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   35701篇
  免费   18337篇
  国内免费   43276篇
测绘学   2843篇
大气科学   21720篇
地球物理   12942篇
地质学   35554篇
海洋学   16056篇
天文学   991篇
综合类   4688篇
自然地理   2520篇
  2024年   172篇
  2023年   373篇
  2022年   608篇
  2021年   936篇
  2020年   2092篇
  2019年   5454篇
  2018年   5773篇
  2017年   5435篇
  2016年   5528篇
  2015年   4860篇
  2014年   4365篇
  2013年   4903篇
  2012年   4574篇
  2011年   4360篇
  2010年   4361篇
  2009年   3671篇
  2008年   2953篇
  2007年   2999篇
  2006年   2587篇
  2005年   2525篇
  2004年   2792篇
  2003年   2528篇
  2002年   2243篇
  2001年   2051篇
  2000年   1706篇
  1999年   1789篇
  1998年   1867篇
  1997年   1924篇
  1996年   1524篇
  1995年   1444篇
  1994年   1291篇
  1993年   1257篇
  1992年   1069篇
  1991年   795篇
  1990年   740篇
  1989年   629篇
  1988年   543篇
  1987年   408篇
  1986年   343篇
  1985年   263篇
  1984年   287篇
  1983年   172篇
  1982年   207篇
  1981年   151篇
  1980年   115篇
  1979年   108篇
  1978年   46篇
  1977年   42篇
  1971年   53篇
  1970年   44篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
中国黄铁矿资源丰富,按元素和矿物组合的不同,其矿床类型可分为:黄铁矿矿床;黄铁矿型铜矿床;含锌、铜黄铁矿型矿床;黄铁矿型多金属矿床;含钨黄铁矿型铜矿床;含锡黄铁矿型矿床;含金黄铁矿型矿床。最主要的成因类型是海底喷气沉积矿床,它广泛分布于不同时期的造山带及早前寒武纪克拉通。黄铁矿形成的构造环境可分为5种,即:边缘浅海或优地槽环境;上叠的断裂坳陷带;洋中脊;岛弧地带;陆相火山盆地。  相似文献   
92.
以内蒙古为例,探讨了内陆待开发地区的产业发展模式,内陆待开发地区经济发展的主要制约因素是缺乏资金,缺乏技术,缺乏人才,因此,其经济发展必须有选择,有重点地优先发展部分行业。一般说来,待开发的内陆地区其经济发展必须以资源优势为依托,以市场为导向,开发优质名牌产品,发展优势产业,建设主导产业,带动地区经济的起飞。  相似文献   
93.
华南阿伦尼格世几丁虫生物地层与古生物地理   总被引:14,自引:0,他引:14  
陈孝红  汪啸风 《地质论评》1996,42(3):200-208,T001
本文系统介绍了湖北宜昌黄花场及浙江常山黄泥塘剖面Arenig统几丁虫分布发育规律,指出华南地区Arening统的几丁虫自下向上可划分为Conochitinasymmetrica,Eremochitinabaculata,Eremochitinabrevis-Conochitinalangei,Conochitinapirum,Rhabdochitinaturgida等生物带。讨论了华南地区这一时期  相似文献   
94.
郴桂地区中大比例尺成矿预测的方法与效果   总被引:1,自引:0,他引:1  
曾昭健 《湖南地质》1996,15(4):221-226
郴桂地区是南岭多金属成矿带的重要地段,地质矿产工作研究程度较高,我院在此开展了大中比例尺成矿预测研究。本文扼要介绍了本区成矿预测的基本做法和预测方法,以及其主要成果和验证效果。  相似文献   
95.
陆相火山岩铜矿床成矿条件研究   总被引:1,自引:1,他引:1  
研究陆相火山岩铜矿床的成矿条件,对于多发现新的铜矿资源有着重要的意义。本文就陆相火山岩型铜矿床的实际存在,大陆玄武岩型铜矿的成矿系列,大陆裂谷的成矿环境和热液成矿作用等方面进行讨论。  相似文献   
96.
