全文获取类型
收费全文 | 1232篇 |
免费 | 71篇 |
国内免费 | 7篇 |
专业分类
化学 | 1051篇 |
晶体学 | 13篇 |
力学 | 12篇 |
数学 | 70篇 |
物理学 | 164篇 |
出版年
2023年 | 6篇 |
2022年 | 18篇 |
2021年 | 18篇 |
2020年 | 24篇 |
2019年 | 41篇 |
2018年 | 16篇 |
2017年 | 15篇 |
2016年 | 45篇 |
2015年 | 35篇 |
2014年 | 44篇 |
2013年 | 82篇 |
2012年 | 97篇 |
2011年 | 87篇 |
2010年 | 64篇 |
2009年 | 60篇 |
2008年 | 79篇 |
2007年 | 72篇 |
2006年 | 70篇 |
2005年 | 59篇 |
2004年 | 62篇 |
2003年 | 43篇 |
2002年 | 38篇 |
2001年 | 13篇 |
2000年 | 15篇 |
1999年 | 13篇 |
1998年 | 11篇 |
1997年 | 5篇 |
1996年 | 18篇 |
1995年 | 9篇 |
1994年 | 12篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 7篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 12篇 |
1986年 | 12篇 |
1985年 | 6篇 |
1984年 | 14篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1970年 | 2篇 |
1967年 | 3篇 |
排序方式: 共有1310条查询结果,搜索用时 15 毫秒
151.
Polycyclic aromatic compounds can be synthesized from 2-benzylic- or 2-allylbenzaldehydes using a catalytic amount of In(III) or Re(I) complexes. By using this method, polycyclic aza-aromatic compounds can also be prepared efficiently. In these reactions, only water is formed as a side product. 相似文献
152.
Fujioka H Nakahara K Hirose H Hirano K Oki T Kita Y 《Chemical communications (Cambridge, England)》2011,47(3):1060-1062
A novel and rapid approach to chiral mono- or di-substituted spiroketals based on remote asymmetric induction by intramolecular iodoetherification of ene or diene ketals has been developed. This strategy concisely offers 5,5- and 5,6-spiroketals including the natural insect pheromone of the wasp. 相似文献
153.
Shiraki T Dawn A Le TN Tsuchiya Y Tamaru S Shinkai S 《Chemical communications (Cambridge, England)》2011,47(25):7065-7067
A thermo- and light-responsive system consisting of single-walled carbon nanotube and helical polysaccharide modified with poly(N-isopropylacrylamide) side-chains has been developed through supramolecular polymer wrapping. Coagulation of the complex can be induced by the external stimuli, which leads to a catch-and-release action of a porphyrin derivative. 相似文献
154.
Noriaki Nishiguchi Takafumi Kinuta Yoko Nakano Dr. Takunori Harada Dr. Nobuo Tajima Tomohiro Sato Prof. Dr. Michiya Fujiki Prof. Dr. Reiko Kuroda Prof. Dr. Yoshio Matsubara Dr. Yoshitane Imai 《化学:亚洲杂志》2011,6(4):1092-1098
The solid‐state chiral optical properties of a 4‐(2‐arylethynyl)‐benzoic acid/amine supramolecular organic fluorophore can be controlled by changing the arylethynyl group of the achiral 4‐(2‐arylethynyl)‐benzoic acid component molecule rather than the chirality of the amine component molecule. 相似文献
155.
Tomohiro Shirai 《Optical Review》2005,12(2):115-121
A modified arrangement of the adaptive optical retinal imaging system that we described previously is proposed to reduce the intensity loss in the system, so that it works properly even when the intensity of light incident on the eye is very weak. Experiments to verify the system performance were conducted using a conventional artificial eye with a specular reflector as a model retina. We observed that an image of a test target (mimicking a retina) blurred by an aberration plate (mimicking the ocular aberrations) was successfully restored in the adaptive optics fashion even when the intensity of the incident light probing the aberration of the eye became about 1.5% of that required in the previous system. Effect of a more realistic artificial eye with a scattering object as a model retina was also examined experimentally. We found that not only the ocular aberrations, but also the retinal scattering cause the wave-front deformations and that our adaptive optics system compensates for both of them simultaneously. 相似文献
156.
