全文获取类型
收费全文 | 9356篇 |
免费 | 1252篇 |
国内免费 | 590篇 |
专业分类
测绘学 | 1025篇 |
大气科学 | 509篇 |
地球物理 | 4869篇 |
地质学 | 1816篇 |
海洋学 | 455篇 |
天文学 | 116篇 |
综合类 | 470篇 |
自然地理 | 1938篇 |
出版年
2024年 | 47篇 |
2023年 | 95篇 |
2022年 | 214篇 |
2021年 | 236篇 |
2020年 | 276篇 |
2019年 | 345篇 |
2018年 | 304篇 |
2017年 | 349篇 |
2016年 | 381篇 |
2015年 | 380篇 |
2014年 | 466篇 |
2013年 | 548篇 |
2012年 | 465篇 |
2011年 | 479篇 |
2010年 | 424篇 |
2009年 | 490篇 |
2008年 | 525篇 |
2007年 | 452篇 |
2006年 | 477篇 |
2005年 | 428篇 |
2004年 | 395篇 |
2003年 | 346篇 |
2002年 | 320篇 |
2001年 | 295篇 |
2000年 | 296篇 |
1999年 | 277篇 |
1998年 | 318篇 |
1997年 | 252篇 |
1996年 | 241篇 |
1995年 | 244篇 |
1994年 | 155篇 |
1993年 | 140篇 |
1992年 | 98篇 |
1991年 | 81篇 |
1990年 | 57篇 |
1989年 | 58篇 |
1988年 | 67篇 |
1987年 | 24篇 |
1986年 | 21篇 |
1985年 | 21篇 |
1984年 | 31篇 |
1983年 | 6篇 |
1982年 | 13篇 |
1981年 | 6篇 |
1980年 | 10篇 |
1979年 | 14篇 |
1978年 | 7篇 |
1977年 | 11篇 |
1976年 | 2篇 |
1954年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Greenhouse gas emission mitigation plan for the State of Israel: strategies,incentives and reporting
Axel Michaelowa 《Climate Policy》2013,13(6):784-786
In the context of the negotiations under the United Nations Framework Convention on Climate Change and its accompanying Kyoto Protocol, participating nations have recognized the need for formulating Nationally Appropriate Mitigation Actions (NAMAs). These NAMAs allow countries to take into account their national circumstances and to construct measures to mitigate GHG emissions across economic sectors. Israel has declared to the UN that it would strive to reduce its GHG emissions by 20% in the year 2020 relative to a ‘business as usual' scenario. With its growing population and an expanding economy, the national GHG mitigation plan was developed to draw a course for steering the Israeli economy into a low-carbon future while accommodating continued economic growth. The article describes relevant policy measures, designed to aid in the implementation of the plan and compares them with measures being undertaken by different countries. Emphasis is placed on analysing the progress to date, opportunities and barriers to attaining the ultimate GHG emissions reduction goals. The objective of this article is to contribute to the knowledge base of effective approaches for GHG emissions reduction. We emphasize the integrated approach of planning and implementation that could be especially useful for developing countries or countries with economies in transition, as well as for developed countries. Yet, in the article we argue that NAMAs’ success hinges on structured tracking of progress according to emerging global consensus standards such as the GHG Protocol Mitigation Goals Standard.Policy relevance:The study is consistent with the NAMA concept, enabling a country to adopt a ‘climate action plan’ that contributes to its sustainable development, while enabled by technology and being fiscally sound.The analysis shows that although NAMAs have been framed in terms of projects, policies, and goals, current methodologies allow only the calculation of emission reductions that can be attributed to distinct projects. Currently, no international guidance exists for quantifying emissions reduction from policy-based NAMAs, making it difficult to track and validate progress. This gap could be addressed by an assessment framework that we have tested, as part of a World Resources Institute pilot study for an emerging voluntary global standard. 相似文献
993.
