全文获取类型
收费全文 | 1048篇 |
免费 | 223篇 |
国内免费 | 369篇 |
专业分类
测绘学 | 233篇 |
大气科学 | 69篇 |
地球物理 | 222篇 |
地质学 | 572篇 |
海洋学 | 303篇 |
天文学 | 10篇 |
综合类 | 100篇 |
自然地理 | 131篇 |
出版年
2024年 | 9篇 |
2023年 | 29篇 |
2022年 | 80篇 |
2021年 | 96篇 |
2020年 | 62篇 |
2019年 | 58篇 |
2018年 | 73篇 |
2017年 | 49篇 |
2016年 | 57篇 |
2015年 | 78篇 |
2014年 | 77篇 |
2013年 | 71篇 |
2012年 | 88篇 |
2011年 | 79篇 |
2010年 | 92篇 |
2009年 | 84篇 |
2008年 | 80篇 |
2007年 | 86篇 |
2006年 | 99篇 |
2005年 | 55篇 |
2004年 | 73篇 |
2003年 | 28篇 |
2002年 | 30篇 |
2001年 | 36篇 |
2000年 | 26篇 |
1999年 | 10篇 |
1998年 | 5篇 |
1997年 | 7篇 |
1996年 | 1篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1981年 | 2篇 |
1979年 | 4篇 |
1964年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有1640条查询结果,搜索用时 15 毫秒
1.
2.
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
3.
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
4.
5.
Some studies have been made on the variation of primary productivity in the Central South ChinaSea. This paper studies comprehensively the characteristics of chlorophyll a distributions in time andspace and the primary productivity, as well their relations to the environmental factors.Materals and methods During the comprehensive investigation in the Central South China Sea from September 1983 toDecember 1984, the distributions of chlorophyll a and primary productivity were studied. Figure 1shows the sampling stations and their range of investigation. 相似文献
6.
7.
8.
Diatoms are major primary producers of microbial biomass in the Antarctica. They are found in the water and sea ice. The distribution, abundance of the ice diatoms and their relation to the environmental factors inside and outside the ice have been studied for its special role in the Antarctic Ocean ecology. In this paper we describe the abundance, distribution and composition of diatom assemblages in 相似文献
9.
10.
Comparison of Drags on Fish Cages of Different Shapes 总被引:1,自引:0,他引:1
1 .Introduction Commercial fishfarming in net cages is becoming widespread around the world as an importantsource of food.In PRChina ,mostfishfarmingtakes placeincalmcoastal areas .Fishcages work wellat these sites becausethe environmental forces are usua… 相似文献