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961.
白岗岩型铀矿是一种非常重要的岩浆型矿床,主要产于纳米比亚。罗辛铀矿是白岗岩型铀矿的典型矿床,该矿床目前仍是全球铀资源的主要提供者之一。文章对前人研究成果进行分析总结,概括了罗辛铀矿的区域地质背景和岩石地层系统,分析了铀矿床地质特征及矿床成因。研究认为:罗辛铀矿床形成时间为(508±2)Ma;铀的赋存以独立铀矿物为主,少量以类质同像形式存在于钍矿物中;含铀白岗岩相对富集大离子亲石元素Rb,K,Th,U和Pb,而相对亏损Ba,Nb,Sr,P和Ti;穹窿构造为岩体侵位成矿提供了空间,而岩浆的重熔结晶作用使得铀进入岩浆,并在局部富集成矿。 相似文献
962.
文章对产于津巴布韦大岩墙内的哈特利(Hartley)铂矿床的地质特征和成因进行研究。津巴布韦大岩墙于新太古代侵入,在津巴布韦克拉通内形成南北段次级岩浆房格局。哈特利铂矿的铂族元素主要分布在杂岩体的中下部,与硫化物密切相关,主要含矿矿物为铋、碲矿物。在岩浆侵位的过程中发生结晶分异,形成了铂族元素和硫化物的垂向分带。哈特利矿床与中国金川等铂族元素矿床相比,其成岩成矿时代早,矿床特征、成矿元素组合方面均有明显不同。 相似文献
963.
Considerable attempts have been made on removing the crosstalk noise in a simultaneous source data using the popular K-means Singular Value Decomposition algorithm ( KSVD ). Several hybrids of this method have been designed and successfully deployed, but the complex nature of blending noise makes it difficult to manipulate easily. One of the challenges of the K-means Singular Value Decomposition approach is the chal-lenge to obtain an exact KSVD for each data patch which is believed to result in a better output. In this work, we propose a learnable architecture capable of data training while retaining the K-means Singular Value Decom-position essence to deblend simultaneous source data. 相似文献
964.
965.
某工程拟在深水软土地基上修筑防波堤,为了尽量减少地基处理充分利用天然地基,创新性设计出一种轻型薄壁的预制防波堤结构,其挡浪部分为直立薄壁圆筒,基础部分则为倒扣的薄壁椭圆形桶,并且椭圆形下桶为外壁和内隔板分成9个格室,防波堤结构浮运至指定位置后,拟采用负压工法施工安装就位。这种新型防波堤结构为国内外首次提出,其下沉施工设计尚无规范可循,为此开展了土工离心模型试验,在模型加速过程中模拟了椭圆形下桶基础在淤泥层中的自重下沉,之后利用新研发了一种大行程作动加载装置给椭圆形下桶施加下推力,让其继续向下贯入直至穿越整个淤泥层,以模拟负压工法的贯入下沉。试验测量了下桶贯入下沉过程中的推力与贯入位移,还尝试测量了桶壁和内隔板断面的压应变,由此分析了下桶基础的下沉总阻力、桶壁摩擦力以及截面压应变随贯入位移的变化。结果发现,这些曲线均出现了转折点,根据转折点对应的下沉总阻力确定了椭圆形下桶基础贯入过程所遭遇的临界下沉总阻力值,据此估算了负压工法中所需施加的压力差。 相似文献
966.
In-situ measurements in Xiangshan Bay, the East China Sea, show that the duration of the rising tide is shorter than that of the falling tide around the bay mouth, while it becomes much longer in the inner bay. A finite volume coastal ocean model(FVCOM) with an unstructured mesh was applied to simulate the asymmetric tidal field of Xiangshan Bay. The model reproduced the observed tidal elevations and currents successfully. Several numerical experiments were conducted to clarify the roles of primary mechanisms underlying the asymmetric tidal field. According to the model results, the time-varying channel depth and nonlinear advection prefer shorter duration of the rising tide in Xiangshan Bay, while the time-varying bay width favors longer duration of the rising tide. The overtides generated by these two opposite types of nonlinear mechanisms are out of phase, resulting in smaller M4 amplitude than the sumfold of each individual contribution. Although the bottom friction as a nonlinear mechanism contributes little to the generation of overtide M4, it is regarded as a mechanism that could cause a shorter duration of the rising tide, for it can slow down the M2 phase speed much more than it slows down the M4 phase speed. The time-varying depth, nonlinear advection and bottom friction are dominating factors around the bay mouth, while the time-varying width dominates in the inner bay, causing the tidal elevation asymmetry to be inverted along the bay. 相似文献
967.
