全文获取类型
收费全文 | 94162篇 |
免费 | 26197篇 |
国内免费 | 50624篇 |
专业分类
测绘学 | 6735篇 |
大气科学 | 29892篇 |
地球物理 | 25256篇 |
地质学 | 63480篇 |
海洋学 | 21576篇 |
天文学 | 4936篇 |
综合类 | 9965篇 |
自然地理 | 9143篇 |
出版年
2024年 | 445篇 |
2023年 | 1351篇 |
2022年 | 3114篇 |
2021年 | 3945篇 |
2020年 | 4493篇 |
2019年 | 7798篇 |
2018年 | 8578篇 |
2017年 | 8053篇 |
2016年 | 8462篇 |
2015年 | 7131篇 |
2014年 | 7497篇 |
2013年 | 8039篇 |
2012年 | 7581篇 |
2011年 | 7555篇 |
2010年 | 7429篇 |
2009年 | 6761篇 |
2008年 | 5790篇 |
2007年 | 5777篇 |
2006年 | 5044篇 |
2005年 | 4500篇 |
2004年 | 4236篇 |
2003年 | 3969篇 |
2002年 | 3778篇 |
2001年 | 3594篇 |
2000年 | 3388篇 |
1999年 | 4068篇 |
1998年 | 3565篇 |
1997年 | 3599篇 |
1996年 | 3003篇 |
1995年 | 2843篇 |
1994年 | 2534篇 |
1993年 | 2297篇 |
1992年 | 1900篇 |
1991年 | 1467篇 |
1990年 | 1214篇 |
1989年 | 1097篇 |
1988年 | 945篇 |
1987年 | 683篇 |
1986年 | 580篇 |
1985年 | 430篇 |
1984年 | 440篇 |
1983年 | 295篇 |
1982年 | 316篇 |
1981年 | 230篇 |
1980年 | 189篇 |
1979年 | 167篇 |
1978年 | 85篇 |
1977年 | 75篇 |
1971年 | 63篇 |
1958年 | 58篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
A Preliminary Study of Shear Wave in Seafloor Surface Sediments 总被引:1,自引:0,他引:1
This article preliminarily reports and analyses the transmission characteristics and behaviors of shear wave in the offshore seafloor surface sediments in China, discusses the relationships between the physical and mechanical features of the shear wave and the compression wave, and compares the testing results with that of Hamilton and Chen et al. The result shows that the shear wave can be tested if the seafloor surface sediment has tangent modulus. The shear wave velocity ranges from 50-600 m/s and the measuring frequency from 50-200 kHz. The sound velocity rate of shear wave and compression wave can be used to appraise the stress-strain feature of seafloor surface sediments. This study provides a basis for further describing and appraising the seafloor sedimentary acoustic-mechanical feature and building a geological-acoustic model on China's offshore sea area. 相似文献
92.
We study the problem of determination of the sound field of a point harmonic source in the coastal zone and the influence of a cylindrical body floating above the source on the sound field formed in the marine medium. A numerical-analytic method is proposed for the determination of the velocity potential. According to this method, the unknown coefficients in the general solution of the problem are determined from the corresponding infinite system of linear algebraic equations by the method of reduction. We present results of numerical calculations for a special case of a waveguide whose parameters are typical of the coastal part of the sea and perform the comparative analysis of the data obtained as a result of variation of the indicated parameters. 相似文献
93.
In the food clods of the mass species of macrobenthos of the Gryaznaya Inlet, nonstructured matter plays a great role. We identify this matter as derivates from plant tissues, which are the products of their external metabolism and degradation, with associated microorganisms. This way, the near-shore community considered is supported by a detrital trophic web. This feature distinguishes it from the similar community of the near-Atlantic waters that is based on a pasture web, at least as far as the bivalve mass species are concerned. The groups of the near-shore species of Gryaznaya Inlet separated by a cluster analysis are identified as consortia, combined by the biogeochemical conditions (edifice factor), which can hardly be analyzed at present. 相似文献
94.
