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991.
Malcolm L. Spaulding Mark Reed Eric Anderson Tatsusaburo Isaji J.Craig Swanson Saul B. Saila Ernesto Lorda Henry Walker 《Estuarine, Coastal and Shelf Science》1985,20(1):41-53
An oil spill fishery impact assessment model system has been applied to the Georges Bank-Gulf of Maine region to assess the sensitivity of probable impact on several key fisheries to spill location and timing. Simulations of the impact on the fishery of tanker spills (20 million gallons released over 5 days), at two separate locations for each season of the year, and blowout spills (68 million gallons released over 30 days) at one location, with monthly releases and at six other locations with seasonal spills have been studied. Atlantic cod has been employed as the principal fish species throughout the simulations. Impacts on Atlantic herring and haddock have also been investigated for selected cases. All spill sites are located on Georges Bank with the majority in the general region of OCS leasing activity.The results of these simulations suggest a complex interaction among spill location and timing, the spatial and temporal distribution of spawning, the population dynamics of the species under study, and the hydrodynamics of the area. For the species studied, spills occurring during the winter and spring have the largest impact with cod being the most heavily impacted followed by haddock and herring. In all cases, the maximum cumulative loss to the fishery of a one time spill event never exceeded 25% of the annual catch with the exact value depending on the number of ichthyoplankton impacted by the spill and the compensatory dynamics of the population. 相似文献
992.
Garnets from recrystallized, staurolite- and kyanite-bearing mica schists from the central Saualpe basement, representing the host rocks of the type-locality eclogites, give concordant Sm–Nd garnet–whole-rock isochron ages between 88.5±1.7 and 90.9±0.7 Ma. The millimetre-sized, mostly inclusion-free grains show fairly homogeneous element profiles with pyrope contents of 25–27%. Narrow rims with an increase in Fe and Mn and a decrease in Mg document minor local re-equilibration during cooling. According to phengite geothermobarometry, peak metamorphic conditions at 90 Ma were close to 20 kbar and 680 °C and similar to those recorded by the eclogites. The garnet rims record about 575 °C/7 kbar for the final stages of metamorphism. A phengitic garnet–mica schist, sampled at the immediate contact with the Gertrusk eclogite, gave a garnet–whole-rock Sm–Nd age of 94.0±2.7 Ma.
Garnet porphyroclasts separated from a pegmatite–mylonite of the Koralpe plattengneiss near Stainz are unzoned and show spessartine contents of 15%. Composition and Sm–Nd ages of close to 260 Ma point to a magmatic origin for these garnets.
The garnet data from the Saualpe document an intense Alpine metamorphism for this part of the Austroalpine basement. The mica schists recrystallized during decompression and rapid exhumation, at the final stages of and immediately following a high- P event. The Koralpe data show that high Alpine temperatures did not reopen the Sm–Nd isotope system, implying a closure temperature in excess of c . 600 °C for this isotopic system in garnet. 相似文献
Garnet porphyroclasts separated from a pegmatite–mylonite of the Koralpe plattengneiss near Stainz are unzoned and show spessartine contents of 15%. Composition and Sm–Nd ages of close to 260 Ma point to a magmatic origin for these garnets.
The garnet data from the Saualpe document an intense Alpine metamorphism for this part of the Austroalpine basement. The mica schists recrystallized during decompression and rapid exhumation, at the final stages of and immediately following a high- P event. The Koralpe data show that high Alpine temperatures did not reopen the Sm–Nd isotope system, implying a closure temperature in excess of c . 600 °C for this isotopic system in garnet. 相似文献
993.
在东汤峪地区已有地质工作的基础上,进一步研究了区内地质构造特征,着重分析了山前断裂的构造特征及演化史,认为山前断裂经历了挤压和拉张交替作用的多期(次)活动过程;并探讨了该区温泉的构造控制因素,认为东汤峪温泉主要由区内山前断裂所控制。 相似文献
994.
995.
试论中西地理思想的差异及中国古代地理学的特点 总被引:1,自引:0,他引:1
于希贤 《云南地理环境研究》1993,5(1):7-14
中国古代有独持的地理学的理论与成就,西方科学家称之为“东方文化生态”。其中,”天人合一”的地理观;天、地、生、人各系统之间的整体、有机观体现了中国古代地理学的特点。深入发掘中国古代的地理学思想,对当今建立开放、复杂的地理巨系统有现实意义。 相似文献
996.
