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251.
阻尼对应力波传播的影响 总被引:2,自引:0,他引:2
基于一维应力波理论,本文讨论了材料粘性(内阻尼)及作用于杆侧表面外阻尼对应力波传播的影响,应力波在外阻尼作用下,向上传播-应力波,该应力波在端面质点速度方向与入射波质点速度相反,而内阻尼则使材料具有松弛、蠕变行为,作用力终止后,端面质点速度缓慢地回复到零。无论是内阻尼还是外阻尼。受其影响,应力波在向下传播过程中,能量有一定程度的耗损 相似文献
252.
253.
Zhang Zhaochong Chai Fengmei Yan Shenghao Chen Bailin He Lixin He Yongsheng Zhou Gang 《Frontiers of Earth Science》2007,1(1):44-48
The Sr, Nd and O isotopic compositions of the Kalatongke and Xibodu mafic-ultramafic complexes from the southern margin of
the Altay orogenic belt show that they have similar isotopic compositions, characterized by low (87Sr/86Sr), and high ε
Nd(t) values (6.3–9.1). It suggests that they were derived from a depleted asthenospheric mantle. However, most of the samples
have δ
18O values >6‰ (5.4‰–10.2‰), indicating crustal contamination. A combination of Sr and O isotopic data shows the incorporation
of crustal materials into the depleted mantle. They were produced by the melting of depleted mantle by the incorporation of
subducted oceanic crust, and this incorporation might have occurred in the Early Paleozoic in the light of their Nd model
ages and regional tectonics. The Kalatongke complex might have undertaken the contamination of the upper crust whereas the
Xibodu complex does not have any signature of contamination of the upper crust. In addition, the similarities of the sources
of the two complexes, which were located at the northern and southern sides of the regional Irtysh fault zone respectively,
suggest that this fault might not be the boundary between the Altay and Junggar orogenic belts.
Translated from Geological Review, 2006, 52(1): 38–42 [译自: 地质论评] 相似文献
254.
On the Generation Algorithm of VRS Virtual Observations 总被引:1,自引:0,他引:1
WEI Erhu CHAI Hua LIU Jingnan AN Zhiguo 《地球空间信息科学学报》2007,10(2):91-95
255.
256.
Depositional and Diagenetic Controls on Pore Structure of Tight Gas Sandstone Reservoirs: Evidence from Lower Cretaceous Bashijiqike Formation in Kelasu Thrust Belts,Kuqa Depression in Tarim Basin of West China
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Deeply buried Lower Cretaceous Bashijiqike sandstones are important gas exploration targets in the Kelasu thrust belt, Kuqa Depression of Tarim Basin in China. The sandstones are characterized by low porosity, low permeability and strong microscopic heterogeneity due to diagenesis during their geologic history. Mineralogical, petrographic, and geochemical analyses combined with high‐pressure mercury injection analysis have been used to investigate the diagenesis, diagenetic minerals, and their impact on reservoir quality. This article addresses the controls exerted by depositional parameters and diagenetic modifications on pore‐network characteristics (porosity, pore types, sizes, shapes, and distribution), with the aim to unravel the formation mechanisms of this complex pore structures, and to improve the characterization and classification evaluation for the Bashijiqike sandstone reservoirs. The Bashijiqike sandstones are dominated by lithic arkoses and feldspathic litharenite. The pore system consists of intergranular macropores, intergranular micropores, and intragranular pores. Framework grains are generally heavily compacted. Authigenic quartz, authigenic feldspar, clay minerals and carbonates are the major pore‐filling constituents. The pore structure is characterized by small pore radius and poor interconnectivity. Entry pressure reflects the microscopic pore network and macroscopic reservoir property characteristics. Pore structure characteristics are linked to the depositional parameters, type and degree of diagenesis. Clays do not control reservoir pore networks alone, and pores and pore throats are wider in coarser grained sandstones. Entry pressure decreases with the content of the rigid quartz. Compaction and cementation continue to decrease the pore‐throat size, while dissolution enlarges pores and pore‐throats radius. Considerable amounts of microporosity associated with clay minerals and altered grains contribute to the high entry pressure. Comprehensive Coefficient of Diagenesis (CCD), which considers the integrative effect of diagenesis, shows strong statistical correlations with entry pressure. CCD is an integrative modulus of diagenesis and physical property, and generally the higher the values are, the better the pore structure. It is suitable for quantitatively characterizing pore structure in tight gas sandstones. The results of this work can help assess pore‐network characteristics like the Bashijiqike sandstones which had experienced strong diagenetic modifications during their geological history. 相似文献
257.
