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951.
本研究基于分层黏弹介质模型,考虑强震或大地震同震位错、震后黏滞松弛及主断层段震间构造应力加载三方面效应,给出1480年以来,川滇菱形块体东边界鲜水河断裂带、安宁河断裂带、则木河断裂带和小江断裂带共20个断层段由三方面效应引起的累积库仑应力变化随时间的演化,分析强震间相互作用和强震发生的应力累积背景,定性分析各断层段的地震危险性.同时,分别采用现今台网地震目录和川滇菱形块体东边界各断层段强震复发间隔两种资料,定量计算2030年各断层段的强震发生概率;并基于摩擦本构理论,将周边强震引起的库仑应力变化量作为应力扰动,修正强震发生概率的计算结果.各断层段累积库仑应力演化的结果表明,鲜水河断裂带中部八美段、色拉哈段及南部磨西段、安宁河断裂带冕宁-西昌段、小江断裂带北部巧家-东川段和南部建水段的累积库仑应力显著增加.修正的强震发生概率计算结果显示,鲜水河断裂带中部八美-色拉哈-康定一带、安宁河断裂带冕宁-西昌段、小江断裂带南部华宁-建水一带强震发生概率较高,地震危险性值得关注.本研究基于库仑应力演化计算定性分析强震危险性的同时,基于摩擦本构律理论,结合地震引起的应力扰动和强震发生背景,定量计算修正的强震发生概率,为川滇菱形块体东边界强震危险地点及中长期发震紧迫程度判定提供方法和依据.
相似文献952.
The effect of fully submerged boulders on the flow structure in channels has been studied by some researchers. However, many natural streams have bed material with boulders that are not fully submerged under water. In many natural streams, boulders cover between 1% and 10% of the area of the stream reach. The effect of non-submerged boulders on the velocity profile and flow characteristics is very important for assessing riverbed deformation. The objectives of this paper are to find the pattern of velocity distribution around a non-submerged boulder and to compare it with the classical studies on flow resistance and Reynolds stress distribution in open channels. Also, by considering the variation in the Reynolds stress distribution at different locations around a non-submerged boulder, the effect of a non-submerged boulder on the estimation of shear velocity and resistance to flow has been investigated. Results indicates that inside the scour hole caused by a non-submerged boulder in a river velocity distributions are irregular. However, velocity distributions are regular outside the scour hole. The presence of the boulder causes a considerable deviation of the Reynolds shear stress from the classic distribution, showing a non-specific distribution with negative values. The classical methods for calculating shear velocity are not suitable because these methods do not give detailed velocity and Reynolds stress distributions in natural rivers with a lot of boulders. Thus, the effect of a non-submerged boulder on the estimation of the resistance to flow by considering the variations in velocity and Reynolds stress distributions at different locations around a non-submerged boulder is important and needs to be studied in a natural river instead of just in laboratory flumes. The negative values in Reynolds stress distribution around a boulder indicate that the classical methods are unable to predict resistance to flow, and also show strong turbulence inside the scour hole where the complex flow conditions present ambiguous Reynolds stress distributions. In the current study, to obtain a reasonable estimation of parameters in natural rivers, the classical method has been modified by considering velocity and Reynolds stress distributions through the boundary layer method. 相似文献
953.
New anisotropic covariance models and estimation of anisotropic parameters based on the covariance tensor identity 总被引:2,自引:0,他引:2
Many heterogeneous media and environmental processes are statistically anisotropic. In this paper we focus on range anisotropy,
that is, stochastic processes with variograms that have direction dependent correlation lengths and direction independent
sill. We distinguish between two classes of anisotropic covariance models: Class (A) models are reducible to isotropic after
rotation and rescaling operations. Class (B) models can be separated into a product of one-dimensional functions oriented
along the principal axes. We propose a new Class (A) model with multiscale properties that has applications in subsurface
hydrology. We also present a family of Class (B) models based on non-Euclidean distance metrics that are generated by superellipsoidal
functions. Next, we propose a new method for determining the orientation of the principal axes and the degree of anisotropy,
i.e., the ratio(s) of the correlation lengths. This information reduces the degrees of freedom of anisotropic variograms and
thus simplifies the estimation procedure. In particular, Class (A) models are reduced to isotropic and Class (B) models to
one-dimensional functions. Our method is based on an explicit relation between the second-rank slope tensor (SRST), which
can be estimated from the data, and the covariance tensor. The procedure is conceptually simple and numerically efficient.
