全文获取类型
收费全文 | 18395篇 |
免费 | 4177篇 |
国内免费 | 5885篇 |
专业分类
测绘学 | 1706篇 |
大气科学 | 3293篇 |
地球物理 | 5179篇 |
地质学 | 10948篇 |
海洋学 | 3267篇 |
天文学 | 1307篇 |
综合类 | 1282篇 |
自然地理 | 1475篇 |
出版年
2024年 | 57篇 |
2023年 | 230篇 |
2022年 | 520篇 |
2021年 | 666篇 |
2020年 | 738篇 |
2019年 | 923篇 |
2018年 | 803篇 |
2017年 | 851篇 |
2016年 | 878篇 |
2015年 | 1023篇 |
2014年 | 1340篇 |
2013年 | 1202篇 |
2012年 | 1315篇 |
2011年 | 1404篇 |
2010年 | 1257篇 |
2009年 | 1416篇 |
2008年 | 1325篇 |
2007年 | 1564篇 |
2006年 | 1496篇 |
2005年 | 1254篇 |
2004年 | 1196篇 |
2003年 | 1012篇 |
2002年 | 799篇 |
2001年 | 663篇 |
2000年 | 675篇 |
1999年 | 631篇 |
1998年 | 608篇 |
1997年 | 475篇 |
1996年 | 410篇 |
1995年 | 349篇 |
1994年 | 332篇 |
1993年 | 224篇 |
1992年 | 214篇 |
1991年 | 149篇 |
1990年 | 103篇 |
1989年 | 125篇 |
1988年 | 68篇 |
1987年 | 51篇 |
1986年 | 26篇 |
1985年 | 21篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 9篇 |
1980年 | 5篇 |
1977年 | 2篇 |
1976年 | 7篇 |
1973年 | 4篇 |
1971年 | 2篇 |
1954年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
对武汉区域气象中心并行计算机系统进行了详细地介绍,分析了并行计算机体系结构、网络和存储系统特点;给出了在并行计算机SP上实现数值预报业务并行化的部分结果;对数值预报模式在串、并行编程环境下的结果进行了分析比较。 相似文献
72.
张赤军 《大地测量与地球动力学》2002,22(4):31-34
介绍当今确定天文大地垂偏差的新仪器-CCD自动天体测量仪和确定两点间高程异常差的新方法,该方法用单极坐标代替繁琐的双极坐标进行计算,讨论了天文重力水准的误差及垂线偏差非线性影响等问题,估计在不久的将来,用这一手段施测山区似大地水准面的精度可望达到厘米级。 相似文献
73.
张晓晖 《成都信息工程学院学报》2002,17(3):166-169
通过对影响能见度的因素的分析,提出了一种能见度预报方法-综合分析法,极大地提高了能见度的预报准确率。 相似文献
74.
Dark energy has a dramatic effect on the dynamics of the Universe, causing the recently discovered acceleration of the expansion. The dynamics are also central to the behaviour of the growth of large-scale structure, offering the possibility that observations of structure formation provide a sensitive probe of the cosmology and dark energy characteristics. In particular, dark energy with a time-varying equation of state can have an influence on structure formation stretching back well into the matter-dominated epoch. We analyse this impact, first calculating the linear perturbation results, including those for weak gravitational lensing. These dynamical models possess definite observable differences from constant equation of state models. Then we present a large-scale numerical simulation of structure formation, including the largest volume to date involving a time-varying equation of state. We find the halo mass function is well described by the Jenkins et al. mass function formula. We also show how to interpret modifications of the Friedmann equation in terms of a time-variable equation of state. The results presented here provide steps toward realistic computation of the effect of dark energy in cosmological probes involving large-scale structure, such as cluster counts, the Sunyaev–Zel'dovich effect or weak gravitational lensing. 相似文献
75.
Victor A. Avdyushev 《Celestial Mechanics and Dynamical Astronomy》2003,87(4):383-409
Mainly, the author focuses on Baumgarte's method and its applications in satellite, asteroid, stellar and planetary problems. In the paper arguments are given for the use of energy relations for stabilization in the elliptical two-body problem. Stabilizing properties of Baumgarte's equations and others are discussed. A simple approach is proposed for stabilizing the equations of almost circular motion. By using Baumgarte's technique, the author derives stabilized equations of perturbed restricted three-body problem. It is shown experimentally that stabilization in the problems mentioned above can raise the accuracy of numerical integration by several orders. 相似文献
76.
In this paper a slightly different approach is proposed for the process of determining the functions S
m
and H
m
* of the algorithm of the canonical version of Hori method. This process will be referred to as integration theory of the mth order equation of the method. It will be shown that the ordinary differential equation with an auxiliary parameter t
* as independent variable, introduced through Hori auxiliary system, can be replaced by a partial differential equation in the time t. In this way, the mth order equation of the algorithm assumes a form very similar to the one of other perturbation methods. In virtue of this new approach of the integration theory for Hori method, Lagrange's variational equations introduced by Sessin are revised. As an example, the Duffing equation is solved through this new approach. 相似文献
77.
用电测深研究地电断面、寻找隐伏多金属矿体时,以往采用ρ_s(或η_s)等值线断面图进行地质推断解释,因受浅源信号的干扰,效果差。本文提出了采用ρ_s(或η_s)差值法,能排除浅源干扰信号,反映出地电断面的相对变化,突出了深部微弱信息,取得了较好的地质解释效果。 相似文献
78.
79.
Geoff Kite 《水文研究》1993,7(2):227-233
Using current meters to estimate flows in fast mountain streams is difficult and inaccurate. The salt dilution method offers an easier and more accurate alternative. The method has been used for many years but is time consuming and messy because of the need to mix chemical solutions and measure chemical concentrations in the field. A computer program has been developed which uses a laptop computer to calculate the mixing length and the mass of salt needed. The program controls the conductivity measurements and calculates the streamflow directly in the field. The development of this program is described and examples are presented of the application of the method in the Rocky Mountains of Alberta and British Columbia. 相似文献
80.
为了给公路设计部门提供选线依据,运用瞬变电磁法在山西境内的某两条高速公路隧道工程设计线路段上进行探测,以查明下覆不良地质构造的发育情况.通过对瞬变电磁法的探测能力进行理论上的讨论,对不同地电断面情况下的异常体电磁响应的定性分析,得出用瞬变电磁法探测不良地质体的可行性结论.经过资料处理,查出不良地质构造赋存的位置,解释结果与钻探资料完全吻合. 相似文献