全文获取类型
收费全文 | 1598篇 |
免费 | 231篇 |
国内免费 | 315篇 |
专业分类
测绘学 | 8篇 |
大气科学 | 487篇 |
地球物理 | 442篇 |
地质学 | 724篇 |
海洋学 | 236篇 |
天文学 | 90篇 |
综合类 | 35篇 |
自然地理 | 122篇 |
出版年
2024年 | 6篇 |
2023年 | 24篇 |
2022年 | 29篇 |
2021年 | 46篇 |
2020年 | 60篇 |
2019年 | 42篇 |
2018年 | 35篇 |
2017年 | 51篇 |
2016年 | 41篇 |
2015年 | 48篇 |
2014年 | 58篇 |
2013年 | 70篇 |
2012年 | 54篇 |
2011年 | 81篇 |
2010年 | 64篇 |
2009年 | 112篇 |
2008年 | 118篇 |
2007年 | 105篇 |
2006年 | 113篇 |
2005年 | 107篇 |
2004年 | 104篇 |
2003年 | 72篇 |
2002年 | 75篇 |
2001年 | 53篇 |
2000年 | 84篇 |
1999年 | 71篇 |
1998年 | 61篇 |
1997年 | 58篇 |
1996年 | 44篇 |
1995年 | 31篇 |
1994年 | 42篇 |
1993年 | 36篇 |
1992年 | 25篇 |
1991年 | 14篇 |
1990年 | 28篇 |
1989年 | 12篇 |
1988年 | 14篇 |
1987年 | 13篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 5篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有2144条查询结果,搜索用时 15 毫秒
101.
W. Swider 《Pure and Applied Geophysics》1988,127(2-3):403-414
The most meaningful way to compare observations of the daytimeD-region under all ionization conditions, for the purpose of improving our understanding of this region, would appear to be through use of the effective electron recombination coefficient, =q/[e]2, whereq is the ionization production rate, and where [e] is the electron concentration. This ratio apparently increases monotonically with decreasing altitude, and is much less variable than its componentsq and [e]. This parameter appears eminently suitable as a best first order solution to [e] after determiningq. For nighttime conditions, is more sensitive toq. However, an accurate but simple formula exists for the calculation of electron concentrations. 相似文献
102.
103.
黄山东镁铁超镁铁杂岩中的辉石化学成分研究 总被引:7,自引:0,他引:7
通过对黄山东镁铁超镁铁杂岩的辉石化学成分研究,证明辉石的化学成分受寄主岩石类型的制约,从超镁铁岩相到角闪辉长岩相斜方辉石的化学成分由富MgO、SiO_2、Al_2O_3、Cr_2O_3到富FeO、TiO_2、CaO、MnO;单斜辉石化学成分由富Al_2O_3、Cr_2O_3、Na_2O、MgO到富FeO、MnO、CoO。在同一寄主岩石中,单斜辉石比斜方辉石富TiO_2、Al_2O_3、Cr_2O_3、CaO和Na_2O,贫MgO、SiO_2、MnO和FeO。根据辉石化学成分特征得出黄山东杂岩形成于岛弧环境,为上地幔石榴二辉檄榄岩部分熔融形成的拉斑玄武岩岩浆结晶分异作用的产物。 相似文献
104.
金川超镁铁质岩体矿物化学特征及矿物地质温度计、压力计研究 总被引:4,自引:0,他引:4
根据金川超镁铁质岩体主要造岩矿物和副矿物的共生组合关系及各种矿物的化学成分特点;选用5种较成熟、使用较方便的矿物地质温度计、压力计(主要是辉石温压计和角闪石压力计),对岩体形成的温、压条件进行了估算,其结果为:成岩温度为1000~1300℃(上限可到1400~1500℃),成岩压力约为5×10 ̄8~11×10 ̄8pa。金川超镁铁质岩体的主要岩石类型为尖晶石二辉橄榄岩,这一岩石类型在复杂体系相关系图中的稳定区域大致处于5×l0 ̄8~15×10 ̄8pa的范围,这与矿物温压计估算的成岩温压条件是一致的。 相似文献
105.
The chemical composition of lake water in Laguna Amarga, a small, shallow, saline lake near the Torres del Paine National Park (at 51°S), Chilean Patagonia, was studied in January, 1993. The water was strongly alkaline (pH 9.4) conductivity was 71.4 mS cm–1, and salinity was 77 g L–1. The major ions were sodium and sulphate. 相似文献
106.
Influence of fluid chemistry on shear-wave attenuation and velocity in sedimentary rocks 总被引:2,自引:0,他引:2
Dung Vo-Thanh 《Geophysical Journal International》1995,121(3):737-749
107.
With the high-speed development of numerical weather prediction, since the later 1980’s, the prediction of short-range climate anomalies has attracted worldwide meteorologists’ attention. What the so called short-range re-fers to the time scale from one month to one season or more. In dealing with the problem of short-range climate pre-diction, two points are needed noticing: one is the basic research to explore or investigate the mechanism of variability of the slow varying components which mainly include internal dynamics of extratropics, external forcings and tropical dynamics, and the other is the modeling efforts to simulate the process of the long-term evolution of the signal which include the improvement of model quality, stochastic prediction and the air-sea-coupled model (Miyakoda et al.,1986). Previous researches on the numerical prediction of short-term climate anomalies are mostly concentrated in the analysis of variables with global spatial scale, especially the global general atmospheric circulation analysis.As to the simulation or prediction of regional short-term climate anomalies, there exist many difficulties and problems. Though some meteorologists are devoting themself to this field, up to now, they have not reached satisfac-tory results. As a primary effort, by using the 2-level general atmospheric circulation model developed in the Institute of Atmospheric Physics, Chinese Academy of Sciences (IAP-AGCM) (Zeng et al., 1989), and taking the year of 1985 as a case, a numerical simulation of regional short-term climate change is completed. We pay high attention to the predictand of anomalous summer rainfall in the Yangtze River and Yellow River valleys, especially its month-to-month variation. 相似文献
108.
本文用279个气象测站的年雨量资料得到中国东部(100°E以东)1891—1988年大范围平均雨量资料序列.对代表性进行了检验表明:序列在1921年以后能较好地反映大范围气候旱涝状况,而1920年以前则代表性较差.从雨量变化看中国东部的气候在近百年期间是干湿交替出现的,可以分成六个时段.在近四五十年中雨量有减少的趋势,前期雨量偏多,后期从60年代中期以来雨量持续偏少.而且这种变化与北半球副热带其他地区有同相变化的关系.在50年代以前副热带地区雨量的变化却没有明显的同相关系. 相似文献
109.
Laminar sheetflows, transporting sediment at their capacity rates, both with and without rainfall disturbance, were investigated. Values of flow depth and relative submergence were very small. In the flows without rainfall, measured velocities exceeded the predictions of the smooth-surface, clear-water laminar model by an average of 12 per cent. Reduced flow resistance due to high sediment concentrations may explain this result. Velocities in the rainfall-disturbed flows were not significantly different from the predictions of the smooth-surface, clear-water model, and the velocity reduction due to rainfall was about 12 per cent. Although the uniformity of rainfall intensity under the single-nozzle rainfall simulator is high, variation of momentum and kinetic energy fluxes along the 1-5 m long flume was significant. The rainfall angle of incidence was highly correlated with deviations from expected flow velocities in the upper and lower sections of the flume. 相似文献
110.