全文获取类型
收费全文 | 9430篇 |
免费 | 2043篇 |
国内免费 | 2746篇 |
专业分类
测绘学 | 1313篇 |
大气科学 | 1518篇 |
地球物理 | 2119篇 |
地质学 | 5088篇 |
海洋学 | 1571篇 |
天文学 | 370篇 |
综合类 | 929篇 |
自然地理 | 1311篇 |
出版年
2024年 | 77篇 |
2023年 | 260篇 |
2022年 | 531篇 |
2021年 | 676篇 |
2020年 | 563篇 |
2019年 | 628篇 |
2018年 | 626篇 |
2017年 | 570篇 |
2016年 | 641篇 |
2015年 | 595篇 |
2014年 | 723篇 |
2013年 | 791篇 |
2012年 | 747篇 |
2011年 | 700篇 |
2010年 | 684篇 |
2009年 | 713篇 |
2008年 | 649篇 |
2007年 | 580篇 |
2006年 | 521篇 |
2005年 | 381篇 |
2004年 | 281篇 |
2003年 | 238篇 |
2002年 | 221篇 |
2001年 | 234篇 |
2000年 | 228篇 |
1999年 | 236篇 |
1998年 | 160篇 |
1997年 | 159篇 |
1996年 | 135篇 |
1995年 | 114篇 |
1994年 | 114篇 |
1993年 | 84篇 |
1992年 | 76篇 |
1991年 | 51篇 |
1990年 | 28篇 |
1989年 | 25篇 |
1988年 | 29篇 |
1987年 | 19篇 |
1986年 | 24篇 |
1985年 | 13篇 |
1984年 | 8篇 |
1983年 | 10篇 |
1982年 | 13篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1979年 | 12篇 |
1976年 | 4篇 |
1958年 | 7篇 |
1957年 | 3篇 |
1954年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
STUDY ON GIS FOR YIELD ESTIMATION BY REMOTE SENSING IN JILIN MAIZE BELTSTUDYONGISFORYIELDESTIMATIONBYREMOTESENSINGINJILINMAIZ... 相似文献
12.
13.
J. Rajchl J. Bočcek D. Očenáš J. Škvarka P. Zimnikoval H. Murayama K. Ohtsuka 《Earth, Moon, and Planets》1995,68(1-3):479-486
Some results following from two contemporary photographical programs (Slovakia and Japan) for persistent meteor train spectra are compared. It shows that even though both programs are not too different according to their lenses and films used, the spectral interval detected is very different. In this respect prism as a dispersion element is more favourable than the grating with blaze wavelength near 610 nm. However, some results previously assumed as typicai for presented persistent trains-e.g. the forbidden Herzberg O2 emission, the NO2 continuum and OH red emissions-seem to be substanciated especially due to higher and linear dispersion of those grating spectra. 相似文献
14.
本文通过对成都10个重污染日进行天气学分析,将污染浓度与气象要素进行聚类、研究了重污染日形成原因及污染浓度与气象要素的关系。在此基础上,建立了SO_2、TSP日平均浓度分级预报方程。 相似文献
15.
1INTRODUCTION Since the first use in human genetic research in1966,allozyme has become the most popular genetic marker for population genetics studies for almost all groups of animals and plants(Lewontin and Hubby,1966;Murphy et al.,1996).In the past seve… 相似文献
16.
HUANGGuoqiang DONGShuanglin WANGFang 《中国海洋大学学报(英文版)》2005,4(1):56-60
Attractabilities of different diets and dietary selectivity of Chinese shrimp, Fenneropenaeus chinensis were studied through behavior observation and feeding experiment, respectively. The five diets used in the experiment are: Fish Flesh (FF), Shrimp Flesh (SF), Clam Foot (CF), Polychaete Worm (PW), and Formulated Diet (FD). No significant differences of attractability exist between any two different diets when every two natural diets or all five diets are provided simultaneously. On the other hand, significant differences of attractability exist between FD and every single natural diet when they are provided simultaneously. Results of behavioral observation indicate that natural diets are more attractive than FD. In feeding experiment, Chinese shrimp has distinct selectivity on different diets. It positively selects CF and PW, negatively selects FF and SF, and excludes FD absolutely. The results of the present studies indicate that the dietary selectivity of shrimp was based not only on the attractabilities of the diets, but also on the responses such as growth and food conversion. 相似文献
17.
本文根据石油地质勘探的最新资料和元-济人工地震地壳测深剖面相应地段重新解释的结果,分析了邢台7.2级地震的构造背景和发震断裂。研究结果表明,7.2级地震震中位于束鹿断陷盆地南部次凹的东缘,该次凹发育在由新河断裂等4条缓倾铲形正断裂分制围限地台盖层而成的“斛”状构造块体上,块体之下的地壳中存在两条倾向相反的高角度断裂;地震与断陷主断裂及其控制的断陷盆地并非是简单的对应关系,7.2级地震的发震断裂不是单一的缓倾铲形新河断裂或其下方的高角度的F_3断裂和深部的东断裂,而是它们的组合,且高角度断裂是发震断裂的主要部分 相似文献
18.
The distribution of L absorption lines has been investigated in the fractal scheme. It is found that (1) the L absorption clouds distribute completely different from that of galaxies; (2) the L absorption clouds are anti-associated with galaxies and quasars. These results may imply that there are two kinds of objects formed by different processes of clustering. This is favourable for the cosmic-string theory on the formation of large-scale structure of the Universe. In the string model, the objects can be divided into two kinds according to their clustering with or without string loops as their initial density perturbation.On leave from the Center of Astrophysics, University of Science and Technology of China, Hefei, P.R. China. Y. Chu is a research fellow of Alexander von Humboldt-Foundation. 相似文献
19.
Ni Xiang-bin Jiang Yao-tiao Chen Zai-zhang Fang Cheng 《Chinese Astronomy and Astrophysics》1985,9(4):273-277
We propose a new heating mechanism of faculae. We think that the formation of faculae is a result of the Joule dissipation of the Hall current generated by the interaction of the convection field of granules in an active region and the inter-granular magnetic field. For a region to generate effectively Hall current, its characteristic length must be such that the magnetic Reynolds number is less than 1. The equation of energy balance in the facula region is .For five observational models of faculae, we calculated the corresponding velocity fields, and the results are in basic agreement with the observed fields. The present mechanism explains the dependence of the facula brightness on the magnetic and velocity fields, the apparent distribution of the faculae on the solar disk and suggest a possible interpretation of the five structures of faculae. 相似文献
20.