全文获取类型
收费全文 | 484篇 |
免费 | 14篇 |
国内免费 | 1篇 |
专业分类
化学 | 389篇 |
晶体学 | 3篇 |
力学 | 11篇 |
数学 | 46篇 |
物理学 | 50篇 |
出版年
2023年 | 3篇 |
2022年 | 14篇 |
2021年 | 25篇 |
2020年 | 10篇 |
2019年 | 12篇 |
2018年 | 11篇 |
2017年 | 9篇 |
2016年 | 14篇 |
2015年 | 22篇 |
2014年 | 11篇 |
2013年 | 44篇 |
2012年 | 30篇 |
2011年 | 41篇 |
2010年 | 25篇 |
2009年 | 19篇 |
2008年 | 28篇 |
2007年 | 24篇 |
2006年 | 25篇 |
2005年 | 21篇 |
2004年 | 20篇 |
2003年 | 18篇 |
2002年 | 11篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 5篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 5篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1973年 | 1篇 |
排序方式: 共有499条查询结果,搜索用时 656 毫秒
71.
Mauro D. Santos Pedro Cunha Rui P. Queirós Liliana G. Fidalgo Ivonne Delgadillo 《高压研究》2013,33(4):452-459
Pressure treatments of 300 and 500?MPa during 15?min were found to change starch–water sorption (adsorption and desorption) isotherms and the hysteresis effect, particularly the 500?MPa. This last treatment shifted the adsorption/desorption isotherms downward, compared with non-treated starch and starch treated at 300?MPa. The observed hysteresis effect decreased with the increase in pressure level in the whole aw range, indicating that adsorption and desorption isotherms became closer. Guggenheim–Anderson–De Boer and Brunauer–Emmett–Teller model parameters Cb, Cg, K and Mm also showed changes caused by pressure, the latter being lower in the pressure-processed samples, thus indicating possible changes on microbial and (bio)chemical stabilities of pressure-processed food products containing starch. 相似文献
72.
73.
Zingaretti L Mariano Correa N Boscatto L Chiacchiera SM Durantini EN Bertolotti SG Rivarola CR Silber JJ 《Journal of colloid and interface science》2005,286(1):245-252
The distribution of different aliphatic and aromatic amines: n-butylamine (n-BA), isobutylamine (i-BA), tert-butylamine (t-BA), piperidine (PIP), N,N-dimethylaniline (DMA) and N-methylaniline (MA) in water/sodium 1,4-bis(2-ethylhexyl)sulfosuccinate(AOT)/n-hexane reverse micelles was investigated by steady-state fluorescence measurements. The partition constants were measured by an indirect method based on the effect that amine partitioning exert on the bimolecular rate of the reaction between a microphase incorporated fluorophore (Ru(bpy)2+(3)) and the quencher, (Fe(CN)3-(6)). For MA, that can act as a quencher of the fluorophore a direct method was used. The results show that primary amines have larger partition constants than the secondary ones. For tertiary amines the distribution constants were practically negligible. Laser flash photolysis experiments confirmed that tertiary amines, both aliphatic and aromatic, are not incorporated to the micellar pseudophase. The effect of the amine structure on the partition constant was analyzed through linear solvation free energy relationships (LSER) using solute parameters and compared with those obtained for alcohols. Hydrogen bond interactions with the AOT polar heads appear to be the main driving force for the distribution of amines between the organic and micellar pseudophases, whereas the size of the alkyl or aromatic group tends to hinder it. 相似文献
74.
trans-[PtCl2(Am)(pip-pip)] x HCl complexes, where Am = ammine, methylamine and dimethylamine, react with ubiquitin to form 1:1 covalent adducts. The platinum complexes bind exclusively to Met1 of ubiquitin forming trans-[PtCl(S-Met1-Ub)(Am)(pip-pip)] adducts. These adducts are reactive towards nucleophiles and react with deoxyguanosine (dGMP) to form the ternary trans-[Pt(dGMP)(S-Met1-Ub) (Am)(pip-pip)] complex which is stable in water and even in the presence of excess glutathione (GSH). Reaction of trans-[PtCl(S-Met1-Ub)(Am)(pip-pip)] with GSH resulted in the rapid formation of the ternary complex trans-[Pt(GS)(S-Met1-Ub)(Am)(pip-pip)] which was not stable and slowly lost the platinum moiety; after 7 days the platinum moiety was completely removed and the native ubiquitin was regenerated. 相似文献
75.
Afrodita Liliana Boldea 《Central European Journal of Physics》2010,8(6):995-1000
The paper presents a concrete study of the existence of generalized and potential symmetries for the 1+1 dimensional version
of the Rudenko-Robsman equation, an interesting fourth-order partial differential equation that describes the evolution of
nonlinear waves in a dispersive medium. As the main results, the existence of a two-parameter algebra of generalized symmetries
and of an infinite-dimensional algebra when potential symmetries are taken into account is proven. 相似文献
76.
