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991.
辽宁省近50年霜的气候变化特征 总被引:3,自引:0,他引:3
主要使用辽宁省35个站点1957—2006年霜的地面观测资料以及相应时间的温度资料分析了该区霜的变化特征及其受气候变暖的影响,得到如下结论:近50年辽宁省初霜日期推迟近10 d,终霜日期提前约17 d,无霜期日数增加约26 d;初、终霜日期和无霜期日数在20世纪90年代初发生突变;从空间分布来看,初霜日期明显推后、终霜日期显著提前、无霜期增多的区域主要分布在辽宁中部、西部以及辽东半岛的部分地区;初霜日期与9月份各温度因子相关性较与其他各月高,终霜日期与4月份各温度因子相关性较强,无霜期主要受4—9月间各温度因子的影响;初霜期推迟、终霜期提前以及无霜期延长都主要是由温度的升高引起的,其中平均最低地面温度、平均最低气温是最重要的影响因素;伴随气候变暖,辽宁省初、终霜发生日期以及无霜期长度的空间分布都显示出由西南向东北方向推移的特点。 相似文献
992.
Vladislav Babuška Jiří Fiala Jaroslava Plomerová 《International Journal of Earth Sciences》2010,99(4):891-907
We present model of the structure and development of the entire lithosphere beneath the western Eger Rift (ER). Its crustal
architecture and paths of volcanic products are closely related to sutures/boundaries of uppermost mantle domains distinguished
by different orientations of olivine fabric, derived from 3-D analysis of seismic anisotropy. Three different fabrics of the
mantle lithosphere belong to the Saxothuringian (ST), Teplá-Barrandian (TB) and Moldanubian (MD) microplates assembled during
the Variscan orogeny. Dipping fossil (pre-assembly) olivine orientations, consistent within each unit, do not support any
voluminous mantle delamination. The variable rift structure and morphology depend on the character of the pre-rift suture
between the northern ST unit and the TB/MD units in the southern rift flank. The proper rift with typical graben morphology
has developed above the steep lithosphere-scale suture between the ST and TB units. This subduction-related boundary originated
from the closure of the ST Ocean. Parts of the crust and mantle lithosphere were dragged there into asthenospheric depths
and then rapidly uplifted. The suture is marked by abrupt change in the mantle fabric and sharp gradients in regional gravity
field and in metamorphic grade. The secular TB-side-down normal movement is reflected in deep sedimentary basins, which developed
since the Carboniferous to Cenozoic and in topography. The graben morphology of the ER terminates above the “triple junction”
of the ST, TB and MD mantle lithospheres. The junction is characterized by offsets of surface boundaries of the tectonic units
from their mantle counterparts indicating a detachment of the rigid upper crust from the mantle lithosphere. The southwest
continuation of the rift features in Bavaria is expressed in occurrences of Cenozoic sediments and volcanics above an inclined
broad transition zone between the ST and MD lithospheres. Schematic scenario of evolution of the region consists mainly of
a subduction of the ST lithosphere to depths around 140 km, exhumation of HP-HT rocks and the post-tectonic granitoid plutonism. 相似文献
993.
994.
David Beresford-Jones Sean Taylor Clea Paine Alexander Pryor Jiří Svoboda Martin Jones 《Quaternary Science Reviews》2011,30(15-16):1948-1964
Precisely how Upper Palaeolithic human ecology was shaped by changing climate during the Pleniglacial remains a matter of debate, for while this generally cold period is now understood to include complex and often rapid flux in climate, there are still considerable difficulties in resolving climatic variations at particular times and places — derived from various lines of proxy evidence — with the high-resolution proxy record of temperature changes from oxygen isotope analysis of the Greenland ice-cores.In this paper we apply the methodology of large-scale flotation to newly excavated contexts from the Upper Palaeolithic (Gravettian) site of Dolní V?stonice II, Czech Republic, to explore the potential of charcoal — as a natural archive of environmental information — to offer information on environmental change towards the end of the middle pleniglacial during Oxygen Isotope Stage 3, between c. 32,500 and 31,200 Cal yr BP. The results of an analysis of ring widths and other anatomical features — interpreted alongside micromorphological data — indicate that this charcoal may capture a higher-resolution record of the changing climatic conditions during which humans were first expanding into these hitherto marginal ecologies and, consequently, shed new light upon the complexity of the lifeways that enabled them to do so. 相似文献
995.
