an adsorbent a possible alternative to the use of more expensive activated carbons. 相似文献
32.
Thermal stratification in a mantled hot water storage tank is analysed numerically for different water inlet velocities. The aim is to obtain higher thermal stratification and supply hot water for usage as long as possible. Twelve different water inlet velocities to the hot water storage tank are considered. The numerical method is validated by comparing its results against experimental and numerical results from the literature. It turned out that the results obtained from the numerical analysis have shown very good agreements with the results from previous works. As a result, the water temperature in the tank increases with the increase of the water inlet velocities to the mantle but this increment is not proportional. After a period of operation of 7.2 h, which corresponds to the average sunshine duration in Turkey, temperature increments of 6.5 and 35 K have been estimated for the hot water inlet velocities of 0.01 and 0.3 m s?1, respectively, at a radial distance of 0.1 m and a height of 1 m inside the storage tank. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
33.
34.
本文采用粒子追踪理论对水平管中粒子流动状态进行了数值模拟.文中提出了一种新的粒子碰撞模型,并忽略粒子的旋转和扬力,仅考虑气流阻力和重力对粒子的影响,在输送量为9.13×10~3kg/s,混合比约0.3的条件下,通过数值计算得知:由于粒子间的碰撞,使得异径粒子的速度趋向平均化;粒子间的碰撞是粒子悬浮的原因之一;粒子的浓度沿管轴向是随时间而发生变化的. 相似文献
35.
36.
37.
No authorship indicated 《Canadian Metallurgical Quarterly》2004,59(8):728
Provides the biography of Dante Cicchetti and announces that he has received the APA Award for Distinguished Senior Career Contributions to Psychology in the Public Interest (2004) for his seminal role in bridging theory, research, and practice by fostering the emergence and coalescence of the field of developmental psychopathology. A selected bibliography is also provided. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
38.
39.
40.
The aluminium species in different tea infusions were investigated, by determining their stability constants and concentration. This was done for some particular samples using a simple experimental method based on the sorption of aluminium on the strongly sorbing resin Chelex 100, by a batch procedure. From the thermodynamic information obtained it is possible to calculate the concentration of the different species, and in particular that of the free metal ion, which is very important for evaluating the adsorption of aluminium on biological membranes. It was found that aluminium in the tea infusions here considered is present at high total concentration, approximately 0.1 mM, but mainly linked to strong complexes, for instance with side reaction coefficient higher than 10(5.11) at pH 3.95 in one case (tea 1). This could be the reason for the low toxicity of aluminium in tea. These strong complexes were not dissociated even in the presence of Chelex 100. In this case only a limiting value of the reaction coefficient could be evaluated. The presence of the very strong complexes was found in all the tea sample here considered. In two of the considered samples (one black and one green tea) a part of Al(III) was linked to less strong complexes, for example with a reaction coefficient 10(4.14) (tea 2, pH 4.20). The presence in the considered tea infusions of other substances able to complex aluminium was also detected, by the well known ligand titration procedure, at concentration ranging from 0.65 to 3.37 mM in three tea infusions, and at somewhat higher concentration in the case of the ready drink, which was also considered for comparison. 相似文献