全文获取类型
收费全文 | 33447篇 |
免费 | 6011篇 |
国内免费 | 8080篇 |
专业分类
测绘学 | 2702篇 |
大气科学 | 6854篇 |
地球物理 | 8283篇 |
地质学 | 16424篇 |
海洋学 | 3992篇 |
天文学 | 1366篇 |
综合类 | 3659篇 |
自然地理 | 4258篇 |
出版年
2024年 | 178篇 |
2023年 | 588篇 |
2022年 | 1520篇 |
2021年 | 1785篇 |
2020年 | 1440篇 |
2019年 | 1685篇 |
2018年 | 1830篇 |
2017年 | 1684篇 |
2016年 | 1968篇 |
2015年 | 1721篇 |
2014年 | 2094篇 |
2013年 | 1974篇 |
2012年 | 1909篇 |
2011年 | 1985篇 |
2010年 | 2112篇 |
2009年 | 1949篇 |
2008年 | 1803篇 |
2007年 | 1716篇 |
2006年 | 1347篇 |
2005年 | 1263篇 |
2004年 | 958篇 |
2003年 | 963篇 |
2002年 | 914篇 |
2001年 | 951篇 |
2000年 | 1096篇 |
1999年 | 1498篇 |
1998年 | 1202篇 |
1997年 | 1138篇 |
1996年 | 1047篇 |
1995年 | 919篇 |
1994年 | 793篇 |
1993年 | 715篇 |
1992年 | 573篇 |
1991年 | 452篇 |
1990年 | 337篇 |
1989年 | 313篇 |
1988年 | 272篇 |
1987年 | 153篇 |
1986年 | 145篇 |
1985年 | 95篇 |
1984年 | 101篇 |
1983年 | 75篇 |
1982年 | 65篇 |
1981年 | 58篇 |
1980年 | 41篇 |
1979年 | 34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
11.
12.
We use the following numerical model for the collapse stage of a Type II supernova of 15 M⊙. Our electron capture rate includes the effects of the inverse reaction and the neutron-proton mass difference. This decreases the electron density at the collapse stage and led to rather large values of the maximum inward velocity and of the corresponding mass (Umax = 3.06 × 109cm/s, Mmax=0.76 M⊙). These larger values are more favourable for the propagation of shock after the rebounce and the triggering-off of a Type-II supernova explosion. For neutrino transport, we use a leakage model and an equilibrium diffusion model, respectively, for the thin and thick stages and a grey atmosphere model to assess the effect of neutrino precipitation on the collapse. We found this effect to be small, the energy precipitation to be not more than 10?5 the neutrino energy loss and the momentum precipitation not more than 10?6 the gravitational acceleration. 相似文献
13.
Sdsealbedoisdefinedasaratioofreflectivesolarradiationtototalacradiation,whichcanindicatetheaborptionandreflectivecapabilityofthe~hforsolarradiation.Itisan~tfactortoinfluencethes~radiationbalance,espeiallyfortheformationandvariationoflocalndcroclirnate.Generally,theactualdatafromo~tionalstationSforrebationareedintheanalysisofsolacealal.HOwever,therepresentativenessOfthedateisIratedduetothescarcityofobservationalstationandunevendistributionofs~condition.Afterthe1960s,theanalysisfors~ealbedoise… 相似文献
14.
A new technique designed to help quantify the degree of damage to the landscape from one area to another shows a close relationship between population density and the degree of landscape damage. The technique establishes a scale of damage from 0 to 5 (zero = no damage; 5 = severe damage) using data from aerial photographs, land-use maps, and field data. The related formula allows one to compare the relative degree of damage across regions using a combination of an absolute index, a theoretical index, a relative index, and population density. Xing'an County is used to demonstrate the technique. 相似文献
15.
16.
A new species,Clathrocorys gracilis nov. spec. of Tripocyrtidae (Radiolarians: Nassellaria) from surface water in northern South China Sea, is described in this
paper. The new species has four radial beams arising from the cephalic base centre, each foot with cup-shaped structure and
ramified bar in the proximal section (near cephalic base), and each wing with a large mesh in the middle, a medium mesh and
a small mesh on each side respectively.
Project supported by the NSFC (No. 40276044) and the Chinese Academy of Sciences (No. KSCX2-SW-101B). 相似文献
17.
本文用完全动力学程式计算了Ⅰ型超新星爆发。这些模型是依据氦或碳和氧构成星核,部分地或全部地产生瞬时完成的核燃烧。计算中将动力学方程、核统计平衡、Rayleigh-Taylor不稳定性等物理过程联合起来求解。重点比较了Rayleigh-Taylor不稳定性的影响,现不能作出完全肯定的结论。计算结果列在表1、表2和图2—6中。 相似文献
18.
着重讨论了网络用户经济效益的内涵以及用户的投入量和产出量,并提出了评价网络用户经济效益的指标体系,包括成本降低率,成本利润增长率、产品开发时间约率、市场占有增长率等系列指标。 相似文献
19.
Li Chongyin 《大气科学进展》1993,10(1):41-53
In a simple semi-geostropic model on the equatorialβ-plane, the theoretical analysis on the 30-60 day oscillation in the tropical atmosphere is further discussed based on the
wave-CISK mechanism. The convection heat-ing can excite the CISK-Kelvin wave and CISK-Rossby wave in the tropical atmosphere
and they are all the low-frequency modes which drive the activities of 30-60 day oscillation in the tropics. The most favorable
conditions to excite the CISK-Kelvin wave and CISK-Rossby wave are indicated: There is convection heating but not very strong
in the atmosphere and there is weaker disturbance in the lower troposphere.
The influences of vertical shearing of basic flow in the troposphere on the 30-60 day oscillation in the tropics are also
discussed. 相似文献
20.
Shi Zhi-dong Li Zhong-yuanUniversity of Science Technology of China Hefei PRC Advanced Centre for Earth Science Astronomy Third World Academy of Science 《紫金山天文台台刊》1996,(2)
Areview about K-H instability related to comet tail is presented.The effect of dust graing on KHI is theoretically analysed and relations of critical shear to excit KHI with the properties of dust grains both for sheared ion flow and for sheared dust flow re put out.Their possible application in comet tail is suggested. 相似文献