全文获取类型
收费全文 | 3931篇 |
免费 | 468篇 |
国内免费 | 657篇 |
专业分类
测绘学 | 1488篇 |
大气科学 | 689篇 |
地球物理 | 625篇 |
地质学 | 879篇 |
海洋学 | 615篇 |
天文学 | 104篇 |
综合类 | 411篇 |
自然地理 | 245篇 |
出版年
2024年 | 15篇 |
2023年 | 48篇 |
2022年 | 77篇 |
2021年 | 117篇 |
2020年 | 121篇 |
2019年 | 159篇 |
2018年 | 98篇 |
2017年 | 153篇 |
2016年 | 227篇 |
2015年 | 197篇 |
2014年 | 233篇 |
2013年 | 309篇 |
2012年 | 256篇 |
2011年 | 277篇 |
2010年 | 204篇 |
2009年 | 246篇 |
2008年 | 228篇 |
2007年 | 253篇 |
2006年 | 260篇 |
2005年 | 204篇 |
2004年 | 172篇 |
2003年 | 147篇 |
2002年 | 131篇 |
2001年 | 113篇 |
2000年 | 85篇 |
1999年 | 94篇 |
1998年 | 126篇 |
1997年 | 86篇 |
1996年 | 72篇 |
1995年 | 63篇 |
1994年 | 55篇 |
1993年 | 45篇 |
1992年 | 40篇 |
1991年 | 24篇 |
1990年 | 24篇 |
1989年 | 31篇 |
1988年 | 18篇 |
1987年 | 21篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有5056条查询结果,搜索用时 15 毫秒
91.
Keith D. Hamill 《新西兰海洋与淡水研究杂志》2013,47(5):1057-1059
Toxic cyanobacteria have been linked to dog deaths in the Waikanae River (1998) and Mataura River (1999 and 2000), New Zealand. These were Oscillatoria‐like species which formed benthic mats. This is the first time in New Zealand that animal deaths have been linked to toxins from benthic cyanobacteria. 相似文献
92.
93.
94.
Fry of grass carp, Ctenopharyngodon idella (Val.), were air‐freighted from Hong Kong to New Zealand in October 1971. The fish were at first kept in tanks with a recirculating water supply, where they soon showed symptoms of parasitic infestation and suffered heavy mortality. Attempts were made to remove parasites with chemotherapeutic treatment. Tripartiella sp., Dactylogyrus ctenopharyngodonis, and Gyrodactylus clenopharyngodontis were eliminated by prolonged bathing of the infected fish with quinine. Chemical treatment failed to eliminate Ichthyophthirius mullifiliis from the body surface and the gills, but the rate of spontaneous recovery of the fish from this disease was accelerated by keeping them in clean, running water. Experiments to remove the cestode Bothriocephalus gowkongensis from the intestine of the fish with tetravalent tin compounds and to control the intermediate host (Cyclops) in the water resulted in the eradiction of the cestode. When parasitic infestations had been brought under control the fish were transferred to outdoor ponds, where they began to feed on aquatic and terrestrial vegetation and rapidly increased in size. 相似文献
95.
Lionel Carter 《新西兰海洋与淡水研究杂志》2013,47(2):263-282
Transport of seston (suspended sediment) in Pelorus Sound is controlled by tides and freshwater inflow. During high freshwater inflow, a moderately stratified estuarine circulation may be superimposed on the tidal circulation, but the latter dominates and transports seston seawards and landwards with the ebb and flood phases respectively. With extreme freshwater inflow, the estuarine circulation gains impetus and most seston is rapidly transported seaward in the low saline surface layer. Irrespective of circulation there is a persistent trend in seston concentrations. Highest values occur at the sound's head because of the influence of nearby Pelorus and Kaituna Rivers and because of resuspension of bottom sediment by strong tidal currents. Seston concentrations wane along the sound until near the entrance, where values increase as a result of greater production of biogenic seston and because additional seston is brought in from Cook Strait with the flood tide. This trend parallels variability in the thicknesses of muddy bottom sediments. Muds are thick at the head where an extensive delta extends from the river mouths; muds gradually thin seaward and then thicken markedly in the vicinity of the sound entrance. Seston weight and composition patterns and 3.5 kHz seismic profiles indicate Pelorus Sound acts as a double‐ended sediment trap. The upper reaches receive and retain river‐derived seston, whereas the sound entrance traps seston derived from Cook Strait. This situation appears to hold for both high and extremely high influxes of sediment. 相似文献
96.
根据2011年6月茅尾海生态环境调查资料,对该海域海水和表层沉积物中叶绿素a的空间分布进行了分析。结果表明,海水叶绿素a变化范围1.384~4.060 mg/m3,平均值为2.143 mg/m3,表层沉积物叶绿素a范围为0.006~0.740 mg/kg(湿重),均值为0.124 mg/kg;海水与表层沉积物叶绿素a均呈现自河口向南逐渐降低的空间分布特征。单位面积表层沉积物叶绿素a平均含量为上方水柱叶绿素a平均含量的129.44%,沉积物对该海域初级生产力有显著的潜在贡献。相关分析表明,海水和沉积物叶绿素a均与无机氮及底栖动物栖息密度呈显著或极显著的正相关关系(P0.05或P0.01)。 相似文献
97.
98.
在对珠江口外2006年冬季航次走航ADCP观测资料处理中发现用Joyce的方法不能有效地订正系统误差,其原因在于订正角与航速、船艏向相关。给出了一个订正角为船艏向余弦的拟合函数,得出良好的订正结果。分析了VmDas软件处理流速结果的精度,给出了系统误差识别的方法。发现观测资料中一些不能为VmDas软件识别的错误数据,分析了海况对观测资料的影响,提出了观测资料质量控制与误差订正的一套程序。 相似文献
99.
We present an alternative scheme for implementing the unconventional geometric two-qubit phase gate and preparing multiqubit entanglement by using a frequency-modulated laser field to simultaneously illuminate all ions. Selecting the index of modulation yields selective mechanisms for coupling and decoupling between the internal and the external states of the ions. By the selective mechanisms, we obtain the unconventional geometric two-qubit phase gate, multiparticle Greenberger--Horne--Zeilinger states and highly entangled cluster states. Our scheme is insensitive to the thermal motion of the ions. 相似文献
100.