全文获取类型
收费全文 | 26350篇 |
免费 | 4643篇 |
国内免费 | 7114篇 |
专业分类
测绘学 | 4578篇 |
大气科学 | 5081篇 |
地球物理 | 6701篇 |
地质学 | 11762篇 |
海洋学 | 3956篇 |
天文学 | 299篇 |
综合类 | 2014篇 |
自然地理 | 3716篇 |
出版年
2024年 | 175篇 |
2023年 | 463篇 |
2022年 | 969篇 |
2021年 | 1138篇 |
2020年 | 1334篇 |
2019年 | 1454篇 |
2018年 | 1218篇 |
2017年 | 1404篇 |
2016年 | 1541篇 |
2015年 | 1632篇 |
2014年 | 1725篇 |
2013年 | 1954篇 |
2012年 | 1782篇 |
2011年 | 1796篇 |
2010年 | 1483篇 |
2009年 | 1674篇 |
2008年 | 1695篇 |
2007年 | 1737篇 |
2006年 | 1667篇 |
2005年 | 1460篇 |
2004年 | 1295篇 |
2003年 | 1116篇 |
2002年 | 1030篇 |
2001年 | 884篇 |
2000年 | 822篇 |
1999年 | 736篇 |
1998年 | 705篇 |
1997年 | 579篇 |
1996年 | 525篇 |
1995年 | 467篇 |
1994年 | 401篇 |
1993年 | 338篇 |
1992年 | 211篇 |
1991年 | 184篇 |
1990年 | 119篇 |
1989年 | 93篇 |
1988年 | 91篇 |
1987年 | 60篇 |
1986年 | 29篇 |
1985年 | 33篇 |
1984年 | 20篇 |
1983年 | 2篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1954年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
于圣睿 《中国海洋大学学报(自然科学版)》1990,(4)
采用金属络合物通式模型,在IBM-PC计算机上计算了不同pH(7.5~9.5)、碱度(2.3~2.5mmol dm~(-3))和加入不同浓度的铜离子(1.0×10~(-4)~1.0mg dm~(-3))条件下,海水培养液中铜的主要化学存在形式分配的百分数。还给出了计算机程序框图和主要化学存在形式含量的百分数随pH、碱度和铜浓度变化图。 相似文献
132.
本文以我国北黄海的烟威渔场为研究对象,采用优选因子场预报模式,对盐度的时空变化进行预报试验。文中对所采用的统计预报方法,作了简要介绍。对影响本海区盐度变化的显著因子及预报结果作了初步分析。预报试验表明:预报的总体平均绝对误差为0.27‰,预报相对误差在18%左右,预报误差小于0.5‰的站数占总站数的85%,预报趋势与实测资料基本一致。 相似文献
133.
134.
青岛市大气污染时间序列分析预报方法研究 总被引:5,自引:0,他引:5
根据青岛市大气污染监测资料 ,采用时间序列分析方法 ,建立多种预报模型 ,有原序列周期外延法、均生函数周期外延法、均生函数逐步回归法以及自回归预报法等 ,最后提出一种综合预报模型。连续预报试验表明 ,综合预报模型优于任何个别预报模型 ,有较好的预报能力。利用马尔可夫概型对污染状态 (轻、中、重 )进行了分级预报试验 ,也获得良好的效果。 相似文献
135.
三传感器波浪水槽二次反射主动吸收方法是加拿大科学院水力中心最近开发的一种水槽反射波控制技术。该法在造波板前 1~ 2倍波长处布置 3个传感器 ,通过入反射波分离方法得到准确的入反射波参数 ,以此调整造波信号 ,有效地吸收由建筑物反射回到造波板的二次反射波。文中在分析波浪水槽二次反射吸收方法研究现状的基础上 ,介绍了加拿大水力中心对现有方法的改进及其效果 相似文献
136.
长江口深水航道数学模型信息系统研究 总被引:3,自引:0,他引:3
利用GIS二次开发软件ArcView,完成数学模拟所需的计算网格生成及线边界法中地形数据提取的优化。集成ArcView、Visual Basic及长江口潮流数学模型,实现了数值模拟计算成果的三维可视化及实时互动的动态演示。所开发的长江口数学模型信息系统能根据整治工程需要,提交各类工程数据库。 相似文献
137.
138.
The effect of the cone spacing of a conieal structure on the ice force is studied by model experiments. The ice force reduction coefficient presented in this paper expresses the relationship between the ice force and the arrangement of cones. The experiments prove that the mode of the ice failure before the boundary of upward-downward bending cone (UDBC) is crushing. A conclusion can also be drawn from the experiments that the ice force on the boundary of UDBC is by far less than that on a vertical pile with the same diameter. Moreover, the ice force frequencies on upright and inve-rted cones are obtained under the field condition of the platform JZ20-2, respectively. The results show that the alterna-tion of the ice force on UDBC can hardly induce resonance of platform JZ20-2. 相似文献
139.
We have examined wind-induced circulation in the Sea of Okhotsk using a barotropic model that contains realistic topography
with a resolution of 9.25 km. The monthly wind stress field calculated from daily European Centre for Medium-Range Weather
Forecasting (ECMWF) Re-Analysis data is used as the forcing, and the integration is carried out for 20 days until the circulation
attains an almost steady state. In the case of November (a representative for the winter season from October to March), southward
currents of velocity 0.1–0.3 m s−1 occur along the bottom contours off the east of Sakhalin Island. The currents are mostly confined to the shelf (shallower
than 200 m) and extend as far south as the Hokkaido coast. In the July case (a representative for the summer season from April
to September), significant currents do not occur, even in the shallow shelves. The simulated southward current over the east
Sakhalin shelf appears to correspond to the near-shore branch of the East Sakhalin Current (ESC), which was observed with
the surface drifters. These seasonal variations simulated in our experiments are consistent with the observations of the ESC.
Dynamically, the simulated ESC is interpreted as the arrested topographic wave (ATW), which is the coastally trapped flow
driven by steady alongshore wind stress. The volume transport of the simulated ESC over the shelf reaches about 1.0 Sv (1
Sv = 106 m3s−1) in the winter season, which is determined by the integrated onshore Ekman transport in the direction from which shelf waves
propagate.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
140.
Using meteorological data of field observation in 1990 - 2000, especially polar orbit high-resolution NOAA satellite cloud maps received from the Antarctic expedition vessel since 1997, the formation and development of the Prydz Bay cyclone are studied in this paper. Some new viewpoints are suggested such as: when surround-polar cyclone enters the Prydz Bay, it can also intensify and develop in summer; cyclone can also develop in the easterlies in this bay. These view points revise old uncom-plete view point that the Prydz Bay is a burial ground of cyclone, and also further consummate formation-development theory of surround-cyclone in the Antarctic westerlies and cyclone in the Antarctic easterlies. In this paper, the mechanism of ice-air-sea interaction in the Prydz Bay is studied, and the physical process of cyclone formation-development is explained. By use of wholly dynamic transportation method, an energy exchange case of a cyclone, which explosively developed after entering the Prydz Bay, is calcu 相似文献