全文获取类型
收费全文 | 13432篇 |
免费 | 2580篇 |
国内免费 | 2488篇 |
专业分类
测绘学 | 2598篇 |
大气科学 | 3208篇 |
地球物理 | 2710篇 |
地质学 | 5484篇 |
海洋学 | 1584篇 |
天文学 | 712篇 |
综合类 | 1146篇 |
自然地理 | 1058篇 |
出版年
2024年 | 97篇 |
2023年 | 400篇 |
2022年 | 536篇 |
2021年 | 605篇 |
2020年 | 390篇 |
2019年 | 625篇 |
2018年 | 353篇 |
2017年 | 359篇 |
2016年 | 363篇 |
2015年 | 529篇 |
2014年 | 925篇 |
2013年 | 711篇 |
2012年 | 924篇 |
2011年 | 941篇 |
2010年 | 829篇 |
2009年 | 983篇 |
2008年 | 1278篇 |
2007年 | 874篇 |
2006年 | 752篇 |
2005年 | 911篇 |
2004年 | 760篇 |
2003年 | 799篇 |
2002年 | 708篇 |
2001年 | 525篇 |
2000年 | 411篇 |
1999年 | 283篇 |
1998年 | 185篇 |
1997年 | 209篇 |
1996年 | 144篇 |
1995年 | 169篇 |
1994年 | 170篇 |
1993年 | 143篇 |
1992年 | 117篇 |
1991年 | 80篇 |
1990年 | 79篇 |
1989年 | 80篇 |
1988年 | 31篇 |
1987年 | 30篇 |
1986年 | 15篇 |
1985年 | 30篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 16篇 |
1981年 | 9篇 |
1980年 | 12篇 |
1965年 | 9篇 |
1961年 | 6篇 |
1960年 | 7篇 |
1958年 | 5篇 |
1954年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
881.
882.
Microsatellite markers have become one kind of the most important molecular tools used in various researches. A large number of microsatellite markers are required for the whole genome survey in the fields of molecular ecology, quantitative genetics and genomics. Therefore, it is extremely necessary to select several versatile, low-cost, efficient and time- and labor-saving methods to develop a large panel of microsatellite markers. In this study, we used Zhikong scallop (Chlamys farreri) as the target species to compare the efficiency of the five methods derived from three strategies for microsatellite marker development. The results showed that the strategy of constructing small insert genomic DNA library resulted in poor efficiency, while the microsatellite-enriched strategy highly improved the isolation efficiency. Although the mining public database strategy is time- and cost-saving, it is difficult to obtain a large number of microsatellite markers, mainly due to the limited sequence data of non-model species deposited in public databases. Based on the results in this study, we recommend two methods, microsatellite-enriched library construction method and FIASCO-colony hybridization method, for large-scale microsatellite marker development. Both methods were derived from the mi-crosatellite-enriched strategy. The experimental results obtained from Zhikong scallop also provide the reference for microsatellite marker development in other species with large genomes. 相似文献
883.
唐鹰 《国土资源导刊(湖南)》2009,6(7):92-94
[编者按]2009年3月27日,国土资源部颁发<关于印发开展地质找矿改革发展大讨论工作方案的通知>,决定集中半年时间,广泛深入地开展多层面、多领域的地质找矿改革发展大讨论.这是对日渐紧张以及某些稀有资源被大肆而无序地开采导致枯竭的一种拯救,也是对人类可持续发展的一种探索,同时,对构建地质找矿的新机制的形成也是有力的支持. 相似文献
884.
《山东国土资源》2009,25(7):64-65
记者22日从国土资源部广州海洋地质调查局获悉,我国“海洋四号”科考船近日采用新研制的“气密性孔隙水原位采样系统”,首次在南海中央海盆4000多米深水水域海底成功获取孔隙水样品。这标志着我国对可燃冰的深海探测技术又取得了新的突破。“气密性孔隙水原位采样系统”由多个高强度抗腐蚀金属材料气密容器纵向排列,通过水下计算机实现对孔隙水采样的全自动监控和采集。该系统近日搭载于“海洋四号”科考船进行海上试验,其最大工作水深超过4000m,沉积物采样深度大于5m,可同时采集11个层位的孔隙水,系统仅在海底停留5分钟,每个层位采水量皆超过100mL,共采集孔隙水1198mL, 相似文献
885.
Requirements for monitoring the coastal zone environment are first summarized. Then the application of hyperspectral remote sensing to coast environment investigation is introduced, such as the classification of coast beaches and bottom matter, target recognition, mine detection, oil spill identification and ocean color remote sensing. Finally, what is needed to follow on in application of hyperspectral remote sensing to coast environment is recommended. 相似文献
886.
A fully nonlinear numerical model based on a time-domain higher-order boundary element method (HOBEM) is founded to simulate the kinematics of extreme waves. In the model, the fully nonlinear free surface boundary conditions are satisfied and a semi-mixed Euler-Lagrange method is used to track free surface; a fourth-order Runga-Kutta technique is adopted to refresh the wave elevation and velocity potential on the free surface at each time step; an image Green function is used in the numerical wave tank so that the integrations on the lateral surfaces and bottom are excluded. The extreme waves are generated by the method of wave focusing. The physical experiments are carried out in a wave flume. On the horizontal velocity of the measured point, numerical solutions agree well with experimental results. The characteristics of the nonlinear extreme-wave kinematics and the velocity distribution are studied here. 相似文献
887.
The geological-geophysical map series of the eastern China seas and adjacent region (1:1 000 000) will be published in the late half year of 2009. The regional tectonic map is one of the main professional maps. The Mapping methods, the division method of geological tectonic units and the main geological tectonic units are mainly discussed. The strata from Pliocene to Holocene are peeled off so as to display the Pre-Pliocene structures. In basins, isopaches are drawn for the Cenozoic deposits. The plate tectonic theory and present tectonic pattern are adopted as the priorities in tectonic division. As to the division of intraplate tectonic units, it is a revision, complement and improvement of previous dividing systems, and the nomenclature for each tectonic unit follows the current system in China. The first-order tectonic unit is plate (Pacific Plate, Eurasian Plate and Philippine Sea Plate). The second-order tectonic unit is tectonic domain (East Asian continental tectonic domain,East Asian continental margin tectonic domain and west Pacific tectonic domain). The Philippine Sea Plate and the west part of the Pacific Plate are called the West Pacific tectonic domain. The part of the Eurasian Plate involved in this study area can be further divided into East Asian continental tectonic domain and East Asian continental margin tectonic domain. The East Asian continental margin domain is composed of the Ryukyu island arc, the Okinawa Trough back-arc basin and the back-arc basin of Sea of Japan. The East Asian continental tectonic domain in this study area is composed of the Sino-Korea Massif, the Changjiang River (Yangtze) Massif and South China Massif. In turn, these massifs consist of basins, folded belts or uplift zones. The basins,the folded belts or the uplift zones are further divided into uplifts and depressions made up of sags and swells. 相似文献
888.
889.
890.