全文获取类型
收费全文 | 498篇 |
免费 | 18篇 |
国内免费 | 1篇 |
专业分类
化学 | 391篇 |
晶体学 | 1篇 |
力学 | 6篇 |
数学 | 39篇 |
物理学 | 80篇 |
出版年
2023年 | 5篇 |
2022年 | 3篇 |
2021年 | 8篇 |
2020年 | 14篇 |
2019年 | 7篇 |
2018年 | 6篇 |
2017年 | 7篇 |
2016年 | 13篇 |
2015年 | 10篇 |
2014年 | 14篇 |
2013年 | 23篇 |
2012年 | 34篇 |
2011年 | 31篇 |
2010年 | 21篇 |
2009年 | 23篇 |
2008年 | 53篇 |
2007年 | 33篇 |
2006年 | 30篇 |
2005年 | 24篇 |
2004年 | 24篇 |
2003年 | 13篇 |
2002年 | 14篇 |
2001年 | 9篇 |
2000年 | 9篇 |
1999年 | 5篇 |
1998年 | 7篇 |
1997年 | 5篇 |
1996年 | 12篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 9篇 |
1984年 | 4篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有517条查询结果,搜索用时 937 毫秒
1.
V. A. Sadovnichy V. V. Alexandrov E. Soto T. B. Alexandrova T. G. Astakhova R. Vega N. V. Kulikovskaya V. I. Kurilov S. S. Migunov N. E. Shulenina 《Journal of Mathematical Sciences》2007,146(3):5938-5947
A mathematical model of the system composed of two sensors, the semicircular canal and the sacculus, is suggested. The model
is described by three lines of blocks, each line of which has the following structure: a biomechanical block, a mechanoelectrical
transduction mechanism, and a block describing the hair cell ionic currents and membrane potential dynamics. The response
of this system to various stimuli (head rotation under gravity and falling) is investigated. Identification of the model parameters
was done with the experimental data obtained for the axolotl (Ambystoma tigrinum) at the Institute of Physiology, Autonomous
University of Puebla, Mexico. Comparative analysis of the semicircular canal and sacculus membrane potentials is presented.
__________
Translated from Fundamentalnaya i Prikladnaya Matematika, Vol. 11, No. 7, pp. 207–220, 2005. 相似文献
2.
García F García JM García-Acosta B Martínez-Máñez R Sancenón F Soto J 《Chemical communications (Cambridge, England)》2005,(22):2790-2792
A sensory polymeric material for the colorimetric sensing of cyanide in water has been developed based on the reactivity of this anion with the pyrylium cation. 相似文献
3.
A rapid method of capillary zone electrophoresis is described to determine the oxidized (GSSG) and reduced (GSH) form of glutathione in plant tissue. In order to separate both analytes in a fused-silica capillary, the pH and composition of the electrolyte solution were optimized. The electrolyte composition was 100 mmol/L, borate 25 mmol/L Tris, and 0.2% w/v metaphosphoric acid (MPA), pH 8.2. Some instrumental conditions used to run the samples were hydrostatic injection for 30 s, 30 kV applied voltage, and UV detection (185 nm) at 25 degrees C. Linearity and useful range obtained for the calibration curves were optimum, with correlation coefficients about 0.999 in the 0-120 micromol/L range. The migration time was highly reproducible, less than 5 min being afforded to run a sample. Electrolyte buffer and samples required a careful pH control for optimal separation of both analytes. This aspect constitutes a critical analytical step when acids are used in the procedure for sample preparation. Simultaneous analysis of GSH and GSSG may provide a useful tool for comparative studies of plants in order to select those species with a potential capacity for detoxification from toxic elements or those appearing promising from phytoremediation for these elements. 相似文献
4.
5.
The photodissociation dynamics of nitromethane (CH(3)NO(2)) starting at the S(3) excited state has been studied at the complete active space self-consistent field level of theory in conjunction with atomic natural orbital type basis sets. In addition, the energies of all the critical points and the energy profiles connecting them have been recomputed with the multiconfigurational second-order perturbation method. It is found that the key step in the reaction mechanism is a radiationless decay through an S(3)S(2) conical intersection. The branching space spanned by the gradient difference and nonadiabatic coupling vectors of this crossing point comprises dissociation into excited nitromethane plus singlet atomic oxygen [CH(3)NO(1A")+O((1)D)] and S(3)-->S(2) deactivation, respectively. Furthermore, deactivated nitromethane S(n (n<3)) can decompose in subsequent steps into CH(3)+NO(2), where NO(2) is generated at least in two different electronic states (1 (2)B(2) and 1 (2)A(1)). It is shown that formation of excited nitric oxide NO(A (2)Sigma) arises from CH(3)NO(1A") generated in the previous step. In addition, four crossings between singlet and triplet states are localized; however, no evidence is found for a relevant role of such crossings in the photochemistry of CH(3)NO(2) initiated at S(3) state in the gas phase. 相似文献
6.
