全文获取类型
收费全文 | 14809篇 |
免费 | 129篇 |
国内免费 | 85篇 |
专业分类
测绘学 | 341篇 |
大气科学 | 1056篇 |
地球物理 | 2831篇 |
地质学 | 6073篇 |
海洋学 | 1345篇 |
天文学 | 2776篇 |
综合类 | 72篇 |
自然地理 | 529篇 |
出版年
2022年 | 144篇 |
2021年 | 204篇 |
2020年 | 190篇 |
2019年 | 228篇 |
2018年 | 862篇 |
2017年 | 770篇 |
2016年 | 606篇 |
2015年 | 267篇 |
2014年 | 497篇 |
2013年 | 628篇 |
2012年 | 624篇 |
2011年 | 662篇 |
2010年 | 566篇 |
2009年 | 654篇 |
2008年 | 596篇 |
2007年 | 584篇 |
2006年 | 510篇 |
2005年 | 834篇 |
2004年 | 1031篇 |
2003年 | 744篇 |
2002年 | 312篇 |
2001年 | 248篇 |
2000年 | 254篇 |
1999年 | 169篇 |
1998年 | 184篇 |
1997年 | 171篇 |
1996年 | 115篇 |
1995年 | 131篇 |
1994年 | 115篇 |
1993年 | 97篇 |
1992年 | 71篇 |
1991年 | 98篇 |
1990年 | 97篇 |
1989年 | 68篇 |
1988年 | 79篇 |
1987年 | 99篇 |
1986年 | 80篇 |
1985年 | 107篇 |
1984年 | 95篇 |
1983年 | 104篇 |
1982年 | 86篇 |
1981年 | 81篇 |
1980年 | 97篇 |
1979年 | 88篇 |
1978年 | 87篇 |
1977年 | 77篇 |
1976年 | 59篇 |
1975年 | 63篇 |
1974年 | 71篇 |
1973年 | 64篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
891.
C. Vigny J. Chéry T. Duquesnoy F. Jouanne J. Ammann M. Anzidei J.-P. Avouac F. Barlier R. Bayer P. Briole E. Calais F. Cotton F. Duquenne K. L. Feigl G. Ferhat M. Flouzat J.-F. Gamond A. Geiger A. Harmel M. Kasser M. Laplanche M. Le Pape J. Martinod G. Ménard B. Meyer J.-C. Ruegg J.-M. Scheubel O. Scotti G. Vidal 《Journal of Geodesy》2002,76(2):63-76
The Western Alps are among the best studied collisional belts with both detailed structural mapping and also crustal geophysical
investigations such as the ECORS and EGT seismic profile. By contrast, the present-day kinematics of the belt is still largely
unknown due to small relative motions and the insufficient accuracy of the triangulation data. As a consequence, several tectonic
problems still remain to be solved, such as the amount of N–S convergence in the Occidental Alps, the repartition of the deformation
between the Alpine tectonic units, and the relation between deformation and rotation across the Alpine arc. In order to address
these problems, the GPS ALPES group, made up of French, Swiss and Italian research organizations, has achieved the first large-scale
GPS surveys of the Western Alps. More than 60 sites were surveyed in 1993 and 1998 with a minimum observation of 3 days at
each site. GPS data processing has been done by three independent teams using different software. The different solutions
have horizontal repeatabilities (N–E) of 4–7 mm in 1993 and 2–3 mm in 1998 and compare at the 3–5-mm level in position and
2-mm/yr level in velocity. A comparison of 1993 and 1998 coordinates shows that residual velocities of the GPS marks are generally
smaller than 2 mm/yr, precluding a detailed tectonic interpretation of the differential motions. However, these data seem
to suggest that the N–S compression of the Western Alps is quite mild (less than 2 mm/yr) compared to the global convergence
between the African and Eurasian plate (6 mm/yr). This implies that the shortening must be accomodated elsewhere by the deformation
of the Maghrebids and/or by rotations of Mediterranean microplates. Also, E–W velocity components analysis supports the idea
that E–W extension exists, as already suggested by recent structural and seismotectonic data interpretation.
