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91.
92.
K. Muralidharan 《商业与工业应用随机模型》2001,17(4):331-343
The modulated power law process (MPLP) is often used to model failure data from repairable system, when both renewal type behaviour and time trends are present. The MPLP allows for the failure rate of a system to be affected by the failure and repair. Since the MLEs of the estimates do not have closed form expressions, they have to be approximated, and hence deriving a test procedure will be difficult. Black and Rigdon (1996) have proposed asymptotic MLEs and asymptotic likelihood ratio tests for the parameters which also do not have closed form expressions and hence are not easy for application. In this paper, we derive a closed form expression for the test statistics which is simple and easy to apply for testing (i) H0: β=1 versus H1: β≠1 when κ is known and (ii) H0: (β=1 and κ=1) versus H1: (β≠1 or κ≠1). The simulation study for percentiles and powers are given. We also compare the performance of the test with that of Black and Rigdon's (1996) test. Some numerical examples are also provided to illustrate the testing procedures. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
93.
94.
ZHANG Jingbo LINYuan YIN Feng & XIAO Xurui 《中国科学B辑(英文版)》2000,43(4):443-449
Interfacial charge transfer kinetics of the nanocrystalline CdSe thin film electrodes have been studied in sodium polysulfide solutions by intensity modulated photocurrent spectroscopy (IMPS). The interfacial direct and indirect charge transfer and recombination processes were analyzed in terms of the parameters: normalized steady state photocurrents and surface state lifetimes obtained by measuring the IMPS responses under different applied potentials and different solution concentrations. IMPS responses of polycrystalline CdSe thin film electrodes were also presented for comparison. 相似文献
95.
The method of temperature modulated DSC has been applied to obtain additional information about the effect of constraints
on the melting behaviour of gel-spun ultra high molecular mass polyethylene (UHMW-PE) fibers coated with a high temperature
stable poly(p-xylylene) (PPX) polymer. The underlying signal, corresponding to the normal DSC signal, reveals two endothermic
peaks for the coated PE fibers. A shift in the underlying and magnitude signal from 142 to 145°C at 0.1 K min–1 , a relative small magnitude signal, together with a vanishing step-like change in the phase signal with increasing PPX coating
layer thickness characterize the constraints in terms of a hindrance of the melting of the unconstrained orthorhombic crystal
fraction. The time constant of the melting process can be estimated as larger than the reciprocal angular frequency 1/ω=5
s of the modulation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
96.
K. J. Kociba 《Journal of Thermal Analysis and Calorimetry》2000,60(3):779-784
This article presents the concept of calibrating temperature in thermomechanical analyzers (TMA) using reference standard
magnetic materials whose Curie temperatures are well-known. This concept has not been tested experimentally to the best of
the author's knowledge. Electrical current applied to a unifilarly wound furnace results in the furnace acting as an electrical
inductor. A magnetic material sample located within such a furnace practically constitutes a solenoid core. A modulated temperature
program directly results in a corresponding varying force exerted by the sample against the TMA probe, if the probe's axis
and the central induced magnetic field line of force are coaxial, and, furthermore, if the direction of the central magnetic
field line of force and the expansion direction of the probe are identical. If a sample undergoes a Curie transition, then
the force which the sample exerts against the probe will diminish to zero as the transition goes to completion. Using a modulated
temperature program throughout this phase transition allows determination of transition completion, by observation of the
point at which the force required to maintain the sample's physical position reaches a steady state from it's previously non-steady
state.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
97.
J. Dweck 《Journal of Thermal Analysis and Calorimetry》2000,60(3):785-793
The DSC curve obtained in conventional equipment usually only shows the resultant thermal effect due to simultaneous phenomena,
which may occur during isothermal or dynamic analyses. This does not allow one to identify the processes properly and may
cause an erroneous interpretation of the resulting curves.
