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271.
ZHANG Xiaoyu LI Chunlai L Chang Graduate University of Chinese Academy of Sciences Beijing China National Astronomical Observatories Chinese Academy of Sciences Beijing China 《中国地球化学学报》2009,28(2):204-211
In the second phase of the Chang’E Program an unmanned lunar rover will be launched onto the Moon. When ground scientists
get a full understanding of the chemical composition of lunar soil around the rover, they can make more detailed survey plans
for the rover and various payloads onboard so as to satisfy their scientific objectives. There is an obvious relationship
between the reflectance of lunar soil and its chemical characteristics. Both principal component analysis (PCA) and support
vector machine (SVM) models were applied to establishing the relationship between the reflectance spectra and chemical compositions
of lunar highland and mare soil samples sent back by Apollo missions 11, 12, 14, 15, 16 and 17 and measured by Lunar Soil
Characterization Consortium (LSCC). PCA was used to reduce and select the features of the reflectance spectra of lunar soil
samples. Then, these features were put into SVM to estimate the abundances of various chemical components in lunar soil. We
also compared the results of our measurement with those obtained by the SVM model [partial least squares (PLS)] and the principal
component regression (PCR) model reported in literature. Our studies showed that with the exception of TiO2, the results of prediction of the abundances of chemical compounds in lunar soil by our model are much more reliable than
those reported in literature. The reflectance spectra of lunar soil are closely related to the materials from which it was
derived. 相似文献
272.
平庄凹陷盖层中发育九佛堂组、沙海组和阜新组3套烃源岩,虽然以往围绕煤矿生产展开了大量的煤田地质勘探工作,但石油、天然气勘探工作较少,研究程度较低。为了客观评价平庄凹陷的油气资源,需对烃源岩有机质成熟度进行评判。在对平庄凹陷烃源岩岩石热解、镜质组反射率、生物标志物参数分析的基础上,对平庄凹陷九佛堂组、沙海组烃源岩有机质热演化特征及演化阶段进行了系统研究。结果表明:平庄凹陷烃源岩各参数随埋藏深度的增加变化明显,具有纵向上的连续性和横向上的不均匀性;平庄洼陷烃源岩有机质成熟度处于未成熟—低成熟—成熟阶段,其中,九佛堂组烃源岩是盆地的主要成油岩系;四龙洼陷烃源岩有机质成熟度较低,对盆地成烃贡献不大。 相似文献
273.
山西沁水盆地热史演化特征 总被引:4,自引:0,他引:4
沁水盆地是华北克拉通内的构造盆地,是天然气勘探的潜在重要区域,盆地的热史研究是天然气储层评价的重要基础。重点应用磷灰石裂变径迹的分析与模拟,配合镜质体反射率的分析与模拟以及区域构造地质背景分析,恢复了沁水盆地的古地温梯度和地热演化模型:早古生代地温梯度稳定,为3℃/100 m,晚二叠世至三叠纪地温梯度较前期略有降低,约为2.5~3.0℃/100 m;早、中侏罗世地温梯度开始上升,约为3.0~4.0℃/100 m;晚侏罗世—早白垩世地温梯度大幅度上升,为4.5~6.5℃/100 m;晚白垩世至古近纪早、中期为高地温场的延续时期,地温梯度为5.5~6.5℃/100 m;古近纪晚期—新近纪早期地温梯度大幅度降低,从6.0℃/100 m骤降至4.2℃/100 m左右;中新世以来地温场逐渐趋于稳定,地温梯度由4℃/100 m演变到接近现代地温场的3℃/100 m左右。 相似文献
274.
275.
Determination of multispectral specular reflectance is an important tool for ore identification in reflected light microscopy, and may be used for automated characterization of ores. However, reflectance values can be affected by compositional variations in a way that is seldom understood. The aim of the present work is to investigate this problem in chromite, an ore whose composition may show typically large natural variations as member of the spinel family, and whose relatively high reflectance variations are apparently unpredictable. For this research, eighteen samples of chromian spinel covering a large range of compositions in the base of the Hagerthy prism were selected for microprobe analysis and reflectance measure on polished sections. The samples belong to a variety of deposits and types (ultramafic massif, ophiolitic, and metamorphosed types: Ojén and Ronda Massifs, Spain; Mayarí, Moa-Baracoa, Camagüey and Sagua de Tánamo, Cuba; Golyamo Kemenyane, Avren and Yakovitsa, Bulgaria). The specular reflectances are characterized as multispectral values, measured at thirteen intervals (50 nm each) in the VNIR region (Visible and Near-Infrared: 400–1000 nm), using the automated CAMEVA System.The relationship between compositional and reflectance values is studied by multivariate analysis and subsequently tested on independent samples. For this purpose, the samples have been grouped in two sets: a larger population of fifteen samples constitutes the initial data set for mathematical processing, while a selection of three samples of widely differing compositions is used to test the resulting functions, so as to gain a critical appraisal of their validity.The results obtained show that the specular reflectance of chromite depends on composition and can be used to estimate compositional parameters, as #Cr = Cr/(Cr + Al) or #Mg = Mg/(Mg + Fe2+), but this relationship is complex and does not allow simple direct determinations, due to the multiplicity of possible changes and coupled substitutions (e.g. Al–Cr–Fe3+, or Mg-Fe2+, Ni, Zn, Ti …) in the chromian spinel family. On the other hand, the relationship of chromite composition with deposit type is also detectable through the reflectance values, but with a higher uncertainty. Reflectance increases with increasing Cr and Fe3+ contents in all cases, but the relationship of reflectance with Mg seems to be specific of the deposit type: while reflectance increases with increasing #Mg in the Ojén chromites, it shows the opposite behaviour in podiform chromites. Although these results should be regarded as preliminary until further studies on larger sample populations can be achieved, they are suggestive of possible practical applications for exploration, e. g. to approach Cr-spinel compositions or chromite deposit typology, early in an exploration campaign, by inexpensive reflected light determination of specular reflectance in a few samples. 相似文献
276.