Received: 27 November 2000 / Accepted: 17 September 2001 相似文献
892.
893.
Laser-based validation of GLONASS orbits by short-arc technique 总被引:1,自引:0,他引:1
F. Barlier C. Berger P. Bonnefond P. Exertier O. Laurain J. F. Mangin J. M. Torre 《Journal of Geodesy》2001,75(11):600-612
The International GLONASS Experiment (IGEX-98) was carried out between 19 October 1998 and 19 April 1999. Among several objectives
was the precise orbit determination of GPS and GLONASS satellites and its validation by laser ranging observations. Local
laser-based orbit corrections (radial, tangential and normal components in a rotating orbital local reference frame) are computed
using a geometrical short-arc technique. The order of magnitude of these corrections is at the level of few decimeters, depending
on the considered components. The orbit corrections are analyzed as a function of several parameters (date, orbital plane,
geographical area). The mean corrections are at the level of several centimeters. However, when averaging over the entire
campaign and for all the satellites, no mean radial, tangential and normal orbit corrections are found. The origin of the
observed corrections is considered (errors due to the geocentric gravitational constant, the non-gravitational forces, the
thermal equilibrium of on-board equipment, the reference systems, the location and the signature of the retroreflector array,
and the precision of the satellite laser ranges). Some features are also due to errors in the radio-tracking GLONASS orbits.
Further investigations will be needed to better understand the origin of various biases.
Received: 17 February 2000 / Accepted: 31 January 2001 相似文献
894.
We investigated the effect of two different spatial scales of climate change scenarios on crop yields simulated by the EPIC crop model for corn, soybean, and wheat, in the central Great Plains of the United States. The effect of climate change alone was investigated in Part I. In Part II (Easterling et al., 2001) we considered the effects ofCO2 fertilization effects and adaptation in addition to climate change. The scenarios were formed from five years of control and 2 ×CO2 runs of a high resolution regional climate model (RegCM) and the same from an Australian coarse resolution general circulation model (GCM), which provided the initial and lateral boundary conditions for the regional model runs. We also investigated the effect of two different spatial resolutions of soil input parameters to the crop models. We found that for corn and soybean in the eastern part of the study area, significantly different mean yield changes were calculated depending on the scenario used. Changes in simulated dryland wheat yields in the western areas were very similar, regardless of the scale of the scenario. The spatial scale of soils had a strong effect on the spatial variance and pattern of yields across the study area, but less effect on the mean aggregated yields. We investigated what aspects of the differences in the scenarios were most important for explaining the different simulated yield responses. For instance, precipitation changes in June were most important for corn and soybean in the eastern CSIRO grid boxes. We establish the spatial scale of climate changescenarios as an important uncertainty for climate change impacts analysis. 相似文献
895.
The Last Glacial Maximum climate over Europe and western Siberia: a PMIP comparison between models and data 总被引:3,自引:1,他引:3
M. Kageyama O. Peyron S. Pinot P. Tarasov J. Guiot S. Joussaume G. Ramstein 《Climate Dynamics》2001,17(1):23-43
Under the framework of the Palaeoclimate Modelling Intercomparison Project (PMIP), 17 climate models, 16 of which are atmospheric
general circulation models, have been run to simulate the climate of the Last Glacial Maximum (21 000 years ago) using the
same set of boundary conditions. Parallel to these numerical experiments, new, consistent, data bases have been developed
on a continental scale. The present work compares the range of the model responses to the large perturbation corresponding
to the conditions of the Last Glacial Maximum with consistently derived climate reconstructions from pollen records over Europe
and western Siberia. It accounts for the differences in the model results due to the models themselves and directly compares
this “error bar” due to the models to the uncertainties in the climate reconstructions from the pollen records. Overall the
Last Glacial Maximum climate simulated by the models over western Europe is warmer, especially in winter, and wetter than
the one depicted by the reconstructions. This is the region where the reconstructed increase in temperature, precipitation
and moisture index from the Last Glacial Maximum to the present conditions is largest. The same disagreement, but of smaller
amplitude, is found over Central Europe and the eastern Mediterranean Basin, while models and data are in broad agreement
over western Siberia. The numerous modelling results allow a study of the link between the changes in atmospheric circulation
and those in temperature, and an interpretation of the discrepancies in precipitation in terms of those in temperature.
