全文获取类型
收费全文 | 16093篇 |
免费 | 3108篇 |
国内免费 | 4069篇 |
专业分类
测绘学 | 1238篇 |
大气科学 | 3037篇 |
地球物理 | 4031篇 |
地质学 | 8545篇 |
海洋学 | 2125篇 |
天文学 | 627篇 |
综合类 | 1652篇 |
自然地理 | 2015篇 |
出版年
2024年 | 139篇 |
2023年 | 409篇 |
2022年 | 917篇 |
2021年 | 1064篇 |
2020年 | 903篇 |
2019年 | 957篇 |
2018年 | 1075篇 |
2017年 | 927篇 |
2016年 | 992篇 |
2015年 | 853篇 |
2014年 | 1075篇 |
2013年 | 1013篇 |
2012年 | 989篇 |
2011年 | 1008篇 |
2010年 | 1005篇 |
2009年 | 906篇 |
2008年 | 816篇 |
2007年 | 715篇 |
2006年 | 602篇 |
2005年 | 558篇 |
2004年 | 436篇 |
2003年 | 396篇 |
2002年 | 371篇 |
2001年 | 410篇 |
2000年 | 440篇 |
1999年 | 618篇 |
1998年 | 520篇 |
1997年 | 472篇 |
1996年 | 468篇 |
1995年 | 365篇 |
1994年 | 360篇 |
1993年 | 311篇 |
1992年 | 276篇 |
1991年 | 182篇 |
1990年 | 153篇 |
1989年 | 129篇 |
1988年 | 97篇 |
1987年 | 71篇 |
1986年 | 57篇 |
1985年 | 47篇 |
1984年 | 32篇 |
1983年 | 29篇 |
1982年 | 26篇 |
1981年 | 11篇 |
1980年 | 11篇 |
1979年 | 15篇 |
1978年 | 9篇 |
1977年 | 5篇 |
1975年 | 4篇 |
1958年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
201.
根据天山地区(42~44^oN,81~89^oE)1:20万,七探采集的900余个岩石样品的分析结果,基于全样本统计和迭代剔除方法,得到新疆天山地区表壳(出露地壳)的39种元素丰度值;对其中的SiO2、TiO2、Al2O3、TFe2O3、MgO、MnO、CaO、Na2O、K2O、P2O5 10种常量元素,按氧化物之和为100%进行归算。与全球大陆上地壳元素丰度值相比,天山地区表壳元素丰度富集SiO2、MnO和Ag、As、Hj、Sb元素,明显亏损CaO和。Be、Co、Cr、Ni、Mo、Sn,V、W等元素。从元素比值来看,该区表壳的Ba/La、K/La、K/Th、Nb/La、Th/La、Y/La值与全球大陆上地壳相应元素值相当;而K/Na、La/As、La/Sb值明显低于全球大陆上地壳。该区表壳化学成分相当于花岗闪长岩,同时表现出相对富钠和As、Sb元素的特征;这一地球化学特征与区内出露的表壳岩石主要是加里东期和海西期岛弧造山作用的产物有关,相对富钠的成分特征与岛弧岩浆活动中的Adakite质岩浆作用有关。 相似文献
202.
地球科学研究产生了大量的地球数据,其特点决定了地球数据共享的必要性。分析了网络化过程中地球数据共享存在的若干问题,介绍了XML Web Service及其相关技术.提出了基于XML Web Service的地球数据共享模型。在VS.NET中对XML Web Service在地球数据共享的应用进行了测试.指出XML Web Service是未来实现全球级的地球数据共享应用的理想选择。 相似文献
203.
Benjamin J. Kadlec David A. Yuen Xili L. Yang Evan F. Bollig Yunsong Wang Gordon Erlebacher Maxwell Rudolph 《Visual Geosciences》2004,9(1):61
We report here our experiences from using easily acquired web-cam components for collaborative ventures in the Earth sciences. We have used a variety of hardware and different software. We demonstrate from various locations in the U.S.A. the feasibility of using web-cam in multitudinous activities, relevant for conducting research and knowledge dissemination. We summarize the quality of the connections from the various combinations of communicating parties. Today, web-cams can be utilized as an economical and viable means of point-to-point communication in the Earth science community. Greater bandwidth is sorely needed for activities such as multi-party conferencing on the present internet network. We propose that web-cam can be readily deployed as a web-service for facilitating collaborative research over the GRID infrastructure, using the middleware Narada-Brokering. Web-cam will play an important role in the emerging field of geoinformatics. 相似文献
204.
Genesis of Kanggur Gold Deposit in Eastern Tianshan Orogenic Belt, NW China: Fluid Inclusion and Oxygen and Hydrogen Isotope Constraints 总被引:3,自引:0,他引:3
Abstract. Primary fluid inclusions in quartz and carbonates from the Kanggur gold deposit are dominated by aqueous inclusions, with subsidiary CO2 -H2 O inclusions that have a constant range in CO2 content (10–20 vol %). Microthermometric results indicate that total homogenization temperatures have a wide but similar range for both aqueous inclusions (120 to 310C) and CO2 -H2 O inclusions (140 to 340C). Estimates of fluid salinity for CO2 -H2 O inclusions are quite restricted (5.9∼10.3 equiv. wt% NaCl), whereas aqueous inclusions show much wider salinity ranging from 2.2 to 15.6 equivalent wt %NaCl.
