全文获取类型
收费全文 | 780篇 |
免费 | 27篇 |
国内免费 | 3篇 |
专业分类
化学 | 577篇 |
晶体学 | 8篇 |
力学 | 26篇 |
数学 | 67篇 |
物理学 | 132篇 |
出版年
2022年 | 4篇 |
2021年 | 7篇 |
2020年 | 9篇 |
2019年 | 11篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2016年 | 14篇 |
2015年 | 13篇 |
2014年 | 18篇 |
2013年 | 40篇 |
2012年 | 53篇 |
2011年 | 78篇 |
2010年 | 33篇 |
2009年 | 40篇 |
2008年 | 72篇 |
2007年 | 54篇 |
2006年 | 51篇 |
2005年 | 35篇 |
2004年 | 31篇 |
2003年 | 28篇 |
2002年 | 30篇 |
2001年 | 16篇 |
2000年 | 12篇 |
1999年 | 3篇 |
1998年 | 14篇 |
1997年 | 11篇 |
1996年 | 12篇 |
1995年 | 8篇 |
1994年 | 11篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1985年 | 9篇 |
1984年 | 4篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1968年 | 3篇 |
1940年 | 2篇 |
1919年 | 2篇 |
排序方式: 共有810条查询结果,搜索用时 15 毫秒
151.
Jordan BJ Cooke G Garety JF Pollier MA Kryvokhyzha N Bayir A Rabani G Rotello VM 《Chemical communications (Cambridge, England)》2007,(12):1248-1250
We report the synthesis of a water-soluble flavin polymer using ATRP, whereby the oligoethylene glycol backbone provides both a local hydrophobic environment and redox tuning of the flavin moiety typical of flavoenzyme prototypes. 相似文献
152.
Reaction of Tp*MoVSCl2 with a variety of phenols and thiols in the presence of triethylamine produces mononuclear, thiomolybdenyl complexes Tp*MoVSX2 [Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate; X = 2-(ethylthio)phenolate (etp), 2-(n-propyl)phenolate (pp), phenolate; X2 = benzene-1,2-dithiolate (bdt), 4-methylbenzene-1,2-dithiolate (tdt), benzene-1,2-diolate (cat)]. The complexes have been characterized by microanalysis, mass spectrometry, IR, EPR, and UV-visible spectroscopic data, and X-ray crystallography (for the etp, pp, bdt, and cat derivatives). The mononuclear, six-coordinate, distorted-octahedral Mo centers are coordinated by terminal sulfido (MoS = 2.123(1)-2.1368(8) A), tridentate facial Tp*, and monodentate or bidentate O/S-donor ligands. Multifrequency (S-, X-, Q-band) EPR spectra of the complexes and selected molybdenyl analogues were acquired at 130 K and 295 K and yielded a spin Hamiltonian of Cs symmetry or lower, with gzz < gyy < gxx < ge and Az'z' > Ax'x' approximately Ay'y', and a noncoincidence angle in the range of beta = 24-39 degrees . Multifrequency EPR, especially at S-band, was found to be particularly valuable in the unambiguous assignment of the spin Hamiltonian parameters in these low-symmetry complexes. The weaker pi-donor terminal sulfido ligand yields a smaller SOMO-LUMO gap and reduced g-values for the thiomolybdenyl complexes compared with molybdenyl analogues, supporting existing crystallographic and EPR data for an apically coordinated oxo group in the active site of xanthine oxidase. 相似文献
153.
Hennet L Pozdnyakova I Bytchkov A Price DL Greaves GN Wilding M Fearn S Martin CM Thiaudière D Bérar JF Boudet N Saboungi ML 《The Journal of chemical physics》2007,126(7):074906
The authors have studied the structural evolution of the fragile glass-forming liquid CaAl2O4 during supercooling from the stable liquid phase to the cold glass below Tg. The evolution is characterized by a sharpening of the first diffraction peak and a shortening of the average nearest-neighbor bond length around 1.25Tg, indicating an increase in the degree of both intermediate-range and short-range orders occurring close to the dynamical crossover temperature. The cooling curve developed a kink at this temperature, indicating a simultaneous change in thermodynamic properties. 相似文献
154.
