全文获取类型
收费全文 | 328045篇 |
免费 | 12384篇 |
国内免费 | 7532篇 |
专业分类
化学 | 167456篇 |
晶体学 | 4417篇 |
力学 | 19206篇 |
综合类 | 525篇 |
数学 | 56386篇 |
物理学 | 99971篇 |
出版年
2022年 | 2909篇 |
2021年 | 3604篇 |
2020年 | 4005篇 |
2019年 | 3953篇 |
2018年 | 13869篇 |
2017年 | 13459篇 |
2016年 | 11684篇 |
2015年 | 5735篇 |
2014年 | 6852篇 |
2013年 | 12923篇 |
2012年 | 15665篇 |
2011年 | 23771篇 |
2010年 | 14912篇 |
2009年 | 15265篇 |
2008年 | 17863篇 |
2007年 | 19219篇 |
2006年 | 10701篇 |
2005年 | 10584篇 |
2004年 | 9576篇 |
2003年 | 8978篇 |
2002年 | 7691篇 |
2001年 | 9202篇 |
2000年 | 7051篇 |
1999年 | 5818篇 |
1998年 | 4417篇 |
1997年 | 4275篇 |
1996年 | 4103篇 |
1995年 | 3678篇 |
1994年 | 3496篇 |
1993年 | 3141篇 |
1992年 | 3667篇 |
1991年 | 3657篇 |
1990年 | 3293篇 |
1989年 | 3123篇 |
1988年 | 2922篇 |
1987年 | 2975篇 |
1986年 | 2660篇 |
1985年 | 3303篇 |
1984年 | 3210篇 |
1983年 | 2527篇 |
1982年 | 2511篇 |
1981年 | 2315篇 |
1980年 | 2242篇 |
1979年 | 2567篇 |
1978年 | 2699篇 |
1977年 | 2617篇 |
1976年 | 2479篇 |
1975年 | 2295篇 |
1974年 | 2305篇 |
1973年 | 2305篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
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
22.
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23.
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
24.
25.
根据教育部颁布的《普通高中物理课程标准(2017年版)》,在上海市物理教育教学基地(上海高校“立德树人”人文社会科学重点研究基地)的大力支持下,由上海市教育委员会组织编写的上海高中物理非统编教材进行了正式使用前的试教试用活动,此教材是在上海高中物理“二期课改”教材的基础上全面改写而成的.单元教学设计已成为当前教学设计的焦点问题,以《物理·必修》(第三册)静电场单元为例,详细阐述了“教学问题链”的设计理念,希望与广大一线教师交流试教试用的心得与反思,推动新课改课堂转型. 相似文献
26.
Numerical Algorithms - This paper considers different versions of block-column iterative (BCI) methods for solving nonnegative constrained linear least squares problems. We present the convergence... 相似文献
27.
Zhang Ya-Li Han Rong-Sheng Chen Liang 《International Journal of Theoretical Physics》2021,60(4):1384-1398
International Journal of Theoretical Physics - In this work, we give an analytical derivation of the reduced density matrix between two qubits in a cavity field, which is described by the quantum... 相似文献
28.
Karandashev S. A. Lukhmyrina T. S. Matveev B. A. Remennyi M. A. Usikova A. A. 《Optics and Spectroscopy》2021,129(11):1231-1235
Optics and Spectroscopy - The current–voltage characteristics and photocurrent of “monolithic” diode optical pairs optically coupled by a substrate made of InAs common for them... 相似文献
29.
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
30.
Kobayashi M. Zhang Y. Ishikawa H. Sun J. Oddershede J. Juul Jensen D. Miura H. 《Experimental Mechanics》2021,61(5):817-828
Experimental Mechanics - The internal strain distribution developing during plastic deformation is important for understanding the mechanical properties of polycrystalline materials. Such... 相似文献