The 6D values of fluid inclusions in carbonates vary from -45 to -61 %, in well accord with the published δD values of fluid inclusions in quartz (-46 to -66 %). Most of the δ18 O and δD values of the ore-forming fluids can be achieved by exchanged meteoric water after isotopic equilibration with wall rock by fluid/rock interaction at a low water/rock ratio. However, the exchanged meteoric water alone cannot explain the full range of δ18 O and δD values, magmatic and/or meta-morphic water should also be involved. The wide salinity in aqueous inclusions may also result from mixing of meteoric water and magmatic and/or metamorphic water. 相似文献
The 6D values of fluid inclusions in carbonates vary from -45 to -61 %, in well accord with the published δD values of fluid inclusions in quartz (-46 to -66 %). Most of the δ
205.
北京延庆北部地区后城组火山岩岩石化学特征与成因探讨 总被引:3,自引:0,他引:3
根据TAS图解 ,北京延庆北部地区后城组火山属于玄武粗安岩 流纹岩 (和粗面岩 )的双峰式组合。该套火山岩不属于典型的钾玄岩系列 ,在基性岩和中性岩中总体上以碱性系列和向碱性系列过渡的高钾钙碱性系列、钾玄岩系列为主 ,流纹岩类属于富钾质的拉斑系列。该套火山岩轻稀土元素明显富集。玄武粗安岩类岩石没有负铕异常或负铕异常不明显 ,而流纹岩存在明显的负铕异常。延庆北部地区后城组火山岩形成于燕山运动早期或中期阶段的造山变形事件趋于结束时的后碰撞构造环境中。 相似文献
206.
数字地质编录中坡面展示影像图的制作研究 总被引:2,自引:0,他引:2
基于影像的数字地质编录是摄影测量和工程地质学科边缘交叉发展的技术成果之一.目前仍处于研究阶段。介绍了影像数字地质编录中坡面展示影像图的制作原理及其流程,重点阐述了畸变校正后像片坡面影像几何纠正的两种不同的处理方法。实践表明,两种处理方法的结合能够很好地满足数字地质编录中对展示影像图的生成及使用的要求。 相似文献
207.
在信息传播媒体的竞争日益严酷的时代,面对天气预报节目只依靠简单的画面加解说,拉洋片式传统方法这样一种一成不变的局面,策划创意制作出《天气资讯》节目,打破天气预报节目以往的节目形式和播出形式,以极少的投入获得最大的社会效益和经济效益。 相似文献
208.
C. Hsein Juang Haiming Yuan David Kun Li Susan Hui Yang Raymond A. Christopher 《Soil Dynamics and Earthquake Engineering》2005,25(5):403-411
An empirical procedure for estimating the severity of liquefaction-induced ground damage at or near foundations of existing buildings is established. The procedure is based on an examination of 30 case histories from recent earthquakes. The data for these case histories consist of observations of the damage that resulted from liquefaction, and the subsurface soil conditions as revealed by cone penetration tests. These field observations are used to classify these cases into one of three damaging effect categories, ‘no damage’, ‘minor to moderate damage’, and ‘major damage’. The potential for liquefaction-induced ground failure at each site is calculated and expressed as the probability of ground failure. The relationship between the probability of ground failure and the damage class is established, which allows for the evaluation of the severity of liquefaction-induced ground damage at or near foundations. The procedure presented herein represents a significant attempt to address the issue of liquefaction effect. Caution must be exercised, however, when using the proposed model and procedure for estimating liquefaction damage severity, because they are developed based on limited number of case histories. 相似文献
209.
210.
SHA Liqing ZHENG Zheng TANG Jianwei Wang Yinghong ZHANG Yiping CAO Min WANG Rui Liu Guangren WANG Yuesi SUN Yang 《中国科学D辑(英文版)》2005,48(Z1)
With the static opaque chamber and gas chromatography technique, from January 2003 to January 2004 soil respiration was investigated in a tropical seasonal rain forest in Xishuangbanna, SW China. In this study three treatments were applied, each with three replicates: A (bare soil), B (soil+litter), and C (soil+litter+seedling). The results showed that soil respiration varied seasonally, low from December 2003 to February 2004, and high from June to July 2004. The annual average values of CO2 efflux from soil respiration differed among the treatments at 1% level, with the rank of C (14642 mgCO2· m-2. h-1)>B (12807 mgCO2· m-2. h-1)>A (9532 mgCO2· m-2. h-1). Diurnal variation in soil respiration was not apparent due to little diurnal temperate change in Xishuangbanna. There was a parabola relationship between soil respiration and soil moisture at 1% level. Soil respiration rates were higher when soil moisture ranged from 35% to 45%. There was an exponential relationship between soil respiration and soil temperature (at a depth of 5cm in mineral soil) at 1% level. The calculated Q1o values in this study,ranging from 2.03 to 2.36, were very near to those of tropical soil reported. The CO2 efflux in 2003was 5.34 kgCO2· m-2. a-1 from soil plus litter plus seedling, of them 3.48 kgCO2· m-2. a-1 from soil (accounting for 62.5%), 1.19 kgCO2· m-2. a-1 from litter (22.3%) and 0.67 kgCO2·m-2. a-1 from seedling (12.5%). 相似文献