全文获取类型
收费全文 | 75816篇 |
免费 | 13449篇 |
国内免费 | 18119篇 |
专业分类
化学 | 56487篇 |
晶体学 | 1928篇 |
力学 | 5041篇 |
综合类 | 1770篇 |
数学 | 10904篇 |
物理学 | 31254篇 |
出版年
2024年 | 78篇 |
2023年 | 1000篇 |
2022年 | 1953篇 |
2021年 | 2276篇 |
2020年 | 2604篇 |
2019年 | 2722篇 |
2018年 | 2347篇 |
2017年 | 2872篇 |
2016年 | 3090篇 |
2015年 | 3622篇 |
2014年 | 4312篇 |
2013年 | 5768篇 |
2012年 | 6456篇 |
2011年 | 6946篇 |
2010年 | 5892篇 |
2009年 | 5792篇 |
2008年 | 6370篇 |
2007年 | 5960篇 |
2006年 | 5734篇 |
2005年 | 4834篇 |
2004年 | 3897篇 |
2003年 | 3043篇 |
2002年 | 3156篇 |
2001年 | 2983篇 |
2000年 | 2507篇 |
1999年 | 1781篇 |
1998年 | 1183篇 |
1997年 | 998篇 |
1996年 | 1026篇 |
1995年 | 880篇 |
1994年 | 827篇 |
1993年 | 689篇 |
1992年 | 600篇 |
1991年 | 493篇 |
1990年 | 401篇 |
1989年 | 387篇 |
1988年 | 278篇 |
1987年 | 247篇 |
1986年 | 243篇 |
1985年 | 178篇 |
1984年 | 153篇 |
1983年 | 133篇 |
1982年 | 94篇 |
1981年 | 90篇 |
1980年 | 66篇 |
1979年 | 57篇 |
1978年 | 45篇 |
1977年 | 35篇 |
1974年 | 32篇 |
1973年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 168 毫秒
21.
Feng Cheng Shuqi Wu Wenwei Zheng Shengqun Su Takumi Nakanishi Wenhuang Xu Pritam Sadhukhan Hibiki Sejima Shimon Ikenaga Kaoru Yamamoto Kaige Gao Shinji Kanegawa Prof. Osamu Sato 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(59):e202202161
The crystallization of a complex having electron transfer properties in a polar space group can induce the polarization switching of a crystal in a specific direction, which is attractive for the development of sensors, memory devices, and capacitors. Unfortunately, the probability of crystallization in a polar space group is usually low. Noticing that enantiopure compounds crystallize in Sohncke space groups, this paper reports a strategy for the molecular design of non-ferroelectric polarization switching crystals based on the use of intramolecular electron transfer and chirality. In addition, this paper describes the synthesis of a mononuclear valence tautomeric (VT) cobalt complex bearing an enantiopure ligand. The introduction of enantiomer enables the crystallization of the complex in the polar space group (P21). The polarization of the crystals along the b-axis direction is not canceled out and the VT transition is accompanied by a change in the macroscopic polarization of the polar crystal. Polarization switching via electron transfer is realized at around room temperature. 相似文献
22.
弛豫铁电单晶Pb(In1/2Nb1/2)O3-PbTiO3(PIN-PT)相较于常用的Pb(Mg1/3Nb2/3)O3-PbTiO3(PMN-PT)具有更高的居里温度,在高稳定性、高性能的传感器、换能器方面具有应用前景。本工作采用谐振法研究了[001]方向极化的0.66PIN-0.34PT铁电单晶的全矩阵机电性能参数。0.66PIN-0.34PT 单晶的三方-四方相变温度(TRT)约为160 ℃,居里温度(TC)约为260 ℃,室温压电系数d33、d31、d15分别为1 340 pC/N、-780 pC/N、321 pC/N,介电常数εT33、εS33、εT11、εS11分别为2 700、905、2 210、1 927,机电耦合系数 k33、k31、k15、kt分别为 87%、58%、38%、61%。其纵向压电常数(d33)和纵向机电耦合系数(k33)小于 PMN-PT 单晶,但是横向压电性能(d31)和剪切压电性能(d15)都略高于PMN-PT单晶。另外,研究了机电耦合性能随温度的变化趋势,发现0.66PIN-0.34PT单晶在150 ℃以下有较好的温度稳定性。 相似文献
23.
Dr. Hongying Tang Jian Gao Prof. Yidong Wang Prof. Nanwen Li Dr. Kang Geng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(70):e202202064
Great efforts have been conducted to develop high temperature proton exchange membrane fuel cell (HT-PEMFC) due to its features of enhanced electrocatalyst reactivity, simplified hydrothermal management system and high CO tolerance of catalysts, and remarkable progress has been achieved. However, the easy leaching of phosphoric acid (PA) from the membranes during operation limits its commercial scale-up in complicated environments. This concept here mainly focuses on the recent developments for mitigation of PA loss in PEMs. The probable mechanisms of PA loss are proposed. The approaches to improve PA retention for example via introduction of phosphonic acid by covalent bond, using ion-pairs interaction and siphoning effect, and blending with inorganic nanoparticles are described in detail. Among these strategies, the siphoning effect from the intrinsic microporous PEMs is the most efficient and enables the cell to operate flexibly within a broad temperature range. Therefore, this concept may provide new ideas for the scientists to retain PA, to improve the cell performance and expand the potential applications of PA doped PEMs at elevated humidity and wide temperature range. 相似文献
24.
Yang Gang Wang Yanhui Yang Xueying Pan Yuelong Liu Yu Cheng Jianfeng Jiang Qiao Tuo Xianguo 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(5):2135-2145
Journal of Radioanalytical and Nuclear Chemistry - The preparation of C30 concrete for a cavernous waste repository under construction in China and its Cs(I) adsorption performance were... 相似文献
25.
29.
In this paper,we first construct compact embeddedλ-hypersurfaces with the topology of torus which are calledλ-torus in Euclidean spaces?n^+1.Then,we give many compact immersedλ-hypersurfaces in Euclidean spaces?n^+1. 相似文献
30.
The purpose of this paper is to investigate the connections between the weak Galerkin (WG) methods with and without stabilizers. The choices of stabilizers directly affect the convergence rates of the corresponding WG methods in general. However, we observed that the convergence rates are independent of the choices of stabilizers for these WG elements with stabilizers being optional. In this paper, we will verify such phenomena theoretically as well as numerically.
相似文献