全文获取类型
收费全文 | 1074篇 |
免费 | 31篇 |
国内免费 | 2篇 |
专业分类
化学 | 701篇 |
晶体学 | 5篇 |
力学 | 11篇 |
数学 | 67篇 |
物理学 | 323篇 |
出版年
2022年 | 8篇 |
2021年 | 10篇 |
2020年 | 10篇 |
2019年 | 11篇 |
2018年 | 6篇 |
2017年 | 10篇 |
2016年 | 26篇 |
2015年 | 20篇 |
2014年 | 22篇 |
2013年 | 54篇 |
2012年 | 48篇 |
2011年 | 73篇 |
2010年 | 42篇 |
2009年 | 34篇 |
2008年 | 65篇 |
2007年 | 59篇 |
2006年 | 67篇 |
2005年 | 64篇 |
2004年 | 39篇 |
2003年 | 32篇 |
2002年 | 34篇 |
2001年 | 15篇 |
2000年 | 23篇 |
1999年 | 20篇 |
1998年 | 14篇 |
1997年 | 12篇 |
1996年 | 16篇 |
1995年 | 11篇 |
1994年 | 15篇 |
1993年 | 15篇 |
1992年 | 24篇 |
1991年 | 14篇 |
1990年 | 21篇 |
1989年 | 17篇 |
1988年 | 14篇 |
1987年 | 18篇 |
1986年 | 15篇 |
1985年 | 16篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 8篇 |
1976年 | 4篇 |
1975年 | 5篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1914年 | 2篇 |
排序方式: 共有1107条查询结果,搜索用时 15 毫秒
91.
It has been found that unsolvated bis (diorganoamino) magnesium compounds react smoothly with carboxylic acids to give the corresponding carboxamides directly in good to excellent yields. 相似文献
92.
D.-X. Chen E. Pardo A. Sanchez 《Physica C: Superconductivity and its Applications》2010,470(9-10):444-450
The driving force on an Abrikosov vortex is calculated numerically from the London equation and involved energies for a vortex perpendicular to the screening current near the surface of a superconductor. Compared with previous analytical derivation of the total force, the partial magnetic, kinematic, and external forces are also obtained so that the nature of the driving force may be deeply discussed. It is shown that the force is neither a Lorentz force nor a Magnus force as often believed and that in order to get a correct result, the image effects and the work done by the applied field must be taken into account. A name of London force is suggested for the driving force. A deep understanding of the nature of the driving force on Abrikosov vortices may also be important in the study of vortex pinning and dynamics in type-II superconductors. 相似文献
93.
94.
A. Z. Hrynkiewicz R. Kmieć K. Tomala J. P. Sanchez J. M. Friedt 《Hyperfine Interactions》1986,28(1-4):1047-1050
Isomer shifts for119Sn and121Sb impurities in different metallic hosts are compared. In the frame of the Miedema and van der Woude model three contributions to the isomer shifts due to the charge transfer, electron density mismatch and volume adjustment are calculated. 相似文献
95.
The title reaction was studied in different water–cosolvent (methanol) mixtures. The results have been rationalized employing the Marcus–Hush treatment. To apply this treatment, the true, unimolecular, electron‐transfer rate constants (ket) were obtained from the experimentally measured rate constants after calculation of the equilibrium constant for the processes of formation of the encounter complex. This calculation was carried out using Eigen–Fuoss (EF) and exponential mean spherical (EMSA) approaches employing effective values of the solvent dielectric constant. These effective values were obtained from the measured association constants corresponding to other ion pairs. The results reveal that in these media there is an additional component of reorganization energy, absent in neat solvents. An explanation of the origin of this component is given. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 658–666, 2009 相似文献
96.
R. Arvai F. Toulgoat M. Médebielle B. Langlois F. Alloin J.Y. Sanchez 《Journal of fluorine chemistry》2008,129(10):1029-1035
Several aryl-containing ammonium sulfonates have been prepared either by cationic metathesis from the corresponding lithium sulfonates or from the corresponding sulfonic acids. The latter have been obtained by elution of an Amberlite resin with alcoholic solutions of the lithium sulfonates. These ammonium sulfonates exhibit interesting conductivities and thermal properties which allow them to be promising candidates as electrolytes for electricity storage. 相似文献
97.
