全文获取类型
收费全文 | 1837篇 |
免费 | 179篇 |
国内免费 | 153篇 |
专业分类
化学 | 1418篇 |
晶体学 | 18篇 |
力学 | 92篇 |
综合类 | 12篇 |
数学 | 174篇 |
物理学 | 455篇 |
出版年
2023年 | 13篇 |
2022年 | 44篇 |
2021年 | 54篇 |
2020年 | 49篇 |
2019年 | 62篇 |
2018年 | 56篇 |
2017年 | 46篇 |
2016年 | 68篇 |
2015年 | 78篇 |
2014年 | 82篇 |
2013年 | 136篇 |
2012年 | 143篇 |
2011年 | 171篇 |
2010年 | 87篇 |
2009年 | 102篇 |
2008年 | 110篇 |
2007年 | 86篇 |
2006年 | 93篇 |
2005年 | 86篇 |
2004年 | 80篇 |
2003年 | 60篇 |
2002年 | 103篇 |
2001年 | 74篇 |
2000年 | 48篇 |
1999年 | 49篇 |
1998年 | 22篇 |
1997年 | 15篇 |
1996年 | 19篇 |
1995年 | 10篇 |
1994年 | 17篇 |
1993年 | 11篇 |
1992年 | 7篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1989年 | 2篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1976年 | 2篇 |
1975年 | 5篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1971年 | 2篇 |
排序方式: 共有2169条查询结果,搜索用时 15 毫秒
941.
可见光驱动光环化的荧光turn-on型二芳基乙烯分子开关是超分辨显微成像的理想材料, 但目前关于该类型分子的报道仍较少. 本工作合成了一种基于苯并[b]萘并[1,2-d]噻吩(BNTP)的405 nm可见光驱动光环化的荧光turn-on型二芳基乙烯分子BNTP-BTTO4, 同时系统研究了该分子的光物理性能与稳定性, 并借助密度泛函理论(DFT)计算厘清了分子实现可见光驱动光环化及荧光turn-on原因. 另外, 本研究发现BNTP引入后分子表现出比参比分子Ph-BTTO4更优异的抗疲劳性、热稳定性和光稳定性, 尤其是在历经200 min 405 nm可见光照射后, BNTP-BTTO4(c)吸收强度只下降4%, 光稳定性大幅提升. 本研究为设计开发性能优异的可见光驱动光环化的荧光turn-on型二芳基乙烯提供了新的思路. 相似文献
942.
943.
Song LQ Feng J Wang XS Yu JH Hou YJ Xie PH Zhang BW Xiang JF Ai XC Zhang JP 《Inorganic chemistry》2003,42(11):3393-3395
The unique behavior of a new Ru(II) diimine complex, Ru(bpy)(2)(L)(2+) (where L is 4-methyl-4'-[p-(dimethyl- amino)-alpha-styryl]-2,2'-bipyridine, bpy is 2,2'-bipyridine), was studied in detail. Due to the strong electron donating property of the amino group, an ILCT (intraligand charge transfer) state is involved either in the absorption spectra or in the time-resolved emission spectra. Dual emission based on (3)MLCT and (3)ILCT states was observed at room temperature for the first time via a time-resolved technique in Ru(II) diimine complexes. 相似文献
944.
具有β-(1→6)-半乳吡喃糖骨架和α-L-(1→3)-阿拉伯呋喃糖侧链的阿拉伯半乳寡糖的简易合成 总被引:1,自引:0,他引:1
4-Methoxyphenyl glycoside of β-D-Galp-(1→6)-[α-L-Araf-(1→3)-]β-D-Galp-(1→6)-β-D-Galp-(1→6)-{β-D-Galp-(1→6)-[α-L-Araf-(1→3)-]β-D-Galp-(1→6)-β-D-Galp-(1→6)-}2β-D-Galp-(1→6)-[α-L-Araf-(1→)3)-]β-D-Galp-(1→)6)-β-D-Galp was synthesized with 2,3,4,6-tetra-O-benzoyl-α-D-galactopyranosyl trichloroacetimidate (1), 6-O-acetyl-2,3,4-tri-O-benzoyl-α-D-galactopyranosyl trichloroacetimidate (11), 4-methoxyphenyl 3-O-allyl-2,4-tri-O-benzoyl-β-D-galactopyranoside (2),isopropyl 3-O-allyl-2,4-tri-O-benzoyl--thio-β-D-galactopyranoside (12),4-methoxyphenyl 2,3,4-tri-O-benzoyl-β-D-galactopyranoside (5), and 2,3,5-tri-O-benzoyl-α-L-arabinofuranosyl trichloroacetimidate (8) as the key synthons. 相似文献
945.
