全文获取类型
收费全文 | 377篇 |
免费 | 11篇 |
国内免费 | 3篇 |
专业分类
化学 | 270篇 |
晶体学 | 5篇 |
力学 | 5篇 |
数学 | 6篇 |
物理学 | 105篇 |
出版年
2022年 | 3篇 |
2020年 | 3篇 |
2019年 | 8篇 |
2018年 | 3篇 |
2016年 | 3篇 |
2015年 | 10篇 |
2014年 | 13篇 |
2013年 | 19篇 |
2012年 | 10篇 |
2011年 | 20篇 |
2010年 | 12篇 |
2009年 | 13篇 |
2008年 | 24篇 |
2007年 | 8篇 |
2006年 | 24篇 |
2005年 | 15篇 |
2004年 | 22篇 |
2003年 | 25篇 |
2002年 | 17篇 |
2001年 | 17篇 |
2000年 | 12篇 |
1999年 | 8篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 9篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 6篇 |
1989年 | 10篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1974年 | 3篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1960年 | 1篇 |
1929年 | 2篇 |
排序方式: 共有391条查询结果,搜索用时 234 毫秒
91.
T. Hattori K. Shirai M. Niwa Y. Murakami 《Reaction Kinetics and Catalysis Letters》1980,15(2):193-196
IR spectra of adsorbed alcohols on alumina were measured under the reaction conditions at elevated temperatures. The transient response of IR absorption intensity indicates that alkoxides are reactive adsorbed species but carboxylates are not. The rate constants of surface reactions were calculated from the transient response.
, . , , , —, .相似文献
92.
Haruyuki Okamura Shogo Toda Masahiro Tsunooka Masamitsu Shirai 《Journal of polymer science. Part A, Polymer chemistry》2002,40(17):3055-3062
Photocrosslinkable systems with thermally cleavable properties based on blends of poly(vinyl phenol) (PVP) and diepoxides were investigated. Thermally cleavable diepoxides as crosslinkers were prepared and characterized. As a thermally cleavable linkage, a tertiary ester moiety was incorporated into the crosslinker molecule. PVP/crosslinker blended films containing photoacid generators (PAGs) became insoluble in solvents after UV irradiation and subsequent post‐exposure‐bake (PEB) treatment. With a rise in the PEB temperature, the insoluble fraction of the irradiated films increased, passed through a maximum value, decreased, and increased again at elevated baking temperatures. The insolubilization profiles of the irradiated films were complicated and strongly dependent on the type of PAG used, the structure of the crosslinkers, and the PVP/crosslinker ratio. A mechanism for the thermal degradation was studied with Fourier transform infrared spectroscopy. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3055–3062, 2002 相似文献
93.
Amenomori M Cao Z Ding LK Feng ZY Hibino K Hotta N Huang Q Huo AX Jia HY Jiang GZ Jiao SQ Kajino F Kasahara K Labaciren Mei DM Meng L Meng XR Mimaciren Mizutani K Mu J Nanjo H Nishizawa M Nusang Oguro A Ohnishi M Ohta I Ren JR Saito T Sakata M Shi ZZ Shibata M Shirai T Sugimoto H Sun XX Tai A Taira K Tan YH Tateyama N Torii S Wang H Wen CZ Yamamoto Y Yao XY Yu GC Yuan P Yuda T Zeng JG Zhang CS Zhang HM Zhang L Zhasang Zhaxiciren Zhou WD 《Physical review D: Particles and fields》1993,47(7):2675-2681
94.
trans-2-Phenyltetrahydrothiophenium 1-methylide (trans-3), which is generated by fluoride ion-induced desilylation of trans-2-phenyl-1-[(trimethylsilyl)methyl]tetrahydrothiophenium salt (trans-2), gave a mixture of 1,4,5,10a-tetrahydro-3H-2-benzothiocine (4) ([2,3]sigmatropic rearrangement product) and 4-methylsulfanyl-1-phenyl-1-butene (5) (Hofmann elimination product). Ylide trans-3 cannot undergo [2,3]sigmatropic rearrangement because the ylide-carbon is too far from the phenyl group, and trans-3 would instead isomerize to cis-3. In this paper, we discuss the mechanism of the isomerization of trans-3 to cis-3. 相似文献
95.
Yokoyama K Teranishi Y Toya Y Shirai T Fukuda Y Aoyama M Akahane Y Inoue N Ueda H Yamakawa K Yokoyama A Yamada H Yabushita A Sugita A 《The Journal of chemical physics》2004,120(20):9446-9449
Optimal laser control for ultrafast selection of closely lying excited states whose energy separation is smaller than the laser bandwidth is reported on the two-photon transition of atomic cesium; Cs(6S-->7D(J), J=5/2 and 3/2). Selective excitation was carried out by pulse shaping of ultrashort laser pulses which were adaptively modulated in a closed-loop learning system handling eight parameters representing the electric field. Two-color fluorescence from the respective excited states was monitored to measure the selectivity. The fitness used in the learning algorithm was evaluated from the ratio of the fluorescence yields. After fifty generations, a pair of nearly transform-limited pulses were obtained as an optimal pulse shape, proving the effectiveness of the "Ramsey fringes" mechanism. The contrast of the selection ratio was improved by approximately 30% from the simple "Ramsey fringes" experiment. 相似文献
96.
