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111.
大采深倾斜薄煤层底板采动破坏开态的连续探测 总被引:4,自引:0,他引:4
利用多回路钻孔注(放)水连续探测系统,结合断裂力学分析,了大采深倾斜薄煤层底板采动破坏特征与形态,结果表明底板破坏形态为一匙形,与厚煤层开采所形成的破坏形态相比其破坏特征的差异在于底板采动裂隙主要是原生节理裂隙的扩展,而工作面推过压实后,绝大部分裂隙又趋于闭合。 相似文献
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113.
寡-中营养型水体中,虽然营养盐水平偏低,但仍会偶发性出现较为严重的蓝藻水华现象,其具体机制仍有待深入探索研究.本研究以偶发水华水体方便水库为例,通过历史数据分析和调查研究,探讨了其水华蓝藻的优势类群,并分析了蓝藻水华形成的主要驱动因素.研究发现:方便水库优势的水华蓝藻为浮丝藻和长孢藻,这两种丝状蓝藻是发生偶发性蓝藻水华的潜在风险物种,其中浮丝藻的发生风险最高,风险时段为7-9月.方便水库多年来营养盐浓度呈现下降的趋势,其中总氮浓度的下降趋势快于总磷浓度,整体有利于蓝藻水华的防控,但是营养盐的波动,尤其是随着降雨导致的地表径流入库对水体总磷的脉冲式补充,降低了水体氮磷比,增加了水库偶发蓝藻水华的风险;在营养盐满足的条件下,水温、高锰酸盐指数和氧化还原电位是发生浮丝藻水华的主要驱动因素,氧化还原电位、水温和透明度是发生长孢藻水华的主要驱动因素.本研究结果有助于提升对偶发性蓝藻水华机制的认识和应急处置工作的精准性. 相似文献
114.
甘东南地区位于青藏高原东北部,受印度板块与欧亚板块碰撞及印度板块向北楔入挤压的影响,构造活动强烈,中强地震发生较为频繁( Dewey et al,1973;Tapponnier et al, 1982,2001;Métivier et al,1998;Molnar et al,2009).在大地构造上,该区地处中国南北... 相似文献
115.
根据田间试验观测资料,从SPAC(土壤-植物-大气连续统一体)系统出发,分析了南京地区冬小麦抽穗至黄熟阶段农田水分的能量耗散和物质耗散特点,找出了影响作物蒸腾的主要生理,生态因子以及它们之间的关系。 相似文献
116.
Examining the distribution and dynamics of impervious surface in different function zones in Beijing
Impervious surface (IS) is often recognized as the indicator of urban environmental changes. Numerous research efforts have been devoted to studying its spatio-temporal dynamics and ecological effects, especially for the IS in Beijing metropolitan region. However, most previous studies primarily considered the Beijing metropolitan region as a whole without considering the differences and heterogeneity among the function zones. In this study, the subpixel impervious surface results in Beijing within a time series (1991, 2001, 2005, 2011 and 2015) were extracted by means of the classification and regression tree (CART) model combined with change detection models. Then based on the method of standard deviation ellipse, Lorenz curve, contribution index (CI) and landscape metrics, the spatio-temporal dynamics and variations of IS (1991, 2001, 2011 and 2015) in different function zones and districts were analyzed. It is found that the total area of impervious surface in Beijing increased dramatically during the study period, increasing about 144.18%. The deflection angle of major axis of standard deviation ellipse decreased from 47.15° to 38.82°, indicating the major development axis in Beijing gradually moved from northeast-southwest to north-south. Moreover, the heterogeneity of impervious surface’s distribution among 16 districts weakened gradually, but the CI values and landscape metrics in four function zones differed greatly. The urban function extended zone (UFEZ), the main source of the growth of IS in Beijing, had the highest CI values. Its lowest CI value was 1.79 that is still much higher than the highest CI value in other function zones. The core function zone (CFZ), the traditional aggregation zone of impervious surface, had the highest contagion index (CONTAG) values, but it contributed less than UFEZ due to its small area. The CI value of the new urban developed zone (NUDZ) increased rapidly, and it increased from negative to positive and multiplied, becoming an important contributor to the rise of urban impervious surface. However, the ecological conservation zone (ECZ) had a constant negative contribution all the time, and its CI value decreased gradually. Moreover, the landscape metrics and centroids of impervious surface in different density classes differed greatly. The high-density impervious surface had a more compact configuration and a greater impact on the eco-environment. 相似文献
117.
