全文获取类型
收费全文 | 344篇 |
免费 | 16篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 17篇 |
大气科学 | 37篇 |
地球物理 | 72篇 |
地质学 | 148篇 |
海洋学 | 15篇 |
天文学 | 44篇 |
综合类 | 3篇 |
自然地理 | 26篇 |
出版年
2022年 | 3篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 8篇 |
2016年 | 7篇 |
2015年 | 6篇 |
2014年 | 12篇 |
2013年 | 16篇 |
2012年 | 12篇 |
2011年 | 15篇 |
2010年 | 21篇 |
2009年 | 14篇 |
2008年 | 11篇 |
2007年 | 9篇 |
2006年 | 12篇 |
2005年 | 7篇 |
2004年 | 13篇 |
2003年 | 13篇 |
2002年 | 8篇 |
2001年 | 9篇 |
2000年 | 3篇 |
1999年 | 8篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 7篇 |
1974年 | 3篇 |
1972年 | 2篇 |
1968年 | 5篇 |
1967年 | 2篇 |
1966年 | 3篇 |
1964年 | 2篇 |
1937年 | 2篇 |
排序方式: 共有362条查询结果,搜索用时 15 毫秒
211.
212.
International climate negotiations that aim at reducing global greenhouse gas emissions are strongly influenced by a conflict between rich and poor countries and by a lack of consensus about the urgency of emission reduction measures. We have previously in an experimental game characterised the implied challenge of avoiding dangerous climate change as the “collective-risk social dilemma”. Here we introduce heterogeneous wealth and two time horizons into the collective-risk social dilemma game. We show that rich players are willing to substitute for missing contributions by the poor, provided the players collectively face intermediate climate targets that, if not reached, are potentially followed by simulated intermediate costly climate risks. However, despite some increase in the contributions of the rich against the final collective target, the final target is reached less often than the intermediate target. Our results provide experimental evidence that similar, intermediate time horizons between climate risks and climate change mitigation planning are a necessary, though not sufficient, component of successful climate negotiations. 相似文献
213.
John Barrett Glen Peters Thomas Wiedmann Kate Scott Manfred Lenzen Katy Roelich 《Climate Policy》2013,13(4):451-470
Global GHG emissions continue to rise, with nearly a quarter of it due to trade that is not currently captured within global climate policy. In the context of current trade patterns and limited global cooperation on climate change, the feasibility of consumption-based emissions accounting to contribute to a more comprehensive (national) policy framework in the UK is investigated. Consumption-based emissions results for the UK from a range of models are presented, their technical robustness is assessed, and their potential application in national climate policy is examined using examples of policies designed to reduce carbon leakage and to address high levels of consumption. It is shown that there is a need to include consumption-based emissions as a complementary indicator to the current approach of measuring territorial emissions. Methods are shown to be robust enough to measure progress on climate change and develop and inform mitigation policy. Finally, some suggestions are made for future policy-oriented research in the area of consumption-based accounting that will facilitate its application to policy. Policy relevance Emissions embodied in trade are rapidly increasing and there is thus a growing gap between production emissions and the emissions associated with consumption. This is a growing concern due to the absence of a global cap and significant variation in country-level mitigation ambitions. Robust measurements of consumption-based emissions are possible and provide new insights into policy options. This includes trade-related policy (e.g. border carbon adjustments) and domestic policies (e.g. resource efficiency strategies). As climate policy targets deepen, there is a need for a broad range of policy options in addition to production and technological solutions. Consumption-based emissions are complementary to production-based emissions inventories, which are still the most accurate estimate for aggregated emissions at the global level. However, without consumption-based approaches, territorial emissions alone will not provide a complete picture of progress in regional and national emissions reduction. 相似文献
214.
