全文获取类型
收费全文 | 1705篇 |
免费 | 40篇 |
国内免费 | 23篇 |
专业分类
测绘学 | 55篇 |
大气科学 | 167篇 |
地球物理 | 292篇 |
地质学 | 650篇 |
海洋学 | 126篇 |
天文学 | 331篇 |
综合类 | 11篇 |
自然地理 | 136篇 |
出版年
2023年 | 9篇 |
2021年 | 17篇 |
2020年 | 18篇 |
2019年 | 18篇 |
2018年 | 34篇 |
2017年 | 29篇 |
2016年 | 41篇 |
2015年 | 25篇 |
2014年 | 44篇 |
2013年 | 73篇 |
2012年 | 55篇 |
2011年 | 82篇 |
2010年 | 78篇 |
2009年 | 127篇 |
2008年 | 79篇 |
2007年 | 101篇 |
2006年 | 84篇 |
2005年 | 100篇 |
2004年 | 57篇 |
2003年 | 50篇 |
2002年 | 56篇 |
2001年 | 44篇 |
2000年 | 43篇 |
1999年 | 33篇 |
1998年 | 31篇 |
1997年 | 26篇 |
1996年 | 20篇 |
1995年 | 25篇 |
1994年 | 25篇 |
1993年 | 16篇 |
1992年 | 15篇 |
1991年 | 14篇 |
1990年 | 14篇 |
1988年 | 13篇 |
1987年 | 9篇 |
1986年 | 11篇 |
1985年 | 16篇 |
1984年 | 13篇 |
1983年 | 22篇 |
1982年 | 16篇 |
1981年 | 15篇 |
1980年 | 13篇 |
1979年 | 10篇 |
1978年 | 9篇 |
1976年 | 17篇 |
1975年 | 10篇 |
1973年 | 17篇 |
1972年 | 15篇 |
1971年 | 11篇 |
1970年 | 9篇 |
排序方式: 共有1768条查询结果,搜索用时 15 毫秒
411.
Assessment of Nanosecond Laser Ablation Multi‐Collector Inductively Coupled Plasma‐Mass Spectrometry for Pb and Sr Isotopic Determination in Archaeological Glass: Mass Bias Correction Strategies and Results for Corning Glass Reference Materials 下载免费PDF全文
Alicia Van Ham‐Meert Stepan M. Chernonozhkin Stijn J.M. Van Malderen Thibaut Van Acker Frank Vanhaecke Patrick Degryse 《Geostandards and Geoanalytical Research》2018,42(2):223-238
This work presents an evaluation of various methods for in situ high‐precision Sr and Pb isotopic determination in archaeological glass (containing 100–500 μg g?1 target element) by nanosecond laser ablation multi‐collector‐inductively coupled plasma‐mass spectrometry (ns‐LA‐MC‐ICP‐MS). A set of four soda‐lime silicate glasses, Corning A–D, mimicking the composition of archaeological glass and produced by the Corning Museum of Glass (Corning, New York, USA), were investigated as candidates for matrix‐matched reference materials for use in the analysis of archaeological glass. Common geological reference materials with known isotopic compositions (USGS basalt glasses BHVO‐2G, GSE‐1G and NKT‐1G, soda‐lime silicate glass NIST SRM 610 and several archaeological glass samples with known Sr isotopic composition) were used to evaluate the ns‐LA‐MC‐ICP‐MS analytical procedures. When available, ns‐LA‐MC‐ICP‐MS results for the Corning glasses are reported. These were found to be in good agreement with results obtained via pneumatic nebulisation (pn) MC‐ICP‐MS after digestion of the glass matrix and target element isolation. The presence of potential spectral interference from doubly charged rare earth element (REE) ions affecting Sr isotopic determination was investigated by admixing Er and Yb aerosols by means of pneumatic nebulisation into the gas flow from the laser ablation system. It was shown that doubly charged REE ions affect the Sr isotope ratios, but that this could be circumvented by operating the instrument at higher mass resolution. Multiple strategies to correct for instrumental mass discrimination in ns‐LA‐MC‐ICP‐MS and the effects of relevant interferences were evaluated. Application of common glass reference materials with basaltic matrices for correction of ns‐LA‐MC‐ICP‐MS isotope data of archaeological glasses results in inaccurate Pb isotope ratios, rendering application of matrix‐matched reference materials indispensable. Correction for instrumental mass discrimination using the exponential law, with the application of Tl as an internal isotopic standard element introduced by pneumatic nebulisation and Corning D as bracketing isotopic calibrator, provided the most accurate results for Pb isotope ratio measurements in archaeological glass. Mass bias correction relying on the power law, combined with intra‐element internal correction, assuming a constant 88Sr/86Sr ratio, yielded the most accurate results for 87Sr/86Sr determination in archaeological glasses 相似文献
412.
