全文获取类型
| 收费全文 | 4482篇 |
| 免费 | 749篇 |
| 国内免费 | 1127篇 |
专业分类
| 测绘学 | 233篇 |
| 大气科学 | 446篇 |
| 地球物理 | 1131篇 |
| 地质学 | 3161篇 |
| 海洋学 | 457篇 |
| 天文学 | 213篇 |
| 综合类 | 234篇 |
| 自然地理 | 483篇 |
出版年
| 2024年 | 19篇 |
| 2023年 | 77篇 |
| 2022年 | 129篇 |
| 2021年 | 169篇 |
| 2020年 | 190篇 |
| 2019年 | 219篇 |
| 2018年 | 158篇 |
| 2017年 | 175篇 |
| 2016年 | 210篇 |
| 2015年 | 192篇 |
| 2014年 | 262篇 |
| 2013年 | 230篇 |
| 2012年 | 247篇 |
| 2011年 | 268篇 |
| 2010年 | 223篇 |
| 2009年 | 287篇 |
| 2008年 | 302篇 |
| 2007年 | 303篇 |
| 2006年 | 286篇 |
| 2005年 | 240篇 |
| 2004年 | 233篇 |
| 2003年 | 184篇 |
| 2002年 | 209篇 |
| 2001年 | 155篇 |
| 2000年 | 187篇 |
| 1999年 | 189篇 |
| 1998年 | 137篇 |
| 1997年 | 119篇 |
| 1996年 | 130篇 |
| 1995年 | 101篇 |
| 1994年 | 80篇 |
| 1993年 | 86篇 |
| 1992年 | 69篇 |
| 1991年 | 50篇 |
| 1990年 | 51篇 |
| 1989年 | 41篇 |
| 1988年 | 39篇 |
| 1987年 | 25篇 |
| 1986年 | 22篇 |
| 1985年 | 17篇 |
| 1984年 | 15篇 |
| 1983年 | 7篇 |
| 1982年 | 7篇 |
| 1980年 | 1篇 |
| 1979年 | 2篇 |
| 1978年 | 8篇 |
| 1977年 | 1篇 |
| 1976年 | 1篇 |
| 1975年 | 1篇 |
| 1954年 | 4篇 |
排序方式： 共有6358条查询结果，搜索用时 171 毫秒
1.
Heat-shock protein 70 expression in shrimp Fenneropenaeus chinensis during thermal and immune-challenged stress 总被引：4，自引：0，他引：4
Using western immunoblotting, we obtained heat-shock protein 70 (HSP70) induction data and distribution in different tissues from shrimp Fenneropenaeus chinensis during thermal and immune-challenged stresses. This is probably the first report of the effects of various stressors on the expression of HSP70 in shrimp.HSP70 was prominently induced in hepatopancreas and gills, but not in muscle, eyestalk and hemolymph, when the shrimp were exposed to heat shock and Vibrio anguillavium-challenged stresses. Cold shock and WSSV treatment had no significant effects on the levels of HSP70 expression in all tissues examined. HSP70 induction was greatest after 2 h exposure to heat shock stress, which was elevated after acute heat shock exposure of 10℃ above ambient temperature. 相似文献
2.
3.
4.
阿吾拉勒山体西段发育了厚度巨大的下二叠统火山岩,这些火山岩均属碱性玄武岩系列,以钾质类型为主,钠质类型次之,岩浆演化呈现出跨越B型趋势。这种火山活动是在大陆地壳内部产生的,代表了陆内裂谷演化的早期阶段。在早二叠世末期,由于受到新源运动的影响,这种火山活动被终止了。 相似文献
5.
C. Dickinson R. D. Davies R. J. Davis 《Monthly notices of the Royal Astronomical Society》2003,341(2):369-384
A full-sky template map of the Galactic free–free foreground emission component is increasingly important for high-sensitivity cosmic microwave background (CMB) experiments. We use the recently published Hα data of both the northern and southern skies as the basis for such a template.
