全文获取类型
收费全文 | 39501篇 |
免费 | 3213篇 |
国内免费 | 4888篇 |
专业分类
测绘学 | 2599篇 |
大气科学 | 4935篇 |
地球物理 | 8264篇 |
地质学 | 19800篇 |
海洋学 | 3078篇 |
天文学 | 2233篇 |
综合类 | 3559篇 |
自然地理 | 3134篇 |
出版年
2024年 | 137篇 |
2023年 | 407篇 |
2022年 | 912篇 |
2021年 | 1062篇 |
2020年 | 902篇 |
2019年 | 955篇 |
2018年 | 5599篇 |
2017年 | 4751篇 |
2016年 | 3425篇 |
2015年 | 1076篇 |
2014年 | 1147篇 |
2013年 | 1035篇 |
2012年 | 1944篇 |
2011年 | 3654篇 |
2010年 | 2950篇 |
2009年 | 3144篇 |
2008年 | 2629篇 |
2007年 | 2985篇 |
2006年 | 646篇 |
2005年 | 736篇 |
2004年 | 810篇 |
2003年 | 783篇 |
2002年 | 616篇 |
2001年 | 450篇 |
2000年 | 488篇 |
1999年 | 630篇 |
1998年 | 534篇 |
1997年 | 470篇 |
1996年 | 468篇 |
1995年 | 365篇 |
1994年 | 358篇 |
1993年 | 309篇 |
1992年 | 276篇 |
1991年 | 182篇 |
1990年 | 151篇 |
1989年 | 129篇 |
1988年 | 98篇 |
1987年 | 71篇 |
1986年 | 57篇 |
1985年 | 47篇 |
1984年 | 32篇 |
1983年 | 29篇 |
1982年 | 26篇 |
1981年 | 32篇 |
1980年 | 30篇 |
1979年 | 15篇 |
1978年 | 9篇 |
1977年 | 5篇 |
1976年 | 9篇 |
1958年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
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
43.
Rapid economic developments in East Asian countries have inevitably resulted in environmental degradation in the surrounding seas, and concern for both the environment and protection from pollutants is increasing. Identification of sources of contaminants is essential to environmental pollution management. In this study, the provenance of anthropogenic lead (Pb), a major pollutant of Yellow Sea sediments, was determined for river mouth sediments, including those of the Changjiang, Huanghe, Han, and Geum Rivers, and for age-determined shelf core sediments through the measurement of Pb isotope ratios in the HCl-leached fraction using multi-collector inductively coupled plasma-mass spectrometry (MC ICP/MS). Anthropogenic Pb has accumulated in shelf core sediments since 1910, and its isotope ratios were estimated as 0.863–0.866 and 2.119–2.125 for 207Pb/206Pb and 208Pb/206Pb, respectively, from the mixing relationships of the two endmembers. River mouth sediments exhibited enough distinction in anthropogenic Pb isotope ratios to be discriminated: 0.874 (2.144) in the Huanghe, 0.856 (2.129) in the Han, 0.857 (2.122) in the Geum, and 0.854 (2.101) in the Changjiang for 207Pb/206Pb (208Pb/206Pb), respectively. Although isotope ratios of geogenic Pb in sediments dating before 1910 showed narrow ranges (0.842–0.845 and 2.088–2.100 for 207Pb/206Pb and 208Pb/206Pb, respectively), distinct isotope ratios in each core permitted source identification of sediments in the Yellow Sea based on geographic locations and the geogenic Pb of each river. By comparing the isotope ratios of the estimated anthropogenic Pb to source-related materials, the provenances of anthropogenic Pb in Chinese river sediments were presumed to be Chinese coal or ore, which is also a major source of atmospheric particulate Pb. The anthropogenic Pb in the shelf core sediments in the northern Yellow Sea originated from northern Chinese cities such as Beijing and Tianjin through atmospheric pathways. Pb isotope ratios indicated that Pb in Korean river sediments was characteristic of local Korean ores. 相似文献
44.
K. S. Rao Y. S. Rao H. K. Al Jassar 《Journal of the Indian Society of Remote Sensing》2008,36(2):123-136
Spaceborne Imaging Radar (SIR-C) data acquired over Gujarat, India in 1994 were processed and analysed using differnet techniques
applicable to polarimetric SAR data such as polarization signatures, polarization index, decomposition of the signal and polarization
phase difference and limited groundtruth data. It has been observed that multi-frequency polarimetric data enhances the potential
of retrieving geo-physical parameters. The polarization signatures are found to vary with the nature of the target. Target
decomposition of the returned signal will be useful for the classification of various features. Polarization Phase Difference
(PPD) gives good information about the vegetation parameters. 相似文献
45.
46.
47.
Lars E. Sjöberg 《Journal of Geodesy》2008,82(9):565-567
Through each of two known points on the ellipsoid a geodesic is passing in a known azimuth. We solve the problem of intersection
of the two geodesics. The solution for the latitude is obtained as a closed formula for the sphere plus a small correction,
of the order of the eccentricity of the ellipsoid, which is determined by numerical integration. The solution is iterative.
Once the latitude is obtained, the longitude is determined without iteration. 相似文献
48.
This paper introduces a new method for GPS signal acquisition, which is based on the repeatability of successive code phase
measurements and the M-of-N search algorithm. The performance of the proposed method in terms of probability of signal detection
is similar to that of traditional methods, except that the calculation of the probability of detection does not rely on the
noise distribution or the Carrier-to-Noise ratio (C/N0). The code phase repeatability-based method is presented along with equations for probability of detection and probability
of false detection. If the distribution of the noise is known, it also provides an estimate of the C/N0. The proposed method is illustrated for coherent and non-coherent acquisition and C/N0 estimation. 相似文献
49.
This paper presents a continuous version of the model of distribution dynamics to analyse the transition dynamics and implied
long-run behaviour of the EU-27 NUTS-2 regions over the period 1995–2003. It departs from previous research in two respects:
first, by introducing kernel estimation and three-dimensional stacked conditional density plots as well as highest density regions
plots for the visualisation of the transition function, based on Hyndman et al. (J Comput Graph Stat 5(4):315–336, 1996), and second, by combining Getis’ spatial filtering view with kernel estimation to explicitly account for the spatial dimension of the
growth process. The results of the analysis indicate a very slow catching-up of the poorest regions with the richer ones,
a process of shifting away of a small group of very rich regions, and highlight the importance of geography in understanding
regional income distribution dynamics.
相似文献
Manfred M. FischerEmail: |
50.