全文获取类型
收费全文 | 1577篇 |
免费 | 37篇 |
国内免费 | 12篇 |
专业分类
化学 | 946篇 |
晶体学 | 12篇 |
力学 | 45篇 |
数学 | 249篇 |
物理学 | 374篇 |
出版年
2023年 | 9篇 |
2022年 | 10篇 |
2021年 | 13篇 |
2020年 | 27篇 |
2019年 | 29篇 |
2018年 | 18篇 |
2017年 | 11篇 |
2016年 | 28篇 |
2015年 | 25篇 |
2014年 | 29篇 |
2013年 | 67篇 |
2012年 | 60篇 |
2011年 | 80篇 |
2010年 | 54篇 |
2009年 | 48篇 |
2008年 | 73篇 |
2007年 | 68篇 |
2006年 | 74篇 |
2005年 | 79篇 |
2004年 | 66篇 |
2003年 | 67篇 |
2002年 | 47篇 |
2001年 | 20篇 |
2000年 | 20篇 |
1999年 | 24篇 |
1998年 | 17篇 |
1997年 | 9篇 |
1996年 | 15篇 |
1995年 | 8篇 |
1994年 | 18篇 |
1993年 | 11篇 |
1992年 | 14篇 |
1991年 | 14篇 |
1990年 | 15篇 |
1989年 | 8篇 |
1985年 | 27篇 |
1984年 | 21篇 |
1983年 | 19篇 |
1982年 | 36篇 |
1981年 | 35篇 |
1980年 | 22篇 |
1979年 | 12篇 |
1978年 | 23篇 |
1977年 | 10篇 |
1976年 | 16篇 |
1975年 | 15篇 |
1974年 | 18篇 |
1973年 | 15篇 |
1971年 | 8篇 |
1965年 | 9篇 |
排序方式: 共有1626条查询结果,搜索用时 218 毫秒
951.
The photocyclisation rate of 2-allyl-3-(or 5-)aminophenols (1, 4 and 8) is dramatically enhanced, when compared with reference compounds, as a consequence of a coupled proton/electron transfer process. 相似文献
952.
Time differences between the two ears are an important cue for animals to azimuthally locate a sound source. The first binaural brainstem nucleus, in mammals the medial superior olive, is generally believed to perform the necessary computations. Its cells are sensitive to variations of interaural time differences of about 10 micros. The classical explanation of such a neuronal time-difference tuning is based on the physical concept of delay lines. Recent data, however, are inconsistent with a temporal delay and rather favor a phase delay. By means of a biophysical model we show how spike-timing-dependent synaptic learning explains precise interplay of excitation and inhibition and, hence, accounts for a physical realization of a phase delay. 相似文献
953.
Airapetian A Akopov N Akopov Z Amarian M Andrus A Aschenauer EC Augustyniak W Avakian R Avetissian A Avetissian E Bacchetta A Bailey P Balin D Beckmann M Belostotski S Bianchi N Blok HP Böttcher H Borissov A Borysenko A Bouwhuis M Brüll A Bryzgalov V Capitani GP Cappiluppi M Chen T Ciullo G Contalbrigo M Dalpiaz PF Leo RD Demey M Nardo LD Sanctis ED Devitsin E Nezza PD Düren M Ehrenfried M Elalaoui-Moulay A Elbakian G Ellinghaus F Elschenbroich U Fabbri R Fantoni A Fechtchenko A Felawka L 《Physical review letters》2005,94(1):012002
Single-spin asymmetries for semi-inclusive electroproduction of charged pions in deep-inelastic scattering of positrons are measured for the first time with transverse target polarization. The asymmetry depends on the azimuthal angles of both the pion (phi) and the target spin axis (phi(S)) about the virtual-photon direction and relative to the lepton scattering plane. The extracted Fourier component sin((phi+phi(S))(pi)(UT) is a signal of the previously unmeasured quark transversity distribution, in conjunction with the Collins fragmentation function, also unknown. The component sin((phi-phi(S)(pi)(UT) arises from a correlation between the transverse polarization of the target nucleon and the intrinsic transverse momentum of quarks, as represented by the previously unmeasured Sivers distribution function. Evidence for both signals is observed, but the Sivers asymmetry may be affected by exclusive vector meson production. 相似文献
954.
The structure of 4-methylphenol (p-cresol) and its binary water cluster have been elucidated by rotationally resolved laser-induced fluorescence spectroscopy. The electronic origins of the monomer and the cluster are split into four sub-bands by the internal rotation of the methyl group and of the hydroxy group in case of the monomer, and the water moiety in case of the cluster. From the rotational constants of the monomer the structure in the S1 state could be determined to be distorted quinoidally. The structure of the p-cresol-water cluster is determined to be trans linear, with a O-O hydrogen bond length of 290 pm in the electronic ground state and of 285 pm in the electronically excited state. The S1-state lifetime of p-cresol, p-cresol-d1, and the binary water cluster have been determined to be 1.6, 9.7, and 3.8 ns, respectively. 相似文献
955.
956.
957.
958.
M. Di Maina S. Cesca P. Giusti G. Ferraris und P. L. Magagnini 《Colloid and polymer science》1978,256(11):1153
Ohne Zusammenfassung 相似文献
959.
960.
Kolmogorov-Arnol'd-Moser (KAM) surfaces are studied in the context of a perturbed two-dimensional twist map. In particular, we ask how a KAM surface can disappear as the perturbation parameter is increased. Following Greene, we use cycles to numerically construct the KAM curve and discover that at the critical coupling it shows structure at all length scales. Aspects of this structure are fitted by a scaling analysis; critical indices and scaling functions are determined numerically. Some evidence is presented which suggests that the results are universal.Supported in part by the Materials Research Laboratory Program of the National Science Foundation at the University of Chicago under grant No. NSF-MRL 7924007.Robert R. McCormick and National Science Foundation Fellow 相似文献