全文获取类型
收费全文 | 6910篇 |
免费 | 334篇 |
国内免费 | 14篇 |
专业分类
化学 | 5080篇 |
晶体学 | 63篇 |
力学 | 93篇 |
数学 | 1030篇 |
物理学 | 992篇 |
出版年
2023年 | 47篇 |
2022年 | 69篇 |
2021年 | 101篇 |
2020年 | 116篇 |
2019年 | 106篇 |
2018年 | 125篇 |
2017年 | 120篇 |
2016年 | 240篇 |
2015年 | 221篇 |
2014年 | 227篇 |
2013年 | 466篇 |
2012年 | 556篇 |
2011年 | 620篇 |
2010年 | 318篇 |
2009年 | 261篇 |
2008年 | 464篇 |
2007年 | 488篇 |
2006年 | 414篇 |
2005年 | 401篇 |
2004年 | 305篇 |
2003年 | 262篇 |
2002年 | 224篇 |
2001年 | 165篇 |
2000年 | 132篇 |
1999年 | 89篇 |
1998年 | 54篇 |
1997年 | 41篇 |
1996年 | 78篇 |
1995年 | 52篇 |
1994年 | 41篇 |
1993年 | 46篇 |
1992年 | 56篇 |
1991年 | 31篇 |
1990年 | 17篇 |
1989年 | 19篇 |
1988年 | 19篇 |
1987年 | 22篇 |
1986年 | 20篇 |
1985年 | 29篇 |
1984年 | 27篇 |
1983年 | 17篇 |
1982年 | 27篇 |
1981年 | 18篇 |
1980年 | 14篇 |
1979年 | 15篇 |
1978年 | 12篇 |
1977年 | 9篇 |
1976年 | 15篇 |
1974年 | 7篇 |
1973年 | 10篇 |
排序方式: 共有7258条查询结果,搜索用时 31 毫秒
981.
982.
In this article we study relations between groups and quantum error correcting codes. Groups of central type are used to construct quantum error correcting codes. Both stabilizer and Clifford codes can be derived from a construction involving this kind of groups. A more general construction of Clifford codes will be given and their correcting properties will be examined using group theoretical techniques. 相似文献
983.
Cándido Martín González 《代数通讯》2013,41(5):1903-1912
In this note we study associative dialgebras proving that the most interesting such structures arise precisely when the algebra is not semiprime. In fact the presence of some “perfection” property (simpleness, primitiveness, primeness, or semiprimeness) imply that the dialgebra comes from an associative algebra with both products ? and ? identified. We also describe the class of zero-cubed algebras and apply its study to that of dialgebras. Finally, we describe two-dimensional associative dialgebras. 相似文献
984.
985.
Flavia Bonomo Guillermo Durán Martín D. Safe Annegret K. Wagler 《Discrete Applied Mathematics》2013,161(13-14):1925-1942
A graph is balanced if its clique-matrix contains no edge–vertex incidence matrix of an odd chordless cycle as a submatrix. While a forbidden induced subgraph characterization of balanced graphs is known, there is no such characterization by minimal forbidden induced subgraphs. In this work, we provide minimal forbidden induced subgraph characterizations of balanced graphs restricted to graphs that belong to one of the following graph classes: complements of bipartite graphs, line graphs of multigraphs, and complements of line graphs of multigraphs. These characterizations lead to linear-time recognition algorithms for balanced graphs within the same three graph classes. 相似文献
986.
987.
In this article the frame-theoretic account of what is archimedean for order-algebraists, and semisimple for people who study commutative rings, deepens with the introduction of ${\mathcal{J}}$ -frames: compact normal frames that are join-generated by their saturated elements. Yosida frames are examples of these. In the category of ${\mathcal{J}}$ -frames with suitable skeletal morphisms, the strongly projectable frames are epicomplete, and thereby it is proved that the monoreflection in strongly projectable frames is the largest such. That is news, because it settles a problem that had occupied the first-named author for over five years. In compact normal Yosida frames the compact elements are saturated. When the reverse is true one gets the perfectly saturated frames: the frames of ideals Idl(E), when E is a compact regular frame. The assignment E?Idl(E) is then a functorial equivalence from compact regular frames to perfectly saturated frames, and the inverse equivalence is the saturation quotient. Inevitable are the Yosida covers (of a ${\mathcal{J}}$ -frame L): coherent, normal Yosida frames of the form Idl(F), with F ranging over certain bounded sublattices of the saturation SL of L. These Yosida frames cover L in the sense that each maps onto L densely and codensely. Modulo an equivalence, the Yosida covers of L form a poset with a top ${\mathcal{Y}} L$ , the latter being characterized as the only Yosida cover which is perfectly saturated. Viewed correctly, these Yosida covers provide, in a categorical setting, another (point-free) look at earlier accounts of coherent normal Yosida frames. 相似文献
988.
