全文获取类型
收费全文 | 1300篇 |
免费 | 22篇 |
国内免费 | 4篇 |
专业分类
化学 | 704篇 |
晶体学 | 20篇 |
力学 | 36篇 |
综合类 | 2篇 |
数学 | 36篇 |
物理学 | 528篇 |
出版年
2022年 | 8篇 |
2020年 | 13篇 |
2019年 | 12篇 |
2018年 | 6篇 |
2017年 | 7篇 |
2016年 | 18篇 |
2015年 | 15篇 |
2014年 | 16篇 |
2013年 | 58篇 |
2012年 | 47篇 |
2011年 | 80篇 |
2010年 | 53篇 |
2009年 | 46篇 |
2008年 | 82篇 |
2007年 | 82篇 |
2006年 | 97篇 |
2005年 | 74篇 |
2004年 | 62篇 |
2003年 | 51篇 |
2002年 | 46篇 |
2001年 | 32篇 |
2000年 | 28篇 |
1999年 | 15篇 |
1998年 | 11篇 |
1997年 | 13篇 |
1996年 | 12篇 |
1995年 | 15篇 |
1994年 | 27篇 |
1993年 | 20篇 |
1992年 | 31篇 |
1991年 | 10篇 |
1990年 | 21篇 |
1989年 | 22篇 |
1988年 | 16篇 |
1987年 | 11篇 |
1986年 | 18篇 |
1985年 | 22篇 |
1984年 | 11篇 |
1983年 | 8篇 |
1982年 | 9篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 10篇 |
1978年 | 11篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1969年 | 9篇 |
1968年 | 5篇 |
排序方式: 共有1326条查询结果,搜索用时 15 毫秒
971.
Ken‐ichi Shinohara Toshiki Aoki Takashi Kaneko 《Journal of polymer science. Part A, Polymer chemistry》2002,40(11):1689-1697
Three optically active phenylacetylene polymers with chiral bulky pinanyl groups, (?)‐poly[4‐(dimethylpinanylsilyl)phenylacetylene] [(?)‐poly(PSPA)], (+)‐poly{4‐[3‐(10‐pinanyl)tetramethyldisiloxy]phenylacethylene} [(+)‐poly(PDSPA)], and their copolymer [(?)‐copoly(PSPA/PDSPA)], were synthesized. We observed high chirality in the main‐chain chromophore of (?)‐poly(PSPA), due to the presence of a chiral helix, with circular dichroism spectroscopy. In contrast, (+)‐poly(PDSPA),with flexible SiOSi spacers between the chiral pinanyl group and the main chain, had lower chirality. (?)‐Poly(PSPA), with large circular dichroism signals, was prepared by polymerization with a rhodium catalyst and had a highly stereoregular main chain (high cis‐configuration percentage). However, (?)‐poly(PSPA) prepared with a tungsten catalyst had lower chirality and lower stereoregularity in the main chain. A membrane from (?)‐poly(PSPA) showed enantioselective permeability for tryptophan in an aqueous solution. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1689–1697, 2002 相似文献
972.
A successful cationic perfluoroalkylation of alkenes and alkadienes with RfI(Ph)OSO2CF3 was described. The reactivity of RfI(Ph)OSO3H was also examined. 相似文献
973.
Akikazu Matsumoto Kenichi Yamagishi Shuzo Aoki 《Journal of polymer science. Part A, Polymer chemistry》1994,32(5):917-928
Radical polymerizations of methyl methacrylate (MMA), styrene (St), and vinyl acetate (VAc) were carried out in the presence of a novel phenyl acrylate derivative bearing a hindered phenol moiety (HPA). It has been clarified that HPA acts as a retarder and inhibitor for the polymerizations of MMA and VAc, respectively, and that in the polymerization of St it behaves as a monomer to give a copolymer. These additive effects were interpreted in terms of intramolecular transfer of the phenolic hydrogen in competition with propagation of the HPA radical to monomers. © 1994 John Wiley & Sons, Inc. 相似文献
974.
K. Aoki S. Sakurai M. Murata T. Ito H. Terada K. Hiramatsu 《Colloid and polymer science》1984,262(6):470-476
When the solution of bovine serum albumin at pH 9 is incubated at 65 °C, new components 1' (modified monomer), 2 (dimer) and 3 (probably trimer) are formed. The isoelectric focusing indicated that the isoelectric points of components 1', 2 and 3 were pH 5.9.The hydrogen ion titration curve for the native albumin had well known abnormal steepness at pH near 4, but that for component 1' had no abnormal steepness. The titration curve for component 1' located right side of that for the native albumin.Circular dichroism measurements indicated that some unfolding occurred, when the native albumin was changed to component 1'. The contents of-helix were 74 and 52 % for the native albumin and for component 1', respectively. The contents of -structure were 19 and 23 % for the native albumin and for component 1', respectively. The wavelength of maximum intensity of tryptophan fluorescence shifted to lower wavelength, when the native albumin was changed to component 1'. This suggests that tryptophan residue(s) is transferred to a more hydrophobic environment.The hydrogen ion titration curves, circular dichroism and fluorescence measurements, all supported the possibility that the component 2 is formed by the dimerization of component 1'. Further, it has been found that component 2' (dimer impurity in commercial bovine serum albumin preparations) is formed by the direct dimerization of native bovine serum albumin without conformational change. 相似文献
975.