电吸附找矿方法寻找隐伏金矿床的研究   总被引:7,自引:0,他引:7  
电吸附找矿方法是指对采集的样品在室内特别装置中通电,并用吸附体吸附试样中电运移元素,通过这些元素所形成的异常来发现矿体的一种方法,该方法是依据野外地电提取方法的理论发展起来的,具有设备简单,成本低,工效效率高,工作条件及质量容易控制等优点。  相似文献   
97.
在管地贫硫银金矿床进行了近场源二极激电法的应用研究,获得了三高一低的次级低缓激电异常,即高ηs、R_2、Js,低ρs,表明用次级参数表示的激电弱异常要明显,为增加矿量,提高地质找矿效果起了积极作用。  相似文献   
98.
In many instances hydrogeological parameters obtained by conventional methods for selected localities within an aquifer or an aquitard are not sufficient for adequate regionalization at the scale of the entire layer. Here, we demonstrate an application of the fuzzy kriging method in regionalization of hydrogeological data, in which the set of conventional, crisp values is supplemented by imprecise information subjectively estimated by an expert. It is believed that such an approach eventually may reflect the real-world conditions more closely than a traditional crisp-value approach, because the former does not impose exactness artificially on phenomena which are diffuse by their nature. Spatial interpolation was done for the thickness of one of the major aquitards (till and glaciolacustrine clay) in northwestern Germany. The dataset consists of 329 crisp values from boreholes supplemented by 172 imprecise values defined as fuzzy numbers. It is demonstrated that the reliability of regionalization was higher, compared to regionalization performed with the crisp dataset only. Fuzzy kriging was performed with FUZZEKS (Fuzzy Evaluation and Kriging System) developed at the Ecosystem Research Center at the University of Kiel.  相似文献   
99.
Deep clays exhibit a pronounced strain anisotropy both during mechanical loading as well as during heating and cooling at constant stress in drained isotropic conditions. During mechanical loading vertical strain is larger than the horizontal one. During heating the vertical strain is larger than the horizontal one within the elastic range; the opposite is observed in the elasto-plastic range. The above described response can be interpreted adopting a consistent rotational, kinematic hardening thermo-elasto-plastic constitutive law.  相似文献   
100.
The HADES project (High Activity Disposal Experimental Site) aims at demonstrating the technical feasibility and the long-term safety of geological disposal of reprocessed HLW (High-Level Wastes) radioactive wastes. This disposal could be realised in the Tertiary Boom clay formation below the Mol/Dessel nuclear site. Previous studies in the 80's on the geomechanical behaviour of Boom clay, at host rock temperature (15°C), have demonstrated the mining capabilities of this clay. European partners have collaborated to increase the number of in-situ tests to be developed and operated from the Underground Research Facility (URF). Integrated large-scale experiments have been developed during the last four years, within the framework of the Commission of the European Communities (CEC) research contracts, in order to gain more insight into the thermal influence of heat-emiting wastes on the clay behaviour in the near field.

This paper summarizes the knowledge gained from the in-situ hydro-thermo-mechanical experiments realised from the URF. The objectives and main issues of the tests are described. Information regarding selection of parameters and representativeness of their measurements is discussed. Despite their different aims and designs, three hydro-thermo-mechanical experiments are compared in order to emphasize similarities in the general behaviour of the clay massif submitted to a thermal load. It is observed that its behaviour is qualitatively similar to the reaction upon a constant total stress increase. With the information now available, it is not obvious to draw conclusions with respect to the irreversibility of some phenomena.

Simple in-house analytical codes are able to simulate with a good accuracy the hydro-thermo-mechanical behaviour of clay. Nevertheless, these codes are not sufficient to describe the complexity of the phenomena that are involved in hydro-thermo-mechanical processes as pointed out by field data. In order to validate more complex models, the possibilities to improve the representativeness of the measurements are investigated.  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