全文获取类型
收费全文 | 801篇 |
免费 | 279篇 |
国内免费 | 492篇 |
专业分类
测绘学 | 32篇 |
大气科学 | 837篇 |
地球物理 | 228篇 |
地质学 | 155篇 |
海洋学 | 161篇 |
天文学 | 46篇 |
综合类 | 55篇 |
自然地理 | 58篇 |
出版年
2024年 | 4篇 |
2023年 | 5篇 |
2022年 | 31篇 |
2021年 | 32篇 |
2020年 | 35篇 |
2019年 | 44篇 |
2018年 | 30篇 |
2017年 | 40篇 |
2016年 | 45篇 |
2015年 | 38篇 |
2014年 | 60篇 |
2013年 | 65篇 |
2012年 | 54篇 |
2011年 | 74篇 |
2010年 | 50篇 |
2009年 | 69篇 |
2008年 | 68篇 |
2007年 | 93篇 |
2006年 | 81篇 |
2005年 | 69篇 |
2004年 | 43篇 |
2003年 | 53篇 |
2002年 | 42篇 |
2001年 | 44篇 |
2000年 | 36篇 |
1999年 | 33篇 |
1998年 | 54篇 |
1997年 | 40篇 |
1996年 | 39篇 |
1995年 | 42篇 |
1994年 | 36篇 |
1993年 | 40篇 |
1992年 | 22篇 |
1991年 | 26篇 |
1990年 | 7篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1980年 | 1篇 |
排序方式: 共有1572条查询结果,搜索用时 328 毫秒
951.
Using the humidity profiles from the Atmospheric Infrared Sounder (AIRS) dataset, rainfall from the Tropical Rainfall Measuring Mission (TRMM) Global Precipitation Index (GPI), and surface winds from QuickSCAT (QSCAT) as well as SST from the Advanced Microwave Scanning Radiometer for NASA's Earth
Observing System (AMSR-E), we analyzed the structure of summer intraseasonal oscillation (ISO) over the western North Pacific region in 2003--2004. We find that the signal of 20--90-day oscillations in the western North Pacific originates from the equatorial Indian Ocean, and propagates eastward to
Philippine Sea and then moves northwestward to South China. The AIRS humidity data reveal that the boundary-layer moisture leads the mid-troposphere moisture during the ISO propagation. The positive SST anomaly may play an important role to moistening the boundary-layer, which preconditions the ISO propagation.Therefore, the intraseasonal SST anomaly could positively feed back to the atmosphere through moistening the boundary-layer,destabilizing the troposphere, and contributing to the northwestward propagation of the ISO in western North Pacific. On the other hand, the salient feature that the boundary-layer moisture anomaly leads mid-troposphere moisture does not exist in
ECMWF/TOGA analysis. 相似文献
952.
We investigate the effect of exotic matter in particular, hyperon matter on neutron star properties such as equation of state
(EoS), mass-radius relationship and bulk viscosity. Here we construct equations of state within the framework of a relativistic
field theoretical model. As hyperons are produced abundantly in dense matter, hyperon–hyperon interaction becomes important
and is included in this model. Hyperon–hyperon interaction gives rise to a softer EoS which results in a smaller maximum mass
neutron star compared with the case without the interaction. Next we compute the coefficient of bulk viscosity and the corresponding
damping time scale due to the non-leptonic weak process including Λ hyperons. Further, we investigate the role of the bulk
viscosity on gravitational radiation driven r-mode instability in a neutron star of given mass and temperature and find that
the instability is effectively suppressed.
相似文献
953.
During the latest several decades, there has been considerable interest in revealing the relationship between El Niño–southern oscillation (ENSO) and hydro‐meteorological variables. The oscillation is characterized by a simple index, the southern oscillation index (SOI). However, thus far, there is little evidence for the influence of ENSO in Korea and Japan. The influence of ENSO has also been studied in South Korea, but the estimated results are still qualitative and show an indirect relationship between ENSO and hydro‐meteorological variables. In this study we use simple approaches to reveal the quantitative and direct correlation between SOI and the monthly precipitation at five stations distributed over South Korea. The monthly precipitation data are transformed into nonexceedance probability time series because the data cannot be normally distributed by applying the usual transformations. The SOI is classified into five categories according to their values. Additionally, to detect the nonlinear relationship between categorized SOI and nonexceedance probability of the monthly precipitation, we use Kendall's τ, a nonparametric test. Significant correlations between the categorized SOI and the transformed precipitation are detected. Generally, the monthly precipitation is influenced by a La Niña event with a lag time of 4 months for southern coastal areas and a lag time of 5 months for middle to high regions in South Korea. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
954.
CISK,EVAPORATION-WIND FEEDBACK MECHANISM AND 30—60 DAY OSCILLATIONS IN THE TROPICAL ATMOSPHERE 下载免费PDF全文
A baroclinic semi-geostrophic model with evaporation-wind feedback mechanism(EWFM)and CISK is established,two non-dimensional parameters a and η are introduced to representEWFM and CISK,respectively.Analytic solutions of the model system are obtained,dynamicsanalyses and the model atmosphere calculations further confirm that EWFM and CISK are veryimportant physical processes in leading to the low-frequency oscillations in the tropics. 相似文献
955.
