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81.
Giraldo A 《Community genetics》2004,7(2-3):126-129
Medical genetic services, including clinical genetics, cytogenetics, biochemical and molecular genetics and paternity testing, are performed in Colombia in the more developed medical schools or university institutions, in nine major cities of the country. Accessibility to genetic services is limited by medical care reimbursement laws which do not cover clinical genetic services nor genetic tests. Paternity testing is performed free of charge by a governmental welfare institution, if a legal claim is made against an alleged father. Basic teaching of genetics in medical schools is mandatory, but is very uneven and limited to the better schools. Postgraduate medical genetic training is offered by four different programs of similar quality. Research is performed on some of the most prevalent genetic conditions and on population genetic issues. 相似文献
82.
María S. Renzini Laura C. Lerici Ulises Sedran Liliana B. Pierella 《Journal of Analytical and Applied Pyrolysis》2011,92(2):450-455
The stability of H-ZSM-11 (H-Z) and H-BETA (H-B) zeolites during the catalytic degradation of low-density polyethylene (LDPE) was studied using the same sample of catalyst in eleven consecutive cycles. The gaseous hydrocarbons, liquid hydrocarbons and waxes generated in each cycle were analyzed as well as the used catalyst. The zeolites were characterized by XRD, FTIR of adsorbed pyridine and N2 adsorption, while the physical mixtures of LDPE/zeolites were subjected to TG-DTG analysis.The H-Z zeolite exhibited an important stability during the successive cycles of LDPE conversion. On the contrary, the behavior H-B zeolite was completely different; from the sixth cycle the yields of products changed progressively, approaching to that obtained in a purely thermal process.The yields of accumulated coke increased steadily throughout the cycles up to maximum values in the eleventh cycle of ∼6 and ∼15 wt% for H-Z and H-B, respectively. These results were confirmed by TG under air flow. 相似文献
83.
Perez AA Sánchez CC Patino JM Rubiolo AC Santiago LG 《Colloids and surfaces. B, Biointerfaces》2011,85(2):50-315
Milk whey proteins (MWP) and pectins (Ps) are biopolymer ingredients commonly used in the manufacture of colloidal food products. Therefore, knowledge of the interfacial characteristics of these biopolymers and their mixtures is very important for the design of food dispersion formulations (foams and/or emulsions). In this paper, we examine the adsorption and surface dilatational behaviour of MWP/Ps systems under conditions in which biopolymers can saturate the air-water interface on their own. Experiments were performed at constant temperature (20 °C), pH 7 and ionic strength 0.05 M. Two MWP samples, β-lactoglobulin (β-LG) and whey protein concentrate (WPC), and two Ps samples, low-methoxyl pectin (LMP) and high-methoxyl pectin (HMP) were evaluated. The contribution of biopolymers (MWP and Ps) to the interfacial properties of mixed systems was evaluated on the basis of their individual surface molecular characteristics. Biopolymer bulk concentration capable of saturating the air-water interface was estimated from surface pressure isotherms. Under conditions of interfacial saturation, dynamic adsorption behaviour (surface pressure and dilatational rheological characteristics) of MWP/Ps systems was discussed from a kinetic point of view, in terms of molecular diffusion, penetration and configurational rearrangement at the air-water interface. The main adsorption mechanism in MWP/LMP mixtures might be the MWP interfacial segregation due to the thermodynamic incompatibility between MWP and LMP (synergistic mechanism); while the interfacial adsorption in MWP/HMP mixtures could be characterized by a competitive mechanism between MWP and HMP at the air-water interface (antagonistic mechanism). The magnitude of these phenomena could be closely related to differences in molecular composition and/or aggregation state of MWP (β-LG and WPC). 相似文献
84.
85.
Aminoacyl phosphates, biomimetic analogues of aminoacyl adenylates, react efficiently with amino acid esters to form dipeptides with retention of stereochemical integrity. The reactions are selective and occur readily in the presence of nucleophiles other than amino groups on their side chains. Aminoacyl phosphate esters that lack an amino-protecting group are also suitable for peptide bond formation, leading to a simplified overall process. 相似文献
86.
Radical alkylation of 2-(tert-butyl)-2-methyldioxolan-4-one, a chiral equivalent of glycolic acid, occurs with good to high diastereoselectivity that compares favorably with the corresponding enolate alkylation. The importance of the position of the transition state position, early or late, is highlighted. 相似文献
87.
