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121.
In this paper, we provide a new insight to the previous work of Briys and de Varenne [E. Briys, F. de Varenne, Life insurance in a contingent claim framework: Pricing and regulatory implications, Geneva Papers on Risk and Insurance Theory 19 (1) (1994) 53–72], Grosen and Jørgensen [A. Grosen, P.L. Jørgensen, Life insurance liabilities at market value: An analysis of insolvency risk, bonus policy, and regulatory intervention rules in a barrier option framework, Journal of Risk and Insurance 69 (1) (2002) 63–91] and Chen and Suchanecki [A. Chen, M. Suchanecki, Default risk, bankruptcy procedures and the market value of life insurance liabilities, Insurance: Mathematics and Economics 40 (2007) 231–255]. We show that the particular risk management strategy followed by the insurance company can significantly change the risk exposure of the company, and that it should thus be taken into account by regulators. We first study how the regulator establishes regulation intervention levels in order to control for instance the default probability of the insurance company. This part of the analysis is based on a constant volatility. Given that the insurance company is informed of regulatory rules, we study how results can be significantly different when the insurance company follows a risk management strategy with non-constant volatilities. We thus highlight some limits of the prior literature and believe that the risk management strategy of the company should be taken into account in the estimation of the risk exposure as well as in that of the market value of liabilities. 相似文献
122.
Seven new depsipeptides, termed largamides A-G (1-7), and one new cyclic peptide, largamide H (8), have been isolated from the marine cyanobacterium Oscillatoria sp. Their structures were determined by NMR and ESI-MS techniques. The absolute configurations were assigned using LC-MS, chiral HPLC, and combined analysis of homonuclear and heteronuclear (2,3)J couplings, along with ROE data. Largamides, isolated from a single homogeneous cyanobacterial collection, represent three different structural classes of peptides. Largamides A-C (1-3) are characterized by the unusual occurrence of a senecioic acid unit, while largamides B (2) and C (3) possess in addition the rare 2-amino-5-(4'-hydroxyphenyl)pentanoic acid (Ahppa) and the novel 2-amino-6-(4'-hydroxyphenyl)hexanoic acid (Ahpha), respectively. Largamides D-G (4-7) are the first 3-amino-6-hydroxy-2-piperidone acid (Ahp)-containing depsipeptides reported with the rare Ahppa unit. Largamide H (8) is a unique cyclic peptide displaying a new 2,5-dihydroxylated beta-amino acid moiety, a methoxylated derivative of Ahppa, and two residues of the nonstandard 2,3-dehydro-2-aminobutanoic acid (Dab). Largamides D-G (4-7) inhibited chymotrypsin with IC(50) values ranging between 4 and 25 microM. 相似文献
123.
Surface tailoring for controlled protein adsorption: effect of topography at the nanometer scale and chemistry 总被引:1,自引:0,他引:1
Protein adsorption behavior is at the heart of many of today's research fields including biotechnology and materials science. With understanding of protein-surface interactions, control over the conformation and orientation of immobilized species may ultimately allow tailor-made surfaces to be generated. In this contribution protein-surface interactions have been examined with particular focus on surface curvature with and without surface chemistry effects. Silica spheres with diameters in the range 15-165 nm with both hydrophilic and hydrophobic surface chemistries have been used as model substrates. Two proteins differing in size and shape, bovine serum albumin (BSA) and bovine fibrinogen (Fg), have been used in model studies of protein binding with detailed secondary structure analysis being performed using infrared spectroscopy (IR) on surface-bound proteins. Although trends in binding affinity and saturation values were similar for both proteins, albumin is increasingly less ordered on larger substrates, while fibrinogen, in contrast, loses secondary structure to a greater extent when adsorbing onto particles with high surface curvature. These effects are compounded by surface chemistry, with both proteins becoming more denatured on hydrophobic surfaces. Both surface chemistry and topography play key roles in determining the structure of the bound proteins. A model of the binding characteristics of these two proteins onto surfaces having differing curvature and chemistry is presented. We propose that properties of an adsorbed protein layer may be guided through careful consideration of surface structure, allowing the fabrication of materials/surface coatings with tailored bioactivity. 相似文献
124.
