全文获取类型
收费全文 | 783篇 |
免费 | 170篇 |
国内免费 | 319篇 |
专业分类
测绘学 | 7篇 |
大气科学 | 291篇 |
地球物理 | 183篇 |
地质学 | 514篇 |
海洋学 | 109篇 |
综合类 | 61篇 |
自然地理 | 107篇 |
出版年
2024年 | 10篇 |
2023年 | 25篇 |
2022年 | 35篇 |
2021年 | 34篇 |
2020年 | 43篇 |
2019年 | 48篇 |
2018年 | 37篇 |
2017年 | 54篇 |
2016年 | 44篇 |
2015年 | 52篇 |
2014年 | 60篇 |
2013年 | 65篇 |
2012年 | 65篇 |
2011年 | 70篇 |
2010年 | 42篇 |
2009年 | 58篇 |
2008年 | 54篇 |
2007年 | 59篇 |
2006年 | 45篇 |
2005年 | 48篇 |
2004年 | 45篇 |
2003年 | 31篇 |
2002年 | 31篇 |
2001年 | 38篇 |
2000年 | 28篇 |
1999年 | 27篇 |
1998年 | 27篇 |
1997年 | 17篇 |
1996年 | 14篇 |
1995年 | 9篇 |
1994年 | 14篇 |
1993年 | 18篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有1272条查询结果,搜索用时 0 毫秒
71.
本文以重庆市温塘峡背斜和滇东小江断裂带出露温泉为例,探讨了其水文地球化学特征的差异。研究发现,由于地质背景条件基本相同,温塘峡背斜出露的温泉水文地球化学特征比较接近,水化学类型为SO4-Ca(Mg)型,而小江断裂带温泉水文地球化学特征差异较大,泉水水化学类型主要有HCO3-Na型(YN1)、HCO3-Ca型(YN2)、SO4-Ca(Mg)型(YN3和YN5)和SO4-HCO3-Ca-Na型(YN4),这与各泉点所处地质背景条件不同有很大关系。此外,通过对Na-K-Mg和Na-K-Mg-Ca图解模型的解读得出,所有样品均未达到水-岩平衡,仅有YN1泉点样品接近完全平衡线,表明YN1接近水-岩作用平衡状态,并由上述图解模型估算得到YN1点热储温度大概为100~120℃,与运用SiO2温标计算的热储温度(133~139℃)相差不大。此外,水化学特征和Na-K-Mg-Ca图解分析也表明,YN2与温塘峡背斜温泉水-岩作用过程比较相似。 相似文献
72.
本文详细分析了山西辛安岩溶泉的水文地质条件,并通过对泉域岩溶水的补给、径流、排泄条件的分析,将辛安泉域概化为单输入单输出线性时不变集中参数随机系统的概念模型。利用24年的水文序列资料进行基流分割,获得泉多年月平均流量过程曲线,求得泉年平均流量和年平均补给量。在此基础上,应用滑动平均模型(MA),自回归—滑动平均模型(AR-MA)及泉流量调和分析—残差自回归等三个模型,对泉域地下水进行模拟,获得了满意的结果,不仅揭示了泉水动态特征,而且对泉流量动态进行了预报,为晋东南区域经济规划提供了有益资料。 相似文献
73.
本文首次弄清了毛垭温泉测点的局部地质环境,确定了测泉的水文地质性质和类型,弥补了建点基础资料之不足。采用常规的调查追踪方法对该前兆观测点近期出现的特大异常进行了较为详细地落实,并简要分析了调查结果。 相似文献
74.
75.
