全文获取类型
收费全文 | 19028篇 |
免费 | 1638篇 |
国内免费 | 973篇 |
专业分类
电工技术 | 372篇 |
综合类 | 1365篇 |
化学工业 | 4274篇 |
金属工艺 | 618篇 |
机械仪表 | 1433篇 |
建筑科学 | 672篇 |
矿业工程 | 774篇 |
能源动力 | 1369篇 |
轻工业 | 872篇 |
水利工程 | 334篇 |
石油天然气 | 6124篇 |
武器工业 | 323篇 |
无线电 | 218篇 |
一般工业技术 | 1496篇 |
冶金工业 | 512篇 |
原子能技术 | 257篇 |
自动化技术 | 626篇 |
出版年
2024年 | 68篇 |
2023年 | 296篇 |
2022年 | 496篇 |
2021年 | 553篇 |
2020年 | 554篇 |
2019年 | 586篇 |
2018年 | 518篇 |
2017年 | 594篇 |
2016年 | 761篇 |
2015年 | 769篇 |
2014年 | 1032篇 |
2013年 | 1240篇 |
2012年 | 1279篇 |
2011年 | 1443篇 |
2010年 | 1023篇 |
2009年 | 909篇 |
2008年 | 798篇 |
2007年 | 1057篇 |
2006年 | 1159篇 |
2005年 | 1048篇 |
2004年 | 888篇 |
2003年 | 792篇 |
2002年 | 725篇 |
2001年 | 546篇 |
2000年 | 485篇 |
1999年 | 398篇 |
1998年 | 344篇 |
1997年 | 270篇 |
1996年 | 249篇 |
1995年 | 214篇 |
1994年 | 135篇 |
1993年 | 88篇 |
1992年 | 65篇 |
1991年 | 55篇 |
1990年 | 59篇 |
1989年 | 30篇 |
1988年 | 24篇 |
1987年 | 17篇 |
1986年 | 21篇 |
1985年 | 7篇 |
1984年 | 10篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 9篇 |
1980年 | 5篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1959年 | 5篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
��ɫ������������ѡ�꾮Һ����ģʽ 总被引:1,自引:1,他引:0
本文应用灰色关联分析方法,对70种不同类型和组成的钻井液,进行了两参数流变模式优选及评价。与现行方法比较的结果表明此方法与现行结果的吻合度高,并有新颖、数据要求量少、结论易于比较等优点。 相似文献
92.
93.
A continuous process for the extraction of sunflower oil using supercritical CO2, featuring multiple extractors, one oil separator and three cascaded CO2 recovery vessels operating at different pressures, was devised and studied. For every single equipment of the plant making up the process a mathematical model was built. Experimental tests—consisting in measurements of oil solubility in supercritical CO2—were carried out in a laboratory-scale apparatus to characterise the behaviour of sunflower oil in the separation from the supercritical fluid. The mathematical model of the whole process was coded in the commercial gPROMS process modelling environment where both its simulation and optimisation—this latter assuming the overall oil production cost as the objective function—were carried out. The process- and economics-related results are discussed and compared with those obtained with traditional and cold-pressing extraction. 相似文献
94.
A. BETTERO M. R. ANGI F. GALIANO C. A. BENASSI 《International journal of cosmetic science》1985,7(1):1-8
To assess ocular irritancy caused by chemical and cosmetic products a reliable method based on evaluation of histamine (Hm) in tears is presented. Hm is measured at picomole levels by HPLC and fluorimetric detection after fluorescamine-HM derivatization. In order to avoid any uncontrolled irritation and stimulation of the conjunctiva during sample collection, a procedure of conjunctiva lavage was developed. A balanced salt solution (50 μl) containing a known amount of Hm-fluorophore as reference standard is instilled in the conjunctiva fornix. After a few seconds 20 μl of tear fluid is collected: 10 μl are immediately analysed and 10 μl after derivatization reaction. In this way it is possible to evaluate tear dilution and to assess Hm content in less than 10 minutes.
In a group of 20 normal subjects Hm has been determined in comparison with that of two volunteers after topical application of 50 μ of 0.2% and 0.4% sodium lauryl sulphate solution. A contact of 30 seconds of the cosmetic ingredient caused an immediate dose-dependent Hm release through a direct cytotoxic damage of cell membranes due to the surfactant action.
Évaluation de l'irritation occulaire due aux cosmétiques par la détermination de l'histamine lacrimale 相似文献
In a group of 20 normal subjects Hm has been determined in comparison with that of two volunteers after topical application of 50 μ of 0.2% and 0.4% sodium lauryl sulphate solution. A contact of 30 seconds of the cosmetic ingredient caused an immediate dose-dependent Hm release through a direct cytotoxic damage of cell membranes due to the surfactant action.
Évaluation de l'irritation occulaire due aux cosmétiques par la détermination de l'histamine lacrimale 相似文献
95.
A new method for characterization of stratified thermal energy stores (TES) that integrates both the first law and the second law concerns is presented here. The first law concern is incorporated into a quantity called energy response factor and the second law concern into an entropy generation ratio. A product of these two quantities is at the heart of the TES efficiency definitions. This approach removes the overemphasis of the existing methods either on the first or the second law of thermodynamics which often biases the characterization results. The information about the evolution of the temperature field of the system in time is the prerequisite of the new method. It may be obtained from experiments or from suitable numerical simulations. The current method can be easily integrated into computational fluid dynamic (CFD) simulations and thus facilitate CFD-based design analysis. As an example of such CFD-integrated analysis, a large-scale hot water seasonal heat store is numerically studied to identify the effects of aspect ratio, containment shape, internal structures, and containment size on their efficiency. The results suggest the effectiveness of the new method in deriving useful design insights. 相似文献
96.
97.
康山金矿地质地球化学特征及其成因 总被引:3,自引:1,他引:2
康山金矿产在豫西熊耳山古隆起区的结晶基底太华群和盖层中元古界熊耳群地层接触界面附近,矿体严格受构造破碎蚀变带控制。流体包裹体,稳定同位素等研究表明,成矿物质来自太华群变质岩,成矿流体的性质与变质热液截然不同,而与花岗岩浆热液相近似。该矿床的形成与燕山期发生的同构造-花岗岩浆期热液活动有关,金沉淀成矿阶段有大气水的混入。 相似文献
98.
介绍了在钻井液与油气层损害及保护研究领域里常用的数种具有推广应用价值的数学方法,说明了各种方法的基本原理及其在此研究领域中的具体应用成果。 相似文献
99.
A rapid and easy analysis method for polymers is presented. The method involves sample preparation by SFE, separation of the extracted compounds by SFC and simultaneous quantitative detection by FID, as well as identification of unknowns by MS. The applications illustrate how structural research work and routine polymer analysis can be done with this time saving method. 相似文献
100.
D. E. Wetzler P. F. Aramendía M. L. Japas R. Fernández-Prini 《International Journal of Thermophysics》1998,19(1):27-42
Thermal diffusivities of supercritical CO2 and C2H6 were determined over a wide density range with a photothermal technique. The thermal lens, formed by the degradation of the absorbed light energy as heat by the sample, allows the employment of a nonequilibrium method in the critical region. Controlling the refractive-index gradient, i.e., a density gradient, perturbations can be maintained at levels where convection is negligible. An easy-to-operate setup allowed us to measure thermal diffusivities in the density ranges 5 to 20 mol·dm–3 for CO2 at 308 and 313 K and 2 to 12 mol·dm–3 for C2H6 at 308 K with a standard precision of 15%. 相似文献