全文获取类型
收费全文 | 1873篇 |
免费 | 42篇 |
国内免费 | 10篇 |
专业分类
化学 | 1416篇 |
晶体学 | 30篇 |
力学 | 20篇 |
综合类 | 1篇 |
数学 | 140篇 |
物理学 | 318篇 |
出版年
2021年 | 10篇 |
2020年 | 9篇 |
2019年 | 30篇 |
2018年 | 15篇 |
2017年 | 14篇 |
2016年 | 18篇 |
2015年 | 23篇 |
2014年 | 44篇 |
2013年 | 129篇 |
2012年 | 67篇 |
2011年 | 95篇 |
2010年 | 45篇 |
2009年 | 67篇 |
2008年 | 115篇 |
2007年 | 91篇 |
2006年 | 90篇 |
2005年 | 97篇 |
2004年 | 109篇 |
2003年 | 90篇 |
2002年 | 78篇 |
2001年 | 48篇 |
2000年 | 33篇 |
1999年 | 16篇 |
1998年 | 33篇 |
1997年 | 17篇 |
1996年 | 21篇 |
1995年 | 25篇 |
1994年 | 18篇 |
1993年 | 16篇 |
1992年 | 20篇 |
1991年 | 23篇 |
1990年 | 22篇 |
1989年 | 20篇 |
1988年 | 24篇 |
1987年 | 16篇 |
1986年 | 21篇 |
1985年 | 34篇 |
1984年 | 35篇 |
1983年 | 17篇 |
1982年 | 23篇 |
1981年 | 21篇 |
1980年 | 13篇 |
1979年 | 24篇 |
1978年 | 19篇 |
1977年 | 18篇 |
1976年 | 17篇 |
1975年 | 11篇 |
1974年 | 9篇 |
1969年 | 7篇 |
1967年 | 7篇 |
排序方式: 共有1925条查询结果,搜索用时 0 毫秒
951.
952.
The theory of gel point in real polymer solutions is examined with the empirical correlation between the reciprocal of the percolation threshold and the coordination number given by the percolation theory. Applying a larger value of the relative frequency of cyclization, an excellent agreement is obtained between the present theory and the percolation result. This suggest that while the ring distribution on lattices is similar to that in real systems, ring production is more frequent in the lattice model than in real systems. To confirm this conjecture, we derive the ring distribution function of the lattice model as a limiting case of d→∞, and show that the solution is in fact identical to the asymptotic formula of C→∞ in real systems except for the coefficient C, which has a maximum at d = 5, in support of the above conjecture. To examine the validity of the asymptotic solution for the lattice model, we apply it to the critical point problem of the percolation theory, showing that the solution works well in high dimensions greater than six. 相似文献
953.
Minoru Ota Hiroshi Sakurai Yoshiharu Sakurai 《Journal of Physics and Chemistry of Solids》2004,65(12):2065-2070
The magnetic Compton profiles (MCPs) of Fe thin film with 1 μm thickness have been successfully measured, using polyethylene terephtalate (PET) substrates with 4 μm thickness to reduce scattering photons from substrate.We have succeeded for the first time to observe the anisotropy of MCPs in the Co/Pd multilayer. The magnetic out-of-plane anisotropy of the current Co (0.8 nm)/Pd (1.6 nm) multilayer sample can be explained by the model of a large number of the |m|=1 states of 3d-bands. 相似文献
954.
955.
Osamu Sakurada Yasutake Kato Noriyoshi Kito Keiichi Kameyama Toshiaki Hattori Minoru Hashiba 《Analytical sciences》2004,20(2):311-314
Zirconium oxy-salts were hydrolyzed to form positively charged polymer or cluster species in acidic solutions. The zirconium hydrolyzed polymer was found to react with a negatively charged polyelectrolyte, such as poly(vinyl sulfate), and to form a stoichiometric polyion complex. Thus, colloidal titration with poly(vinyl sulfate) was applied to measure the zirconium concentration in an acidic solution by using a Toluidine Blue selective plasticized poly(vinyl chloride) membrane electrode as a potentiometric end-point detecting device. The determination could be performed with 1% of the relative standard deviation. The colloidal titration stoichiometry at pH < or = 2 was one mol of zirconium per equivalent mol of poly(vinyl sulfate). 相似文献
956.
