全文获取类型
收费全文 | 96篇 |
免费 | 11篇 |
国内免费 | 25篇 |
专业分类
大气科学 | 1篇 |
地球物理 | 15篇 |
地质学 | 30篇 |
海洋学 | 68篇 |
天文学 | 3篇 |
综合类 | 10篇 |
自然地理 | 5篇 |
出版年
2022年 | 4篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2014年 | 6篇 |
2013年 | 15篇 |
2012年 | 3篇 |
2011年 | 6篇 |
2010年 | 3篇 |
2009年 | 9篇 |
2008年 | 5篇 |
2007年 | 7篇 |
2006年 | 7篇 |
2005年 | 7篇 |
2004年 | 1篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 6篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有132条查询结果,搜索用时 15 毫秒
31.
32.
在广东大亚湾核电站温排水排放前、后,自1993年1月20日至1995年2月28日对该站附近水域14个站位共进行6个航次的采样调查,收集鲷科鱼卵、仔鱼样本和同一站位的水温资料。结果表明,各站位的绸科鱼卵、仔鱼的分布在温排水排放前、后与水温变化密切相关。水域升温2—8℃对鲷科鱼类的产卵、孵化和仔鱼生长发育有明显的影响。鉴于目前升温水域范围只限在2nmile内,可以认为整个大亚湾鲷科鱼类的资源和补充尚未受到较大的影响。 相似文献
33.
Hans-Uwe Dahms Xiangdong Li Gan Zhang Pei-Yuan Qian 《Estuarine, Coastal and Shelf Science》2006,67(4):562-568
The distribution and abundance of viable and non-viable (so-called resting eggs) embryos of the calanoid copepod Tortanus forcipatus were determined in the laboratory by the enumeration of nauplii that emerge from sediments collected in Victoria Harbor (Hong Kong). Sediment cores sliced down to a depth of 37 cm showed the highest number of viable resting eggs near the surface layer (0–5 cm). The number of viable eggs sharply decreased with sediment depth, particularly at the inner harbor stations, although diapause eggs remained viable as deep as 25 cm. 210Pb analyses of the sediments indicated that the mean egg age was 4.9 years. The egg mortality of T. forcipatus in the sediments was 0.135 year−1, or 78.22% annual egg survival, calculated by regressing ln (egg density) from sediment age. The range of horizontal distribution of viable resting eggs was 24.25 × 103–58.90 × 103 m−2, with a mean value of 36.8 × 103 m−2 over all stations. The accumulation of viable resting eggs that can persist for an extended period of time provided evidence for the existence of an egg bank of T. forcipatus in the sediments of Victoria Harbor. 相似文献
34.
T. M. Ward J. Staunton-Smith S. Hoyle I. A. Halliday 《Estuarine, Coastal and Shelf Science》2003,56(5-6):1125-1140
The diverse pelagic fish assemblage of sub-tropical southern Queensland includes fishes with predominantly temperate distributions, such as tailor Pomatomus saltatrix, sardine Sardinops sagax, round herring Etrumeus teres, and Australian anchovy Engraulis australis. The peak spawning seasons of P. saltatrix, S. sagax and E. teres occur during late winter and early spring (June–October). Eggs and larvae of these three species are widely distributed in shelf waters and comprise >50% of the ichthyoplankton assemblage during this period. Mean monthly sea surface temperatures (SSTs) during late winter and early spring range from 21 to 23 °C, and are thus similar to those recorded in southern Australia during summer and autumn, which is the spawning season of these three species in those temperate waters. E. australis eggs occur mainly in inshore waters, and comprise >50% of fish eggs collected during summer and autumn when mean monthly SSTs in southern Queensland exceed 27 °C. E. australis also spawns mainly during summer and autumn in temperate Australia. Hence, water temperature may be less important as a determinant of the spawning season of E. australis than it is for the other three species. The suitability of southern Queensland for spawning by predominantly temperate species during late winter and early spring may contribute to the high diversity of the region's pelagic fish assemblage. Adult P. saltatrix, S. sagax and E. teres appear to migrate northwards into southern Queensland during early winter to spawn, and larvae may be transported southwards into temperate waters by the East Australian Current. This dispersal-migration pattern is similar to those observed for several species, including P. saltatrix, in the western boundary current systems off the east coasts of North America and Africa. Hence, pelagic fishes in ecosystems off the east coast of three continents migrate into sub-tropical waters to spawn, and larvae are transported back into temperate nursery areas by the prevailing current. 相似文献
35.
圆尾斗鱼的胚胎和仔鱼发育的研究 总被引:7,自引:0,他引:7
圆尾斗鱼的受精卵呈圆球形,光滑,略带淡黄色,浮性;卵膜吸水膨胀后的平均直径为1.19mm,当水温21-23.5℃时,从受精卵到孵化出膜需42.5小时;水温22-24.5℃时,刚出膜仔鱼到卵黄囊消失需4天,到油球消失约25天。出膜30天仔鱼的形态基本与成体相似。 相似文献
36.
37.
华东地区虽然迄今没有发现可靠的暴龙类恐龙骨骼化石,但近年在浙江天台白垩纪赤城山组地层中发现了白垩纪巨型暴龙类恐龙产的西峡巨型长形蛋(Macroelongatoolithus xixiaensis)化石。因暴龙类恐龙目前在系统分类上被归入兽足亚目(Theropoda)暴龙超科(Tyrannosauroidea)暴龙科(Tyrannosauridae),建议巨型长形蛋化石也可采用相应分类方法,归入长形蛋化石亚目(Elongatoolithineae)巨型长形蛋化石超科(Macroelongatoolithoidea)巨型长形蛋化石科(Macroelongatoolithidae),以便对应研究。这些蛋究竟是哪一种暴龙类恐龙所产?从目前掌握资料分析,在东亚的暴龙类恐龙属种中,冠龙和帝龙个体较小,成年体长分别仅约3m和1.6m,年代更早,分别为约160Ma和130Ma,基本上可以排除在外。鹰龙和分支龙成年体长5m~6m,还不能算巨型暴龙类恐龙。只有体长达10m,甚至更大的特暴龙,似乎最有可能产下这样的巨型长形蛋。但特暴龙迄今已知的化石层位时代为晚白垩世末期的Maastrichtian期(71Ma~65Ma),而浙江的巨型长形蛋的年代则是晚白垩世早期的Turonian期(约92Ma)。这样就存在两种可能,或许是特暴龙的生存年代要上溯到约92Ma,或许这种巨型长形蛋是另一种目前尚不为人知的,生存年代在约92Ma的巨型暴龙类恐龙所产。此外,根据这些蛋化石的外形特征及其在巢穴里的分布方式可以推测,这种暴龙类恐龙,具有功能双输卵管系统,每次产卵2枚,蛋在巢穴里呈2个一组放射状排列。其蛋壳并非刚性的硬壳,而是具有一定韧性的厚牛皮纸状外壳,在重力作用下变形呈扁的长椭球形。 相似文献
38.
39.
40.
T. P. Singh 《Journal of Astrophysics and Astronomy》1997,18(4):335-338
We give an elementary overview of the subject of gravitational collapse in classical general relativity. Recent theoretical
evidence for the formation of black-holes and naked singularities is summarised. 相似文献