The enantioselective reaction of alpha-seleno carbanions derived from bis(phenylseleno)acetal and bis(2-pyridylseleno)acetal in the presence of bis(oxazoline)s with various electrophiles gave products with high enantioselectivity. The enantioselective reaction of alpha-lithio benzyl 2-pyridyl selenide gave the products with stereochemistry reverse to that obtained in the reaction of alpha-lithio benzyl phenyl selenide. Mechanistic investigation suggests the enantiodetermination of these reactions at -78 degrees C depends on dynamic thermodynamic resolution. The enantioselective reaction was applied to the preparation of enantioenriched olefins and epoxide. 相似文献
976.
Cassette dosing approach and quantitative structure-pharmacokinetic relationship study of antifungal N-myristoyltransferase inhibitors 总被引:1,自引:0,他引:1
977.
Mikata Y Wakamatsu M So H Abe Y Mikuriya M Fukui K Yano S 《Inorganic chemistry》2005,44(21):7268-7270
A new heptadentate N6-O1 ligand, N,N,N',N'-tetrakis(2-quinolylmethyl)-2-hydroxy-1,3-propanediamine (Htqhpn), was synthesized and used to generate compounds with linearly ordered MnIIMnIIIMnIIIMnII tetranuclear cores. This is the lowest valent tetranuclear manganese complex that exhibits a (mu2-O)2Mn2 core in the molecule. The electron paramagnetic resonance and magnetic measurements of these tetranuclear complexes suggest moderately strong antiferromagnetic coupling for the central MnIII2 core, with weak coupling between the MnII and MnIII centers. 相似文献
978.
Shuzo Aoki Yoshiyuki Harita Yoshiaki Tanaka Hiroshi Mandai Takayuki Otsu 《Journal of polymer science. Part A, Polymer chemistry》1968,6(9):2585-2590
The relative reactivities of α-monosubstituted cyclic ethers having rings of three to six members toward a cation were estimated from their copolymerizations with 3,3-bis-(chloromethyl)oxetane (M1) catalyzed by boron trifluoride etherate in methylene chloride at 0°C. It was found that the reactivity of these cyclic ethers was dominated by both the ring strain and the basicity. The following empirical equation was derived to represent the relative reactivity of cyclic ethers: log (1/r1) = ?0.086ΔRS ? 0.31ΔB + 0.57, where ΔRS and ΔB are constants, characteristic of ring strain and basicity of the cyclic ethers and determined from the differences in free energy of polymerization of the corresponding cycloalkanes and in basicity between M1 and M2 monomers, respectively. A good linear correlation was observed between the reactivities calculated from this equation and those obtained from the experiments. 相似文献
979.
The mutual solubilities of {xCH3CH2CH2CH2OH+(1-x)H2O} have been determined over the temperature range 302.95 to 397.75 K at pressures up to 2450 atm. An increase in temperature and pressure results in a contraction of the immiscibility region. The results obtained for the critical solution properties are: To(U.C.S.T.) = 397.85 K and xo = 0.110 at 1 atm; at p < 400 atm and at 800 atm < p < 2500 atm; . 相似文献
980.
Development of radioimmunoassay of intact laminin and its clinical evaluation as a tumor marker. 总被引:2,自引:0,他引:2
The concentration of laminin including laminin variants in serum samples was measured by a double-antibody radioimmunoassay using intact laminin. The mean level in 92 normal subjects (47 men and 45 women) was defined as 1 unit (U)/ml, and the cut-off value (2 S.D. above the mean) was 1.37 U/ml. Mean laminin level in 391 patients with various malignancies was 1.50 +/- 0.86 U/ml. Laminin levels were elevated in various cancer patients, and in 45.0% (176/391) the values exceeded the cut-off level; in patients with cancer of the stomach or pancreas, positivity rate exceeded 60%. Mean laminin concentration for 130 pregnant women (2.06 +/- 0.65 U/ml) was also significantly higher than that of normal controls, but concentrations for patients with various benign diseases were within a low range (0.55 +/- 0.29-1.10 +/- 0.29 U/ml). In the stomach or pancreas cancer patients, a positive correlation between laminin level and tumor progression or course of the disease was observed. These findings indicate that serum laminin level is potentially useful in the diagnosis and monitoring of certain cancers. 相似文献