全文获取类型
收费全文 | 488794篇 |
免费 | 6372篇 |
国内免费 | 2352篇 |
专业分类
电工技术 | 9008篇 |
综合类 | 757篇 |
化学工业 | 71023篇 |
金属工艺 | 20608篇 |
机械仪表 | 14455篇 |
建筑科学 | 11816篇 |
矿业工程 | 1992篇 |
能源动力 | 12362篇 |
轻工业 | 43173篇 |
水利工程 | 4605篇 |
石油天然气 | 7005篇 |
武器工业 | 46篇 |
无线电 | 59543篇 |
一般工业技术 | 94625篇 |
冶金工业 | 96164篇 |
原子能技术 | 10713篇 |
自动化技术 | 39623篇 |
出版年
2021年 | 3496篇 |
2019年 | 3307篇 |
2018年 | 5583篇 |
2017年 | 5592篇 |
2016年 | 5995篇 |
2015年 | 4145篇 |
2014年 | 7035篇 |
2013年 | 21493篇 |
2012年 | 11684篇 |
2011年 | 16340篇 |
2010年 | 12929篇 |
2009年 | 14697篇 |
2008年 | 15438篇 |
2007年 | 15576篇 |
2006年 | 13747篇 |
2005年 | 12707篇 |
2004年 | 12507篇 |
2003年 | 12261篇 |
2002年 | 12031篇 |
2001年 | 12195篇 |
2000年 | 11373篇 |
1999年 | 12276篇 |
1998年 | 30971篇 |
1997年 | 21853篇 |
1996年 | 16741篇 |
1995年 | 12624篇 |
1994年 | 11129篇 |
1993年 | 11045篇 |
1992年 | 7931篇 |
1991年 | 7668篇 |
1990年 | 7197篇 |
1989年 | 7083篇 |
1988年 | 6776篇 |
1987年 | 5946篇 |
1986年 | 5902篇 |
1985年 | 6715篇 |
1984年 | 6135篇 |
1983年 | 5642篇 |
1982年 | 5284篇 |
1981年 | 5319篇 |
1980年 | 5150篇 |
1979年 | 4840篇 |
1978年 | 4877篇 |
1977年 | 5708篇 |
1976年 | 7931篇 |
1975年 | 4119篇 |
1974年 | 3999篇 |
1973年 | 4022篇 |
1972年 | 3338篇 |
1971年 | 2966篇 |
排序方式: 共有10000条查询结果,搜索用时 437 毫秒
961.
P. F. Prasolov 《Strength of Materials》1991,23(3):282-285
Based on the criteria of safety of the spherical portion of the deformation stresses and for the work of deformation on the limiting condition of a material a separation is made of the elastic energy of deformation of an anisotropic body. It is shown that in the general case of loading the components of the spherical portion of the stresses and strains are not equal to one third of their first invariants. The values of these components, as for the values of the deviator portion of the elastic potential, depend upon the stressed and strained state and the loading direction (deformation).Translated from Problemy Prochnosti, No. 3, pp. 38–40, March, 1991. 相似文献
962.
J. M. Parpia W. P. Kirk P. S. Kobiela Z. Olejniczak 《Journal of Low Temperature Physics》1985,60(1-2):57-72
The ac susceptibility of lanthanum-diluted cerium magnesium nitrate has been compared to the temperature scales as derived
from the (P, T) relation determined by Halperin and that was measured recently by Greywall. It is found that the susceptibility does
not obey a simple Curie-Weiss law over the temperature range between 1 and 50 mK. The results of these calibrations are also
used to determine the temperatures for the second-order phase transitions into the superfluid phases of3He at several pressures. TheseT
c(P) values are compared to results of earlier experiments that used thermometry based on the susceptibility of platinum as well
as other thermometry techniques. 相似文献
963.
964.
A. Vahid Shahidi I. Shih T. Araki C. H. Champness 《Journal of Electronic Materials》1985,14(3):297-310
Structural investigation on monocrystalline CuInSe2 samples has been made. From the single crystal results, the space group of CuInSe2 was confirmed to be Iˉ42d and the crystal solidification direction was investigated. Compositional uniformity of the ingots
was established by EPMA and it was found that the indium concentration was greater than that for copper. Systematic annealing
experiments were carried out in vacuum at different temperatures (as low as 160° C) and for different times. Large variation
in resistivity was observed after the annealing treatment. P-type samples were found to convert to n-type after the heat-treatments. 相似文献
965.
966.
967.
Due to their small size, mammalian oocytes and embryos pose unique problems during preparation for transmission electron microscopy. This paper outlines a method which combines protein embedding with centrifugation to locate the specimens on the face of a Beem capsule mould. This method facilitates both the processing of oocytes with minimal loss and rapid location of the specimens within the block for simultaneous sectioning, staining and examination. 相似文献
968.
969.
970.
We report impedance measurements on PVC matrix membranes which contain KBPh4 with varying proportions of valinomycin. In agreement with our earlier measurements the value of the bulk membrane resistance (Rb) is much larger in the presence of valinomycin, indicating that the mobility of K+ is greatly reduced by the valinomycin. Rb shows a linear variation with valinomycin/K+ ratio between 0 and 1, but it is invariant at higher valinomycin/K+ ratios. Thus there is no evidence for a special transport mechanism for K+ in these membranes. 相似文献