McGuiness CL Shaporenko A Mars CK Uppili S Zharnikov M Allara DL 《Journal of the American Chemical Society》2006,128(15):5231-5243
Through rigorous control of preparation conditions, organized monolayers with a highly reproducible structure can be formed by solution self-assembly of octadecanethiol on GaAs (001) at ambient temperature. A combination of characterization probes reveal a structure with conformationally ordered alkyl chains tilted on average at 14 +/- 1 degrees from the surface normal with a 43 +/- 5 degrees twist, a highly oleophobic and hydrophobic ambient surface, and direct S-GaAs attachment. Analysis of the tilt angle and film thickness data shows a significant mismatch of the average adsorbate molecule spacings with the spacings of an intrinsic GaAs(001) surface lattice. The monolayers are stable up to approximately 100 degrees C and exhibit an overall thermal stability which is lower than that of the same monolayers on Au[111] surfaces. A two-step solution assembly process is observed: rapid adsorption of molecules over the first several hours to form disordered structures with molecules lying close to the substrate surface, followed by a slow densification and asymptotic approach to final ordering. This process, while similar to the assembly of alkanethiols on Au[111], is nearly 2 orders of magnitude slower. Finally, despite differences in assembly rates and the thermal stability, exchange experiments with isotopically tagged molecules show that the octadecanethiol on GaAs(001) monolayers undergo exchange with solute thiol molecules at roughly the same rate as the corresponding exchanges of the same monolayers on Au[111]. 相似文献
125.
Carole Vincelet Jean Marc Roussel David Benanou 《Analytical and bioanalytical chemistry》2010,396(6):2285-2292
Membrane-assisted solvent extraction was applied for the determination of different classes of compounds in water, having
K
o/w (octanol–water partition coefficient) values between 101 (aniline) and 108 (methyl stearate), by means of experimental designs. Four solvents were investigated—propan-2-ol, ethyl acetate, diisopropyl
ether and cyclohexane—as well as extraction time, temperature, salt impact, pH and methanol addition. The best choice was
diisopropyl ether, 50 °C, 30 min and an addition of 3 g of sodium chloride at pH 2 for polar compounds. The relative standard
deviation (n = 3) was found in the range from 5 to 17%. Recoveries ranged between 34 and 100%. Membrane-assisted solvent extraction was
successfully applied to a fast screening method dedicated to an unknown wastewater sample. 相似文献
126.
Christian Chapuis Carole Cantatore Peter Fankhauser René Challand Jean‐Jacques Riedhauser 《Helvetica chimica acta》2009,92(9):1782-1799
The synthesis of various D‐labeled perfume ingredients (orris‐like, sandalwood‐like, musky, and amber‐like) is presented. These substances, possessing practically identical H2O/solid and solid/gas partition coefficients as their unlabeled analogues, are used as internal standards for the validation of a new analytical GC/MS method for the determination of low residual concentrations in H2O after biodegradability tests. 相似文献
127.
Xavier Colin Emmanuel Richaud Jacques Verdu Carole Monchy-Leroy 《Radiation Physics and Chemistry》2010,79(3):365-370
A non-empirical kinetic model has been built for describing the general trends of radiooxidation kinetics of ethylene–propylene copolymers (EPR) at low γ dose rate and low temperature. It is derived from a radical chain oxidation mechanism composed of 30 elementary reactions: 19 relative to oxidation of methylene and methyne units plus 11 relative to their eventual cooxidation. The validity of this model has been already checked successfully elsewhere for one homopolymer: polyethylene (PE) (Khelidj et al., 2006a, Khelidj et al., 2006b; Colin et al., 2007). In the present study, it is now checked for polypropylene (PP) and a series of three EPR differing essentially by their mole fraction of ethylene (37%, 73% and 86%) and their crystallinity degree (0%, 5% and 26%). Predicted values of radiation-chemical yields are in good agreement with experimental ones published in the last half past century. 相似文献
128.
