全文获取类型
收费全文 | 14169篇 |
免费 | 2095篇 |
国内免费 | 2141篇 |
专业分类
测绘学 | 1220篇 |
大气科学 | 3499篇 |
地球物理 | 2997篇 |
地质学 | 4216篇 |
海洋学 | 1555篇 |
天文学 | 139篇 |
综合类 | 826篇 |
自然地理 | 3953篇 |
出版年
2024年 | 48篇 |
2023年 | 136篇 |
2022年 | 432篇 |
2021年 | 593篇 |
2020年 | 609篇 |
2019年 | 715篇 |
2018年 | 557篇 |
2017年 | 737篇 |
2016年 | 697篇 |
2015年 | 764篇 |
2014年 | 876篇 |
2013年 | 1280篇 |
2012年 | 842篇 |
2011年 | 911篇 |
2010年 | 738篇 |
2009年 | 900篇 |
2008年 | 909篇 |
2007年 | 906篇 |
2006年 | 801篇 |
2005年 | 744篇 |
2004年 | 574篇 |
2003年 | 499篇 |
2002年 | 451篇 |
2001年 | 377篇 |
2000年 | 349篇 |
1999年 | 319篇 |
1998年 | 288篇 |
1997年 | 291篇 |
1996年 | 188篇 |
1995年 | 191篇 |
1994年 | 171篇 |
1993年 | 144篇 |
1992年 | 105篇 |
1991年 | 63篇 |
1990年 | 49篇 |
1989年 | 31篇 |
1988年 | 42篇 |
1987年 | 15篇 |
1986年 | 15篇 |
1985年 | 14篇 |
1984年 | 13篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1977年 | 3篇 |
1954年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
891.
Fu Liangkui 《地球科学》1986,(2)
本文阐明了反向变分流系统地下电流的分布特点和规律。文中还给出了反向变分流电阻率法视电阻率的异常表达式,计算了装置系数和电流分配系数之间的关系,并阐明其规律和作用。最后,作为一个例子,分析了水平地层上反向变分流电测深法视电阻率的异常分布规律,并指出它在勘探中的作用。 相似文献
892.
T. Spencer 《地球表面变化过程与地形》1995,20(1):49-64
Coral islands formed of largely unconsolidated sands only a few metres above sea level are thought to be particularly vulnerable to sea-level rise consequent upon global warming. However, scenarios which predict catastrophic flooding and loss of island area need reassessment, particularly in the light of the continued downwards revision of projected rates of future sea-level rise. Revised questions concern the interactions between reef growth and sea-level change, biophysical constraints on coral growth, and the importance to reef systems of potential changes in the magnitude, frequency and location of tropical cyclones and hurricanes. It is clear that most reefs have the growth potential to meet even the highest of future sea-level rise scenarios, but too little is known about physiological and physical constraints to reef growth to adequately evaluate the importance of these two factors in constraining this potential at the present time. Future sea-level rise in the tropical oceans, and coral reef responses, will take place against a backdrop of inter-regional differences in Holocene sea levels, resulting from the varying interaction of eustatic and hydro-isostatic processes. These differences have generated varying constraints on the development of modern reefs and varying inherited topographies upon which future sea-level changes will be superimposed. These controls are particularly important in assessing differences in vulnerability to future sea-level rise for reef islands in the Pacific Ocean and the Caribbean Sea. 相似文献
893.
西影井自1974年观测以来,动态比较稳定,干扰很明显,反映地壳应力变比较灵敏,但从1989年10月中旬开始,出现了大幅度,长时间的复杂多样的异常变化。经过研究,初步认为,这是一次大区域地壳构造运动引起的水位异常。 相似文献
894.
大强固区之间的相互作用和震后运动可以引起触发,强固区破裂引起相邻强固区加载。震后运动可以在大范围内发生并引起相邻区域的不均匀应变积累。观测表明大震后首先发生中等地震的地点正好是下次大震的位置,所以任何一个大地震发生都提供了一个探寻临界破裂区的良好时机。依据1960—1980年资料总结的中期地震危险性估测方法称为“诱发前震图象”,1981—1992年的地震资料完全证实了该方法的可靠性。 相似文献
895.
