全文获取类型
收费全文 | 423篇 |
免费 | 3篇 |
国内免费 | 2篇 |
专业分类
化学 | 222篇 |
晶体学 | 1篇 |
力学 | 1篇 |
数学 | 52篇 |
物理学 | 152篇 |
出版年
2020年 | 8篇 |
2019年 | 4篇 |
2018年 | 10篇 |
2017年 | 22篇 |
2016年 | 18篇 |
2015年 | 50篇 |
2014年 | 6篇 |
2013年 | 22篇 |
2012年 | 9篇 |
2011年 | 6篇 |
2010年 | 3篇 |
2008年 | 6篇 |
2007年 | 8篇 |
2006年 | 5篇 |
2004年 | 15篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2001年 | 13篇 |
2000年 | 8篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 29篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 8篇 |
1992年 | 9篇 |
1991年 | 9篇 |
1990年 | 5篇 |
1989年 | 11篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1985年 | 8篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1975年 | 12篇 |
1973年 | 10篇 |
1971年 | 3篇 |
1968年 | 4篇 |
1965年 | 2篇 |
1962年 | 2篇 |
1944年 | 2篇 |
1935年 | 4篇 |
1917年 | 2篇 |
1887年 | 2篇 |
排序方式: 共有428条查询结果,搜索用时 15 毫秒
71.
72.
A simple “green synthesis” of noble metal nanoparticles by direct reaction between Dextran‐graft‐lactone copolymers and metal salts without the need to separately add reducing and stabilizing agents was carried out. The effects of the composition, molecular weights of copolymers and solvents on the characteristics of the nanoparticles were considered. The amphiphilic character of the copolymers seems to be an important factor in the results of the synthesis. According to the results, general correlations between experimental parameters of synthesis and characteristics of the obtained nanoparticles were established. Techniques such as, transmission electron microscopy, scanning electron microscopy, UV–visible spectroscopy, Zeta Potential, dynamic light scattering and Fourier transform Infrared Spectroscopy, were used for the characterization of the products. The results indicate the possibility of control of the characteristics of the nanostructured material. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
73.
74.
Katsman E. A. Berenblyum A. S. Danyushevsky V. Ya. Karpov V. M. Kuznetsov P. S. Leont´eva S. V. Flid V. R. 《Russian Chemical Bulletin》2018,67(12):2224-2229
Russian Chemical Bulletin - The kinetics of liquid-phase decarbonylation of stearic acid in n-dodecane on γ-Al2O3 supported nickel sulfide catalyst promoted with silver was experimentally... 相似文献
75.
L. V. Мikhal´chenko V. N. Leibzon M. Yu. Leonova V. P. Gultyai 《Russian Chemical Bulletin》2016,65(9):2216-2219
An effect of boric acid additives on oxidation of 2,4,6-trinitrotoluene (TNT) to 2,4,6-trinitrobenzoic acid (TNBA) with chromic anhydride in concentrated (96—100%) H2SO4 has been studied. In the presence of tetrahydrosulfatoboric acid HB(HSO4)4 formed in situ (up to 5 mol.%) or added as a preliminary prepared solution (up to 1 mol. %), TNT is selectively oxidized to TNBA in the yields up to 95—99%. The mechanism including formation of TNT dication as a key step of its oxidation at the methyl group has been suggested. 相似文献
76.
Tarasenkov A. N. Vasil´ev V. G. Buzin M. I. Getmanova E. V. Pak G. G. Kramarenko E. Yu. Muzafarov A. M. 《Russian Chemical Bulletin》2016,65(4):1086-1096
Russian Chemical Bulletin - The rheological properties of hyperbranched polycarbosilanes with butyl and decyl terminal groups and their sulfur-containing analogs were compared. The use of various... 相似文献
77.
