全文获取类型
收费全文 | 378篇 |
免费 | 15篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 14篇 |
大气科学 | 51篇 |
地球物理 | 132篇 |
地质学 | 106篇 |
海洋学 | 20篇 |
天文学 | 40篇 |
综合类 | 6篇 |
自然地理 | 25篇 |
出版年
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 7篇 |
2018年 | 6篇 |
2017年 | 11篇 |
2016年 | 9篇 |
2015年 | 9篇 |
2014年 | 15篇 |
2013年 | 19篇 |
2012年 | 22篇 |
2011年 | 16篇 |
2010年 | 18篇 |
2009年 | 19篇 |
2008年 | 16篇 |
2007年 | 13篇 |
2006年 | 13篇 |
2005年 | 13篇 |
2004年 | 8篇 |
2003年 | 8篇 |
2002年 | 5篇 |
2001年 | 13篇 |
2000年 | 13篇 |
1999年 | 4篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1988年 | 5篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1984年 | 4篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1976年 | 3篇 |
1975年 | 5篇 |
1971年 | 2篇 |
1969年 | 2篇 |
1966年 | 2篇 |
1964年 | 2篇 |
1957年 | 2篇 |
1956年 | 3篇 |
1954年 | 4篇 |
1951年 | 2篇 |
排序方式: 共有394条查询结果,搜索用时 15 毫秒
121.
122.
U. Pöschl J. Williams P. Hoor H. Fischer P. J. Crutzen C. Warneke R. Holzinger A. Hansel A. Jordan W. Lindinger H. A. Scheeren W. Peters J. Lelieveld 《Journal of Atmospheric Chemistry》2001,38(2):115-132
Airborne measurements of acetone were performed overthe tropical rainforest in Surinam(2°–7° N, 54°–58° W, 0–12 kmaltitude) during the LBA-CLAIRE campaign in March1998, using a novel proton transfer reaction massspectrometer (PTR-MS) that enables the on-linemonitoring of volatile organic compounds (VOC) with ahigher proton affinity than water. The measuredacetone volume mixing ratios ranged from 0.1 nmol/molup to 8 nmol/mol with an overall average of 2.6nmol/mol and a standard deviation of 1.0 nmol/mol. Theobserved altitude profile and correlations with CO,acetonitrile, propane and wind direction are discussedwith respect to potential acetone sources. No linearcorrelation between acetone and CO mixing ratios wasobserved, at variance with results of previousmeasurement campaigns. The mean acetone/CO ratio(0.022) was substantially higher than typical valuesfound before. The abundance of acetone appears to beinfluenced, but not dominated, by biomass burning,thus suggesting large emissions of acetone and/oracetone precursors, such as possibly 2-propanol, fromliving plants or decaying litter in the rainforest. 相似文献
123.
Horálek J. Šílený J. Fischer T. Slancová A. Boušková A. 《Studia Geophysica et Geodaetica》2000,44(4):491-521
In order to learn more about the nature of the dynamic processes taking place in the West Bohemia/Vogtland earthquake swarm region, we investigated the temporal and spatial variations of the source mechanisms of the January 1997 swarm beneath Nový Kostel (NKC). Visual analyses of WEBNET seismograms of over 800 events revealed that a specific feature of this swarm was the occurrence of eight classes of multiplet events. The result of single-source, absolute moment tensor inversion of the P and SH peak amplitudes of a subset of 70 events representing all multiplet classes indicated that eight statistically significant types of mechanisms occurred during the swarm. Two of them, types
A
and
B
in our denotation, comprised all M
L
1.3 events and predominated in the swarm. Type
A
were pure strike-slip mechanisms or strike-slip mechanisms containing a small normal component, with a nearly pure double-couple source. For class
B
events, oblique-thrust faulting and non-double-couple components significant at a fairly high confidence level were typical. Type
A
events predominated in the southern subcluster of the swarm, whereas most of type
B
events occurred in the subcluster northwards from NKC. This indicates that two major seismogenic planes were active during the swarm. The swarm essentially developed in four phases: in the first, type
A
events prevailed and the southern plane was active; during the second, characterised by the occurrence of both type
A
and
B
events (the former in the southern, the latter predominantly in the northern subcluster), the activity of the swarm culminated; in the third and fourth, the occurrence of type
B
events in the northern plane predominated, and only weak single events occurred southwards from NKC. Mechanisms of types
AB
,
C
,
D
,
E
,
F
and
G
, which were typical for M
L
1.2 events, occurred randomly throughout the swarm. Type
AB
events were identified in both the southern and northern clusters, type
C
,
E
,
F
and
G
mechanisms only southwards from NKC. Type
D
events exhibited a large scatter of hypocentres which fell in neither the southern nor the northern cluster. Focal mechanisms like those reported in this study and with analogous temporal and spatial variations were observed by other authors already fifteen years ago in the 1985/86 earthquake swarm and may, therefore, be typical for the region under study. 相似文献
124.