J. Betzabe Gonzlez‐campos Evgen Prokhorov Gabriel Luna‐Brcenas A. Mendoza Galvn Isaac C. Sanchez Sergio M. Nuo Donlucas B. Garcia‐Gaitan Yuriy Kovalenko 《Journal of Polymer Science.Polymer Physics》2009,47(9):932-943
Relaxations in chitin have been investigated in the temperature range 298–523 K using impedance spectroscopy in the frequency range 10−1–108 Hz. The objective was to detect a glass‐transition temperature for this naturally occurring, semicrystalline polysaccharide. The impedance study was complemented with X‐ray diffraction, thermogravimetric, and differential scanning calorimetry measurements. Preliminary impedance data treatment includes the subtraction of the dc conductivity contribution, the exclusion of contact and interfacial polarization effects, and obtaining a condition of minimum moisture content for further analysis. When all these aspects are taken into account, two relaxations are clearly revealed in the impedance data. For the first time, evidence is presented for a relaxation process, which exhibits a non‐Arrhenius temperature dependence, in dry α‐chitin (∼0.1% moisture content), and likely represents the primary α‐relaxation. This evidence suggests a glass transition temperature for chitin of 335 ± 10 K estimated on the basis of the temperature dependence of the conductivity and of the relaxation time. A second relaxation in dry α‐chitin, not previously reported in the literature, is observed from 353 K to the onset of thermal degradation (∼483 K) and is identified as the σ‐relaxation often associated with proton mobility. It exhibits a normal Arrhenius‐type temperature dependence with activation energy of 113 ± 3 kJ/mol. The latter has not been previously reported in the literature. A high frequency secondary β‐relaxation is also observed with Arrhenius activation energy of 45 ± 1 kJ/mol. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 932–943, 2009 相似文献
98.
L. Calvo Blazquez J. Rodriguez Flores F. Vinagre Jara A. Sanchez Misiego 《Journal of Chemical Sciences》1989,101(5):415-419
The electroanalytical behaviour of orotic acid in cathodic processes has been studied in HClO4, at several pH values in Britton-Robinson buffers, using DPP and CV techniques.
Orotic acid undergoes three cathodic waves over the entire pH range considered. Optimum conditions for determination of orotic
acid using the DPP technique are also studied. 相似文献
99.
In situ ion beam sputter deposition and X‐ray photoelectron spectroscopy (XPS) of multiple thin layers under computer control for combinatorial materials synthesis 下载免费PDF全文
Thomas A. Wilson Anders J. Barlow Michael L. Foster Mariela Bravo Sanchez Jose F. Portoles Naoko Sano Peter J. Cumpson Ian W. Fletcher 《Surface and interface analysis : SIA》2017,49(1):18-24
Deposition of ultra‐thin layers under computer control is a frequent requirement in studies of novel sensors, materials screening, heterogeneous catalysis, the probing of band offsets near semiconductor junctions and many other applications. Often large‐area samples are produced by magnetron sputtering from multiple targets or by atomic layer deposition (ALD). Samples can then be transferred to an analytical chamber for checking by X‐ray photoelectron spectroscopy (XPS) or other surface‐sensitive spectroscopies. The ‘wafer‐scale’ nature of these tools is often greater than is required in combinatorial studies, where a few square centimetres or even millimetres of sample is sufficient for each composition to be tested. The large size leads to increased capital cost, problems of registration as samples are transferred between deposition and analysis, and often makes the use of precious metals as sputter targets prohibitively expensive. Instead we have modified a commercial sample block designed to perform angle‐resolved XPS in a commercial XPS instrument. This now allows ion‐beam sputter deposition from up to six different targets under complete computer control. Ion beam deposition is an attractive technology for depositing ultra‐thin layers of great purity under ultra‐high vacuum conditions, but is generally a very expensive technology. Our new sample block allows ion beam sputtering using the ion gun normally used for sputter depth‐profiling of samples, greatly reducing the cost and allowing deposition to be done (and checked by XPS) in situ in a single instrument. Precious metals are deposited cheaply and efficiently by ion‐beam sputtering from thin metal foils. Samples can then be removed, studied and exposed to reactants or surface treatments before being returned to the XPS to examine and quantify the effects. Copyright © 2016 The Authors Surface and Interface Analysis Published by John Wiley & Sons Ltd. 相似文献
100.
The behavior of single-degree-of-freedom systems possessing quadratic and cubic nonlinearities subject to parametric excitation is investigated. Both fundamental and principal parametric resonances are considered. A global bifurcation diagram in the excitation amplitude and excitation frequency domain is presented showing different possible stable steady-state solutions (attractors). Fractal basin maps for fundamental and principal parametric resonances when three attractors coexist are presented in color. An enlargement of one region of the map for principal parametric resonance reveals a Cantor-like set of fractal boundaries. For some cases, both periodic and chaotic attractors coexist. 相似文献