本文对新郑市天利两周墓地居民的牙齿磨耗及口腔疾病进行了统计和分析,试图从古病理学的角度揭示当时居民的食物构成、饮食行为习惯及社会经济生活方式等。研究显示,天利两周墓地居民除了在牙釉质发育不良方面存在显著的两性差异,即男性明显高于女性外,在牙齿磨耗水平、牙齿生前脱落和龋病的患齿率上虽不存在明显的两性差异,但均表现为女性略高于男性。同时,与先秦时期不同地区、不同经济形态的古代居民相比,天利居民在前部牙齿,尤其是上颌前部的牙齿上表现出了较后部牙齿更为严重的磨耗。产生这些现象的原因一方面是天利墓地地处中原地区,旱作农业的谷类食物成为居民的主要食物来源,女性在牙齿生前脱落和龋病的患齿率及牙齿磨耗程度上略高于男性,说明两性在食物结构大致相同的情况下还存在少许差异,不同的劳动分工使得男性可能获得更多的动物性蛋白质和脂肪;对相关骨骼进行的稳定同位素分析显示,男性应该获取了比谷类食物更多的肉食,相对的,女性食物结构中的谷类比重则较大。另一方面,男性在牙釉质发育不良的患齿率上明显高于女性,说明该墓地的男性居民(尤其在幼年时期)普遍具有高于女性的生存压力;在牙釉质硬度降低、多用前部牙齿做工具使用及与女性相比,获取较多肉食的情况下,天利墓地男性居民相对于其他地区较明显的前部牙齿磨耗。
相似文献118.
潍北凹陷是昌潍坳陷的次一级凹陷盆地,也是传统油气开采区,潍北凹陷孔店组二段沉积了较厚的暗色泥岩、泥页岩、油页岩,多为良好的烃源岩,也是潍北凹陷内页岩气的主要生、储层位。通过分析昌页参1井现场解析实验数据,探讨了潍北凹陷孔店组二段地层损失气量、损失时间、样品深度、样品岩性等与解析气量的对应关系。分析现场解析实验数据发现,样品的损失气量大于解析气量,两者的变化趋势基本一致;深度相近、岩性相同时,解析气量随着损失时间的增长而减小,深度相近时,泥岩解析气量大于粉砂质泥岩;岩性相同时,解析气量随深度的增加而增加,增速随深度的增加而减小。 相似文献
119.
Guangsheng Chen Hanqin Tian Chi Zhang Mingliang Liu Wei Ren Wenquan Zhu Arthur H. Chappelka Stephen A. Prior Graeme B. Lockaby 《Climatic change》2012,114(2):379-397
Drought is one of the most devastating natural hazards faced by the Southern United States (SUS). Drought events and their adverse impacts on the economy, society and environment have been extensively reported during 1895?C2007. Our aim is thus to characterize drought conditions in the SUS and explore the impacts on terrestrial ecosystem function (i.e., net primary productivity (NPP) and net carbon exchange (NCE)). Standard precipitation index (SPI) was used to characterize drought intensity and duration, and a process-based ecosystem model was used to explore the relationship between drought and ecosystem function. Combining overall information on growing-season SPI, drought area and duration, we concluded there was no significant change in drought conditions for the SUS during 1895?C2007. However, increased drought intensity was found for many areas in the east, resulting in significant decreases in NPP for these areas, with the largest decrease up to 40% during extreme droughts. Changes in precipitation patterns increased C emissions of 0.16 Pg (1 Pg?=?1015?g) in the SUS during 1895?C2007. The west (dry region) acted as a C sink due to increased precipitation, while the east (water-rich region) acted as a C source due to increased drought intensity. Both NPP and NCE significantly increased along a gradient of declining drought intensity. Changes in precipitation resulted in C sources in forest, wetland, and cropland ecosystems, while C sinks in shrubland and grassland ecosystems. Changes in air temperature could either enhance or reduce drought impacts on NPP and NCE across different vegetation types. 相似文献
120.