首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   9468篇
  免费   2593篇
  国内免费   2143篇
测绘学   682篇
大气科学   1747篇
地球物理   3889篇
地质学   2813篇
海洋学   3183篇
天文学   148篇
综合类   909篇
自然地理   833篇
  2024年   30篇
  2023年   132篇
  2022年   259篇
  2021年   332篇
  2020年   396篇
  2019年   492篇
  2018年   407篇
  2017年   414篇
  2016年   420篇
  2015年   531篇
  2014年   551篇
  2013年   585篇
  2012年   638篇
  2011年   610篇
  2010年   464篇
  2009年   581篇
  2008年   590篇
  2007年   796篇
  2006年   657篇
  2005年   591篇
  2004年   576篇
  2003年   492篇
  2002年   418篇
  2001年   388篇
  2000年   350篇
  1999年   340篇
  1998年   350篇
  1997年   269篇
  1996年   277篇
  1995年   271篇
  1994年   233篇
  1993年   194篇
  1992年   147篇
  1991年   121篇
  1990年   69篇
  1989年   73篇
  1988年   49篇
  1987年   32篇
  1986年   22篇
  1985年   15篇
  1984年   6篇
  1983年   6篇
  1982年   2篇
  1980年   5篇
  1979年   3篇
  1978年   3篇
  1977年   3篇
  1954年   14篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
991.
V. P. Singh 《水文研究》2002,16(12):2441-2477
Kinematic wave solutions are derived for transport of a conservative non‐point‐source pollutant during a rainfall‐runoff event over an infiltrating plane for two cases: (i) finite‐period mixing and (ii) soil‐mixing zone. Rainfall is assumed to be steady, uniform and finite in duration, and it is assumed to have zero concentration of pollutants. Infiltration is assumed constant in time and space. Prior to the start of rainfall, the pollutant is distributed uniformly over the plane. In the first case, when rainfall occurs, the mixing of pollutant in the runoff water occurs in a finite period of time. In the second case, the chemical concentration is assumed to be a linearly decreasing function of rainfall intensity and overland flow. The solute concentration and discharge are found to depend on the flow characteristics as well as the solute concentration parameters. The characteristics of solute concentration and discharge graphs seem to be similar to those reported in the literature and observed in laboratory experiments. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
992.
993.
The monitoring of the perturbed motion of artificial satellites since the 1960's has provided a valuable resource for improved activities in geodesy. These observations and the improved geodetic techniques they fostered have provided an unparalleled means for studying both the gravity field and the Earth's shape. In this paper, we will review the various determinations of the Earth's gravity field produced at many research centers over the years from space techniques. The specific methods which have been used to measure our planet, such as satellite altimetry and satellite orbital perturbation analyses (over short and long periods of time), will be compared.  相似文献   
994.
995.
Miniature gravity corer for recovering short sediment cores   总被引:12,自引:0,他引:12  
  相似文献   
996.
One of the important consequences of a newly discovered secular dynamical evolution process of spiral galaxies (Zhang, 1996, 1998, 1999) is that the orbiting disk matter receives energy injection each time it crosses the spiral density wave crest. This energy injection has been shown to be able to quantitatively explain the observed age-velocity-dispersion relation of the solar neighborhood stars. We demostrate in this paper that similar energy injection into the interstellar medium could serve as the large-scale energy source to continuously power the observed interstellar turbulence and to offset its downward cascade tendency. This revised version was published online in September 2006 with corrections to the Cover Date.  相似文献   
997.
We demonstrate how Sakharov's idea of induced gravity allows one to explain the statistical-mechanical origin of the entropy of a black hole. According to this idea, gravity becomes dynamical as the result of quantum effects in the system of heavy constituents of the underlying theory.The black hole entropy is related to the properties of the vacuum in the induced gravity in the presence of the horizon. We obtain the Bekenstein-Hawking entropy by direct counting the states of the constituents.  相似文献   
998.
mODUCnONGravityflowsedimentationonthenorthwsterncontinentalsl0PeoftheSOuthChinaSea(SCS)are0fgreatinterestfromthescientificandengineeringP0intofview-Th0roughknOWedgofcontinentalsloPepmeessesanddepositionfeatUresispreregUisiteforhydID-carbenexploraion0fdeepwaerandforprotectionofoffhoredrineeopneeringstrUcbes(PlaifonnsandpiPelines)againstnaedhed.ManykindsofmassmovmentPIDCess-eswerefoUndtobeactiveonthen0rthernSCS(Damuth,l979;l98O).High-freqUency(3.5ffo)echo-chaIaCterInaPPingisawell…  相似文献   
999.
中国东南陆缘大地水准面的确定   总被引:1,自引:0,他引:1  
利用我国东南地区11822个重力数据、30″×30″数值地形模型和WDM94重力位模型,以Stokes理论为基础,采用低通滤波方法处理远区影响,计算了中国东南陆缘2.5′×2.5′格网重力大地水准面,其结果与福建、山东的GPS水准相比较,精度分别为±0.124m和±0.062m。  相似文献   
1000.
在介绍由高程异常确定大地水准面有关理论的同时,提出了用地形质量计算重力异常垂直梯度的方法,结合高程异常资料,可以使山区大地水准面得到精化。将本方法应用于珠穆朗玛峰,获得其大地水准面高为- 30.36 m 。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号