Tomohiro Yasuda Kenji Miyatake Michiko Hirai Masato Nanasawa Masahiro Watanabe 《Journal of polymer science. Part A, Polymer chemistry》2005,43(19):4439-4445
A series of sulfopropylated and sulfobutylated polyimide copolymers containing fluorenyl groups, SPI‐4, were synthesized to investigate the effect of alkyl side chains on the properties (stability, mechanical strength, water uptake, and proton conductivity) of the polymimide electrolyte membranes. SPI‐4 showed much better hydrolytic stability (in 10% MeOH aq at 100 °C) than the main chain sulfonated polyimide, SPI‐1. Tough, flexible, and ductile membranes were obtained from these copolymers. At high relative humidity all the SPI‐4 membranes showed high mechanical properties (>34 MPa of the maximum stress) and proton conductivity (>0.1 Scm?1). These properties are comparable to or even better than those of the perfluorosulfonic acid ionomer (Nafion 112). The new polyimide ionomers have proved to be a possible candidate as polymer electrolyte membrane for PEFCs and DMFCs. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4439–4445, 2005 相似文献
157.
158.
Tsuneyuki Sato Masahiko Hashimoto Makiko Seno Tomohiro Hirano 《Journal of polymer science. Part A, Polymer chemistry》2003,41(12):1819-1830
The polymerizations of α‐ethyl β‐N‐(α′‐methylbenzyl)itaconamates carrying (RS)‐ and (S)‐α‐methylbenzylaminocarbonyl groups (RS‐EMBI and S‐EMBI) with dimethyl 2,2′‐azobisisobutyrate (MAIB) were studied in methanol (MeOH) and in benzene kinetically and with electron spin resonance (ESR) spectroscopy. The initial polymerization rate (Rp) at 60 °C was given by Rp = k[MAIB]0.58 ± 0.05[RS‐EMBI]2.4 ± 0.l and Rp = k[MAIB]0.61 ± 0.05[S‐EMBI]2.3 ± 0.l in MeOH and Rp = k[MAIB]0.54 ± 0.05[RS‐EMBI]1.7 ± 0.l in benzene. The rate constants of initiation (kdf), propagation (kp), and termination (kt) as elementary reactions were estimated by ESR, where kd is the rate constant of MAIB decomposition and f is the initiator efficiency. The kp values of RS‐EMBI (0.50–1.27 L/mol s) and S‐EMBI (0.42–1.32 L/mol s) in MeOH increased with increasing monomer concentrations, whereas the kt values (0.20?7.78 × 105 L/mol s for RS‐EMBI and 0.18?6.27 × 105 L/mol s for S‐EMBI) decreased with increasing monomer concentrations. Such relations of Rp with kp and kt were responsible for the unusually high dependence of Rp on the monomer concentration. The activation energies of the elementary reactions were also determined from the values of kdf, kp, and kt at different temperatures. Rp and kp of RS‐EMBI and S‐EMBI in benzene were considerably higher than those in MeOH. Rp of RS‐EMBI was somewhat higher than that of S‐EMBI in both MeOH and benzene. Such effects of the kinds of solvents and monomers on Rp were explicable in terms of the different monomer associations, as analyzed by 1H NMR. The copolymerization of RS‐EMBI with styrene was examined at 60 °C in benzene. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1819–1830, 2003 相似文献
159.
T. Okamoto T. Omori K. Yoshihara 《Journal of Radioanalytical and Nuclear Chemistry》1984,85(4):245-251
The chemical species of carrier-free technetium, which were extractable into a TTA-benzene solution on reduction of96TcO
4
–
either with NaBH4 or concentrated HCl, were studied by means of silica gel chromatography. Elution peaks ascribed to the formation of Tc/tta/4 and Tc/tta/3 type complexes were observed. The latter complex was also synthesized by recoil effect of Ru/, p/Tc reactions in -irradiated Ru/tta/3. 相似文献
160.
T. Omori K. Omori C. Ochi K. Yoshihara M. Yagi 《Journal of Radioanalytical and Nuclear Chemistry》1984,82(1):61-69
In order to produce routinely carrier-free96Tc and111In, their simultaneous production was examined by means of the stacked foil method. Both niobium and silver foils were arranged on the target holder so as the desired nuclear reactions took place effectively. Simultaneous irradiation of the target with 35 MeV -particles produced effectively111In and96Tc by the109Ag(, 2n)111In and93Nb(, n)96Tc reactions, respectively. Sufficient amounts of radioactivities for tracer uses are obtained by the irradiation at 5 A current for 2 hrs. In addition, carrier-free96TcO4
– in a perchloric acid solution could be prepared by the combined use of precipitation and anion-exchange methods. Separation of carrier-free111In from the silver matrix was done by means of solvent extraction using acetylacetone as a chelating agent. 相似文献