全文获取类型
收费全文 | 920篇 |
免费 | 27篇 |
国内免费 | 1篇 |
专业分类
化学 | 668篇 |
晶体学 | 6篇 |
力学 | 16篇 |
数学 | 22篇 |
物理学 | 236篇 |
出版年
2021年 | 12篇 |
2019年 | 16篇 |
2018年 | 16篇 |
2017年 | 9篇 |
2016年 | 12篇 |
2015年 | 11篇 |
2014年 | 10篇 |
2013年 | 37篇 |
2012年 | 37篇 |
2011年 | 34篇 |
2010年 | 25篇 |
2009年 | 17篇 |
2008年 | 46篇 |
2007年 | 52篇 |
2006年 | 56篇 |
2005年 | 38篇 |
2004年 | 31篇 |
2003年 | 33篇 |
2002年 | 36篇 |
2001年 | 28篇 |
2000年 | 27篇 |
1999年 | 20篇 |
1998年 | 12篇 |
1997年 | 13篇 |
1996年 | 10篇 |
1995年 | 11篇 |
1994年 | 10篇 |
1993年 | 13篇 |
1992年 | 16篇 |
1991年 | 9篇 |
1990年 | 22篇 |
1989年 | 14篇 |
1988年 | 18篇 |
1987年 | 15篇 |
1986年 | 20篇 |
1985年 | 14篇 |
1984年 | 22篇 |
1983年 | 12篇 |
1982年 | 15篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 10篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1973年 | 4篇 |
1971年 | 4篇 |
1968年 | 4篇 |
排序方式: 共有948条查询结果,搜索用时 62 毫秒
41.
Fujimoto C 《Electrophoresis》2001,22(7):1322-1329
Polymerized sodium 11-acrylamidoundecanoate (poly(Na 11-AAU)) was used as a pseudostationary phase (PSP) for micellar electrokinetic chromatography to separate uncharged compounds. The polymer PSP showed signifcantly different solute migration behaviors from conventional micelles including sodium dodecyl sulfate and poly (sodium 10-undecylenate), giving high separation efficiencies (>200000 theoretical plates/m). Linear solvation energy relationships were used to evaluate and characterize the chemical interactions that influence the retention behavior in the poly (Na 11-AAU) micellar system. It was found that the solute volume and solute hydrogen bond basicity mainly influenced the retention. The characteristic feature of the poly (Na 11-AAU) micellar system is that the micelle has a significantly higher capacity for dipole-dipole and dipole-induced dipole interactions as well as a slightly higher capacity for electron pair interactions than the aqueous phase. Due to its unique selectivity, the poly(Na 11-AAU) micellar system would become an attractive new option for selectivity optimization on methods development. 相似文献
42.
Michelin SE Oliveira HL Kroin T Soares LS Veiteinheimer E Luz CA Lima MF Fujimoto MM Lee MT 《The Journal of chemical physics》2005,122(9):094309
In this work, we present a theoretical study on elastic electron collisions from three isoelectronic free radicals (CNN, NCN, and CCO) in the low incident energy range. More specifically, calculated differential, integral, and momentum transfer cross sections are reported in the 1-30 eV energy range. Calculations are performed in the static-exchange and static-exchange-polarization levels. The iterative Schwinger variational method is used to solve the scattering equations. Our study reveals that the calculated cross sections for the three targets are significantly different at incident energies below 10 eV. Above that energy, a remarkable similarity among the calculated results is seen. 相似文献
43.
Hayashi A Fujimoto Y Ogawa Y Nakayama H Tsuhako M 《Journal of colloid and interface science》2005,283(1):57-63
Ammonium-ion-exchanged alpha-Zr(HPO(4))(2)H(2)O (alpha-ZrP) was obtained as a single phase with the interlayer distance of 9.4 A by the ion-exchange of proton with ammonium ion. The ammonium ion-exchanged alpha-ZrP could adsorb ill-smelling gases, such as formaldehyde and carboxylic acids (formic acid, acetic acid, propionic acid, and butyric acid). The adsorption amounts of carboxylic acids increased in the order, butyric acid相似文献
44.
M Miyauchi K Sasahara K Fujimoto I Kawamoto J Ide H Nakao 《Chemical & pharmaceutical bulletin》1989,37(9):2369-2374
The degradation kinetics of pivaloyloxymethyl (POM) esters of cephalosporins in phosphate buffer solution (pH 6-8) were investigated. The degradation of the starting delta 3 cephalosporin ester proceeded mainly via isomerization to the delta 2 ester and subsequent hydrolysis to the delta 2 acid. Hydrolysis to the delta 3 acid (the parent acid) was very slow. Analysis of the rate constants indicated that the isomerization rate k12 was approximately equal to the apparent degradation rate of the delta 3 ester kdeg, and slower than the hydrolysis rate of the delta 2 ester k24. The isomerization process to the delta 2 ester was found to be the rate-determining step in the degradation of cephalosporin esters. The substituent at the C-3 position of the cephalosporins affected the degradation kinetics. The degradation was accelerated by increase of pH, buffer concentration and added protein. 相似文献
45.
