全文获取类型
收费全文 | 211013篇 |
免费 | 3159篇 |
国内免费 | 1440篇 |
专业分类
化学 | 110864篇 |
晶体学 | 3484篇 |
力学 | 10677篇 |
综合类 | 98篇 |
数学 | 22671篇 |
物理学 | 67818篇 |
出版年
2021年 | 2302篇 |
2020年 | 2423篇 |
2019年 | 3025篇 |
2018年 | 4020篇 |
2017年 | 3994篇 |
2016年 | 5290篇 |
2015年 | 2809篇 |
2014年 | 4844篇 |
2013年 | 9255篇 |
2012年 | 7678篇 |
2011年 | 8855篇 |
2010年 | 7054篇 |
2009年 | 7137篇 |
2008年 | 8202篇 |
2007年 | 8127篇 |
2006年 | 7116篇 |
2005年 | 6250篇 |
2004年 | 5873篇 |
2003年 | 5384篇 |
2002年 | 5414篇 |
2001年 | 5851篇 |
2000年 | 4274篇 |
1999年 | 3311篇 |
1998年 | 2818篇 |
1997年 | 2837篇 |
1996年 | 2614篇 |
1995年 | 2263篇 |
1994年 | 2383篇 |
1993年 | 2280篇 |
1992年 | 2570篇 |
1991年 | 2691篇 |
1990年 | 2592篇 |
1989年 | 2655篇 |
1988年 | 2553篇 |
1987年 | 2567篇 |
1986年 | 2423篇 |
1985年 | 3040篇 |
1984年 | 3107篇 |
1983年 | 2604篇 |
1982年 | 2565篇 |
1981年 | 2529篇 |
1980年 | 2337篇 |
1979年 | 2709篇 |
1978年 | 2671篇 |
1977年 | 2870篇 |
1976年 | 2872篇 |
1975年 | 2664篇 |
1974年 | 2602篇 |
1973年 | 2711篇 |
1972年 | 2085篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Colloid Journal - The capillary-osmosis and reverse-osmosis coefficients of an ion-exchange membrane have been calculated as the kinetic coefficients of the Onsager matrix within the thermodynamics... 相似文献
22.
Wacker oxidation is an industry-adopted process to transform olefins into value-added epoxides and carbonyls. However, traditional Wacker oxidation involves the use of homogeneous palladium and copper catalysts for the olefin addition and reductive elimination. Here, we demonstrated an ultrahigh loading Cu single atom catalyst(14% Cu, mass fraction) for the palladium-free Wacker oxidation of 4-vinylanisole into the corresponding ketone with N-methylhydroxylamine hydrochloride as an additive under mild conditions. Mechanistic studies by 18O and deuterium isotope labelling revealed a hydrogen shift mechanism in this palladium-free process using N-methylhydroxylamine hydrochloride as the oxygen source. The reaction scope can be further extended to Kucherov oxidation. Our study paves the way to replace noble metal catalysts in the traditional homogeneous processes with single atom catalysts. 相似文献
23.
Meihua Shen Dr. Xinpeng Zhao Dr. Lu Han Nanxi Jin Prof. Song Liu Prof. Tao Jia Prof. Zhijun Chen Prof. Xiuhua Zhao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(20):e202104137
Solar-driven interfacial vaporization by localizing solar-thermal energy conversion to the air−water interface has attracted tremendous attention. In the process of converting solar energy into heat energy, photothermal materials play an essential role. Herein, a flexible solar-thermal material di-cyan substituted 5,12-dibutylquinacridone (DCN−4CQA)@Paper was developed by coating photothermal quinacridone derivatives on the cellulose paper. The DCN−4CQA@Paper combines desired chemical and physical properties, broadband light-absorbing, and shape-conforming abilities that render efficient photothermic vaporization. Notably, synergetic coupling of solar-steam and solar-electricity technologies by integrating DCN−4CQA@Paper and the thermoelectric devices is realized without trade-offs, highlighting the practical consideration toward more impactful solar heat exploitation. Such solar distillation and low-grade heat-to-electricity generation functions can provide potential opportunities for fresh water and electricity supply in off-grid or remote areas. 相似文献
24.
Doklady Mathematics - Two classes of Taylor-type formulas for arbitrary continuous functions on intervals are obtained using Bernstein polynomials. These formulas are applicable to both smooth... 相似文献
25.
McElroy Tucker S. Politis Dimitris N. 《Statistical Inference for Stochastic Processes》2022,25(3):471-483
Statistical Inference for Stochastic Processes - The problem of linear interpolation in the context of a multivariate time series having multiple (possibly non-consecutive) missing values is... 相似文献
26.
Ibotov Sh. Kh. Yuldasheva N. K. Mukarramov N. I. Zakirova R. P. Gusakova S. D. 《Chemistry of Natural Compounds》2022,58(4):728-731
Chemistry of Natural Compounds - 相似文献
27.
Svetlakova A. V. Mendez M. Sanchez Tuchin E. S. Khodan A. N. Traore M. Azouani R. Kanaev A. Tuchin V. V. 《Optics and Spectroscopy》2021,129(8):846-850
Optics and Spectroscopy - We study the photocatalytic activity of nanocomposites based on θ-phase alumina (Al2O3) with different TiO2 concentrations for heterogeneous photocatalysis and... 相似文献
28.
Kolesnikov A. O. Shatokhin A. N. Vishnyakov E. A. Ragozin E. N. 《Journal of Russian Laser Research》2022,43(4):467-475
Journal of Russian Laser Research - We analyze the way of advancing to tender X-rays the short-wavelength bound of the operating range of flat-field grating spectrographs. We design two VLS grating... 相似文献
29.
Russian Chemical Bulletin - The N-methylation of primary carboxamides is based on two consecutive reactions. The silylation of the corresponding carboxamides with chloro(chloromethyl)dimethylsilane... 相似文献
30.
Nonlinear Dynamics - In this paper, we analyze the effect which the choice of a friction model has on tippe top inversion in the case where the resulting action of all dissipative forces is... 相似文献