全文获取类型
收费全文 | 1130篇 |
免费 | 49篇 |
国内免费 | 4篇 |
专业分类
化学 | 806篇 |
晶体学 | 7篇 |
力学 | 19篇 |
数学 | 202篇 |
物理学 | 149篇 |
出版年
2023年 | 10篇 |
2022年 | 22篇 |
2021年 | 26篇 |
2020年 | 30篇 |
2019年 | 23篇 |
2018年 | 15篇 |
2017年 | 16篇 |
2016年 | 45篇 |
2015年 | 44篇 |
2014年 | 32篇 |
2013年 | 70篇 |
2012年 | 63篇 |
2011年 | 74篇 |
2010年 | 47篇 |
2009年 | 39篇 |
2008年 | 49篇 |
2007年 | 64篇 |
2006年 | 46篇 |
2005年 | 40篇 |
2004年 | 36篇 |
2003年 | 34篇 |
2002年 | 21篇 |
2001年 | 14篇 |
2000年 | 16篇 |
1999年 | 20篇 |
1998年 | 13篇 |
1997年 | 13篇 |
1996年 | 12篇 |
1995年 | 8篇 |
1994年 | 7篇 |
1993年 | 7篇 |
1992年 | 9篇 |
1990年 | 8篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1984年 | 5篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1973年 | 6篇 |
1937年 | 6篇 |
1934年 | 5篇 |
1933年 | 7篇 |
1932年 | 8篇 |
1930年 | 10篇 |
1918年 | 7篇 |
1917年 | 8篇 |
1916年 | 5篇 |
1915年 | 13篇 |
排序方式: 共有1183条查询结果,搜索用时 0 毫秒
1.
2.
Biosorption of Chromium(III) by Biomass of Seaweed Sargassum sp. in a Fixed-Bed Column 总被引:2,自引:0,他引:2
Eneida Sala Cossich Edson Antonio da Silva Célia Regina Granhen Tavares Lúcio Cardozo Filho Teresa Massako Kakuta Ravagnani 《Adsorption》2004,10(2):129-138
This work aimed at modeling chromium biosorption using the biomass of seaweed Sargassum sp. in a fixed-bed column. The mathematical model used was obtained from the mass balance of the component in the liquid phase and in the biosorbent material. The effects of both axial dispersion in the column and the resistance to mass transfer in the solid were considered for the solution of the partial differential equations of the model, using the Galerkin method on finite elements. To represent the equilibrium data of the batch system the Langmuir isotherm were used. The chromium ion adsorption capacity of the seaweed Sargassum sp., at a temperature of 30°C and pH 3.5, was 2.61 mmol/g. The model performance was evaluated from experimental data obtained at 30°C for flow rates of 2, 6 and 8 mL/min. The parameters of the model, mass transfer and axial dispersion coefficients, were adjusted from these experimental data. The model proved adequate to describe chromium biosorption dynamics in fixed-bed columns. 相似文献
3.
Regina S. Burachik Rafail N. Gasimov Nergiz A. Ismayilova C. Yalçin. Kaya 《Journal of Global Optimization》2006,34(1):55-78
We study convergence properties of a modified subgradient algorithm, applied to the dual problem defined by the sharp augmented
Lagrangian. The primal problem we consider is nonconvex and nondifferentiable, with equality constraints. We obtain primal
and dual convergence results, as well as a condition for existence of a dual solution. Using a practical selection of the
step-size parameters, we demonstrate the algorithm and its advantages on test problems, including an integer programming and
an optimal control problem.
*Partially Supported by 2003 UniSA ITEE Small Research Grant Ero2.
Supported by CAPES, Brazil, Grant No. 0664-02/2, during her visit to the School of Mathematics and Statistics, UniSA. 相似文献
4.
This study presents a method of adaptive identification of parameters describing Sugeno fuzzy inference system in presence of bounded disturbances while maintaining the readability and interpretability of the fuzzy model during and after identification. This method do not require any a priori knowledge of a bound on the disturbance and noise and of a bound on the unknown parameters values. The method can be used for the robust and adaptive identification of slowly time varying nonlinear systems using fuzzy inference systems. The suggested method was used to build a fuzzy expert system that approximates the functional relationship between physical fitness and some of the measurable physiological parameters by their real measurements and opinion (human-experiences) of a medical expert. 相似文献
5.
