全文获取类型
收费全文 | 793篇 |
免费 | 17篇 |
国内免费 | 3篇 |
专业分类
化学 | 544篇 |
晶体学 | 7篇 |
力学 | 14篇 |
数学 | 143篇 |
物理学 | 105篇 |
出版年
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 12篇 |
2019年 | 5篇 |
2018年 | 6篇 |
2017年 | 7篇 |
2016年 | 16篇 |
2015年 | 21篇 |
2014年 | 17篇 |
2013年 | 44篇 |
2012年 | 52篇 |
2011年 | 36篇 |
2010年 | 24篇 |
2009年 | 30篇 |
2008年 | 32篇 |
2007年 | 47篇 |
2006年 | 45篇 |
2005年 | 31篇 |
2004年 | 29篇 |
2003年 | 35篇 |
2002年 | 30篇 |
2001年 | 12篇 |
2000年 | 21篇 |
1999年 | 14篇 |
1998年 | 13篇 |
1997年 | 14篇 |
1996年 | 11篇 |
1995年 | 15篇 |
1994年 | 11篇 |
1993年 | 13篇 |
1992年 | 14篇 |
1991年 | 9篇 |
1990年 | 3篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 9篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1982年 | 11篇 |
1981年 | 4篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1978年 | 11篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1975年 | 7篇 |
1974年 | 6篇 |
1973年 | 5篇 |
1966年 | 3篇 |
1947年 | 5篇 |
排序方式: 共有813条查询结果,搜索用时 15 毫秒
51.
Avik Khan Khanh Dang Vu Gregory Chauve Jean Bouchard Bernard Riedl Monique Lacroix 《Cellulose (London, England)》2014,21(5):3457-3468
Microfluidization, which is a high-pressure homogenization technique, was used to develop highly dispersed cellulose nanocrystal (CNC) reinforced chitosan based nanocomposite films. A three factor central composite design with five levels was designed to systematically optimize the microfluidization process. The three factors were the CNC content, the microfluidization pressure and the number of microfluidization cycles. Response surface methodology was used to obtain relationship between the mechanical properties of the nanocomposite films and the factors. Polynomial equations were generated based on the regression analysis of the factors and the predicted properties of the nanocomposite films were in good agreement with the experimental results. Microfluidization effectively reduced the CNC–chitosan aggregates and improved the mechanical properties of the nanocomposite films. Microscopic analysis of the microfluidized nanocomposite films revealed a 10–15 times reduction in the size of the aggregates compared to the non-microfluidized CNC/chitosan films and an increase in the root mean square surface roughness (Rq). 相似文献
52.
Dborah De Masi Juan M. Asensio Pier‐Francesco Fazzini Lise‐Marie Lacroix Bruno Chaudret 《Angewandte Chemie (International ed. in English)》2020,59(15):6187-6191
Induction heating of magnetic nanoparticles (NPs) is a method to activate heterogeneous catalytic reactions. It requires nano‐objects displaying high heating power and excellent catalytic activity. Here, using a surface engineering approach, bimetallic NPs are used for magnetically induced CO2 methanation, acting both as heating agent and catalyst. The organometallic synthesis of Fe30Ni70 NPs displaying high heating powers at low magnetic field amplitudes is described. The NPs are active but only slightly selective for CH4 after deposition on SiRAlOx owing to an iron‐rich shell (25 mL min?1, 25 mT, 300 kHz, conversion 71 %, methane selectivity 65 %). Proper surface engineering consisting of depositing a thin Ni layer leads to Fe30Ni70@Ni NPs displaying a very high activity for CO2 hydrogenation and a full selectivity. A quantitative yield in methane is obtained at low magnetic field and mild conditions (25 mL min?1, 19 mT, 300 kHz, conversion 100 %, methane selectivity 100 %). 相似文献
53.
54.
A simple collimating lens system was used to modify, at modest cost, a flame atomic absorption spectrophotometer for performing flameless atomic absorption spectrophotometry (f.a.a.s.) analysis with the Varian Model 63 Carbon Rod Atomizer. The source light was collimated into a 3-mm diameter beam which passed through the carbon tube and was focused by a second lens to work efficiently with the monochromator. The modified f.a.a.s. techniques extends the capability of the flame atomic absorption spectrophotometer to make possible analyses of trace elements. Good correlation of values for Zn, Fe, Cu, and Mn were obtained by use of the National Bureau of Standards Standard Reference Material Orchard Leaves. 相似文献
55.
The present paper deals with the modeling of a district boiler (city of La Rochelle, west coast of France), as part of the OptiEnR research project. This “multi-energy” boiler supplies domestic hot water and heats residential and public buildings, using mainly wood and sometimes fuel or gas if necessary. The OptiEnR research project focuses on optimizing the performance of the boiler. Its main objective is to minimize the use of fossil energy, stocking renewable energy during low-demand periods and using it when peak-demand is high. Because of both the complexity of the plant as a whole and the strong interactions between the sub-systems (the wood boiler, the gas-fuel oil boiler, the breaking pressure bottle, the cogeneration plant, the hot water distribution network), a modular approach has been proposed. According to what information is available, a combination of white, grey and black boxes (Hammerstein–Wiener models) has been used to carry out the modeling task. To answer for the lack of information, additional parameters were proposed and identified. The model has been first used in simulation during heating periods, with the aim of optimizing both the parameters of the boilers control systems and the use of wood, gas and fuel oil. Next, it will be used, when adding to the plant a thermal storage unit and implementing a model predictive controller, to improve its functioning, especially reducing the coverage rate of the fossil energy boiler. 相似文献
56.
C. Lacroix 《Solid State Communications》1985,54(11):991-994
Using an exact equivalence between the Kondo lattice with infinite J and the Hubbard model with infinite U, we show that the ground state of the Kondo lattice is non-magnetic for concentrations of conduction electrons close to 1, but there are still some magnetic regions even for J → ∞. 相似文献
57.
58.
59.
E.?Tomasi-GustafssonEmail author F.?Lacroix C.?Duterte G.?I.?Gakh 《The European Physical Journal A - Hadrons and Nuclei》2005,24(3):419-430
We perform a global analysis of the experimental data of the electromagnetic nucleon form factors, in space-like and time-like regions. We give the expressions of the observables in annihilation processes, such as p + ¯↦ℓ+ + ℓ-, ℓ = e or μ, in terms of form factors. We discuss some of the phenomenological models proposed in the literature for the space-like region, and consider their analytical continuation to the time-like region. After determining the parameters through a fit on the available data, we give predictions for the observables which will be experimentally accessible with large statistics, polarized annihilation reactions 相似文献
60.
Shevchenko A Carter J Fearick RW Förtsch SV Fujita H Fujita Y Kalmykov Y Lacroix D Lawrie JJ von Neumann-Cosel P Neveling R Ponomarev VY Richter A Sideras-Haddad E Smit FD Wambach J 《Physical review letters》2004,93(12):122501
Fine structure in the energy region of the isoscalar giant quadrupole resonance in nuclei is observed in high-resolution proton scattering experiments at iThemba LABS over a wide mass range. A novel method based on wavelet transforms is introduced for the extraction of scales characterizing the fine structure. A comparison with microscopic model calculations including two-particle two-hole (2p2h) degrees of freedom identifies the coupling to surface vibrations as the main source of the observed scales. A generic pattern is also found for the stochastic coupling to the background of the more complex states. 相似文献