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991.
Existence and uniqueness of splittings for stationary iterative methods with applications to alternating methods 总被引:3,自引:0,他引:3
Summary. Given a nonsingular matrix , and a matrix of the same order, under certain very mild conditions, there is a unique splitting , such that . Moreover, all properties of the splitting are derived directly from the iteration matrix . These results do not hold when the matrix is singular. In this case, given a matrix and a splitting such that , there are infinitely many other splittings corresponding to the same matrices and , and different splittings can have different properties. For instance, when is nonnegative, some of these splittings can be regular splittings, while others can be only weak splittings. Analogous results
hold in the symmetric positive semidefinite case. Given a singular matrix , not for all iteration matrices there is a splitting corresponding to them. Necessary and sufficient conditions for the existence of such splittings are
examined. As an illustration of the theory developed, the convergence of certain alternating iterations is analyzed. Different
cases where the matrix is monotone, singular, and positive (semi)definite are studied.
Received September 5, 1995 / Revised version received April 3, 1996 相似文献
992.
A new approach to the optimal control of diffusion processes based on Lagrange functionals is presented. The method is conceptually and technically simpler than existing ones. A first class of functionals allows to obtain optimality conditions without any resort to stochastic calculus and functional analysis. A second class, which requires Ito's rule, allows to establish optimality in a larger class of problems. Calculations in these two methods are sometimes akin to those in minimum principles and in dynamic programming, but the thinking behind them is new. A few examples are worked out to illustrate the power and simplicity of this approach.Research performed at the Mathematisches Seminar der Universität Kiel with support provided by an Alexander von Humboldt Foundation fellowship. 相似文献
993.
994.
Melucci M Zambianchi M Favaretto L Gazzano M Zanelli A Monari M Capelli R Troisi S Toffanin S Muccini M 《Chemical communications (Cambridge, England)》2011,47(43):11840-11842
The design, synthesis and structure-property investigation of a new thienopyrrolyl dione substituted oligothiophene material showing reduced band gap energy, low lying LUMO energy level and ambipolar semiconducting behaviour is described. 相似文献
995.
Krasowska M Ferrari M Liggieri L Malysa K 《Physical chemistry chemical physics : PCCP》2011,13(20):9452-9457
Superhydrophobic surfaces have recently attracted a lot of attention due to their self-cleaning properties. The superhydrophobic surfaces used in our studies were prepared using a mixed inorganic-organic coating. In order to check how short chain surface active agents affect the surface energy of such surfaces, their wettability (sessile drop technique) and the kinetics of the three phase contact formation were studied. It was found that with increasing concentrations of n-hexanol and n-octanol the surface energy of these surfaces was only slightly changed, i.e. a small decrease in contact angle values with increasing solution concentration was detected. Even for the most concentrated n-hexanol and n-octanol solutions, the contact angles were in the range 145-155° and the drop rolled off, indicating that the studied surfaces stayed superhydrophobic. Air bubbles, upon collision with such superhydrophobic surfaces, spread over the superhydrophobic surface within milliseconds in the studied solutions. 相似文献
996.
Tanwar J Datta A Tiwari AK Chaturvedi S Ojha H Allard M Chaudary NK Thirumal M Mishra AK 《Dalton transactions (Cambridge, England : 2003)》2011,40(13):3346-3351
A bis-polyazamacrocycle, 10'-bis(acetamido)ethane-bis[1,4,7-tri(carboxymethane)-1,4,7,10-tetraazacyclododecane] (DO3A-AME-DO3A) was synthesized for application in magnetic resonance imaging. The efficacy of DO3A-AME-DO3A as non ionic magnetic contrast agent was tested by performing relaxometric studies on its gadolinium complex. The longitudinal relaxivity, r(1) and transverse relaxivity, r(2) values were found to be 5.84 mM(-1)s(-1) and 6.82 mM(-1)s(-1), per Gd(III) at pH 7.0, 37 °C. The luminescence properties of europium complex of DO3A-AME-DO3A were investigated in aqueous medium. The lifetime of Eu(2)-DO3A-AME-DO3A in water was found to be 0.786 ms. Emission and luminescence lifetime measurements on the europium complex of DO3A-AME-DO3A gives a hydration number of q = 1.9. The reaction enthalpy and entropy were found to be, ΔH(0) = -(6.2 ± 2) kJ mol(-1), ΔS(0) = - (1.8 ± 0.4) kJ mol(-1)K(-1), and K(Eu)(298) = (1.8 ± 0.1). 相似文献
997.
