全文获取类型
收费全文 | 118099篇 |
免费 | 1918篇 |
国内免费 | 1039篇 |
专业分类
测绘学 | 2986篇 |
大气科学 | 8710篇 |
地球物理 | 24116篇 |
地质学 | 40920篇 |
海洋学 | 10141篇 |
天文学 | 26104篇 |
综合类 | 312篇 |
自然地理 | 7767篇 |
出版年
2021年 | 949篇 |
2020年 | 1124篇 |
2019年 | 1186篇 |
2018年 | 2534篇 |
2017年 | 2387篇 |
2016年 | 3137篇 |
2015年 | 2000篇 |
2014年 | 3106篇 |
2013年 | 6135篇 |
2012年 | 3271篇 |
2011年 | 4613篇 |
2010年 | 3941篇 |
2009年 | 5390篇 |
2008年 | 4950篇 |
2007年 | 4571篇 |
2006年 | 4483篇 |
2005年 | 3696篇 |
2004年 | 3727篇 |
2003年 | 3479篇 |
2002年 | 3264篇 |
2001年 | 2944篇 |
2000年 | 2857篇 |
1999年 | 2389篇 |
1998年 | 2447篇 |
1997年 | 2345篇 |
1996年 | 2006篇 |
1995年 | 1957篇 |
1994年 | 1764篇 |
1993年 | 1604篇 |
1992年 | 1527篇 |
1991年 | 1393篇 |
1990年 | 1596篇 |
1989年 | 1371篇 |
1988年 | 1227篇 |
1987年 | 1506篇 |
1986年 | 1311篇 |
1985年 | 1646篇 |
1984年 | 1841篇 |
1983年 | 1751篇 |
1982年 | 1628篇 |
1981年 | 1508篇 |
1980年 | 1344篇 |
1979年 | 1252篇 |
1978年 | 1314篇 |
1977年 | 1193篇 |
1976年 | 1139篇 |
1975年 | 1069篇 |
1974年 | 1070篇 |
1973年 | 1064篇 |
1972年 | 683篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
591.
592.
593.
594.
Christian Betzler Jörn Fürstenau Thomas Lüdmann Christian Hübscher Sebastian Lindhorst Andreas Paul John J. G. Reijmer André W. Droxler 《Basin Research》2013,25(2):172-196
Multichannel high‐resolution seismic and multibeam data were acquired from the Maldives‐isolated carbonate platform in the Indian Ocean for a detailed characterization of the Neogene bank architecture of this edifice. The goal of the research is to decipher the controlling factors of platform evolution, with a special emphasis on sea‐level changes and changes of the oceanic currents. The stacking pattern of Lower to Middle Miocene depositional sequences, with an evolution of a ramp geometry to a flat‐topped platform, reflects variations of accommodation, which here are proposed to be primarily governed by fluctuations of relative sea level. Easterly currents during this stage of bank growth controlled an asymmetric east‐directed progradation of the bank edge. During the late middle Miocene, this system was replaced by a twofold configuration of bank development. Bank growth continued synchronously with partial bank demise and associated sediment‐drift deposition. This turnover is attributed to the onset and/or intensification of the Indian monsoon and related upwelling and occurrence of currents, locally changing environmental conditions and impinging upon the carbonate system. Mega spill over lobes, shaped by reversing currents, formed as large‐scale prograding complexes, which have previously been interpreted as deposits formed during a forced regression. On a regional scale, a complex carbonate‐platform growth can occur, with a coexistence of bank‐margin progradation and aggradation, as well as partial drowning. It is further shown that a downward shift of clinoforms and offlapping geometries in carbonate platforms are not necessarily indicative for a sea‐level driven forced regression. Findings are expected to be applicable to other examples of Cenozoic platforms in the Indo‐Pacific region. 相似文献
595.
PAULJ.GEMPERLINE 《地理学报(英文版)》1989,(3)
One of the major application areas of factor analysis, multivariate calibration and quantitation, is coveredin this review. The algorithms, methodologies and applications covered include principal componentregression, target transformation factor analysis, singular value decomposition and rank annihilationfactor analysis. Many important areas of research having relevance to multivariate calibration andquantitation problems are also covered in this review, including background correction, measurementerror, rank determination, cross-validation, figures of merit, detection of invalid samples, experimentaldesign, sample selection, statistical inference and wavelength selection. 相似文献
596.
A possible suture between an old craton in West Africa and the Arabian—Nubian shield is marked by a persistent zone of Phanerozoic weakness. This zone extends between the Nile and Niger deltas and passes through the Qattara embayment, along the Bahariya fault, through the Kufra basin, between the Tibesti and Jabal al Uwaynat massifs, through the Bahr el Ghazal and Lake Chad areas, and along the Benoue trough. 相似文献
597.
J. R. Smith 《The Photogrammetric Record》1998,16(91):157-157
598.
599.
G. M. Appleby 《Journal of Geodesy》1998,72(6):333-342
In this paper we describe the results of an analysis of a 2.5-year set of satellite laser range observations of the two Etalon
geodetic satellites. We fit continuous orbits to the range observations, and map the range residuals into series of equivalent
orbital element residuals, considering in detail the orbital longitude, eccentricity and nodal residuals. We use the longitude
residuals to study thermal effects acting on the satellites and compare the results with those published for the Lageos satellites.
We discuss the differences between the two series of eccentricity residuals, and again compare the results with those from
Lageos. Finally we use the nodal residuals to investigate the potential for determination of UT1 of the reference frame defined
by the orbits of the Etalon satellites.
Received: 30 January 1997 / Accepted: 11 December 1997 相似文献
600.
In this paper, a number of robust biased estimators (e.g. ordinary robust ridge estimator, robust principal components estimator,
robust combined principal components estimator, robust single-parametric principal components estimator, robust root-root
estimator) are established by means of a unified expression of biased estimators and based on the principle of equivalent
weight. The most attractive advantage of these new estimators is that they can not only overcome the ill-conditioning of the
normal equation but also have the ability to resist outliers. A numerical example is used to illustrate that these new estimators
are much better than the least-squares estimator and various biased estimators even when both ill-conditioning and outliers
exist.
Received: 14 November 1995/Accepted: 11 February 1998 相似文献