全文获取类型
收费全文 | 202044篇 |
免费 | 2241篇 |
国内免费 | 504篇 |
专业分类
化学 | 110588篇 |
晶体学 | 3647篇 |
力学 | 7996篇 |
综合类 | 11篇 |
数学 | 19201篇 |
物理学 | 63346篇 |
出版年
2020年 | 1724篇 |
2019年 | 1919篇 |
2018年 | 2236篇 |
2017年 | 2355篇 |
2016年 | 3515篇 |
2015年 | 2190篇 |
2014年 | 3548篇 |
2013年 | 9083篇 |
2012年 | 6507篇 |
2011年 | 8018篇 |
2010年 | 5701篇 |
2009年 | 5658篇 |
2008年 | 7158篇 |
2007年 | 7074篇 |
2006年 | 6696篇 |
2005年 | 6053篇 |
2004年 | 5523篇 |
2003年 | 5100篇 |
2002年 | 4868篇 |
2001年 | 6143篇 |
2000年 | 4623篇 |
1999年 | 3518篇 |
1998年 | 2746篇 |
1997年 | 2703篇 |
1996年 | 2594篇 |
1995年 | 2440篇 |
1994年 | 2331篇 |
1993年 | 2166篇 |
1992年 | 2829篇 |
1991年 | 2732篇 |
1990年 | 2673篇 |
1989年 | 2690篇 |
1988年 | 2713篇 |
1987年 | 2725篇 |
1986年 | 2591篇 |
1985年 | 3305篇 |
1984年 | 3314篇 |
1983年 | 2599篇 |
1982年 | 2710篇 |
1981年 | 2764篇 |
1980年 | 2534篇 |
1979年 | 2878篇 |
1978年 | 2860篇 |
1977年 | 2980篇 |
1976年 | 2817篇 |
1975年 | 2554篇 |
1974年 | 2511篇 |
1973年 | 2466篇 |
1972年 | 1703篇 |
1968年 | 1704篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Mark L. Agranovsky E. K. Narayanan 《Proceedings of the American Mathematical Society》2006,134(7):2117-2123
A test for a function to be a solution of an elliptic PDE is given in terms of extensions, as solutions, from the boundaries inside the domains belonging to an isotopic family. It generalizes a result of Ehrenpreis for spheres moved along a straight line.
112.
Julia K Pruns Jens-Peter Vietzke Manfred Strassner Claudius Rapp Ulrich Hintze Wilfried A K?nig 《Rapid communications in mass spectrometry : RCM》2002,16(3):208-211
A new solvent-free sample preparation method using silver trifluoroacetate (AgTFA) was developed for the analysis of low molecular weight paraffins and microcrystalline waxes by laser desorption/ionization time-of-flight mass spectrometry (LDI-TOFMS). Experiments show that spectral quality can be enhanced by dispersing AgTFA directly in liquid paraffins without the use of additional solvents. This preparation mixture is applied directly to the MALDI probe. Solid waxes could be examined by melting prior to analysis. The method also provides sufficiently reproducible spectra that peak area ratios between mono- and bicyclic alkane peaks indicated variations in the cycloalkane content of paraffin samples. Dehydrogenation of hydrocarbons observed during the desorption/ionization process was studied by analysis of alkane standards. 相似文献
113.
S. Sabchevski T. Idehara I. Ogawa M. Glyavin K. Ohashi 《International Journal of Infrared and Millimeter Waves》2002,23(5):675-692
A computer code for simulation of beam-field interaction in a resonant cavity of a gyrotron has been developed. It is based on a self-consistent, time-independent, single-mode physical model. The code has been applied to the analysis of the electrodynamical system of a novel high-harmonic gyrotron with axis-encircling beam and a permanent magnet. In this paper both the physical model and numerical techniques used are outlined. Some results of the numerical experiments are presented and discussed. 相似文献
114.
K Kawasaki T Tsuji K Hirase M Miyano Y Imoto M Iwamoto 《Chemical & pharmaceutical bulletin》1991,39(3):584-589
N-Terminal tripeptide analogs of fibrin alpha-chain were synthesized and their inhibitory effect on fibrinogen/thrombin clotting was examined. A new water-soluble active ester, 3-pyridinium ester, was used for the synthesis. Among the synthetic peptides, H-Gly-Pro-Arg-hexamethyleneimine exhibited the highest inhibitory effect on fibrinogen-thrombin clotting. 相似文献
115.
In the present paper an analytical potential form is used for overlap repulsive energy, derived by Harrison from quantum mechanical considerations, along with the composite effect of three-body forces and intersublattice displacement. The short-range overlap parameters in Harrison's potential form have direct correlation with the valence state energies for outermost electrons. The potential model is applied to calculate the third and fourth order elastic constants, first and second pressure derivatives of second order elastic constants, Grüneisen parameter and its volume dependence, Anderson parameter, and thermal expansion coefficient for three non-centrosymmetric crystals, viz. CaF2, SrF2 and BaF2. The calculated values of various physical quantities are found to be in good agreement with experimental data.The authors are grateful to Dr. Mansour Khalef, the Head of Physics Department, TNRC, Tajura (Tripoli) for the facilities and encouragements. 相似文献
116.
K. A. Bronnikov 《Annalen der Physik》1991,503(8):527-534
A multidimensional generalization of the Reissner-Nordström solution of general relativity is obtained for the case of n Ricci-flat internal spaces. A two-parameter family of black-hole solutions for an arbitrary dimensionality D is selected. Nontrivial black holes with D > 4 are shown to exist only with a nonzero electric charge. Observational consequences are discussed, in particular, a violation of Coulomb's law. 相似文献
117.
118.
Yu. K. Voron'ko A. B. Kudryavtsev V. V. Osiko E. V. Sorokin 《Journal of Applied Spectroscopy》1991,55(4):953-957
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 4, pp. 535–540, October, 1991. 相似文献
119.
120.
Microwave-induced organic reaction enhancement (‘MORE’) chemistry technique (open vessel; controlled microwave energy to stay below the boiling point of the reaction mixture) was used for the N-formylation of aliphatic and aromatic amines and amino heterocycles with aq formic acid (80%) on a multiple gram scale in a few minutes. 相似文献