全文获取类型
收费全文 | 81916篇 |
免费 | 978篇 |
国内免费 | 754篇 |
专业分类
化学 | 27034篇 |
晶体学 | 834篇 |
力学 | 6932篇 |
综合类 | 23篇 |
数学 | 32402篇 |
物理学 | 16423篇 |
出版年
2023年 | 109篇 |
2022年 | 171篇 |
2021年 | 179篇 |
2020年 | 164篇 |
2019年 | 147篇 |
2018年 | 10529篇 |
2017年 | 10331篇 |
2016年 | 6233篇 |
2015年 | 1032篇 |
2014年 | 527篇 |
2013年 | 573篇 |
2012年 | 4088篇 |
2011年 | 10819篇 |
2010年 | 5832篇 |
2009年 | 6245篇 |
2008年 | 6830篇 |
2007年 | 8970篇 |
2006年 | 430篇 |
2005年 | 1479篇 |
2004年 | 1673篇 |
2003年 | 2104篇 |
2002年 | 1122篇 |
2001年 | 342篇 |
2000年 | 374篇 |
1999年 | 263篇 |
1998年 | 288篇 |
1997年 | 231篇 |
1996年 | 284篇 |
1995年 | 192篇 |
1994年 | 128篇 |
1993年 | 123篇 |
1992年 | 88篇 |
1991年 | 93篇 |
1990年 | 72篇 |
1989年 | 75篇 |
1988年 | 78篇 |
1987年 | 76篇 |
1986年 | 70篇 |
1985年 | 55篇 |
1984年 | 57篇 |
1983年 | 40篇 |
1982年 | 45篇 |
1981年 | 41篇 |
1980年 | 55篇 |
1979年 | 46篇 |
1914年 | 45篇 |
1913年 | 40篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
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
2.
Nonlinear Dynamics - In order to solve the constrained-input problem and reduce the computing resources, a novel event-triggered optimal control method is proposed for a class of discrete-time... 相似文献
3.
Mesoscopic modeling at the pore scale offers great promise in exploring the underlying structure transport performance of flow through porous media. The present work studies the fluid flow subjected to capillarity-induced resonance in porous media characterized by different porous structure and wettability. The effects of porosity and wettability on the displacement behavior of the fluid flow through porous media are discussed. The results are presented in the form of temporal evolution of percentage saturation and displacement of the fluid front through porous media. The present study reveals that the vibration in the form of acoustic excitation could be significant in the mobilization of fluid through the porous media. The dependence of displacement of the fluid on physicochemical parameters like wettability of the surface, frequency along with the porosity is analyzed. It was observed that the mean displacement of the fluid is more in the case of invading fluid with wetting phase where the driving force strength is not so dominant. 相似文献
4.
5.
6.
7.
8.
S. V. Panin I. V. Vlasov V. P. Sergeev B. B. Ovechkin P. O. Marushchak Sunder Ramasubbu P. S. Lyubutin V. V. Titkov 《Physical Mesomechanics》2015,18(3):261-272
The structure and properties of 12Cr1MoV steel irradiated with a zirconium ion beam were studied by optical microscopy, scanning electron microscopy, and micro- and nanoindentation. It is shown that the modification covers the entire cross-section of the irradiated specimens to a depth of 1 mm. The data on irradiation-induced structural changes are used to interpret the changes in mechanical properties of the irradiated specimens under static and cyclic loading. Particular attention is given to analysis of strain estimation by the digital image correlation method. 相似文献
9.
He Haidong Yang Haifeng Zhou Longpeng Chen Tianchi 《Journal of Russian Laser Research》2015,36(3):292-299
Ni–Co alloys have a wide range of applications in various fields owning to their excellent physical, chemical, and mechanical properties. In this paper, we prepare Ni–Co alloy coatings on 316L stain steel surfaces by electroplating. We present a novel approach utilizing a nanosecond laser to induce microtextures on Ni–Co alloy coatings. We study experimentally the effects of laser power and scanning rate on the surface morphologies of Ni–Co alloy coatings. The results indicate that the shape and size of induced microtextures can be controlled by the laser power and scanning rate. The size of grains increases with increase in the work current of the laser (WCL) at a certain scanning rate. With the WCL constant, the size of grains decreases with increase in scanning rate while their average height increases. It is a simple and easily-controlled method for the fabrication of microstructures on Ni–Co alloy coatings, which has promising applications in investigations of the properties of microtextured surfaces, such as friction, adhesion, and wetting. 相似文献
10.