全文获取类型
收费全文 | 230篇 |
免费 | 23篇 |
国内免费 | 80篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 5篇 |
地球物理 | 78篇 |
地质学 | 60篇 |
海洋学 | 153篇 |
综合类 | 22篇 |
自然地理 | 13篇 |
出版年
2024年 | 8篇 |
2023年 | 15篇 |
2022年 | 16篇 |
2021年 | 12篇 |
2020年 | 12篇 |
2019年 | 13篇 |
2018年 | 13篇 |
2017年 | 9篇 |
2016年 | 5篇 |
2015年 | 5篇 |
2014年 | 16篇 |
2013年 | 15篇 |
2012年 | 15篇 |
2011年 | 20篇 |
2010年 | 9篇 |
2009年 | 16篇 |
2008年 | 16篇 |
2007年 | 12篇 |
2006年 | 12篇 |
2005年 | 11篇 |
2004年 | 11篇 |
2003年 | 4篇 |
2002年 | 10篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 7篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 7篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1982年 | 2篇 |
排序方式: 共有333条查询结果,搜索用时 62 毫秒
81.
A web-based distributed system for monitoring and forecasting of the marine environment has been developed in line with INfrastructure for SPatial InfoRmation in Europe (INSPIRE) and Global Monitoring for Environment and Security (GMES) recommendations for a European Spatial Data Infrastructure (SDI). This system, called DISPRO, enables integration and distribution of multi-source data from satellites, aircraft, and in situ instruments, as well as results from numerical models. Geographic data and metadata are stored on a set of distributed computer nodes and retrieved and integrated by a web GIS client by means of Open Geospatial Consortium (OGC) Web Map Server (WMS) technologies. A profile of ISO 19115 was developed for metadata handling, using eXtensible Markup Language (XML) as a platform independent encoding mechanism. DISPRO has been demonstrated in six European coastal zone and ocean regions in the spring and summer of 2005. The overall positive experiences of both service providers and end users indicate that the system should be further developed into an operational GMES service. 相似文献
82.
台湾海峡小型浮游动物的摄食对夏季藻华演替的影响 总被引:3,自引:2,他引:3
于2004年8月1~6日对台湾海峡南部近岸的藻华过程进行了定点连续跟踪观测,用稀释法研究了浮游植物的生长率和小型浮游动物对浮游植物的摄食死亡率,同时运用高效液相色谱(HPLC)技术,分析了浮游植物不同光合色素类群的生长率和摄食死亡率.结果表明,观测期间处于藻华的消退期.8月1日时,浮游植物生物量(叶绿素a)和丰度分别为2.04μg/dm3和2.99×105个/dm3,主要优势种为尖刺伪菱形藻(Pseudo-nitzschia pungens)、冰河拟星杆藻(Asterionellopsis glacialis)和中肋骨条藻(Skeletonema costatum),8月6日时,浮游植物生物量和丰度分别减为0.37μg/dm3和1.54×104个/dm3;而蓝藻和甲藻的丰度和比例则呈现出逐渐增加的趋势,所占的比重分别从1日的0.04%和0.85%增加到6日的9.59%和41.97%.小型浮游动物主要由无壳纤毛虫、砂壳纤毛虫、红色中缢虫(Mesodinium rubrum)和异养甲藻等类群组成,总丰度于8月2日达到最大值,为3640个/dm3,之后逐渐减少,6日时,仅为436个/dm3.观测期间,小型浮游动物在群落组成上虽一直以无壳纤毛虫和异养甲藻为主,但在具体的类群结构上却表现出了一定的差异,30μm以下的无壳纤毛虫和异养甲藻总体呈下降的趋势,而红色中缢虫、砂壳纤毛虫和大于50μm的无壳纤毛虫总体呈增加的趋势.观测期间,浮游植物的生长率为0.40~0.91d-1,小型浮游动物的摄食率为0.26~1.34d-1,摄食率和生长率总体呈逐渐下降的趋势.结果还表明,小型浮游动物的摄食率与叶绿素a具有很好的相关性(R2=0.89),对各光合色素类群的现存量和初级生产力均具有较高的摄食压力(分别为37.97%~82.24%和70.71%~281.33%),是藻华消亡的重要原因之一;此外,小型浮游动物对甲藻和蓝藻的避食行为,可能是观测期间由“硅藻”水华向“硅藻-甲藻”水华转变的重要原因之一. 相似文献
83.
84.
酒泉盆地油气勘探始于20世纪20年代,先后发现了老君庙、鸭儿峡、单北、白杨河等油田。盆地在中、新生代经历了早白垩世断陷盆地演化阶段和新生代前陆盆地演化阶段,为断拗叠置型盆地。断陷期的酒泉盆地下白垩统赤金堡组和下沟组为一套纹层状泥质白云岩和白云质泥岩,藻纹层比较发育,是优质的烃源岩。拗陷期盆地的快速沉降导致烃源岩快速成熟、高效生烃,为油气运移提供了动力,同时挤压逆冲对构造圈闭、油气运移通道的形成和储层物性的改善起着关键的作用,形成的窟窿山等多个正向构造带是油气富集的有利区带。青西凹陷存在低成熟、成熟、高成熟3类原油,低成熟原油仅分布于青西凹陷的下沟组上段至中沟组,成熟原油发生了大规模的运移,形成了柳沟庄、鸭儿峡—老君庙—石油沟油田,而深层高成熟原油没有大规模向中浅层运移,青西凹陷具有寻找高成熟原油的资源潜力。希望该研究成果可为青西凹陷下白垩统油气勘探提供经验与思路。 相似文献
85.
