全文获取类型
收费全文 | 18340篇 |
免费 | 3290篇 |
国内免费 | 4196篇 |
专业分类
测绘学 | 1019篇 |
大气科学 | 3706篇 |
地球物理 | 5166篇 |
地质学 | 8773篇 |
海洋学 | 2565篇 |
天文学 | 771篇 |
综合类 | 1741篇 |
自然地理 | 2085篇 |
出版年
2024年 | 94篇 |
2023年 | 342篇 |
2022年 | 796篇 |
2021年 | 921篇 |
2020年 | 747篇 |
2019年 | 795篇 |
2018年 | 920篇 |
2017年 | 875篇 |
2016年 | 1004篇 |
2015年 | 823篇 |
2014年 | 1004篇 |
2013年 | 1091篇 |
2012年 | 957篇 |
2011年 | 998篇 |
2010年 | 1070篇 |
2009年 | 992篇 |
2008年 | 830篇 |
2007年 | 887篇 |
2006年 | 653篇 |
2005年 | 634篇 |
2004年 | 463篇 |
2003年 | 522篇 |
2002年 | 507篇 |
2001年 | 493篇 |
2000年 | 613篇 |
1999年 | 904篇 |
1998年 | 758篇 |
1997年 | 759篇 |
1996年 | 727篇 |
1995年 | 646篇 |
1994年 | 570篇 |
1993年 | 489篇 |
1992年 | 409篇 |
1991年 | 287篇 |
1990年 | 231篇 |
1989年 | 188篇 |
1988年 | 180篇 |
1987年 | 102篇 |
1986年 | 110篇 |
1985年 | 68篇 |
1984年 | 58篇 |
1983年 | 57篇 |
1982年 | 55篇 |
1981年 | 40篇 |
1980年 | 47篇 |
1979年 | 36篇 |
1978年 | 14篇 |
1977年 | 9篇 |
1974年 | 9篇 |
1958年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
In this study, a directional interpolation infinite element suited to a saturated porous medium is presented to account for dynamic problems with semi-infi 相似文献
2.
Barley(Hordeum vulgare L.) is one of the earliest domesticated crop species and ranked as the fourth largest cereal production worldwide. Forward genetic studies in barley have greatly advanced plant genetics during the last century; however, most genes are identified by the conventional mapping method. Array genotyping and exome-capture sequencing have also been successfully used to target the causal mutation in barley populations, but these techniques are not widely adopted because of associated costs and partly due to the huge genome size of barley. This review summarizes three mapping cases of barley cuticle mutants in our laboratory with the help of RNA-sequencing. The causal mutations have been successfully identified for two of them and the target genes are located in the pericentromeric regions. Detailed information on the mapping-by-sequencing, mapping-and-sequencing, and RNA-sequencing assisted linkage mapping are presented and some limitations and challenges on the mapping assisted by RNA sequencing are also discussed. The alternative and elegant methods presented in this review may greatly accelerate forward genetics of barley mapping, especially for laboratories without large funding. 相似文献
3.
4.
从太湖流域旱涝史料看历史气候信息处理 总被引:15,自引:1,他引:14
历史气候信息处理建立在信息提取的基础上,目的在于建立一套方法,将定性的历史气候信息转化为气候变化参数,并消除各种不均—性,从而建立历史气候序列。本文着重介绍建立太湖流域历史旱涝等级序列的方法与步骤: 1)确立信息源,建立信息网络;2)站点等级的确定与订正;3)弱信息处理;4)信息的综合。 相似文献
5.
Sdsealbedoisdefinedasaratioofreflectivesolarradiationtototalacradiation,whichcanindicatetheaborptionandreflectivecapabilityofthe~hforsolarradiation.Itisan~tfactortoinfluencethes~radiationbalance,espeiallyfortheformationandvariationoflocalndcroclirnate.Generally,theactualdatafromo~tionalstationSforrebationareedintheanalysisofsolacealal.HOwever,therepresentativenessOfthedateisIratedduetothescarcityofobservationalstationandunevendistributionofs~condition.Afterthe1960s,theanalysisfors~ealbedoise… 相似文献
6.
陈以良 《广东海洋大学学报》1992,(1)
用比电导法研究两种活性炭自稀水溶液中吸附强电解质硫酸铬和硫酸铜的吸附平衡特性。结果表明,在本文的研究条件下,两种活性炭对硫酸铬和硫酸铜都有吸附作用。同时,活性炭吸附硫酸铜的吸附平衡特性可以用 Freundlich 方程式来描述。研究的结果对固体在溶液中的吸附基础理论以及处理工业废水具有一定的意义。 相似文献
7.
8.
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
9.
Yunfei Bao Shengbo Chen 《东北亚地学研究》2006,9(1):100-108
IntroductionThe radiance leaving the earth-atmosphere sys-tem which can be sensed by a satellite borne ra-diometer is the sum of radiation emission fromtheearth surface and each atmospheric level that aretransmittedtothe top of the atmosphere.The radia-tion emissionfromthe earthsurface andthe radianceof each atmospheric level can be separated fromtheradiance at the top the atmospheric level a satellitemeasured.Thus,the earth surface parameters willbe retrieved from the surface radiance after a… 相似文献
10.
The response of natural vegetation to climate change is of global concern. In this research, an aggregated Holdridge Life Zone System was used to study the possible response of life zones in China under doubled atmospheric CO2 concentration with the input climatic parameters at 0.5×0.5° resolution of longitude and latitude from NCAR regional climate model 2 (RegCM2) coupled with the CSIRO global climate model. The results indicate that the latitudinal distribution of life zones would become irregular because of the complicated climate change. In particular, new life zones, such as subtropical desert (SD), tropical desert (TDE) and tropical thorn woodland (TTW), would appear. Subtropical evergreen broadleaved forest (SEBF), tropical rainforest and monsoon forest (TRF), SD, TDE and TTW zones would appear in the northeastern China. Cool-temperate mixed coniferous and broadleaved forest (CMC) and warm-temperate deciduous broadleaved forest (WDBF) zones would appear at latitudes 25–35°N. The temperate desert (TD) in the western China would become Tibetan high-cold plateau (THP), SEBF, WDBF and temperate steppe (TS), and a large part of THP would be replaced by TRF, TDE, SEBF, TS and TTW. The relative area (distribution area/total terrestrial area) of CMC, TRF, TDE and TTW zone would increase about 3%, 21%, 3% and 6%, respectively. However, the relative area of SEBF, TS, TD and THP would decrease about 5%, 3%, 19% and 4%, respectively. In all, the relative area of forests (CCF, CMC, WDBF, SEBF, TRF) would increase about 15%, but the relative area of desert (TD, SD, TDE, and TTW) and THP would decrease about 9% and 4%, respectively. Therefore, responses of different life zones in China to climate change would be dramatic, and nationwide corridors should be considered for the conservation of migrating species under climate change. 相似文献