月表光度行为描述了月表物质反射的太阳光随入射、出射和太阳相角的变化,其反射率的不同取决于月壤颗粒大小、粒子形状、透明度、孔隙度、表面粗糙度等因素。为了分析月表光度行为,了解区域反射率差异原因,本文以Apollo16登月区为例,使用M3(moon mineralogy mapper)数据反演Hapke模型物理参数,并分析了Hapke模型光度参数对二向性反射率的影响程度。反演结果显示,本文研究区域光度参数b、hS变化很小,光度参数w有一定的变化;表明本文研究区域反射率不同主要是w的差异造成的。研究区域月壤中各类矿物颗粒的前向散射占主导地位,月壤结构和粒径总体相近,但在孔隙度、风化层填充物状态及表面粗糙度等因素中至少有一种因素存在差异。 相似文献
277.
下古生界缺失高等植物来源的镜质组,其有机质成熟度的确定一直是油气源岩评价的难题之一。基于对含笔石页岩的反射光显微镜观察和低成熟度含笔石页岩与煤共置的热压模拟实验,研究了下古生界海相页岩笔石表皮体的光性特征及其热演化规律,探讨了笔石表皮体随机反射率作为有机质热演化参数的可行性。下古生界海相页岩非粒状笔石表皮体呈条带状顺层或者碎片状产出、颗粒较大,光学特征类似于镜质组,适合于测量反射率。非粒状笔石表皮体随机反射率■换算为等效镜质组反射率■的关系式为■。采用笔石表皮体随机反射率分析了上扬子地区东部五峰组—龙马溪组页岩的有机质成熟度分布特征,认为非粒状笔石表皮体随机反射率是一个实用的下古生界烃源岩有机质成熟度指标,为确定下古生界有机质成熟度提供了一种可信的解决方案。 相似文献
278.
As a kind of important biogenic organic matter, amino sugars can effectively provide insights for the source of organic matters and the contribution of bacterial organic matters based on their concentrations and compositions in the environment. A large number of studies on the analysis of amino sugars have been conducted for environmental samples throughout the world. However, comprehensive and systematic reviews of new progress on the analytical method are still rare. From the aspects of pretreatment methods and detection techniques, the advantages and disadvantages and applicable conditions of three common methods (eg. gas chromatography, high performance liquid chromatography and infrared spectroscopy) were systematically summarized. In terms of pretreatment, the process of the gas chromatography is cumbersome and requires derivatization, while the pretreatment of high performance liquid chromatography is relatively simple and easier to automate. In respect of instrument detection, the gas chromatography can detect four amino sugars (glucosamine, galactosamine, mannosamine and muramic acid) simultaneously and is more stable than the high performance liquid chromatography. In addition, the infrared spectroscopy method has the advantages of structural qualitative, however, its sensitivity is lower. There is no analytical method that can guarantee both sensitive analysis of amino sugars and experimental efficiency. Therefore, the analytical method should be reasonably selected according to the form of the sample and the requirements in the analysis of amino sugars. Further work should focus on economy, compatibility and online automation of analytical methods, so as to provide technical support for the research on biogeochemical processes of amino sugars in the environment. 相似文献
279.
Stratabound epigenetic dolomite occurs in carbonate facies of the Barrandian basin (Silurian and Devonian), Czech Republic.
The most intense dolomitization is developed in bioclastic calcarenites within the transition between micritic limestone and
shaledominated Přídolí and Lochkov formations deposited on a carbonate slope. Medium-crystalline (100–400 μm), inclusion-rich,
xenotopic matrix dolomite (δ
18O=−4.64 to −3.40‰ PDB;δ
13C=+1.05 to +1.85‰ PDB) which selectively replaced most of the bioclastic precursor is volumetrically the most important dolomite
type. Coarse crystalline saddle dolomite (δ
18O=−8.04 to −5.14‰ PDB;δ
18C=+0.49 to +1.49 PDB) which precipitated in fractures and vugs within the matrix dolomite represents a later diagenetic dolomitization
event. In some vugs, saddle dolomite coprecipitated with petroleum inclusion-rich authigenic quartz crystals and minor sulfides
which, in turn, were post-dated by semisolid asphaltic bitumen. The interpretation of the dolomitization remains equivocal.
Massive xenotopic dolomite, although generally characteristic of a deeper burial setting, may have been formed by a recrystallization
of an earlier, possibly shallow burial dolomite. Deeper burial recrystallization by reactive basinal pore fluids that presumably
migrated through the more permeable upper portion of the Přídolí sequence appears as a viable explanation for this dolomitization
overprint. Saddle dolomite cement of the matrix dolomite is interpreted as the last dolomitization event that occurred during
deep burial at the depth of the oil window zone. The presence of saddle dolomite, the fluid inclusion composition of associated
quartz crystals, and vitrinite paleogeothermometry of adjacent sediments imply diagenetic burial temperatures as high as 160°C.
Although high geothermal gradients in the past or the involvement of hydrothermally influenced basinal fluids can account
for these elevated temperatures, burial heating beneath approximately 3-km-thick sedimentary overburden of presumably post-Givetian
strata, no longer preserved in the basin, appears to be the most likely interpretation. This interpretaion may imply that
the magnitude of post-Variscan erosion in the Barrandian area was substantially greater than previously thought. 相似文献
280.
HY-3型全自动显微光度测定系统为煤、焦、中间相、矿物等反射率提供了自动测定工具。本文介绍了其中采用的技术措施与反射率自动测定过程中采用的技术方法。 相似文献