全文获取类型
收费全文 | 1282316篇 |
免费 | 33518篇 |
国内免费 | 11948篇 |
专业分类
化学 | 636373篇 |
晶体学 | 19680篇 |
力学 | 74551篇 |
综合类 | 507篇 |
数学 | 239513篇 |
物理学 | 357158篇 |
出版年
2021年 | 14094篇 |
2020年 | 16755篇 |
2019年 | 17108篇 |
2016年 | 27958篇 |
2015年 | 21583篇 |
2014年 | 31548篇 |
2013年 | 75717篇 |
2012年 | 36067篇 |
2011年 | 30020篇 |
2010年 | 36204篇 |
2009年 | 39178篇 |
2008年 | 29935篇 |
2007年 | 24478篇 |
2006年 | 32872篇 |
2005年 | 24002篇 |
2004年 | 26409篇 |
2003年 | 25752篇 |
2002年 | 27530篇 |
2001年 | 25050篇 |
2000年 | 22823篇 |
1999年 | 21839篇 |
1998年 | 20877篇 |
1997年 | 20888篇 |
1996年 | 21133篇 |
1995年 | 19240篇 |
1994年 | 18599篇 |
1993年 | 18095篇 |
1992年 | 17586篇 |
1991年 | 17919篇 |
1990年 | 17140篇 |
1989年 | 17211篇 |
1988年 | 16728篇 |
1987年 | 16774篇 |
1986年 | 15657篇 |
1985年 | 22124篇 |
1984年 | 23494篇 |
1983年 | 19758篇 |
1982年 | 21501篇 |
1981年 | 20752篇 |
1980年 | 20082篇 |
1979年 | 20086篇 |
1978年 | 21506篇 |
1977年 | 21056篇 |
1976年 | 20714篇 |
1975年 | 19380篇 |
1974年 | 18742篇 |
1973年 | 19286篇 |
1972年 | 13816篇 |
1968年 | 11857篇 |
1967年 | 12250篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Zhengcheng Wang Shangyan Zhou Wei Liao Qian Zhou Meida Chen Jin Long Prof. Qingmei Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(66):e202201987
The designs of efficient and inexpensive Pt-based catalysts for methanol oxidation reaction (MOR) are essential to boost the commercialization of direct methanol fuel cells. Here, the highly catalytic performance PtFe alloys supported on multiwalled carbon nanotubes (MWCNTs) decorating nitrogen-doped carbon (NC) have been successfully prepared via co-engineering of the surface composition and electronic structure. The Pt1Fe3@NC/MWCNTs catalyst with moderate Fe3+ feeding content (0.86 mA/mgPt) exhibits 2.26-fold enhancement in MOR mass activity compared to pristine Pt/C catalyst (0.38 mA/mgPt). Furthermore, the CO oxidation initial potential of Pt1Fe3@NC/MWCNTs catalyst is lower relative to Pt/C catalyst (0.71 V and 0.80 V). Benefited from the optimal surface compositions, the anti-corrosion ability of MWCNT, strong electron interaction between PtFe alloys and MWCNTs and the N-doped carbon (NC) layer, the Pt1Fe3@NC/MWCNTs catalyst presents an improved MOR performance and anti-CO poisoning ability. This study would open up new perspective for designing efficient electrocatalysts for the DMFCs field. 相似文献
62.
Hua Saixiang Zhu Huichao Wang Xiao Wu Mingyuan Wu Qingyun Liu Jiuyi Yang Jianjun Zhang Jianan 《Cellulose (London, England)》2022,29(13):7465-7475
Cellulose - Ultraviolet (UV) protective cotton fabric is a convenient and reliable way to protect human body from sunlight. Herein, a polymerizable UV-absorber,... 相似文献
63.
Journal of Analytical Chemistry - The present study reports the development of a magnetic polyethylene glycol nanocomposite based on graphite reinforcement carbon paste electrode for the sensitive... 相似文献
64.
Varfolomeev S. D. Panin A. A. Semenova N. A. Ublinskiy M. V. Akhadov T. A. Bykov V. I. Tsybenova S. B. 《Russian Chemical Bulletin》2022,71(3):591-594
A kinetic study of the effect of thermoheliox (inhalation of a helium and oxygen mixture, 70 °C) on the functional hemodynamics of the human brain by functional magnetic resonance imaging was carried out. The dynamic responses of the BOLD signal were found to be biphasic. An empirical equation describing the first phase of the hemodynamic response to visual stimulus was proposed. It was shown that preliminary inhalation of thermoheliox stimulates the hemodynamic responses by slowing down the vasoconstriction.
相似文献65.
Russian Journal of Organic Chemistry - A highly efficient green protocol has been proposed for the synthesis of symmetrical S-aryl arenesulfonothioates by irradiation of N-hydroxy arenesulfonamides... 相似文献
66.
Numerical Algorithms - In this work, we propose a fractional extension of the one-dimensional nonlinear vibration problem on an elastic string. The fractional problem is governed by a hyperbolic... 相似文献
67.
为提高煤与瓦斯突出矿井瓦斯抽放效果,建立了3个一级指标、14个二级指标的突出矿井瓦斯抽放限制影响因素评价指标体系,利用AHP和熵权法分别确定指标因子主、客观权重.通过实地调研分析和反馈验证了AHP-熵权法的可行性和正确性,利用加权平均法确定评价模型的综合权重.研究表明:封孔方式、钻孔半径、抽放时间、煤体裂隙发育程度和抽放负压是目前影响煤矿瓦斯抽放效果的主控因素. 相似文献
68.
Siberian Mathematical Journal - Let $ \{(A_{i},B_{i})\}_{i=1}^{m} $ be a set pair system. Füredi, Gyárfás, and Király called it $ 1 $ -cross intersecting if $... 相似文献
69.
Theoretical and Mathematical Physics - Dynamic systems acting on the plane and possessing the Wada property have been observed. There exist only two topological types, symmetric and antisymmetric,... 相似文献
70.
Mathematical Notes - Subspaces of the space of analytic functions on a convex domain in the complex plane that are invariant with respect to the differentiation operator are studied. The problem of... 相似文献