全文获取类型
收费全文 | 614篇 |
免费 | 17篇 |
国内免费 | 2篇 |
专业分类
化学 | 426篇 |
晶体学 | 4篇 |
力学 | 10篇 |
数学 | 87篇 |
物理学 | 106篇 |
出版年
2023年 | 8篇 |
2022年 | 22篇 |
2021年 | 25篇 |
2020年 | 30篇 |
2019年 | 30篇 |
2018年 | 19篇 |
2017年 | 11篇 |
2016年 | 13篇 |
2015年 | 19篇 |
2014年 | 22篇 |
2013年 | 40篇 |
2012年 | 42篇 |
2011年 | 53篇 |
2010年 | 31篇 |
2009年 | 12篇 |
2008年 | 23篇 |
2007年 | 23篇 |
2006年 | 33篇 |
2005年 | 44篇 |
2004年 | 20篇 |
2003年 | 15篇 |
2002年 | 17篇 |
2001年 | 6篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 9篇 |
1997年 | 8篇 |
1996年 | 2篇 |
1995年 | 7篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1967年 | 1篇 |
1955年 | 1篇 |
1935年 | 1篇 |
1932年 | 1篇 |
排序方式: 共有633条查询结果,搜索用时 0 毫秒
131.
Adam R. Hill Pablo Cubillas James T. Gebbie-Rayet Mollie Trueman Nathan de Bruyn Zulaikha al Harthi Rachel J. S. Pooley Martin P. Attfield Vladislav A. Blatov Davide M. Proserpio Julian D. Gale Duncan Akporiaye Bjrnar Arstad Michael W. Anderson 《Chemical science》2021,12(3):1126
A Monte Carlo crystal growth simulation tool, CrystalGrower, is described which is able to simultaneously model both the crystal habit and nanoscopic surface topography of any crystal structure under conditions of variable supersaturation or at equilibrium. This tool has been developed in order to permit the rapid simulation of crystal surface maps generated by scanning probe microscopies in combination with overall crystal habit. As the simulation is based upon a coarse graining at the nanoscopic level features such as crystal rounding at low supersaturation or undersaturation conditions are also faithfully reproduced. CrystalGrower permits the incorporation of screw dislocations with arbitrary Burgers vectors and also the investigation of internal point defects in crystals. The effect of growth modifiers can be addressed by selective poisoning of specific growth sites. The tool is designed for those interested in understanding and controlling the outcome of crystal growth through a deeper comprehension of the key controlling experimental parameters.Generic in silico methodology – CrystalGrower – for simulating crystal habit and nanoscopic surface topology to determine crystallisation free energies. 相似文献
132.
133.
Jong-San Chang Do-Young Hong Vladislav P. Vislovskiy Sang-Eon Park 《Catalysis Surveys from Asia》2007,11(1-2):59-69
Utilization of carbon dioxide as a soft oxidant for the catalytic dehydrogenation of ethylbenzene (CO2-EBDH) has been recently attempted to explore a new technology for producing styrene selectively. This article summarizes
the results of our recent attempts to develop effective catalyst systems for the CO2-EBDH on the basis of alumina-supported vanadium oxide catalysts. Its initial activity and on-stream stability were essentially
improved by the introduction of antimony oxide as a promoter into the alumina-supported catalyst. Insertion of zirconium oxide
into alumina support substantially increased the catalytic activity. Modification of alumina with magnesium oxide yielded
an increase of catalyst stability of alumina-supported V–Sb oxide due to the coking suppression. Carbon dioxide has been confirmed
to play a beneficial role of selective oxidant in improving the catalytic performance through the oxidative pathway, avoiding
excessive reduction and maintaining desirable oxidation state of vanadium ion (V5+). The positive effect of carbon dioxide in dehydrogenation reactions of several alkylbenzenes such as 4-diethylbenzene, 4-ethyltoluene,
and iso- and n-propylbenzenes was also observed. Along with the easier redox cycle between fully oxidized and partially reduced vanadium
species, the optimal surface acidity of the catalyst is also responsible for achieving high activity and catalyst stability.
