全文获取类型
收费全文 | 25891篇 |
免费 | 4924篇 |
国内免费 | 6249篇 |
专业分类
测绘学 | 4294篇 |
大气科学 | 6735篇 |
地球物理 | 5740篇 |
地质学 | 11133篇 |
海洋学 | 2743篇 |
天文学 | 955篇 |
综合类 | 2209篇 |
自然地理 | 3255篇 |
出版年
2024年 | 105篇 |
2023年 | 280篇 |
2022年 | 667篇 |
2021年 | 863篇 |
2020年 | 932篇 |
2019年 | 1149篇 |
2018年 | 825篇 |
2017年 | 1016篇 |
2016年 | 994篇 |
2015年 | 1232篇 |
2014年 | 1519篇 |
2013年 | 1610篇 |
2012年 | 1720篇 |
2011年 | 1881篇 |
2010年 | 1463篇 |
2009年 | 1697篇 |
2008年 | 1639篇 |
2007年 | 2037篇 |
2006年 | 1877篇 |
2005年 | 1675篇 |
2004年 | 1531篇 |
2003年 | 1353篇 |
2002年 | 1226篇 |
2001年 | 1020篇 |
2000年 | 1007篇 |
1999年 | 878篇 |
1998年 | 820篇 |
1997年 | 734篇 |
1996年 | 650篇 |
1995年 | 536篇 |
1994年 | 511篇 |
1993年 | 394篇 |
1992年 | 304篇 |
1991年 | 232篇 |
1990年 | 180篇 |
1989年 | 161篇 |
1988年 | 109篇 |
1987年 | 85篇 |
1986年 | 41篇 |
1985年 | 31篇 |
1984年 | 15篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 11篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1954年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 531 毫秒
101.
提出一种确定连续系统参数的时域方法。该方法利用方波输入和系统稳定性,离析出输出采样信号与结构参数的内在联系,推导出确定连续系统结构参数的算法.指出该算法与辨识方法相结合,可实现对含随机干扰的连续系统结构参数的估计. 相似文献
102.
103.
公用微机硬盘信息保护的一种有效方法 总被引:1,自引:0,他引:1
张玉彪 《中国海洋大学学报(自然科学版)》1994,(Z2)
介绍一种保护公用微机硬盘信息的有效方法.不仅可以预防各种计算机病毒,更重要的是可以防止人为操作对硬盘信息的破坏。适用于学校等开放性微机实验室的信息安全与保护. 相似文献
104.
Ocean current forecasting is still in explorative stage of study. In the study, we face some problems that have not been met before. The solving of these problems has become fundamental premise for realizing the ocean current forecasting. In the present paper are discussed in depth the physical essence for such basic problems as the predictability of ocean current, the predictable currents, the dynamical basis for studying respectively the tidal current and circulation, the necessity of boundary model, the models on regions with different scales and their link. The foundations and plans to solve the problems are demonstrated. Finally a set of operational numerical forecasting system for ocean current is proposed. 相似文献
105.
Cao Guoao Shen Yilei
Dr.Professor Tongji University Shanghai
Shanghai College of Architectural Municipal Engineering Shanghai 《中国海洋工程》1991,(1)
In this paper, the responses of the interaction system of R.C. gravity single-leg platform to seismic excitation are mainly analysed. A set of nonlinear equations for the interaction system are established by using the wave, one is the soil-structure interaction and the other is the fluid-structure interaction. The seismic response of the interaction system is analysed for the influence of the asymmetric structure, fluid action, etc. with the input of seismic SH waves in any direction. The numerical results are given for a simple example. 相似文献
106.
随着Linux技术逐步走向成熟,嵌入式Linux技术在海洋自动观测系统中的应用将全面提高海洋观测系统整体性能,降低系统开发成本,进一步推进我国海洋自动观测系统产权自主化的建设。文章就如何研制适用于海洋自动观测系统的嵌入式Linux系统进行了论述。 相似文献
107.
本文运用福建省沿海气象要素的异常变化,作台湾省的中、短期地震预报,取得了成功的效果。采用长乐历年各月14时最低气压的距平值,作台湾省未来4~7个月内出现强震的预报依据,并采用热异常进行短临跟踪。当秋冬季节连续4d 长乐、福州、台北的气温均比广州累计高出10℃时,预报未来1~5d 台湾省出现7级强震。又根据近百年来台湾发生的强震,统计其活动季节,得到近20年来7级地震发生的时间,绝大部分在9~12月。 相似文献
108.
Rifting to Spreading Process along the Northern Continental Margin of the South China Sea 总被引:7,自引:0,他引:7
Understanding the development from syn-rift to spreading in the South China Sea (SCS) is important in elucidating the western Pacific's tectonic evolution because the SCS is a major tectonic constituent of the many marginal seas in the region. This paper describes research examining the transition from rifting to spreading along the northern margin of the SCS, made possible by the amalgamation of newly acquired and existing geophysical data. The northernmost SCS was surveyed as part of a joint Japan-China cooperative project (JCCP) in two phases in 1993 and 1994. The purpose of the investigation was to reveal seismic and magnetic characteristics of the transitional zone between continental crust and the abyssal basin. Compilation of marine gravity and geomagnetic data of the South China Sea clarify structural characteristics of its rifted continental and convergent margins, both past and present. Total and three component magnetic data clearly indicate the magnetic lineations of the oceanic basin and the magnetic characteristics of its varied margins. The analyses of magnetic, gravity and seismic data and other geophysical and geological information from the SCS led up to the following results: (1) N-S direction seafloor spreading started from early Eocene. There were at least four separate evolutional stages. Directions and rates of the spreading are fluctuating and unstable and spreading continued from 32 to 17 Ma. (2) The apparent difference in the present tectonism of the eastern and western parts of Continent Ocean Boundary (COB) implies that in the east of the continental breakup is governed by a strike slip faulting. (3) The seismic high velocity layer in the lower crust seems to be underplated beneath the stretched continental crust. (4) Magnetic anomaly of the continental margin area seems to be rooted in the uppermost sediment and upper part of lower crust based on the tertiary volcanism. (5) Magnetic quiet zone (MQZ) anomaly in the continental margin area coincides with COB. (6) The non-magnetic or very weakly magnetized layer is probably responsible for MQZ. One of the causes of demagnetization of the layer is due to hydrothermal alteration while high temperature mantle materials being underplated. Another explanation is that horizontal sequences of basalt each with flip-flop magnetization polarity cancel out to the resultant magnetic field on the surface. We are currently developing a synthetic database system containing datasets of seismicity, potential field data, crustal and thermal structures, and other geophysical data to facilitate the study of past, contemporary and future changes in the deep sea environment around Japan; i.e. trench, trough, subduction zones, marginal basins and island arcs. Several special characteristics are an object-oriented approach to the collection and multi-faceted studies of global data from a variety of sources. 相似文献
109.
110.
用三峡及邻区(东经108°~113°,北纬29°~33°)地质资料,地震资料,现 场地应力测量资料论证三峡及邻区晚第三纪以来构造应力场稳定性及其分区特 征。 相似文献