全文获取类型
收费全文 | 18911篇 |
免费 | 4232篇 |
国内免费 | 6324篇 |
专业分类
测绘学 | 2791篇 |
大气科学 | 3535篇 |
地球物理 | 3685篇 |
地质学 | 10523篇 |
海洋学 | 4083篇 |
天文学 | 466篇 |
综合类 | 1743篇 |
自然地理 | 2641篇 |
出版年
2024年 | 155篇 |
2023年 | 382篇 |
2022年 | 1063篇 |
2021年 | 1268篇 |
2020年 | 1071篇 |
2019年 | 1288篇 |
2018年 | 1140篇 |
2017年 | 1114篇 |
2016年 | 1154篇 |
2015年 | 1200篇 |
2014年 | 1304篇 |
2013年 | 1537篇 |
2012年 | 1611篇 |
2011年 | 1651篇 |
2010年 | 1573篇 |
2009年 | 1534篇 |
2008年 | 1573篇 |
2007年 | 1469篇 |
2006年 | 1326篇 |
2005年 | 1051篇 |
2004年 | 789篇 |
2003年 | 651篇 |
2002年 | 662篇 |
2001年 | 618篇 |
2000年 | 463篇 |
1999年 | 359篇 |
1998年 | 238篇 |
1997年 | 208篇 |
1996年 | 192篇 |
1995年 | 163篇 |
1994年 | 121篇 |
1993年 | 112篇 |
1992年 | 87篇 |
1991年 | 55篇 |
1990年 | 45篇 |
1989年 | 46篇 |
1988年 | 32篇 |
1987年 | 21篇 |
1986年 | 26篇 |
1985年 | 20篇 |
1984年 | 15篇 |
1983年 | 12篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1979年 | 10篇 |
1978年 | 6篇 |
1958年 | 4篇 |
1957年 | 5篇 |
1954年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
In 1979, we found many small colorless transparent and light yellow-green glassy spherules in the surface layer and core sediment samples taken from the west of the Central Pacific Occan, which are considered to be microtektites. This finding is worthy of further determination of the range of strewn field and origin of tektites. 相似文献
92.
CHEN Yan KE Caihuan ZHOU Shiqiang LI FuxueDepartment of Oceanography Key Laboratory for Marine Environmental Science of the Ministry of Education Xiamen University Xiamen China 《海洋学报(英文版)》2004,(3)
The development of embryos and larvae of Babylonia formosae habei living along the southeast coast of China is observed under laboratory conditions. The egg masses are laid by females on hard substrate at night and each capsule contains 100-500 eggs. Each egg is 250-280 mm in diameter. The first two cleavages of the embryo are meridional and equal, and a polar lobe is produced. Larval kidney, which only consists of a single cell, appears during the gastrula stage on each side of the embryo. The right tentacle develops prior to the left one. At 25-27℃, an intracapsulate veliger stage is reached about 4.5 d after deposition. The larvae hatch on the fifth day as swimming veligers with a shell length of 360 -500 mm. The newly hatched larva can ingest suspended algal cells from the water column and remains in the pelagic stage for 8-10 d. The newly settled juveniles are 900-1 200 mm in shell length. 相似文献
93.
Following Bagnold's approach, a relationship between sediment transport and energy dissipation is developed. The major assumption made in the study is that the near bed velocity plays a dominant role in the process of sediment transport. A general relationship between energy dissipation and sediment transport is first proposed. Then the equations for total sediment transport are derived by introducing the appropriate expression of energy dissipation rate under different conditions, such as open channel flows, combination of wave and current, as well as longshore sediment transport. Within the flows investigated, the derived relationships are fairly consistent with the available data over a wide range of conditions. 相似文献
94.
半潜式超大浮体连接器动力特性的一种时间序列分析方法 总被引:1,自引:2,他引:1
根据刚性模块弹性连接器 (RMFC)假设研究由 3个模块连接而成的半潜式超大浮体MobileOffshoreBase(MOB)的波浪载荷动力响应。模块和连接器动力响应根据时间序列法计算 ,这种方法包括海况模拟 ,波浪载荷计算和结构响应计算三个主要部分。通过对结构的适当简化 ,根据Airy波理论 ,Morrison公式以及流体中的结构运动方程、弹性连接器变形方程 ,计算求得MOB在不规则海况下的动力响应 ,并将其与相关文献中的结果进行比较 ,表明该方法有良好的精确性 相似文献
95.
96.
97.
98.
提出了混合型单调算子对的概念,并给出了其不动点的存在唯一性;研究了它在微分方程组的具体应用. 相似文献
99.
The development of embryos and larvae of Babyloniaformosae habei living along the southeast coast of China is observed under laboratory conditions. The egg masses are laid by females on hard substrate at night and each capsule contains 100-500 eggs. Each egg is 250-280 mm in diameter. The fast two cleavages of the embryo are meridional and equal, and a polar lobe is produced. Larval kidney, which only consists of a single cell, appears during the gastrula stage on each side of the embryo. The right tentacle develops prior to the left one. At 25-27 ℃, an intracapsulate veliger stage is reached about 4.5 d after deposition. The larvae hatch on the fifth day as swimming veligers with a shell length of 360 -500 mm. The newly hatched larva can ingest suspended algal cells from the water column and remains in the pelagic stage for 8-10 d. The newly settled juveniles are 900-1 200 mm in shell length. 相似文献
100.
1 .Introduction Wave breaking and associated whitecapping have long beeninteresting due totheir close relationto many fields of ocean study,including air-sea interaction,remote sensing,ocean engineering,aswell as wave dynamics .The breaking probabilityBan… 相似文献