全文获取类型
收费全文 | 139篇 |
免费 | 9篇 |
国内免费 | 9篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 12篇 |
地球物理 | 40篇 |
地质学 | 53篇 |
海洋学 | 33篇 |
天文学 | 8篇 |
综合类 | 4篇 |
自然地理 | 3篇 |
出版年
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 9篇 |
2017年 | 7篇 |
2016年 | 9篇 |
2015年 | 1篇 |
2014年 | 6篇 |
2013年 | 3篇 |
2012年 | 8篇 |
2011年 | 6篇 |
2010年 | 8篇 |
2009年 | 5篇 |
2008年 | 13篇 |
2007年 | 10篇 |
2006年 | 3篇 |
2005年 | 2篇 |
2004年 | 3篇 |
2003年 | 7篇 |
2002年 | 3篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 6篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 6篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1987年 | 2篇 |
1983年 | 2篇 |
1979年 | 1篇 |
1974年 | 1篇 |
1966年 | 1篇 |
1964年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有157条查询结果,搜索用时 15 毫秒
31.
32.
Masaya Toyokawa Kaoru Aoki Satoshi Yamada Akira Yasuda Yusuke Murata Tomohiko Kikuchi 《Journal of Oceanography》2011,67(2):209-218
We surveyed the distribution of colonies of polyps of Aurelia
aurita sensu lato (s.l.) in Mikawa Bay, Japan. First, we surveyed the distribution of ephyrae of A. aurita s.l. at 75 stations encompassing the whole of Mikawa Bay in early 2008. A total of 37 ephyrae were sampled mostly from fishing
ports. Ephyrae were most abundant around the islands located near the mouth of the bay, and decreased from the western part
to the eastern part of Mikawa Bay. Next, we selected five fishing ports in Mikawa Bay where ephyrae occurred and surveyed
the underside of floating piers and underwater overhangs of wharfs. We found dense colonies of polyps of A. aurita s.l. under nearly all of the floating piers at the two islands located near the mouth of the bay. Fitting a logistic regression
model to the dataset showed that the percentage coverage of Aurelia polyps was significantly greater at the two islands compared with the other locations. In addition, the coverage of Aurelia polyps was greater when the coverage of other fouling organisms was in the range of 65–90%, and the coverage of Aurelia polyps was lower on floating piers with a vinyl surface and on concrete wharfs. The combined distribution of polyp colonies
of A. aurita s.l. in Ise Bay and Mikawa Bay suggested that A. aurita s.l. in the two bays probably forms a single population and shoals of medusae mainly originate from protected harbors along the
mouth-part of the bays. 相似文献
33.
Hisham?A.?GahlanEmail author Shoji?Arai Fawzy?F.?Abu El-Ela Akihiro?Tamura 《Contributions to Mineralogy and Petrology》2012,163(2):225-241
Ultramafic cumulates, mainly crustal true wehrlites, were discovered and described in the mantle–crust transition zone (MTZ)
and the extremely lower layered gabbro sequence of the Ras Salatit ophiolite, Central Eastern Desert, Egypt. They form either
boudinaged lensoidal tabular bodies or interdigitated layers often concordant with the planolinear fabrics of the Ras Salatit
ophiolite rocks. The contact between wehrlites and the host MTZ dunite or layered gabbro is razor sharp, lobate and/or sinuous,
without chilled margins or any visible deformations. The Ras Salatit wehrlites are orthopyroxene-free and composed mainly
of olivine and clinopyroxene. They are texturally equilibrated and show a characteristic poikilitic texture. Crystallization
order of the Ras Salatit wehrlites is olivine/spinel followed by clinopyroxene with the absence of plagioclase. Olivine and
clinopyroxene of the Ras Salatit wehrlites are compositionally uniform and conspicuously high in Mg#, mostly around 0.93 and
0.92, respectively. Moreover, the clinopyroxene shows low Ti and Al contents coupled with marked depletion in LILE. The calculated
melt in equilibrium with clinopyroxene from the Ras Salatit wehrlites is largely similar to lavas from the Izu-Bonin forearc.