The evaluation of a simple and rapid tristimulus colorimetric method for the determination of arsenic in brackish waters and its application to brackish water samples taken from brackish Lake Nakaumi are described. The determinations of arsenic in brackish water samples were made satisfactorily independent of sample salinity. By applying this method to lake water samples, the distributions and behaviors of arsenic in the lake and their controlling factors were clarified, such as seasonal variations of arsenic and the effect of a typhoon. 相似文献
957.
Kiyoharu Nakatani Jun Yamashita Tomomi Sekine Minoru Toriumi Toshiro Itani 《Analytical sciences》2003,19(5):775-777
The dissociation of t-butyl methacrylate-methacrylic acid copolymers in dimethyl sulfoxide was analyzed by a nonaqueous potentiometric titration technique. The negative logarithm of the dissociation constant of the monomer unit of a methacrylic acid (MAA) monotonously increased with the increasing degree of dissociation corresponding to the titrant/MAA amount ratio, and was highly influenced by the copolymerization ratio. The results are discussed in terms of the suppression of the dissociation of MAA by a neighboring charged methacrylate anion unit. 相似文献
958.
Miyabi Hiyama Hidefumi Akiyama Kenta Yamada Nobuaki Koga 《Photochemistry and photobiology》2014,90(1):35-44
Assignment of the fluorescence spectrum of firefly luciferin in aqueous solutions was achieved by utilizing not only emission energies but also theoretical absorption spectra and relative concentrations as estimated by pKa values. Calculated Gibbs free energies were utilized to estimate pKa values. These pKa values were then corrected by employing the experimental results. It was previously thought that the main peak near 550 nm observed in the experimental fluorescence spectra at all pH values corresponds to emission from the first excited state of the luciferin dianion [Ando et al. (2010) Jpn. J. Appl. Phys. 49, 117002–117008]. However, we found that the peak near 550 nm at low pH corresponds to emission from the first excited state of the phenolate monoanion of luciferin. Furthermore, we found that the causes of the red fluorescence at pH 1–2 are not only the emission from phenol monoanion but also the emission from the protonated species at nitrogen atom in the thiazoline ring of dianion. 相似文献
959.
Mari Akiyama 《Analytical and bioanalytical chemistry》2014,406(24):5805-5813
Inspection of patient-derived cells used in transplantation is non-invasive. Therefore, proteomics analysis using supernatants of cells cultured before transplantation is informative. In order to investigate the cell niche of bovine periosteal cells, supernatants of these cultured cells were subjected to 2-D electrophoresis followed by mass spectrometry, which identified type 1 collagen and the C-terminus of type 3 collagen. Only the C-terminal peptide from type 3 collagen was found in supernatants. It is known that type 3 collagen may be expressed intra- or extra-cellularly. Paraffin sections of the cultured cells were next examined by immunohistochemistry, which revealed that type 3 collagen regions besides the C-terminal peptide were present around the bovine periosteal cells but were not found in supernatants. Full-length type 3 collagen was closely associated with the cells, and only the C-terminal peptide was detectable in culture supernatants. Mass spectrometry analysis of partial peptide data combined with immunohistochemistry also indicated that uveal autoantigen with coiled coil domains and ankyrin repeats (UACA), exosome complex component RRP45 (EXOSC9), and thioredoxin-related transmembrane protein 2 (TMX2) were expressed in bovine periosteal cells. Results of this study indicate that analysis of culture supernatants before cell transplantation can provide useful biomarkers indicating the niche of cells used for transplantation. 相似文献
960.
Theoretical Study of Firefly Luciferin pKa Values—Relative Absorption Intensity in Aqueous Solutions
Miyabi Hiyama Hidefumi Akiyama Kenta Yamada Nobuaki Koga 《Photochemistry and photobiology》2013,89(3):571-578
Ground‐state vibrational analyses of firefly luciferin and its conjugate acids and bases are performed. The Gibbs free energies obtained from these analyses are used to estimate pKa values for phenolic hydroxy and carboxy groups and the N–H+ bond in the N‐protonated thiazoline or benzothiazole ring of firefly luciferin. The theoretical pKa values are corrected using the experimental values. The concentrations of these chemical species in solutions with different pH values are estimated from their corrected pKa values, and the pH dependence of their relative absorption intensities is elucidated. With the results obtained we assign the experimental spectra unequivocally. Especially, the small peak near 400 nm at pH 1–2 in experimental absorption spectra is clarified to be due to the excitation of carboxylate anion with N‐protonated thiazoline ring of firefly luciferin. Our results show that the pKa values of chemical species, which are contained in the aqueous solutions, are effective to assign experimental absorption spectra. 相似文献