全文获取类型
收费全文 | 236076篇 |
免费 | 5741篇 |
国内免费 | 781篇 |
专业分类
电工技术 | 3700篇 |
综合类 | 157篇 |
化学工业 | 39976篇 |
金属工艺 | 8862篇 |
机械仪表 | 6230篇 |
建筑科学 | 6324篇 |
矿业工程 | 992篇 |
能源动力 | 6188篇 |
轻工业 | 25555篇 |
水利工程 | 2239篇 |
石油天然气 | 3400篇 |
武器工业 | 8篇 |
无线电 | 22997篇 |
一般工业技术 | 43010篇 |
冶金工业 | 45829篇 |
原子能技术 | 4612篇 |
自动化技术 | 22519篇 |
出版年
2022年 | 1465篇 |
2021年 | 2848篇 |
2020年 | 2062篇 |
2019年 | 2485篇 |
2018年 | 4184篇 |
2017年 | 4147篇 |
2016年 | 4429篇 |
2015年 | 3236篇 |
2014年 | 4872篇 |
2013年 | 11912篇 |
2012年 | 7998篇 |
2011年 | 9925篇 |
2010年 | 7858篇 |
2009年 | 8466篇 |
2008年 | 8549篇 |
2007年 | 8204篇 |
2006年 | 6856篇 |
2005年 | 6236篇 |
2004年 | 5897篇 |
2003年 | 5432篇 |
2002年 | 5238篇 |
2001年 | 4866篇 |
2000年 | 4647篇 |
1999年 | 4942篇 |
1998年 | 14371篇 |
1997年 | 9893篇 |
1996年 | 7362篇 |
1995年 | 5283篇 |
1994年 | 4486篇 |
1993年 | 4424篇 |
1992年 | 2924篇 |
1991年 | 2842篇 |
1990年 | 2719篇 |
1989年 | 2752篇 |
1988年 | 2655篇 |
1987年 | 2373篇 |
1986年 | 2312篇 |
1985年 | 2677篇 |
1984年 | 2412篇 |
1983年 | 2194篇 |
1982年 | 2092篇 |
1981年 | 2178篇 |
1980年 | 2003篇 |
1979年 | 1974篇 |
1978年 | 1924篇 |
1977年 | 2414篇 |
1976年 | 3295篇 |
1975年 | 1663篇 |
1974年 | 1632篇 |
1973年 | 1706篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
961.
F. Wastin J. Rebizant J.P. Sanchez A. Blaise J. Goffart J.C. Spirlet C.T. Walker J. Fuger 《Journal of Alloys and Compounds》1994,210(1-2):83-89
Twelve new ternary intermetallic compounds of light actinide elements from Th to Pu, namely U4Tc7Si6, U4Tc7Ge6, Np4Ru7Ge6, U2Tc3Si5, Np2Re3Si5, Pu2Re3Si5, Th2Mo3Si4, U2Mo3Si4, U2Mo3Ge4, Np2Mo3Si4, Np2Mo3Ge4, and Pu2Mo3Si4, were obtained. The structures of these compounds are discussed as well as some preliminary physical property studies. Magnetic susceptibility measurements show that An2Mo3(Si or Ge)4 compounds are paramagnetic at all temperatures studied and that U4Tc7Si6 orders antiferromagnetically around 25 K. Mössbauer spectroscopy on Np4Ru7Ge6 does not show a magnetic splitting down to 4.2 K. 相似文献
962.
Translated from Izmeritel'naya Tekhnika, No. 2, pp. 45–46, February, 1992. 相似文献
963.
Finding new applications for ceramic materials requires a better knowledge of thermal fatigue behaviour. However, result-scattering inherent to thermal fatigue and duration of a thermal fatigue cycle lead to a lack of experimental results. For these reasons, we have developed a new approach that permits the determination of a relevant stress intensity factor exponent n with a minimum testing sample number. From knowledge of the distribution function of artificial cracks, the analytical formula of the failure probability F(N) can be completely determined. Thus, it is possible to calculate n from a correlation of F(N) with experimental results obtained for only one temperature difference. Correlations between theoretical curves F(N) and experimental results, conducted for two temperature differences, lead to the same value of n. This and the good agreement between the experimental points and the theoretical curves validate this new approach. 相似文献
964.
High-temperature oxide scale growth at the ceramic-metal interface is a major contributor to the thermomechanical resistance
of thermal barrier coatings for hot stages of gas turbines. In order to better understand this phenomenon, microstructural
observations of the alumina scales formed at 1100 and 1200 °C under air, between low-pressure plasma-sprayed NiCrAlY and air
plasma-sprayed ZrO2-8.5 wt % Y2O3, have been performed by classical and analytical transmission electron microscopy on transverse thin foil specimens. The
evolution of the oxide grain morphology from the metal-oxide to the oxide-oxide interface suggests that the scale growth principally
takes place at the metal-oxide interface. Segregation of yttrium at oxide grain boundaries has been detected as well as significant
quantities of zirconium inside the alumina grains. The oxide growth seems to be dominated by a classical grain-boundary oxygen
diffusion mechanism. The presence of zirconium inside the alumina grains also suggests that Al2O3 partially forms by chemical reduction of ZrO2 by AI. The comparison between the microstructures observed and that of alumina scales grown under similar conditions on bare
MCrAlY alloys gives some insight into how the ceramic top-coat modifies NiCrAlY high-temperature oxidation mechanisms. 相似文献
965.
Commercial poly(styrene-b-butadiene) copolymers (SBS) can act as effective compatibilizers in blends between high-impact polystyrene (HIPS) and polyethylene (PE), allowing a fine dispersion of PE in the polystyrene matrix, with a good balance of stiffness and impact strength. However, when processed under more severe conditions (e.g. in multiple extrusions, which simulate customer's product scrap recovery), the above blends show rather poor stability and their useful properties are rapidly lost. That undesirable effect is mainly due to cross-linking of SBS, which thus looses its compatibilizing activity. A correlation has been found between the time-to-cross-linking of SBS rubber in a Brabender mixer and the rapid decay of mechanical properties. The analysis of the mixing process and the morphology examinations of the final blend sample by TEM seem to support the above hypothesis. A significant reduction of block copolymer degradation has been achieved by means of a suitable stabilization. 相似文献
966.
Luiz F. Martha L. J. Gray A. R. Ingraffea 《International journal for numerical methods in engineering》1992,35(9):1907-1921
An efficient hypersingular boundary integral equation method for three-dimensional fracture mechanics was presented in a previous paper. The details of the numerical implementation of this method are further discussed herein. In particular, an algorithm for achieving the required differentiability of the crack surface displacement function is discussed. To illustrate the utility of the method, computational results for several strongly interacting multiple-crack geometries are presented. The calculated stress intensity factors are in excellent agreement with those obtained by an approximate analytical method due to Kachanov and Laures. 相似文献
967.
968.
969.
970.
Collusion attacks are a major issue in fingerprinting schemes for copyright protection. A new class of codes, called scattering codes, is presented which can be used to control colluders' strategy in collusions of size up to 3. Scattering codes can be combined with dual Hamming codes to obtain 3-secure fingerprinting codes much shorter than those resulting from Boneh-Shaw's general construction 相似文献