Manfred Wildner Gerald Giester Monika Kersten Klaus Langer 《Physics and Chemistry of Minerals》2014,41(9):669-680
Polarized electronic absorption spectra of colourless chalcocyanite, CuSO4, have been measured using microscope-spectrometric techniques. The spectra are characterized by a structured and clearly polarized band system in the near-infrared spectral range with components centred at 11,720, 10,545, 9,100, and 7,320 cm?1, which have been assigned to crystal field d–d transitions of Cu2+ cations in pseudo-tetragonally elongated CuO6 polyhedra with point symmetry C i ( \(\bar{1}\) ). The polarization behaviour is interpreted based on a D 2(C 2″) pseudo-symmetry. Crystal field calculations were performed for the actual triclinic point symmetry by applying the Superposition Model of crystal fields, as well as in terms of a ‘classic’ pseudo-tetragonal crystal field approach yielding the parameters Dq (eq) = 910, Dt = 395, and Ds = 1,336 cm?1, corresponding to a cubically averaged Dq cub = 679 cm?1. A comparative survey on crystal fields in Cu2+ minerals shows that the low overall crystal field strength in chalcocyanite, combined with a comparatively weak pseudo-tetragonal splitting of energy levels, is responsible for its unique colourless appearance among oxygen-based Cu2+ minerals. The weak crystal field in CuSO4 can be related to the lower position of the SO4 2? anion compared to, e.g. the H2O molecule in the spectrochemical series of ligands. 相似文献
215.
216.
Ralf Hetzel Mingxin Tao Samuel Niedermann Manfred R. Strecker Susan Ivy-Ochs Peter W. Kubik Bo Gao 《地学学报》2004,16(3):157-162
A fault scaling law suggests that, over eight orders of magnitude, fault length L is linearly related to maximum displacement D. Individual faults may therefore retain a constant ratio of D/L as they grow. If erosion is minor compared with tectonic uplift, the length and along‐strike relief of young mountain ranges should thus reflect fault growth. Topographic profiles along the crests of mountain ranges in the actively deforming foreland of north‐east Tibet exhibit a characteristic shape with maximum height near their centre and decreasing elevation toward the tips. We interpret the along‐strike relief of these ranges to reflect the slip distribution on high‐angle reverse faults. A geometric model illustrates that the lateral propagation rate of such mountain ranges may be deciphered if their length‐to‐height ratio has remained constant. As an application of the model, we reconstruct the growth of the Heli Shan using a long‐term uplift rate of ~1.3 mm yr?1 derived from 21Ne and 10Be exposure dating. 相似文献
217.
Manfred P. Leubner 《Astrophysics and Space Science》2002,282(3):573-579
Most astrophysical plasmas are observed to have velocity distribution functions exhibiting non-Maxwellian suprathermal tails.
The high energy particle populations are accurately represented by the family of kappa-distributions where the use of these
distributions has been unjustly criticized because of a perceived lack of theoretical justification. We show that distributions
very close to kappa-distributions are a consequence of the generalized entropy favored by non extensive statistics, which
provides the missing link for power-law models of non-thermal features from fundamental physics. With regard to the physical
basis supplied by the Tsallis nonextensive entropy formalism we propose that this slightly modified functional form, qualitatively
similar to the traditional kappa-distribution, be used in fitting particle spectra in the future. 相似文献
218.
219.
Manfred A. F. Thiel 《Astrophysics and Space Science》1972,17(1):39-47
The distribution of the main axes of double radio sources is used to test isotropy of that part of the universe which is accessible to radio investigations. Data for 274 double and/or extended sources have been taken from the literature to compute the fit to several simple models of global orientation by means of a 2-test. The best fit has been found on a 3%-significance level for the preferred orientation along a right-handed helix with pitch angle 82° in the direction =95°, =–38° (165°,b=20°). This preferential alignment of radio sources is assumed to be caused by a largescale magnetic field. 相似文献
220.
n-Pentadecane was photo-oxidized, as a surface film, on purified natural seawater under simulated environmental conditions with anthraquinone as sensitizer. Initial attack by hydrogen abstraction from carbon atoms within the chain is followed by reaction of the alkyl radicals thus generated with molecular oxygen. The stable reaction products identified by GC-MS strongly suggest that alkoxy radicals produced by cleavage of the peroxide bond are key intermediates in the decomposition of the original alkane. The alkoxy radicals stabilize themselves either as ketones by reaction with molecular oxygen which is transformed into HO2 or, if μ-hydrogen atoms are available, by cyclic electron rearrangements similar to a Norrish type II photo-decomposition. The products of the electron rearrangements are 1-alkenes and daughter alkoxy radicals. The latter either yield methyl ketones and HO2 radicals upon reaction with molecular oxygen or undergo further decomposition as long as γ-hydrogen atoms are available. The generation of acetone and HO2 radicals, inferred by the proposed reaction mechanism as products of many such degradation sequences, offers a plausible explanation for their occurrence in seawater in addition to those already advanced. 相似文献