全文获取类型
收费全文 | 33849篇 |
免费 | 4621篇 |
国内免费 | 3705篇 |
专业分类
化学 | 12445篇 |
晶体学 | 79篇 |
力学 | 2705篇 |
综合类 | 286篇 |
数学 | 19246篇 |
物理学 | 7414篇 |
出版年
2024年 | 73篇 |
2023年 | 428篇 |
2022年 | 497篇 |
2021年 | 769篇 |
2020年 | 1197篇 |
2019年 | 1226篇 |
2018年 | 1038篇 |
2017年 | 1113篇 |
2016年 | 1472篇 |
2015年 | 1361篇 |
2014年 | 1872篇 |
2013年 | 3554篇 |
2012年 | 1929篇 |
2011年 | 2261篇 |
2010年 | 1907篇 |
2009年 | 2399篇 |
2008年 | 2325篇 |
2007年 | 2383篇 |
2006年 | 2131篇 |
2005年 | 1682篇 |
2004年 | 1469篇 |
2003年 | 1392篇 |
2002年 | 1143篇 |
2001年 | 894篇 |
2000年 | 851篇 |
1999年 | 728篇 |
1998年 | 604篇 |
1997年 | 588篇 |
1996年 | 398篇 |
1995年 | 323篇 |
1994年 | 296篇 |
1993年 | 210篇 |
1992年 | 204篇 |
1991年 | 145篇 |
1990年 | 134篇 |
1989年 | 103篇 |
1988年 | 87篇 |
1987年 | 73篇 |
1986年 | 67篇 |
1985年 | 102篇 |
1984年 | 128篇 |
1983年 | 61篇 |
1982年 | 94篇 |
1981年 | 90篇 |
1980年 | 86篇 |
1979年 | 72篇 |
1978年 | 69篇 |
1977年 | 45篇 |
1976年 | 43篇 |
1975年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
Nasrollah Hamidi 《Journal of Macromolecular Science: Physics》2019,58(2):219-247
The thermal decomposition of post-consumer samples of a carbonated water bottle made of poly(ethylene terephthalate), PC-PET, was examined by linear temperature programing under an argon atmosphere to determine its mass loss kinetics. A simple kinetic model, called the first order pseudo single-component model, was used. The total weight-loss of each sample assumed to be in two periods, with each period corresponding to a one step decomposition of the PC-PET to volatiles. Three methods for determining the kinetic parameters by thermal gravimetric analysis were examined: differential analysis at a constant heating rate (differential), temperatures of a given conversion at a number of heating rates (isoconversional), and the maximum rate at multiple heating rates (peak temperature). The latter two multiple heating rates methods results were comparable to each other but they were not in agreement with the results from the differential method. The results of the differential method were insensitive to the heating rate and consistent with kinetics data reported in the literature for PET. 相似文献
22.
High pressure can effectively control the phase transition of MoTe2 in experiment, but the mechanism is still unclear. In this work, we show by first-principles calculations that the phase transition is suppressed and phase becomes more stable under high pressure, which originates from the pressure-induced change of the interlayer band occupancies near the Fermi energy. Specifically, the interlayer states of phase tend to be fully occupied under high pressure, while they keep partially occupied for the phase. The increase of the band occupancies makes the phase more favorable in energy and prevents the structure changing from to phase. Moreover, we also analyze the superconductivity under high pressure based on BCS theory by calculating the density of states and phonon spectra. Our results may shed some light on understanding the relationship between the interlayer band occupancy and crystal stability of MoTe2 under high pressures. 相似文献
23.
The first-principles DFT calculations together with microkinetic analysis reveal the complex catalytic mechanism of low-content NO oxidation on CrO2(110) at room temperature. It quantitatively makes clear that CrO2(110) can exhibit considerable activity with the Mars-van-Krevelen mechanism preferred, and the nitrate species serves as the key poisoning species. 相似文献
24.
Jamil Chaker 《Mathematische Nachrichten》2019,292(11):2316-2337
We consider systems of stochastic differential equations of the form for with continuous, bounded and non‐degenerate coefficients. Here are independent one‐dimensional stable processes with . In this article we research on uniqueness of weak solutions to such systems by studying the corresponding martingale problem. We prove the uniqueness of weak solutions in the case of diagonal coefficient matrices. 相似文献
25.
Awatif Alqahtani Mohamed Jleli Bessem Samet 《Mathematical Methods in the Applied Sciences》2019,42(3):861-870
In this paper, some nonlocal in time differential inequalities of Sobolev type are considered. Using the nonlinear capacity method, sufficient conditions for the nonexistence of nontrivial global classical solutions are provided. 相似文献
26.
Claudianor O. Alves Daniel C. de Morais Filho Giovany M. Figueiredo 《Mathematical Methods in the Applied Sciences》2019,42(14):4862-4875
In this work, we prove the existence of positive solution for the following class of problems where λ>0 and is a potential satisfying some conditions. Using the variational method developed by Szulkin for functionals, which are the sum of a C1 functional with a convex lower semicontinuous functional, we prove that for each large enough λ>0, there exists a positive solution for the problem, and that, as λ→+∞, such solutions converge to a positive solution of the limit problem defined on the domain Ω=int(V?1({0})). 相似文献
27.
28.
29.
30.