全文获取类型
收费全文 | 561414篇 |
免费 | 7641篇 |
国内免费 | 2945篇 |
专业分类
电工技术 | 10390篇 |
技术理论 | 5篇 |
综合类 | 3628篇 |
化学工业 | 83920篇 |
金属工艺 | 23673篇 |
机械仪表 | 17174篇 |
建筑科学 | 14047篇 |
矿业工程 | 2992篇 |
能源动力 | 13238篇 |
轻工业 | 46528篇 |
水利工程 | 5999篇 |
石油天然气 | 8901篇 |
武器工业 | 258篇 |
无线电 | 66536篇 |
一般工业技术 | 107524篇 |
冶金工业 | 94091篇 |
原子能技术 | 9986篇 |
自动化技术 | 63110篇 |
出版年
2021年 | 4375篇 |
2020年 | 3081篇 |
2019年 | 3841篇 |
2018年 | 19932篇 |
2017年 | 18822篇 |
2016年 | 16170篇 |
2015年 | 5340篇 |
2014年 | 8208篇 |
2013年 | 21755篇 |
2012年 | 15931篇 |
2011年 | 26346篇 |
2010年 | 21844篇 |
2009年 | 20771篇 |
2008年 | 23034篇 |
2007年 | 24019篇 |
2006年 | 14911篇 |
2005年 | 14045篇 |
2004年 | 13021篇 |
2003年 | 12962篇 |
2002年 | 11941篇 |
2001年 | 12035篇 |
2000年 | 11211篇 |
1999年 | 11583篇 |
1998年 | 28040篇 |
1997年 | 19954篇 |
1996年 | 15263篇 |
1995年 | 11442篇 |
1994年 | 10417篇 |
1993年 | 10232篇 |
1992年 | 7554篇 |
1991年 | 7285篇 |
1990年 | 7168篇 |
1989年 | 6936篇 |
1988年 | 6669篇 |
1987年 | 5687篇 |
1986年 | 5610篇 |
1985年 | 6217篇 |
1984年 | 5900篇 |
1983年 | 5577篇 |
1982年 | 5021篇 |
1981年 | 5115篇 |
1980年 | 4817篇 |
1979年 | 4835篇 |
1978年 | 4538篇 |
1977年 | 5160篇 |
1976年 | 6883篇 |
1975年 | 3950篇 |
1974年 | 3776篇 |
1973年 | 3752篇 |
1972年 | 3226篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
It is suggested that the chord length distribution method could be useful for predicting double-bit upset rates in certain circumstances. A chord length distribution function for simultaneous path lengths in two parallelepipeds, applicable to a unidirectional flux, is derived. A proof of the system is outlined for the case under consideration 相似文献
82.
83.
J-M Choe 《欧洲信息系统杂志》2002,11(2):142-158
This study empirically examined the organisational learning effects of the nonfinancial performance information provided by management accounting information systems (MAISs) under advanced manufacturing technology (AMT). In this study, a target costing system and the frequent and quick reporting of information were considered the facilitators of learning. First, we examined the relationships between AMT level and the amount of nonfinancial performance information produced by MAISs. The empirical results showed that there are significant positive relationships between the level of AMT and nonfinancial performance information. With a systems approach, we also proved the impact of the relationships among AMT levels, nonfinancial performance information and learning facilitators on the organisational performance of a firm. The results of our research suggest that under a high level of AMT, for the provision of information to result in an increase of performance through organisational learning, a target costing system must be introduced and a large amount of information should be provided frequently and quickly. The results of this study also showed that although AMT level may be low, fairly well-arranged facilitators and a moderately large amount of information may be necessary for the improvement of performance. In conclusion, effective organisational learning depends on the provision of relevant information as well as efficient learning support mechanisms. 相似文献
84.
I. N. Polandov V. K. Novik O. K. Gulish B. P. Bogomolov V. B. Morozov 《Measurement Techniques》1989,32(9):888-890
Translated from Izmeritel'naya Tekhnika, No. 9, pp. 34–35, September, 1989. 相似文献
85.
M. Polák M. Majoro F. Hanic J. Pitel M. Kedrová P. Kottman J. Talapa L. Vencel 《Journal of Superconductivity》1989,2(2):219-233
A method for contactless measurement of the shielding critical current density and its dependence on the external magnetic field is described and analyzed. The obtained values are compared with those measured resistively on two different samples. It is shown that the shielding critical current densityJ
cs
and the intergranular transport current densityJ
cr
are identical if the measurement conditions are similar. A degradation ofJ
cs
measured in the external field with AC ripple has been observed. 相似文献
86.
Containment structures have several regions in which the continuity of the cylindrical pressure boundary is interrupted, e.g., shell penetrations, discontinuous stiffeners, and changes in the shell thickness. Significant strain concentrations can occur in these areas of discontinuity. The Sandia National Laboratories 1:8-scale steel containment equipment hatch was analyzed as an example of an eccentricity at a stiffener intersection.A portion of the as-built 1:8-scale model was modeled with the ANSYS general purpose finite element program using triangular, thin shell finite elements. The overall size of the model was determined from Saint-Venant type considerations of the stress field around the hatch. Shell elements were used to model the ring and formed stiffeners. Geometric and material nonlinear behavior were included. The model was loaded using discrete load steps up to a pressure of 165 psig. At this pressure, the maximum strain was 19.7 percent in the formed stiffener near its intersection with the ring stiffener. The finite element solution demonstrated the very localized nature of the strain field near the ring/formed stiffener intersection.In an attempt to reduce analysis costs, a small portion of the 1:8-scale model immediately surrounding the ring/formed stiffener intersection was selected for further analysis. Two smaller models, a ring/formed stiffener intersection and a ring/circular stiffener intersection, were studied. The models were significantly smaller than the regions used previously. A comparison of the two intersection models showed that the circular stiffener is a more efficient configuration. 相似文献
87.
88.
89.
Translated from Atomnaya Énergiya, Vol. 67, No. 2, pp. 97–100, August, 1989. 相似文献
90.