Given the above characteristics, the Ras Salatit wehrlites were produced by crystal accumulation from a hydrous depleted basaltic/tholeiitic
melt corresponding to temperatures between 1,000 and 1,100°C at the oceanic crustal pressure (~2 kbar). The involved hydrous
tholeiitic melt has been probably formed by fluid-assisted partial melting of a refractory mantle source (similar to the underlying
harzburgites) in a somewhat shallow sub-arc environment. 相似文献
34.
Hafiz U. Rehman Tahseenullah Khan Hao‐Yang Lee Sun‐Lin Chung Mamoru Murata M. Qasim Jan 《Island Arc》2019,28(6)
We report Permian (ca. 272 Ma ±5.4 Ma) felsic dykes that intrude into the Neoproterozoic (ca. 750 Ma) magmatic suite of the Nagar Parkar Igneous Complex (NPIC), the western extension of the Malani Igneous Suite (MIS). The NPIC consists of Neoproterozoic basement amphibolites and granites (riebeckite–aegirine gray granites and the biotite–hornblende pink granites), all of which are intruded by several generations of mafic and felsic dykes. Granitic magmatism occurred in the Late Neoproterozoic (ca. 750 Ma) due to the subduction‐, followed by the rift‐related tectonic regime during the breakup of the Rodinia supercontinent. U–Th–Pb zircon and monazite CHIME age data of 700–800 Ma from the earlier generation porphyritic felsic dykes suggest the dyke intrusion was coeval or soon after the emplacement of the host granites. Our findings of Permian age orthophyric felsic dykes provide new insights for the prevalence of active tectonics in the MIS during late Paleozoic. Textural features and geochemistry also make the orthophyric dykes distinct from the early‐formed porphyritic dykes and the host granites. Our newly obtained age data combined with geochemistry, suggest the existence of magmatism along the western margin of India (peri‐Gondwana margin) during Permian. Like elsewhere in the region, the Permian magmatism in the NPIC could be associated with the rifting of the Cimmerian micro‐continents from the Gondwana. 相似文献
35.
长牡蛎(Crassostrea gigas)微卫星克隆快速分离及特性分析 总被引:22,自引:2,他引:22
采用磁珠杂交选择和PCR筛选法,从长牡蛎DNA选择片段文库中,快速分离含有微卫星序列的阳性克隆。结果表明,在筛选的200个白色菌落中,56个克隆含有重复次数5以上的微卫星序列,其中41个(20.5%)有随机侧翼区,可以进行引物设计,12个缺乏足够的侧翼序列,3个为中断的微卫星序列。此外,还获得两个小卫星克隆。在获得的微卫星序列中,完全的占54.7%,不完全的占20.8%,复合的占24.5%。除探针中使用的CA重复单元外,还观察到CT、ACT、CGCA、CACT、GACT、GCAC、CCTTA和CCTCA的重复序列。微卫星重复次数主要集中在5-30次之间,占71.7%,最高为60次。本研究中构建的长牡蛎(CA)n富集微卫星文库将为以后开发未知微卫星标记提供帮助。 相似文献
36.
Masayuki Saigusa Kazushi Oishi Akihiro Ikumoto Hiroshi Iwasaki Michihiro Terajima 《Journal of Oceanography》2000,56(3):295-310
The emergence of small arthropods was studied in the boreal sea, Japan (Akkeshi, Hokkaido). In the shallow subtidal zone, two impeller pumps were set in the surface and bottom waters. The pumps ran continuously for 25 days (22 August-16 September, 1998), and invertebrates were sampled using a nylon net (300 to 500 m in mesh size). The small arthropods collected with the net belonged to 16 orders comprising about 60 taxa. In the dominant 23 taxa, a two-way ANOVA was applied to determine whether there was any significant difference in abundance between day and night and between surface and bottom. While emergence of 15 taxa (65%) was significantly different with regard to the day/night factor, that of the other 8 taxa (35%) was not. As to the difference between the two depths, the distribution of 15 taxa (65%) was significantly different. Furthermore, in 25 taxa for which over 100 specimens were collected in each of the two depths of water, emergence patterns were examined with regard to the synchrony with day/night and tidal cycles. There were various nocturnal patterns, and the strength of the synchrony with the day/night cycle was different for each species or group. Within the same taxa, nocturnal patterns were more clearly manifested in the surface water than in the bottom water. A tidal rhythm of emergence was only seen in zoeas of shrimp. Variations of the emergence patterns of benthic crustaceans are accounted for by a hypothesis that the frequency of swimming during day versus at night is different in each species. On the other hand, the emergence patterns of some zooplankton reflect by the daily rhythm of vertical migration or dispersal in the water column. 相似文献
37.
