全文获取类型
收费全文 | 1021篇 |
免费 | 30篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 55篇 |
大气科学 | 154篇 |
地球物理 | 200篇 |
地质学 | 416篇 |
海洋学 | 61篇 |
天文学 | 137篇 |
综合类 | 1篇 |
自然地理 | 32篇 |
出版年
2021年 | 12篇 |
2018年 | 20篇 |
2017年 | 20篇 |
2016年 | 34篇 |
2015年 | 21篇 |
2014年 | 37篇 |
2013年 | 49篇 |
2012年 | 35篇 |
2011年 | 38篇 |
2010年 | 40篇 |
2009年 | 43篇 |
2008年 | 31篇 |
2007年 | 46篇 |
2006年 | 28篇 |
2005年 | 30篇 |
2004年 | 20篇 |
2003年 | 25篇 |
2002年 | 34篇 |
2001年 | 23篇 |
2000年 | 13篇 |
1999年 | 20篇 |
1998年 | 9篇 |
1997年 | 20篇 |
1996年 | 11篇 |
1995年 | 24篇 |
1994年 | 13篇 |
1993年 | 10篇 |
1991年 | 21篇 |
1990年 | 11篇 |
1989年 | 10篇 |
1987年 | 13篇 |
1986年 | 7篇 |
1985年 | 11篇 |
1984年 | 10篇 |
1983年 | 15篇 |
1981年 | 14篇 |
1980年 | 12篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1976年 | 13篇 |
1975年 | 8篇 |
1974年 | 7篇 |
1972年 | 7篇 |
1971年 | 7篇 |
1965年 | 7篇 |
1960年 | 9篇 |
1955年 | 8篇 |
1952年 | 11篇 |
1951年 | 8篇 |
排序方式: 共有1056条查询结果,搜索用时 187 毫秒
201.
202.
The development of biorefineries is the key for access to an integrated production of food, feed, chemicals, materials, goods, fuels and energy of the future. This communication considers an integrated green biorefinery combined with today's production of feed in the green agriculture. Special attention is given to the combination of physical and biotechnological processes for the production of proteins as well as platform chemicals such as lactic acid and lysine. Mass and energy flows (steam and electricity) are given for the biorefining of green biomass to produce platform chemicals, proteins, feed and biogas from residues. 相似文献
203.
Methane exchange between coal-bearing basins and the atmosphere: the Ruhr Basin and the Lower Rhine Embayment, Germany 总被引:1,自引:0,他引:1
Thomas Thielemann Andreas Lücke Gerhard H. Schleser Ralf Littke 《Organic Geochemistry》2000,31(12):121
A precise knowledge of methane exchange processes is required to fully understand the recent rise of atmospheric methane concentration. Three of these processes take place at the lithosphere/atmosphere boundary: bacterial consumption of methane and emission of bacterial or thermogenic methane. This study was initiated to quantify these processes on a regional scale in the Ruhr Basin and the Lower Rhine Embayment. Since these areas are subject to bituminous coal and lignite mining, natural and anthropogenically-induced methane exchange processes could be studied. The methane emission and consumption rates and their carbon isotope signal were measured at the lithosphere/atmosphere boundary using flux chambers. On most of the soils studied, methane consumption by bacteria was identified. Thermogenic methane was released only at some of the natural faults examined. In active and abandoned bituminous coal mining areas methane emissions were restricted to small areas, where high emission rates were measured. The carbon isotope composition of methane at natural faults and in mining subsidence troughs was typical of thermogenic methane (−45 to −32 ‰ δ13C). Methane exchange balancing revealed that natural methane emissions from these two basins represent no source of atmospheric importance. However, methane release by upcast mining shafts dominates the methane exchange processes and is by about two orders of magnitude greater than methane consumption by bacterial oxidation in the soils. 相似文献
204.