兴1井是辽宁省内最早建成的静水位观测井,已有近20年的观测历史。系统分析预测以来的资料,发现该井水位有很强的映震能力并有一定的映震规律,可进行单井水位异常预报地震震级与发震时间的科学试验。 相似文献
896.
西影井水位自1974-1978年三次井溢后,1989年9月以来又出现了一次大起大落的特异变化。很多学者都十分关注这罕见的现象,并认为是区域应力增强所致的。经过多年的调查与分析,笔者认为是大量抽取地下水引起的地面沉降与地裂并由此导致地下岩层的层间错动与井管变形破坏的结果。 相似文献
897.
This paper studies the relationship between water level step-variation anomalies and regional seismic activity.The train of thinking is as follows:First,a series of water level step-variation anomalies are regarded as sequential step-variation anomalies; next,these sequential anomalies are divided into several sub-sequential anomalies according to the temporal density of step-variations in different segments of the sequence; then the generation and evolution processes of various sub-sequential anomalies are analyzed to find their relation with regional moderate-strong earthquake activities,and finally the various sub-sequential anomalies are synthesized as sequential anomalies so as to analyze their relation with the tendency of seismic activities.By the above method,this paper has analyzed the relationship between a series of water level step-variation anomalies at the Wanquan well since 1981 and several regional moderate-strong earthquake activities.According to the monthly frequency,amplitude and tre 相似文献
898.
Peng-Jun Zhao 《地震学报(英文版)》1995,8(2):317-323
Based on the partial differential equation governing the effect of atmospheric pressure on water level of confined well, deriving
the boundary condition and considering the seepage water between well and aquifer, the author obtained the analytical solution
of water level change in time domain under the action of an atmospheric pressure history with the Laplace transform method.
This solution is composed of two terms:stable and retarded terms. The stable term is the multiplication of barometric efficiency
and simultaneous atmospheric pressure, and it implies the value of water level after infinite time when the atmospheric pressure
is a constant from the time in question. The retarded term is the transient process due to the time lag of water exchange
between well and aquifer. From the solution, it is obtained that the interference of atmospheric pressure on water level is
the integral superimposition of the contribution of all atmospheric pressure changes before the time in question. So that,
we further found out the response function of pulsive atmospheric pressure history. Calculation shows: (1) The pulsive response
function starts from zero and tends to a steady value, which is proportional to the barometric efficiency, when the time tends
to infinity; (2) The retarded time depends on the mechanical property of aquifer and the radius of well. The larger the seepage
coefficient, the smaller the radius of well and the thicker the aquifer, then the shorter the retarded time gets. This solution
can be used as the theoretical basis for further analysis of the atmospheric effect and practical correcting method in the
future. 相似文献
899.
ANALYSIS OF SURFACE AIR TEMPERATURE RECORDED IN LAHORE AND MIANWALI OVER THE PAST THREE DECADES
下载免费PDF全文
![点击此处可从《Acta Meteorologica Sinica》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Surface air temperatures recorded over the past three decades at the weather stations located in Lahore (anindustrialized and densely populated city) and Mianwali (a small and sparsely populated city) were analyzed in order tostudy their climatic trend.Lahore,where meteorological data are recorded at two weather stations (city station and air-port station) indicates a cooling trend,of about 0.5℃ per record period of 1953—1992,for the airport station (31°31′N,74°24′E) and a slight warming trend,of about 0.2℃,for the city station (31°33′N,74°20′E) for the record period of 1950—1992.The Mianwali weather station (32°33′N,71°31′E) also shows a slight cooling trend,of about 0.4℃ per recordperiod of 1959—1992.The climatic variability at these stations was studied by computing seasonal and annual tempera-ture anomalies.The results are explained in terms of the local environmental conditions. 相似文献
900.