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排序方式: 共有167条查询结果,搜索用时 31 毫秒
31.
We construct and analyze Gauss-type quadrature rules with complex- valued nodes and weights to approximate oscillatory integrals
with stationary points of high order. The method is based on substituting the original interval of integration by a set of
contours in the complex plane, corresponding to the paths of steepest descent. Each of these line integrals shows an exponentially
decaying behaviour, suitable for the application of Gaussian rules with non-standard weight functions. The results differ
from those in previous research in the sense that the constructed rules are asymptotically optimal, i.e., among all known
methods for oscillatory integrals they deliver the highest possible asymptotic order of convergence, relative to the required
number of evaluations of the integrand. 相似文献
32.
A polarizable model for simulation of liquid methanol, compatible with the COS/G2 water model, has been developed using the Charge-on-Spring (COS) technique. The model consists of three point charges, with one polarizable center on the oxygen atom. The Lennard-Jones parameters on the oxygen atom together with the molecular polarizability were varied to reproduce the experimental heat of vaporization and density of liquid methanol at ambient conditions. We examined the energies of various methanol dimers in the gas phase and compared them with values obtained from ab initio calculations. The model was then used to study the thermodynamic, dynamic, structural, and dielectric properties of liquid methanol as well as of a methanol-water mixture. A microscopic picture of the structure of pure liquid methanol and of the methanol-water mixture is provided. Good agreement was found between the results from our model simulations and available experimental and ab initio calculation data. In particular, the experimental dielectric permittivity of 32 could be reproduced, which had been shown to be difficult when using nonpolarizable models. 相似文献
33.
Sonic crystals can be used as acoustic lenses in certain frequencies and the design of such systems by creating vacancies and using genetic algorithms has been proven to be an effective method. So far, rigid cylinders have been used to create such acoustic lens designs. On the other hand, it has been proven that Helmholtz resonators can be used to construct acoustic lenses with higher refraction index as compared to rigid cylinders, especially in low frequencies by utilizing their local resonances. In this paper, these two concepts are combined to design acoustic lenses that are based on Helmholtz resonators. The Multi-Level Wave Based Method is used as the prediction method. The benefits of the method in the context of design procedure are demonstrated. In addition, symmetric boundary conditions are derived for more efficient calculations. The acoustic lens designs that use Helmholtz resonators are compared with the acoustic lens designs that use rigid cylinders. It is shown that using Helmholtz resonator based sonic crystals leads to better acoustic lens designs, especially at the low frequencies where the local resonances are pronounced. 相似文献
34.
Annemiek D. Knijnenburg Emile Spalburg Albert J. de Neeling Roos H. Mars‐Groenendijk Daan Noort Gijsbert M. Grotenbreg Gijs A. van der Marel Herman S. Overkleeft Mark Overhand 《Helvetica chimica acta》2012,95(12):2544-2561
This article presents a series of ring‐extended gramicidin S derivatives, 9 – 14 , that have four ornithine residues as polar protonated side chains and one modified turn region containing a mono‐functionalized cis‐δ‐oxetane, δ‐furanoid, or δ‐pyranoid sugar amino acid residue. Of the GS analogs evaluated, we identified compound 7 , which contains the mono‐benzyloxy cis‐δ‐pyranoid sugar amino acid, as having a better biological profile than the clinically applied topical antibiotic gramicidin S. 相似文献
35.
36.
Renger H. Jellema David J. Louwerse Age K. Smilde Mathieu J. P. Gerritsen Daan Guldemond 《Fresenius' Journal of Analytical Chemistry》2000,368(4):397-406
In steel industries a need exists for the reduction of variation in the element concentrations. This need is triggered by
an increasing demand for high quality steel products by clients. The results of a large-scale experiment concerning the identification
and quantification of sources of variation in the production, sampling and analysis of steel are presented. The results are
obtained by means of a strategic approach that consists of six steps. By means of this strategic approach, insight is obtained
in the build-up of the total variation. This knowledge can be used to reduce the influence of those factors that have a major
impact on the total variation. Attention is focused on estimating the magnitude of sources of variation apparent in sampling
of certain stages of the steel making process and in analysis of steel samples by means of spark emission spectrometry.
Received: 6 November 1999 / Revised: 10 February 2000 / Accepted: 19 March 2000 相似文献
37.
Riadh Neffati Alexander Alexeev Sergey Saunin Jos C. M. Brokken‐Zijp Daan Wouters Stefan Schmatloch Ulrich S. Schubert Joachim Loos 《Macromolecular rapid communications》2003,24(1):113-117
A systematic investigation into the surface properties of siloxane rubber/carbon black (CB) nanocomposites has been performed, using an automated scanning probe microscope. In this way the influence of CB concentration and curing rate of the siloxane rubber matrix on roughness and conductivity of the composites was studied. Decreasing the curing rate while keeping the CB concentration resulted in a decrease in both roughness and surface conductivity, which can be explained by an additional siloxane‐rubber layer formed during curing.
38.
Wilfred F. van Gunsteren Dirk Bakowies Riccardo Baron Indira Chandrasekhar Markus Christen Xavier Daura Peter Gee Daan P. Geerke Alice Glttli Philippe H. Hünenberger Mika A. Kastenholz Chris Oostenbrink Merijn Schenk Daniel Trzesniak Nico F. A. van der Vegt Haibo B. Yu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2006,118(25):4168-4198
39.
Daan S. van Es Guus E. Frissen Jacco van Haveren Leonardus W. Jenneskens 《Polymer Degradation and Stability》2008,93(1):50-58
This paper describes the rheological effects observed after addition of (natural) polyols to several different types of heavy metal-free PVC formulations. It is found that addition of natural polyols, such as sorbitol, leads to changes in the rheology of the system comparable to the addition of external lubricants. Hence as suggested previously, addition of (natural) polyols may lead to the occurrence of undesirable plate-out phenomena. The magnitude of the effect on the rheology depends on the number of hydroxyl groups in the polyol and its propensity to undergo intramolecular cyclodehydration reactions. It is established that the undesirable rheological effects, which coincide with plate-out phenomena, can be suppressed by the addition of various types of inorganic as well as organic substances, most of which are known PVC additives. This will allow for the use of (natural) polyols as efficient and benign co-stabilisers in next generation stabiliser systems. 相似文献
40.
Eko Aditya Rifai Marc van Dijk Nico P. E. Vermeulen Daan P. Geerke 《Journal of computer-aided molecular design》2018,32(1):239-249
Computational protein binding affinity prediction can play an important role in drug research but performing efficient and accurate binding free energy calculations is still challenging. In the context of phase 2 of the Drug Design Data Resource (D3R) Grand Challenge 2 we used our automated eTOX ALLIES approach to apply the (iterative) linear interaction energy (LIE) method and we evaluated its performance in predicting binding affinities for farnesoid X receptor (FXR) agonists. Efficiency was obtained by our pre-calibrated LIE models and molecular dynamics (MD) simulations at the nanosecond scale, while predictive accuracy was obtained for a small subset of compounds. Using our recently introduced reliability estimation metrics, we could classify predictions with higher confidence by featuring an applicability domain (AD) analysis in combination with protein–ligand interaction profiling. The outcomes of and agreement between our AD and interaction-profile analyses to distinguish and rationalize the performance of our predictions highlighted the relevance of sufficiently exploring protein–ligand interactions during training and it demonstrated the possibility to quantitatively and efficiently evaluate if this is achieved by using simulation data only. 相似文献