It is highlighted that supra-equilibrium EBDH conversions were obtained over alumina-supported V–Sb oxide catalyst in CO2-EBDH as compared with those in steam-EBDH in the absence of carbon dioxide. 相似文献
134.
Wall coating for capillary electrophoresis on microchips 总被引:2,自引:0,他引:2
Dolník V 《Electrophoresis》2004,25(21-22):3589-3601
This review article with 116 references describes recent developments in the preparation of wall coatings for capillary electrophoresis (CE) on a microchip. It deals with both dynamic and permanent coatings and concentrates on the most frequently used microchip materials including glass, poly(methyl methacrylate), poly(dimethyl siloxane), polycarbonate, and poly(ethylene terephthalate glycol). Characterization of the channel surface by measuring electroosmotic mobility and water contact angle of the surface is included as well. The utility of the microchips with coated channels is demonstrated by examples of CE separations on these chips. 相似文献
135.
The [Fe(II)(Cys)(4)](2-) site of rubredoxin from Clostridium pasteurianum (Rd(red)) has been studied by M?ssbauer spectroscopy in both purified protein and whole cells of Escherichia coli overproducing it. Excellent fits were obtained to an S = 2 spin Hamiltonian for D = 5.7(3) cm(-1), E/D = 0.25(2), delta = 0.70(3) mm/s, DeltaE(Q) = -3.25(2) mm/s, eta = 0.75(5), A(x) = -20.1(7) MHz, A(y) = -11.3(2) MHz, and A(z) = -33.4(14) MHz. These parameters were analyzed with crystal-field theory for the (5)D manifold of iron(II), revealing a d(z(2)) orbital ground state that is admixed by approximately 0.21 d(x(2) - y(2)). The spin-Hamiltonian parameters are consistent within the (5)D theory, apart from the zero-field splitting parameter, D. This problem was solved by extending the crystal-field treatment with spin-orbit coupling to spin-triplet d-d excited states of the iron. Theoretical estimates are given for the spin-triplet (D(T)) and spin-quintet contributions (D(Q)) to D based on excitation energies derived from time-dependent density functional theory, TD-DFT. The computational results were interpreted in terms of crystal-field theory, yielding the Racah parameters B = 682 cm(-1) and C = 2583 cm(-1). The theoretical analysis gives the relative magnitudes D(Q):D(T):D(ss) = 51%: 42%:7% (D(ss) originates from spin-spin interaction). The DFT analysis corroborates the pivotal role of the torsion angles (omega(i)) of the C-S(i) bonds in shaping the electronic structure of the iron(II) site. Rd(red) in overexpressing whole cells accounts for 60% of the M?ssbauer absorption. The Rd(red) spectra from whole cells are virtually identical to those of the purified protein. By using the theoretical omega dependence of the spin Hamiltonian parameters, the torsions for Rd(red) in whole cells and purified protein samples are estimated to be the same within 2 degrees. These findings establish M?ssbauer spectroscopy as a structural tool for investigating iron sites in whole cells. 相似文献
136.
