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131.
Lepzelter D Bates O Zaman M 《Langmuir : the ACS journal of surfaces and colloids》2012,28(12):5379-5386
Integrins are transmembrane proteins that allow cells to bind to their external environment. They are the primary regulators of cell-matrix interactions, with direct roles in cell motility and signaling, which in turn regulate numerous physiological processes. Under common experimental conditions, integrins tend to cluster for sturdy and effective binding to extracellular matrix molecules. These clusters often evolve into focal adhesions, which regulate downstream signaling. However, integrin clusters are more pronounced and have longer lifetimes in two-dimensional assays than in more realistic three-dimensional environments. While a number of models and theoretical approaches have focused on integrin binding and diffusion, the reasons for the differences between two- and three-dimensional clustering have remained elusive. In this study, we model an individual cluster attached to a two-dimensional collagen film and attached to collagen fibers of various sizes in three-dimensional matrices. We then discuss how our results explain differences in size and lifetime, and how they hint at reasons for other differences between the two environments. Further, we make predictions regarding the stability of clusters based on different overall intracellular conditions. Our results show good agreement with experiments and provide a quantitative basis for understanding how matrix dimensionality and structure regulate integrin behavior in environments that mimic in vivo conditions. 相似文献
132.
133.
Microwave‐assisted synthesis of disulfides using tetrathiomolybdate: A step toward greener synthesis
Naheed Sidiq Mohsin Ahmad Bhat Khaliquz Zaman Khan Mohammad Akbar Khuroo 《Heteroatom Chemistry》2012,23(4):373-376
An eco‐friendly, efficient, and rapid synthetic procedure for disulfides using benzyl triethyl ammonium tetrathiomolybdate through microwave irradiation of solid support adsorbed reactants is reported. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:373–376, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21025 相似文献
134.
Photoelectric charging experiments measure heterogeneous uptake coefficients for pyrene on model marine aerosol particles, including NaCl, NaNO(3), and MgCl(2). The analysis employs a multilayer kinetic model that contains adsorption and desorption rate constants for the bare aerosol surface and for pyrene-coated surfaces. First coating the aerosol particles with a pyrene layer and following the desorption using both t-DMA and photoelectric charging yields the desorption rate constants. Separate experiments monitor the increase in surface coverage of initially bare aerosol particles after exposure to pyrene vapor in a sliding-injector flow tube. Analyzing these data using the multilayer model constrained by the measured desorption rate constants yields the adsorption rate constants. The calculated initial heterogeneous uptake coefficient, γ(0)(295 K), is 1.1 × 10(-3) for NaCl, 6.6 × 10(-4) for NaNO(3), and 6.0 × 10(-4) for MgCl(2). The results suggest that a free energy barrier controls the uptake rate rather than kinematics. 相似文献
135.
The study focuses on elevated levels of environmental radioactivity present in heavy mineral deposits located along a 120-km coastal section of Cox's Bazar on the eastern panhandle of Bangladesh. The deposits are situated in or at sand dunes located on the recent beach (foredune area) or in attached paleo-beach areas (backdune area). This study investigates activity concentrations in bulk beach sands (six representative samples) and in five mineral fractions separated from the beach sands in order to assess potential radio-ecological effects and the possible use of the mineral deposits as a source for uranium and thorium. The bulk beach sands and individual mineral fractions were analysed by gamma-ray spectroscopy. The activity concentrations of U-238, U-235, Th-232 and K-40 in the bulk beach sand samples were found to be considerably high and positively correlated to the concentration of heavy minerals in the sand. In the mineral fractions, the highest activity concentrations were found in the zircon fraction followed by garnet, rutile, ilmenite and magnetite. The determination of (i) the radium activity, (ii) several radiation hazard indices and (iii) adsorbed and effective gamma doses allowed to assess the related exposure of the environment and the local population to elevated radioactivity. It becomes evident from the present data that (1) if raw sands or mineral fractions mined in the study area are used for building purposes or industrial use, their activity concentrations have to be considered from a radio-ecological perspective and (2) if mining and processing of the minerals is being considered, uranium and thorium may become strategically significant by-products. 相似文献
136.
