全文获取类型
收费全文 | 376篇 |
免费 | 25篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 8篇 |
大气科学 | 72篇 |
地球物理 | 107篇 |
地质学 | 123篇 |
海洋学 | 12篇 |
天文学 | 62篇 |
自然地理 | 20篇 |
出版年
2023年 | 2篇 |
2021年 | 14篇 |
2020年 | 7篇 |
2019年 | 6篇 |
2018年 | 17篇 |
2017年 | 18篇 |
2016年 | 25篇 |
2015年 | 22篇 |
2014年 | 26篇 |
2013年 | 32篇 |
2012年 | 24篇 |
2011年 | 10篇 |
2010年 | 21篇 |
2009年 | 16篇 |
2008年 | 16篇 |
2007年 | 10篇 |
2006年 | 10篇 |
2005年 | 6篇 |
2004年 | 6篇 |
2003年 | 4篇 |
2002年 | 9篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1990年 | 2篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1977年 | 2篇 |
1974年 | 4篇 |
1968年 | 2篇 |
1965年 | 2篇 |
1962年 | 2篇 |
1958年 | 1篇 |
1957年 | 4篇 |
1955年 | 3篇 |
1954年 | 1篇 |
1953年 | 6篇 |
1952年 | 3篇 |
1951年 | 4篇 |
1950年 | 3篇 |
1949年 | 3篇 |
1948年 | 4篇 |
排序方式: 共有404条查询结果,搜索用时 31 毫秒
31.
F. Steinhauser W. Mörikofer H. Israël M. Toperczer 《Meteorology and Atmospheric Physics》1953,6(1):114-128
Ohne Zusammenfassung 相似文献
32.
33.
Innes D.E. Inhester B. Srivastava N. Brekke P. Harrison R.A. Matthews S.A. Noëns J.C. Schmieder B. Thompson B.J. 《Solar physics》1999,186(1-2):337-361
The structure and dynamics of the initial phases of a coronal mass ejection (CME) seen in soft X-ray, extreme ultraviolet and optical emission are described. The event occurred on the SW limb of the Sun in active region AR 8026 on 9 April 1997. Just prior to the CME there was a class C1.5 flare. Images taken with the Extreme Ultraviolet Imaging Telescope (EIT) reveal the emergence of a candle-flame shaped extreme ultraviolet (EUV) cavity at the time of the flare. Yohkoh images, taken about 15 min later, show that this cavity is filled with hot X-ray emitting gas. It is most likely that this is the site of the flare. Almost simultaneous to the flare, an H surge or small filament eruption occurs about 50 arc sec northwards along the limb from the EUV cavity. At both the site of the core of the hot, EUV cavity and the filament ejection are X-ray jets. These jets seem to be connected by hot loops near their bases. Both jets disappear within a few minutes of one another.Clear evidence of the CME first appeared in the Large Angle Spectrometric Coronagraph (LASCO) and EIT images 40 min after the flare and onset of the filament ejection. It seems to come from a region between the two X-ray jets. This leads to the speculation that magnetic field reconnection near one footpoint of a loop system triggers reconnection near its other footpoint. The loop system is destabilized and ultimately gives rise to the CME. This possibility is supported by magnetic field and H images taken when the active region was at disk center which show that the active region had a double bipole structure with dark H filaments between the bipoles. 相似文献
34.
Mathieu Bringer Michel Boër Cedric Peignot Gérard Fontan Colette Mercé 《Experimental Astronomy》2001,12(1):33-48
We have developped a new method for the scheduling ofastronomical automatic telescopes, in the framework of theautonomous TAROT instrument. The MAJORDOME software canhandle a variety of observations, constrained, periodic,etc., and produces a timeline for the night, which may bemodified at any time to take into account the specificconditions of the night. The MAJORDOME can also handletarget of opportunity observations without delay. 相似文献
35.
Matheron (1971) proposed an approximation of the extension variance in IR. We propose in this note an extension of this formula in IR 2 , based on a MacLaurin formula. Its application is shown in an example, the estimation of the maximum depressional storage of a soil surface. 相似文献
36.
Doppler tracking of artificial satellites has been applied to determine the pole components through an experiment called MEDOC.
In addition to developing scientific aspects dealing with polar motion, it is proposed to promote new observational techniques
and to investigate the possibility of operating an international permanent service.
So far, nearly two years of bi-daily solutions have been derived. Each improvement of computational procedures, data processing
and station component determination has contributed to better precision in the computed pole positions.
MEDOC pole coordinate solutions show good agreement with DMA and BIH global solutions corrected for annual terms. Differences
of the smoothed values are less than one meter for both components.
The MEDOC experiment was initiated by the GRGS (Groupe de Recherches de Géodésie Spatiale) and took place in 1977 and 1978.
The experiment as presently organized will continue up to 1980. Future improvements are still foreseen by increasing the number
of observing sites and refinement of the force models, but already international involvement is taking place in the MEDOC
experiment. 相似文献
37.