Determination of In and Sn Mass Fractions in Sixteen Geological Reference Materials by Isotope Dilution MC‐ICP‐MS 下载免费PDF全文
Maria Kirchenbaur Alexander Heuser Alessandro Bragagni Frank Wombacher 《Geostandards and Geoanalytical Research》2018,42(3):361-377
Mass fractions of Sn and In were determined in sixteen geological reference materials including basaltic/mafic (BCR‐2, BE‐N, BHVO‐1, BHVO‐2, BIR‐1, OKUM, W‐2, WS‐E), ultramafic (DTS‐2b, MUH‐1, PCC‐1, UB‐N) and felsic/sedimentary reference materials (AGV‐2, JA‐1, SdAR‐M2, SdAR‐H1). Extensive digestion and ion exchange separation tests were carried out in order to provide high yields (> 90% for Sn, > 85% for In), low total procedural blanks (~ 1 ng for Sn, < 3 pg for In) and low analytical uncertainties for the elements of interest in a variety of silicate sample matrices. Replicate analyses (n = 2–13) of Sn–In mass fractions gave combined measurement uncertainties (2u) that were generally < 3% and in agreement with literature data, where available. We present the first high‐precision In data for reference materials OKUM (32.1 ± 1.5 ng g?1), DTS‐2b (2.03 ± 0.25 ng g?1), MUH‐1 (6.44 ± 0.30 ng g?1) and PCC‐1 (3.55 ± 0.35 ng g?1) as well as the first Sn data for MUH‐1 (0.057 ± 0.010 μg g?1) and DTS‐2b (0.623 ± 0.018 μg g?1). 相似文献
413.
Dr. Frank Scherbaum 《International Journal of Earth Sciences》1982,71(2):519-536
Seismic velocities from the environment of a saltdome on the Pompeckj-Swell were analysed in order to estimate the rates of subsidence and uplift. It is shown using geological data that no true movements of the demanded amount can be proved in the study area. The apparent uplifts estimated from velocity analysis can be interpreted as a result of the ice load during the Pleistocene together with compression caused by the salt.
Zusammenfassung Für die Umgebung eines Salzstocks auf der Pompeckjschen Scholle werden mit Hilfe der seismischen Geschwindigkeiten die Beträge der scheinbaren Hebungen und Absenkungen ermittelt. Die Untersuchung der Sedimentationsverhältnisse im gleichen Gebiet ergibt jedoch keinen Hinweis auf tatsächliche Bewegungen in der geforderten Größenordnung. Die scheinbaren Hebungen lassen sich vielmehr als Folge der Druckbeanspruchung durch das Salz und den Einfluß des pleistozänen Inlandeises deuten.
Résumé Les vitesses sismiques ont été analysées dans les environs d'un diapir situé sur le seuil de Pompeckj pour estimer l'ampleur des soulèvements et des affaissements apparents. L'étude des rapports sédimentaires ne montre aucun signe de mouvements réels dans la région étudiée. Les soulèvements apparents s'expliquent beaucoup mieux comme le résultat commun d'une déformation due à la calotte glaciaire du Pleistocène et à la compression par le sel.
, . . , .相似文献
414.
415.