Meili?Chi Haishen?WenEmail author Meng?Ni Kun?Qian Pei?Zhang Senhao?Chai 《中国海洋大学学报(英文版)》2015,14(4):717-723
The RNA helicase Vasa is an important regulator of primordial germ cell development. Its function in mature fish, especially the hormone-related differences in maturing male fish has seldom been documented. In this study, a full length cDNA sequence of the vasa gene was cloned from Japanese sea bass, Lateolabrax japonicas, and it was named jsb-vasa. Homology analysis showed that jsb-vasa was closely related to its teleost homologs. The spatial distribution of jsb-vasa indicated that it was only highly expressed in testis, showing its germ cell-specific expression pattern. During the testicular development cycle, jsb-vasa was highly expressed during early period of spermatogenesis, and reduced when spermatogenesis advanced. In addition, the jsb-vasa gene expression was significantly inhibited at 6 h, 12 h and 24 h after injecting hCG (human chorionic gonadotropin) and GnRHa (Gonadotropin-releasing hormone analogue), indicating that jsb-vasa gene may play an important role in spermatogenesis of Japanese sea bass, and be under the regulation of external sex hormones. 相似文献
258.
Ha Da Zheng Gang Loáiciga Hugo A. Guo Wei Zhou Haizuo Chai Jinchun 《Acta Geotechnica》2021,16(4):1303-1314
Acta Geotechnica - A large volume of groundwater is withdrawn annually in Tianjin Municipality, China, to meet agricultural, industrial, and municipal water uses. Groundwater overdraft in the urban... 相似文献
259.
The South China Sea(SCS)is the largest semi-enclosed marginal sea in the western Pacific.The alternation of East Asian monsoon causes a significant seasonal pattern of chlorophyll,primary productivity,and export flux of sinking particles.However,the source and sink of dissolved organic carbon(DOC)pools with different bioavailability are less studied.Here we evaluated the seasonal production of DOC in labile,semi-labile and refractory forms using a coupled physical-biogeochemical model.This study aims to understand the dynamics and budgets of organic matters in the SCS.Model results show that the production of labile,semi-labile and refractory DOC is highly correlated with the net primary productivity(NPP)which is higher in winter and lower in summer,reflecting a dependence of DOC on the NPP.The seasonal variation in Pearl River discharge dominates the DOC production in the northern coastal region.In the northeast,the Kuroshio intrusion associated frontal system is attributed to cause high winter production.The DOC production in the southwest is controlled by both winter mixing and summer upwelling.The production of refractory DOC with the least bioavailability favors carbon sequestration.Its annual mean production is 1.8±0.5 mg C m?2 d?1,equivalent to 26%of the export flux of particulate organic carbon at 1000 m. 相似文献
260.
The Yingchengzi gold deposit, located 10 km west of Shalan at the eastern margin of the Zhangguangcai Range, is the only high commercially valuable gold deposit in southern Heilongjiang Province, NE China. This study investigates the chronology and geodynamic mechanisms of igneous activity and metallogenesis within the Yingchengzi gold deposit. New zircon U–Pb data, fluid inclusion 40Ar/39Ar dating, whole‐rock geochemistry and Sr–Nd isotopic analysis is presented for the Yingchengzi deposit to constrain its petrogenesis and mineralization. Zircon U–Pb dating of the granite and diabase–porphyrite rocks of the igneous complex yields mean ages of 471.7 ± 5.5 and 434 ± 15 Ma respectively. All samples are high‐K calc‐alkaline or shoshonite rocks, are enriched in light rare earth elements and large ion lithophile elements, and are depleted in high field strength elements, consistent with the geochemical characteristics of arc‐type magmas. The Sr–Nd isotope characteristics indicate that the granite formed by partial melting of the lower crust, including interaction with slab‐derived fluids from an underplated basaltic magma. The primary magma of the diabase–porphyrite was likely derived from the metasomatized mantle wedge by subducted slab‐derived fluids. Both types of intrusive rocks were closely related to subduction of the ocean plate located between the Songnen–Zhangguangcai Range and Jiamusi massifs. However, fluid inclusion 40Ar/39Ar dating indicates that the Yingchengzi gold deposit formed at ~249 Ma, implying that the mineralization is unrelated to both the granite (~472 Ma) and diabase–porphyrite (~434 Ma) intrusions. Considering the tectonic evolution of the study area and adjacent regions, we propose that the Yingchengzi gold deposit was formed in a late Palaeozoic–Early Triassic continental collision regime following the closure of the Paleo‐Asian Ocean. In addition, the Yingchengzi deposit could be classified as a typical orogenic‐type gold deposit occuring in convergent plate margins in collisional orogens, and unlikely an intrusion‐related gold deposit as reported by previous studies. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献