William L. Balsam Brooks B. Ellwood Junfeng Ji Earle R. Williams Xiaoyong Long Ahmed El Hassani 《Quaternary Science Reviews》2011,30(19-20):2732-2744
The magnetic susceptibility of soils has been linked with climate, mainly through rainfall, by numerous investigators. For this study we assembled a worldwide dataset of 272 samples, both published and new, to determine the nature of the relationship between MS and rainfall. On a worldwide basis there is a crude relationship (r2 = 0.265) between MS and rainfall. MS increases with increasing rainfall from about 200 mm/yr to 1000–1200 mm/yr. Above 1200 mm/yr, MS decreases as rainfall increases up to about 2000 mm/yr. Under arid and semi-arid conditions, below about 200 mm/yr of rainfall, MS and rainfall exhibit no relationship, likely the result of limited pedogenic activity.When tropical and temperate localities are analyzed separately, the correlation between MS and rainfall exhibits a dramatic improvement, r2 = 0.568 and 0.520, respectively. For similar amounts of rainfall tropical localities generally exhibit lower MS values which may be related to differences in the seasonal variation of rainfall. Because the soil environment is highly variable, it is unlikely that a global or even regional equation could accurately estimate rainfall from MS. Using data from Morocco and Mali we demonstrate that local equations using only MS to estimate rainfall produce reasonable results, r2 = 0.700 for Morocco and 0.611 for Mali. However, a single independent variable is unlikely to capture the variability of the complex soil system. To the local equations described above we experimented with adding several independent variables in addition to MS including diffuse reflectance spectral data (DRS), x-ray diffraction (XRD), and x-ray fluorescence (XRF). For DRS data, % reflectance and red, yellow, and near-infrared wavelengths appear important; for XRD illite and kaolinite counts are important whereas for XRF Fe2O3 is important. The addition of these other independent variables dramatically improves prediction quality. In the case of the Mali transect, estimating rainfall from these variables produces an r2 that exceeds 0.9. Based on these data we conclude that MS has the potential to be a reasonable proxy of rainfall for mean annual precipitation values from 200 to 2000 mm/yr, especially if local equations are used. Predictions can be improved by including other independent variables that show sensitivity to climate and are related to MS through the chemistry of the weathering process; we included DRS, XRD, and XRF data with good results. 相似文献
996.
997.
本文通过对工程建设项目的实例分析,研究其在建设和运营过程中遭受地质灾害的危险性,以及工程建设诱发或加剧地质灾害的可能性,进而提出相宜的地质灾害防治对策,以确保工程建设的质量和安全,减少经济损失,保护环境。 相似文献
998.
基于GIS和单元簇的模糊逻辑推理及其在区域矿产预测中的应用 总被引:2,自引:1,他引:2
论述了 GIS支持下的一种基于“单元簇”概念和模糊逻辑推理的多元地学信息综合分析方法及其在区域矿产预测中的应用。针对以往矿产定量预测中的单元划分方法对空间信息利用不足的问题 ,用单元的空间组合 (“单元簇”)代替单元作为定量类比的基本单位 ,从而能较充分地利用地质变量的局部空间结构信息 ;将单元作为 GIS区图元 ,利用 GIS空间分析功能实现对单元及单元簇的管理和操作 ;建立两个层次即变量对单元和组成单元对单元簇的模糊推理规则 ,经两次模糊推理计算出所有未知单元的找矿有利度 ,为进一步圈定找矿远景区提供了基础 ,并以新疆康古尔塔格地区金矿预测实例说明了其应用效果 相似文献
999.
1000.