L. A. Bulavin V. Ya. Gotsul´skii N. P. Malomuzh V. E. Chechko 《Russian Chemical Bulletin》2016,65(4):851-876
Regularities of equilibrium state establishment in dilute aqueous solutions of alcohols and the concentration and temperature dependences of the contraction, which is one of the simplest and important thermodynamic characteristics of solutions, were considered. The equilibrium state in aqueous solutions of the alcohols is established for days and even weeks after preparation. Such a slow relaxation process is directly related to the formation of the microheterogeneous state of the system and peculiarities of its time evolution. The character of the temperature and concentration dependences of the contraction is satisfactorily explained on the basis of the simplest virial equation of state assuming that its parameters are determined by the averaged potentials of intermolecular interaction. The physical nature of peculiar points of aqueous solutions of alcohols, i.e., intersection points of the contraction curves or points in the vicinity of which the intensity of molecular light scattering anomalously increases, was considered. The appearance of peculiar points depends on orientational correlations in water. The possibility of existence of peculiar points in other binary solutions is also discussed. 相似文献
78.
The classical fatigue limit is often an important characteristic in fatigue design regarding metallic material. The limit is usually obtained from a staircase test in combination with some assumption about the statistical distribution of the limit. This distribution can be of a normal, log-normal or of extreme value type and no particular physical argument gives favor to any specific distribution. This leads to a certain ambiguity in the evaluation of test results which forces the designer to introduce large safety factors. In order to find a physically based statistical distribution for use in staircase tests to determine the fatigue limit we present here a random model for the fatigue limit based on the following assumptions; (i) The square root area model according to Murakami and co-workers is valid, (ii) the randomness in the fatigue limit is induced by the randomness of the maximum defect size, (iii) the random maximum defect size has an extreme value distribution of Gumbel type. This leads to the fatigue limit distribution based on Gumbel (FLG), which is recommended to replace the normal distribution in the evaluation of staircase fatigue tests in case of hard materials. It turns out that the skewness of the resulting distribution depends on the coefficient of variation; with a normal-like non-skewed distribution at the coefficient of variation of five percent. 相似文献
79.
Two ternary miscible fluoro-polyimide blends have been identified. They are 6FDA-3,3′-6F-diamine/6FDA-4,4′- F - diamine/BTDA - 4,4′ - 6FDA blend and 6FDA - 3,3′ - 6F - diamine/6FDA - 4,4′ - 6F - diamine/ODPA - PMDA - 4,4′-6F-diamine blend (6FDA is 2,2′-bis(3,4′-dicarboxy- phenyl)hexafluoro propane dianhydride, 6F-diamine is 2,2′-bis(3-aminophenyl) hexafluoro propane). Their miscibility probably arises from the fact that their diamine parts have hexafluoro isopropylidene groups, their dianhydride parts have similar bond angle, space, rigidity and length. Several 6FDA-polyimides and PCTG 5445 (glycol-modified polycyclohexanedimethanolterephthalate) form- ing miscible blends have also been discovered. These surprising results suggest that hexafluoro-isopropylidene-group containing polyimides are quite intermolecular active and the 1,4-cyclohexane dimethanol component in PCTG 5445 may also offer unique miscibility capability. © 1997 John Wiley & Sons, Ltd. 相似文献
80.
Arthur Jaffe Christian D. Jäkel Roberto E. Martinez II 《Communications in Mathematical Physics》2014,329(1):1-28
We explore a framework for complex classical fields, appropriate for describing quantum field theories. Our fields are linear transformations on a Hilbert space, so they are more general than random variables for a probability measure. Our method generalizes Osterwalder and Schrader’s construction of Euclidean fields. We allow complex-valued classical fields in the case of quantum field theories that describe neutral particles. From an analytic point-of-view, the key to using our method is reflection positivity. We investigate conditions on the Fourier representation of the fields to ensure that reflection positivity holds. We also show how reflection positivity is preserved by various spacetime compactifications of ${\mathbb{R}^{d}}$ in different coordinate directions. 相似文献