辽东湾表层沉积物碎屑矿物组合分布及其对物源和沉积物扩散的指示意义 总被引:1,自引:0,他引:1
对取自渤海辽东湾的128个表层沉积物样品进行了碎屑矿物鉴定,对矿物成分含量应用log-ratio法处理后进行统计分析。结果表明,研究区重矿物质量百分含量平均值为6.3%,高值区位于六股河口和湾西北近岸。共鉴定出7种轻矿物,38种重矿物,轻矿物以石英、斜长石和钾长石为主,重矿物以普通角闪石、绿帘石、磁铁矿、石榴子石、钛铁矿为主。根据碎屑矿物的组合分布特征,可将研究区划分为两个矿物组合区,其中又可细分为6个矿物亚区。六股河和湾西北近岸矿物亚区的碎屑矿物主要来源于六股河、湾西北入海小溪和海岸侵蚀物质,湾东北部矿物亚区沉积物主要来源于双台子河和大辽河,湾中部矿物亚区为多源混合区,湾南部矿物亚区受邻近海域和复州河沉积物影响大,湾东南部的辽东浅滩矿物亚区为潮流作用的产物。与河流入海沉积物相比,该区表层沉积物的石英/长石比值和ZTR指数明显增大。研究认为,物源是控制研究区碎屑矿物的组合与分布的主要因素,同时也受到海洋水动力和矿物性质等因素影响。 相似文献
968.
Land-use change is intertwined with tourism because land is used as a resource for human activities.Land-use change also provides an opportunity to evaluate the status of the ecoenvironment.Understanding the relationship between tourism and land use change would help to predict the effect of tourism on land use and encourage sustainable tourism development.Using the Li River Basin as a case study,a hybrid approach using multilevel modeling and logistic regressions was employed to analyze the distribution of land-usechange between 1989 and 2010 to examine potential driving factors.Results reveal that rapid tourism development and construction expansion expose this area to risk of deforestation and forest degradation.Construction increased by 141% between 1989 and 2000 and by 195% between 2000 and 2010.The primary driving force for construction expansion shifted from population growth between 1989 and 2000 to investment growth after 2000.New construction primarily occurred on crop and woodlands areas,with shares of 81.25% and 6.38%,respectively,between 1989 and 2000,and with shares of 57.79% and 15.29%,respectively,between 2000 and 2010.Moreover,these drastic increases in construction also led to frequent transitions between croplands,woodlands,and grasslands.Traits including distances to urban areas and roads and scenic locations exerted significant effects on land-use change.Woodland regrowth in the areas thatsurround scenic locations consisted of fluctuating woodlands,whereas stable woodland regrowth was often absent in these areas.Likewise,permanent woodland clearing tended to be closed to near scenic locations.That is,construction at scenic locations negatively affected forest conservation in the Li River Basin. 相似文献
969.
970.
使用高级积分方程模型,模拟多个地表参数条件下的风云三号B星微波成像仪(FY-3B/MWRI)资料。基于模拟数据,分析地表微波辐射特性,利用粗糙地表发射率Qp模型,建立我国西部地区裸露地表土壤湿度反演模型。将该模型用于我国西部地区4个日期(2011年10月8日、10月18日、10月28日和11月8日)的土壤湿度反演,并将反演结果用实测数据进行交叉验证。结果表明:反演土壤湿度与实测土壤湿度的决策系数R2为0.604,均方根误差为0.030 5 cm3/cm3,反演模型具有较高的反演精度。 相似文献