全文获取类型
收费全文 | 7098篇 |
免费 | 1071篇 |
国内免费 | 2257篇 |
专业分类
测绘学 | 69篇 |
大气科学 | 875篇 |
地球物理 | 1166篇 |
地质学 | 1877篇 |
海洋学 | 5483篇 |
天文学 | 33篇 |
综合类 | 448篇 |
自然地理 | 475篇 |
出版年
2024年 | 18篇 |
2023年 | 70篇 |
2022年 | 247篇 |
2021年 | 246篇 |
2020年 | 259篇 |
2019年 | 265篇 |
2018年 | 264篇 |
2017年 | 285篇 |
2016年 | 255篇 |
2015年 | 309篇 |
2014年 | 480篇 |
2013年 | 494篇 |
2012年 | 337篇 |
2011年 | 468篇 |
2010年 | 363篇 |
2009年 | 614篇 |
2008年 | 534篇 |
2007年 | 559篇 |
2006年 | 479篇 |
2005年 | 489篇 |
2004年 | 396篇 |
2003年 | 376篇 |
2002年 | 391篇 |
2001年 | 301篇 |
2000年 | 277篇 |
1999年 | 257篇 |
1998年 | 208篇 |
1997年 | 204篇 |
1996年 | 170篇 |
1995年 | 144篇 |
1994年 | 140篇 |
1993年 | 117篇 |
1992年 | 100篇 |
1991年 | 73篇 |
1990年 | 41篇 |
1989年 | 62篇 |
1988年 | 21篇 |
1987年 | 17篇 |
1986年 | 11篇 |
1985年 | 20篇 |
1984年 | 17篇 |
1983年 | 12篇 |
1982年 | 11篇 |
1981年 | 17篇 |
1978年 | 6篇 |
1954年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 107 毫秒
51.
南黄海灾害性地质研究 总被引:2,自引:0,他引:2
本文研完了南黄海10种灾害地质因素的性质、危害性及分布,对其进行了分类,在此基础上对本区之灾害地质进行了区划和评价。 相似文献
52.
Abstract. The secondary production of Spisula subtruncata (somatic production) is calculated in the framework of a benthic monitoring study in a coastal area. The temporal trends of density, biomass and growth increments are examined in the three year-classes present. These are compared to certain physical and chemical parameters. 相似文献
53.
Erling K. Stenevik Webjrn Melle Eilif Gaard Astthor Gislason Cecilie T.. Broms Irina Prokopchuk Bjrnar Ellertsen 《Deep Sea Research Part II: Topical Studies in Oceanography》2007,54(23-26):2672
Egg production of Calanus finmarchicus was studied during joint basin-scale surveys in April–June 2003 in the Norwegian Sea. Surveys covered the whole Norwegian Sea and were conducted from Norwegian, Icelandic and Faroese research vessels. Stations were classified as being in pre-bloom, bloom or post-bloom phase according to levels of chlorophyll a and nitrate. Individual egg production rates and population egg production rates were calculated and compared between areas. Both individual egg production rates (eggs female−1 day−1) and population egg production rates (eggs m−2 day−1) were significantly higher in bloom areas compared with pre-bloom and post-bloom areas. However, when integrated over an estimated duration of the three phases, the time-integrated egg production (eggs m−2) in most years was highest in the pre-bloom phase, and this was explained by the longer duration of this phase compared with the two other phases. 相似文献
54.
南海区重点岸段海岸侵蚀现状成因分析与防治对策 总被引:4,自引:0,他引:4
在2003年与2006年对南海区琼州海峡两岸重点岸段(雷州市徐闻县龙塘镇赤坎村岸段、海南省海口市镇海村岸段和新海村岸段)的海岸侵蚀进行了现场监测,测量了侵蚀的长度、宽度和面积。对两年现场测量结果进行比较分析,结果表明:海岸侵蚀长度的平均速度为200m/a,宽度的平均速度为20m/a,面积的平均速度为4000m2/a。应用了地质分析、水动力分析、极端海洋气候影响分析等新的理论和方法重点分析了海岸侵蚀的成因,并提出了一些对策,供相关部门参考。 相似文献
55.
The expansion of offshore activities and the increasing need to meet international and national commitments to biodiversity conservation have led to an enhanced interest in marine spatial planning (MSP) as a tool for sea use management. Several European countries, on their own initiative or driven by European legislation and policy, have taken global leadership in implementing MSP. This article will discuss the Belgian experiences with MSP. It will give a short historical overview based on legal developments and review the implementation process of a ‘Master Plan’ as a spatial management policy for the Belgian Part of the North Sea. Additionally, this article will reflect on the research that has been done in Belgium to apply a land-use planning approach to the marine environment. The MSP process in Belgium shows that a spatial approach to sea use management is possible despite the lack of a legal zoning framework. However, it concludes that a legal basis for MSP, in addition to the current permit system, would provide a more strategic and integrated framework for ecosystem-based, sea use management. 相似文献
56.
57.
58.
Seasonal abundance and distribution of pelagic tunicates (Chordata: Thaliacea) in the central South China Sea 总被引:2,自引:1,他引:2
1IntroductionTunicates(Chordata:Thaliacea)are large pe-lagic gelatinous zooplankton.They can be used as in-dicator species for ocean currents and water bodies(Chen et al.,1980;Chen et al.,1988;Lin,1988,1990;Lin and Zhang,1993;Thompson,1948).They also play… 相似文献
59.
This study is devoted to oceanographic features of the semi-enclosed Gulf of Aqaba, Red Sea. The data were recorded in winter—spring
1999 on the R/V Meteor cruise leg 44/2. Temperature and salinity profiles were measured at six positions (I—VI). The shipboard
NarrowBand Acoustic Doppler Current Profiler (NB ADCP) 150 kHz continuously recorded current profiles down to 350 m en route.
The research revealed that the current near the Strait of Tiran front (position VI) represents a semidiurnal signal of an
internal tide wave (∼12 h period; 0.2 ms−1 amplitude) that might be generated by the barotropic tide at the sill of the Strait. A sequence of cyclonic and anticyclonic
eddy pairs is found along the axis of the Gulf of Aqaba during winter-spring seasons. These sub-mesoscale signals are dominant
above the main thermocline and might be caused by wind forcing and the narrowness of the Gulf; it might remain in other seasons
with different dimensions in relation to the depth of thermocline. The total diameter of each pair was twice the baroclinic
Rossby radius (R ≈ 10 km). A single anti-cyclonic eddy was observed in the upper 300 m in the northern tip of the Gulf with a diameter of
about 5–8 km. 相似文献
60.
尝试性地将南黄海灾害地质因素分为4大类。同时参考地貌沉积界线和其他因素将南黄海分成4个灾害地质区:即海岸带、苏北浅滩、海州湾和南黄海东部灾害地质区,并时各灾害地质区进行了定性评价,苏北浅滩灾害地质区是研究区内灾害地质环境最不稳定的区域。 相似文献