全文获取类型
收费全文 | 90393篇 |
免费 | 16930篇 |
国内免费 | 9250篇 |
专业分类
化学 | 61774篇 |
晶体学 | 921篇 |
力学 | 5777篇 |
综合类 | 517篇 |
数学 | 10170篇 |
物理学 | 37414篇 |
出版年
2024年 | 349篇 |
2023年 | 2053篇 |
2022年 | 3305篇 |
2021年 | 3471篇 |
2020年 | 3954篇 |
2019年 | 3532篇 |
2018年 | 3237篇 |
2017年 | 2885篇 |
2016年 | 4610篇 |
2015年 | 4391篇 |
2014年 | 5359篇 |
2013年 | 6790篇 |
2012年 | 8250篇 |
2011年 | 8429篇 |
2010年 | 5574篇 |
2009年 | 5408篇 |
2008年 | 5803篇 |
2007年 | 5093篇 |
2006年 | 4780篇 |
2005年 | 3837篇 |
2004年 | 2958篇 |
2003年 | 2303篇 |
2002年 | 2112篇 |
2001年 | 1824篇 |
2000年 | 1612篇 |
1999年 | 1847篇 |
1998年 | 1598篇 |
1997年 | 1582篇 |
1996年 | 1568篇 |
1995年 | 1326篇 |
1994年 | 1153篇 |
1993年 | 1000篇 |
1992年 | 864篇 |
1991年 | 785篇 |
1990年 | 645篇 |
1989年 | 501篇 |
1988年 | 373篇 |
1987年 | 308篇 |
1986年 | 325篇 |
1985年 | 262篇 |
1984年 | 151篇 |
1983年 | 117篇 |
1982年 | 100篇 |
1981年 | 57篇 |
1980年 | 42篇 |
1979年 | 15篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1957年 | 31篇 |
1922年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Xin Yang Chuan Dong Jun Zhang Yan-sheng Wei Wei-Jun Jin Chang-song Liu 《Microchemical Journal》1997,57(3):294-304
Six polycyclic aromatic hydrocarbons (PAHs) are studied by chemical deoxygenation microemulsion-stabilized room temperature phosphorimetry with sodium sulfite as an oxygen scavenger and thallous nitrate as a heavy atom perturber in sodium dodecyl sulfate medium. Several factors influencing room temperature phosphorescence such as the concentration of sodium dodecyl sulfate, the heavy atom concentration, the pH, and the concentration of sodium sulfite are discussed and the quenching effect of NO2−on room temperature phosphorimetry of PAHs was compared in the microemulsion and micelle media. 相似文献
992.
993.
N-(α-Benzotriazolylalkyl)arylacetamides, readily available from an arylacetamide, an aldehyde and benzotriazole, undergo intramolecular cyclization under acidic conditions to give 1-aryl-1,4-dihydro-3(2H)-isoquinolinones in good to excellent yields. Similarly, 2-(benzotriazol-1-yl)-2-(o-hydroxyphenyl)ethanols, obtained by lithiation of 2-(benzotriazol-1-ylmethyl)phenols followed by quenching with aldehydes or ketones, eliminate a molecule of water and a molecule of benzotriazole yielding 2-substituted and 2,3-disubstituted benzofurans. 相似文献
994.
Theoretical and Mathematical Physics - The initial-boundary value problems for the matrix Lakshmanan–Porsezian–Daniel system are studied by utilizing the Fokas unified transform... 相似文献
995.
Acta Mathematicae Applicatae Sinica, English Series - Joint analysis of multiple phenotypes can have better interpretation of complex diseases and increase statistical power to detect more... 相似文献
996.
In this paper, we deal with the nonlinear second-order differential equation with damped vibration term involving p-Laplacian operator. Of particular interest is the resolution of an open problem. An interesting outcome from our result is that we can obtain the fast homoclinic solution with general superlinear growth assumption in suitable Sobolev space. To our knowledge, our theorems appear to be the first such result about damped vibration problem with p-Laplacian operator. 相似文献
997.
This paper is considering the problem of traveling wave solutions (TWS) for a susceptible-exposed-infectious-recovered (SEIR) epidemic model with discrete diffusion. The threshold condition for the existence and nonexistence of TWS is obtained. More specifically, such kind of solutions are governed by the threshold number ?0. We can find a critical wave speed c? if ?0 > 1, by employing the Schauder's fixed point theorem, limiting argument and two-sided Laplace transform, we confirm that there exists TWS for c > c?, while there exists no TWS for c < c?. We also obtain the nonexistence of TWS for ?0 ≤ 1. At last, we give some biological explanations from the epidemiological perspective. 相似文献
998.
In this paper, the authors use Glimm scheme to study the global existence of BV solutions to Cauchy problem of the pressure-gradient system with large initial data. To this end, some important properties of the shock curves of the pressure-gradient system in the Riemann invariant coordinate system and verify that the shock curves satisfy Diperna’s conditions (see [Diperna, R. J., Existence in the large for quasilinear hyperbolic conservation laws, Arch. Ration. Mech. Anal., 52(3), 1973, 244–257]) are studied. Then they construct the approximate solution sequence through Glimm scheme. By establishing accurate local interaction estimates, they prove the boundedness of the approximate solution sequence and its total variation. 相似文献
999.
本文研究带有五次项的非线性Schrödinger方程初边值问题的有限差分法,其中方程中二阶偏导数项的系数、五次项的系数及初值满足下面的条件(1.6).针对此问题,我们研究了一个守恒差分格式,在条件(1.6)下,差分解的$L^{\infty}$模先验估计被得到.在此基础上,我们得到了差分解最优$L^2$模的误差估计. 相似文献
1000.
Journal of Optimization Theory and Applications - This paper is to establish a sufficient maximum principle for one kind of stochastic optimal control problem with three types of delays: a discrete... 相似文献