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   825篇
  免费   154篇
  国内免费   296篇
测绘学   7篇
大气科学   36篇
地球物理   327篇
地质学   714篇
海洋学   76篇
天文学   19篇
综合类   8篇
自然地理   88篇
  2024年   3篇
  2023年   12篇
  2022年   15篇
  2021年   25篇
  2020年   34篇
  2019年   45篇
  2018年   27篇
  2017年   41篇
  2016年   44篇
  2015年   38篇
  2014年   50篇
  2013年   76篇
  2012年   50篇
  2011年   44篇
  2010年   42篇
  2009年   65篇
  2008年   48篇
  2007年   69篇
  2006年   78篇
  2005年   67篇
  2004年   51篇
  2003年   39篇
  2002年   32篇
  2001年   40篇
  2000年   50篇
  1999年   34篇
  1998年   27篇
  1997年   22篇
  1996年   22篇
  1995年   21篇
  1994年   15篇
  1993年   5篇
  1992年   13篇
  1991年   9篇
  1990年   7篇
  1989年   4篇
  1988年   5篇
  1987年   1篇
  1986年   2篇
  1984年   1篇
  1977年   1篇
  1954年   1篇
排序方式: 共有1275条查询结果,搜索用时 187 毫秒
81.
人造气液包裹体方法及其在研究热液性质中的应用   总被引:3,自引:0,他引:3       下载免费PDF全文
张毅刚 《地质科学》1992,(2):141-148
人造气液包裹体方法在研究热液的物理化学性质方面较传统方法简便、易行。它可用于研究热液的等容线、不混溶性质及矿物在热液中的溶解度。本文解释了人造气液包裹体的合成方法和人造气液包裹体方法的原理,分述了应用此方法研究热液所取得的最新成果。此法不仅能用于研究热液的性质,也能用于其它方面的研究,具有广阔的前景。  相似文献   
82.
含水层中海水入侵的数学模型   总被引:3,自引:1,他引:3       下载免费PDF全文
提出了考虑过渡带的适合潜水含水层和承压含水层的海水入侵数学模型,导出了相应的方程和定解条件.经实例验证,模型是合理和可靠的.  相似文献   
83.
综述了高压超高压变质岩带的基本构造特征,认为运用体粘滞性流变学理论可以很好地解释高压超高压变质岩的发育过程及其抬升-剥露动力学机制。  相似文献   
84.
In the estimation of momentum fluxes over land surfaces by the bulk aerodynamic method, no unique value of the drag coefficient (C D) is found in the literature. The drag coefficient is generally estimated from special observations at different parts of the world. In this study an attempt is made to estimate drag coefficient over the western desert sector of India using data sets of Monsoon Trough Boundary Layer Experiment (MONTBLEX) during the summer monsoon season of 1990. For this purpose, the fast and slow response data sets obtained simultaneously from a 30 m high micro-meteorological tower at Jodhpur are used. All the observations used in this study are confined to a wind speed regime of 2.5–9.0 ms−1. A comparison of momentum fluxes computed by eddy correlation (direct estimation) with profile and bulk aerodynamic (C D = 3.9 × 10−3, Garratt, 1977) methods revealed that though the nature of variation of the fluxes by all these methods is almost similar, both the indirect methods give an under-estimated value of the fluxes. The drag coefficient is estimated as a function of wind speed and surface stability by a multiple regression approach. An average value of the estimated drag coefficient is found to be of the order of 5.43 × 10−3. The estimated value ofC D is validated with a set of independent observations and found to be quite satisfactory. The recomputed momentum fluxes by bulk aerodynamic method using the estimated drag coefficient are in close agreement with the directly estimated fluxes.  相似文献   
85.
Abstract Quartz-hosted, synthetic CO2-H2O fluid inclusions behave as open systems with respect to diffusional transfer of hydrogen during laboratory-simulated metamorphic re-equilibration at 650, 750 and 825°C and 1.5 kbar total pressure with fO2 defined by the C-CH4 buffer. Microthermometry and Raman spectroscopy show that the initial CO2-H2O inclusions become CO2-CH4-H2-H2O
inclusions after diffusive influx of hydrogen from the reducing confining medium. Measurable changes are observed in inclusion compositions after only 15 days of re-equilibration, implying significant hydrogen mobility at still lower temperatures over geological time spans. Results of synthetic inclusion re-equilibrium experiments have profound implications for the interpretation of natural fluid-inclusion data; failure to account for potential hydrogen migration in inclusions from high-temperature geological environments may lead to erroneous estimates of P-T, and/or the compositions of metamorphic fluids.  相似文献   
86.