Tuoto C. V. Regina A. Nagy J. B. Nastro A. 《Journal of Thermal Analysis and Calorimetry》1998,54(3):891-899
DSC, TG and quadrupole mass spectrometer data concerning methylquinuclidinium iodide (MeQ1), dried precursor gel, and crystalline
levyne-type zeolite are discussed together with the thermal degradation of MeQ1 mixed with single inorganic components of
the gel.
It is shown that MeQ+ions play a role in the organization of the gel structure.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
Braulio Insuasty Fernando Fernandez Jairo Quiroga Rodolfo Moreno Roberto Martinez Enrique Angeles Ruban Gavito Regina H. S. De Almeida 《Journal of heterocyclic chemistry》1998,35(4):977-981
The reaction of 1,2-diaminobenzenes with substituted 1,2-dibenzoyl-1,2-dibromoethanes constitutes a convenient synthetic route to the hitherto 2-(p-R-benzoylmethylene)-3-(p-R-phenyl)-1H-quinoxalines. Structures of all products were elucidated by ir, 1H and 13C-nmr, mass spectra data. X-Ray crystallography data confirm assigned structures. 相似文献
7.
Th. Rubehn W. F. J. Müller R. Bassini M. Begemann-Blaich Th. Blaich A. Ferrero C. Groß G. Imme I. Iori G. J. Kunde W. D. Kunze V. Lindenstruth U. Lynen T. Möhlenkamp L. G. Moretto B. Ocker J. Pochodzalla G. Raciti S. Reito H. Sann A. Schüttauf W. Seidel V. Serfling W. Trautmann A. Trzcinski G. Verde A. Wörner E. Zude B. Zwieglinski 《Zeitschrift für Physik A Hadrons and Nuclei》1995,353(2):197-204
Electromagnetic fission of238U projectiles at E/A =600 and 1000 MeV was studied with the ALADIN spectrometer at the heavy-ion synchrotron SIS. Seven different targets (Be, C, Al, Cu, In, Au and U) were used. By considering only those fission events where the two charges added up to 92, most of the nuclear interactions were excluded. The nuclear contributions to the measured fission cross sections were determined by extrapolating from beryllium to the heavier targets with the concept of factorization. The obtained cross sections for electromagnetic fission are well reproduced by extended Weizsäcker-Williams calculations which include E1 and E2 excitations. The asymmetry of the fission fragments' charge distribution gives evidence for the excitation of the double giant-dipole resonance in uranium.Communicated by V. Metag 相似文献
8.
A. Weidinger J. Erxmeyer H. Glückler Ch. Niedermayer O. Laforsch J. Groß M. Mehring 《Hyperfine Interactions》1994,86(1):609-614
Hydrogenated YBa2Cu3O7 with [H]/cell=2.0 was studied by X-ray diffraction, SR and1H-NMR. For the first time, the hydride phase (16% larger c-axis) known from thin film experiments was seen in a bulk sample. A comparison of the SR and NMR results shows that the 15 mT site (2 MHz in SR) is the stable position for the proton and muon. The three other muon sites (4 MHz line and two exponentially decaying components) are metastable. 相似文献
9.
U. Groß P. Dietrich G. Engler D. Prescher J. Schulze K. Lunkwitz A. Ferse 《Journal of fluorine chemistry》1982,20(1):33-52
The present work studies the changes in polymer structure and the mechanism of the decomposition of polytetrafluoroethylene resin (PTFE) exposed to high energy radiation (electron beam). Spectroscopic and kinetic observations are used to interpret the degradation process. For the first time the decomposition of PTFE has been carried out on a preparative scale and new results obtained by analysing the degradation products. The radiation-induced degradation of PTFE is accompanied by thermal degradation under certain irradiation conditions. This is due to an increase in temperature of the polymer caused by retardation of highly accelerated electrons (heat accumulation effect).The kinetics are discussed in terms of the reactions and recombination of radicals produced by high-energy radiation both in the polymer melt and the polymer surface. These are related to the overall rate of decomposition.The primary radicals formed by decomposition of PTFE in an inert atmosphere (N2, Ar) react to produce perfluorinated alkanes and alkenes. In the presence of reactive gases the decomposition fragments originated will react rapidly; e.g. if oxygen is present in the reactive area the radicals form perflourinated peroxyl and oxyl radicals which finally stabilize themselves by CC-scission to perfluorocarbon acid fluorides and carbonyldifluorides. 相似文献
10.