全文获取类型
收费全文 | 25177篇 |
免费 | 4539篇 |
国内免费 | 5479篇 |
专业分类
测绘学 | 2064篇 |
大气科学 | 4814篇 |
地球物理 | 6639篇 |
地质学 | 12266篇 |
海洋学 | 3270篇 |
天文学 | 1011篇 |
综合类 | 2211篇 |
自然地理 | 2920篇 |
出版年
2024年 | 133篇 |
2023年 | 408篇 |
2022年 | 1121篇 |
2021年 | 1328篇 |
2020年 | 1083篇 |
2019年 | 1261篇 |
2018年 | 1694篇 |
2017年 | 1545篇 |
2016年 | 1471篇 |
2015年 | 1276篇 |
2014年 | 1427篇 |
2013年 | 1490篇 |
2012年 | 1979篇 |
2011年 | 1815篇 |
2010年 | 1495篇 |
2009年 | 1362篇 |
2008年 | 1241篇 |
2007年 | 1126篇 |
2006年 | 1007篇 |
2005年 | 1611篇 |
2004年 | 1419篇 |
2003年 | 1145篇 |
2002年 | 667篇 |
2001年 | 631篇 |
2000年 | 603篇 |
1999年 | 742篇 |
1998年 | 578篇 |
1997年 | 539篇 |
1996年 | 513篇 |
1995年 | 423篇 |
1994年 | 399篇 |
1993年 | 333篇 |
1992年 | 306篇 |
1991年 | 205篇 |
1990年 | 171篇 |
1989年 | 137篇 |
1988年 | 106篇 |
1987年 | 85篇 |
1986年 | 56篇 |
1985年 | 45篇 |
1984年 | 33篇 |
1983年 | 30篇 |
1982年 | 27篇 |
1981年 | 13篇 |
1980年 | 13篇 |
1979年 | 16篇 |
1978年 | 10篇 |
1975年 | 8篇 |
1958年 | 11篇 |
1954年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
191.
二次特征值问题 (QEP)的主要的求解方法之一是转化为广义特征值问题 (GEP) ,然后用求解广义特征值的方法 (比如 QZ方法 )求解。本文研究由此获得的计算解的范数意义下的最佳向后扰动分析 ,所得结果是 Tisseur最近所得结果的加强。 相似文献
192.
Algorithm for HF radar vector current measurements 总被引:1,自引:0,他引:1
A new algorithm is proposed, called the stream function method (SFM) for producing vector current maps from radial data measured
by dual-site high frequency surface wave radar (HFSWR). In SFM, a scalar stream function is constructed under some oceanographic
assumptions. The function describes the two-dimensional (2-D) ocean surface water motion and is used to obtain the distribution
of vector currents. The performance of SFM is evaluated using simulated radial data, which demonstrates that SFM has advantages
over typical vectorial combination methods (VCM) both in error acceptance and robustness, and excels another method based
on least-squares fitting (LSF) in recovering the complicated current models. Furthermore, SFM is capable of providing the
total currents based on radials from single-site radar. We also test the assumptions of horizontal non-divergence in the simulation.
The new algorithm is applied to the field experiment data of Wuhan University’s ocean state measuring and analyzing radar
(OSMAR), collected in the coastal East China Sea during April 11–17, 2004. Quantitative comparisons are given between radar
results by three current algorithms and in-situ current meter measurements. Preliminary analysis of the vertical current shear is given based on the current meter measurements. 相似文献
193.
Takushi?NikiEmail author Taiki?Fujinaga Mariyo?F.?Watanabe Junji?Kinoshita 《Journal of Oceanography》2004,60(5):913-917
Solid-phase microextraction (SPME) is a simple, sensitive and less destructive method for the determination of dimethylsulfide
(DMS) in seawater. Combined with detection by gas chromatography-mass spectrometry (GC-MS), the method had sufficient sensitivity
(minimum detectable concentration of DMS was 0.05 nM), and practical levels of reproducibility (relative standard deviation
≤7%) and linearity (r
2 > 0.995) over a wide concentration range (0.5 to 910 nM). The protocol developed was applied to a Sagami Bay water sample
to determine concentrations of DMS and DMSP, and in situ DMSP-lyase activity. 相似文献
194.
