全文获取类型
收费全文 | 1301篇 |
免费 | 295篇 |
国内免费 | 506篇 |
专业分类
测绘学 | 271篇 |
大气科学 | 257篇 |
地球物理 | 300篇 |
地质学 | 659篇 |
海洋学 | 312篇 |
天文学 | 13篇 |
综合类 | 131篇 |
自然地理 | 159篇 |
出版年
2024年 | 7篇 |
2023年 | 28篇 |
2022年 | 96篇 |
2021年 | 114篇 |
2020年 | 77篇 |
2019年 | 84篇 |
2018年 | 90篇 |
2017年 | 68篇 |
2016年 | 72篇 |
2015年 | 100篇 |
2014年 | 101篇 |
2013年 | 82篇 |
2012年 | 109篇 |
2011年 | 108篇 |
2010年 | 115篇 |
2009年 | 114篇 |
2008年 | 109篇 |
2007年 | 97篇 |
2006年 | 107篇 |
2005年 | 69篇 |
2004年 | 90篇 |
2003年 | 42篇 |
2002年 | 38篇 |
2001年 | 38篇 |
2000年 | 36篇 |
1999年 | 19篇 |
1998年 | 12篇 |
1997年 | 18篇 |
1996年 | 16篇 |
1995年 | 10篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1984年 | 2篇 |
1981年 | 1篇 |
1979年 | 3篇 |
1964年 | 1篇 |
1957年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有2102条查询结果,搜索用时 15 毫秒
1.
2.
Study of zooplankton ecology in Zhejiang coastal upwelling system-Species distribution and diversity of zooplankton 总被引:2,自引:0,他引:2
The species distribution and diversity of zooplankton and the effects of hydrodynamic factors of Zhejiang coastal waters during the active period of upwelling are discussed.High dominance (low diversity), high biomass and short food chain were found in the landward margins of the central region of the upwelling. There were evident interactions between the distribution of zooplankton and the environmental factors. The expression of these interactions is that different ecotypes of zooplankton adapt to different hydrological situations. There is significant positive correlation between the diversity indices of zooplankton and the mean water temperature in the survey area. It is noted that the vertical distribution of Calanus sinicus indicates to a certain extent the colder water environment of the upwelling (Fig. 7, Table 2, Reference (Hargreaves, 1981). 相似文献
3.
不同浓度的营养盐(NO3-N,PO4-P)条件下Pb(Ⅱ)对2种海洋赤潮藻生长影响的研究 总被引:6,自引:2,他引:6
探讨海区环境容量的估算,为海水水质标准的制订提供理论依据,采用1次培养实验方法,研究了3种不同浓度的营养盐(NO3-N,PO4-P)条件下Pb(Ⅱ)对旋链角毛藻(Chaetoceroscurvisetus)、中肋骨条藻(Skeletonemacostatum(Greville)Cleve)的生长影响.采用抑制率-重金属离子浓度的对数方程拟合求算出3种浓度营养盐(NO3-N、PO4-P)条件下Pb(Ⅱ)对2种赤潮藻的96hEC50值,分别为8373,2563,2307;18523,10445,3494μg·dm-3,并根据方程应用origin7.0拟合3种不同浓度的营养盐(NO3-N,PO4-P)条件下旋链角毛藻和中肋骨条藻在不同浓度Pb(Ⅱ)条件下的生长曲线.实验结果表明,较低浓度Pb(Ⅱ)对旋链角毛藻和中肋骨条藻生长都有一定的促进作用,最佳促进藻类生长浓度分别为454,258,51;351,194,35μg·dm-3;高浓度Pb(Ⅱ)对它们的生长则表现为抑制作用,并且随着营养盐(NO3-N,PO4-P)浓度的增加,Pb(Ⅱ)对两种赤潮藻生长的抑制作用是逐渐降低的,营养盐(NO3-N,PO4-P)与Pb(Ⅱ)之间可能存在着拮抗作用. 相似文献
4.
5.
