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41.
We present a mathematical model of local, steady groundwater flow near a vertical barrier wall. Flow features represented in the model include an impermeable arc-shaped barrier wall and multiple wells; distant boundary conditions are not included explicitly, but their effects on the local flow field are modelled by specifying a uniform flow at infinity and a constant areal recharge within a local domain. We develop an explicit closed-form solution to the boundary-value problem using the analytic element method. The solution is an extension of a harmonic solution presented by Anderson and Mesa [Anderson EI, Mesa E. The effects of vertical barrier walls on the hydraulic control of contaminated groundwater. Adv Water Resourc 2006;29(1):89–98] which does not include the effects of recharge. We demonstrate that the general solution with recharge consists of the harmonic solution superposed on a special case of the harmonic solution along with two elementary one-dimensional flow solutions. The results are used to investigate the effects of areal recharge on the capture zone envelopes of the pumping wells and on the reduction in discharge that can be achieved by including a barrier wall in a pump and treat design. We find that the benefits of including an open barrier wall in a design, measured as a reduction in the pumping rate required to contain a plume, increase for higher recharge rates. Dimensionless plots of capture zone envelopes are presented for a practical well and barrier wall configuration. 相似文献
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44.
George W. Housner 《地震工程与工程振动(英文版)》2008,7(2):I0001-I0001
Destructive earthquakes have caused great damage in China and the United States and collapsing buildings havecaused many deaths and injuries. The field of earthquake engineering studies earthquake hazards, the occurrence ofearthquakes of various magnitudes, the nature of the ground shaking during an earthquake, the vibration of structuresduring earthquakes, the strengthening of existing structures and the design of new structures to be earthquake resistant,and finally, how to cope with earthquake damage and restore a city to normal functioning. Such efforts are in progressin both countries, but unfortunately, the language barrier interferes with the free flow of information between China andthe Untied States. It would be mutually beneficial if some means could be developed to promote the exchangeof information across the Pacific Ocean. This new journal has been established for this purpose and its success willbe an important step in promoting earthquake engineering in China and the United States. 相似文献
45.
中国大陆基底可以分为4个区域:西域克拉通和东亚克拉通具太古代-早元古代变质基底,蒙藏增生陆块与华南增生陆块为元古代基底.在西域克拉通内可以识别出南塔里木陆核分布区、准噶尔陆核分布区与伊犁陆核;在东亚克拉通内可以勾画出燕吕陆核分布区、黄淮陆核分布区、秦岭陆核分布区和扬子陆核分布区.在克拉通形成的同时或稍后,在克拉通的两侧发育巨型基底断裂.在东亚克拉通的东西侧为郯庐断裂带与东亚克拉通西缘断裂带;在西域克拉通的南北为阿尔金断裂带与阿尔曼大断裂带.在蒙藏地块中部通过的日喀则-狼山断裂带是位于两克拉通之间的重要断裂带. 相似文献
46.
针对低频Rayleigh表面波,设计了部分埋入式工字形截面周期波屏障。利用有限元方法计算了结构的频散曲线,分析了带隙的形成机理,讨论了屏障埋入土体深度和截面参数对带隙的影响,在此基础上设计了具有低频超宽衰减域的梯度及分段梯度波屏障并计算了其传输谱。结果表明:周期波屏障存在较宽带隙,板埋入深度和端部尺寸是影响带隙的关键参数,通过参数调节可实现不同频段Rayleigh波的调控。工字形变截面波屏障比等截面具有更优越的隔震性能且节省材料。梯度及分段梯度波屏障显著拓宽了衰减域的频率范围,对1.5~20 Hz范围内的Rayleigh表面波实现了全覆盖,用小尺寸控制了大波长。 相似文献
47.
Hazel Rymer Benjamin van Wyk de Vries John Stix Glyn Williams-Jones 《Bulletin of Volcanology》1998,59(5):345-355
Persistent activity at Masaya Volcano, Nicaragua, is characterised by cycles of intense degassing, lava lake development
and pit crater formation. It provides a useful site to study the processes which govern such activity, because of its easy
accessibility and relatively short cycles (years to decades). An understanding of the present activity is important because
Masaya is visited by large numbers of tourists, is located close to major cities and has produced voluminous lavas, plinian
eruptions and ignimbrites in the recent past. We provide structural and geophysical data that characterise the "normal" present
state of activity. These indicate that the ongoing degassing phase (1993 to present) was not caused by fresh magma intrusion.
It was associated with shallow density changes within the active Santiago pit crater. The activity appears to be associated
predominantly with shallow changes in the pit crater structure. More hazardous activity will occur only if there are significant
departures from the present gravity, deformation and seismic signatures.
Received: 16 May 1997 / Accepted: 29 October 1997 相似文献
48.
辽西坳陷中的断陷盆地边缘逆冲断层发育。本文描述了逆冲断层的TM影像特征,解译划分了逆冲断裂带,并指出逆冲断层对找煤远景解译推断的意义。具体分析了南票、北票矿区外围的找煤远景,还应用影像特征探索性地对逆冲断层倾角进行了解译分类。 相似文献
49.
根据散列式居民地中独立房的分布特点,提出了一种适合此类居民地的聚类方法。此法利用邻近原则,将符合聚类条件的独立房快速找出,并聚类在一起,并且本方法不存在过于复杂的运算,速度较快。同时,本文还分析了顾及障碍物的情况下独立房聚类的条件。 相似文献
50.