Modulated DSC equipment enhances the operating conditions and the analysis capacity of conventional DSC by superimposing a
sinusoidal temperature modulation on the linear temperature control. Thus reversing and non-reversing heat flow curves are
obtained, which are, respectively, the heat capacity and kinetic components of the DSC curve. Therefore, events that are related
to these components can be separately analyzed.
A method to obtain curves similar to the MDSC reversing and non-reversing components was developed using conventional DSC
equipment in a non-conventional way. It was applied to analyze samples of poly(ethylene terephthalate) (PET) taken from bottles
of mineral water. The second PET crystallization step that occurs during its melting was quantified and an apparent initial
crystallinity was obtained from the resulting data.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
98.
Motivated by certain situations in manufacturing systems and communication networks, we look into the problem of maximizing the profit in a queueing system with linear reward and cost structure and having a choice of selecting the streams of Poisson arrivals according to an independent Markov chain. We view the system as a MMPP/GI/1 queue and seek to maximize the profits by optimally choosing the stationary probabilities of the modulating Markov chain. We consider two formulations of the optimization problem. The first one (which we call the PUT problem) seeks to maximize the profit per unit time whereas the second one considers the maximization of the profit per accepted customer (the PAC problem). In each of these formulations, we explore three separate problems. In the first one, the constraints come from bounding the utilization of an infinite capacity server; in the second one the constraints arise from bounding the mean queue length of the same queue; and in the third one the finite capacity of the buffer reflect as a set of constraints. In the problems bounding the utilization factor of the queue, the solutions are given by essentially linear programs, while the problems with mean queue length constraints are linear programs if the service is exponentially distributed. The problems modeling the finite capacity queue are non-convex programs for which global maxima can be found. There is a rich relationship between the solutions of the PUT and PAC problems. In particular, the PUT solutions always make the server work at a utilization factor that is no less than that of the PAC solutions. 相似文献
99.
Ronny Pieters Hans E. Miltner Guy Van Assche Bruno Van Mele 《Macromolecular Symposia》2006,233(1):36-41
Temperature-induced phase separation of P(EO75-ran-PO25)/PES and reaction-induced phase separation of DGEBA/MDA modified with PVME are studied using MTDSC as an in-situ tool. Phase separation can be probed by the onset of an ‘excess’ contribution in the MTDSC heat capacity signal, in good correspondence with the cloud point temperature. This feature enables the complete construction of the state diagram of P(EO75-ran-PO25)/PES. The detection of phase separation-induced partial vitrification of the high-Tg phase (PES-rich phase) enables to sub-divide the LCST-type heterogeneous region in a zone 1 (no interference of partial vitrification) and a zone 2 (interference of partial vitrification of the PES-rich phase). This sub-division of the heterogeneous region has drastic implications on the remixing behavior of demixed blends. In DGEBA/MDA modified with PVME, reaction-induced phase separation accompanied by an increase in reaction rate, followed by a vitrification step of the epoxy-amine phase can be detected in-situ. In non-isothermal conditions, a diffusion-controlled reaction after vitrification and a final devitrification of the system is also observed. 相似文献
100.
姿态倾斜对时-空联合调制型干涉成像光谱仪成像质量的影响 总被引:1,自引:0,他引:1
时空联合调制型干涉成像光谱仪获取的像面干涉图是带有干涉条纹的二维空间图像,具有对姿态变化敏感的特点.根据该类仪器的成像过程,在竖直摄影时,相邻两帧像面干涉图之间的像移量为一列像元;偏离竖直摄影时,由于像面干涉图的几何变形或旋转,会引入非正常像移.利用共线方程导出了这一非正常像移量的表达式.利用仿真计算说明:这一非正常像移会在像面干涉图序列中不断积累,导致提取出的物体干涉信息失真.在竖直摄影而平台指向精度较低、倾斜摄影、探测器阵列的安装方向精度较低或者航空成像且存在偏流角时,必须对像面干涉图进行有效校正,才能保证最终反演出的物体光谱的真实性. 相似文献