全文获取类型
收费全文 | 22443篇 |
免费 | 3810篇 |
国内免费 | 6886篇 |
专业分类
测绘学 | 1367篇 |
大气科学 | 6096篇 |
地球物理 | 4222篇 |
地质学 | 7803篇 |
海洋学 | 8299篇 |
天文学 | 1364篇 |
综合类 | 1413篇 |
自然地理 | 2575篇 |
出版年
2024年 | 154篇 |
2023年 | 432篇 |
2022年 | 829篇 |
2021年 | 944篇 |
2020年 | 985篇 |
2019年 | 1146篇 |
2018年 | 948篇 |
2017年 | 1027篇 |
2016年 | 1032篇 |
2015年 | 1118篇 |
2014年 | 1512篇 |
2013年 | 1618篇 |
2012年 | 1464篇 |
2011年 | 1449篇 |
2010年 | 1252篇 |
2009年 | 1711篇 |
2008年 | 1561篇 |
2007年 | 1750篇 |
2006年 | 1498篇 |
2005年 | 1466篇 |
2004年 | 1191篇 |
2003年 | 1053篇 |
2002年 | 1039篇 |
2001年 | 844篇 |
2000年 | 736篇 |
1999年 | 712篇 |
1998年 | 558篇 |
1997年 | 515篇 |
1996年 | 448篇 |
1995年 | 390篇 |
1994年 | 357篇 |
1993年 | 344篇 |
1992年 | 262篇 |
1991年 | 185篇 |
1990年 | 137篇 |
1989年 | 124篇 |
1988年 | 76篇 |
1987年 | 50篇 |
1986年 | 37篇 |
1985年 | 45篇 |
1984年 | 33篇 |
1983年 | 24篇 |
1982年 | 21篇 |
1981年 | 24篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1978年 | 10篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1954年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
Sdsealbedoisdefinedasaratioofreflectivesolarradiationtototalacradiation,whichcanindicatetheaborptionandreflectivecapabilityofthe~hforsolarradiation.Itisan~tfactortoinfluencethes~radiationbalance,espeiallyfortheformationandvariationoflocalndcroclirnate.Generally,theactualdatafromo~tionalstationSforrebationareedintheanalysisofsolacealal.HOwever,therepresentativenessOfthedateisIratedduetothescarcityofobservationalstationandunevendistributionofs~condition.Afterthe1960s,theanalysisfors~ealbedoise… 相似文献
22.
讨论了应用曲面拟合技术和利用离散的重力观测点的重力变化对特定研究区的重力场变化进行数值模拟以获取该区重力变化空间梯度场图像的具体方法;并应用该方法获得了2004年3月福建安溪3.6级地震前的重力变化空间梯度场图像,发现空间梯度场图像能清晰地反映出地震前重力场群体性变化的差异性;利用此方法对2005年6月~2006年3月间台湾海峡西岸重力场变化进行数值模拟,获得其空间梯度场图像。 相似文献
23.
Hai-Ning LiNational Astronomical Observatories Chinese Academy of Sciences Beijing lhnDepartment of Astronomy Beijing Normal University Beijing 《中国天文和天体物理学报》2003,3(5)
We present a quantitative estimate of the relativistic corrections to the thermal SZ power spectrum produced by the energetic electrons in massive clusters. The corrections are well within 10% for current experiments with working frequencies below v < 100 GHz, but become non-negligible at high frequencies v > 350 GHz. Moreover, the corrections appear to be slightly smaller at higher l or smaller angular scales. We conclude that there is no need to include the relativistic corrections in the theoretical study of the SZ power spectrum especially at low frequencies unless the SZ power spectrum is used for precision cosmology. 相似文献
24.
利用 12年的Lageos 1卫星激光测距资料 (1990 - 2 0 0 1)解算得到了地球定向参数 (EOP) ,将该序列的结果与同期的EOP(IERS)C0 4进行比较 ,其外符精度为 :极移XP— 0 .4 0mas,YP— 0 .4 2mas ,日长变化Dr— 0 .0 35ms。 相似文献
25.