De Simone A Montalvao RW Vendruscolo M 《Journal of chemical theory and computation》2011,7(12):4189-4195
In order to carry out their functions, proteins often undergo significant conformational fluctuations that enable them to interact with their partners. The accurate characterization of these motions is key in order to understand the mechanisms by which macromolecular recognition events take place. Nuclear magnetic resonance spectroscopy offers a variety of powerful methods to achieve this result. We discuss a method of using residual dipolar couplings as replica-averaged restraints in molecular dynamics simulations to determine large amplitude motions of proteins, including those involved in the conformational equilibria that are established through interconversions between different states. By applying this method to ribonuclease A, we show that it enables one to characterize the ample fluctuations in interdomain orientations expected to play an important functional role. 相似文献
998.
Serrano MC Vavra AK Jen M Hogg ME Murar J Martinez J Keefer LK Ameer GA Kibbe MR 《Macromolecular bioscience》2011,11(5):700-709
The synthesis of poly(diol-co-citrate) elastomers that are biocompatible with vascular cells and can modulate the kinetics of the NO release based on the diol of selection is reported. NO-mediated cytostatic or cytotoxic effects can be controlled depending on the NO dose and the exposure time. When implanted in vivo in a rat carotid artery injury model, these materials demonstrate a significant reduction of neointimal hyperplasia. This is the first report of a NO-releasing polymer fabricated in the form of an elastomeric perivascular wrap for the treatment of neointimal hyperplasia. These elastomers also show promise for other cardiovascular pathologies where NO-based therapies could be beneficial. 相似文献
999.
Representation or compression of data sets in the wavelet space is usually performed to retain the maximum variance of the
original or pretreated data, like in the compression by means of principal components. In order to represent together a number
of objects in the wavelet space, a common basis is required, and this common basis is usually obtained by means of the variance
spectrum or of the variance wavelet tree. In this study, the use of alternative common bases is suggested, both for classification
and regression problems. In the case of classification or class-modeling, the suggested common bases are based on the spectrum
of the Fisher weights (a measure of the between-class to within-class variance ratio) or on the spectrum of the SIMCA discriminant
weights. In the case of regression, the suggested common bases are obtained by the correlation spectrum (the correlation coefficients
of the predictor variables with a response variable) or by the PLS (Partial Least Squares regression) importance of the predictors
(the product between the absolute value of the regression coefficient of the predictor in the PLS model and its standard deviation).
Other alternative strategies apply the Gram–Schmidt supervised orthogonalization to the wavelet coefficients. The results
indicate that, both in classification and regression, the information retained after compression in the wavelets space can
be more efficient than that retained with a common basis obtained by variance. 相似文献
1000.
Santos FM Monfort LE Castro DM Pinto JE Leonardi M Pistelli L 《Natural product communications》2011,6(10):1499-1504
Plant models offer a method to examine the efficacy of homeopathic solutions. Homeopathic Phosphorus (P) dynamizations were evaluated on the linear growth and dry biomass of Verbena gratissima, a plant native to Brazil. The yields and chemical characterization of the essential oil are also given. Plants exhibited phenotypic plasticity after the homeopathic Phosphorus treatments. The dynamization 9CH, in particular, interfered with plant growth, height, diameter of stems and total dry mass. 9CH treatment showed the highest yield of essential oil. The essential oil composition of V. gratissima varied according to the different dynamization used. Homeopathic Phosphorus provided the greatest amount of beta-pinene, trans-pinocarveol, trans-pinocamphone and trans-pinocarvyl acetate in comparison with controls. 相似文献