Raines SN Watson DM Pipher JL Forrest WJ Greenhouse MA Satyapal S Woodward CE Smith HA Fischer J Goetz JA Frank A 《The Astrophysical journal》2000,533(2):L115-L118
When some magnetic field lines connect a Kerr black hole with a disk rotating around it, energy and angular momentum are transferred between them. If the black hole rotates faster than the disk, ca&solm0;GMH>0.36 for a thin Keplerian disk, then energy and angular momentum are extracted from the black hole and transferred to the disk (MH is the mass and aMH is the angular momentum of the black hole). This way, the energy originating in the black hole may be radiated away by the disk. The total amount of energy that can be extracted from the black hole spun down from ca&solm0;GMH=0.998 to ca&solm0;GMH=0.36 by a thin Keplerian disk is approximately 0.15MHc2. This is larger than approximately 0.09MHc2, which can be extracted by the Blandford-Znajek mechanism. 相似文献
125.
气候变化对中国农业生产的影响 总被引:89,自引:1,他引:88
根据1958 ̄1997年中国310个气象站的月平均最高、最低气温,月平均降水量,日照时数等气象参数分析了中国气候的背影特征。用3个大气环流模型,即HadCM2、CGCM1、ECHAM4来模拟未来中国气候变化的情景。同时,建立未来气候变化的6种方案。最后,根据3个GCMs模拟的结果,利用国际应用系统分析研究所(IIASA)发展并改进的农业生态地带模型(AEZ)评估气候变化对中国农业生产的影响。评估主 相似文献
126.
127.
气候变化对中国农业生产的影响 总被引:1,自引:0,他引:1
根据1958~1997年中国310个气象站的月平均最高、最低气温,月平均降水量,日照时数等气象参数分析了中国气候的背景特征.用3个大气环流模型,即HadCM2、CGCM1、ECHAM4来模拟未来中国气候变化的情景.同时,建立未来气候变化的6种方案.最后,根据3个GCMs模拟的结果,利用国际应用系统分析研究所(IIASA)发展并改进的农业生态地带模型(AEZ)评估气候变化对中国农业生产的影响.评估主要集中于气候变化对不同区域复种指数、可耕种土地面积、潜在粮食产量及其土地生产潜力的影响. 相似文献
128.
Benjamin M. C. Fischer Michael Rinderer Philipp Schneider Tracy Ewen Jan Seibert 《水文研究》2015,29(26):5321-5336
Mountainous headwaters consist of different landscape units including forests, meadows and wetlands. In these headwaters it is unclear which landscape units contribute what percentage to baseflow. In this study, we analysed spatiotemporal differences in baseflow isotope and hydrochemistry to identify catchment‐scale runoff contribution. Three baseflow snapshot sampling campaigns were performed in the Swiss pre‐alpine headwater catchment of the Zwäckentobel (4.25 km2) and six of its adjacent subcatchments. The spatial and temporal variability of δ2H, Ca, DOC, AT, pH, SO4, Mg and H4SiO4 of streamflow, groundwater and spring water samples was analysed and related to catchment area and wetland percentage using bivariate and multivariate methods. Our study found that in the six subcatchments, with variable arrangements of landscape units, the inter‐ and intra catchment variability of isotopic and hydrochemical compositions was small and generally not significant. Stream samples were distinctly different from shallow groundwater. An upper spring zone located near the water divide above 1,400 m and a larger wetland were identified by their distinct spatial isotopic and hydrochemical composition. The upstream wetland percentage was not correlated to the hydrochemical streamflow composition, suggesting that wetlands were less connected and act as passive features with a negligible contribution to baseflow runoff. The isotopic and hydrochemical composition of baseflow changed slightly from the upper spring zone towards the subcatchment outlets and corresponded to the signature of deep groundwater. Our results confirm the need and benefits of spatially distributed snapshot sampling to derive process understanding of heterogeneous headwaters during baseflow. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
129.
Adam M. Booth John Dehls Trond Eiken Luzia Fischer Reginald L. Hermanns Thierry Oppikofer 《Landslides》2015,12(4):745-756
130.
In this paper, we compare integrated water vapour (IWV) retrievals from the Moderate Resolution Spectrometer (MODIS) instrument on board the polar-orbiting Terra platform with those from the coupled regional climate model system BALTIMOS for a period of 2 years (October 2001 to October 2003). The comparison was made for the whole drainage basin of the Baltic Sea as well as major parts of Central Europe. The qualitative comparison between the two data sets of the integrated water vapour shows a good agreement. The patterns in the spatial distribution of the averaged integrated water vapour in both data sets are quite similar. However, significant differences occur in the Hungarian Lowlands, along the Po River and the Wallachia (Romania) in the order of 2.5 to 7.0 kg/m2. For these areas, the BALTIMOS model is dryer than the MODIS observations. This could be an indication for the known summer drying effect of BALTIMOS but needs further investigations. The annual cycle as well as a diurnal developing of integrated water vapour from 09:00 to 12:00 UTC is well pronounced in both data sets. For both data sets, the overall annual variations are 17.5 kg/m2. The observed overall diurnal variability are 1.4 kg/m2 for MODIS and 1.04 kg/m2 for BALTIMOS, respectively. 相似文献