Liliana Garrido Lopera Jorge Alberto Achcar 《Applied mathematics and computation》2011,218(7):3635-3648
In this paper, we introduce a Bayesian analysis for mixture of distributions belonging to the exponential family. As a special case we consider a mixture of normal exponential distributions including joint modeling of the mean and variance. We also consider joint modeling of the mean and variance heterogeneity. Markov Chain Monte Carlo (MCMC) methods are used to obtain the posterior summaries of interest. We also introduce and apply an EM algorithm, where the maximization is obtained applying the Fisher scoring algorithm. Finally, we also include analysis of real data sets to illustrate the proposed methodology. 相似文献
88.
de Campo L Varslot T Moghaddam MJ Kirkensgaard JJ Mortensen K Hyde ST 《Physical chemistry chemical physics : PCCP》2011,13(8):3139-3152
Triphilic star-polyphiles are short-chain oligomeric molecules with a radial arrangement of hydrophilic, hydrocarbon and fluorocarbon chains linked to a common centre. They form a number of liquid crystalline structures when mixed with water. In this contribution we focus on a hexagonal liquid crystalline mesophase found in star-polyphiles as compared to the corresponding double-chain surfactant to determine whether the hydrocarbon and fluorocarbon chains are in fact demixed in these star-polyphile systems, or whether both hydrocarbon and fluorocarbon chains are miscible, leading to a single hydrophobic domain, making the star-polyphile effectively amphiphilic. We report SANS contrast variation data that are compatible only with the presence of three distinct immiscible domains within this hexagonal mesophase, confirming that these star-polyphile liquid crystals are indeed hydrophilic/oleophilic/fluorophilic 3-phase systems. Quantitative comparison with scattering simulations shows that the experimental data are in very good agreement with an underlying 2D columnar (12.6.4) tiling. As in a conventional amphiphilic hexagonal mesophase, the hexagonally packed water channels (dodecagonal prismatic domains) are embedded in a hydrophobic matrix, but that matrix is split into oleophilic hexagonal prismatic domains and fluorophilic quadrangular prismatic domains. 相似文献
89.
Liliana V. Lukashuk Andrey B. Lysenko Harald Krautscheid Konstantin V. Domasevitch 《Acta Crystallographica. Section C, Structural Chemistry》2011,67(12):m378-m383
Poly[bis(3,3′,5,5′‐tetramethyl‐4,4′‐bi‐1H‐pyrazole‐2,2′‐diium) γ‐octamolybdate(VI) dihydrate], {(C10H16N4)2[Mo8O26]·2H2O}n, (I), and bis(3,3′,5,5′‐tetramethyl‐4,4′‐bi‐1H‐pyrazole‐2,2′‐diium) α‐dodecamolybdo(VI)silicate tetrahydrate, (C10H16N4)2[SiMo12O40]·4H2O, (II), display intense hydrogen bonding between the cationic pyrazolium species and the metal oxide anions. In (I), the asymmetric unit contains half a centrosymmetric γ‐type [Mo8O26]4− anion, which produces a one‐dimensional polymeric chain by corner‐sharing, one cation and one water molecule. Three‐centre bonding with 3,3′,5,5′‐tetramethyl‐4,4′‐bi‐1H‐pyrazole‐2,2′‐diium, denoted [H2Me4bpz]2+ [N...O = 2.770 (4)–3.146 (4) Å], generates two‐dimensional layers that are further linked by hydrogen bonds involving water molecules [O...O = 2.902 (4) and 3.010 (4) Å]. In (II), each of the four independent [H2Me4bpz]2+ cations lies across a twofold axis. They link layers of [SiMo12O40]4− anions into a three‐dimensional framework, and the preferred sites for pyrazolium/anion hydrogen bonding are the terminal oxide atoms [N...O = 2.866 (6)–2.999 (6) Å], while anion/aqua interactions occur preferentially viaμ2‐O sites [O...O = 2.910 (6)–3.151 (6) Å]. 相似文献
90.
Alexander Linkov Liliana Rybarska-Rusinek 《Archive of Applied Mechanics (Ingenieur Archiv)》2011,81(9):1203-1214
The paper presents a method for deriving interface conditions simulating the influence of a thin wedge in a multi-wedge system
with smooth contacts. It consists in successive (i) employing the Mellin’s transform, (ii) separation of the symmetric and
anti-symmetric parts of a solution, (iii) distinguishing terms tending to infinity, when the wedge angle tends to zero, (iv)
appropriate re-arrangement of the terms to avoid degeneration, (v) using truncated power series in equations for the thin
wedge and (vi) inspection of the characteristic determinant and finding models simulating the influence of the thin wedge
for various combinations of parameters. The paper extends and improves the results previously obtained by the authors for
a harmonic problem. The analysis leads to three physical models of contact interaction, which cover all the ratios of shear
modules of a thin wedge and neighbour wedges. Numerical examples illustrate the accuracy provided by the method employed and
the models derived. 相似文献