J. E. J. Lovell H. Hirabayashi H. Kobayashi Y. Murata P. G. Edwards G. A. Moellenbrock S. Horiuchi E. B. Fomalont S. Kameno K. M. Shibata 《New Astronomy Reviews》1999,43(8-10)
An overview and status report of the VLBI Space Observatory Programme is presented. 相似文献
38.
Sequences Characterization of Microsatellite DNA Sequences in Pacific Abalone(Haliotis discus hannai) 总被引:1,自引:0,他引:1
Kijima Akihiro 《中国海洋大学学报(英文版)》2007,(1)
1 Introduction Microsatellites or simple sequence repeats (SSRs) are tandemly repeated motifs of one to six bases found in all prokaryotic and eukaryotic genomes analysed to date (Zane et al., 2002). Due to their hyper-variable and co-dominant nature, relatively high abundance and random distribution in the genome, microsatellites are among the most efficient class of molecular markers. Such repeats display high polymorphism because of variation in repeat length and can be rapidly analysed t… 相似文献
39.
Primary productivity off Enshu-nada was measured by the13C method in September 1989. Primary productivity was estimated in a cold water mass developed off Enshu-nada for the first time. The obtained value was 469 mgC·m–2·d–1 and higher than those in the pelagic area of Kuroshio, but equivalent to those in the neritic and the Oyashio areas. It was indicated that cold water mass is the place where organic matter is produced actively. Extremely high chlorophylla of more than 5g·l–1 were found in the cold water mass. The high productivity was due to high standing crop of phyoplankton. Furthermore, calculated light efficiency and quantum yield showed consistent increase with depth and showed a maximum at 10% light level. Both were larger on the coastal side than those on the oceanic side of the Kuroshio current. 相似文献
40.
Meso-scale characteristics of disturbances that bring about atmospheric disasters in pre- and mature monsoon seasons in Bangladesh
are analyzed. Several types of meteorological instruments capable of observations with high temporal and spatial resolutions
were introduced for the first time in this area to capture the meso-scale structure of rainfall systems. We installed an automatic
weather station (AWS) and several automatic raingauges (ARGs) and utilized the weather radar of Bangladesh Meteorological
Department (BMD). From the radar image in the summer of 2001 (16–18 July), a striking feature of the systematic diurnal variation
in this area was elucidated. In these 3 days, the diurnal evolutions of convective activity were remarkably similar to each
other, implying that this pattern can be understood as a typical response of local cloud systems to the diurnal variation
of insolation under some summer monsoon situations. The ARG data show the difference in characteristics of rainfall between
pre- and mature monsoon seasons. The short intense downpour tends to occur more frequently in the pre-monsoon season than
in the mature monsoon season. The pre-monsoon rainfall also has clear diurnal variation with a peak that is more strongly
concentrated in time. In the northern part the rainfall peak is found in between midnight and early morning, while it is observed
in the daytime in central to western parts of the country. Two disaster cases caused by meso-scale disturbances are analyzed.
Although they occurred in the same season, the structures of the cloud systems were largely different from each other. The
disturbance brought about tornadoes on 14 April 2004, consisting of many spherical cloud systems of approximately 20 km size.
On the other hand, another one that caused the tragic river water transport accident on 23 May 2004 had meso-scale rain band
structure. The latter case was captured by the AWS located at Dhaka. Sudden changes in temperature, wind and pressure were
observed clearly, showing the typical structure of convective rain bands. 相似文献