Aridgides LJ Doblin MA Berke T Dobbs FC Matson DO Drake LA 《Marine pollution bulletin》2004,48(11-12):1096-1101
There is enormous potential for global transfer of microorganisms, including pathogens, in ships' ballast water. We contend that a major advancement in the study of ballast-water microorganisms in particular, and of aquatic pathogens in general, will be expedited sample analysis, such as provided by the elegant technology of DNA microarrays. In order to use DNA microarrays, however, one must establish the appropriate conditions to bind target sequences in samples to multiple probes on the microarrays. We conducted proof-of-concept experiments to optimize simultaneous detection of multiple microorganisms using polymerase chain reaction (PCR) and Southern hybridization. We chose three target organisms, all potentially found in ballast water: a calicivirus, the bacterium Vibrio cholerae, and the photosynthetic protist Aureococcus anophagefferens. Here, we show simultaneous detection of multiple pathogens is possible, a result supporting the promising future use of microarrays for simultaneous detection of pathogens in ballast water. 相似文献
86.
在柴达木盆地发育了各种类型的渐新世—中新世湖相叠层石,其中丘状叠层石具有重要的地质意义,丘状叠层石直接生长在砾岩上,并向上逐渐演化为藻礁,藻礁向上又重新转化为叠层石沉积。通过对内部纹层特征和沉积组分的研究并结合叠层石的同位素、地球化学以及古生物资料分析表明,微生物自身的钙化作用以及微生物引发的沉淀作用形成了这种具有典型内部纹层的丘状叠层石。较高的温度、炎热和干燥的气候条件、坚硬的基底以及较少的藻类干扰作用是叠层石生成的主要因素。总体上,叠层石形成于较为低能的环境中,与高能环境中所形成的藻礁完全不同,而且两者具有明显的相互竞争作用。因此,与气候和水体条件密切相关的后生生物的生长和真核藻类的发育是叠层石在显生宙迅速衰落的主要因素。 相似文献
87.
88.
Two coal-bearing units from the Lower Carboniferous succession in Central Spitsbergen, Svalbard, have been investigated using coal petrographic and geochemical techniques. The upper member consists mainly of algal cannels, dominated by Botryococcus-type algae. The coals from the lower member are a mixture of durite-type coals with sporinite and inertinite and coals containing prdominantly vitrinite. The Rock-Eval and pyrolysis-GC also show a clear distinction in the composition of the organic matter in the two coal-bearing units investigated. These results, together with detailed sedimentological analyses, are used to reconstruct the depositional environments for the two coal-bearing sequences. 相似文献
89.
燕辽地区中、晚元古代宏观藻类化石研究 总被引:2,自引:0,他引:2
以蓟县中、上元古界层型剖面所产宏观藻类化石为重点 ,兼顾京冀辽等邻区 ,全面总结和系统讨论了该区中、晚元古代宏观藻类化石的研究简史、产出层位、区域分布、化石组合、生物群特征、可能的系统分类 ,以及国内外对比与地层学意义 ,初步探讨了宏观藻类植物群在中、新元古代的发生、发展与更迭 ,追索宏观真核生物起源等。通过对燕辽地区中、新元古代宏观藻类的研究与总结 ,把显生宙行之有效的生物地层学方法运用于前寒武纪地层研究中 ,进行国内外前寒武纪地层的对比 ,显然具有重要的地层学意义。同时 ,对探讨地球早期生命演化也具有重要的理论意义 相似文献
90.
The distribution of organic carbon (OC) and of some metals (Cu, Mn) amongst the particulate (>0·2 μm), colloidal (10 kDa–0·2 μm) and the truly dissolved (<10 kDa) fractions of the River Marne was investigated during the phytoplankton spring bloom. A tangential ultrafiltration (UF) device was utilized to separate the colloidal fraction. On average, 22% of the OC, 31% of the Cu and 53% of the Mn, usually assigned to the so‐called dissolved fraction, were found in the colloidal fraction. The colloidal fraction exhibited a behaviour different from that of the particulate and truly dissolved fractions. Autochthonous production led to enrichment in the colloidal and particulate OC pools: up to 47% of the total dissolved OC was in the colloidal fraction. An increase in the colloidal metal fraction, concomitant with a fall in the truly dissolved fraction, coincided with peaks in phytoplankton during the bloom. These phenomena might be related either to an increase in pH associated with photosynthetic activity, resulting in the precipitation of truly dissolved forms into the colloidal fraction, or to scavenging of the truly dissolved metals by the algal species of colloidal size. The interaction between the colloidal and the truly dissolved phases was very important. The partition coefficients of the Cu and Mn between the colloidal and truly dissolved fractions were higher than between the particulate and the truly dissolved fractions. This pattern is consistent with a greater specific surface area of colloids than macroparticles. Consequently, the adsorption and complexation capacities are enhanced in the colloidal fraction of the particulate matter. The extraction of hydrophobic complexes with Cu using C18 Sep‐Pak columns, showed that the Cu occurring in colloidal, total dissolved or truly dissolved forms was significantly complexed by the organic matter. The truly dissolved fraction might be complexed up to 100% during a phytoplankton bloom. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献