全文获取类型
收费全文 | 6851篇 |
免费 | 1284篇 |
国内免费 | 1648篇 |
专业分类
测绘学 | 317篇 |
大气科学 | 1486篇 |
地球物理 | 1806篇 |
地质学 | 3248篇 |
海洋学 | 1036篇 |
天文学 | 219篇 |
综合类 | 860篇 |
自然地理 | 811篇 |
出版年
2024年 | 30篇 |
2023年 | 119篇 |
2022年 | 328篇 |
2021年 | 366篇 |
2020年 | 342篇 |
2019年 | 314篇 |
2018年 | 383篇 |
2017年 | 363篇 |
2016年 | 424篇 |
2015年 | 315篇 |
2014年 | 405篇 |
2013年 | 373篇 |
2012年 | 352篇 |
2011年 | 383篇 |
2010年 | 425篇 |
2009年 | 371篇 |
2008年 | 305篇 |
2007年 | 314篇 |
2006年 | 272篇 |
2005年 | 205篇 |
2004年 | 190篇 |
2003年 | 211篇 |
2002年 | 200篇 |
2001年 | 183篇 |
2000年 | 205篇 |
1999年 | 312篇 |
1998年 | 292篇 |
1997年 | 277篇 |
1996年 | 231篇 |
1995年 | 244篇 |
1994年 | 215篇 |
1993年 | 171篇 |
1992年 | 154篇 |
1991年 | 94篇 |
1990年 | 91篇 |
1989年 | 73篇 |
1988年 | 51篇 |
1987年 | 38篇 |
1986年 | 22篇 |
1985年 | 25篇 |
1984年 | 25篇 |
1983年 | 15篇 |
1982年 | 18篇 |
1981年 | 17篇 |
1980年 | 12篇 |
1979年 | 12篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1975年 | 2篇 |
1958年 | 4篇 |
排序方式: 共有9783条查询结果,搜索用时 15 毫秒
211.
中国近海多毛纲龙介虫科(石灰虫科)Serpulidae的分类区系,除吴宝铃和陈木(1985,1991)、陈木和吴宝铃(1978,1980)发表过6个新种以及杨德渐和孙瑞平(1988)作过一些常见种报道外,迄今尚未见系统研究报道。本文根据中国科学院海洋研究所历年调查、全国海洋综合调查和作者近年来调查补采的标本进行系统整理。共鉴定龙介虫科盘管虫属28种,其中11种为我国首次记录、1个新种。模式标本保存在中国科学院海洋研究所。 相似文献
212.
213.
214.
215.
A general set of 3-D dynamic field equations for a cable segment is derived based on the classical Euler-Kirchhoff theory of an elastica. The model includes flexural stiffness to remove the potential singularity when cable tension vanishes and can be reduced to the equations for a perfectly flexible cable. A hybrid model and a solution scheme by direct integration are then proposed to solve the oceanic cable/body system with a localized low-tension region. Numerical examples demonstrate the capability and validity of the formulation and the numerical algorithm. 相似文献
216.
217.
莱州湾东部滨海水域砂金分布特征 总被引:1,自引:0,他引:1
通过对莱州湾东部滨海水域地球物理和地质钻综合调查,业已查明该海区地质的构造和古地理环境特征,并发现区内砂金分布较普遍,本文从砂金分布的地貌单元,沉积物类型,砂金成因类型,物质来源,古气候,构造作用,砂金成因等诸方面,研究了该海域内砂金特征。 相似文献
218.
This paper is concerned with the formation control problem of multiple underactuated surface vessels moving in a leader-follower formation.The formation is achieved by the follower to track a virtual target defined relative to the leader.A robust adaptive target tracking law is proposed by using neural network and backstepping techniques.The advantage of the proposed control scheme is that the uncertain nonlinear dynamics caused by Coriolis/centripetal forces,nonlinear damping,unmodeled hydrodynamics and disturbances from the environment can be compensated by on line learning.Based on Lyapunov analysis,the proposed controller guarantees the tracking errors converge to a small neighborhood of the origin.Simulation results demonstrate the effectiveness of the control strategy. 相似文献
219.
A three-dimensional coupled physical and water quality model was developed and applied to the Jiaozhou Bay to study water quality involving nutrients, biochemical oxygen demand, dissolved oxygen, and phytoplankton that are closely related to eutrophication process. The physical model is a modified ECOM-si version with inclusion of flooding/draining processes over the intertidal zone. The water quality model is based on WASP5 which quantifies processes governing internal nutrients cycling, dissolved oxygen balance and phytoplankton growth. The model was used to simulate the spatial distribution and the temporal variation of water quality in the Jiaozhou Bay for the period of May 2005 to May 2006. In addition, the effect of reduction of riverine nutrients load was simulated and evaluated. The simulated results show that under the influence of nutrients discharged from river, the concentrations of nutrients and phytoplankton were higher in the northwest and northeast of the bay, and decreased from the inner bay to the outer. Affected by strong tidal mixing, the concentrations of all state variables were vertically homogeneous except in the deeper regions where a small gradient was found. Obvious seasonal variation of phytoplankton biomass was found, which exhibited two peaks in March and July, respectively. The variation of riverine waste loads had remarkable impact on nutrients concentration in coastal areas, but slightly altered the distribution in the center of the bay. 相似文献
220.