The adsorption of methylamine on highly siliceous MFI, FAU and FER-type zeolites was investigated withXRD, FT-IR, Raman, ^13C and ^29Si MAS NMR, and compared with the adsorption of methanol. As the adsorption of the amine, the relative intensity of XRD peaks of the zeolites has been changed significantly, the high-resolution ^29Si MAS NMR peaks have been broadened and shifted to low field, and the resonance of Si-OH groups has appeared. The vibration of N-H has been shifted to low frequency and C-N vibration moved to high frequency in the IR spectra, and the ^13C resonance peak broadened and shifted to high field for the adsorbed amine. The facts reveal an associating interaction between the perfect framework of the zeolites and the adsorbed methylamine with hydrogen bonds, leading to the formation of Si-OH groups and the high desorption temperature of the methylamine from the zeolites. 相似文献
946.
Molecular Simulations of Human and Mouse Aβ1–16 at Different pH Values: Structural Characteristics toward Understanding Cu2+‐Coordinated Amyloid Beta Spheres 下载免费PDF全文
As the main sequence responsible for metal ion coordination in the amyloid beta (Aβ) peptide, Aβ1–16 plays a key role in the understanding of the aggregation of Aβ induced by Cu2+ ions. There is no consensus on the nature of the coordination sphere of the Cu2+–Aβ complex so far due to the amorphous conformation of the Aβ1–16 peptide itself and the pH dependence of Cu2+–Aβ coordination. The simulation reported here reveals that human Aβ1–16 monomer has a U‐shape morphology, which is preserved at any pH. This morphology accommodates Cu2+ ions with several binding sites and is also the basis for establishing a center‐distance statistical method (CDSM). Based on this CDSM, specific histidine residues for a Cu2+‐coordinated sphere are identified and the corresponding accurate pH range is established, indicating that the CDSM can be used as a reference to predict the potential coordination sites of metal ions in other amorphous peptides. By contrast, mouse Aβ1–16 monomer has a more open and random morphology than human Aβ1–16 due to the differences of three sequence positions. These mutations not only reduce the number of binding sites required by a stable Cu2+‐binding sphere but also diminish the capacity to generate salt bridges compared to the human peptide. These observations offer insights into the roles of three residues that differ in the mouse Aβ1–16 and perhaps into the reasons mice seldom develop Alzheimer's disease. 相似文献
947.
Rizi Ai M. Qaiser Fatmi Chia-en A. Chang 《Journal of computer-aided molecular design》2010,24(10):819-827
T-Analyst is a user-friendly computer program for analyzing trajectories from molecular modeling. Instead of using Cartesian
coordinates for protein conformational analysis, T-Analyst is based on internal bond-angle-torsion coordinates in which internal
torsion angle movements, such as side-chain rotations, can be easily detected. The program computes entropy and automatically
detects and corrects angle periodicity to produce accurate rotameric states of dihedrals. It also clusters multiple conformations
and detects dihedral rotations that contribute hinge-like motions. Correlated motions between selected dihedrals can also
be observed from the correlation map. T-Analyst focuses on showing changes in protein flexibility between different states
and selecting representative protein conformations for molecular docking studies. The program is provided with instructions
and full source code in Perl. 相似文献
948.
Ai He Chao Zhang Yan Lv Qi‐Zhi Zhong Xi Yang Zhi‐Kang Xu 《Macromolecular rapid communications》2016,37(17):1460-1465
Polydopamine‐based coatings are fabricated via an electric field‐accelerating and ‐directing codeposition process of polydopamine with charged polymers such as polycations, polyanions, and polyzwitterions. The coatings are uniform and smooth on various substrates, especially on those adhesion‐resistant materials including poly(vinylidene fluoride) and poly(tetrafluoroethylene) membranes. Moreover, this electric field‐directed deposition method can be applied to facilely prepare Janus membranes with asymmetric chemistry and wettability.
949.
Ai‐Hong Wu Jian‐Jun Sun Yi‐Min Fang Rui‐Juan Zheng Guo‐Nan Chen 《Electroanalysis》2010,22(22):2702-2707
Hot electron induced cathodic electrochemiluminescence (ECL) was observed at screen printed carbon electrodes (SPCEs) during pulse polarization. The thin insulating film resulted from the printing inks was found to be suitable for generating hot electrons, which can further be converted to hydrated electrons and induce the subsequent luminescence. Compared with disposable Al/Al2O3 electrode, SPCEs show more stable and reproducible ECL in a wider pH range without background emission. A sensitive ECL method for determination of quercetin is proposed. The detection limit is 8.0×10?10 mol L?1(S/N=3), which is two magnitudes lower than that of common ECL method. 相似文献
950.