全文获取类型
收费全文 | 450730篇 |
免费 | 4342篇 |
国内免费 | 1338篇 |
专业分类
化学 | 234013篇 |
晶体学 | 7328篇 |
力学 | 20978篇 |
综合类 | 9篇 |
数学 | 52231篇 |
物理学 | 141851篇 |
出版年
2020年 | 3507篇 |
2019年 | 3970篇 |
2018年 | 5271篇 |
2017年 | 5179篇 |
2016年 | 7622篇 |
2015年 | 4606篇 |
2014年 | 7481篇 |
2013年 | 18997篇 |
2012年 | 14147篇 |
2011年 | 17390篇 |
2010年 | 12384篇 |
2009年 | 12221篇 |
2008年 | 16226篇 |
2007年 | 16346篇 |
2006年 | 15400篇 |
2005年 | 13896篇 |
2004年 | 12863篇 |
2003年 | 11532篇 |
2002年 | 11418篇 |
2001年 | 12765篇 |
2000年 | 9828篇 |
1999年 | 7656篇 |
1998年 | 6687篇 |
1997年 | 6538篇 |
1996年 | 6227篇 |
1995年 | 5719篇 |
1994年 | 5801篇 |
1993年 | 5621篇 |
1992年 | 6103篇 |
1991年 | 6265篇 |
1990年 | 5996篇 |
1989年 | 5804篇 |
1988年 | 5929篇 |
1987年 | 5707篇 |
1986年 | 5390篇 |
1985年 | 7350篇 |
1984年 | 7675篇 |
1983年 | 6368篇 |
1982年 | 6631篇 |
1981年 | 6534篇 |
1980年 | 6420篇 |
1979年 | 6501篇 |
1978年 | 6879篇 |
1977年 | 6687篇 |
1976年 | 6851篇 |
1975年 | 6323篇 |
1974年 | 6352篇 |
1973年 | 6527篇 |
1972年 | 4585篇 |
1971年 | 3843篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Silver nitrate-acetonitrile and π iodine-benzene complexes in thermotropic liquid crystals have been studied by 1H, 2H, and 13C NMR spectroscopy and by optical microscopy. Evidence for at least two silver complexes in each liquid crystal is presented. 相似文献
992.
A. R. Kuznetsov S. G. Lunter S. I. Nikitina A. G. Plyukhin Yu. K. Fedorov 《Journal of Applied Spectroscopy》1992,56(1):68-72
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 56, No. 1, pp. 90–95, January, 1992. 相似文献
993.
G. V. Plyatsko V. N. Maksimovich L. V. Khomlyak 《Journal of Mathematical Sciences》1992,62(1):2518-2523
We solve the thermoplastic problem for a semi-infinite plate under local nonstationary heating by heat sources. The physical equations are taken to be the relations of the nonisothermic theory of plastic flow associated with the Mises fluidity condition. The solution of the problem is constructed by the method of integral equations and the self-correcting method of sequential loading, where time is taken as the loading parameter. We carry out numerical computations of the stresses in the case of heating a plate with heat output by normal-circular heat sources. We study the problem of optimization of heating regimes in order to introduce favorable residual compressive stresses (from the point of view of hardness) in a given region of a half-plane. Two figures.Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 27, 1988, pp. 29–34. 相似文献
994.
995.
We examine differences between3H binding energies obtained by solving the Faddeev equations using standard partial-wave expansion procedures and results from solving the Schrödinger equation by means of the coupled-rearrangement-channel variational method. Variational bounds generated from Faddeev solutions for several contemporary, realistic potential models are presented as a function of the number of partial waves retained in the potential expansion. We demonstrate that the Faddeev wave function yields an optimal variational bound for the partial-wave truncated potential from which it is generated, but it does not yield optimal bounds for the full Hamiltonian or when the potential is partial-wave truncated at a different level. Finally, qualitative differences between3H solutions for static models such as the AV14 and RSC potentials and for momentum-dependent models such as the Nijmegen soft-core and Paris potentials are explored, and comparison is made with solutions for the RSC/TM two-body-force plus three-body-force model. 相似文献
996.
997.
Coulomb systems in which the particles interact through thed-dimensional Coulomb potential but are confined in a flat manifold of dimensiond–1 are considered. The actual Coulomb potential acting is defined by particular boundary conditions involving a characteristic macroscopic distanceW in the direction perpendicular to the manifold: either it is periodic of periodW in that direction, or it vanishes on one ideal conductor wall parallel to the manifold at a distanceW from it, or it vanishes on two parallel walls at a distanceW from each other with the manifold equidistant from them. Under the assumptions that classical equilibrium statistical mechanics is applicable and that the system has the macroscopic properties of a conductor, it is shown that the suitably smoothed charge correlation function is universal, and that the free energy and the grand potential have universal dependences onW (universal means independent of the microscopic detail). The casesd=2 are discussed in detail, and the generic results are checked on an exactly solvable model. The cased=3 of a plane parallel to an ideal conductor is also explicitly worked out.Laboratoire associé au Centre National de la Recherche Scientifique-URA D0063. 相似文献
998.
A. S. Lobach B. P. Tarasov Yu. M. Shul'ga A. A. Perov A. N. Stepanov 《Russian Chemical Bulletin》1996,45(2):464-465
Fullerene deuteride was obtained by the reaction of deuterium with solid palladium fulleride C60Pd4.9 under fairly mild conditions. The compound was identified by FD-MS, UV-Vis and IR spectroscopies, and TLC.Translated from Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 483–484, February, 1996 相似文献
999.
1000.
A short-term load-forecasting system has been developed to predictload demand for the Irish Electricity Supply Board from 1 to10 days in advance. Model output is acceptably accurate at mosttimes, but special days such as public holidays and the Easterweekend etc. require individual treatment. The basic model usedin everyday load forecasting is presented first, and specialdays when this model fails in accuracy are then examined andtreated separately using rule-based procedures. These proceduresare based on identified relationships between weather conditionsand prevailing daily load shapes. Comparisons are made betweenthe forecasts for these special days as given by the standardmodel and the ruled-based procedures. 相似文献