全文获取类型
收费全文 | 2395篇 |
免费 | 486篇 |
国内免费 | 429篇 |
专业分类
测绘学 | 235篇 |
大气科学 | 352篇 |
地球物理 | 715篇 |
地质学 | 1019篇 |
海洋学 | 492篇 |
天文学 | 33篇 |
综合类 | 150篇 |
自然地理 | 314篇 |
出版年
2024年 | 6篇 |
2023年 | 39篇 |
2022年 | 106篇 |
2021年 | 118篇 |
2020年 | 132篇 |
2019年 | 113篇 |
2018年 | 98篇 |
2017年 | 124篇 |
2016年 | 116篇 |
2015年 | 117篇 |
2014年 | 152篇 |
2013年 | 166篇 |
2012年 | 184篇 |
2011年 | 146篇 |
2010年 | 131篇 |
2009年 | 135篇 |
2008年 | 146篇 |
2007年 | 150篇 |
2006年 | 153篇 |
2005年 | 140篇 |
2004年 | 102篇 |
2003年 | 90篇 |
2002年 | 74篇 |
2001年 | 85篇 |
2000年 | 77篇 |
1999年 | 64篇 |
1998年 | 51篇 |
1997年 | 50篇 |
1996年 | 45篇 |
1995年 | 31篇 |
1994年 | 38篇 |
1993年 | 39篇 |
1992年 | 13篇 |
1991年 | 23篇 |
1990年 | 9篇 |
1989年 | 6篇 |
1988年 | 10篇 |
1987年 | 9篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 1篇 |
1983年 | 5篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1978年 | 3篇 |
1976年 | 2篇 |
排序方式: 共有3310条查询结果,搜索用时 15 毫秒
81.
82.
Deep sea drilling in the Central Gulf of California, a young and active spreading centre, shows that the high heat flow typical of these regions causes extensive alteration of sediment organic matter, especially near sills and above magma chambers where hydrothermal activity is concentrated. Even on the nearby passive margin, where there are no sills, heat flow is moderately high and hydrocarbon generation has begun in immature sequences. Migrating light hydrocarbons are detected especially where hydrothermal activity is concentrated. Thermogenic methane is more widespread, though not in the passive margin bordering the spreading centre. Despite the incidence of hydrocarbon generation and migration, the amounts of hydrocarbons involved are relatively small and apparently do not lead to commercially significant accumulations of petroleum.The organic matter in these sediments is mostly marine because the Gulf of California generally has low runoff from land and highly productive surface waters. Turbidites rich in terrigenous organic material are locally abundant in the mainly pelagic section in the Guaymas Basin. The highest concentrations of organic matter are found in laminated diatomites deposited on the Guaymas passive margin within the oxygen minimum zone. 相似文献
83.
84.
钱塘江河口的风暴潮预报工作可归结为澉浦或乍浦两个单站的预报,这使得经验预报成为可能。利用一种动力线性模型将动力学的线性问题转化为统计学的线性回归模型,通过合理选取预报量及预报因子,并采用正交筛选技术确定每个预报因子所对应的系数,建立经验预报方程。后报结果表明该方法可取得较好的效果。 相似文献
85.
86.
87.
This paper presents a numerical model study of the propagation of water waves using the parabolic approximation of the mild-slope equation in the orthogonal coordinate system. Two types of coordinate systems are studied: (a) a general form of orthogonal coordinate system and (b) the conformal system, a special form of orthogonal coordinate system. Two typical examples, namely, expanded breakwaters and a circular channel, are studied to validate the model. First, the examples are studied by use of the general orthogonal coordinates. Then the same examples are computed by use of the confonnal system. The computational results show that the confonnal coordinate system generally gives better predictions than the general orthogonal system. A numerical technique for generating the conformal grid is combined with the numerical model to improve the practicability of the model. The comparison between the result from the numerical grid system and that from the analytical grid system shows that reliable computational results can be obtained by use of the numerical confonnal grid system. 相似文献
88.
The upper layer (above 140 m depth) temperature in the western Philippine Sea near Taiwan was sampled using a coastal monitoring
buoy (CMB) with 15 attached thermistors during July 28–August 7, 2005. The data were collected every 10 min at 1, 3, 5, 10,
15, and 20 m using the CMB sensors, and every 15 sec at 15 different depths between 25 m and 140 m. Internal waves and solitons
were identified from the time-depth plot of the temperature field. Without the internal waves and solitons, the power spectra,
structure functions, and singular measures (representing the intermittency) of temperature field satisfy the power law with
multi-scale characteristics at all depths. The internal waves do not change the basic characteristics of the multifractal
structure. However, the internal solitons change the power exponent of the power spectra drastically, especially in the low
wave number domain; they also break down the power law of the structure function and increase the intermittency parameter.
The physical mechanisms causing these different effects need to be explored further. 相似文献
89.
90.
风力对内陆浅水水域磷水平的影响 总被引:1,自引:0,他引:1
本文通过对平度市大泽山水库(面积约0.5平方公里,平均水深约1.5米)的实地观测,研究了风力对内陆浅水水域磷水平的影响。结果表明,影响程度取决于风速、风力作用时间、水深以及风力作用前磷水平的高低等因素。就大泽山水库而言,风速大于2.5米/秒的风力可引起各种形态磷的明显增加。不过对磷酸盐磷来说,如果浓度本来就较高,风力作用下当有大量沉积物颗粒泛起时,会对PO_4~≡产生吸附,因而可能导致水中游离磷酸盐磷含量下降。鉴于此,作者建议对内陆浅水水域进行磷水平调查时应考虑风力的作用。 相似文献