全文获取类型
收费全文 | 13758篇 |
免费 | 1239篇 |
国内免费 | 872篇 |
专业分类
电工技术 | 746篇 |
技术理论 | 1篇 |
综合类 | 1198篇 |
化学工业 | 2091篇 |
金属工艺 | 740篇 |
机械仪表 | 873篇 |
建筑科学 | 1509篇 |
矿业工程 | 349篇 |
能源动力 | 394篇 |
轻工业 | 584篇 |
水利工程 | 521篇 |
石油天然气 | 1467篇 |
武器工业 | 62篇 |
无线电 | 942篇 |
一般工业技术 | 1451篇 |
冶金工业 | 858篇 |
原子能技术 | 76篇 |
自动化技术 | 2007篇 |
出版年
2024年 | 49篇 |
2023年 | 136篇 |
2022年 | 284篇 |
2021年 | 355篇 |
2020年 | 416篇 |
2019年 | 387篇 |
2018年 | 303篇 |
2017年 | 443篇 |
2016年 | 501篇 |
2015年 | 509篇 |
2014年 | 904篇 |
2013年 | 730篇 |
2012年 | 952篇 |
2011年 | 1089篇 |
2010年 | 729篇 |
2009年 | 867篇 |
2008年 | 731篇 |
2007年 | 937篇 |
2006年 | 882篇 |
2005年 | 656篇 |
2004年 | 600篇 |
2003年 | 563篇 |
2002年 | 491篇 |
2001年 | 387篇 |
2000年 | 360篇 |
1999年 | 318篇 |
1998年 | 233篇 |
1997年 | 190篇 |
1996年 | 163篇 |
1995年 | 139篇 |
1994年 | 89篇 |
1993年 | 61篇 |
1992年 | 50篇 |
1991年 | 38篇 |
1990年 | 41篇 |
1989年 | 33篇 |
1988年 | 15篇 |
1987年 | 16篇 |
1986年 | 14篇 |
1985年 | 16篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1979年 | 15篇 |
1978年 | 9篇 |
1964年 | 13篇 |
1957年 | 12篇 |
1956年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
The present empirical investigation had a 3-fold purpose: (a) to cross-validate L. R. Offermann, J. K. Kennedy, and P. W. Wirtz's (1994) scale of Implicit Leadership Theories (ILTs) in several organizational settings and to further provide a shorter scale of ILTs in organizations; (b) to assess the generalizability of ILTs across different employee groups, and (c) to evaluate ILTs' change over time. Two independent samples were used for the scale validation (N1 = 500 and N2 = 439). A 6-factor structure (Sensitivity, Intelligence, Dedication, Dynamism, Tyranny, and Masculinity) was found to most accurately represent ELTs in organizational settings. Regarding the generalizability of ILTs, although the 6-factor structure was consistent across different employee groups, there was only partial support for total factorial invariance. Finally, evaluation of gamma, beta, and alpha change provided support for ILTs' stability over time. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
3.
In the oxidation of TiAl alloys, the role of scale-growth stresses formed during oxidation has, thus far, been unknown. In the present paper the oxide-growth stresses were investigated by the deflection-test method in monofacial oxidation (DTMO) accompanied by acoustic-emission measurements. On unmodified surfaces the growth stresses are compressive and reach levels of around –100 MPa. At the same time, significant acoustic emission occurs indicating that even under isothermal conditions, stresses are relieved by a scale-cracking mechanism. For oxide scales on TiAl surfaces, which had been ion implanted with chlorine before oxidation, a very thin protective alumina layer is formed which, however, develops growth stresses in the range of several GPa, accompanied by intensive acoustic emission. In all stress–time curves, a dynamic situation is observed. This consists of phases of stress relief by scale microcracking and phases of stresses increase due to crack healing and further oxide growth. As a result, the level of stress as a function of oxidation time, is characterized by an oscillating course. 相似文献
4.
A kind of complex additive mainly containing Al, Mg, F, and O was prepared. The synthetical performances of the property-modified prebaked anodes containing additives were tested in laboratory. On the basis of ideal testing results obtained, a large number of industrial prebaked property-modified anodes are prepared in a large-scale aluminum company. Further more, they are all used in 160 kA prebaked anode aluminum electrolysis cells. The statistic result show that, compared with common anodes, the property-modified ones enhance current by 11.6 kg per ton aluminum averagely. 相似文献
5.
A probabilistic model for cleavage fracture with a length scale--parameter estimation and predictions of stationary crack experiments 总被引:1,自引:0,他引:1
This study presents a large experimental investigation in the transition temperature region on a modified A508 steel. Tests were carried out on single-edge-notch-bend specimens with three different crack depth over specimen width ratios to capture the strong constraint effect on fracture toughness. Three test temperatures were considered, covering a range of 85 °C. All specimens failed by cleavage fracture prior to ductile tearing. A recently proposed probabilistic model for the cumulative failure by cleavage was applied to the comprehensive sets of experimental data. This modified weakest link model incorporates a length scale, which together with a threshold stress reduce the scatter in predicted toughness distributions as well as introduces a fracture toughness threshold value. Model parameters were estimated by a robust procedure, which is crucial in applications of probabilistic models to real structures. The conformity between predicted and experimental toughness distributions, respectively, were notable at all the test temperatures. 相似文献
6.
本文主要介绍了在动态汽车衡的试验过程中不确定度来源,并以动态试验为例重点介绍了计算各分量的标准不确定度、合成标准不确定度以及扩展不确定度的方法. 相似文献
7.
Yun‐Seok Cho Bheong‐Uk Lee Kye‐Heon Oh 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(9):1211-1217
BACKGROUND: Environmental contamination by nitroaromatic compounds such as 2,4,6‐trinitrotoluene (TNT), hexahydro‐1,3,5‐trinitro‐1,3,5‐s‐triazine (RDX), atrazine, and/or simazine (TRAS) generated as waste from military and agricultural activities is a serious worldwide problem. Microbiological treatment of these compounds is an attractive method because many explosives and herbicides are biodegradable and the process can be made cost‐effective. We explored the feasibility of using cultures of Pseudomonas putida HK‐6 for simultaneous degradation of TRAS with the aim of microbial application in wastewater treatment in bench‐scale bioreactors. RESULTS: Experiments were conducted to study the effects of supplemental carbons, nitrogens, and Tween‐80 on the degradation of Ps. putida HK‐6 in media containing TRAS as target substrate(s). The most effective TRAS degradation was shown in the presence of molasses. Addition of nitrogen sources produced a delayed effect for the target substrate(s). Tween‐80 enhanced the degradation of target substrate(s). Simultaneous degradation of these compounds proceeded to completion within the given period. CONCLUSIONS: Ps. putida HK‐6 was capable of growth with TRAS, and the effects of supplements on TRAS degradation and simultaneous TRAS degradation were evaluated in bench‐scale bioreactors. The results of this study have practical applications in the processes of industrial waste stream treatment where the disposal of TRAS may be problematic. Copyright © 2008 Society of Chemical Industry 相似文献
8.
9.
官泓 《有色冶金设计与研究》2003,24(3):49-51
阐述水厂设计中对水厂规模、水源地、净水厂位置及净水工艺的确定过程,根据原水的特点,通过分析对无阀滤池进行改良。 相似文献
10.