The first step is to correct the Hα maps for dust absorption using the 100-μm dust maps of Schlegel, Finkbeiner & Davis. We show that for a range of longitudes, the Galactic latitude distribution of absorption suggests that it is 33 per cent of the full extragalactic absorption. A reliable absorption-corrected Hα map can be produced for ∼95 per cent of the sky; the area for which a template cannot be recovered is the Galactic plane area | b | < 5°, l = 260°–0°–160° and some isolated dense dust clouds at intermediate latitudes.
The second step is to convert the dust-corrected Hα data into a predicted radio surface brightness. The free–free emission formula is revised to give an accurate expression (1 per cent) for the radio emission covering the frequency range 100 MHz–100 GHz and the electron temperature range 3000–20 000 K. The main uncertainty when applying this expression is the variation of electron temperature across the sky. The emission formula is verified in several extended H ii regions using data in the range 408–2326 MHz.
A full-sky free–free template map is presented at 30 GHz; the scaling to other frequencies is given. The Haslam et al. all-sky 408-MHz map of the sky can be corrected for this free–free component, which amounts to a ≈6 per cent correction at intermediate and high latitudes, to provide a pure synchrotron all-sky template. The implications for CMB experiments are discussed. 相似文献
The first step is to correct the Hα maps for dust absorption using the 100-μm dust maps of Schlegel, Finkbeiner & Davis. We show that for a range of longitudes, the Galactic latitude distribution of absorption suggests that it is 33 per cent of the full extragalactic absorption. A reliable absorption-corrected Hα map can be produced for ∼95 per cent of the sky; the area for which a template cannot be recovered is the Galactic plane area | b | < 5°, l = 260°–0°–160° and some isolated dense dust clouds at intermediate latitudes.
The second step is to convert the dust-corrected Hα data into a predicted radio surface brightness. The free–free emission formula is revised to give an accurate expression (1 per cent) for the radio emission covering the frequency range 100 MHz–100 GHz and the electron temperature range 3000–20 000 K. The main uncertainty when applying this expression is the variation of electron temperature across the sky. The emission formula is verified in several extended H ii regions using data in the range 408–2326 MHz.
A full-sky free–free template map is presented at 30 GHz; the scaling to other frequencies is given. The Haslam et al. all-sky 408-MHz map of the sky can be corrected for this free–free component, which amounts to a ≈6 per cent correction at intermediate and high latitudes, to provide a pure synchrotron all-sky template. The implications for CMB experiments are discussed. 相似文献
6.
We have developed a method for analytically solving the porous medium flow equation in many different geometries for horizontal (two‐dimensional), homogeneous and isotropic aquifers containing impermeable boundaries and any number of pumping or injection wells located at arbitrary positions within the system. Solutions and results are presented for rectangular and circular aquifers but the method presented here is easily extendible to many geometries. Results are also presented for systems where constant head boundary conditions can be emulated internal to the aquifer boundary. Recommendations for extensions of the present work are briefly discussed. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
7.
8.
1INTRODUCTIONWiththerecentmodernizationandurbanizationofChi-na,urbanareashavegreatlyincreased, andgiantbuild-ings,especiallythosetallerthan100m,havebeendomi-nantincities,whichhave resultedinthegreatincreaseintheproportionofbuilding'sexternalsurfacetototalurbanarea.Thedifferencesofthermalpropertiesmain-lyinducedbysolarradiationbetweenbuilding'sexter-nalsurfacesareobviousfordifferentexposures,whichcaninevitablyinfluencethedistributionsofairtempera-turenearby,eventheverticaldistributionsofurb… 相似文献
9.
金州地区广泛发育震旦纪地层,具分布连续、出露完整、沉积相标志明显的特点。本文运用现代沉积学和地层学理论,对区内震旦系岩石地层进行了基本层序研究与沉积环境分析。 相似文献
10.
青藏块体东北缘地壳水平运动状态 总被引：10，自引：6，他引：4
应用青藏块体东北缘1999～2003年多期GPS观测资料，计算了不同时段GPS点水平运动速率。通过分析发现：甘青块体可分为东部块体和西部块体，东、西部块体的运动状态存在明显的差异；受2001年11月14日昆仑Ms8．1地震的影响，震后地壳运动状态发生了明显的改变。 相似文献