全文获取类型
收费全文 | 129511篇 |
免费 | 10931篇 |
国内免费 | 8200篇 |
专业分类
化学 | 77213篇 |
晶体学 | 1630篇 |
力学 | 7665篇 |
综合类 | 611篇 |
数学 | 15849篇 |
物理学 | 45674篇 |
出版年
2023年 | 1328篇 |
2022年 | 2793篇 |
2021年 | 3122篇 |
2020年 | 3450篇 |
2019年 | 3638篇 |
2018年 | 3933篇 |
2017年 | 3818篇 |
2016年 | 4952篇 |
2015年 | 3875篇 |
2014年 | 5160篇 |
2013年 | 7228篇 |
2012年 | 7742篇 |
2011年 | 8058篇 |
2010年 | 6119篇 |
2009年 | 6079篇 |
2008年 | 6445篇 |
2007年 | 5896篇 |
2006年 | 5410篇 |
2005年 | 4745篇 |
2004年 | 4129篇 |
2003年 | 3623篇 |
2002年 | 3720篇 |
2001年 | 3239篇 |
2000年 | 2644篇 |
1999年 | 2362篇 |
1998年 | 2130篇 |
1997年 | 1912篇 |
1996年 | 1824篇 |
1995年 | 1577篇 |
1994年 | 1576篇 |
1993年 | 1442篇 |
1992年 | 1357篇 |
1991年 | 1388篇 |
1990年 | 1365篇 |
1989年 | 1238篇 |
1988年 | 1072篇 |
1987年 | 1037篇 |
1986年 | 981篇 |
1985年 | 1033篇 |
1984年 | 982篇 |
1983年 | 880篇 |
1982年 | 857篇 |
1979年 | 809篇 |
1978年 | 813篇 |
1977年 | 808篇 |
1976年 | 920篇 |
1975年 | 814篇 |
1974年 | 846篇 |
1973年 | 847篇 |
1972年 | 752篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Knyazev Yu. V. Kazak N. V. Gavrichkov V. A. Polukeev S. I. Ovchinnikov S. G. 《JETP Letters》2022,116(8):567-573
JETP Letters - Changes in the magnetic properties of FeBO3 single crystals in the course of spin crossover occurring with increasing pressure up to 63 GPa are studied both experimentally and... 相似文献
12.
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
13.
Hao Lu Xiaodong Wang Hang Wang Andong Zhang Xinming Zheng Na Yu Zheng Tang Xinjun Xu Yahui Liu Ya-Nan Chen Zhishan Bo 《中国科学:化学(英文版)》2022,65(3):594-601
Three nonfused ring electron acceptors (NFREAs) TTC6,TT-C8T and TT-TC8 were purposefully designed and synthesized.The molecular geometry can be adjusted by the steric hindrance of lateral substituents.According to the DFT calculations,from TTC6 to TT-C8T and TT-TC8,planarity of the molecular backbone is gradually improved,accompanying with the enhancing of intramolecular charge transfer effect.As for TT-TC8,the two phenyl substituents are almost perpendicular to the molecular backbone,which endues the acceptor with good solubility and suppresses it to form over-aggregation.Multidirectional regular molecular orientation and closer molecular stacking are formed in TT-TC8 film.As a result,TT-TC8 based devices afford the highest PCE of 13.13%,which is much higher than that of TTC6 (4.41%) and TT-C8T (10.42%) and among the highest PCE values based on NFREAs. 相似文献
14.
Wang Rong Li Xu Zhou Youshi Cao Shuxuan Xu Honghao Han Wenjuan Zhang Yuxia Liu Junhai 《Journal of Russian Laser Research》2022,43(4):476-481
Journal of Russian Laser Research - We demonstrate a passively-mode-locked Pr3+: LuLiF4 laser operated at the 604 nm orange wave-length, using monolayer graphene as a saturable absorber. The... 相似文献
15.
Theoretical and Mathematical Physics - We consider three one-dimensional superconducting structures: 1) the one with $$p$$ -wave superconductivity; 2) the main experimental model of a nanowire with... 相似文献
16.
Designs, Codes and Cryptography - Large sets of combinatorial designs has always been a fascinating topic in design theory. These designs form a partition of the whole space into combinatorial... 相似文献
17.
In this paper, we study vanishing and splitting results on a complete smooth metric measure space \((M^n,g,\mathrm {e}^{-f}\mathrm {d}v)\) with various negative m-Bakry-Émery Ricci curvature lower bounds in terms of the first eigenvalue \(\lambda _1(\Delta _f)\) of the weighted Laplacian \(\Delta _f\), i.e., \(\mathrm {Ric}_{m,n}\ge -a\lambda _1(\Delta _f)-b\) for \(0<a\le \dfrac{m}{m-1}, b\ge 0\). In particular, we consider three main cases for different a and b with or without conditions on \(\lambda _1(\Delta _f)\). These results are extensions of Dung and Vieira, and weighted generalizations of Li-Wang, Dung-Sung, and Vieira.
相似文献18.
Siberian Mathematical Journal - We give a simple proof of one assertion used in solving Waring’s problem. 相似文献
19.
20.
Journal of Fourier Analysis and Applications - We develop a theory of Sobolev orthogonal polynomials on the Sierpiński gasket ( $$SG$$ ), which is a fractal set that can be viewed as a limit... 相似文献