全文获取类型
收费全文 | 27915篇 |
免费 | 392篇 |
国内免费 | 360篇 |
专业分类
测绘学 | 781篇 |
大气科学 | 2096篇 |
地球物理 | 5407篇 |
地质学 | 9616篇 |
海洋学 | 2424篇 |
天文学 | 6855篇 |
综合类 | 67篇 |
自然地理 | 1421篇 |
出版年
2021年 | 213篇 |
2020年 | 248篇 |
2019年 | 309篇 |
2018年 | 646篇 |
2017年 | 620篇 |
2016年 | 776篇 |
2015年 | 438篇 |
2014年 | 750篇 |
2013年 | 1388篇 |
2012年 | 864篇 |
2011年 | 1135篇 |
2010年 | 1029篇 |
2009年 | 1351篇 |
2008年 | 1232篇 |
2007年 | 1244篇 |
2006年 | 1206篇 |
2005年 | 948篇 |
2004年 | 918篇 |
2003年 | 829篇 |
2002年 | 795篇 |
2001年 | 685篇 |
2000年 | 701篇 |
1999年 | 637篇 |
1998年 | 633篇 |
1997年 | 586篇 |
1996年 | 464篇 |
1995年 | 464篇 |
1994年 | 452篇 |
1993年 | 360篇 |
1992年 | 349篇 |
1991年 | 307篇 |
1990年 | 352篇 |
1989年 | 310篇 |
1988年 | 272篇 |
1987年 | 308篇 |
1986年 | 269篇 |
1985年 | 347篇 |
1984年 | 389篇 |
1983年 | 356篇 |
1982年 | 349篇 |
1981年 | 289篇 |
1980年 | 304篇 |
1979年 | 248篇 |
1978年 | 238篇 |
1977年 | 234篇 |
1976年 | 202篇 |
1975年 | 205篇 |
1974年 | 205篇 |
1973年 | 184篇 |
1972年 | 127篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
L. T. Handoko 《Earth, Moon, and Planets》2009,104(1-4):331-336
This short paper is a progress report on our experiences in Indonesia of collecting, integrating and disseminating both global and local scientific data across the country through the web. Our recent efforts are concentrated on improving local public access to global scientific data, and encouraging local scientific data to be more accessible for global communities. We have maintained a well-connected infrastructure and web-based information management systems to realize these objectives. This paper is especially focused on introducing the ARSIP system for mirroring global data and sharing local scientific data, and the newly developed Indonesian Scientific Index for integrating local scientific data through an automated intelligent indexing system. 相似文献
122.
T.A. McMahon R.E. Murphy M.C. Peel J.F. Costelloe F.H.S. Chiew 《Journal of Arid Environments》2008,72(10):1853-1868
This is the first of two papers that describe the surface hydrology of the Lake Eyre Basin (LEB) (1,140,000 km2) in central Australia and compares some key characteristics with those observed from arid regions globally. This paper concentrates on annual rainfall, whereas the second paper is devoted to streamflow. The first part describes the LEB's climate (arid to semi-arid), which is dominated by a subtropical high pressure ridge stretching latitudinally across central Australia. Then follow major analyses that include the characteristics of rainfall, wet and dry spell lengths and cumulative surpluses and deficiencies, rainfall trends and intra- and inter-decadal fluctuations, and the relationship between rainfall and El Niño-Southern Oscillation (ENSO). The paper concludes with six conclusions, the key ones being: the variability of the annual rainfall (based on the coefficient of variation) in the LEB is approximately 60% greater than that found for stations located in arid regions in the rest of the world; there is a bias towards longer lengths of dry years than observed in the rest of Australia; and, there is a significant lag correlation between rainfall and ENSO, particularly in the east and in the latter part of a year. 相似文献
123.
124.
Art R. T. Jonkers 《Geophysical Journal International》2007,169(2):646-658
The technique of bootstrapped discrete scale invariance allows multiple time-series of different observables to be normalized in terms of observed and predicted characteristic timescales. A case study is presented using the SINT2000 time-series of virtual axial dipole moment, which spans the past 2 Myr. It is shown that this sequence not only bears a clear signature of a preferred timescale of about 55.6 Ka, but additionally predicts similar features (of shorter and longer duration) that are actually observed on the timescales of historical secular variation and dipole reversals, respectively. In turn, the latter two empirical sources both predict the characteristic timescale found in the dipole intensity sequence. These communal scaling characteristics suggest that a single underlying process could be driving dynamo fluctuations across all three observed timescales, from years to millions of years. 相似文献
125.
126.
In this paper we present the H map, the 2D velocity field and the rotation curve of the galaxy NGC 784 obtained with the ByuFOSC2 scanning Fabry-Perot interferometer, attached at the prime focus of the 2.6-m telescope of Byurakan Observatory. The H image shows several HII condensations along the major axis of the galaxy. The galaxy has an asymmetric distribution of the H emission. The rotation curve is quite symmetric with a low gradient in the central part of the galaxy. 相似文献
127.
Spherical harmonic analysis is made of the grid point values of geopotential heights at 700 mb and 300 mb levels for the months April to August for the years 1967 and 1972. The year 1967 is a good monsoon year and 1972 is a bad monsoon year in India. Meridional transport of sensible heat is obtained in wave number domain using spherical harmonic coefficients at 500 mb level form=1 to 10 andn–m=0 to 10, wherem represents the wave number round the globe andn–m gives the numbers of zero points from north pole to south pole excluding the poles themselves.Large northward transports of sensible heat in the month of May and in the monsoon months at the subtropics are characteristic of bad monsoon. Wave 1 transports sensible heat southward (forn–m=0) and wave 2 transports sensible heat northward (forn–m=4). Strengthening of wave 1 is conducive to good monsoon year and strengthening of wave 2 is conducive to bad monsoon year. These are the same features obtained in Fourier analysis. The contrasting features exist in waves 1 and 2 both in good and in bad monsoon and are better defined in the present analysis than in the Fourier analysis of the earlier study. However, waves 1 and 2 reveal clearer contrast in the present analysis than in the Fourier analysis. Bad monsoon activity is associated with large divergence of heart at subtropics and large convergence of heat at extra tropics. 相似文献
128.
A. K. Jain U. B. Jayanthi K. Kasturirangan U. R. Rao 《Astrophysics and Space Science》1976,45(2):433-438
The paper presents experimental evidence for the existence of fast intensity fluctuations with time scales of the order of a minute in the X-ray emission from Cyg X-1 at energies greater than 29 keV. Spectral variations over time intervals of 20–25 min are also observed in the same energy range. Whereas, similar intensity and spectral fluctuations have been reported earlier at lower energies the observations presented here is the first evidence for the existence of similar fluctuations at high energies. 相似文献
129.
130.
T. Gold 《Earth, Moon, and Planets》1973,7(3-4):293-306