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91.
92.
93.
We propose a new scenario tree reduction algorithm for multistage stochastic programs, which integrates the reduction of a
scenario tree into the solution process of the stochastic program. This allows to construct a scenario tree that is highly
adapted on the optimization problem. The algorithm starts with a rough approximation of the original tree and locally refines
this approximation as long as necessary. Promising numerical results for scenario tree reductions in the settings of portfolio
management and power management with uncertain load are presented. 相似文献
94.
Algorithms for separable nonlinear least squares with application to modelling time-resolved spectra
Katharine M. Mullen Mikas Vengris Ivo H. M. van Stokkum 《Journal of Global Optimization》2007,38(2):201-213
The multiexponential analysis problem of fitting kinetic models to time-resolved spectra is often solved using gradient-based
algorithms that treat the spectral parameters as conditionally linear. We make a comparison of the two most-applied such algorithms,
alternating least squares and variable projection. A numerical study examines computational efficiency and linear approximation
standard error estimates. A new derivation of the Fisher information matrix under the full Golub-Pereyra gradient allows a
numerical comparison of parameter precision under variable projection variants. Under the criteria of efficiency, quality
of standard error estimates and parameter precision, we conclude that the Kaufman variable projection technique performs well,
while techniques based on alternating least squares have significant disadvantages for application in the problem domain. 相似文献
95.
Summary. The iterative aggregation method
for the solution of linear systems is
extended in several directions:
to operators on Banach spaces; to the method with inexact correction, i.e.,
to methods where the (inner) linear system is in turn solved
iteratively; and to the problem of finding
stationary distributions of Markov operators.
Local convergence is shown in all cases.
Convergence results apply to the particular case of stochastic
matrices. Moreover, an argument is given which suggests why the
iterative aggregation method works so well for nearly
uncoupled Markov chains, as well as for Markov chains with
other zero-nonzero structures.
Received
May 25, 1991/Revised version received February 23, 1994 相似文献
96.
97.
The paper surveys some recent results on iterative aggregation/disaggregation methods (IAD) for computing stationary probability vectors of stochastic matrices and solutions of Leontev linear systems. A particular attention is paid to fast IAD methods. 相似文献
98.
Prof. Dr. Ivo Leito Prof. Dr. Ilmar A. Koppel Dr. Ivar Koppel Dr. Karl Kaupmees Sofja Tshepelevitsh Jaan Saame 《Angewandte Chemie (International ed. in English)》2015,54(32):9262-9265
The potential limits of superbasicity achievable with different families of neutral bases by expanding the molecular framework are explored using DFT computations. A number of different core structures of non‐ionic organosuperbases are considered (such as phosphazenes, guanidinophosphazenes, guanidino phosphorus ylides). A simple model for describing the dependence of basicity on the extent of the molecular framework is proposed, validated, and used for quantitatively predicting the ultimate basicities of different compound families and the rates of substituent effect saturation. Some of the considered bases (guanidino phosphorus carbenes) are expected to reach gas‐phase basicity around 370 kcal mol?1, thus being the most basic neutral bases ever reported. Also, the classical substituted alkylphosphazenes were predicted to reach pKa values of around 50 in acetonitrile, which is significantly higher than previously expected. 相似文献
99.
Anneli Kruve Riin Rebane Karin Kipper Maarja-Liisa Oldekop Hanno Evard Koit Herodes Pekka Ravio Ivo Leito 《Analytica chimica acta》2015
This is the part I of a tutorial review intending to give an overview of the state of the art of method validation in liquid chromatography mass spectrometry (LC–MS) and discuss specific issues that arise with MS (and MS/MS) detection in LC (as opposed to the “conventional” detectors). The Part I briefly introduces the principles of operation of LC–MS (emphasizing the aspects important from the validation point of view, in particular the ionization process and ionization suppression/enhancement); reviews the main validation guideline documents and discusses in detail the following performance parameters: selectivity/specificity/identity, ruggedness/robustness, limit of detection, limit of quantification, decision limit and detection capability. With every method performance characteristic its essence and terminology are addressed, the current status of treating it is reviewed and recommendations are given, how to determine it, specifically in the case of LC–MS methods. 相似文献
100.
A Novel Alkaloid from Aspidosperma pyricollum (Apocynaceae) and Complete 1H and 13C Chemical Shift Assignments 下载免费PDF全文
Hádria M. do Carmo Raimundo Braz‐Filho Ivo J. Curcino Vieira 《Helvetica chimica acta》2015,98(10):1381-1386
A novel natural product indole, alkaloid, named rel‐pyricolluminol ( 1 ), was isolated from Aspidosperma pyricollum Müll .Arg . together with six known metabolites sitsirikine ( 2 ), aparicin ( 3 ), ulein ( 4 ), stemmadenine ( 5 ), lupeol ( 6 ), and (3β)‐sitoster‐3‐yl β‐D ‐glucopyranoside ( 7 ). These compounds were characterized on the basis of their spectral data, mainly 1D‐ (1H,13C‐DEPTQ) and 2D‐NMR (1H,1H‐COSY, NOESY, HSQC, and HMBC), and mass spectra (EI‐MS and HR‐ES‐MS), involving also comparison with data from the literature. 相似文献