全文获取类型
收费全文 | 155篇 |
免费 | 3篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 11篇 |
地球物理 | 28篇 |
地质学 | 51篇 |
海洋学 | 14篇 |
天文学 | 19篇 |
自然地理 | 34篇 |
出版年
2020年 | 3篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 4篇 |
2012年 | 7篇 |
2010年 | 6篇 |
2009年 | 6篇 |
2008年 | 4篇 |
2007年 | 2篇 |
2006年 | 3篇 |
2005年 | 3篇 |
2004年 | 4篇 |
2003年 | 8篇 |
2002年 | 3篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 2篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1957年 | 1篇 |
1954年 | 1篇 |
1925年 | 2篇 |
1910年 | 6篇 |
1908年 | 4篇 |
1905年 | 2篇 |
1899年 | 1篇 |
1898年 | 3篇 |
1895年 | 1篇 |
1875年 | 1篇 |
排序方式: 共有158条查询结果,搜索用时 109 毫秒
121.
122.
123.
124.
In 2011, a large repository of resting cysts of the toxic dinoflagellate Alexandrium catenella was discovered in the sediments of the Onapua/Opua inlet located off Tory Channel, Queen Charlotte Sound. The inlet is a potential source of infection for other areas, such as the major mussel-growing areas of Port Underwood and Pelorus Sound. This study aimed to establish whether the dinoflagellate was a new arrival in the Sounds or had existed unnoticed in this isolated embayment for some time. Alexandrium catenella cysts were identified to a depth of 20–21?cm within the sediment cores, corresponding to a date estimated by radioisotope (210Pb and 137Cs) and Pinus radiata pollen distribution to at least the mid 1970s. Over this time span, resident populations of A. catenella have not become established beyond the confines of Queen Charlotte Sound, suggesting it does not pose an imminent threat of doing so unless increasingly intense and prolonged blooms result in more widespread cyst dispersal. 相似文献
125.
Scintillometer Intercomparison Study—Continued 总被引:3,自引:3,他引:0
J. Kleissl C. J. Watts J. C. Rodriguez S. Naif E. R. Vivoni 《Boundary-Layer Meteorology》2009,130(3):437-443
An earlier study by one of the authors reported significant differences of up to 21% in linear regression slopes between six
Kipp & Zonen large-aperture scintillometers. In this note, the consistency of this increasingly popular instrument for measuring
sensible heat fluxes at the km scale was quantified by comparing measurements from four Scintec boundary-layer scintillometers
and one large-aperture scintillometer over nearly identical transects. The Kipp & Zonen instrument’s sensible heat fluxes
were more than 20% larger than those from the Scintec instruments, while the difference in regression slopes amongst the Scintec
instruments was 3% or less. 相似文献
126.
We report the results of a numerical investigation of three methods of cosmic X-ray spectral reduction, with an emphasis on the apodization technique of Dolan (1972). The study is carried out in the energy range 10–100 keV on pulse height distributions which were synthesized from simple X-ray source spectra with predetermined parameters. The spectral response function used was that of a balloon-borne, large area, xenon-filled proportional counter; however, we believe that our results are generally relevant to other non-dispersive systems such as scintillators and low energy (1–10 keV) proportional counters. We agree that the ill-conditioned energy resolution matrix cannot be inverted using standard procedures without propagating unacceptable errors. The apodization solution was investigated as a function of counter resolution, fluorescence escape probability, extent of energy window, number of pulse height channels, dataS/N ratio, and the so-called apodization instrument factor. We conclude that in most circumstances apodization should be the preferred reduction technique, but that the present widely and improperly used minimum –x
2 method may be useful as the final step in obtaining refined spectral parameters estimates. 相似文献
127.
Summary. A total of 3708 1 × 1° free-air gravity anomaly averages have been used to construct a new 1 × 1° gravimetric geoid of the Northwest Pacific Ocean. The 1 × 1° averages are based on a compilation of 147000 surface ship and pendulum gravity measurements. The gravimetric geoid reveals information in the geoid of the Northwest Pacific not present in currently used satellite derived models. The RMS difference between the 1 × 1° geoid and satellite derived models is about ±6 m. Difference geoid undulations range from a maximum of +19 m over the Hawaiian ridge to a minimum of −31 m over the junction of the Kuril and Aleutian trenches. The Hawaiian swell is associated with a geoidal high of up to +15 m with wavelengths of about 2200 km and the topographic rises seaward of deep-sea trenches are associated with geoidal highs of up to 4m with wavelengths of about 220–900 km. The main difference between the gravimetric geoid and the satellite derived models occurs over the Pacific basin where discrepancies reach +10 m with wavelengths of 4000 km. The agreement between the gravi-metric geoid and Skylab-4 and Geos-3 altimeter data is close for wavelengths greater than about 300 km but poor for shorter wavelengths. 相似文献
128.
129.
Previous sonar surveys show that the north flank of Tenerife has been subject to at least four major landslides during the past 1 Ma. The youngest, Icod, affected the region to the north of the Teide-Pico Viejo complex, the world's third highest oceanic volcano. Recently, we obtained the first detailed acoustic images of Icod using a deep-tow side-scan sonar. The images suggest that Tenerife's north flank has experienced at least two types of flow deposit in the recent past. The older flow deposit, Icod I, is characterised by a 15- to 20-km-wide, >65-km-long, chaotic debris avalanche deposit which includes several very large blocks. We believe the deposit to be ~170 ka, and that it represents the mass-wasting products of the Cañadas edifice, remnants of which are now found in the Las Cañadas caldera wall. The younger flow deposit, Icod II, associated with a shute in its proximal part, appears to have produced a less chaotic deposit in its distal part which clearly preserves flow structures such as latitudinal boulder ridges and longitudinal shear structures. The sonar images cannot determine how much younger Icod II is than Icod I, although it is likely that they are a consequence of the same lateral collapse event. There is evidence from the shute area for erosional scour and sediment deposition since the Icod landslide. If this is correct, then it suggests that mass wasting is an ongoing process that has already started to modify the Teide-Pico Viejo complex itself. 相似文献
130.
An examination of the relationship between large organizations and local labour markets which draws attention to the role of the extended internal labour market (EILM). This paper explores recruitment strategies in the local labour market amongst 52 major employers in the metal sectors in the Sheffield local labour market. It shows how dependence on the external labour market rather than the internal labour market varies with the different occupations recruited within the local area and that, in some occupations, the EILM plays an important role. Where recruitment difficulties are experienced there are a variety of responses, all of which have particular implications for the amount and type of labour sought from the external labour market. The paper concludes by arguing for a greater emphasis on the recruitment strategies of larger firms in employer surveys to provide new insights into the operation of local labour markets and, in particular, the operation of the EILM. 相似文献