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961.
By measuring stresses in cylinders with no stress gradient in axial direction, the cross-section of the cylinder may be considered
as consisting of concentric rings in each of which the stresses are constant. Axial stress distribution in the cylinder is
determined stepwise starting with the outermost ring (the so-called onion-peeling method). This paper generalizes the onion-peeling
method for the case of axisymmetric stress distributions when stress gradient in the axial direction is present. Measurement
of the integrated isoclinic and optical retardation is carried out in two parallel sections which are perpendicular to the
specimen axis, Δz apart from each other. The distributions of the axial stress and shear stress are determined directly from the measurement
data, using linear approximation of integrated photoelasticity. Other stress components are determined using the equilibrium
equation and the compatibility equation (if stresses are due to external loads) or using the generalized sum rule (if residual
stresses in glass are measured). The method is less sensitive to measurement errors than the Abel inversion. In comparison
with the polynomial approximation of the stress distributions, the onion-peeling method gives more adequate results if stress
distribution is not smooth. The paper is illustrated with several applications. 相似文献
962.
Statistical analysis of HDPE fatigue lifetime 总被引:1,自引:0,他引:1
Fatigue lifetime of HDPE structures such as pipes is recognized to show a large scatter. This study aims to compare different
statistical methods and distributions, in order to give convenient modeling of tensile and fatigue test results of commercially
available polyethylene compression molded sheets. The median rank, the maximum likelihood and the Kolmogorov-Smirnov fitting
are compared for the estimation of Weibull parameters. The choice of the best distribution to fit fatigue lifetime is discussed
on the basis of the goodness-of-fit results. It is found that whether the three-parameter distributions of Weibull and lognormal
types are suitable for lifetime prediction, the two-parameter Weibull is more conservative for probabilistic fatigue design. 相似文献
963.
We investigate how firing activity
of globally coupled neural network depends on the coupling strength C and system size N. Network elements are described by space-clamped FitzHugh-Nagumo (SCFHN) neurons with the values
of parameters at which no firing activity occurs. It is found that for a given appropriate coupling strength, there is an intermediate range of system size where the firing activity of
globally coupled SCFHN neural network is induced and enhanced. On the other hand, for a given intermediate system size level, there exists an optimal value of coupling strength such that the intensity of firing activity reaches its maximum. These phenomena
imply that the coupling strength and system size play a vital role
in firing activity of neural network. 相似文献
964.
载银纳米SiO2对超细羊毛摩擦磨损性能的影响 总被引:1,自引:0,他引:1
用载银纳米SiO2功能液对超细羊毛进行表面改性处理,在羊毛表面形成纳米抗菌层,使纤维具有持久的抗菌性能.通过扫描电子显微镜(SEM)观察到抗菌层厚度约200 nm,纤维表面变均匀.按照国家纤维测试标准对超细羊毛纳米改性前、后单纤维强力和摩擦性能进行测试,结果表明:超细羊毛经过纳米改性后,单纤维强力增大13.4%,断裂伸长率增大38.6%,断裂强度增大22.8%,动摩擦效应减小11.04%,静摩擦效应减小16.25%,改善了超细羊毛的穿着舒适性和耐摩擦磨损性能. 相似文献
965.
UHMWPE基体上沉积GLC薄膜及其摩擦磨损性能研究 总被引:1,自引:1,他引:0
改善超高分子量聚乙烯(UHMWPE)臼杯的耐磨性能是提高人工髋关节使用寿命的关键.本文在UHMWPE基体上采用非平衡直流磁控溅射沉积类石墨碳(GLC)薄膜,用扫描电镜、台阶轮廓仪考察了薄膜形貌和表面粗糙度,拉曼光谱分析了GLC薄膜的结构.用划痕仪和球-盘式摩擦磨损机研究了GLC薄膜与UHMWPE基体的界面结合力和GLC薄膜的摩擦磨损性能.结果表明:磁控溅射法制备的GLC薄膜与基体结合力大于90 N,且对表面粗糙度没有影响;表面镀覆GLC薄膜的体积磨损率为1.6×10-17 m3/(N·m),是UHMWPE的1/19. 相似文献
966.
967.
968.
969.
Kajaks J. A. Reihmane S. A. Bulmanis V. N. Lejnieks J. E. 《Mechanics of Composite Materials》2001,37(2):167-170
The effect of the amount of absorbed water on the physicomechanical indices (tensile modulus and tensile strength) of composites based on low-density polyethylene (LDPE) and linen yarn production waste (LW), both with and without coupling agents (stearic acid - SA and diphenylmetane diisocyanate - DIC), is studied. It is shown that the strength properties depend considerably on the time of water sorption and on the blend composition. The tensile strength decreases with increased amount of absorbed water (with increased time of exposure to distilled water) and with increased content of LW in the composite. Somewhat different results are obtained for systems containing SA and DIC modifiers. The modifiers, intensifying the interfacial interaction, retard the process of water sorption, therefore the drop in the strength indices is not so significant. Of special interest is the behavior of systems with DIC. In some cases, a slight increase in strength (after a two to five day exposure to water) is observed, which is probably caused by cross-linking of the free diisocyanate in the system under the action of moisture. 相似文献
970.