全文获取类型
收费全文 | 215228篇 |
免费 | 1773篇 |
国内免费 | 627篇 |
专业分类
化学 | 117924篇 |
晶体学 | 3270篇 |
力学 | 8349篇 |
综合类 | 6篇 |
数学 | 23305篇 |
物理学 | 64774篇 |
出版年
2020年 | 1970篇 |
2019年 | 2263篇 |
2018年 | 3205篇 |
2017年 | 3113篇 |
2016年 | 4267篇 |
2015年 | 2371篇 |
2014年 | 3818篇 |
2013年 | 9260篇 |
2012年 | 6891篇 |
2011年 | 8434篇 |
2010年 | 6071篇 |
2009年 | 5921篇 |
2008年 | 8136篇 |
2007年 | 8206篇 |
2006年 | 7629篇 |
2005年 | 6937篇 |
2004年 | 6166篇 |
2003年 | 5643篇 |
2002年 | 5497篇 |
2001年 | 5939篇 |
2000年 | 4684篇 |
1999年 | 3470篇 |
1998年 | 3007篇 |
1997年 | 3033篇 |
1996年 | 2823篇 |
1995年 | 2319篇 |
1994年 | 2419篇 |
1993年 | 2450篇 |
1992年 | 2595篇 |
1991年 | 2657篇 |
1990年 | 2559篇 |
1989年 | 2533篇 |
1988年 | 2463篇 |
1987年 | 2434篇 |
1986年 | 2357篇 |
1985年 | 3037篇 |
1984年 | 3194篇 |
1983年 | 2559篇 |
1982年 | 2827篇 |
1981年 | 2703篇 |
1980年 | 2503篇 |
1979年 | 2718篇 |
1978年 | 2833篇 |
1977年 | 2856篇 |
1976年 | 2832篇 |
1975年 | 2687篇 |
1974年 | 2665篇 |
1973年 | 2810篇 |
1972年 | 1875篇 |
1967年 | 1830篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Univ.-Prof. Dr-Ing. J. Betten Univ.-Prof. Dr.-Ing. E. El-Magd Dr.-Ing. S. C. Meydanli Dipl.-Ing. P. Palmen 《Archive of Applied Mechanics (Ingenieur Archiv)》1995,65(2):121-132
Übersicht Ziel der Untersuchung ist es, den Einfluß von Kriechschädigung und Belastungsvorgeschichte auf das weitere Kriechverhalten nach einer Änderung der Belastungsrichtung zu bestimmen. Die ermittelten Kriechbruchzeiten werden stark von der Änderung der Belastungsrichtung beeinflußt. Dieses Verhalten wird mit einer tensoriell nichtlinearen Theorie erklärt, indem man den Einfluß der Vorschädigung mit einem zweistufigen Tensor darstellt.
相似文献
相似文献
962.
We study the critical behavior of certain two-parameter families of correlated percolation models related to the Ising model on the triangular and square lattices, respectively. These percolation models can be considered as interpolating between the percolation model given by the + and – clusters and the Fortuin-Kasteleyn correlated percolation model associated to the Ising model. We find numerically on both lattices a two-dimensional critical region in which the expected cluster size diverges, yet there is no percolation. 相似文献
963.
A. S. Peregudov L. N. Usatova E. I. Smyslova E. I. Fedin D. N. Kravtsov 《Russian Chemical Bulletin》1995,44(8):1513-1519
It has been shown by the19F NMR method that the relative polarities of nitrogenelement bonds in 2-(4-fluorophenyl)benzimidazole and its PhHg and PPh3Au derivatives increase in the order N-H19F NMR. It has been found that these reactions occur by a bimolecular associative mechanism and that the N-H bond is substantially less reactive than the N-Hg and N-Au bonds, which have identical reactivities within the limits of sensitivity of the method used.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1574–1580, August, 1995.This work was carried out with financial support from the Russian Foundation for Basic Research (Project No. 93-03-5528). 相似文献
964.
Summary A Modified-Melt-Powder-Melt-Growth (MMPMG) technique has been developed for the preparation of melt-textured Y-Ba−Cu−O pellets.
To test their performances, the samples were characterized with respect to their microstructure, pinning strength and interaction
force with permanent magnets. A superconducting magnetic bearing was built and integrated in a levitating flywheel system
for energy storage.
Paper presented at the “VII Congresso SATT?, Torino, 4–7 October 1994.
Under a Fondazione Confalonieri grant. 相似文献
965.
We make a thorough non-covariant analysis of the derivation of the equation of motion for a charged particle, including radiation reaction, by means of a simple model for the charge: a dumbbell. This model and our method to expand retarded quantities, based on complex-variable theory, allow us to avoid some of the usual approximations, so we can show several features of the radiation reaction problem. 相似文献
966.
Jean-Jacques Jutier Even Lemieux Robert E. Prud'homme 《Journal of Polymer Science.Polymer Physics》1988,26(6):1313-1329
The miscibility of polyester/nitrocellulose blends was investigated by differential scanning calorimetry and Fourier-transform infrared (FTIR) spectroscopy. Two nitrocelluloses (NC) derived from wood and having different nitrogen contents (12.62 and 13.42%) were used. On the basis of the glass transition temperature criterion, poly(?-caprolactone) (PCL), poly(valerolactone), poly(ethylene adipate), and poly(butylene adipate) are miscible with nitrocellulose, whereas poly(α-methyl α-propyl β-propiolactone) and poly(α-methyl β-proiolactone) are immiscible. The Tg versus composition curves of PCL/NC blends do not follow a monotone function but exhibit a singular point at a critical PCL volume fraction of 0.51 for NC-1342 and 0.45 for NC-1262 in agreement with Kovacs' theory. A shift of 17 cm-1 of the carbonyl stretching band was observed with PCL/NC blends and is taken as evidence for hydrogen bonding interaction between the PCL carbonyl group and NC hydroxyl group. The frequency difference between the free hydroxyl absorbance and the absorbances of the hydrogen-bonded species was found to be 85 cm-1 in pure NC and 125 cm-1 in PCL/NC blends; it indicates that the average strength of this interaction is stronger than the corresponding self-associated hydrogen bonding in pure NC. The presence of a dipole-dipole interaction between the nitrate-ester groups of NC and the carbonyl groups of the polyesters is reported. The relative strength of the hydrogen bonding and dipole-dipole interactions is discussed and correlated with polymer miscibility. 相似文献
967.
E. I. Timoshenko 《Mathematical Notes》1995,57(4):414-420
Translated from Matematicheskie Zametki, Vol. 47, No. 4, pp. 597–605, April, 1995. 相似文献
968.
969.
970.