Integer aperture bootstrapping: a new GNSS ambiguity estimator with controllable fail-rate 总被引:1,自引:0,他引:1
P.J.G. Teunissen 《Journal of Geodesy》2005,79(6-7):389-397
In this contribution, we introduce a new bootstrap-based method for Global Navigation Satellite System (GNSS) carrier-phase ambiguity resolution. Integer bootstrapping is known to be one of the simplest methods for integer ambiguity estimation with close-to-optimal performance. Its outcome is easy to compute due to the absence of an integer search, and its performance is close to optimal if the decorrelating Z-transformation of the LAMBDA method is used. Moreover, the bootstrapped estimator is presently the only integer estimator for which an exact and easy-to-compute expression of its fail-rate can be given. A possible disadvantage is, however, that the user has only a limited control over the fail-rate. Once the underlying mathematical model is given, the user has no freedom left in changing the value of the fail-rate. Here, we present an ambiguity estimator for which the user is given additional freedom. For this purpose, use is made of the class of integer aperture estimators as introduced in Teunissen (2003). This class is larger than the class of integer estimators. Integer aperture estimators are of a hybrid nature and can have integer outcomes as well as non-integer outcomes. The new estimator is referred to as integer aperture bootstrapping. This new estimator has all the advantages known from integer bootstrapping with the additional advantage that its fail-rate can be controlled by the user. This is made possible by giving the user the freedom over the aperture of the pull-in region. We also give an exact and easy-to-compute expression for its controllable fail-rate. 相似文献
994.
995.
地震前兆复杂性成因机理研究的讨论(一):地震前兆复杂性的表现形式 总被引:8,自引:2,他引:8
通过国内外成功与失败的震例分析,介绍了地震前兆共性的一面,如在台网具有一定监测能力的地区,如果发生6级以上地震,震前总能或多或少地观测到异常现象。地震越大震前异常越多,分布越广,持续时间越长,异常幅度也较大,同时章着重对前兆复杂性的表现形式进行了较系统的归纳,整理,主要从以下几方面进行了分析,异常与地震关系的不确定性,主要表现在除了“有异常有地震”和“无异常无地震”的理论情况外,还存在“有异常无 相似文献
996.
Aftershock sequence simulations using synthetic earthquakes and rate-state seismicity formulation 下载免费PDF全文
Heming Xu Yifeng Cui James H. Dieterich Keith Richards-Dinger Efecan Poyraz Dong Ju Choi 《地震科学(英文版)》2014,27(4):401-410
We use an efficient earthquake simulator that incorporates rate-state constitutive properties and uses boundary element method to discretize the fault surfaces, to generate the synthetic earthquakes in the fault system. Rate-and-state seismicity equation is subsequently employed to calculate the seismicity rate in a region of interest using the Coulomb stress transfer from the main shocks in the fault system. The Coulomb stress transfer is obtained by resolving the induced stresses due to the fault patch slips onto the optimal-oriented fault planes. The example results show that immediately after a main shock the aftershocks are concentrated in the vicinity of the rupture area due to positive stress transfers and then disperse away into the surrounding region toward the background rate distribution. The number of aftershocks near the rupture region is found to decay with time as Omori aftershock decay law predicts. The example results demonstrate that the rate-and-state fault system earthquake simulator and the seismicity equations based on the rate-state friction nucleation of earthquake are well posited to characterize the aftershock distribution in regional assessments of earthquake probabilities. 相似文献
997.
阐述了如何利用地下水宏观异常作强烈地震的临震预报,详细叙述了利用地下水宏观异常预报地震三要素的方法。 相似文献
998.
对地震科技档案目前在收集、接收等常规管理中存在的问题和如何解决这些问题进行了详细论述。认为,只有实现了档案材料形成积累和收集整理过程的一体化,才可保障档案材料的齐全完整,实现依法管理。 相似文献
999.
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
1000.
葛秀珍 《前寒武纪研究进展》2012,(3):195-205
温室气体CO2的大量排放给全球气候和环境带来的巨大影响,受到了世界各国的关注。实现CO2的深度减排是人类可持续发展的必由之路。CO2地质储存是缓解碳排放行之有效的方法之一。本文通过以下几方面论述了国外CO2地质储存的现状以及对未来的展望:1)CO2捕集机理,2)CO2地质储存,3)CO2地质储存项目现状与未来预测,4)CO2地质储存场地储量评估,5)CO2地质储存监测技术,6)CO2地质储存模拟工具,7)CO2地质存储经费等。 相似文献