Paweł Berczyński Aleksandra Kładna Irena Kruk Teresa Piechowska Hassan Y. Aboul-Enein Oya Bozdağ-Dündar Meltem Ceylan-Unlusoy 《Journal of fluorescence》2013,23(6):1319-1327
The antioxidant properties of 11 new synthesized chromonyl-2,4-thiazolidinediones and chromonyl-2,4-imidazolidinediones (CBs) were investigated. The antioxidant activities and mechanisms of the CBs interaction with reactive oxygen species (ROS) were clarified using various in vitro antioxidant assay methods including superoxide anion radical ( $ \mathrm{O}\overline{{}_2^{\bullet }} $ ), hydroxyl radical (HO?), 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH?) scavenging activity and the iron (II)-ferrozine complex formation. The potassium superoxide/18-crown-6 ether dissolved in dimethylsulfoxide (DMSO) was applied as a source of superoxide anion radical. Hydroxyl radicals were produced in the Fenton-like reaction Fe(II)+H2O2. Chemiluminescence, spectrophotometry, and electron paramagnetic resonance (EPR) spectroscopy using 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) as spin trap were applied as the measurement techniques. The CBs examined that exhibited good free radical scavenging activity also showed strong total antioxidant power capacity. Possible mechanisms of antioxidation are proposed to explain the differences in the experimental results between the chromone derivatives with imidazolidine-2,4-dione ring and those with thiazolidine-2,4-dione ring. In conclusion, some of the new CBs are promising to be applied as inhibitors of free radicals. 相似文献
989.
Diana B. Muñiz-Márquez Guillermo C. Martínez-Ávila Jorge E. Wong-Paz Ruth Belmares-Cerda Raúl Rodríguez-Herrera Cristóbal N. Aguilar 《Ultrasonics sonochemistry》2013,20(5):1149-1154
Bay leaves (BL) (Laurus nobilis L., Family: Laureceae) are traditionally used to treat some symptoms of gastrointestinal problems, such as epigastric bloating, impaired digestion, eructing and flatulence. These biological properties are mainly attributed to its phenolic compounds. In this paper, ultrasound-assisted extraction of phenolic compounds from Laurus nobilis L. (Laureceae) was studied.Effects of several experimental factors, such as sonication time, solid/liquid ratio and concentration of solvent on extraction of phenolic compounds were evaluated through a randomized complete block design with factorial treatment arrangement (33). The best extraction conditions were: 1 g plant sample with 12 mL of 35% ethanol, for 40 min, obtaining a yield of phenolic compounds of 17.32 ± 1.52 mg g?1 of plant. In addition, free radical-scavenging potential of DPPH and lipid oxidation inhibition, by linoleic acid peroxidation of the selected extract was measured in order to evidence their antioxidant properties. Results indicated that high amounts of phenolic compounds can be extracted from L. nobilis by ultrasound-assisted extraction technology. 相似文献
990.
Etienne Plésiat Piero Decleva Fernando Martín 《Central European Journal of Physics》2013,11(9):1157-1162
We use an extension of the static-exchange density functional theory (DFT) method, previously reported in [E. Plésiat et al., Phys. Rev. A 2, 023409 (2012), E. Plésiat, P. Decleva, F. Martín, Phys. Chem. Chem. Phys. 31, 10853 (2012)], to evaluate vibrationally resolved (total and angular) K-shell photoelectron cross sections of methane. The calculated cross sections are in very good agreement with the existing experimental measurements at low photoelectron energies. We show that, in contrast with the rich interference patterns previously observed in molecular frame C(1s) photoelectron angular distributions of methane at both low and high photoelectron energy, no interference effects are observed in the calculated β parameters, even at high photon energies. 相似文献