全文获取类型
收费全文 | 2045篇 |
免费 | 40篇 |
国内免费 | 12篇 |
专业分类
化学 | 1482篇 |
晶体学 | 25篇 |
力学 | 29篇 |
数学 | 165篇 |
物理学 | 396篇 |
出版年
2023年 | 14篇 |
2022年 | 21篇 |
2021年 | 17篇 |
2020年 | 14篇 |
2019年 | 24篇 |
2018年 | 15篇 |
2017年 | 14篇 |
2016年 | 30篇 |
2015年 | 28篇 |
2014年 | 36篇 |
2013年 | 108篇 |
2012年 | 84篇 |
2011年 | 104篇 |
2010年 | 60篇 |
2009年 | 58篇 |
2008年 | 102篇 |
2007年 | 136篇 |
2006年 | 137篇 |
2005年 | 140篇 |
2004年 | 84篇 |
2003年 | 101篇 |
2002年 | 91篇 |
2001年 | 37篇 |
2000年 | 39篇 |
1999年 | 39篇 |
1998年 | 23篇 |
1997年 | 23篇 |
1996年 | 31篇 |
1995年 | 30篇 |
1994年 | 17篇 |
1993年 | 17篇 |
1992年 | 29篇 |
1991年 | 17篇 |
1990年 | 22篇 |
1989年 | 21篇 |
1988年 | 22篇 |
1987年 | 18篇 |
1986年 | 17篇 |
1985年 | 20篇 |
1984年 | 38篇 |
1983年 | 10篇 |
1982年 | 26篇 |
1981年 | 22篇 |
1980年 | 16篇 |
1979年 | 24篇 |
1978年 | 23篇 |
1977年 | 24篇 |
1976年 | 10篇 |
1974年 | 9篇 |
1973年 | 9篇 |
排序方式: 共有2097条查询结果,搜索用时 15 毫秒
71.
72.
Keiichi Kimura Akira Matsui Yoshiaki Inaki Kiichi Takemoto 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(8):1231-1241
Polymerization of acrylonitrile initiated by triazole-copper(II) complexes was studied in dimethylsulfoxide solution. It was found that the polymerization proceeds by a free radical mechanism; however, the complexes can hardly homopolymerize methyl methacrylate and styrene. Ability of the complexes to initiate polymerization seems to depend on the substituents of triazole, the sort of solvents, and the counterions of copper(n) salts. From the data of visible spectroscopy and the spin trapping, the initiation mechanism was discussed in terms of reduction of copper(II) followed by forming active species. 相似文献
73.
A Nafion film containing tris(2,2′-bipyridine)ruthenium(II) as a luminescence probe was applied to photodetection of oxygen in a gas by utilizing the luminescence quenching by dioxygen. The linear Stern-Volmer plots of the emission intensity with respect to the oxygen concentration allowed quantitative determination of the oxygen. From the emission decay studied by a single-photon counting method, it was concluded that the quenching of the excited state Ru complex by oxygen proceeds by a conventional dynamic mechanism. 相似文献
74.
75.
Prof. Dr. Masaichi Saito Tomoki Akiba Misumi Kaneko Toshiaki Kawamura Dr. Minori Abe Prof. Dr. Masahiko Hada Prof. Dr. Mao Minoura 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(50):16946-16953
Plumbacyclopentadienylidenes, in which the lead atoms have divalent states and are coordinated by THF, pyridine and N‐heterocyclic carbene, were synthesized and characterized. The THF‐ and pyridine‐stabilized compounds can be regarded as rare examples of hypervalent 10‐X‐4 species. The equilibrium between the THF adduct and the free plumbacyclopentadienylidene was evidenced by spectroscopic analysis and theoretical calculations. The THF adduct in benzene converted into a plumbylene dimer, where one of the lead centers is coordinated by THF and the other lead atom is coordinated by a divalent lead atom, the dimer gradually decomposing into spiroplumbole. The THF adduct unexpectedly reacted with trifluoroborane and trichlorogallane to afford fluoroborole and chlorogallole, which are the first examples of non‐annulated fluoroborole and gallole, respectively. 相似文献
76.
Summary The ion exchange selectivity of trivalent metal ions has been determined on titanium antimonate cation exchanger prepared by coprecipitation of antimony to titanium at different mole ratios. The selectivity sequence Al3+<Cr3+<Ga3+<In3+<Fe3+ was found for trivalent metal ions at an initial concentration of 10–4 mol dm–3 in nitric acid media. A high separation factor Ga/Al = KdGa/KdAl, 4.8×103, was observed for the Ga3+–Al3+ pair on titanium antimonate with an antimony to titanium ratio of 0.34. The effective separation of Ga3+ and In3+ from Al3+ was achieved using a 3 cm×0.5 cm i.d. column containing titanium antimonate with an antimony to titanium ratio of 0.34. 相似文献
77.
Jun TakayamaSeiko Fukuda Yoshiaki SugiharaAkihiko Ishii Juzo Nakayama 《Tetrahedron letters》2003,44(28):5159-5162
Hetero Diels-Alder reactions of 3,4-di-tert-butylthiophene 1-oxide (1) with thioaldehydes and thioketones take place exclusively, except the reaction with thiobenzophenone, at the syn-π-face of 1 with respect to the SO bond. The π-face selectivity was explained in terms of the extent of conformational changes of 1 that are brought about in the process to the transition states. 相似文献
78.
Nomoto A Mitsuoka H Ozeki H Kobuke Y 《Chemical communications (Cambridge, England)》2003,(9):1074-1075
Introducing a porphyrin bearing electron acceptor onto a self-assembled monolayer (SAM) using a supramolecular method to form a hetero-dimer increased the photocurrent value compared with using porphyrin without an electron acceptor. 相似文献
79.
Two-dimensional network formation of cardiac myocytes in agar microculture chip with 1480 nm infrared laser photo-thermal etching 总被引:1,自引:0,他引:1
We have developed a new method that enables agar microstructures to be used to cultivate cells and that allows cell network patterns to be controlled. The method makes use of non-contact three-dimensional photo-thermal etching with a 1480 nm infrared focused laser beam, which is strongly absorbed by water and agar gel, to form the shapes of agar microstructures. It allows microstructures to be easily formed in an agar layer within a few minutes, with cell-culture holes formed by the spot heating of a 100 mW laser and tunnels by the tracing of a 100 microm s(-1), 40 mW laser. We cultivated rat cardiac myocytes in adjacent microstructures and observed synchronized beating in them 90 min after they had made physical contact. Our results indicate that the system can make and use microstructures for cell-network cultivation in a minimal amount of time without any expensive microfabrication facilities or complicated procedures. 相似文献
80.
Porphyrin macrocycles composed of five and six units of m-gable imidazolylporphyrinatozinc (1-Zn) were synthesized by self-assembled cyclization followed by ring-closing metathesis linkings. Each porphyrin macrocycle was isolated by GPC chromatography, and their molecular weights were determined by MALDI-TOF mass spectroscopy. These structures represent mimics of light-harvesting complexes in photosynthetic bacteria. [structure: see text] 相似文献