The aim of this present paper is to construct exact solutions corresponding to the motion of magnetohydrodynamic (MHD) fluid
in the presence of Hall current, due to cosine and sine oscillations of a rigid plate as well as those induced by an oscillating
pressure gradient. A uniform magnetic field is applied transversely to the flow. By using Fourier sine transform steady state
and transient solutions are presented. These solutions satisfy the governing equations and all associated initial and boundary
conditions. The results for a hydrodynamic second grade fluid can be obtained as a limiting case when B
0 → 0 and for a Newtonian fluid when α
1 → 0. 相似文献
137.
This paper describes an experimental investigation of the statistical properties of turbulent velocity fluctuations in an axisymmetric jet. The focus is on those properties that are relevant to the prediction of noise. Measurements are performed using two single hot-wire anemometers as well as a two-component anemometer. Two-point cross correlations of the axial velocity fluctuations and of the fluctuations in the square of the axial velocity fluctuations are presented. Several reference locations in the jet are used including points on the jet lip and centerline. The scales of the turbulence and the convection velocity are determined, both in an overall sense as well as a function of frequency. The relationship between the second and fourth order correlations is developed and compared with the experimental data. The implications of the use of dimensional as well as non-dimensional correlations are considered. Finally, a comparison is made between the length scales deduced from the flow measurements and a RANS CFD calculation. 相似文献
138.
A number of important aromatic carboxylic acids precursors, or intermediates in the syntheses of natural products, are converted
into methyl esters and reduced to the corresponding primary alcohols using a sodium borohydride-THF-methanol system. The alcohols
are obtained in 70–92% yields in 2–5 hours, in a pure state. This two-step procedure not only provides a better alternative
to aluminum hydride reduction of acids but also allows the selective reduction of esters in presence of acids, amides, nitriles
or nitro functions which are not affected under these conditions. 相似文献
139.
Sungchul Yang Kwangsoo Kim Muhammad Zaman Haradhara Naik Guinyun Kim Tae-Yung Song Young-Ouk Lee Sung Gyun Shin Young-Uk Key Moo-Hyun Cho 《Journal of Radioanalytical and Nuclear Chemistry》2014,300(1):367-377
The independent isomeric yield ratios (IR) for the 139m,gNd and the 141m,gNd isomeric pairs produced from the natNd(γ, xn) reactions were determined by the activation and the off-line γ-ray spectrometric technique at the end-point bremsstrahlung energies of 45, 50, 55, and 60 MeV in the 100 MeV electron Linac of the Pohang accelerator laboratory, Korea. The present IR for the 141m,gNd isomeric pair were compared with those from the literature measured by the bremsstrahlung and the neutron to examine the role of excitation energy. The obtained IR for the 139m,gNd and the 141m,gNd isomeric pairs from natNd(γ, xn) reactions were compared with those from the 141Pr(p, x), the natCe(3He, x), and the 136Ce(α, n) reactions to examine the role of parameters in entrance channel i.e. excitation energy and the effect of the input angular momentum. The present IR of 139m,gNd and 141m,gNd were compared with those calculated by using the TALYS 1.4 code as well as those from the literature data of above mentioned reactions. 相似文献
140.
Mansoureh Tatari Guinyun Kim Haladhara Naik Abbas Hoseini Ranjbar Kwangsoo Kim Sung Chul Yang Muhammad Zaman Muhammad Sahid Sung Gyun Shin Yong Uk Kye Moo-Hyun Cho 《Journal of Radioanalytical and Nuclear Chemistry》2014,300(1):269-275
The isomeric yield ratios for the natAg(γ,xn)104m,g,106m,gAg reactions with the end-point bremsstrahlung energies of 45- and 55-MeV have been determined by the off-line γ-ray spectrometric technique using 100 MeV electron linac at Pohang accelerator laboratory, Korea. The present data were compared with literature data in comparable compound nucleus from the natAg(γ,xn), natPd(p,xn), and 103Rh(α,xn) reactions to examine the effects of an excitation energy and an input angular momentum. It is observed that the isomeric yield ratios of 104,106Ag in natAg(γ,xn), natPd(p,xn) and 103Rh(α,xn) reactions increase with the end-point bremsstrahlung energy, proton and alpha energy, which indicate the role of excitation energy. It is also found that for the similar compound nucleus at same excitation energy, the isomeric yield ratio of 104m,gAg is higher in the natPd(p,xn) and 103Rh(α,xn) reactions than those in natAg(γ,xn) reaction, which indicate the effect of an input angular momentum. 相似文献