全文获取类型
收费全文 | 12485篇 |
免费 | 1470篇 |
国内免费 | 1529篇 |
专业分类
测绘学 | 619篇 |
大气科学 | 1874篇 |
地球物理 | 3736篇 |
地质学 | 5143篇 |
海洋学 | 1164篇 |
天文学 | 1177篇 |
综合类 | 698篇 |
自然地理 | 1073篇 |
出版年
2024年 | 43篇 |
2023年 | 166篇 |
2022年 | 352篇 |
2021年 | 463篇 |
2020年 | 387篇 |
2019年 | 374篇 |
2018年 | 792篇 |
2017年 | 624篇 |
2016年 | 718篇 |
2015年 | 561篇 |
2014年 | 689篇 |
2013年 | 742篇 |
2012年 | 628篇 |
2011年 | 668篇 |
2010年 | 638篇 |
2009年 | 642篇 |
2008年 | 582篇 |
2007年 | 512篇 |
2006年 | 429篇 |
2005年 | 324篇 |
2004年 | 320篇 |
2003年 | 295篇 |
2002年 | 287篇 |
2001年 | 266篇 |
2000年 | 235篇 |
1999年 | 341篇 |
1998年 | 386篇 |
1997年 | 330篇 |
1996年 | 330篇 |
1995年 | 244篇 |
1994年 | 236篇 |
1993年 | 191篇 |
1992年 | 176篇 |
1991年 | 141篇 |
1990年 | 159篇 |
1989年 | 125篇 |
1988年 | 98篇 |
1987年 | 98篇 |
1986年 | 89篇 |
1985年 | 66篇 |
1984年 | 56篇 |
1983年 | 48篇 |
1982年 | 51篇 |
1981年 | 54篇 |
1980年 | 49篇 |
1979年 | 41篇 |
1978年 | 32篇 |
1977年 | 32篇 |
1973年 | 35篇 |
1971年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
本文在已有数据处理方法的基础上,利用近代数值逼近理论,给出了从时空域角度描述地壳垂直运动过程的一种具体的函数解析形式。最后给出了一个实际算例。 相似文献
13.
Virtual Huanghe River System: Framework and Technology 总被引:2,自引:0,他引:2
LU Heli LIU Guifang SUN Jiulin 《中国地理科学(英文版)》2006,16(3):255-259
1 Introduction Huanghe (Yellow) River basin is located in 32°–42°N, 96°–119°E. The area of the catchment is more than 752,000km2. The river is 5464km long with a drop in elevation of 4830m. Among the whole area, the moun- tainous and stone area accounts for 29%, loess and hills area 46%, sandy area 11% and plain area 14%, respec- tively. Different natural landscapes exist in this area. The Huanghe River flows through the Loess Plateau, where the soil is eroded seriously (Wang, 2002;… 相似文献
14.
Pco2 of air and seawater samples from the East China Sea(ECS) were measured in situ in autumn, 1994,Ocean currents,terrestrial fluviation,biological activities,etc.,Pco2 char-acters in air and seawater were investigated,CO2 flux and its character in the East China Sea are discussed on the basis of the Pco2 profiles of air and seawater,It was clear that the nearshore was the source of CO2;and tht the oulter sea area was the sink of CO2; and that the shelf area of the EXS is a net sink for atmospheric CO2 in autumn. 相似文献
15.
16.
The conodont colour alteration index (CAI) is potentially valuable in thermal history investigations, but there are problems in its use. An approach is proposed herein to overcome the problem of establishing reliable geothermal palaeogradients in areas with burial metamorphism, based on knowledge of the stratigraphic succession thickness, the boundaries of chronostratigraphic units, and the age and duration of deformation episodes. Although also problematical that a correlation between CAI and Kübler index (KI) values does not exist, there are areas where CAI and KI values are notably consistent for the anchizone boundaries; however, anomalous correlations between CAI and KI values have also been found in some areas. A CAI anchizone (or ancaizone) is defined in order to enable CAI values to be used independently to establish a metamorphic zonation. 相似文献
17.
γ射线暴的研究进展(Ⅳ:特强γ射线暴和软γ重复暴 总被引:2,自引:0,他引:2
最近CGRO上的仪器观测到了两个迄今为止发现的最强的λ暴GB930131和GB940217,其光子最高能量均达GeV量级;GB930131的峰值计数率达2×10~6个光子s~(-1);而GB940217的持续时间竟长达90min。另外沉寂了多年的软重复暴源SGR1900 14和SGR1806-20的再次爆发也由BATSE发现。一系列的观测还发现这些软重复暴均与X射线源对应且与超新星遗迹成协。文中对特强暴和软重暴(SGR)的性质及研究进展作了较为详细的评述。 相似文献
18.
V. Majerník 《Astrophysics and Space Science》1996,240(1):133-139
Using the heuristic arguments of quantum physics we describe a new mechanism of the creation of short-living particles from the virtual ones in a stationary gravitation field. The mass of these particles is a function of the intensity of gravitation field. We suppose that the particles created in the gravitation field form a part of the non-baryonic dark matter. Having the intensity of gravitation field in a galaxy we can calculate the density of dark matter created in it by the vacuum quantum fluctuation. We calculate the distribution of this dark matter in a model galaxy and show that its total mass is comparable with the visible mass of the galaxy. 相似文献
19.
K. R. Subramanian R. Ramesh M. S. Sundara Rajan Ch. V. Sastry 《Astrophysics and Space Science》1996,243(1):259-262
Observations of the Sun at two frequencies (51 and 77 MHz) using the East-West arm of the Gauribidanur Radio heliograph are presented. 相似文献
20.
Z. Balog † A. J. Delgado ‡ A. Moitinho G. Frész † G. Kaszás † J. Vinkó E. J. Alfaro 《Monthly notices of the Royal Astronomical Society》2001,323(4):872-886
CCD photometry in Johnson UBV and Strömgren uvby systems and medium-resolution spectroscopy of the galactic open cluster NGC 7128 are presented. Spectral types of the brightest 12 stars in the cluster field were determined based on equivalent widths of the H α and the He i 6678-Å line. The spectroscopic observations also revealed two obvious and one probable Be-type stars showing H α emission. The analysis of the photometric diagrams gave a colour excess of E ( B − V )=1.03±0.06 mag, a distance modulus DM =13.0±0.2 mag and an age above 10 Myr. Time-resolved photometric observations obtained on one night resulted in the detection of short time-scale light variations of seven new and three already known variable stars in the cluster field. 相似文献