Klaus Schäfer 《GeoJournal》2000,52(1):45-58
The article describes a new form of transnational environmental conflict that developed in the wake of globalisation. Activist in this new type of conflict still act as proxies of groups under pressure but in contrast to transnational environmental conflicts hitherto the target of their protests is rather their own society at home than the location of the pressured group. Despite these conditions it is claimed that this type of metaphorical conflict is going to become more frequent as alliances are built along the oppostion to a dominant discourse. According to the model, conflicts of values are easier to transfer on stages abroad or across the Atlantic than conflicts of interests and motivation for activists is higher as the return is affecting their home society. Dynamic and features of this type of conflict are explained with help of discourse theory. 相似文献
205.
206.
Friedrich Lucassen Peter Dulski Rainer Abart Gerhard Franz Dieter Rhede Rolf L. Romer 《Contributions to Mineralogy and Petrology》2010,160(2):279-295
Titanite growth at the expense of rutile during retrograde hydration of eclogite into amphibolite is a common phenomenon. We investigated an amphibolite sample from the Tromsø eclogite facies terrain in Northern Norway to gain insight into the trace element distribution between rutile and titanite during incomplete resorption of the rutile by titanite. Patchy compositional zoning of Al, Ti, and F in titanite relates to the presence of a fluid with variable Ti/Al and/or F during its growth. Laser ablation ICP–MS and electron microprobe data for high field strength elements (HFSE: Nb, Zr, Ta, and Hf) of rutile resorbed by titanite indicate a pronounced enrichment of these elements in the rim of a large single rutile crystal (~8 mm) and a systematic decrease towards uniform HFSE contents in the large core. HFSE contents of smaller rutile grains (~0.5 mm) and rutile inclusions (<100 μm) in the titanite overgrowth are similar or higher than in the rims of large rutile crystals. Element profiles from the rim inward demonstrate that HFSE enrichment in rutile is controlled by diffusion. HFSE ratios in diffusion-altered rutile show systematic variations compared with the uniform core composition of the large rutile. Modelling of Zr and Nb diffusion in rutile indicates that diffusion coefficients in rutile in fluid-dominated natural systems must be considerably higher than those determined experimentally at 1 bar in dry systems. Variations of HFSE contents in the newly formed titanite show no systematic spatial distribution. HFSE ratios in titanite and the rims of rutile are different, indicating different solid/fluid distribution coefficients in these minerals. Element fractionation by diffusion into the relict rutile and during fluid-mediated growth of new titanite could substantially change the HFSE budget of these minerals and could affect their use for geochemical tracing and other applications, such as Zr-based geothermobarometry. 相似文献
207.
Friedrich Lucassen Gerhard Franz Rolf L. Romer Frank Schultz Peter Dulski Klaus Wemmer 《Lithos》2007,99(3-4):312-338
Sr–Nd–Pb isotope ratios of alkaline mafic intra-plate magmatism constrain the isotopic compositions of the lithospheric mantle along what is now the eastern foreland or back arc of the Cenozoic Central Andes (17–34°S). Most small-volume basanite volcanic rocks and alkaline intrusive rocks of Cretaceous (and rare Miocene) age were derived from a depleted lithospheric mantle source with rather uniform initial 143Nd/144Nd ( 0.5127–0.5128) and 87Sr/86Sr ( 0.7032–0.7040). The initial 206Pb/204Pb ratios are variable (18.5–19.7) at uniform 207Pb/204Pb ratios (15.60 ± 0.05). A variety of the Cretaceous depleted mantle source of the magmatic rocks shows elevated Sr isotope ratios up to 0.707 at constant high Nd isotope ratios. The variable Sr and Pb isotope ratios are probably due to radiogenic growth in a metasomatized lithospheric mantle, which represents the former sub-arc mantle beneath the early Palaeozoic active continental margin. Sr–Nd–Pb isotope signatures of a second mantle type reflected in the composition of Cretaceous (one late Palaeozoic age) intra-plate magmatic rocks (143Nd/144Nd 0.5123, 87Sr/86Sr 0.704, 206Pb/204Pb 17.5–18.5, and 207Pb/204Pb 15.45–15.50) are similar to the isotopic composition of old sub-continental lithospheric mantle of the Brazilian Shield.
