全文获取类型
收费全文 | 588篇 |
免费 | 35篇 |
国内免费 | 6篇 |
专业分类
化学 | 519篇 |
晶体学 | 5篇 |
力学 | 4篇 |
数学 | 29篇 |
物理学 | 72篇 |
出版年
2023年 | 5篇 |
2022年 | 4篇 |
2021年 | 10篇 |
2020年 | 9篇 |
2019年 | 19篇 |
2018年 | 10篇 |
2017年 | 6篇 |
2016年 | 19篇 |
2015年 | 11篇 |
2014年 | 19篇 |
2013年 | 29篇 |
2012年 | 33篇 |
2011年 | 37篇 |
2010年 | 17篇 |
2009年 | 17篇 |
2008年 | 35篇 |
2007年 | 39篇 |
2006年 | 36篇 |
2005年 | 35篇 |
2004年 | 30篇 |
2003年 | 31篇 |
2002年 | 19篇 |
2001年 | 11篇 |
2000年 | 9篇 |
1999年 | 9篇 |
1998年 | 12篇 |
1997年 | 8篇 |
1996年 | 13篇 |
1995年 | 3篇 |
1994年 | 11篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1973年 | 2篇 |
1969年 | 2篇 |
1968年 | 2篇 |
排序方式: 共有629条查询结果,搜索用时 53 毫秒
621.
Structures of small mixed krypton-xenon clusters of different compositions with an average size of 30-37 atoms are investigated. The Kr 3d(5/2) and Xe 4d(5/2) surface core level shifts and photoelectron intensities originating from corner, edge, and face/bulk sites are analyzed by using soft x-ray photoelectron spectroscopy. Structural models are derived from these experiments, which are confirmed by theoretical simulation taking induced dipole interactions into account. It is found that one or two small Xe cores are partly embedded in the surface of the Kr clusters. These may grow and merge leading to a phase separation between the two rare gas moieties in mixed clusters with increasing the Xe content. 相似文献
622.
Recent experimental data by Mizoguchi and Ohta are analyzed under the assumption of fast equilibrium between the locally excited (LE), radical-ion-pair (RIP), and exciplex states. In the absence of the equilibrium, no magnetic field effect on the LE fluorescence would be observed. Owing to the equilibrium, the relative electric-field-induced changes of the quantum yields of the LE and exciplex emissions as functions of the magnetic field are linearly connected to each other. The electric field shifts the equilibrium from the LE state toward the RIP state. Predictions are made for the magnetic field effect on the fluorescence kinetics. 相似文献
623.
Mizuhata Y Sasamori T Takeda N Tokitoh N 《Journal of the American Chemical Society》2006,128(4):1050-1051
A kinetically stabilized 2-stannanaphthalene, the first example of a stable, neutral aromatic compound containing a tin atom, has been synthesized and fully characterized. The results of spectroscopic and crystallographic structural analyses of the compound and theoretical calculations using model compounds strongly suggest that it has a delocalized 10pi-electron ring system as does naphthalene. In addition, it was found to behave as an eta6-arene ligand in the ligand exchange reaction with [Cr(CH3CN)3(CO)3] giving the first stable eta6-2-stannanaphthalene chromium complex. 相似文献
624.
Asteropine A, a sialidase-inhibiting conotoxin-like peptide from the marine sponge Asteropus simplex
Takada K Hamada T Hirota H Nakao Y Matsunaga S van Soest RW Fusetani N 《Chemistry & biology》2006,13(6):569-574
Marine sponges contain structurally intriguing and biologically active peptides of nonribosomal peptide synthase origin, often containing amino acids with novel structures. Here we report the discovery of asteropine A (APA), a cystine knot to be isolated from marine sponges. The solution structure of APA as determined by NMR belongs to the four-loop class of cystine knots similar to those of some conotoxins and spider toxins. However, the highly negatively charged surface of APA is uncommon among other cystine knots. APA competitively inhibits bacterial sialidases, but not a viral sialidase. APA was inactive against all other enzymes tested and did not have any apparent antitumor activity. Our data suggest that APA and other knotting peptides may be important leads for antibacterial and even antiviral drug development. 相似文献
625.
The reaction of a bulky hexathioether, TbtS(o-Phen)S(o-Phen)SS(o-Phen)S(o-Phen)STbt (o-Phen = o-phenylene, Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl) (1), with 3 molar amounts of Pd(PPh3)4 afforded trinuclear palladium complex bridged by two benzenedithiolato ligands via a three-step palladium insertion reaction into one sulfur-sulfur and two carbon-sulfur bonds of 1. 相似文献
626.
627.
Nobuhiro Takahashi 《Tetrahedron》2010,66(39):7787-7793
The Diels-Alder reaction between C60 and anthryl glycodendron, which has d- or l-gluconamides at the terminals, gave a new fullerene glycodendron conjugate. Interestingly, the diastereoselective cycloaddition reaction proceeded upon the treatment of C60 with the anthryl dendron 3. Furthermore, optical pure fullerodendrons (−)-4L and (+)-4D, which were confirmed by 1H and 13C NMR spectroscopy, FT-IR, MALDI-TOF mass spectroscopic analysis, were isolated from the mixture of diastereomers. And their absolute configurations were predicted by the use of CD spectra. 相似文献
628.
Yuto Suzuki Mario Gutirrez Senri Tanaka Eduardo Gomez Norimitsu Tohnai Nobuhiro Yasuda Nobuyuki Matubayasi Abderrazzak Douhal Ichiro Hisaki 《Chemical science》2022,13(48):14410
Correction for ‘Construction of isostructural hydrogen-bonded organic frameworks: limitations and possibilities of pore expansion’ by Yuto Suzuki et al., Chem. Sci., 2021, 12, 9607–9618, https://doi.org/10.1039/D1SC02690A.The authors regret that CPHAT-1 CBPHAT-1 TolHAT-1 ThiaHAT-1 Periodicity of the framework/Å 21.48 29.75 34.40 38.01 RMSD of the HAT core plane/Å 0.267 0.205 0.215 0.229 Stacking distance/Å 3.59 3.57 3.49 3.49 Torsion angle of arms/° 22.5 22.1 23.5 24.5 Number of interpenetrations 4 6 8 8 Height of the channel aperture/Å 6.4 14.5 19.2 18.0 Void ratio 0.31 0.45 0.55 0.48 Pore width based on NLDFT/Å —a 12.4 16.6 15.5 BET surface area/m2 g−1 649 1288 440 1394 N2 uptake/mL (STP) g−1 21.39 361.7 155.2 415.7 CO2 uptake/mL (STP) g−1 137.4 304.5 168.6 313.9 Decomposition temp./°C 339 307 190 305 Ref. Ref. 36 Ref. 37 This work This work