全文获取类型
收费全文 | 936篇 |
免费 | 37篇 |
国内免费 | 2篇 |
专业分类
化学 | 722篇 |
晶体学 | 1篇 |
力学 | 31篇 |
数学 | 110篇 |
物理学 | 111篇 |
出版年
2024年 | 1篇 |
2023年 | 10篇 |
2022年 | 13篇 |
2021年 | 22篇 |
2020年 | 17篇 |
2019年 | 22篇 |
2018年 | 13篇 |
2017年 | 10篇 |
2016年 | 22篇 |
2015年 | 29篇 |
2014年 | 38篇 |
2013年 | 39篇 |
2012年 | 59篇 |
2011年 | 77篇 |
2010年 | 61篇 |
2009年 | 49篇 |
2008年 | 68篇 |
2007年 | 85篇 |
2006年 | 73篇 |
2005年 | 76篇 |
2004年 | 49篇 |
2003年 | 44篇 |
2002年 | 31篇 |
2001年 | 8篇 |
2000年 | 8篇 |
1999年 | 11篇 |
1998年 | 8篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 7篇 |
1991年 | 1篇 |
1987年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
排序方式: 共有975条查询结果,搜索用时 15 毫秒
71.
Vendeuvre C Bertoncini F Thiébaut D Martin M Hennion MC 《Journal of separation science》2005,28(11):1129-1136
Modeling the retention in comprehensive two-dimensional gas chromatography (GC x GC) was achieved using retention indices obtained in conventional GC. Predicted results were compared with experimental data obtained in the two-dimensional separation of a synthetic hydrocarbon mixture. This proved to be helpful in optimizing the operating conditions of GC x GC separation of a complex petroleum sample and in identifying chemical families. 相似文献
72.
73.
Fabrice P. L. Andrieux Colin Boxall Robin J. Taylor 《Journal of solution chemistry》2008,37(11):1511-1527
Studies of the thermodynamics of formation of the acetohydroxamatoiron(III) complexes were carried out in acidic media at
temperatures ranging from 293 to 323 K. Through the isolation of the unique UV–visible spectra of all three complexes, it
was possible to determine their formation constants and deduce enthalpies and entropies of formation as well as their molar
absorptivities. The enthalpies of formation of the mono-, bis- and trisacetohydroxamatoiron(III) complexes were found to be
−56.4, −17.09 and +19.74 kJ⋅mol−1, respectively. Following the determination of the enthalpy and entropy of formation of these complexes, speciation diagrams
were calculated for the complexes at temperatures ranging from 293 to 323 K. 相似文献
74.
We study a class of nonlinear regression models for scalar or vectorial response when the explanatory variable is a function. We introduce a consistent estimator of the parameters of models in this class when functions are evaluated at randomly chosen observation points. To cite this article: F. Rossi, B. Conan-Guez, C. R. Acad. Sci. Paris, Ser. I 340 (2005). 相似文献
75.
The difference in adsorption behavior between a conventional monomeric endcapped C18 stationary phase (3.43 micromol/m2) and an endcapped polymeric RP-Amide phase (3.31 micromol/m2) was investigated. The adsorption isotherms of four compounds (phenol, caffeine, sodium 2-naphthalene sulfonate, and propranololium chloride) were measured by frontal analysis (FA) and the degree of heterogeneity of each phase for each solute was characterized by their adsorption energy distributions (AED), derived using the Expectation-Maximization method. The results show that only certain analytes (phenol and 2-naphthalene sulfonate) are sensitive to the presence of the polar embedded amide groups within the RP phase. Their binding constants on the amide-bonded phase are significantly higher than on conventional RPLC phases. Furthermore, an additional type of adsorption sites was observed for these two compounds. However, these sites having a low density, their presence does not affect much the retention factors of the two analytes. On the other hand, the adsorption behavior of the other two analytes (caffeine and propranololium chloride) is almost unaffected by the presence of the amide group in the bonded layer. Strong selective interactions may explain these observations. For example, hydrogen-bond interactions between an analyte (e.g., phenol or naphthalene sulfonate) and the carbonyl group (acceptor) or the nitrogen (donor) of the amido-embedded group may take place. No such interactions may take place with either caffeine or the cation propranololium chloride. This study confirms the hypothesis that analytes have ready access to locations deep inside the bonded layer, where the amide groups are present. 相似文献
76.