Philippe Rentzel Frank Preusser Christine Pümpin Jean-Jacques Wolf 《Swiss Journal of Geoscience》2009,102(3):387-401
Pedological investigations in combination with luminescence dating have been used to reconstruct the genesis and chronology
of a sediment succession at Sierentz, France. The sequence comprises loess and palaeosols on top of gravel attributed to the
High Terrace of River Rhine. According to the dating results, three phases of soil development occurred during different warm
phases of Marine Isotope Stage (MIS) 7 (245–190 ka). Soil development on top of the gravel occurred either during early MIS
7 or during an earlier warm phase, possibly MIS 9. The results imply a minimum age of 250 ka for the formation of the High
Terrace in this part of the Upper Rhine Graben, contrary to previous assumptions that correlated gravel sheet deposition with
MIS 6 (ca. 150 ka). These results and recent findings at other sites suggest that the chronological setting of terrace formation
north of the Alps is much more complex than previously assumed. 相似文献
416.
Trace and minor elements in sphalerite: A LA-ICPMS study 总被引:18,自引:0,他引:18
Nigel J. Cook Cristiana L. Ciobanu Allan Pring William Skinner Leonid Danyushevsky Frank Melcher 《Geochimica et cosmochimica acta》2009,73(16):4761-4791
Sphalerite is an important host mineral for a wide range of minor and trace elements. We have used laser-ablation inductively coupled mass spectroscopy (LA-ICPMS) techniques to investigate the distribution of Ag, As, Bi, Cd, Co, Cu, Fe, Ga, Ge, In, Mn, Mo, Ni, Pb, Sb, Se, Sn and Tl in samples from 26 ore deposits, including specimens with wt.% levels of Mn, Cd, In, Sn and Hg. This technique provides accurate trace element data, confirming that Cd, Co, Ga, Ge, In, Mn, Sn, As and Tl are present in solid solution. The concentrations of most elements vary over several orders of magnitude between deposits and in some cases between single samples from a given deposit. Sphalerite is characterized by a specific range of Cd (typically 0.2-1.0 wt.%) in each deposit. Higher Cd concentrations are rare; spot analyses on samples from skarn at Baisoara (Romania) show up to 13.2 wt.% (Cd2+ ↔ Zn2+ substitution). The LA-ICPMS technique also allows for identification of other elements, notably Pb, Sb and Bi, mostly as micro-inclusions of minerals carrying those elements, and not as solid solution. Silver may occur both as solid solution and as micro-inclusions. Sphalerite can also incorporate minor amounts of As and Se, and possibly Au (e.g., Magura epithermal Au, Romania). Manganese enrichment (up to ∼4 wt.%) does not appear to enhance incorporation of other elements. Sphalerite from Toyoha (Japan) features superimposed zoning. Indium-sphalerite (up to 6.7 wt.% In) coexists with Sn-sphalerite (up to 2.3 wt.%). Indium concentration correlates with Cu, corroborating coupled (Cu+In3+) ↔ 2Zn2+ substitution. Tin, however, correlates with Ag, suggesting (2Ag+Sn4+) ↔ 3Zn2+ coupled substitution. Germanium-bearing sphalerite from Tres Marias (Mexico) contains several hundred ppm Ge, correlating with Fe. We see no evidence of coupled substitution for incorporation of Ge. Accordingly, we postulate that Ge may be present as Ge2+ rather than Ge4+. Trace element concentrations in different deposit types vary because fractionation of a given element into sphalerite is influenced by crystallization temperature, metal source and the amount of sphalerite in the ore. Epithermal and some skarn deposits have higher concentrations of most elements in solid solution. The presence of discrete minerals containing In, Ga, Ge, etc. also contribute to the observed variance in measured concentrations within sphalerite. 相似文献
417.
