首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   380篇
  免费   64篇
  国内免费   67篇
测绘学   12篇
大气科学   27篇
地球物理   147篇
地质学   214篇
海洋学   58篇
天文学   4篇
综合类   21篇
自然地理   28篇
  2024年   2篇
  2023年   7篇
  2022年   8篇
  2021年   11篇
  2020年   14篇
  2019年   13篇
  2018年   13篇
  2017年   19篇
  2016年   16篇
  2015年   10篇
  2014年   18篇
  2013年   28篇
  2012年   24篇
  2011年   7篇
  2010年   24篇
  2009年   27篇
  2008年   25篇
  2007年   27篇
  2006年   12篇
  2005年   15篇
  2004年   18篇
  2003年   16篇
  2002年   13篇
  2001年   14篇
  2000年   14篇
  1999年   32篇
  1998年   16篇
  1997年   6篇
  1996年   8篇
  1995年   13篇
  1994年   5篇
  1993年   4篇
  1992年   5篇
  1991年   4篇
  1990年   1篇
  1989年   4篇
  1988年   2篇
  1987年   4篇
  1986年   2篇
  1985年   2篇
  1984年   1篇
  1983年   3篇
  1982年   1篇
  1981年   2篇
  1978年   1篇
排序方式: 共有511条查询结果,搜索用时 0 毫秒
81.
李迪  张漫  王志旺 《岩土力学》2006,27(Z1):1156-1160
传统的岩体承压板法变形试验以假定岩体为半无限均质弹性介质为前提,只能得出一个综合(等效)的弹性(或变形)模量,对于水电工程中经常遇到的薄的软弱层带的模量不能测定。为此,需要在传统的岩体变形承压板法试验的基础上发展淅的层状岩体承压板法变形试验,它可以利用分层弹模计算的方法测定出软弱层带及其他各个岩层的模量,是岩石力学试验方法上的一次突破。笔者将首次系统地介绍这种新的试验原理、实施、分层弹模计算方法和工程应用。  相似文献   
82.
The stable growth condition of a segregated ice layer is studied by the use of the principle of mass and heat conservation. This condition evidently depends upon the properties of a thin transitional zone, which is believed to exist between the boundary of an ice layer and a 0[°C] isotherm. All probable models of the transitional zone are classified and the conditions for each model is derived. The effect of the small amount of soil minerals contained in an ice layer is also studied.  相似文献   
83.
太平煤矿深厚土层的水文地质工程地质性质   总被引:1,自引:0,他引:1  
依据对太平煤矿3号煤区深厚土层的水文地质与工程地质勘测及室内外实验结果,分析了主要的水文地质与工程地质特征及其对3号煤开采的影响,对矿区防水煤岩柱留设高度进行了合理确定。  相似文献   
84.
非线性土层地震反应分析的一种方法   总被引:12,自引:0,他引:12  
本文利用作者给出的土的剪切动力本构关系的动态骨架曲线模型,结合显式差分数值逐步积分方法,给出了一种分析非线性土层地震反应的方法。反应计算中,地震效应视为基底剪切波垂直入射,且考虑了上部土层中能量向弹性基底辐射的效应。文章最后给出了本方法应用的一个算例,并给出了相应的等效线性化方法的计算结果。  相似文献   
85.
单管高压旋喷注浆技术在砂层加固、止水工程中的应用   总被引:1,自引:0,他引:1  
李文华  张瑞琼 《江苏地质》2004,28(2):103-106
就其他工艺在砂层的加固、止水工程中难以解决的问题,提出了单管高压旋喷注浆技术,并通过一些工程实例证实此工艺的可行性。  相似文献   
86.
We report high-resolution observations of the southward-IMF cusp/cleft ionosphere made on December 16th 1998 by the EISCAT (European incoherent scatter) Svalbard radar (ESR), and compare them with observations of dayside auroral luminosity, as seen at a wavelength of 630 nm by a meridian scanning photometer at Ny Ålesund, and of plasma flows, as seen by the CUTLASS (co-operative UK twin location auroral sounding system) Finland HF radar. The optical data reveal a series of poleward-moving transient red-line (630 nm) enhancements, events that have been associated with bursts in the rate of magnetopause reconnection generating new open flux. The combined observations at this time have strong similarities to predictions of the effects of soft electron precipitation modulated by pulsed reconnection, as made by Davis and Lockwood (1996); however, the effects of rapid zonal flow in the ionosphere, caused by the magnetic curvature force on the newly opened field lines, are found to be a significant additional factor. In particular, it is shown how enhanced plasma loss rates induced by the rapid convection can explain two outstanding anomalies of the 630 nm transients, namely how minima in luminosity form between the poleward-moving events and how events can re-brighten as they move poleward. The observations show how cusp/cleft aurora and transient poleward-moving auroral forms appear in the ESR data and the conditions which cause enhanced 630 nm emission in the transients: they are an important first step in enabling the ESR to identify these features away from the winter solstice when supporting auroral observations are not available.  相似文献   
87.