Study of zooplankton ecology in Zhejiang coastal upwelling system-Zooplankton biomass and abundance of major groups 总被引:1,自引:0,他引:1
He Dehu Yang Guanming Fang Shaojin Shen Weilin Liu Hongbin Gao Aigen Huang Shuxin 《海洋学报(英文版)》1988,7(4):607-620
The studied area is a shallow water area that belongs to the East China Sea continent shelf. The distribution of zooplankton biomass is higher inshore than offshore. The maximum abundance is in the inshore edge of the centre of upwelling, which is the superposed area of the salinity front and temperature front, due to the fact that the mixture of three different waters has brought about a concentration of nutrients. The herbivorous Euphausia, Copepoda and Tunicata are the major groups of the abundant area. Tunicata possess the possibility to compete against other kinds of herbivorous zooplankton. This means that there is negative correlation between the distribution of Tunicata and that of Copepoda and Euphausia. The positions of maximum areas of zooplankton biomass, phytoplankton individual and the concentration of phosphates and chlorophyll-a overlap one another. In the centre of upwelling, zooplankton can not adapt itself to the environment of lower temperature and less oxygen even with rich nutrient 相似文献
6.
The mixing characteristics of particles such as dredged sediment of variable size discharged into cross flow are studied by a 3D numerical model, which is developed to model the particle-fluid two-phase flow. The Eulerian method with the modified k-ε parameterization of turbulence for the fluid phase is used to solve fluid phase, while a Lagrangian method for the solid phase (particles), both the processes are coupled through the momentum sources. In the model the wake turbulence induced by particles has been included as additional source term in the k-ε model; and the variable drift velocities of the particles are treated efficiently by the Lagrangian method in which the particles are tracked explicitly and the diffusion process is approximated by a random walk model. The hydrodynamic behavior of dumping a cloud of particles is governed by the total buoyancy of the cloud, the drag force on each particle and the velocity of cross-flow. The computed results show a roughly linear relationship between the displacement of the frontal position and the longitudinal width of the particle cloud. The particle size in the cloud and the velocity of cross flow dominate the flow behavior. The computed results are compared with the results of laboratory experiments and satisfactory agreement is obtained. 相似文献
7.
A study on zooplankton distribution patterns and indicator species in Kuroshio upstream area and adjacent East China Sea 总被引:3,自引:0,他引:3
On the basis of the data of zooplankton biomass and three major taxa—— Copepoda, Chaetognatha andSiphonophora of May-June 1986, July-August and December 1987, the distributional patterns and the indicator species of zooplankton in the Kuroshio and adjacent waters of the East China Sea are preliminarily studied. The results are as follows:The horizontal distribution of zooplankton biomass and the abundance of copepods, chaetognaths and siphonophores arecurred in the continent area northwest of Taiwan and the south-centre section of the East China Sea continent, which are the mix front of different waters. Zooplankton in the water area inside of Ryukyu Islands presented low abundance and high diversity. There are clear seasonal variations in zooplankton biomass and abundance in the study area. The strength or weakness of different water masses and fronts is the basic reason for the variations of zooplankton biomass and abundance.The species composition of zooplankton in the study area is complex and var 相似文献
8.
9.
南沙群岛南永2井的红色沉积层和黑色沉积层标志着两次异常事件,简称为“红色事件”和“黑色事件”。这两个特殊沉积层的主要特征是磁化率为正值、锰铝(黑色沉积)和铁铝(红色沉积)含量高。关于它们的成因主要有两种观点:一种是火山喷发或地震活动,另一种是气候突变。将红色沉积层和黑色沉积层与南海其它珊瑚礁钻井资料、南海及其周缘火山活动和深海沉积中的微玻陨石进行详细对比,并综合分析几种成因的可能性大小。“红色事件”和“黑色事件”在南海其它珊瑚礁钻井中的反映不明显或无反映,表明两事件的影响范围很有限。尽管南海周缘的一些火山活动期次、全球气候变化的一些代用指标和深海沉积中的微玻陨石层在时间上与“红”、“黑”两事件有较好的对比,成岩作用也能使某些沉积层位形成铁富集或锰富集,但综合考虑各个因素可以排除周缘火山喷发、气候突变、撞击事件及成岩作用等4种成因。火山或地震活动引起的铁或锰热泉上涌可以对“红”、“黑”两事件作出较好的解释,是可能性较大的成因。 相似文献
10.
江苏省主要湖泊的降水量与湖泊的降水效应 总被引:10,自引:0,他引:10
本文分析了江苏境内主要湖泊的降水量特征,揭示了长江是江苏各湖泊不同降水量特征的一条十分明显的天然界线;估算了太湖的降水效应,并据此推估出江苏主要湖泊的降水效应不太明显;江苏各湖泊的降水量与其水位年过程趋势相似,只是后者位相滞后于前者而已。 相似文献