Static portfolio choice under Cumulative Prospect Theory 总被引:3,自引:0,他引:3
We derive the optimal portfolio choice for an investor who behaves according to Cumulative Prospect Theory (CPT). The study
is done in a one-period economy with one risk-free asset and one risky asset, and the reference point corresponds to the terminal
wealth arising when the entire initial wealth is invested into the risk-free asset. When it exists, the optimal holding is
a function of a generalized Omega measure of the distribution of the excess return on the risky asset over the risk-free rate. It conceptually resembles Merton’s optimal
holding for a CRRA expected-utility maximizer. We derive some properties of the optimal holding and illustrate our results
using a simple example where the excess return has a skew-normal distribution. In particular, we show how a CPT investor is
highly sensitive to the skewness of the excess return on the risky asset. In the model we adopt, with a piecewise-power value function with different shape
parameters, loss aversion might be violated for reasons that are now well-understood in the literature. Nevertheless, we argue
that this violation is acceptable. 相似文献
129.
Probing the interaction of the potassium channel modulating KCNE1 in lipid bilayers via solid‐state NMR spectroscopy 下载免费PDF全文
Rongfu Zhang Indra D. Sahu Raven G. Comer Sergey Maltsev Carole Dabney‐Smith Gary A. Lorigan 《Magnetic resonance in chemistry : MRC》2017,55(8):754-758
KCNE1 is known to modulate the voltage‐gated potassium channel α subunit KCNQ1 to generate slowly activating potassium currents. This potassium channel is essential for the cardiac action potential that mediates a heartbeat as well as the potassium ion homeostasis in the inner ear. Therefore, it is important to know the structure and dynamics of KCNE1 to better understand its modulatory role. Previously, the Sanders group solved the three‐dimensional structure of KCNE1 in LMPG micelles, which yielded a better understanding of this KCNQ1/KCNE1 channel activity. However, research in the Lorigan group showed different structural properties of KCNE1 when incorporated into POPC/POPG lipid bilayers as opposed to LMPG micelles. It is hence necessary to study the structure of KCNE1 in a more native‐like environment such as multi‐lamellar vesicles. In this study, the dynamics of lipid bilayers upon incorporation of the membrane protein KCNE1 were investigated using 31P solid‐state nuclear magnetic resonance (NMR) spectroscopy. Specifically, the protein/lipid interaction was studied at varying molar ratios of protein to lipid content. The static 31P NMR and T1 relaxation time were investigated. The 31P NMR powder spectra indicated significant perturbations of KCNE1 on the phospholipid headgroups of multi‐lamellar vesicles as shown from the changes in the 31P spectral line shape and the chemical shift anisotropy line width. 31P T1 relaxation times were shown to be reversely proportional to the molar ratios of KCNE1 incorporated. The 31P NMR data clearly indicate that KCNE1 interacts with the membrane. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
130.
Carole Fraschini Anne Pennors Robert E. Prud'homme 《Journal of Polymer Science.Polymer Physics》2007,45(17):2380-2389
Optically pure S(?) and R(+)‐poly(α‐methyl‐α‐ethyl‐β‐propiolactones) (PMEPLs) of controlled low molecular weights were synthesized by anionic polymerization of the corresponding optically active monomers, and characterized using gel permeation chromatography, Maldi‐TOF mass spectrometry, and NMR spectroscopy. Blends of PMEPLs of opposite configurations and different molecular weights were investigated. All blends lead to the formation of a stereocomplex and its crystallization prevails over a wide range of mixing ratios. The stereocomplex melts 30–40 °C above that of the corresponding pure polymers, depending on the molecular weight; pairs of polymers having similar molecular weights exhibit the highest melting temperatures and enthalpies of fusion. Finally, when the stereocomplex is dispersed in a PMEPL matrix, it acts as a very effective nucleation agent for the crystallization of the polymer in excess. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2380–2389, 2007 相似文献