全文获取类型
收费全文 | 81482篇 |
免费 | 485篇 |
国内免费 | 401篇 |
专业分类
化学 | 26545篇 |
晶体学 | 820篇 |
力学 | 6863篇 |
数学 | 32287篇 |
物理学 | 15853篇 |
出版年
2022年 | 144篇 |
2021年 | 202篇 |
2020年 | 146篇 |
2019年 | 136篇 |
2018年 | 10541篇 |
2017年 | 10340篇 |
2016年 | 6196篇 |
2015年 | 986篇 |
2014年 | 440篇 |
2013年 | 608篇 |
2012年 | 3993篇 |
2011年 | 10700篇 |
2010年 | 5752篇 |
2009年 | 6159篇 |
2008年 | 6709篇 |
2007年 | 8885篇 |
2006年 | 325篇 |
2005年 | 1415篇 |
2004年 | 1592篇 |
2003年 | 2031篇 |
2002年 | 1066篇 |
2001年 | 310篇 |
2000年 | 336篇 |
1999年 | 207篇 |
1998年 | 215篇 |
1997年 | 170篇 |
1996年 | 237篇 |
1995年 | 155篇 |
1994年 | 101篇 |
1993年 | 123篇 |
1992年 | 85篇 |
1991年 | 102篇 |
1990年 | 68篇 |
1989年 | 78篇 |
1988年 | 85篇 |
1987年 | 83篇 |
1986年 | 83篇 |
1985年 | 85篇 |
1984年 | 65篇 |
1983年 | 59篇 |
1982年 | 63篇 |
1981年 | 49篇 |
1980年 | 74篇 |
1979年 | 65篇 |
1978年 | 61篇 |
1977年 | 45篇 |
1914年 | 45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
11.
12.
13.
14.
Zenon Moszner 《Aequationes Mathematicae》2018,92(4):617-625
We give the form of the output function in Ginsburg’s machine in which the input and output dictionaries are abelian groups and the transition function is of a special form. 相似文献
15.
16.
17.
18.
19.
Muhammad Usman Khan Muhammad Yasir Mehboob Riaz Hussain Zainab Afzal Muhammad Khalid Muhammad Adnan 《International journal of quantum chemistry》2020,120(22):e26377
The development of organic electron acceptor materials is one of the key factors for realizing high-performance organic solar cells (OSCs). Nonfullerene electron acceptors, compared to traditional fullerene acceptor materials, have gained much impetus owing to their better optoelectronic tunabilities and lower cost, as well as higher stability. Therefore, 5 three-dimensional (3D) cross-shaped acceptor materials having a spirobifullerene core flanked with 2,1,3-benzothiadiazole are designed from a recently synthesized highly efficient acceptor molecule SF(BR) 4 and are investigated in detail with regard to their use as acceptor molecules in OSCs. The density functional theory (DFT) and time-dependent DFT (TDDFT) calculations have been performed for the estimation of frontier molecular orbital (FMO) analysis, density of states analysis, reorganization energies of electron and hole, dipole moment, open-circuit voltage, photo-physical characteristics, and transition density matrix analysis. In addition, the structure-property relationship is studied, and the influence of end-capped acceptor modifications on photovoltaic, photo-physical, and electronic properties of newly selected molecules ( H1-H5 ) is calculated and compared with reference ( R ) acceptor molecule SF(BR) 4 . The structural tailoring at terminals was found to effectively tune the FMO band gap, energy levels, absorption spectra, open-circuit voltage, reorganization energy, and binding energy value in selected molecules H1 to H5 . The 3D cross-shaped molecules H1 to H5 suppress the intermolecular aggregation in PTB7-Th blend, which leads to high efficiency of acceptor material H1 to H5 in OSCs. Consequently, better optoelectronic properties are achieved from designed molecules H1 to H5 . It is proposed that the conceptualized molecules are superior than highly efficient spirobifullerene core-based SF(BR) 4 acceptor molecules and, thus, are recommended to experiments for future developments of highly efficient solar cells. 相似文献
20.