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For a wide range of phenomena, current computational ability does not always allow for atomistic simulations of high-dimensional molecular systems to reach time scales of interest. Coarse-graining (CG) is an established approach to alleviate the impact of computational limits while retaining the same algorithms used in atomistic simulations. It is important to understand how algorithms such as Langevin integrators perform on non-trivial CG molecular systems, and in particular how large of an integration time step can be used without introducing unacceptable amounts of error into averaged quantities of interest. To investigate this, we examined three different Langevin integrators on a CG polymer melt: the recently developed BAOAB method by Leimkuhler and Matthews [J. Chem. Phys. 138 (17), 05B601_1 (2013)], the Grønbech-Jensen and Farago method [Mol. Phys. 111 (8), 983-991 (2013)], or G-JF, and the frequently used Brünger–Brooks–Karplus integrator [Chem. Phys. Lett. 105 (5), 495-500 (1984)], known as BBK. We compute and analyse key statistical properties for each. Our results indicate that the integrators perform similarly for a small friction parameter; however outside this regime, the use of large integration steps produces significant deviations from the predicted diffusivity and steady-state distributions for all methods examined with the exception of G-JF. 相似文献
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A threshold start-up policy is appealing for manufacturing (service) facilities that incur a cost for keeping the machine
(server) on, as well as for each restart of the server from its dormant state. Analysis of single product (customer) systems
operating under such a policy, also known as the N-policy, has been available for some time. This article develops mathematical analysis for multiproduct systems operating
under a cyclic exhaustive or globally gated service regime and a threshold start-up rule. It pays particular attention to
modeling switchover (setup) times. The analysis extends/unifies existing literature on polling models by obtaining as special
cases, the continuously roving server and patient server polling models on the one hand, and the standard M/G/1 queue with N-policy, on the other hand. We provide a computationally efficient algorithm for finding aggregate performance measures, such
as the mean waiting time for each customer type and the mean unfinished work in system. We show that the search for the optimal
threshold level can be restricted to a finite set of possibilities.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
45.
为满足清华大学加速器实验室光阴极微波电子枪实验平台的发展需求,设计了束团电荷量测量系统,可以实现实时测量加速器束团电荷量的目标。这套测量系统基于积分束流变压器,包括前置放大器、门控积分器、模数转换和数据传输模块。利用信号发生器模拟束流,对整套系统进行了离线测量实验。当前置放大器放大倍数取200和20时,AD转换值和束流电荷的比值分别为2.181 PC-1和0.195 PC-1,与理论值2.070 PC-1和0.207 PC-1基本吻合;其对应的电荷量测量误差分别小于2 PC和15 PC。测量结果和模拟束流电荷量值的拟合曲线线性度好,相关系数的平方均大于0.999 0。该结果验证了系统的可行性。 相似文献
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A. Ruzzon Y. Elskens F. Doveil 《Communications in Nonlinear Science & Numerical Simulation》2012,17(2):769-779
A symplectic, symmetric, second-order scheme is constructed for particle evolution in a time-dependent field with a fixed spatial step. The scheme is implemented in one space dimension and tested, showing excellent adequacy to experiment analysis. Higher order schemes are deduced by composition. 相似文献
48.
Delayed Linear Time-Invariant (LTI) fractional-order dynamic systems areconsidered. The analytical stability bound is obtained by using Lambertfunction. Two examples are presented to illustrate the obtainedanalytical results. 相似文献
49.
We derive a new multisymplectic integrator for the Kawahara-type equation which is a fully explicit scheme and thus needs less computation cost. Multisympecticity of such scheme guarantees the long-time numerical behaviors. Nu- merical experiments are presented to verify the accuracy of this scheme as well as the excellent performance on invariant preservation for three kinds of Kawahara-type equations. 相似文献
50.
Cathepsin‐B Induced Controlled Release from Peptide‐Capped Mesoporous Silica Nanoparticles 下载免费PDF全文
Cristina de la Torre Laura Mondragón Carmen Coll Félix Sancenón María D. Marcos Ramón Martínez‐Máñez Pedro Amorós Mar Orzáez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(47):15309-15314
New capped silica mesoporous nanoparticles for intracellular controlled cargo release within cathepsin B expressing cells are described. Nanometric mesoporous MCM‐41 supports loaded with safranin O ( S1‐P ) or doxorubicin ( S2‐P ) containing a molecular gate based on a cathepsin B target peptidic sequence were synthesized. Solids were designed to show “zero delivery” and to display cargo release in the presence of cathepsin B enzyme, which selectively hydrolyzed in vitro the capping peptide sequence. Controlled delivery in HeLa, MEFs WT, and MEFs lacking cathepsin B cell lines were also tested. Release of safranin O and doxorubicin in these cells took place when cathepsin B was active or present. Cells treated with S2‐P showed a fall in cell viability due to nanoparticles internalization, cathepsin B hydrolysis of the capping peptide, and cytotoxic agent delivery, proving the possible use of these nanodevices as new therapeutic tools for cancer treatment. 相似文献