Cherif Amrouche Philippe G. Ciarlet Liliana Gratie Srinivasan Kesavan 《Comptes Rendus Mathematique》2006,342(10):785-789
The classical Donati theorem is used for characterizing smooth matrix fields as linearized strain tensor fields. In this Note, we give several generalizations of this theorem, notably to matrix fields whose components are only in . We then show that our extensions of Donati's theorem allow to reformulate in a novel fashion linearized three-dimensional elasticity problems as quadratic minimization problems with the strains as the primary unknowns. To cite this article: C. Amrouche et al., C. R. Acad. Sci. Paris, Ser. I 342 (2006). 相似文献
77.
At present the design of the Lightning protection systems (LPS) for structures as stipulated in standards is based on the electro – geometrical method, which was initially used to protect power lines from lightning. A derivative of the electro-geometrical method is the rolling sphere method. This method together, with the protection angle method and mesh method are used almost in all lightning standards as the measure in installing the lightning protection systems of grounded structures. In the mesh method, the dimension of the cell size in different levels of protection is determined using the rolling sphere method. Since the rolling sphere method does not take into account the physics of the lightning attachment process there is a need to evaluate the validity of the stipulated value in standards of the minimum lightning current that can penetrate through the mesh in different levels of protection. In this paper, meshes of different sizes as stipulated in the lightning protection standards were tested for their ability to intercept lightning flashes using a lightning attachment model that takes into account the physics of connecting leaders on. The results are in reasonable agreement with the specifications given in the lightning protection standards. 相似文献
78.
We consider the problem of scheduling a set of independent tasks on multiple same-speed processors with planned shutdown times with the aim of minimizing the makespan. We give an LPT-based algorithm, LPTX, which yields a maximum completion time that is less than or equal to 3/2 the optimal maximum completion time or 3/2 the time that passes from the start of the schedule until the latest end of a downtime. For problems where the optimal schedule ends after the last downtime, and when the downtimes represent fixed jobs, the LPTX maximum completion time is within 3/2 of the optimal maximum completion time. In addition, we show that this result is asymptotically tight for the class of polynomial algorithms assuming that P≠NP. We also show that the bound obtained previously for a similar problem, when no more than half of the machines are shut down at the same time, for the LPT algorithm is asymptotically tight in the class of polynomial algorithms if P≠NP. 相似文献
79.
Kersten Jörn Velasco-Sevilla Liliana 《The European Physical Journal C - Particles and Fields》2013,73(4):1-13
We present the NLO SUSY-QCD corrections to the production of a pair of the lightest neutralinos plus one jet at the LHC, appearing as a monojet signature in combination with missing energy. We fully include all non-resonant diagrams, i.e. we do not assume that production and decay factorise. We derive a parameter point based on the p19MSSM which is compatible with current experimental bounds and show distributions based on missing transverse energy and jet observables. Our results are produced with the program GoSam Cullen et al. (Eur. Phys. J. C 72:1889, 2012) for automated one-loop calculations in combination with MadDipole/MadGraph for the real radiation part. 相似文献
80.
Robert Szczsny Tuan K. A. Hoang Liliana Dobrzaska Duncan H. Gregory 《Molecules (Basel, Switzerland)》2021,26(16)
Herein we describe an alternative strategy to achieve the preparation of nanoscale Cu3N. Copper(II) oxide/hydroxide nanopowder precursors were successfully fabricated by solution methods. Ammonolysis of the oxidic precursors can be achieved essentially pseudomorphically to produce either unsupported or supported nanoparticles of the nitride. Hence, Cu3N particles with diverse morphologies were synthesized from oxygen-containing precursors in two-step processes combining solvothermal and solid−gas ammonolysis stages. The single-phase hydroxochloride precursor, Cu2(OH)3Cl was prepared by solution-state synthesis from CuCl2·2H2O and urea, crystallising with the atacamite structure. Alternative precursors, CuO and Cu(OH)2, were obtained after subsequent treatment of Cu2(OH)3Cl with NaOH solution. Cu3N, in the form of micro- and nanorods, was the sole product formed from ammonolysis using either CuO or Cu(OH)2. Conversely, the ammonolysis of dicopper trihydroxide chloride resulted in two-phase mixtures of Cu3N and the monoamine, Cu(NH3)Cl under similar experimental conditions. Importantly, this pathway is applicable to afford composite materials by incorporating substrates or matrices that are resistant to ammoniation at relatively low temperatures (ca. 300 °C). We present preliminary evidence that Cu3N/SiO2 nanocomposites (up to ca. 5 wt.% Cu3N supported on SiO2) could be prepared from CuCl2·2H2O and urea starting materials following similar reaction steps. Evidence suggests that in this case Cu3N nanoparticles are confined within the porous SiO2 matrix. 相似文献