全文获取类型
收费全文 | 58374篇 |
免费 | 9310篇 |
国内免费 | 6314篇 |
专业分类
化学 | 41835篇 |
晶体学 | 694篇 |
力学 | 3188篇 |
综合类 | 363篇 |
数学 | 6473篇 |
物理学 | 21445篇 |
出版年
2024年 | 203篇 |
2023年 | 1098篇 |
2022年 | 1944篇 |
2021年 | 2060篇 |
2020年 | 2241篇 |
2019年 | 2217篇 |
2018年 | 1906篇 |
2017年 | 1770篇 |
2016年 | 2663篇 |
2015年 | 2624篇 |
2014年 | 3256篇 |
2013年 | 4259篇 |
2012年 | 5028篇 |
2011年 | 5227篇 |
2010年 | 3539篇 |
2009年 | 3437篇 |
2008年 | 3842篇 |
2007年 | 3436篇 |
2006年 | 3137篇 |
2005年 | 2632篇 |
2004年 | 2061篇 |
2003年 | 1636篇 |
2002年 | 1607篇 |
2001年 | 1310篇 |
2000年 | 1075篇 |
1999年 | 1144篇 |
1998年 | 998篇 |
1997年 | 930篇 |
1996年 | 953篇 |
1995年 | 796篇 |
1994年 | 698篇 |
1993年 | 616篇 |
1992年 | 597篇 |
1991年 | 497篇 |
1990年 | 423篇 |
1989年 | 339篇 |
1988年 | 259篇 |
1987年 | 206篇 |
1986年 | 242篇 |
1985年 | 226篇 |
1984年 | 138篇 |
1983年 | 107篇 |
1982年 | 97篇 |
1981年 | 74篇 |
1980年 | 59篇 |
1979年 | 62篇 |
1978年 | 40篇 |
1976年 | 38篇 |
1974年 | 40篇 |
1973年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
21.
22.
23.
24.
Richiro Ushimaru Zhang Chen Houyuan Zhao Po-hsun Fan Prof. Dr. Hung-wen Liu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(9):3586-3590
Albomycin δ2 is a sulfur-containing sideromycin natural product that shows potent antibacterial activity against clinically important pathogens. The l -serine-thioheptose dipeptide partial structure, known as SB-217452, has been found to be the active seryl-tRNA synthetase inhibitor component of albomycin δ2. Herein, it is demonstrated that AbmF catalyzes condensation between the 6′-amino-4′-thionucleoside with the d -ribo configuration and seryl-adenylate supplied by the serine adenylation activity of AbmK. Formation of the dipeptide is followed by C3′-epimerization to produce SB-217452 with the d -xylo configuration, which is catalyzed by the radical S-adenosyl-l -methionine enzyme AbmJ. Gene deletion suggests that AbmC is involved in peptide assembly linking SB-217452 with the siderophore moiety. This study establishes how the albomycin biosynthetic machinery generates its antimicrobial component SB-217452. 相似文献
25.
Jie Lu Ju-Kang Wu Yao Jiang Dr. Peng Tan Lin Zhang Yu Lei Prof. Xiao-Qin Liu Prof. Lin-Bing Sun 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(16):6490-6496
Hierarchically porous metal–organic frameworks (HP-MOFs) are promising in various applications. Most reported HP-MOFs are prepared based on the generation of mesopores in microporous frameworks, and the formed mesopores are connected by microporous channels, limiting the accessibility of mesopores for bulky molecules. A hierarchical structure is formed by constructing microporous MOFs in uninterrupted mesoporous tunnels. Using the confined space in as-prepared mesoporous silica, highly dispersed metal precursors for MOFs are coated on the internal surface of mesoporous tunnels. Ligand vapor-induced crystallization is employed to enable quantitative formation of MOFs in situ, in which sublimated ligands diffuse into mesoporous tunnels and react with metal precursors. The obtained hierarchically porous composites exhibit record-high adsorption capacity for the bulky molecule trypsin. The thermal and storage stability of trypsin is improved upon immobilization on the composites. 相似文献
26.
27.
The biodegradability of phtalic acid esters in marine and freshwater environments was characterized by their binding free energy with corresponding degrading enzymes. According to comprehensive biodegradation effects weights, the binding free energy values were converted into dimensionless efficacy coefficient using ratio normalization method. Then, considering comprehensive dual biodegradation effects value and the structural parameters of PAEs in both marine and freshwater environments, a 3D-QSAR pharmacophore model was constructed, five PAE derivatives (DBP−COOH, DBP−CHO, DBP−OH, DINP−NH2, and DINP−NO2) were screened out based on their environmental friendliness, functionality and stability. The prediction of biodegradation effects on five PAE derivatives by biodegradation models in marine and freshwater environment increased by 15.90 %, 15.84 %, 27.21 %, 12.33 %, and 8.32 %, and 21.57 %, 15.21 %, 20.99 %, 15.10 %, and 9.74 %, respectively. By simulating the photodegradation path of the PAE derivative molecular, it was found that DBP−OH can generate .OH and provides free radicals for the photodegradation of microplastics in the environment. 相似文献
28.
29.
30.
Terahertz(THz) wave emission from argon atom in a two-color laser pulses is studied numerically by solving the one-dimensional(1D) time-dependent Schr ¨odinger equation. The THz spectra we obtained include both discontinuous and continuum ones. By using the special basis functions that we previously proposed, our analysis points out that the discontinuous and continuum parts are contributed by bound–bound and continuum–continuum transition of atomic energy levels. Although the atomic wave function is strongly dressed during the interaction with laser fields, our identification for the discontinuous part of the THz wave shows that the transition between highly excited bound states can still be well described by the field-free basis function in the tunneling ionization regime. 相似文献