全文获取类型
收费全文 | 38002篇 |
免费 | 7451篇 |
国内免费 | 8541篇 |
专业分类
测绘学 | 2847篇 |
大气科学 | 7230篇 |
地球物理 | 10480篇 |
地质学 | 18295篇 |
海洋学 | 4500篇 |
天文学 | 1931篇 |
综合类 | 3864篇 |
自然地理 | 4847篇 |
出版年
2024年 | 103篇 |
2023年 | 460篇 |
2022年 | 1511篇 |
2021年 | 1713篇 |
2020年 | 1429篇 |
2019年 | 1891篇 |
2018年 | 2075篇 |
2017年 | 2001篇 |
2016年 | 2306篇 |
2015年 | 2082篇 |
2014年 | 2445篇 |
2013年 | 2447篇 |
2012年 | 2297篇 |
2011年 | 2357篇 |
2010年 | 2453篇 |
2009年 | 2272篇 |
2008年 | 2168篇 |
2007年 | 1998篇 |
2006年 | 1549篇 |
2005年 | 1507篇 |
2004年 | 1132篇 |
2003年 | 1182篇 |
2002年 | 1183篇 |
2001年 | 1186篇 |
2000年 | 1299篇 |
1999年 | 1628篇 |
1998年 | 1294篇 |
1997年 | 1230篇 |
1996年 | 1131篇 |
1995年 | 980篇 |
1994年 | 857篇 |
1993年 | 784篇 |
1992年 | 626篇 |
1991年 | 497篇 |
1990年 | 367篇 |
1989年 | 345篇 |
1988年 | 298篇 |
1987年 | 164篇 |
1986年 | 163篇 |
1985年 | 105篇 |
1984年 | 108篇 |
1983年 | 81篇 |
1982年 | 79篇 |
1981年 | 61篇 |
1980年 | 38篇 |
1979年 | 35篇 |
1978年 | 11篇 |
1977年 | 11篇 |
1976年 | 6篇 |
1958年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
CORROSION AND ADHERENCE AT SEA OIL-PLATFORM 总被引:1,自引:0,他引:1
Measurements of the adhesive corrosion and protective potentials of 3 Bohai Sea oilplatforms under different cathodic protection showed corrosion still occurred on these platforms undertheir designed protective potentials. Preliminary conclusions from indoor experiments on the relation betweenadhesive corrosion and cathodic protection showed adhering organisms caused the corrosion onthese platforms. 相似文献
102.
在△T异常解释课题中,一个新的角度参量─—视磁化特征角的拟定,最大限度地简化了球体磁场表达式。从而才有可能通过特殊解法,给出了球体磁场的极值与拐点公式。作者据此建立了四种不受正常场制约、仅需异常的局部持征曲线即可全面解释三度异常的解释方法。屏障分解、叠加判别、三元迭代的设计,为解释三度体叠加异常给出了简单而易行的途径。 相似文献
103.
网络经济是相对于大工业经济而言的,其网络企业经济效益的评价,可以从网络企业成本及收益两个方面讨论,然后以投入产出比等五个方面来建立其评价指标体系。 相似文献
104.
This study on the distribution features of petroleum hydrocarbon in water and sedi-ment off the Fujian shore using data obtained from the baseline research on oceanic contamination in Fujian showed that:during the research preiod,petroleum hydrocarbon concentrations in water varied from 5.77μg/L to 37.28μg/L,averaged 14.48 μg/L;was lower in the wet seasson than in the dry season;and was highest in the Minjiang Estuary and Jiulong Estuary in both seasons ,The petorleum hydrocarbon concentrations in shore sediment varied from 14.48 mg/kg to 784.36 mg/kg,averaged 133.3 mg/kg ,and was closely related to sediment types (granularity). 相似文献
105.
本文对徐州地震台JB—72水平摆倾斜仪1988年11月至1989年5月间所记录到的24次同震阶变进行了深入分析,认为:a.造成同震阶变的原因是多方面的,而反应了地球应变场准静态调整的同震阶变才是有价值的价变异常;b.多观测手段的地震台站,同震阶变应该在不止一台仪器上得到响应。 相似文献
106.
107.
利用三维有限元模拟两层地球模型(包括弹性层和粘弹性层)介质的横向不均匀和断层错动的复杂性对震后地表位移场的影响,其数值结果包括弹性解和粘弹性解。结果表明,震后位移场的分布特征不仅与粘弹性层的流变特性有关,还与弹性层介质的剪切模量以及断层的同震错动有关。 相似文献
108.
A coupled deterministic hydrological and water temperature model, CEQUEAU, was modified to include soil temperature and crown closure in its calculation of local advective terms in the heat budget. The modified model was than tested to verify its sensitivity to these modifications. An analysis of the heat budget of a small forested catchment in eastern Canada revealed that the advective term related to interflow plays a significant role in the daily water heat budget, providing on average 28% of the local advective budget (which also includes advective heat terms from surface runoff and groundwater) and nearly 14% of the total heat budget (which includes all radiative terms at the water surface, convection and evaporation, as well as the local advective terms). Relative sensitivity indices (RSIs) were used to verify the impact of the newly introduced parameters and variables. Among them, parameters related to the forest cover (crown closure and leaf area index) have a maximum RSI of ?0·6; i.e. a 100% increase in value produces a 60% decrease in the local advective term. Parameters with the greatest influence are the volume of water contributing to interflow and the amplitude of the net radiative flux at the soil surface, which, if doubled, would double the contribution of the local interflow advective term to the heat budget. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
109.
110.
For ecosystem modelling of the Boreal forest it is important to include processes associated with low soil temperature during spring‐early summer, as these affect the tree water uptake. The COUP model, a physically based SVAT model, was tested with 2 years of soil and snow physical measurements and sap flow measurements in a 70‐year‐old Scots pine stand in the boreal zone of northern Sweden. During the first year the extent and duration of soil frost was manipulated in the field. The model was successful in reproducing the timing of the soil warming after the snowmelt and frost thaw. A delayed soil warming, into the growing season, severely reduced the transpiration. We demonstrated the potential for considerable overestimation of transpiration by the model if the reduction of the trees' capacity to transpire due to low soil temperatures is not taken into account. We also demonstrated that the accumulated effect of aboveground conditions could be included when simulating the relationship between soil temperature and tree water uptake. This improved the estimated transpiration for the control plot and when soil warming was delayed into the growing season. The study illustrates the need of including antecedent conditions on root growth in the model in order to catch these effects on transpiration. The COUP model is a promising tool for predicting transpiration in high‐latitude stands. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献