It is more accurate for regular (on-grid) data distributions, but it can also be used for sparse (off-grid) spatial distributions.
In the case of non-differentiable random fields the method can be extended using generalized derivatives. We illustrate its
implementation with numerical simulations. 相似文献
954.
Due to their intrinsically nonlinear characteristics, development of control strategies that are implementable and can fully
utilize the capabilities of semiactive control devices is an important and challenging task. In this study, two control strategies
are proposed for protecting buildings against dynamic hazards, such as severe earthquakes and strong winds, using one of the
most promising semiactive control devices, the magnetorheological (MR) damper. The first control strategy is implemented by
introducing an inverse neural network (NN) model of the MR damper. These NN models provide direct estimation of the voltage
that is required to produce a target control force calculated from some optimal control algorithms. The major objective of
this research is to provide an effective means for implementation of the MR damper with existing control algorithms. The second
control strategy involves the design of a fuzzy controller and an adaptation law. The control objective is to minimize the
difference between some desirable responses and the response of the combined system by adaptively adjusting the MR damper.
The use of the adaptation law eliminates the need to acquire characteristics of the combined system in advance. Because the
control strategy based on the combination of the fuzzy controller and the adaptation law doesn’t require a prior knowledge
of the combined building-damper system, this approach provides a robust control strategy that can be used to protect nonlinear
or uncertain structures subjected to random loads.
Supported by: Hong Kong Research Grant Council Competitive Earmarked Research Grant HKUST 6218 / 99E and by the National Science Foundation
under grant CMS 99-00234. 相似文献
955.
956.
基于Markov链模型的储层岩相随机模拟 总被引:3,自引:4,他引:3
在油气储层随机建模研究中,基于Markov链模型的方法是一类较受欢迎的技术,同时也是一类不成熟的技术,问题的症结之一在于侧向的转移概率矩阵很难求取,针对这种情况,作者在深入理解Walther相律的基础上,借鉴模拟退火算法的相应思路,提出了一种岩相模拟的新方法,该方法依据不同岩相的百分比进行随机模拟得到一幅初始图象,而后以按岩相组织剖面得到的垂向和侧向的岩相转移概率矩阵的相似性作为判别标准对图象进行扰动,直至得到满意的图象,二维模型试算结果表明了这种岩相随机模拟方法的可行性。 相似文献
957.
958.
若羌测震台属国家测震台,为了评估该台站背景噪声水平,采用Welch平均周期法,对2009—2019年共11年近5000条小时波形数据进行功率谱计算,分析异常噪声特征.同时,绘制该台站11年无断记数据概率密度函数图,分析整体噪声水平.分析发现:①若羌测震台受持续增加的人类活动影响,背景噪声水平不断升高;②受气压影响,水平... 相似文献
959.
A numerical study of comparison of two one-state-variable,rate- and state-dependent friction evolution laws 下载免费PDF全文
Jeen-Hwa Wang 《地震科学(英文版)》2009,22(2):197-204
The two one-state-variable, rate- and state-dependent friction laws, i.e., the slip and slowness laws, are compared on the basis of dynamical behavior of a one-degree-of-freedom spring-slider model through numerical simulations. Results show that two (normalized) model parameters, i.e., Δ (the normalized characteristic slip distance) and β?α (the difference in two normalized parameters of friction laws), control the solutions. From given values of Δ, β, and α, for the slowness laws, the solution exists and the unique non-zero fixed point is stable when Δ>(β?α), yet not when Δ < (β?α). For the slip law, the solution exists for large ranges of model parameters and the number and stability of the non-zero fixed points change from one case to another. Results suggest that the slip law is more appropriate for controlling earthquake dynamics than the slowness law. 相似文献
960.
Mehmet Bilgili 《洁净——土壤、空气、水》2009,37(3):195-202
The development of wind power installations globally and in Turkey is reviewed here. Firstly, the growth of global installed wind power capacity between 1996 and 2007 is reviewed, and the top countries in terms of total installed wind power capacity by region are identified. Then, wind power installation and its development in Europe are discussed. In addition, the current status and development of Turkey's wind power plants are investigated in detail. 相似文献