Hydrographic structure of the water column, dissolved nutrient concentrations and the distribution of suspended particulate matter were recorded from CDT measurements and Niskin bottles sampling on the continental slope of the Bay of Biscay and on the axis of Capbreton canyon. Ascorbate extraction was applied here for the first time on marine suspended particles to determine the content of reactive Fe- and Mn-oxides, and P associated with Fe-oxides. Hydrographic structure of the south-eastern part of the Bay of Biscay did not change during the last three decades. Particulate organic carbon (POC) contents dropped strongly with depth, showing that organic matter mineralization was efficient in the water column. Organic matter mineralized in the water column had a Redfield N:P ratio. POC percent of particles collected at depth were higher during a bloom period, suggesting that some new organic matter reached the bottom. Contents of Fe and Mn extracted with the ascorbate leaching solution showed that suspended particles originated from the Gironde estuary, one of the major sources of particles in the Bay of Biscay. Intermediate and deeper nepheloid layers occurred in the Capbreton canyon. Particles of nepheloid layers were enriched in Mn- and Fe-oxides because they originated from resuspension of surface sediment. 相似文献
38.
CK chondrites are the only group of carbonaceous chondrites with petrologic types ranging from 3 to 6. It is commonly reported than ~15 vol% of CK4–6 samples are composed of chondrules. The modal abundance of chondrules estimated here for 18 CK3–6 (including five CK3s) ranges from zero (totally recrystallized) to 50.5%. Although almost all chemically re‐equilibrated with the host matrix, we recognized in CK3s and Tanezrouft (Tnz) 057 (CK4) up to 85% of chondrules as former type I chondrules. Mean diameters of chondrules range from 0.22 to 1.05 mm for Karoonda (CK4) and Tnz 057 (CK4), respectively. Up to ~60% of chondrules in CK3–4 are surrounded by igneous rims (from ~20 μm to 2 mm width). Zoned olivines were found in unequilibrated chondrules from DaG 431 (CK3‐an), NWA 4724 (CK3.8), NWA 4423 (CK3.9), and Tnz 057 (CK4). We modeled Fe/Mg interdiffusion profiles measured in zoned olivines to evaluate the peak metamorphic temperatures and time scales of the CK parent body metamorphism, and proposed a two‐stage diffusion process in order to account for the position of inflection points situated within chondrules. Time scales inferred from Fe/Mg interdiffusion in olivine from unequilibrated chondrules are on the order of tens to a hundred thousand years (from 50 to 70,000 years for peak metamorphic temperatures of 1140 and 920 K, respectively). These durations are longer than what is commonly accepted for shock metamorphism and shorter than what is required for nuclide decay. Using the concept of a continuous CV–CK metamorphic series, which is reinforced by this study, we estimated peak metamorphic temperatures <850 K for CV, 850–920 K for CK3, and 920–1140 K for CK4–6 chondrites considering a duration of 70,000 years. 相似文献
39.
Gisèle Krysztofiak Yao Veng Té Gwenaël Berthet Geoffrey C. Toon Fabrice Jégou 《大气与海洋》2015,53(1):89-101
AbstractCarbonyl sulphide (OCS) is an important precursor of sulphate aerosols and consequently a key species in stratospheric ozone depletion. The SPectromètre InfraRouge d'Absorption à Lasers Embarqués (SPIRALE) and shortwave infrared (SWIR) balloon-borne instruments have flown in the tropics and in the polar Arctic, and ground-based measurements have been performed by the Qualité de l'Air (QualAir) Fourier Transform Spectrometer in Paris. Partial and total columns and vertical profiles have been obtained to study OCS variability with altitude, latitude, and season. The annual total column variation in Paris reveals a seasonal variation with a maximum in April–June and a minimum in November–January. Total column measurements above Paris and from SWIR balloon-borne instrument are compared with several MkIV measurements, several Network for the Detection of Atmospheric Composition Change (NDACC) stations, aircraft, ship, and balloon measurements to highlight the OCS total column decrease from tropical to polar latitudes. OCS high-resolution in situ vertical profiles have been measured for the first time in the altitude range between 14 and 30?km at tropical and polar latitudes. OCS profiles are compared with Atmospheric Chemistry Experiment (ACE) satellite measurements and show good agreement. Using the correlation between OCS and N2O from SPIRALE, the OCS stratospheric lifetime has been accurately determined. We find a stratospheric lifetime of 68?±?20 years at polar latitudes and 58?±?14 years at tropical latitudes leading to a global stratospheric sink of 49?±?14?Gg?S?y?1. 相似文献
40.
The evolution of the 27-day recurrence in the series of two solar indices (Wolf number WN and 10.7 cm radio flux F) and two geomagnetic indices (Dst and ζ, variance of the geomagnetic field recorded at a magnetic observatory) have been studied over the 1957 – 2007 time
span. Spectral energies contained in two period domains (25 – 27.3 and 27.3 – 31 days), designated as E
1 and E
2, have been computed. Whereas the evolution of E
1 is the same for the four indices, that of E
2 is essentially different for WN and F on the one hand, Dst and ζ on the other hand. Some general conclusions on the dynamics of the solar outer layers are inferred from these results.
First the solar activity, as measured by WN, and when averaged over a few years, evolves in the same way whatever the latitude.
Second, two families of coronal holes (CHs) are identified; the rapidly and the slowly rotating CHs evolve quite differently. 相似文献