Carlos Seoane Jos L. Soto Pilar Zamorano Margarita Quinteiro 《Journal of heterocyclic chemistry》1981,18(2):309-314
Ring transformations of 4H-pyrans into pyridines are reported. Treatment of 2-amino-4,6-diaryl-3,5-dicyano-4H-pyrans (I) with nitrosylsulfuric acid brings about their transformation into 3,5-dicyano-4,6-diaryl-2-pyridones (VI) which can also be obtained from α-benzoylcinnamonitriles (IX) and cyanoacetamide. Similarly, 2-amino-4,6-diaryl-5-carbethoxy-3-cyano-4H-pyrans (II) lead to 4,6-diaryl-5-carbethoxy-3-cyano-2-pyridones (VII). Treatment of both series of pyrans with sulfuric acid results in the formation of the corresponding 3,4-dihydro-2-pyridones (IV and V). Reaction of pyrans II with ammonium acetate in acetic acid yields 2-amino-4,6-diaryl-5-carbethoxy-3-cyanopyridines (XII). Pyrans I undergo an entirely different type of reaction upon treatment with this reagent leading to 2,4,6-triaryl-3,5-dicyano-1,4-dihydropyridines (XV). 相似文献
7.
Ultra‐high pressure LC for astaxanthin determination in shrimp by‐products and active food packaging
A. Sanches‐Silva T. Ribeiro T. G. Albuquerque P. Paseiro R. Sendón A. Bernaldo de Quirós J. López‐Cervantes D. I. Sánchez‐Machado H. Soto Valdez I. Angulo G. P. Aurrekoetxea H. S. Costa 《Biomedical chromatography : BMC》2013,27(6):757-764
Nowadays, there is increasing interest in natural antioxidants from food by‐products. Astaxanthin is a potent antioxidant and one of the major carotenoids in crustaceans and salmonids. An ultra‐high pressure liquid chromatographic method was developed and validated for the determination of astaxanthin in shrimp by‐products, and its migration from new packaging materials to food simulants was also studied. The method uses an UPLC® BEH guard‐column (2.1 × 5 mm, 1.7 µm particle size) and an UPLC® BEH analytical column (2.1 × 50 mm, 1.7 µm particle size). Chromatographic separation was achieved using a programmed gradient mobile phase consisting of (A) acetonitrile–methanol (containing 0.05 m ammonium acetate)–dichloromethane (75:20:5, v/v/v) and (B) ultrapure water. This method was evaluated with respect to validation parameters such as linearity, precision, limit of detection, limit of quantification and recovery. Low‐density polyethylene films were prepared with different amounts of the lipid fraction of fermented shrimp waste by extrusion, and migration was evaluated into food simulants (isooctane and ethanol 95%, v/v). Migration was not detected under the tested conditions. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
8.
A method to generate NOON states with three photons by injecting photons in an array of three waveguides is presented. Conditional measurements project the wave function in a given (desired) state. In passing, it is shown how the array of three waveguides, that effectively reproduces the interaction of three fields, may be reduced to the interaction of two fields. 相似文献
9.
The batch emulsion copolymerization of vinyl acetate with different vinyl silane functional monomers (vinyl trimethoxysilane [VTMS], vinyl triethoxysilane [VTES], and vinyl silanetriol [VSTO]) is studied. The nature of the silane strongly affects the development of the microstructure and crosslinking ability of the latexes. A combination of techniques (Soxhlet extraction, centrifugation, assymetric‐flow field flow fractionation AF4/MALS/RI) shows that the factor controlling the molar mass and crosslinking density is the degree of hydrolysis of the alkoxysilane, producing higher molar masses and degrees of crosslinking when the degree of hydrolysis is high. Thus, the copolymer containing VSTO produced a very crosslinked latex, the one with VTMS produced a latex with a low degree of crosslinking in the wet state that can yield high degrees of crosslinking upon drying, and the latex with VTES do not produce significant amounts of crosslinking neither before nor after drying. 相似文献
10.
Sabine Kopec Emilio Martínez-Núñez Juan Soto Daniel Peláez 《International journal of quantum chemistry》2019,119(21):e26008
We present a generalization of the transition state search using chemical dynamics simulations (TSSCDS) methodology (discussed in a previous study) which allows the topographical characterization of intermolecular potential energy surfaces (IPES) for non-covalently bound complexes (vdW-TSSCDS). Starting from a single random input geometry, we show that vdW-TSSCDS is able to globally and automatically locate stationary points of an IPES, even in limiting cases such as extremely flat regions or nontrivial topologies (eg, bifurcation points). The basic idea is the expression of the connectivity matrix in block structure, where diagonal blocks correspond to the isolated fragments and off-diagonal blocks provide the intermolecular connectivity. To this end, we introduce a new definition of bound or not, in a non-covalent sense, utilizing an extra set of van der Waals distances, which encompasses all kinds of non-covalent distances. To discuss the use of the vdW-TSSCDS method, we present a series of 2-body van der Waals systems, namely, Ar-Benzene (3D), N2-Benzene (6D) and H2O-Benzene (9D). Finally, we further illustrate its capabilities by presenting some applications for n-body problems (n > 2), (H2O)2-Benzene (12D) and (H2O)3-Benzene (21D), as well as to a reactive, fully-flexible, system (Benzene-NO2)+ (39D) in which the simultaneous breaking/formation of both covalent and non-covalent interactions takes place. 相似文献