Published Nd and Sr isotopic compositions of Mesozoic to Cenozoic arc-related magmatic rocks (18–40°S) represent the composition of the convective sub-arc mantle in the Central Andes and are similar to those of the Cretaceous (and rare Miocene) intra-plate magmatic rocks. The dominant convective and lithospheric mantle type beneath this old continental margin is depleted mantle, which is compositionally different from average MORB-type depleted mantle. The old sub-continental lithospheric mantle did not contribute to Mesozoic to Cenozoic arc magmatism. 相似文献
208.
Wafa Abouchami Stephen J. G. Galer Tristan J. Horner Mark Rehkämper Frank Wombacher Zichen Xue Myriam Lambelet Melanie Gault‐Ringold Claudine H. Stirling Maria Schönbächler Alyssa E. Shiel Dominique Weis Philip F. Holdship 《Geostandards and Geoanalytical Research》2013,37(1):5-17
Research into natural mass‐dependent stable isotope fractionation of cadmium has rapidly expanded in the past few years. Methodologies are diverse with MC‐ICP‐MS favoured by all but one laboratory, which uses thermal ionisation mass spectrometry (TIMS). To quantify the isotope fractionation and correct for instrumental mass bias, double‐spike techniques, sample‐calibrator bracketing or element doping has been used. However, easy comparison between data sets has been hampered by the multitude of in‐house Cd solutions used as zero‐delta reference in different laboratories. The lack of a suitable isotopic reference material for Cd is detrimental for progress in the long term. We have conducted a comprehensive round‐robin assay of NIST SRM 3108 and the Cd isotope offsets to commonly used in‐house reference materials. Here, we advocate NIST SRM 3108 both as an isotope standard and the isotopic reference point for Cd and encourage its use as ‘zero‐delta’ in future studies. The purity of NIST SRM 3108 was evaluated regarding isobaric and polyatomic molecular interferences, and the levels of Zn, Pd and Sn found were not significant. The isotope ratio 114Cd/110Cd for NIST SRM 3108 lies within ~ 10 ppm Da?1 of best estimates for the Bulk Silicate Earth and is validated for all measurement technologies currently in use. 相似文献
209.
In order to evaluate the Holocene palaeoenvironmental evolution of the Ugii Nuur basin, central Mongolia, investigations on chemical and mineralogical properties of lacustrine sediments were carried out on a 630 cm sediment core from lake Ugii Nuur. The interpretation of the record is based on a principal component analysis (PCA) of the elemental composition of the samples. The results show that lacustrine deposition started at 10.6 kyr BP. Low lake level conditions were identified during the Early Holocene (10.6-7.9 kyr BP). The Mid Holocene (7.9-4.2 kyr BP) was characterized by generally higher lake levels and thus higher moisture supply, but it experienced strong climatic fluctuations. Arid conditions prevailed from 4.2-2.8 kyr BP and were followed by a stable, more humid phase until today. 相似文献
210.
J. Steppeler R. Hess U. Schättler L. Bonaventura 《Meteorology and Atmospheric Physics》2003,82(1-4):287-301
Summary ?Currently available computer power allows to run operational numerical weather prediction models at resolutions higher than
10 km. The aim of such high resolution modeling is the prediction of local weather, including orographically induced winds
and local precipitation patterns. In this range the hydrostatic approximation is no longer valid and nonhydrostatic models
have to be used instead. For several decades these models have been developed for research purposes only, but operational
application is now reality. In this paper, the numerical methods used in current nonhydrostatic forecast models will be reviewed
and some promising techniques in this field will be discussed. Special attention is given to aspects such as the choice of
the vertical coordinate, the efficiency of algebraic solvers for semi-implicit time discretizations, and accurate and non-oscillatory
advection schemes.
Received July 6, 2001; revision October 12, 2001 相似文献