全文获取类型
收费全文 | 68037篇 |
免费 | 14992篇 |
国内免费 | 5784篇 |
专业分类
化学 | 63286篇 |
晶体学 | 699篇 |
力学 | 2769篇 |
综合类 | 339篇 |
数学 | 6408篇 |
物理学 | 15312篇 |
出版年
2024年 | 68篇 |
2023年 | 655篇 |
2022年 | 850篇 |
2021年 | 1262篇 |
2020年 | 2441篇 |
2019年 | 3707篇 |
2018年 | 2115篇 |
2017年 | 1792篇 |
2016年 | 4852篇 |
2015年 | 4973篇 |
2014年 | 5205篇 |
2013年 | 6476篇 |
2012年 | 5960篇 |
2011年 | 5281篇 |
2010年 | 4924篇 |
2009年 | 4892篇 |
2008年 | 4597篇 |
2007年 | 3703篇 |
2006年 | 3264篇 |
2005年 | 3178篇 |
2004年 | 2662篇 |
2003年 | 2268篇 |
2002年 | 2970篇 |
2001年 | 2175篇 |
2000年 | 2023篇 |
1999年 | 1167篇 |
1998年 | 724篇 |
1997年 | 678篇 |
1996年 | 596篇 |
1995年 | 535篇 |
1994年 | 475篇 |
1993年 | 405篇 |
1992年 | 334篇 |
1991年 | 303篇 |
1990年 | 285篇 |
1989年 | 213篇 |
1988年 | 178篇 |
1987年 | 141篇 |
1986年 | 112篇 |
1985年 | 111篇 |
1984年 | 69篇 |
1983年 | 59篇 |
1982年 | 56篇 |
1981年 | 27篇 |
1980年 | 15篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1957年 | 8篇 |
1936年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
1.
2.
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
3.
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
4.
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
5.
Zeng Qing-Wei Wen Zhuo-Yu Fu Jun-Feng Zhou Nan-Run 《International Journal of Theoretical Physics》2021,60(9):3306-3333
International Journal of Theoretical Physics - A new quantum watermark algorithm is presented by combining maximum pixel difference partitioning with the least significant bit substitution... 相似文献
6.
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
7.
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8.
Li Quanxin Li Zheng He Cheng Sun Huilin Tan Shengheng Zhang Hua 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(5):2105-2115
Journal of Radioanalytical and Nuclear Chemistry - The simplified 8-oxide system (SiO2-B2O3-Na2O-Al2O3-CaO-TiO2-MoO3-La2O3) has been prepared under two types of cooling methods, and analyzed with... 相似文献
9.
Hu Duo-Duo Gao Qian Dai Jing-Cheng Cui Ru Li Yuan-Bo Li Yuan-Ming Zhou Xiao-Guo Bian Kang-Jie Wu Bing-Bing Zhang Kai-Fan Wang Xi-Sheng Li Yan 《中国科学:化学(英文版)》2022,65(4):753-761
Science China Chemistry - A light-induced, nickel-catalyzed three-component arylsulfonation of 1,3-enynes in the absence of photocatalyst is reported. This methodology exhibited mild conditions,... 相似文献
10.
In this article,we study the initial boundary value problem of coupled semi-linear degenerate parabolic equations with a singular potential term on manifolds with corner singularities.Firstly,we introduce the corner type weighted p-Sobolev spaces and the weighted corner type Sobolev inequality,the Poincare′inequality,and the Hardy inequality.Then,by using the potential well method and the inequality mentioned above,we obtain an existence theorem of global solutions with exponential decay and show the blow-up in finite time of solutions for both cases with low initial energy and critical initial energy.Significantly,the relation between the above two phenomena is derived as a sharp condition.Moreover,we show that the global existence also holds for the case of a potential well family. 相似文献