The basic properties of the dynamic model of a turbulent jet formed by a deep-water sewage discharge into the stratified environment of coastal regions are considered. The model developed was used to estimate the parameters of a floating-up jet of deep wastewater discharge from Sand Island into the basin of Mamala Bay (Hawaii) depending on the season and discharge operation mode. The estimates of the float-up depths of the jet and the initial dilution of the jet were estimated on the basis of model calculations using experimental data on the vertical profiles of the water temperature and salinity under the actual conditions of stratification in the study region. It is shown that the further propagation of the wastewater jet depends on tidal events and internal waves generated by tides. The appearance of turbulent jets at the sea surface was recorded. The model estimates of the parameters of the wastewater discharge were compared with the results of experimental measurements. Good agreement was found, which indicates that the physical mechanisms of the propagation of turbulent jets in a stratified medium are adequately described by the model. 相似文献
95.
最近十几年来,海水物理化学中关于海水的化学热力学研究已较广泛地开展,并已有一些重要的研究结果报导。但是,关于海水中化学动力学的研究,至今却基本上仍属空白。然而这正是海洋中许多化学过程(特别像海水化学资源开发、海洋污染和防治等实践性比较强的领域中)要解决的关键问题。本文是我们从事这一方面研究工作的第一篇报导,讨论的内容是海洋中最重要的过程之一——无机离子交换过程。 相似文献
96.
Xie Simei Hao Chunjiang Zou Bin Jing Qiyi Liao Xiaohong Sheng Xiaowen Zhang Canrong 《海洋学报(英文版)》2000,19(1):35-46
INTRODUCTIONTheSMSRPSisstalledontheshipnavigatingovertheseaandreceivessatellitecloudmapsatanytimetoprovidereliablereal-timedataofmeteorologyandocean.Itisanimportantequipmentforsafeguardofshipnavigation.Chinahasthousandsofoceanicships.Butalmostallships,withonlyveryfewexception,arenotstalledbySMSRPS.Thecausesareasfollows:1.Thetechniqueisverycomplicated.2.Thedevelopmentcostisveryhigh.3.Ifweintroduceforeignequipment,thecostistooexpensive.4.Foreignequipmentanditssoftwarearecompletelyclo… 相似文献
97.
本文根据1982年4月21日~5月12日,7月23日~8月5日,10月12~30日在34°30′N以北.124°E以西黄海水域污染现状综合调查中获得的样品和资料,分析了本海区水母类的种类组成,数量分布以及季节变化。调查海区共鉴定有34种水母,其中优势种有盘形美螅水母Clytiadiscoida,四枝管水母Proboscidactylaflavicirrata,五角水母Muggiaeaattantica。秋季(10月)为水母类总个体数的高峰期(8.67个/m3)。水母类的分布与水温、盐度密切相关,海流或水团也起重要作用.水母类分布的变更可以反映出沿岸水和外海水相互推移和消长状况。 相似文献
98.
99.
青岛浮山野生花卉种质资源 总被引:2,自引:0,他引:2
本文简要叙述了青岛浮山野生花卉的种类、生长环境、园林用途及开花结果日期,为把这些野生花生花卉引进城市园林提供科学依据。 相似文献
100.
王梅林 《中国海洋大学学报(自然科学版)》1987,(2)
每几个不同种的雌性克隆对高温(22℃、24℃、26℃)的适应力有所差异。大西洋沿岸的Laminariahyperhoren和L.sacchrina雌性克隆较太平洋沿岸的L.japonica、L.angustata和L.ochotensis雌性克隆明显地不耐高温,遗传性的不同是造成这种差异的主要原因。这种遗传性差异是海带长期自然选择的结果。同一物种L.japonica和L.japonicaCⅡ两种雌性克隆在24℃条件下,在第24天其死亡率分别是40.2%和25.2%,X~2=12.25,P<0.001,差异是高度显著的,说明这种不同是遗传性不同所致,而且属于物种内部的差异。 相似文献