956.
Xiao-Bin Zhang Rong-Xian Zhang Zhi-Ping Li National Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2005,5(6):579-586
We present results of a time-series CCD photometry of two blue stragglers in the open cluster M67 that are also oscillating variables, S1280 and S1284. The observations obtained on 11 nights confirmed the δ Scuti-like variability of the two stars. Four and five main pulsating frequencies are detected for S1280 and S1284, respectively, through a power spectral analysis. A preliminary mode identification indicates that the two stars are both in radial oscillation. Based on the nature of oscillation, the physical parameters of the two stars are determined, and their evolutionary status discussed. 相似文献
957.
958.
厄尔尼诺与太阳活动的50d振荡 总被引:8,自引:0,他引:8
本文分析研究了1981—1994年太阳辐射流量(2800MHz)、太阳黑子相对数、大气角动量和地球自转日长变化序列的50d振荡.振荡周期的变化范围从40d至60d,它们的变化规律极其相似。1981年-1994年期间发生的3次厄尔尼诺均出现在太阳活动的50d振荡周期的谷值时期.这说明太阳活动的50d振荡可能是引起厄尔尼诺事件的一种原因. 相似文献
959.
Characteristics of low-frequency oscillation intensity of air-sea turbulent heat fluxes over the northwest Pacific 总被引:1,自引:0,他引:1
Based on the daily turbulent heat fluxes and related meteorological variables datasets (1985–2006) from Objectively Analyzed
air-sea Fluxes (OAFlux) Project of Woods Hole Oceanographic Institution (WHOI), characteristics of low-frequency oscillation
intensity of air-sea turbulent heat fluxes over the northwest Pacific are analyzed by linear perturbation method and correlation
analysis. It can be concluded that: 1) the distribution of low-frequency oscillation intensity of latent heat flux (LHF) over
the northwest Pacific is mainly affected by that of low-frequency oscillation intensity of anomalous air-sea humidity gradient
(Δq′) as well as mean air-sea humidity gradient (), while the distribution of low-frequency oscillation intensity of sensible heat flux (SHF) is mainly affected by that of
low-frequency oscillation intensity of anomalous air-sea temperature gradient (ΔT′). 2) The low-frequency oscillation of turbulent heat fluxes over the northwest Pacific is the strongest in winter and the
weakest in summer. And the seasonal transition of low-frequency oscillation intensity of LHF is jointly influenced by those
of low-frequency oscillation intensity of Δq′, low-frequency oscillation intensity of anomalous wind speed (U′), and mean wind speed (Ū), while the seasonal transition of low-frequency oscillation intensity of SHF is mainly influenced by those of low-frequency
oscillation intensity of ΔT′ and Ū. 3) Over the tropical west Pacific and sea areas north of 20°N, the low-frequency oscillation of LHF (SHF) is mainly influenced
by atmospheric variables q
a
′ (T
a
′) and U′, indicating an oceanic response to overlying atmospheric forcing. In contrast, over the tropical eastern and central Pacific
south of 20°N, q
s
′ (T
s
′) also greatly influences the low-frequency oscillation of LHF (SHF).
Supported by National Natural Science Foundation of China (Grant No. 40675028) and National Basic Research Program of China
(Grant No. 2006CB403600) 相似文献
960.
Radan Huth Lucie Pokorn Josef Bochní
ek Pavel Hejda 《Journal of Atmospheric and Solar》2009,71(13):1471-1483
We examine joint effects of the solar activity and phase of the quasi-biennial oscillation (QBO) on modes of low-frequency variability of tropospheric circulation in the Northern Hemisphere in winter. The winter months (December–March) are stratified by the solar activity into two (below/above median) classes, and each of these classes is subdivided by the QBO phase (west or east). The variability modes are determined by rotated principal component analysis of 500 hPa heights separately in each class of solar activity and QBO phase. Detected are all the modes known to exist in the Northern Hemisphere. The solar activity and QBO jointly affect the shapes, spatial extent, and intensity of the modes; the QBO effects are, however, generally weaker than those of solar activity. For both solar maxima and minima, there is a tendency to the east/west phase of QBO to be accompanied by a lower/higher activity of zonally oriented modes and increased meridionality/zonality of circulation. This means that typical characteristics of circulation under solar minima, including a more meridional appearance of the modes and less activity of zonal modes, are strengthened during QBO-E; on the other hand, circulation characteristics typical of solar maxima, such as enhanced zonality of the modes and more active zonal modes, are more pronounced during QBO-W. Furthermore, the zonal modes in the Euro-Atlantic and Asian sectors (North Atlantic Oscillation, East Atlantic pattern, and North Asian pattern) shift southwards in QBO-E, the shift being stronger in solar maxima. 相似文献