LingYun  Chiao 《Island Arc》1993,2(2):94-103
Abstract Focal mechanisms of intermediate-depth earthquakes within the subducted Ryukyu slab indicate a systematic pattern of down-dip extension in the northern part under Kyushu. These mechanisms switch rapidly around the Tokara channel to down-dip compression in the southern part toward Taiwan. This intriguing pattern of strain segmentation, together with the differences between the slab geometry of the northern and southern parts, has raised the question of whether stress segmentation, as defined possibly by a tear fault, might exist in the slab. However the Ryukyu trench has a concave oceanward shape in the northern segment while it is convex in the southern oceanward part toward Taiwan. The inflection zone is located around the Tokara channel. The concept of Gaussian curvature of a curved surface suggests that the along-arc variation of the geometric configuration of a subducted slab is related to the shape of the trench. This is in order to accommodate the lateral membrane deformation of the slab as the oceanic lithosphere subducts from a spherical shell to the geometry delineated by the Wadati-Benioff zone. The membrane deformation regime of the subducted Ryukyu slab and its relation with the trench geometry was examined by assuming that the subduction be modelled by the flow field of a thin viscous sheet. A projection operator was utilized to compute the membrane strain-rate tensor of an arbitrary non-Euclidean surface. Numerical experiments indicated that the northern segment of the slab was dominated by lateral compression and down-dip extension and the southern part by lateral extension and down-dip compression. This transition is sharply located near the Tokara channel. These patterns were compatible with what had been observed from studies of focal mechanisms, suggesting that the strain segmentation might be controlled, at least in part, by the lateral membrane deformation within the slab due to the trench shape in this subduction zone. The slab geometry was predicted by minimizing the integrated total dissipation power; this revealed distinct features that were consistent with observations. This implies that the slab geometry may also be affected by the membrane deformation in a systematic fashion.  相似文献   
87.
The generation of natural gases is much more complicated in comparison with liquid petro-leum in that natural gases could be generated from both humic and sapropelic organic matter at different stages and that natural gases could be organic and inorganic …  相似文献   
88.
国际地球自转服务(IERS)评介   总被引:2,自引:0,他引:2  
回顾了建立国际地球自转服务(IERS)的历史过程,简述了IERS机构各部门的设置及其作用。着重介绍了IERS重建的理由和过程以及新IERS机构的组成。最后给出IERS成果对现有科学研究的作用和意义。  相似文献   
89.
A review of the acute and chronic effects of produced formation water (PFW), drilling fluids (muds) including oil-based cutting muds, water-based cutting muds, ester-based cutting muds and chemical additives, and crude oils associated with offshore oil and gas production was undertaken in relation to both temperate and tropical marine ecological processes. The main environmental effects are summarized, often in tabular form. Generally, the temporal and spatial scales of these studies, along with the large levels of inherent variation in natural environments, have precluded our ability to predict the potential long-term environmental impacts of the offshore oil and gas production industry. A series of critical questions regarding the environmental effects of the offshore oil and gas production industry that still remain unanswered are provided for future consideration.  相似文献   
90.
张红红  徐会文  冯哲 《世界地质》2006,25(4):445-449
在试验研究的基础上对比了无机聚合物硅酸盐和有机聚合物聚乙烯醇(PVA)、部分水解聚丙烯酰胺(PHPA)和非水解聚丙烯酰胺(PAM)的防塌能力;由试验得出吸附成膜的速度和保护膜的致密程度是决定钻井液体系防塌能力的关键因素;钻井液体系的防塌能力是无机聚合物和有机聚合物协同作用的结果;部分水解聚丙烯酰胺钻井液体系的防塌能力较非水解聚丙烯酰胺钻井液体系的防塌能力强。研制的无固相聚合物钻井液在吉林农安、伊通、舒兰和梅河口4个矿区近3 000 m的钻探施工中,孔壁稳定,孔内事故少,岩芯采取率达98%以上。  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