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121.
122.
四川省8 ·13特大泥石流灾害特点、成因与启示 总被引:2,自引:0,他引:2
2010年8月12~14日,四川省部分地区普降大到暴雨,在5 ·12汶川地震极重灾区的绵竹市清平乡、汶川县映秀镇和都江堰龙池镇诱发了极为严重的泥石流灾害。本次泥石流灾害表明:地震区和非地震区、震前和震后的泥石流在发育分布规律、启动条件、暴发规模、活动形式及其成灾方式和危害性等方面都具有显著的差别。通过对8 ·13清平乡泥石流、映秀红椿沟泥石流以及龙池泥石流的基本分析,表明8 ·13泥石流具有群发性、突发性、破坏性、灾害链效应等特点,同时还具有沿发震断裂呈带状分布、物源主要来自于汶川地震触发的崩滑堆积物、活动形式主要表现为"拉槽"侵蚀等显著特征。震区异常丰富的松散固体物源和极端气候所造成的局地短时强降雨是泥石流暴发的根本原因。针对汶川地震区泥石流暴发的新特点,应进一步加强对震区泥石流的防治,尤其是针对具有重大泥石流隐患的沟谷,一方面应提高设防标准,强化工程治理和专业监测预警,另一方面更应引入风险管理和控制的理念,注重"防"治"结合; "软"硬"结合; 工程措施与非工程措施结合; "治理"与"管理"结合,调动全社会力量,共同防范地质灾害。 相似文献
123.
针对一种充气前缘(inflatable leading edge, ILE)增升技术,建立了其充气结构与流场耦合作用的运动方程. 将方程写成状态空间形式,
采用时域推进方法求解. 对使用了变前缘增升技术的NACA
63-212翼型进行了充气结构静变形的数值计算,结果表明充气结构的刚度对翼型的气动特性
有明显影响. 与原翼型相比,在不考虑充气结构变形时, 该增升技术大约能使翼型的失速迎角
增加30{\%},最大升力系数增加22{\%};考虑结构变形后增升效果有所降低. 刚度较低的薄
膜在前缘吸力峰的作用下会隆起形成鼓包,容易引起流动分离. 相似文献
124.
We have made an extensive numerical study of a modified model proposed by Olami,Feder,and Christensen to describe earthquake behavior.Two situations were considered in this paper.One situation is that the energy of the unstable site is redistributed to its nearest neighbors randomly not averagely and keeps itself to zero.The other situation is that the energy of the unstable site is redistributed to its nearest neighbors randomly and keeps some energy for itself instead of reset to zero.Different boundary conditions were considered as well.By analyzing the distribution of earthquake sizes,we found that self-organized criticality can be excited only in the conservative case or the approximate conservative case in the above situations.Some evidence indicated that the critical exponent of both above situations and the original OFC model tend to the same result in the conservative case.The only difference is that the avalanche size in the original model is bigger.This result may be closer to the real world,after all,every crust plate size is different. 相似文献
125.
We find prominent similarities in the features of the time series for the (model earthquakes or) overlap of two Cantor sets
when one set moves with uniform relative velocity over the other and time series of stock prices. An anticipation method for
some of the crashes have been proposed here, based on these observations.
相似文献
126.
A. E. El-Ahmady 《Rendiconti del Circolo Matematico di Palermo》2004,53(3):443-450
In this paper, we will give a new definition for folding of fuzzy horocycle. It introduces the concept of fuzzy horocycle.
Also we will deduce the relation between the folding of fuzzy circles and fuzzy horocycles. Theorems governing this type of
folding are deduced. 相似文献
127.
B. Örçal A. Erzan 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(4):721-728
We study the temporal and spatial correlations in a one-dimensional model of a heterogeneous fault zone, in the presence of
viscoelastic effects. As a function of dynamical weakening and of dissipation, the system exhibits three different “phases":
one in which there are no time correlations between the events, a second, in which there are “Omori's law” type temporal correlations,
and a third, runaway phase with quasiperiodic system size events.
Received 30 May 2000 and Received in final form 7 September 2000 相似文献
128.
用虚拟激励法求解非比例阻尼线性体系的非平稳随机地震响应 总被引:2,自引:0,他引:2
应用复振型分解方法,将非比例阻尼线性体系在地震作用下的动力方程求解问题转化为若干个广义复振子的求解与叠加问题。通过假定地震地面运动为一零均值的非平稳随机激励,应用虚拟激励法原理,推导得到了广义复振子动力坐标计算的一般公式,进而得到了非比例阻尼线性体系非平稳随机地震响应计算的一般解答。由于可以选择少量共轭复振型的影响进行计算,对于大型复杂非比例阻尼结构,其随机地震响应计算工作量可以大幅度减小。算例证实了这种方法的可靠性及可行性。 相似文献
129.
A unified approach to two types of evolutionary random response problems in engineering 总被引:7,自引:0,他引:7
Summary Response of structures to earthquake excitations and response of vehicles to road undulations are two typical evolutionary
random problems in engineering. Both kinds of the evolutionary random excitations can be regarded as evolved from stationary
random excitations, though through two utterly different ways. The former one may be obtained by filtering a stationary random
process through a linear time-dependent system, while the latter one may result from nonlinear transformations of the argument
of a stationary random process. However, the response problems due to both types of excitations have much in common. By introducing
the concept of “evolutionary frequency response”, the expressions of the response evolutionary spectra for both problems can
be obtained in a unified, concise way, similar to the input/output PSD relationship in a stationary random problem. For both
the evolutionary random problems, the solution procedures are all the same, but the expressions for evolutionary frequency
responses are different from each other. Moreover, the evolutionary frequency responses may be interpreted as transient responses
of the system subject to certain deterministic evolutionary harmonic excitations. In this sense, an evolutionary random response
problem can be reduced to a deterministic response problem. Based on the complex modal analysis, a unified approach to these
two response problems is derived here. The method can be applied to any linear time-invariant systems, whether they are symmetrical
or not, and whether they are classically damped or not. And the method might be hopefully applied to nonlinear systems, if
the statistical linearization technique is accompanied. To the knowledge of the authors, this unified approach to two types
of evolutionary random response problems is the first time reported in literature.
Received 28 May 1996; accepted for publication 8 January 1997 相似文献
130.
A model on the earthquake effects combination in wind resistant design of high-rise flexible structures is proposed in accordance with the probability method. Based on the Turkstra criteria, the stochastic characters of wind velocity, earthquake ground acceleration and excitations occurrence probability are taken into account and then the combination of the earthquake effects in structure wind resistant design is analyzed with the convolution approach. The results indicate that as for the tall flexible buildings whose lateral force is governed by wind loading, the maximum lateral loads verification with respect to the wind resistant design combined with earthquake effects may be more unfavorable compared with that in terms of the earthquake resistant design involving wind effects. 相似文献