JINFeng-jun 《中国地理科学(英文版)》2003,13(2):97-103
It is very important to establish cooperative mechanism to guarantee all members to develop their e-conomies in the Yellow Sea Rim. In this paper, the development strategies ofshipplng centers and transportation networkare discussed based on economic giobalization tendency. The results argue that a united transportation network should bebuilt in order to promote the economic competition of Northeast Asia in the world. As a key component of the economiccooperation, a hierarchical shipping centers network should be established with Hong Kong, Shanghai, Pusan, Koho,and Tokyo as cores. The authorities of China, Japan, R. O. Korea and D. P. B. Korea should make more efforts tobuild a set of cooperation institutions based on raising the transportation efficiency. 相似文献
26.
CARBON DYNAMICS OF WETLAND IN THE SANJIANG PLAIN 总被引:2,自引:0,他引:2
SONG Chang-chun WANG Yi-yong WANG Yue-si YAN Bai-xing WANG De-xuan ZHAO Zhi-chun LOU Yan-jing 《中国地理科学(英文版)》2003,13(3):228-231
1INTRODUCTIONWetlandsplayanimportant roleintheprocessofcar-bonstorage.Thetotalcarbonstoredindifferentkindsofwetlandsisabout15%-35%ofthetotalcarboninthegloballandsoils(POSTetal.,1982;GORHAM,1991).Inaddition,wetlandsaresignificantnaturalsources fortheatmospheric CH4 (MOORE,1994).It isestimatedthatabout110×1012gCH4 originates fromanaerobicdecompositioninthenaturalwetlands,CH4 emission fromthenaturalwetlandsis15%-30%oftheglobalCH4 emission andtheCH4 emission from thepeat land at hi… 相似文献
27.
With the advent of either sensitive space-born infrared cameras, or their high-resolution ground-based siblings, we are uncovering
a new category of star clusters: the dust-enshrouded super-star clusters. These manifest themselves only beyond a few microns,
as their shroud of dust is able to block all light emitted by the stars themselves. Here we present our results on the spectacular
cluster in SBS 0335-052, a very metal-poor galaxy. We also point to the growing number of galaxy analogs to SBS 0335-052,
revealing the possibility that these clusters signal a major mode of star formation in starbursts. We conclude by listing
a number of open points these clusters raise, in particular with respect to high-redshift counterparts.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
28.
29.
Wei-Hao Bian Quan-Ling Cui Li-Hua Chao Department of Physics Institute of Theoretical Physics Nanjing Normal University Nanjing Key Laboratory for Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2006,6(3):281-286
We used multi-component profiles to model the Hβ and [OⅢ]λλ4959,5007 lines of SDSS J143030.22-001115.1, a narrow-line Seyfert 1 galaxy (NLS1) in a sample of 150 NLS1 candidates selected from the Sloan Digital Sky Survey (SDSS), Early Data Release (EDR). After subtracting the Hβ contribution from narrow line regions (NLRs), we found that its full width half maximum (FWHM) of broad Hβ line is nearly 2900km s~(-1) , significantly larger than the customarily adopted criterion of 2000 km s~(-1) . With its weak Fe Ⅱ multiples, we believe that SDSS J143030.22-001115.1 should not be classified as a genuine NLS1. When we calculate the virial black hole masses of NLS1s, we should use the Hβ linewidth after subtracting the NLR component. 相似文献
30.
在目前常用的周跳探测与修复方法基础上 ,提出了首先将观测资料按照观测历元不连续分成若干小弧段 ,然后利用差分法进行周跳探测 ,根据差分后周跳放大的特性判断周跳和野值 ,并确定其位置利用宽带组合和电离层组合的方法解算周跳大小。通过实例验证了其有效性。 相似文献