Eddy Shedding from the Kuroshio Bend at Luzon Strait 总被引:16,自引:1,他引:16
TOPEX/POSEDIENT-ERS satellite altimeter data along with the mean state from the Parallel Ocean Climate Model result have been used to investigate the variation of Kuroshio intrusion and eddy shedding at Luzon Strait during 1992–2001. The Kuroshio penetrates into the South China Sea and forms a bend. The Kuroshio bend varies with time, periodically shedding anticyclonic eddies. Criteria of eddy shedding are identified: 1) When the shedding event occurs, there are usually two centers of high Sea Surface Height (SSH) together with negative geostrophic vorticity in the Kuroshio Bend (KB) area. 2) Between the two centers of high SSH there usually exists positive geostrophic vorticity. These criteria have been used to determine the eddy shedding times and locations. The most frequent eddy shedding intervals are 70, 80 and 90 days. In both the winter and summer monsoon period, the most frequent locations are 119.5°E and 120°E, which means that the seasonal variation of eddy shedding location is unclear. 相似文献
195.
湄洲湾泥沙活动及海底冲淤变化 总被引:1,自引:0,他引:1
湄洲湾沙源少,海水含沙量低,平均值10~20g/m~3。冬季受东北季风及浙闽沿岸流影响,湾口含沙量高,达到34g/m~3;夏季受径流影响,湾内含沙量相对偏高,达到16g/m~3。泥沙的运移趋势:主航道基本朝外,两侧朝里。受强潮流作用,深槽及水下潮流冲沟受到冲刷,斜坡及潮坪略有淤积。 相似文献
196.
197.
198.
渤海南部表层沉积的相特征 总被引:1,自引:0,他引:1
通过海上调查及实验室分析,查明渤海南部表层沉积物在结构类型、矿物组合、生物组分及沉积构造等相特征方面具有明显的分区性。渤海南部存在五种沉积相:黄河水下三角洲相、陆架盆地相、海湾相、潮流浅滩相及古滨岸相。黄河水下三角洲相从河口延至水深15—20米处,沉积速率很高,沉积物富含碎屑云母及CaCo_3。陆架盆地相的沉积为粉砂质粘土,具有生物扰动构造。 相似文献
199.
仲裁亦称公断,是指争议的当事人在自愿的基础上,将争议提交非司法机构的第三者审理,并做出对争议各方有约束力裁决的一种解决争议的法律制度。以私法方面带有国际因素或涉外因素的争议为对象进行的仲裁,通常称为国际商事仲裁。其在狭义上不同于解决国家之间某一公法上的争端的国际仲裁、不同于为解决国家与企业或私人实体间争议所进行的跨国仲裁、也不同于解决一国范围内自然人、法人和其他组织之间争议包括行政仲裁在内的国内仲裁:广义上国际商事仲裁还包括跨国仲裁。国际商事仲裁主要包括国际贸易和国际海事仲裁。本文仅在狭义上讨论。按照我国现行法律规定,本文称涉外海事仲裁。 相似文献
200.
In this paper we analyze seismic regime and earthquake depth distribution and correlation of seismicity and mud volcanism in the Azerbaijan and the Caspian Sea region. For the present region we have calculated accurate source locations, seismic activity, earthquake repetition and released earthquake energy parameters. It is shown that the active tectonic processes in the region are concentrated within the thick sedimentary cover that we consider as a general source of contemporary stress and a main structural element responsible for the origin of regional earthquakes. The correlation of seismicity and mud volcanism is of paragenetic character. 相似文献