全文获取类型
收费全文 | 2253篇 |
免费 | 58篇 |
国内免费 | 4篇 |
专业分类
化学 | 1816篇 |
晶体学 | 30篇 |
力学 | 24篇 |
数学 | 119篇 |
物理学 | 326篇 |
出版年
2022年 | 7篇 |
2021年 | 10篇 |
2020年 | 16篇 |
2019年 | 26篇 |
2018年 | 26篇 |
2017年 | 10篇 |
2016年 | 42篇 |
2015年 | 40篇 |
2014年 | 50篇 |
2013年 | 92篇 |
2012年 | 101篇 |
2011年 | 122篇 |
2010年 | 81篇 |
2009年 | 55篇 |
2008年 | 131篇 |
2007年 | 126篇 |
2006年 | 111篇 |
2005年 | 110篇 |
2004年 | 116篇 |
2003年 | 130篇 |
2002年 | 103篇 |
2001年 | 57篇 |
2000年 | 83篇 |
1999年 | 36篇 |
1998年 | 26篇 |
1997年 | 36篇 |
1996年 | 34篇 |
1995年 | 33篇 |
1994年 | 24篇 |
1993年 | 27篇 |
1992年 | 31篇 |
1991年 | 22篇 |
1990年 | 21篇 |
1989年 | 14篇 |
1988年 | 24篇 |
1987年 | 11篇 |
1986年 | 13篇 |
1985年 | 30篇 |
1984年 | 28篇 |
1983年 | 18篇 |
1982年 | 23篇 |
1981年 | 26篇 |
1980年 | 28篇 |
1979年 | 30篇 |
1978年 | 29篇 |
1977年 | 18篇 |
1976年 | 16篇 |
1975年 | 11篇 |
1974年 | 11篇 |
1973年 | 10篇 |
排序方式: 共有2315条查询结果,搜索用时 15 毫秒
21.
22.
Tolerance bioaccumulation and biotransformation of arsenic compounds by a freshwater prawn (Macrobrachium rosenbergii) were investigated. M. rosenbergii was exposed to 10, 20, 30 and 35 μg As cm−3 of disodium arsenate [abbreviated as As(V)], 25, 50, 100 and 120 μg As cm−3 of methylarsonic acid (MMAA), or 100,200, 300 and 350 μg As cm−3 of dimethylarsinic acid (DMAA). Tolerances (50% lethal concentration: LC50) of the prawn against As(V), MMAA, and DMAA were 30, 100, and 300 μg As cm−3, respectively. The prawn accumulated arsenic compounds directly from aqueous phase and biotransformed them in part. Both methylation and demethylation of the arsenicals were observed in vivo. Highly methylated and less toxic arsenicals were less accumulated in M. rosenbergii. 相似文献
23.
Yuzuru Uchida Katsumi Onoue Nobuaki Tada Fumio Nagao Hideaki Kozawa Shigeru Oae 《Heteroatom Chemistry》1990,1(4):295-306
Phosphine oxides bearing two or three 2-pyridyl groups react with organometallic reagents affording 2,2′-bipyridyl, 2-substituted pyridines and pyridine in good yields. Phosphonium salts and phosphine oxides, bearing at least two 2-pyridyl or substituted 2-pyridyl groups also give the corresponding 2,2′-bipyridyls and pyridines upon treatment with acid or neutral solvents such as water and alcohols in substantial yields. The 2,2′-bipyridyls are considered to be formed by ligand coupling within the pentacoordinated phosphorus intermediate formed incipiently during the reaction. 相似文献
24.
Shigeru Wada 《Macromolecular Symposia》1992,57(1):327-329
The degradation of the physical properties of polypropylene (PP) used for automotive outer trims for several years is unexpectedly small. It, therefore, can be fully anticipated that PP so used can be recycled for the same purpose or for other applications. 相似文献
25.
Serrano J Bosak A Krisch M Manjón FJ Romero AH Garro N Wang X Yoshikawa A Kuball M 《Physical review letters》2011,106(20):205501
Achieving comprehensive information on thin film lattice dynamics so far has eluded well established spectroscopic techniques. We demonstrate here the novel application of grazing incidence inelastic x-ray scattering combined with ab initio calculations to determine the complete elastic stiffness tensor, the acoustic and low-energy optic phonon dispersion relations of thin wurtzite indium nitride films. Indium nitride is an especially relevant example, due to the technological interest for optoelectronic and solar cell applications in combination with other group III nitrides. 相似文献
26.
Katsuhiro Munakata Kenji Harada Nobukazu Yoshikawa Masahide Itoh Shinsuke Umegaki Toyohiko Yatagai 《Optical Review》1999,6(6):518-521
Two fabrication methods of surface relief electro-optic (EO) gratings in azo-polymer films are described: surface deformation by a continuous wave laser and laser ablation by a pulse laser. In the fabrication process, the periodic intensity modulation of laser beams is formed by an interference fringe or a phase mask. The surface relief EO grating is fabricated by poling the surface relief grating (SRG) after the SRG fabrication process. The linear dependence of an applied voltage in the modulation efficiency of the first-order diffraction beam is observed. The proposed methods are effective for highly-efficient surface relief EO grating fabrication. 相似文献
27.
28.
Xiaopei Li Tasuku Ogihara Prof. Dr. Manabu Abe Dr. Yasuyuki Nakamura Prof. Dr. Shigeru Yamago 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(42):9846-9850
The effect of viscosity on the diffusion efficiency (Fdif) of an organic radical pair in a solvent cage and the termination mechanism, that is, the selectivity of disproportionation (Disp) and combination (Comb) of the geminated caged radical pair and the diffused radicals encountered, were investigated quantitatively by following the photolysis of dimethyl 2,2′-azobis(2-methylpropionate) (V-601) in the absence and presence of PhSD. Fdif and Disp/Comb selectivity outside the cage [Disp(dif)/Comb(dif)] are highly sensitive to the viscosity. In contrast, the Disp/Comb selectivity inside the cage [Disp(cage)/Comb(cage)] is rather insensitive. The difference in viscosity dependence between Disp(cage)/Comb(cage) and Disp(dif)/Comb(dif) is explained by the spin state of the radical pair inside and outside the cage and the spin state dependent configurational changes of the radical pair upon their collision. Given that the configurational change of the radicals associates the displacement and reorganization of solvents around the radicals, the termination outside the cage, which requires larger change than that inside the cage, is highly viscosity dependent. Furthermore, while the bulk viscosity of each solvent shows good correlation with Fdif and Disp/Comb selectivity, microviscosity is the better parameter predicting Fdif and Disp(dif)/Comb(dif) selectivity regardless of the solvents. 相似文献
29.
Hashi K Shimizu T Goto A Kiyoshi T Matsumoto S Wada H Fujito T Hasegawa K Yoshikawa M Miki T Ito S Hamada M Hayashi S 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2002,156(2):318-321
We have developed a 920-MHz NMR system and performed the proton NMR measurement of H(2)O and ethylbenzene using the superconducting magnet operating at 21.6 T (920 MHz for proton), which is the highest field produced by a superconducting NMR magnet in the persistent mode. From the NMR measurements, it is verified that both homogeneity and stability of the magnet have a specification sufficient for a high resolution NMR. 相似文献
30.