全文获取类型
收费全文 | 827篇 |
免费 | 34篇 |
国内免费 | 6篇 |
专业分类
化学 | 600篇 |
晶体学 | 4篇 |
力学 | 15篇 |
数学 | 89篇 |
物理学 | 159篇 |
出版年
2023年 | 8篇 |
2022年 | 7篇 |
2021年 | 17篇 |
2020年 | 18篇 |
2019年 | 16篇 |
2018年 | 19篇 |
2017年 | 18篇 |
2016年 | 21篇 |
2015年 | 24篇 |
2014年 | 27篇 |
2013年 | 43篇 |
2012年 | 41篇 |
2011年 | 57篇 |
2010年 | 32篇 |
2009年 | 36篇 |
2008年 | 46篇 |
2007年 | 45篇 |
2006年 | 38篇 |
2005年 | 25篇 |
2004年 | 29篇 |
2003年 | 13篇 |
2002年 | 11篇 |
2001年 | 7篇 |
2000年 | 8篇 |
1999年 | 6篇 |
1998年 | 7篇 |
1997年 | 8篇 |
1996年 | 10篇 |
1995年 | 12篇 |
1994年 | 5篇 |
1993年 | 11篇 |
1992年 | 14篇 |
1991年 | 13篇 |
1990年 | 11篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1983年 | 5篇 |
1981年 | 8篇 |
1980年 | 11篇 |
1978年 | 6篇 |
1975年 | 5篇 |
1971年 | 4篇 |
1970年 | 5篇 |
1969年 | 7篇 |
1968年 | 7篇 |
1967年 | 4篇 |
1966年 | 5篇 |
排序方式: 共有867条查询结果,搜索用时 31 毫秒
81.
Signori AM Santos Kde O Eising R Albuquerque BL Giacomelli FC Domingos JB 《Langmuir : the ACS journal of surfaces and colloids》2010,26(22):17772-17779
A new and straightforward method for screening highly catalytically active silver nanoparticle-polymer composites derived from branched polyethyleneimine (PEI) is reported. The one-step systematic derivatization of the PEI scaffold with alkyl (butyl or octyl) and ethanolic groups led to a structural diversity correlated to the stabilization of silver nanoparticles and catalysis. Analysis of PEI derivative libraries identified a silver nanoparticle-polymer composite that was able to efficiently catalyze the p-nitrophenol reduction by NaBH(4) in water with a rate constant normalized to the surface area of the nanoparticles per unit volume (k(1)) of 0.57 s(-1) m(-2) L. Carried out in the presence of excess NaBH(4), the catalytic reaction was observed to follow pseudo-first-order kinetics and the apparent rate constant was linearly dependent on the total surface area of the silver nanoparticles (Ag-NPs), indicating that catalysis takes place on the surface of the nanoparticles. All reaction kinetics presented induction periods, which were dependent on the concentration of substrates, the total surface of the nanoparticles, and the polymer composition. All data indicated that this induction time is related to the resistance to substrate diffusion through the polymer support. Hydrophobic effects are also assumed to play an important role in the catalysis, through an increase in the local substrate concentration. 相似文献
82.
Aline Machado de Castro Kelly Cristina Nascimento Rodrigues Pedro Juliana Cunha da Cruz Marcela Costa Ferreira Selma Gomes Ferreira Leite Nei Pereira 《Applied biochemistry and biotechnology》2010,162(7):2111-2122
Sugarcane bagasse is an agroindustrial residue generated in large amounts in Brazil. This biomass can be used for the production
of cellulases, aiming at their use in second-generation processes for bioethanol production. Therefore, this work reports
the ability of a fungal strain, Trichoderma harzianum IOC-4038, to produce cellulases on a novel material, xylan free and cellulose rich, generated from sugarcane bagasse, named
partially delignified cellulignin. The extract produced by T. harzianum under submerged conditions reached 745, 97, and 559 U L−1 of β-glucosidase, FPase, and endoglucanase activities, respectively. The partial characterization of this enzyme complex
indicated, using a dual analysis, that the optimal pH values for the biocatalysis ranged from 4.9 to 5.2 and optimal temperatures
were between 47 and 54 °C, depending on the activity studied. Thermal stability analyses revealed no significant decrease
in activity at 37 °C during 23 h of incubation. When compared to model strains, Aspergillus niger ATCC-16404 and Trichoderma reesei RutC30, T. harzianum fermentation was faster and its extract showed a better balanced enzyme complex, with adequate characteristics for its application
in simultaneous saccharification and fermentation processes. 相似文献
83.
Aline Staub Sylvain Giraud Martial Saugy Serge Rudaz Jean‐Luc Veuthey Julie Schappler 《Electrophoresis》2010,31(2):388-395
CE is a powerful analytical tool used to separate intact biomolecules such as proteins. The coupling of CE with TOF/MS produces a very promising method that can be used to detect and identify proteins in different matrices. This paper describes an efficient, rapid, and simple CE‐ESI‐TOF/MS procedure for the analysis of endogenous human growth hormone and recombinant human growth hormone without sample preparation. Operational factors were optimized using an experimental design, and the method was successfully applied to distinguish human growth hormone and recombinant human growth hormone in unknown samples. 相似文献
84.
85.
Simone Göttlich Simon Hoher Patrick Schindler Veronika Schleper Alexander Verl 《Applied Mathematical Modelling》2014
In this paper a model comparison approach based on material flow systems is investigated that is divided into a microscopic and a macroscopic model scale. On the microscopic model scale particles are simulated using a model based on Newton dynamics borrowed from the engineering literature. Phenomenological observations lead to a hyperbolic partial differential equation on the macroscopic model scale. Suitable numerical algorithms are presented and both models are compared numerically and validated against real-data test settings. 相似文献
86.
87.
88.
89.
Ulrich Meier Christoph Van Wüllen Michael Schindler 《Journal of computational chemistry》1992,13(5):551-559
A direct method for the ab initio calculation of the magnetic susceptibility and chemical shielding tensors based on the individual gauge for localized molecular orbitals (IGLO) formalism is introduced. “Direct” in this context means we avoid storing the two-electron repulsion integrals in favor of recalculating them whenever necessary. In conjunction with the Direct-SCF package TURBOMOLE Direct IGLO (DIGLO) permits calculation of magnetic second-order properties for large molecules by minimizing peripheral disc storage requirements. The size of the molecules to be treated is limited only by the amount of CPU time available. The performance of DIGLO is demonstrated for some selected examples. 相似文献
90.