全文获取类型
收费全文 | 2395篇 |
免费 | 534篇 |
国内免费 | 763篇 |
专业分类
测绘学 | 167篇 |
大气科学 | 778篇 |
地球物理 | 654篇 |
地质学 | 1102篇 |
海洋学 | 330篇 |
天文学 | 131篇 |
综合类 | 282篇 |
自然地理 | 248篇 |
出版年
2024年 | 14篇 |
2023年 | 38篇 |
2022年 | 110篇 |
2021年 | 128篇 |
2020年 | 111篇 |
2019年 | 111篇 |
2018年 | 111篇 |
2017年 | 134篇 |
2016年 | 118篇 |
2015年 | 114篇 |
2014年 | 141篇 |
2013年 | 135篇 |
2012年 | 136篇 |
2011年 | 184篇 |
2010年 | 122篇 |
2009年 | 146篇 |
2008年 | 124篇 |
2007年 | 119篇 |
2006年 | 132篇 |
2005年 | 101篇 |
2004年 | 78篇 |
2003年 | 83篇 |
2002年 | 92篇 |
2001年 | 66篇 |
2000年 | 95篇 |
1999年 | 104篇 |
1998年 | 118篇 |
1997年 | 111篇 |
1996年 | 101篇 |
1995年 | 84篇 |
1994年 | 77篇 |
1993年 | 85篇 |
1992年 | 43篇 |
1991年 | 44篇 |
1990年 | 28篇 |
1989年 | 31篇 |
1988年 | 28篇 |
1987年 | 20篇 |
1986年 | 14篇 |
1985年 | 10篇 |
1984年 | 15篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1958年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有3692条查询结果,搜索用时 0 毫秒
121.
????GRACE?????????????????н???????????????139????????????????????????????仯??ο???????????ж?????????????????????????80%????????????????????????????????????λ???????С???????1 mm???????????????????????????????????????仯???????λ????????????С1.4??1.6 mm?? 相似文献
122.
ENSO事件对我国季节降水和温度的影响 总被引:82,自引:11,他引:82
对近40年来ENSO当年和次年我国季节降水和温度异常进行了合成分析和信度检验。结果表明,ENSO当年我国以少雨、低温为主,次年则相反。降水和温度异常季节变化也基本呈相反趋势。长江中下游地区显著降水异常并不发生在夏季,而在ENSO当年春、秋季和次年春季;东北地区最显著的低温也不在夏季,而在ENSO当年秋季至次年春季。根据本文结果对目前ENSO影响研究中的有关问题提出了看法。 相似文献
123.
Model for Methane Emission from Rice Fields and Its Application in Southern ChinaDingAijuandWangMingxing(InstituteofAtmospher... 相似文献
124.
125.
热带西太平洋海洋上层热含量的分布特征及其年际变化的分析 总被引:1,自引:0,他引:1
选用海面至20℃等温线所处深度水层的平均温度来表征研究海域海洋上层热含量。利用这一特征值,分析1986—1990年期间热带西太平洋边缘海域海洋上层热含量在秋季的分布特征和年际变化。结果表明:(1)热含量呈南高北低分布,在7.5-22.1°N范围内。以130°E断面为代表,热含量的平均递减率为0.179(℃/纬度);(2)热含量的分布主要取决于环流系统,其等值线因受黑潮和棉兰老海流的影响而由纬向分布转向经向分布。某些区域因受暖涡及冷涡的影响而呈封闭状分布;(3)热含量的年际变化与E1Nino事件存在着很好的相关性,在E1Nino事件发生期间,热含量变得很低,高热含量(大于26.5℃)海区的分布范围明显缩小。 相似文献
126.
127.
In consideration of the rapid degradation of coral reef ecosystems, the establishment of models is helpful to comprehend the degradation mechanism of coral reef ecosystems and predict the development process of coral reef communities. According to the characteristics of complex ecosystem of tropical coral reefs in China, the coral reef functional group is the core level variable; combined with the multiple feedback effects of coral reef functional groups and environmental changes, the study presents a coral reef ecosystem dynamics model with hermatypic corals as the core. Based on the simulation of the assumed initial value and the internal feedback of the system, the results show that in the basic simulation(relative health conditions), the coverage area of live corals and coral reefs generally decreased first and then increased, and increased by 4.67% and 6.38% between2010 and 2050, respectively. Based on the calibration model and the current situation of the studied area, the multi-factor disturbance effects of coral reef communities were simulated and explored by setting up three scenarios involving fishing policy, terrestrial deposition, and inorganic nitrogen emissions. Among them, in the single factor disturbance, the fishing policy exerts the most direct impact on the community decline; and the succession phenomenon is obvious; the terrestrial sedimentation has a faster and more integrated effect on the community decline; the effect of inorganic nitrogen emission on the community decline is relatively slow. In the double/multi-factor disturbance, the superimposed disturbance will aggravate the multi-source feedback effect of the coral reef communities development, accelerate the community decay rate, and make its development trajectory more complicated and diverse. This method provides a scientific and feasible method for simulating the damage of long-term coral reef community and exploring the development law and adaptive management of coral reef ecosystems. In the future, it can be further studied in the ecological restoration process and decisionmaking direction of coral reefs. 相似文献
128.
129.
Ship floating condition in regular waves is calculated. New equations controlling any ship's floating condition are proposed by use of the vector operation. This form is a nonlinear optimization problem which can be solved using the penalty function method with constant coefficients. And the solving process is accelerated by dichotomy. During the solving process, the ship's displacement and buoyant centre have been calculated by the integration of the ship surface according to the waterline. The ship surface is described using an accumulative chord length theory in order to determine the displacement, the buoyancy center and the waterline. The draught forming the waterline at each station can be found out by calculating the intersection of the ship surface and the wave surface. The results of an example indicate that this method is exact and efficient. It can calculate the ship floating condition in regular waves as well as simplify the calculation and improve the computational efficiency and the precision of results. 相似文献
130.