Kim B. Knight Noriko T. Kita Frank M. Richter Andrew M. Davis John W. Valley 《Geochimica et cosmochimica acta》2009,73(20):6390-5891
Calcium-, aluminum-rich inclusions (CAIs) are often enriched in the heavy isotopes of magnesium and silicon relative to bulk solar system materials. It is likely that these isotopic enrichments resulted from evaporative mass loss of magnesium and silicon from early solar system condensates while they were molten during one or more high-temperature reheating events. Quantitative interpretation of these enrichments requires laboratory determinations of the evaporation kinetics and associated isotopic fractionation effects for these elements. The experimental data for the kinetics of evaporation of magnesium and silicon and the evaporative isotopic fractionation of magnesium is reasonably complete for Type B CAI liquids (Richter F. M., Davis A. M., Ebel D. S., and Hashimoto A. (2002) Elemental and isotopic fractionation of Type B CAIs: experiments, theoretical considerations, and constraints on their thermal evolution. Geochim. Cosmochim. Acta66, 521-540; Richter F. M., Janney P. E., Mendybaev R. A., Davis A. M., and Wadhwa M. (2007a) Elemental and isotopic fractionation of Type B CAI-like liquids by evaporation. Geochim. Cosmochim. Acta71, 5544-5564.). However, the isotopic fractionation factor for silicon evaporating from such liquids has not been as extensively studied. Here we report new ion microprobe silicon isotopic measurements of residual glass from partial evaporation of Type B CAI liquids into vacuum. The silicon isotopic fractionation is reported as a kinetic fractionation factor, αSi, corresponding to the ratio of the silicon isotopic composition of the evaporation flux to that of the residual silicate liquid. For CAI-like melts, we find that αSi = 0.98985 ± 0.00044 (2σ) for 29Si/28Si with no resolvable variation with temperature over the temperature range of the experiments, 1600-1900 °C. This value is different from what has been reported for evaporation of liquid Mg2SiO4 (Davis A. M., Hashimoto A., Clayton R. N., and Mayeda T. K. (1990) Isotope mass fractionation during evaporation of Mg2SiO4. Nature347, 655-658.) and of a melt with CI chondritic proportions of the major elements (Wang J., Davis A. M., Clayton R. N., Mayeda T. K., and Hashimoto A. (2001) Chemical and isotopic fractionation during the evaporation of the FeO-MgO-SiO2-CaO-Al2O3-TiO2-REE melt system. Geochim. Cosmochim. Acta65, 479-494.). There appears to be some compositional control on αSi, whereas no compositional effects have been reported for αMg. We use the values of αSi and αMg, to calculate the chemical compositions of the unevaporated precursors of a number of isotopically fractionated CAIs from CV chondrites whose chemical compositions and magnesium and silicon isotopic compositions have been previously measured. 相似文献
418.
Alan N. Buckley Siew Wei Goh William M. Skinner Ronald Woods Liang-Jen Fan 《International Journal of Mineral Processing》2009,93(2):155-164
The interaction of freshly abraded surfaces of cuprite, Cu2O, with neutral or mildly alkaline aqueous solutions of diethyl or di-n-butyl dithiophosphate (DTP) has been investigated by means of conventional and synchrotron X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy. It was confirmed that DTP adsorbs readily on Cu atoms in the surface layer of the mineral treated with solutions of the collector at pH values near 7 and 9 in the presence of air, and renders the surface hydrophobic. When cuprite is treated with relatively high concentrations of DTP for sufficiently long periods, collector can also be adsorbed as CuDTP, but the coverage does not exceed a thin layer of CuDTP on the adsorbed DTP monolayer, unlike the situation with Cu metal or chalcocite where a thick multilayer can be formed. 相似文献
419.
420.
末次盛冰期和全新世大暖期中国北方沙地气候定量重建初探 总被引:1,自引:0,他引:1
中国北方典型沙地处于东亚季风边缘区半干旱气候带,对气候变化响应敏感.本文对已有的该区域古气候记录文献资料进行整理分析和评估,对末次盛冰期与全新世大暖期两个特征时间段的古温度与古降雨量空间格局进行定量化重建,获得了其分布特征.结果表明,在末次盛冰期(约26 ~ 16ka)温度降低了5~11℃,变率为60%~200%,降温极值在黄土高原南缘;降雨量减少180 ~ 350mm,变率为50%左右,东北地区降雨量变化不大.在全新世大暖期(约9 ~ 5ka),温度升高了1.0 ~3.5℃,变率为20%~130%;降雨量增加了30 ~ 400mm,变率为10% ~120%,其中存在一些需剔除的奇异点,从东部沿海向西北内陆降雨量增幅有加大趋势.上述结果为进一步探讨中国北方干旱-半干旱区古气候变化机理、检验东亚季风区古气候数值模拟结果等提供了定量化数据. 相似文献