全文获取类型
收费全文 | 218511篇 |
免费 | 1651篇 |
国内免费 | 647篇 |
专业分类
化学 | 119777篇 |
晶体学 | 3352篇 |
力学 | 8444篇 |
综合类 | 6篇 |
数学 | 23841篇 |
物理学 | 65389篇 |
出版年
2021年 | 1895篇 |
2020年 | 2128篇 |
2019年 | 2299篇 |
2018年 | 3232篇 |
2017年 | 3137篇 |
2016年 | 4319篇 |
2015年 | 2430篇 |
2014年 | 3862篇 |
2013年 | 9371篇 |
2012年 | 6991篇 |
2011年 | 8548篇 |
2010年 | 6148篇 |
2009年 | 5980篇 |
2008年 | 8234篇 |
2007年 | 8325篇 |
2006年 | 7761篇 |
2005年 | 7088篇 |
2004年 | 6280篇 |
2003年 | 5747篇 |
2002年 | 5584篇 |
2001年 | 5987篇 |
2000年 | 4729篇 |
1999年 | 3504篇 |
1998年 | 3037篇 |
1997年 | 3072篇 |
1996年 | 2863篇 |
1995年 | 2352篇 |
1994年 | 2451篇 |
1993年 | 2487篇 |
1992年 | 2631篇 |
1991年 | 2695篇 |
1990年 | 2589篇 |
1989年 | 2562篇 |
1988年 | 2493篇 |
1987年 | 2458篇 |
1986年 | 2381篇 |
1985年 | 3085篇 |
1984年 | 3226篇 |
1983年 | 2591篇 |
1982年 | 2863篇 |
1981年 | 2740篇 |
1980年 | 2540篇 |
1979年 | 2744篇 |
1978年 | 2870篇 |
1977年 | 2885篇 |
1976年 | 2865篇 |
1975年 | 2723篇 |
1974年 | 2706篇 |
1973年 | 2848篇 |
1972年 | 1888篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
151.
Russian Journal of Organic Chemistry - Iodohydroxylation of 1-phenyltricyclo[4.1.0.02,7]heptane in aqueous THF at 20°C with N-iodosuccinimide proceeds at the central bicyclobutane bond C 1... 相似文献
152.
E. J. Martínez M. V. Gil J. G. Rosas R. Moreno R. Mateos A. Morán X. Gómez 《Journal of Thermal Analysis and Calorimetry》2017,127(2):1209-1219
The effect of microwave pre-treatment (MwP) on anaerobic digestion of sewage sludge was studied by means of thermal analysis and evolved gas analysis. The effect of the pre-treatment at low energy input (<1000 kJ L?1) on sludge solubilisation was studied with the aid of response surface methodology. The pre-treatment process was subsequently studied at energies of 488–2700 kJ L?1 to evaluate the improvement in biogas production under mesophilic conditions. Organic matter modifications were studied using a Setaram TGA92 analyser at atmospheric pressure coupled to an MSC200 quadrupole mass spectrometer from Balzers. Particle size analysis was carried out using a Laser Diffraction Particle Size Analyser LS 13 320 Beckmann Coulter for evaluating the effect of MwP on sludge particles. Results showed an increase in organic matter solubilisation with the increase in the energy applied. Modifications in the specific surface area of the organic matter due to the MwP resulted in increments in methane yields. However, an accumulation of complex compounds was observed in thermal profiles at the maximum energy input (2700 kJ L?1). Semi-continuous digestion experiments were evaluated using as substrate pre-treated sludge at the optimum energy value (975 kJ L?1). Results showed a significant increase in methane yield (43 %) when evaluating the process at hydraulic retention times (HRTs) of 25–10 days. 相似文献
153.
Grafov B. M. Dobrovolskii Yu. A. Klyuev A. L. Ukshe A. E. Davydov A. D. Astaf’ev E. A. 《Journal of Solid State Electrochemistry》2017,21(3):915-918
Journal of Solid State Electrochemistry - An algorithm for analyzing electrochemical noise based on Chebyshev spectroscopy using the sample median is presented. Chebyshev spectroscopy with the... 相似文献
154.
Cholant C. M. Westphal T. M. Balboni R. D. C. Moura E. A. Gündel A. Flores W. H. Pawlicka A. Avellaneda C. O 《Journal of Solid State Electrochemistry》2017,21(5):1509-1515
Journal of Solid State Electrochemistry - Pure and doped vanadium pentoxide (V2O5, V2O5/MoO3) thin films were prepared by sol-gel method and dip coating technique. Furthermore, they were... 相似文献
155.
V. O. Startsev M. V. Molokov A. N. Blaznov M. E. Zhurkovskii V. T. Erofeev I. V. Smirnov 《Polymer Science Series D》2017,10(4):313-317
Russian and foreign standards for the techniques for the determination of the heat resistance of polymer materials are analyzed and the incorrectness of their use for polymer construction materials is shown. The determination of the heat resistance by the low-frequency dynamic mechanical method based on the temperature derivative extrema of the dynamic modulus of elasticity and the dynamic loss modulus under the transition of polymer matrices from the glassy to the highly elastic state is experimentally substantiated for multicomponent polymer compositions with dispersed or fibrous fillers. 相似文献
156.
We establish estimates of Wiman–Valiron type for solutions of evolution equations with a pseudodifferential operator of the Hörmander class in a Hilbert space. Estimates of this type characterize the behavior of the solution of the problem as t→∞ or t → 0 depending on the decay or growth rate of the Fourier coefficients of the initial data. 相似文献
157.
The Schrödinger operator with complex decaying potential on a lattice is considered. Trace formulas are derived on the basis of classical results of complex analysis. These formulas are applied to obtain global estimates of all zeros of the Fredholm determinant in terms of the potential. 相似文献
158.
Mathematical Notes - The solution of the Cauchy problem for the Gorini–Kossakowski–Sudarshan–Lindblad equation describing the irreversible quantum evolution of an n-particle... 相似文献
159.
We establish criteria for the validity of modular inequalities for the Hardy operator on the cone Ω of nonnegative decreasing functions from weighted Orlicz spaces with general weight. The result is based on the theorem on the reduction of modular inequalities for positively homogeneous operators on the cone Ω, which enables passing to modular inequalities for modified operators on the cone of all nonnegative functions from an Orlicz space. It is shown that, for the Hardy operator, the modified operator is a generalized Hardy operator. This enables us to establish explicit criteria for the validity of modular inequalities. 相似文献
160.