全文获取类型
收费全文 | 39976篇 |
免费 | 1722篇 |
国内免费 | 62篇 |
专业分类
电工技术 | 416篇 |
综合类 | 34篇 |
化学工业 | 7984篇 |
金属工艺 | 764篇 |
机械仪表 | 810篇 |
建筑科学 | 2090篇 |
矿业工程 | 122篇 |
能源动力 | 1213篇 |
轻工业 | 3583篇 |
水利工程 | 456篇 |
石油天然气 | 128篇 |
武器工业 | 5篇 |
无线电 | 2813篇 |
一般工业技术 | 6763篇 |
冶金工业 | 7044篇 |
原子能技术 | 293篇 |
自动化技术 | 7242篇 |
出版年
2023年 | 239篇 |
2022年 | 422篇 |
2021年 | 854篇 |
2020年 | 560篇 |
2019年 | 741篇 |
2018年 | 931篇 |
2017年 | 836篇 |
2016年 | 963篇 |
2015年 | 871篇 |
2014年 | 1207篇 |
2013年 | 2654篇 |
2012年 | 1930篇 |
2011年 | 2374篇 |
2010年 | 1855篇 |
2009年 | 1732篇 |
2008年 | 1987篇 |
2007年 | 1945篇 |
2006年 | 1764篇 |
2005年 | 1562篇 |
2004年 | 1287篇 |
2003年 | 1210篇 |
2002年 | 1133篇 |
2001年 | 760篇 |
2000年 | 593篇 |
1999年 | 658篇 |
1998年 | 716篇 |
1997年 | 667篇 |
1996年 | 612篇 |
1995年 | 620篇 |
1994年 | 577篇 |
1993年 | 539篇 |
1992年 | 522篇 |
1991年 | 311篇 |
1990年 | 442篇 |
1989年 | 413篇 |
1988年 | 338篇 |
1987年 | 364篇 |
1986年 | 320篇 |
1985年 | 427篇 |
1984年 | 424篇 |
1983年 | 327篇 |
1982年 | 305篇 |
1981年 | 290篇 |
1980年 | 277篇 |
1979年 | 275篇 |
1978年 | 250篇 |
1977年 | 231篇 |
1976年 | 221篇 |
1975年 | 200篇 |
1974年 | 176篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Serran G.; Fernandez Y.; Marshall W. L.; Mann R. E. 《Canadian Metallurgical Quarterly》2003,34(4):368
How critical is the therapeutic alliance in the treatment of sexual offenders? To date such process issues have been neglected in the field of sex offender treatment. This article reviews the literature on the influence on behavior change of therapist features, clients' perceptions, and the therapeutic alliance. Among the many therapist features identified as helpful are empathy, warmth, and being directive and rewarding. Therapists who are aggressively confrontational appear not to foster beneficial changes in their clients. These issues are directly related to treatment issues faced by therapists who work with sexual offenders, such as dealing with cognitive distortions, lack of empathy, and lack of motivation to change. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
82.
Linking Entrepreneurship to Growth: The Case of West Germany 总被引:1,自引:0,他引:1
83.
84.
85.
86.
This article is a brief summary of the Discussion session held after the presentation of the preceding papers at the conference organized by the Industrial Carbon and Graphite Group of the Society of Chemical Industry, London, March 1984. 相似文献
87.
M A M Maqueda Sergio A Martinez D Narváez Miriam G Rodriguez Ricardo Aguilar Victor M Herrero 《Water science and technology》2006,53(11):135-142
The Mexican petrochemical industry, Morelos S.A. de C.V., is one of the biggest and more important petroleum industries in Mexico and Latin America. It has an activated sludge system to treat its wastewater flow, which is approximately 7,000 m3/d. The wastewater contains volatile organic carbon substances classified as toxics. The old surface aeration system was changed for fine bubble diffusers; however, one major drawback of the new aeration system is that the temperature in the bioreactor has increased due to the compression of the air, which at the compressor exit reaches 85 degrees C. This effect results in the temperature in the bioreactor attaining 32 degrees C during the fall, whereas in the spring and summer, the bioreactor temperature reaches higher values than 40 degrees C. The high temperatures reduce the microorganism activity and cause a higher volatilisation rate of volatile compounds, among other effects, which affect the performance of the biological treatment. This work was performed to obtain a better modelling of the wastewater treatment from the petrochemical industry. The model describes the effect of the temperature on the performance of the biological treatment. The model was obtained from tests that were carried out in laboratory reactors with 14 L capacity, which were operated at different temperatures (from 30 to 45 degrees C), with the same wastewater and conditions as the actual system. 相似文献
88.
Uwe Kruger David Antory Juergen Hahn George W. Irwin Geoff McCullough 《Computers & Chemical Engineering》2005,29(11-12):2355
Although principal component analysis (PCA) is an important tool in standard multivariate data analysis, little interest has been devoted to assessing whether the underlying relationship within a given variable set can be described by a linear PCA model or whether nonlinear PCA must be utilized. This paper addresses this deficiency by introducing a nonlinearity measure for principal component models. The measure is based on the following two principles: (i) the range of recorded process operation is divided into smaller regions; and (ii) accuracy bounds are determined for the sum of the discarded eigenvalues. If this sum is within the accuracy bounds for each region, the process is assumed to be linear and vice versa. This procedure is automated through the use of cross-validation. Finally, the paper shows the utility of the new nonlinearity measure using two simulation studies and with data from an industrial melter process. 相似文献
89.
Pablo Esquinazi Miguel A. Ramos Reinhard König 《Journal of Low Temperature Physics》2004,135(1-2):27-38
We discuss the strain dependence of the acoustic properties of amorphous metals in both normal and superconducting states, in the temperature range 0.1 mK<T<1 K. A crossover is found when the strain energy is of the order of the effective interaction energy between tunneling systems at the corresponding temperature. Our results provide clear evidence for the interaction between tunneling systems, whose energy is in quantitative agreement with theoretical expectations, and reveal that without the knowledge of the corresponding strain dependences, the measured temperature dependences below ~50 mK of the acoustic properties of disordered solids are rather meaningless. 相似文献
90.