Valentina Laghezza Masci Anna‐Rita Taddei Thomas Courant Ozgül Tezgel Fabrice Navarro Franco Giorgi Denis Mariolle Anna‐Maria Fausto Isabelle Texier 《Macromolecular bioscience》2019,19(5)
Curcumin‐loaded collagen cryostructurates have been devised for wound healing applications. Curcumin displays strong antioxidant, antiseptic, and anti‐inflammatory properties, while collagen is acknowledged for promoting cell adhesion, migration and differentiation. However, when curcumin is loaded directly into collagen hydrogels, it forms large molecular aggregates and clogs the matrix pores. A double‐encapsulation strategy is therefore developed by loading curcumin into lipid nanoparticles (LNP), and embedding these particles inside collagen scaffolds. The resulting collagen/LNP cryostructurates have an optimal fibrous structure with ≈100 µm average pore size for sustaining cell migration. Results show that collagen is structurally unaltered and that nanoparticles are homogeneously distributed amidst collagen fibers. Hydrogels soaked in saline buffer release about 20 to 30% of their nanoparticles content within 24 h, while achieved 100% release after 25 days. When exposed to NIH 3T3 fibroblasts, these hydrogels provide a satisfactory scaffold for cell interaction as early as 4 h after seeding, with no cytotoxic counter effect. These positive features make the collagen/lipid cryostructurates a promising material for further use in wound healing. 相似文献
77.
Rufat Agalarov Martin Byrdin Fabrice Rappaport Gaozhong Shen Donald A. Bryant Art Van Der Est John H. Golbeck 《Photochemistry and photobiology》2008,84(6):1371-1380
Continuous wave (CW) and transient electron paramagnetic resonance studies have implied that when PsaF is removed genetically, the double reduction of A1A is facile, the lifetime of A1A? is shorter and the ratio of fast to slow kinetic phases increases in PS I complexes isolated with Triton X‐100 (Van der Est, A., A. I. Valieva, Y. E. Kandrashkin, G. Shen, D. A. Bryant and J. H. Golbeck [2004] Biochemistry 43 , 1264–1275). Changes in the lifetimes of A1A? and A1B? are characteristic of mutants involving the quinone binding sites, but changes in the relative amplitudes of A1A? and A1B? are characteristic of mutants involving the primary electron acceptors, A0A and A0B. Here, we measured the fast and slow phases of electron transfer from A1B? and A1A? to FX in psaF and psaE psaF null mutants using time‐resolved CW and pump‐probe optical absorption spectroscopy. The lifetime of the fast kinetic phase was found to be unaltered, but the lifetime of the slow kinetic phase was shorter in the psaF null mutant and even more so in the psaE psaF null mutant. Concomitantly, the amplitude of the fast kinetic phase increased by a factor of 1.8 and 2.0 in the psaF and psaE psaF null mutants, respectively, at the expense of the slow kinetic phase. The change in ratio of the fast to slow kinetic phases is explained as either a redirection of electron transfer through A1B at the expense of A1A, or a shortening of the lifetime of A1A? to become identical to that of A1B?. The constant lifetime and the characteristics of the near‐UV spectrum of the fast kinetic phase favor the former explanation. A unified hypothesis is presented of a displacement of the A‐jk(1) α‐helix and switchback loop, which would weaken the H‐bond from Leu722 to A1A, accounting for the acceleration of the slow kinetic phase, as well as weaken the H‐bond from Tyr696 to A0A, accounting for the bias of electron transfer in favor of the PsaB branch of cofactors. 相似文献
78.
Fabrice Baudoin 《Journal of Functional Analysis》2008,254(2):301-317
The purpose of this work is to give a new and short proof of the Atiyah-Singer local index theorem for the Dirac operator on the spin bundle. This proof is obtained by using heat semigroups approximations based on the truncation of Brownian Chen series. 相似文献
79.
80.
Adeline Perro Fabrice Meunier Véronique Schmitt Serge Ravaine 《Colloids and surfaces. A, Physicochemical and engineering aspects》2009,332(1):57-62
For the first time, large amount of Janus silica particles as small as 100 nm in diameter were prepared through a simple method based on the elaboration of Pickering emulsions of wax-in-water. Controlling the kinetic stabilization of wax droplets allows the fabrication of gram-sized quantities of regular asymmetric inorganic particles with high yield. In fact, our method is based on a limited coalescence process, which allows one to predict the quantity of interface which is produced when working with a known mass of wax, and thus to be sure that all introduced silica particles are adsorbed on the wax surface. To this end, the hydrophilic surface of the silica particles was made partially hydrophobic by adsorbing a known amount of surfactant: cetyltrimethylammonium bromide (CTAB). Varying the concentration in surfactant results in tuning the penetration rate of the particles in the wax droplets, leading to various dimension of the modified area. The broken spherical symmetry of the particle surface was thereafter revealed by the selective adsorption of gold nanoparticles on the amino-modified surface. 相似文献