全文获取类型
收费全文 | 952篇 |
免费 | 31篇 |
国内免费 | 2篇 |
专业分类
化学 | 683篇 |
晶体学 | 14篇 |
力学 | 7篇 |
数学 | 43篇 |
物理学 | 238篇 |
出版年
2023年 | 6篇 |
2021年 | 7篇 |
2020年 | 12篇 |
2019年 | 18篇 |
2018年 | 15篇 |
2017年 | 7篇 |
2016年 | 29篇 |
2015年 | 15篇 |
2014年 | 16篇 |
2013年 | 50篇 |
2012年 | 40篇 |
2011年 | 45篇 |
2010年 | 16篇 |
2009年 | 30篇 |
2008年 | 68篇 |
2007年 | 35篇 |
2006年 | 51篇 |
2005年 | 44篇 |
2004年 | 34篇 |
2003年 | 31篇 |
2002年 | 43篇 |
2001年 | 18篇 |
2000年 | 30篇 |
1999年 | 11篇 |
1998年 | 8篇 |
1997年 | 9篇 |
1996年 | 22篇 |
1995年 | 11篇 |
1994年 | 6篇 |
1993年 | 13篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 13篇 |
1989年 | 10篇 |
1988年 | 18篇 |
1987年 | 14篇 |
1986年 | 16篇 |
1985年 | 20篇 |
1984年 | 15篇 |
1983年 | 11篇 |
1982年 | 6篇 |
1981年 | 12篇 |
1980年 | 4篇 |
1979年 | 9篇 |
1978年 | 10篇 |
1977年 | 12篇 |
1976年 | 10篇 |
1975年 | 13篇 |
1973年 | 5篇 |
1972年 | 5篇 |
排序方式: 共有985条查询结果,搜索用时 171 毫秒
71.
72.
73.
74.
Kentaro Okuma Jun-ichi Sakata Yuji Tachibana Takumi Honda Hiroshi Ohta 《Tetrahedron letters》1987,28(52):6649-6652
Wittig reagents were successfully changed to symmetrical olefins when treated with elemental selenium. The reaction proceeds through a selenocarbonyl intermediate, which existence was confirmed by Diels-Alder reaction. 相似文献
75.
76.
77.
Hidekazu Miyaji Junko Fujimoto Riho Mabuchi Moeno Okumura Shoichiro Goto Youtaro Honda 《Tetrahedron letters》2017,58(37):3623-3627
A novel molecular sensor using anthracene bearing two amidopyridines emits blue fluorescence in the presence of succinic acid and green fluorescence in the presence of malonic acid, and its fluorescence intensity increased upon binding. Using this molecular sensor, we succeeded in detecting the difference of one carbon atom between succinic acid and malonic acid with the naked-eye. Furthermore, when methylmalonic acid was dissolved in urine to provide a model system for methylmalonic aciduria, the fluorescence changed from blue to green, and methylmalonic acid was successfully detected with the naked-eye. 相似文献
78.
Eiji Takahashi Hikaru Takaya Dr. Takeshi Naota Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(16):4793-4802
The first vapochromic organic crystals are described with respect to their preparation, color change, adsorption/desorption properties, crystal structures, and color‐change mechanism. Non‐solvatochromic, 1,4,5,8‐naphthalene‐tetracarboxylic diimide (NDI) derivatives 1 a bearing two pyrrole imine (PI) tethers have been used as a motif for the crystal packing template. Red‐purple vapochromic solid 3 was prepared by evacuation of orange crystals 2 (equivalent to 1 a ?2 MeOH), obtained by recrystallization of 1 a from MeOH. Solid 3 showed high‐adsorption ability and unprecedented vapor‐dependent color changes upon exposure to a variety of organic vapors, whereas light brown amorphous solid 1 a , did not show vapo‐ or solvatochromic behavior toward any organic solvent. The strong adsorption capability of 3 was confirmed by TGA experiments and adsorption/desorption isotherms. Analysis of the solid‐state UV/Vis analysis revealed that the vapor‐dependent color changes of 3 were owed to the specific interference of solvent vapors with its broad CT absorbance at λ=450–650 nm. Packing structures of 1 a in orange crystals 2 , red‐purple solid 3 , and regenerated orange solid 2 were unequivocally established by single crystal and synchrotron powder X‐ray diffraction, respectively. Molecular structures and arrays of 1 a in these materials indicated that 1) unit 1 a had an S‐shaped folded conformation in 2 and 3 by intramolecular donor–acceptor interactions between NDI and two PI units; 2) inclusion of the guest vapor into the S‐shaped template decreased the intramolecular PI‐NDI interactions, accompanied by increasing intermolecular NDI‐NDI and PI‐PI interactions; and 3) such flexible, open–close motions of the S‐shaped template could be repeated during reversible adsorption/desorption processes without degradation of crystal packing. The adsorption properties and mechanism of molecular shape‐dependent vapochromic behavior of 3 are discussed with reference to experimental results, crystallographic data, and theoretical calculations. 相似文献
79.
Dynamic properties of combustion instability in a lean premixed gas-turbine combustor 总被引:1,自引:0,他引:1
We experimentally investigate the dynamic behavior of the combustion instability in a lean premixed gas-turbine combustor from the viewpoint of nonlinear dynamics. A nonlinear time series analysis in combination with a surrogate data method clearly reveals that as the equivalence ratio increases, the dynamic behavior of the combustion instability undergoes a significant transition from stochastic fluctuation to periodic oscillation through low-dimensional chaotic oscillation. We also show that a nonlinear forecasting method is useful for predicting the short-term dynamic behavior of the combustion instability in a lean premixed gas-turbine combustor, which has not been addressed in the fields of combustion science and physics. 相似文献
80.
Mori T Iwamoto K Kushibiki S Honda H Matsumoto H Toyota N Avila MA Suekuni K Takabatake T 《Physical review letters》2011,106(1):015501
We present optical conductivity studies of the type-I clathrate Ba8Ga16Sn30, using a terahertz time-domain spectrometer (0.3-3.0?THz). The lowest-lying spectral peak at 0.72?THz due to the Ba(2) ion's off-center vibration in the oversized cage shows a drastic and anomalous temperature dependence. Below about 100?K, the single broad peak splits into two subpeaks, and with further lowering of the temperature, the spectral shape of this so-called rattling phonon shows non-Boltzmann broadening to the point that the linewidth becomes comparable to the peak frequency. Whereas the initial splitting can be understood by assuming a multiwell anharmonic potential, the strong linewidth broadening toward low temperature cannot, since the Boltzmann factor generally sharpens the low-temperature spectra. The observed behavior suggests strong interaction between the local anharmonic phonons and other excitations. 相似文献