M Miyauchi H Kurihara K Fujimoto I Kawamoto J Ide H Nakao 《Chemical & pharmaceutical bulletin》1989,37(9):2375-2378
The effect of substituents at the C-3 position on the degradation kinetics of the pivaloyloxymethyl (POM) ester of delta 3 cephalosporin in phosphate buffer solution (pH 6-8) was investigated. In the degradation, the isomerization process to the delta 2 ester was the rate-determining step. In this study, the logarithm of the isomerization rate to the delta 2 ester (log k12) correlated with the carbon-13 nuclear magnetic resonance chemical shift difference value at C-3 and C-4 of the delta 3 ester (delta delta (4-3)). The energy level of the lowest unoccupied molecular orbital (LUMO) of the delta 3 esters also correlated with log k12. The electronic properties at the C-2 position had no effect on the isomerization reaction. On the other hand, the logarithm of the isomerization rate back to the delta 3 ester (log k21) correlated with the van der Waals volume (MV) of the 3-substituent. These results show that the substituent at the C-3 position influences mainly the electronic structure of the conjugated pi-bond system (C3 = C4 - C4 = O) and consequently affects the feasibility of isomerization to the delta 2 ester, i.e., the stability to degradation. 相似文献
46.
Kohara T Koyama T Fujimura M Tanaka H Maeda J Fujimoto T Yamamoto I Arita M 《Chemical & pharmaceutical bulletin》2002,50(6):818-821
The oxidation behavior of Y-931, a potent atypical antipsychotic drug, was compared with that of clozapine and olanzapine. In two enzymatic systems (horseradish peroxidase (HRP)/glutathione (GSH) and HRP/H(2)O(2)/GSH) which generate thiyl radicals, clozapine markedly strengthened the electron paramagnetic resonance (EPR) signal for the radical. Olanzapine, Y-931 and the major metabolites (compounds 1-3) had no or minimal effect on the intensity of this signal. In addition, the redox potential values for the three derivatives were in accord with the EPR spin trapping results. In toxicological experiments in human leukocytes, a concentration-dependent toxicity was observed when neutrophils were incubated with clozapine (1-10 micromol/l) and H(2)O(2) (1 mmol/l). However, Y-931 and olanzapine did not show remarkable toxicity under the conditions. 相似文献
47.
It is shown that NMR-linewidth measurements are useful to obtain information about the cross-linkage density and the average distance between the cross-links in vulcanized rubber. Inhomogeneous structure of the rubber phase in carbon-filled rubber is evidenced and the thickness of the rubber layer on carbon is evaluated at 50 Å. 相似文献
48.
K. M. Nowak T. Ohta T. Suganuma J. Fujimoto H. Mizoguchi A. Sumitani A. Endo 《Opto-Electronics Review》2013,21(4):345-354
It was shown both theoretically and experimentally that nanosecond order laser pulses at 10.6 micron wavelength were superior for driving the Sn plasma extreme ultraviolet (EUV) source for nano-lithography for the reasons of higher conversion efficiency, lower production of debris and higher average power levels obtainable in CO2 media without serious problems of beam distortions and nonlinear effects occurring in competing solid-state lasers at high intensities. The renewed interest in such pulse format, wavelength, repetition rates in excess of 50 kHz and average power levels in excess of 18 kiloWatt has sparked new opportunities for a matured multi-kiloWatt CO2 laser technology. The power demand of EUV source could be only satisfied by a Master-Oscillator-Power-Amplifier system configuration, leading to a development of a new type of hybrid pulsed CO2 laser employing a whole spectrum of CO2 technology, such as fast flow systems and diffusion-cooled planar waveguide lasers, and relatively recent quantum cascade lasers. In this paper we review briefly the history of relevant pulsed CO2 laser technology and the requirements for multi-kiloWatt CO2 laser, intended for the laser-produced plasma EUV source, and present our recent advances, such as novel solid-state seeded master oscillator and efficient multi-pass amplifiers built on planar waveguide CO2 lasers. 相似文献
49.
Susumu Takigawa Masanori Koshimizu Takio Noguchi Tsutomu Aida Seiichi Takami Tadafumi Adschiri Yutaka Fujimoto Akira Yoko Gimyeong Seong Takaaki Tomai Keisuke Asai 《Journal of Radioanalytical and Nuclear Chemistry》2017,314(2):611-615
We synthesized liquid scintillators incorporating ZrO2 nanoparticles for application in neutrinoless double beta decay experiments. ZrO2 nanoparticles of less than 10 nm in size were synthesized with sub- and supercritical hydrothermal methods. The Zr concentrations in the liquid scintillators were determined to be up to 1.4 wt% with inductively coupled plasma analysis, and the liquid scintillators were transparent to scintillation. These results indicate that these methods are applicable for the preparation of liquid scintillators for neutrinoless double beta decay experiments. 相似文献
50.
O. Brafman J. Poplawski E. Ehrenfreund Z. Vardeny J. Tanaka H. Fujimoto 《Molecular Crystals and Liquid Crystals》2013,570(1):363-366
Resonant Raman Scattering and doping induced IR absorption are explained in terms of amplitude modes of the 1-d gap. The RRS frequencies and relative intensities of the renormalized phonon lines at the various concentrations are readily obtained. 相似文献