T. Nozaki T. Kobayashi M. Shirai 《Journal of Radioanalytical and Nuclear Chemistry》1996,203(1):151-160
Carrier- and salt-free42K milked from an42Ar–42K generator was utilized for isotope dilution analysis of potassium in ultra-pure water. Potassium in the sample marked with the42K was shown to be concentrated easily 60 times by crown-ether extraction and acid back-extraction to be determined by atomic absorption spectrophotometry. The same extractions proved to be effective for removing the reagent blank. Cerenkov radiation counting was often suitable for42K measurement. The42K was used also for studying the interaction of ultra-low concentrations of potassium with vessel walls. 相似文献
97.
Zhao C Nagatsu A Hatano K Shirai N Kato S Ogihara Y 《Chemical & pharmaceutical bulletin》2003,51(3):255-261
Two new podophillotoxin glucosides, L-picropodophillotpxin 7'-O-(beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranoside) (2) and L-picropodophillotpxin 7'-O-beta-D-glucopyranoside (3), were isolated from Chinese medicinal plant, Sinopodophillum emodi, together with 4 known compounds, podophillotoxin (1), podorhizol 4'-O-beta-D-glucopyranoside (4), deoxypodophillotoxin (5), and dehydropodophillotoxin (6). The structures of 2 and 3 were finally determined by the extensive decouping and nuclear Overhauser effect (NOE) experiments in NMR spectra and circular dichroism (CD) spectra. Compound 2 is the second example of podophillotoxin diglucoside, and both the first one and 2 were isolated from S. emodi. X-ray crystal structure analysis of 1, 5, and 6 was carried out. Compounds 1 and 5 showed the different conformations from those reported. 相似文献
98.
T. Kandler Th. Stöhlker P. H. Mokler C. Kozhuharov H. Geissel C. Scheidenberger P. Rymuza Z. Stachura A. Warczak R. W. Dunford J. Eichler A. Ichihara T. Shirai 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1995,35(1):15-18
Measurements of the photon angular distribution of Radiative Electron Capture into the M shell have been performed with He-like uranium ions in the range 110–140 MeV/u. In addition, L REC was studied at a projectile energy of 140 MeV/u. In both cases, the experimental data show an asymmetry around 90° and agree well with a fully relativistic theory. 相似文献
99.
Fengyu Zhao Yutaka Ikushima Masayuki Shirai Takeo Ebina Masahiko Arai 《Journal of molecular catalysis. A, Chemical》2002,180(1-2)
The selective hydrogenation of cinnamaldehyde (CAL) was investigated using silica supported platinum catalysts in supercritical carbon dioxide. Selectivity to cinnamyl alcohol (COL) is enhanced as Pt0/Pt2+ ratio increases; namely, zero-valent metallic surface is beneficial to the formation of COL compared with less reduced surface. The influence of Pt0/Pt2+ ratio is more significant on the selectivity than on the total conversion. For the catalyst with small Pt0/Pt2+ value, the selectivity also depends on the degree of platinum dispersion. The selectivity to COL is higher for higher degree of platinum dispersion. The CO2 pressure did not affect the conversion and selectivity so much. 相似文献
100.
H. Inoue T. Kuroiwa T. Shirai E. Fluck 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4)
Abstract A series of mixed ligand complexes of the type [Fe(CO)3L1L2] (L1=tri-phenylphosphite and L2=phosphine or phosphite) have been prepared to study the Fe-P bond. The 57Fe Mössbauer spectra of trans-[Fe(CO)3L1L2] showed a quadrupole splitting doublet characteristic of the disubstituted iron carbonyls in trigonal bipyramidal symmetry. The linear dependence of the quadrupole splittings on the isomer shifts with a positive slope has revealed that the iron-to-phosphorus σ-donation is offset by the phosphorus-to-iron π-back donation. The 31P{1H} NMR spectra showed a couple of doublets assigned to the coordinated phosphite and the coordinated phosphine. The doublet of the phosphite site was generally observed at the down field compared with that of the phosphine site. The coordination shifts increase with the Mössbauer isomer shifts, suggesting that the iron-to-phosphorus π-back donation plays an important role in the Fe-P bond of trans-[Fe(CO)3L1L2]. The relatively large coupling constants due to 2J(P,P) have demonstrated that there exists a strong interaction between trans phosphorus ligands through the dπ orbitals of the central iron. The coupling constant is a measure of the bond strength between Fe-P, while the Mössbauer isomer shift reflects the electron density at the iron nucleus. Thus, a linear correlation has been established between these two spectroscopic parameters. 相似文献