Matthias Christandl Robert König Graeme Mitchison Renato Renner 《Communications in Mathematical Physics》2007,273(2):473-498
When n − k systems of an n-partite permutation-invariant state are traced out, the resulting state can be approximated by a convex combination of tensor
product states. This is the quantum de Finetti theorem. In this paper, we show that an upper bound on the trace distance of
this approximation is given by , where d is the dimension of the individual system, thereby improving previously known bounds. Our result follows from a more general
approximation theorem for representations of the unitary group. Consider a pure state that lies in the irreducible representation
of the unitary group U(d), for highest weights μ, ν and μ + ν. Let ξμ be the state obtained by tracing out U
ν. Then ξμ is close to a convex combination of the coherent states , where and is the highest weight vector in U
μ.
For the class of symmetric Werner states, which are invariant under both the permutation and unitary groups, we give a second
de Finetti-style theorem (our “half” theorem). It arises from a combinatorial formula for the distance of certain special
symmetric Werner states to states of fixed spectrum, making a connection to the recently defined shifted Schur functions [1].
This formula also provides us with useful examples that allow us to conclude that finite quantum de Finetti theorems (unlike
their classical counterparts) must depend on the dimension d. The last part of this paper analyses the structure of the set of symmetric Werner states and shows that the product states
in this set do not form a polytope in general. 相似文献
155.
Daniel S. Freed Gregory W. Moore Graeme Segal 《Communications in Mathematical Physics》2007,271(1):247-274
In the ordinary quantum Maxwell theory of a free electromagnetic field, formulated on a curved 3-manifold, we observe that
magnetic and electric fluxes cannot be simultaneously measured. This uncertainty principle reflects torsion: fluxes modulo
torsion can be simultaneously measured. We also develop the Hamilton theory of self-dual fields, noting that they are quantized
by Pontrjagin self-dual cohomology theories and that the quantum Hilbert space is -graded, so typically contains both bosonic and fermionic states. Significantly, these ideas apply to the Ramond-Ramond field
in string theory, showing that its K-theory class cannot be measured. 相似文献
156.
157.
Thomas R. Darling Thomas P. Davis Michael Fryd Alexei A. Gridnev David M. Haddleton Steven D. Ittel Robert R. Matheson Graeme Moad Ezio Rizzardo 《Journal of polymer science. Part A, Polymer chemistry》2000,38(10):1706-1708
Polymer chemistry textbooks (e.g., B. Vollmert, Polymer Chemistry, Springer‐Verlag: New York, 1973, p 37; G. Odian, Principles of Polymerization, 3rd ed., Wiley: New York, 1991, p 8; H. G. Elias, An Introduction to Polymer Science, VCH: Weinheim, 1997, p 51) classify polymerization reactions as chain, step, and living according to the dependence of their degree of polymerization (DP ) or molecular weight (M̄) on conversion. This article discusses the rationale for uniform terminology in living polymerization. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1706–1708, 2000 相似文献
158.
159.
Graeme J. Gainsford Tim Kemmitt 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(3):m136-m138
In the title compound, [Na4(C8H16BO4)4(C4H10O2)]n, there are two coordination types for the four independent Na+ cations: two Na+ cations bond to six diolate O atoms [Na—O = 2.305 (2)–2.609 (2) Å], while the other two are five‐coordinate via one 1,4‐butanediol [2.289 (2) and 2.349 (3) Å] and four diolate O atoms [2.295 (2)–2.408 (2) Å]. Corresponding to this, there are three‐ and four‐coordinate diolate O atoms, the latter bridging Na atoms. The 1,4‐butanediol molecules lie on inversion centres. The boron stereochemistry shows minor local perturbations from its usual tetrahedral state [B—O = 1.457 (4)–1.503 (4) Å]. The resulting polymer packs as sheets parallel to the (10) plane crosslinked by the butanediol molecules. The structure was solved using data from a multiple crystal. 相似文献
160.
Graeme J. Gainsford Tim Kemmitt 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(9):m417-m418
The title compound, [Na(C8H20BO4)]n, has twofold crystallographic symmetry, with the Na+ cations bound by four O atoms [Na—O = 2.251 (3) Å]. The tetraethoxyborate anion acts as a bridging ligand to form one‐dimensional polymers running along the twofold crystal axis. The crystal was treated as a racemic twin. 相似文献