Phytoplankton growth rates and mortality rates were experimentally examined at 21 stations during the 2017 spring intermonsoon(April to early May) in the northern and central South China Sea(SCS) using the dilution technique, with emphasis on a comparison between the northern and central SCS areas which had different environmental factors. There had been higher temperature but lower nutrients and chlorophyll a concentrations in the central SCS than those in the northern SCS. The mean rates of phytoplankton growth(μ_0) and microzooplankton grazing(m) were(0.88±0.33) d~(–1) and(0.55±0.22) d~(–1) in the central SCS, and both higher than those in the northern SCS with the values of μ_0((0.81±0.16) d~(–1)) and m((0.30±0.09) d~(–1)), respectively.Phytoplankton growth and microzooplankton grazing rates were significantly coupled in both areas. The microzooplankton grazing impact(m/μ_0) on phytoplankton was also higher in the central SCS(0.63±0.12) than that in the northern SCS(0.37±0.06). The microzooplankton abundance was significantly correlated with temperature in the surface. Temperature might more effectively promote the microzooplankton grazing rate than phytoplankton growth rate, which might contribute to higher m and m/μ_0 in the central SCS. Compared with temperature, nutrients mainly affected the growth rate of phytoplankton. In the nutrient enrichment treatment,the phytoplankton growth rate(μn) was higher than μ_0 in the central SCS, suggesting phytoplankton growth in the central SCS was nutrient limited. The ratio of μ_0/μn was significantly correlated with nutrients concentrations in the both areas, indicating the limitation of nutrients was related to the concentrations of background nutrients in the study stations. 相似文献
76.
OGNJEN BONACCI 《水文科学杂志》2013,58(2):287-299
Abstract The method of “historic event” is used to generate synthetic hyetographs based on statistical analysis of precipitation data. A synthetic triangular model was developed based on rainfall data of Zioud watershed (central Tunisia) with a standard time step of one hour. A database of 2799 observed rainfall events was used to provide statistical parameters for a simple triangular-shaped hyetograph model. The developed model provides a synthetic hyetograph in dimensionless form for different storm durations (2, 3 and 4 hours). For a given season and location, the variation of the first dimensionless moment with duration was relatively small, with an average range of 13% for all the stations. The resulting dimensionless hyetographs were found to be nearly identical when they were non-dimensionalized using the rainfall depth and duration, showing some seasonal effect and insignificant effects of the rainfall duration. A good agreement between simulated and observed hyetographs was achieved based on not only visual impressions, but also statistical numerical and graphical tests. 相似文献
77.
《水文科学杂志》2013,58(4):682-699
Abstract The study area consists of the spring zones of the Kr?i?, Krka and Cetina river catchments located in the Dinaric karst, Croatia. Classical hydrological approaches and some newer time and frequency domain methods are used in order to validate the existing hypotheses both qualitatively and quantitatively, and these contribute to factual information about the hydrological behaviour of the catchments. The groundwater recharge rates are calculated by a mathematical model based on Palmer's soil-moisture balance method. The values of parameters of the groundwater recharge model are estimated by the spectral method. The calculated monthly and annual groundwater recharge rates form the basis for estimating the hydrological catchment areas of the spring zones and also for the determina-tion of quantitative relationships between the catchments. 相似文献
78.
Seismic tests have been conducted on two 3‐storey structures protected with pressurized fluid‐viscous spring damper devices. One of the structures was a reinforced concrete frame with clay elements in the slabs, while the other one was a steel frame with steel/concrete composite slabs. The spring dampers were installed through K bracing in between the floors. The tests were performed by means of the pseudodynamic method, which allowed the use of large and full‐size specimens, and by implementing a specific compensation strategy for the strain‐rate effect at the devices. The test results allowed the verification of the adequacy of the attachment system as well as the comparison of the behaviour of the unprotected buildings with several protected configurations, showing the benefits of the application of the devices and the characteristics of their performance. The response of the protected structures was always safer than that of the unprotected ones mainly due to a significant increase of equivalent damping. The increase in the damping ratio depends on the level of deformation. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
79.
在论述秦岭泥盆系层控铅锌矿床的黄铁矿微量元素,硫、铅、氢、氧同位素,矿物气液包裹体均一温度及成分.区域地层元素丰度等方面特征的基础上,提出了该类型属海底含矿热泉溢出沉积和隐伏含矿热泉贯入沉淀的成因模式. 相似文献
80.
我国春玉米水分供需状况分析 总被引:4,自引:1,他引:4
论述了作物需水量的概念及其计算方法,利用最新的气候和作物资料,计算了我国春玉米的作物需水量,分析其时空分布特征,并利用水发订正系来评价春玉米需水量的满足程度。计算分析结果表明,气候条件对我国在玉米生产是有利的,但在播种期、出苗期及拔节期(4-6月份),存在明显的水亏缺现象,这一时期应采取相应的栽培技术及节水灌溉、人工增雨等措施来缓解旱情。 相似文献