Andrew G. Ogienko Elissa A. Ukraintseva Tatyana A. Chingina Vladislav Yu. Komarov Andrey Yu. Manakov 《Journal of inclusion phenomena and macrocyclic chemistry》2005,53(3-4):231-236
The phase diagram of the pyridine–iron(III) chloride system has been studied for the 223–423 K temperature and 0–56 mass-% concentration ranges using differential thermal analysis (DTA) and solubility techniques. A solid with the highest pyridine content formed in the system was found to be an already known clathrate compound, [FePy3Cl3]·Py. The clathrate melts incongruently at 346.9 ± 0.3 K with the destruction of the host complex: [FePy3Cl3]·Py(solid)=[FePy2Cl3](solid) + liquor. The thermal dissociation of the clathrate with the release of pyridine into the gaseous phase (TGA) occurs in a similar way: [FePy3Cl3]·Py(solid)=[FePy2Cl3](solid) + 2 Py(gas). Thermodynamic parameters of the clathrate dissociation have been determined from the dependence of the pyridine vapour pressure over the clathrate samples versus temperature (tensimetric method). The dependence experiences a change at 327 K indicating a polymorphous transformation occurring at this temperature. For the process ${1 \over 2}[\hbox{FePy}_{3}\hbox{Cl}_{3}]\cdot \hbox{Py}_{\rm (solid)} = {1 \over 2}[\hbox{FePy}_{2}\hbox{Cl}_{3}]_{\rm (solid)} + \hbox{Py}_{\rm (gas)}$ in the range 292–327 K, ΔH $^{0}_{298}$ =70.8 ± 0.8 kJ/mol, ΔS $^{0}_{298}$ =197 ± 3 J/(mol K), ΔG $^{0}_{298}$ =12.2 ± 0.1 kJ/mol; in the range 327–368 K, ΔH $^{0}_{298}$ =44.4 ± 1.3 kJ/mol, ΔS $^{0}_{298}$ =116 ± 4 J/(mol K), ΔG $^{0}_{298}$ =9.9 ± 0.3 kJ/mol. 相似文献
137.
Holba Vladislav Benko Ján Grančičová Ol'ga Vollárová Ol'ga 《Transition Metal Chemistry》1985,10(3):84-89
Summary The kinetics of oxidation of [Co(NH3)5(NCS)]2+ by peroxodisulphate and periodate were investigated at different ionic strengths, and at different temperatures and concentrations
of perchloric acid. Rate constants and activation parameters are also reported in mixed water-organic solvents. It was shown
that the acid-base equilibria involving S2O
8
−2
, and IO
4
−
ions are important in the reactions studied. Solvent effects on the oxidation are interpreted in terms of the solvation of
both the initial state and the activated complex. 相似文献
138.
Efremov D Kuznetsova T Doronin V Sadykov V 《The journal of physical chemistry. B》2005,109(15):7451-7459
The article discusses the properties of several model zirconium dioxide complexes (ZrO(2))(n)() intercalated into the interlayer space of montmorillonite clay. Grand canonical Monte Carlo simulation was used in a series of numerical experiments during analysis of the low-temperature nitrogen adsorption in the micropores thus generated. The goal of such experiments was to determine the geometrical parameters of introduced molecular complexes of different types inside micropores of various widths. The obtained information was used to characterize textural and structural properties of three pillared interlayer materials prepared by using pillaring species synthesized via aging of zirconyl chloride solutions containing as additives chlorides of Ca, Sr, or Ba. It was found that in the cases of Ba and Ca the interlayer micropores are filled with isolated tetramers (ZrO(2))(4). Meanwhile, the presence of Sr in the pillaring solution, most likely, favors the preservation of larger sheetlike complexes (ZrO(2))(8). 相似文献
139.
The formation of chlorinated phenols during the analysis of chromatographically pure polychloroalicyclic ketones by gas chromatography and gas chromatography-mass spectrometry was observed. Also in the mass spectra obtained by direct inlet, the presence of small amounts of chlorophenols was detected. The reasons of the formation of chlorophenols are discussed and qualitative and quantitative results obtained are interpreted. 相似文献
140.
This work addresses the analysis of an isotropic planarly layered waveguide consisting of an inhomogeneous core that is enclosed between two homogeneous layers forming the cladding. The analysis relies on an auxiliary one-dimensional spectral problem that is intimately linked with the scalar wave equation for planarly layered media. We construct the Green function of the waveguide as an expansion involving the eigenfunctions of the continuous and the discrete spectrum of the auxiliary problem. From the eigenvalues of the discrete spectrum, we calculate the allowed propagation constants of the guided modes. The Spectral Parameter Power Series (SPPS) method [Math. Method Appl. Sci. 2010;33: 459–468] leads us to analytic expressions for the eigenfunctions of the auxiliary problem in the form of power series of the spectral parameter. In addition, we obtain an SPPS representation for the dispersion relation without making any kind of approximation or discretisation to the core of the waveguide. The SPPS analysis here presented is well suited for its numerical implementation, since all these series can be truncated due to their uniform convergence. 相似文献