全文获取类型
收费全文 | 49004篇 |
免费 | 2195篇 |
国内免费 | 62篇 |
学科分类
工业技术 | 51261篇 |
出版年
2024年 | 92篇 |
2023年 | 388篇 |
2022年 | 838篇 |
2021年 | 1309篇 |
2020年 | 934篇 |
2019年 | 1114篇 |
2018年 | 1635篇 |
2017年 | 1631篇 |
2016年 | 1738篇 |
2015年 | 1358篇 |
2014年 | 1733篇 |
2013年 | 3446篇 |
2012年 | 2704篇 |
2011年 | 2919篇 |
2010年 | 2279篇 |
2009年 | 2187篇 |
2008年 | 2009篇 |
2007年 | 1785篇 |
2006年 | 1375篇 |
2005年 | 1210篇 |
2004年 | 1118篇 |
2003年 | 998篇 |
2002年 | 930篇 |
2001年 | 668篇 |
2000年 | 661篇 |
1999年 | 711篇 |
1998年 | 3191篇 |
1997年 | 2161篇 |
1996年 | 1434篇 |
1995年 | 840篇 |
1994年 | 688篇 |
1993年 | 765篇 |
1992年 | 280篇 |
1991年 | 285篇 |
1990年 | 204篇 |
1989年 | 227篇 |
1988年 | 220篇 |
1987年 | 200篇 |
1986年 | 165篇 |
1985年 | 215篇 |
1984年 | 169篇 |
1983年 | 131篇 |
1982年 | 163篇 |
1981年 | 178篇 |
1980年 | 190篇 |
1979年 | 97篇 |
1978年 | 97篇 |
1977年 | 350篇 |
1976年 | 744篇 |
1973年 | 84篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
83.
84.
85.
86.
Solution of temperature fields in hydrodynamics bearings by the numerical network method 总被引:1,自引:0,他引:1
Solution to the 2-D steady-state nonlinear heat conduction equation, involving cylindrical coordinates, applied to a plain bearing by a simple and versatile numerical technique based on network method is presented in this work. These advantages of the technique are necessary for the status evaluation of industrial machines during operation because time and computing resources are limited. The pressure field in the fluid is previously solved from the Reynolds equation by finite element method. The main difficulty is associated with the exponential dependency of the viscosity on temperature. The proposed model is very efficient and requires negligible computing times. Solutions are very close to the experimental and numerical results of other researchers. 相似文献
87.
RM Martín‐Aranda E Ortega‐Cantero ML Rojas‐Cervantes MA Vicente‐Rodríguez MA Baares‐Muoz 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(2):234-238
α,β‐Unsaturated nitriles have been synthesized by Knoevenagel condensation of a carbonylic compound with malononitrile, assisted by sonochemical irradiation. Two alkaline‐promoted clays (Li+‐ and Cs+‐exchanged saponites) have been employed as catalysts. The influence of the carbonylic compound (benzaldehyde or cyclohexanone) and the use of a solvent on the catalytic activity have been studied. Remarkable increase in the conversion values has been found when the reaction is activated by ultrasound, as compared with the thermal activation. In this green, solvent‐free procedure, α,β‐unsaturated nitriles have been produced in very high yields (97%) when the Cs+‐saponite is used as catalyst. Copyright © 2004 Society of Chemical Industry 相似文献
88.
Bei der Model Driven Architecture (MDA) bilden Modelle die zentralen Elemente des Softwareentwicklungsprozesses. Ziel ist es, plattformspezifische Modelle möglichst automatisiert aus plattformunabhängigen Modellen abzuleiten. Dadurch soll der Aufwand der Softwareentwicklung verringert und die Adaptierung an neue Technologien erleichtert werden.*Vorschläge an Prof. Dr. Frank Puppe oder Dieter Steinbauer Alle „Aktuellen Schlagwörter“ seit 1988 finden Sie unter: www.ai-wuerzburg.de/as 相似文献
89.
A new definition of the flooding point in a two-phase counter-current trickle bed column has been proposed. Based on this point a versatile correlation of liquid hold-up has been formulated. The coefficients of this correlation are invariant to the change of physical properties of liquid, type and size of the packing forming the bed and gas velocity. This conclusion has been reached from the analysis of experiments with four different liquids irrigating the bed and three types of packing of various size. The versatile correlation can be used also re-currently to calculate flooding hold-up and flooding liquid rate from two known values of liquid hold-up for a given gas rate. 相似文献
90.
Summary The nucleophilic substitution with C6H5SNa, at -30°C, is compared for five PVC samples with various contents of isotactic triads. The conversion curves consist of a very fast stage followed by a steady one. All the samples are found to behave in the same way except for the content of the structures involved in the fast period. This content is estimated by extrapolating the straight lines of the steady stages to zero time. The obtained values are found to be a linear function of the content of isotactic triads. The results, together with some earlier ones, allow for the content of the labile non-defect structures in PVC to be determined. 相似文献