在中下扬子地区地壳区域性滑动层位岩石物性力学参数研究的基础上,对上扬子地区地壳的相应岩层进行了系统的定量测试。其滑动层位各种参量在塑性、韧性和粘性上所表现出特征的规律,在我国南方型数字地层中,具有一定的普遍性和可比性。同时,也揭示了地壳的构造分层性,并可作为上扬子板块浅层地质—地球物理特征分析的重要依据和建库信息。  相似文献   
88.
A 1-D General Ocean Turbulence Model that includes the effects of sediment-induced stratification is shown to simulate the observed onshore and offshore migration of a nearshore sandbar. The only two free parameters of the model, the bed reference concentration and the sediment diffusivity, are taken from the literature, rather than tuned to the data used here. The model results suggest that predictions of onshore bar migration, in which wave-induced sediment transport confined to within a few centimeters of the bottom dominates, are not greatly affected by accounting for buoyancy effects. The model results also suggest that both mean flows and waves transport sediment during offshore bar migration, with different components of transport dominating at different cross-shore locations across the bar-trough bathymetry. Neglecting the effects of sediment-induced stratification results in higher model skill during the largest waves, likely because the excess turbulence production simulated by the non-stratified model is counterbalanced by neglected breaking-wave-generated turbulence. Considering both onshore and offshore migration, the model that includes sediment-induced stratification has higher skill than the model without stratification.  相似文献   
89.
Many researchers have studied the influence of rainfall patterns on soil water movement processes using rainfall simulation experiments. However, less attention has been paid to the influence under natural condition. In this paper, rainfall, soil water content (SWC), and soil temperature at 10‐, 20‐, 30‐, 40‐, and 50‐cm depths were simultaneously monitored at 1‐min intervals to measure the variation in SWC (SWCv) in response to rainfall under different rainfall patterns. First, we classified rainfall events into four patterns. During the study period, the main pattern was the advanced rainfall pattern (38% of all rainfall events), whereas the delayed, central, and uniform rainfall patterns had similar frequencies of about 20%. During natural rainfall, rainwater rapidly passed through the top soil layers (10–40 cm) and was accumulated in the bottom layer (50 cm). When a high rainfall pulse occurred, the water storage balance was disturbed, resulting in the drainage of initial soil water from the top layers into the deeper layers. Therefore, the critical function of the top layers and the bottom layers was infiltration and storage, respectively. The source of water stored in the bottom layer was not only rainfall but also the initial soil water in the upper soil layers. Changes in soil temperature at each soil depth were comonitored with SWCv to determine the movement characteristics of soil water under different rainfall patterns. Under the delayed rainfall pattern, preferential flows preferred to occur. Under the other rainfall patterns, matrix flow was the main form of soil water movement. Rainfall amount was a better indicator than rainfall intensity for SWCv in the bottom layer under the delayed rainfall pattern. These results provide insights into the responses of SWCv under different rainfall patterns in northern China.  相似文献   
90.
There is considerable evidence of widespread damage in the 7th millennium habitation sites across Jordan. The origins of this damage are unknown, but the most widely accepted hypothesis associates the resulting rubble and gravel deposits with the Holocene Rapid Climate Change. One way of testing the various hypotheses is to provide a more reliable chronology for the event(s) in question. In this study, we used quartz OSL and feldspar IRSL signals to date accumulative rubble layers at two archaeological sites in Southern Jordan; Ba'ja and Basta. By comparison with the OSL ages, the IRSL ages demonstrate that most of the quartz samples were sufficiently well bleached at deposition to provide accurate ages. Quartz ages show that deposition of the rubble layers took place in different episodes starting around 8.5 ka and 6.0 ka. Ages from Ba'ja site agree with the archaeological expectations of time of deposition. However, the results from Basta are younger than the archaeological expectations, which are based mainly on architectural style and stratigraphy.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号