滇东下寒武统“沧浪铺组”解体为红井哨组和乌龙箐组 总被引:2,自引:0,他引:2
在从事滇东地区区调工作时,对下寒武统进行了系统的岩石地层和生物地层研究,建立了层序地层格架,表明"沧浪铺组"内部存在一个α型层序边界(Type Sequence Boundary),代表了范围较广泛的海平面迅速下降。以此为线索,发现"沧浪铺组红井哨段、乌龙箐段"之间存在着岩性岩相的明显差异,且与贵州地区对比缺少了两个生物带。以沧浪铺组标准剖面和辅助剖面研究为基础,着重分析了其解体的必要性。 相似文献
997.
对中国东部五个有代表性的碱性花岗岩体氢氧同位素研究表明,δ18O基本正常的苏州和福州碱性花岗岩D亏损分别受单阶段与连续岩浆去气作用的影响,后期大气降水的扰动相对较弱.D-18O同步亏损特征明显的碾子山和山海关碱性花岗岩则主要受岩浆期后大气降水高温亚固态同位素交换机理的制约青岛复式花岗岩基则较为复杂,可能受岩浆去气与晚期大气降水交换的联合作用.未明显受后期地质作用扰动、典型的中国东部碱性花岗岩浆氢氧同位素组成分别为δD=(50±5)‰和δ18=(7.5±1.0)‰这表明中国东部碱性花岗岩是由稳定同位素组成基本正常的内地壳或上地幔物质通过低程度部分熔融产生的,而不是由再循环亏损源区物质产生的低δ18O岩浆结晶分异形成的.中国东部碱性花岗岩总体上表现出的D亏损纬度效应,预示自中生代以来其所在板块位置未发生过大规模水平位移同时,碱性花岗岩与拉张环境之间的内在联系表明,至少在中生代中国东部大陆岩石圈地壳处于拉张减薄状态. 相似文献
998.
The Commission on Geological Sciences for Environmental Planning (COGEOENVIRONMENT) of IUGS and UNESCO have initiated a joint
project to develop a worldwide data base on earth-science-related environmental problems and to assess which geoscientific
information is available locally for prevention, prediction or mitigation of such problems. As a first step, a pilot project
on geo-environmental problems and geo-information was launched for central and eastern Europe. In this paper the results of
a questionnaire sent to all these partly new countries are presented. Analysis of the results of the questionnaire shows that
the most serious and common geo-environmental problems in central and eastern Europe are earthquakes, landslides, soil contamination,
groundwater pollution and flooding by rivers. Other geo-environmental problems in this part of Europe and some difficulties
experienced during the pilot project are also referred to. Some suggestions for the application of geoscientific knowledge
to mitigate such problems are presented at the end of this paper.
Received: 25 February 1997 · Accepted: 28 January 1998 相似文献
999.
胶东莱西地区高压基性麻粒岩的变质作用 总被引:28,自引:19,他引:9
胶东地区莱西-莱阳-栖霞-带晚太古代花岗片麻碉中,出露相当规模的高压基性麻业岩和超镁铁质岩组合,曾被认为它们是与苏鲁-大别超高压碰撞造山作用有关的一套岩石组合,高在性麻粒岩中可同三期变质矿物组合;早期为Grt核部)+Cpx+Pl;中期为Grt(边中)+Cpx+Opx+Pl+Amp+Q+Mt;晚期为Cpx+Pl+Amp+Q+Mt。早期的石榴石含钱铝榴石和镁铝榴石组分较高,单斜辉石含Al高。应用矿物温 相似文献
1000.
东昆仑早石炭世火山岩的地球化学特征及其构造背景 总被引:13,自引:0,他引:13
东昆仑早石炭世火山岩主要沿昆中缝合带及其旁侧分布,岩性以玄武岩为主,之后亦有安山岩和英安岩产出,先后形成于洋脊、洋岛和岛弧构造环境。洋脊玄武岩K2O、P2O5、SiO2、REE含量和FeO/MgO比值低,钙、铁、镁高,轻重稀土元素分馏差。岛弧玄武岩硅、碱、铝和REE含量以及LREE/HREE比值高,镁、铁质低。洋岛玄武岩TiO2和P2O5高,K2O低,REE和LREE/HREE介于前二者之间。火山岩的构造背景表明,早石炭世昆中断裂带以“开”为主,形成洋脊玄武岩和洋岛玄武岩;早石炭世末转为“合”,形成岛弧型玄武岩、安山岩和英安岩。洋脊玄武岩的识别,对于研究区域构造及其演化甚为重要。 相似文献