Received: 1 February 2000 / Accepted: 9 May 2000 相似文献
896.
G.K. PLATTNER F. JOOS T. F. STOCKER O. MARCHAL 《Tellus. Series B, Chemical and physical meteorology》2001,53(5):564-592
Global warming simulations are performed with a coupled climate model of reduced complexity to investigate global warming–marine carbon cycle feedbacks. The model is forced by emissions of CO2 and other greenhouse agents from scenarios recently developed by the Intergovernmental Panel on Climate Change and by CO2 stabilization profiles. The uptake of atmospheric CO2 by the ocean is reduced between 7 to 10% by year 2100 compared to simulations without global warming. The reduction is of similar size in the Southern Ocean and in low‐latitude regions (32.5°S‐32.5°N) until 2100, whereas low‐latitude regions dominate on longer time scales. In the North Atlantic the CO2 uptake is enhanced, unless the Atlantic thermohaline circulation completely collapses. At high latitudes, biologically mediated changes enhance ocean CO2 uptake, whereas in low‐latitude regions the situation is reversed. Different implementations of the marine biosphere yield a range of 5 to 16% for the total reduction in oceanic CO2 uptake until year 2100. Modeled oceanic O2 inventories are significantly reduced in global warming simulations. This suggests that the terrestrial carbon sink deduced from atmospheric O2 /N2 observations is potentially overestimated if the oceanic loss of O2 to the atmosphere is not considered. 相似文献
897.
O. P. Singh 《Meteorology and Atmospheric Physics》2001,78(1-2):1-9
Summary
El Ni?o/Southern Oscillation (ENSO) is known to cause world-wide weather anomalies. It influences the Indian Monsoon Rainfall
(IMR) also. But due to large spatial and temporal variability of monsoon rains, it becomes difficult to state any single uniform
relationship between the ENSO and IMR that holds good over different subdivisions of India, though the general type of relationship
between all India monsoon rainfall and ENSO is known since long. The selection of the most suitable ENSO index to correlate
with the IMR is another problem. The purpose of the present study is twofold, namely, to examine the relationship between
the ENSO and IMR for entire monsoon season by using an ENSO index which represents the ENSO phenomenon in a comprehensive
way, namely, the Multivariate ENSO Index (MEI) and to establish the relationships between MEI and IMR for every meteorological
subdivision of India for each monsoon month; i.e. June, July, August and September. A comparison of MEI/IMR correlations has
been made with Southern Oscillation Index (SOI)/IMR correlations. The result may find applications in the long range forecasting
of IMR on monthly and subdivisional scales, especially over the high monsoon rainfall variability regions of Northwestern
and the Peninsular India.
Received October 27, 2000 相似文献
898.
Two regional climate models have been applied to the task of generating an ensemble of realizations of the year 1982 with
observed boundary conditions in areas covering parts of the Mediterranean countries. These realizations were generated by
applying boundary conditions from the ECMWF ERA reanalysis project consecutively, carrying over the soil variables from the
regional models from one iteration to the next. Monthly mean fields for six iterations of each model have been used as statistical
ensembles in order to investigate the internal variability of the regional model dynamics. This internal variability is a
necessary consequence of the non-linear physical feedback mechanisms of the RCM being active. A small value of internal variability
will give better statistics for climate sensitivity signals, but will make these results less credible. The internal variability
is important for the quantitative assessment of a climate sensitivity signal. With the present choice of models and integration
domains the internal variabilities of surface fields and precipitation do reach levels that are less than, but in summer of
comparable order of magnitude to, corresponding atmospheric variabilities of an atmospheric general circulation model.
Received: 26 October 1999 / Accepted: 18 December 2000 相似文献
899.
Most microsatellites are very polymorphic. This makes them powerful markers for observing genetic differentiation between closely related populations. The population structure of the Greenlandic Arctic fox ( Alopex lagopus ) was studied genetically by analysing six polymorphic microsatellite loci of 75 foxes from four populations in different parts of Greenland. Genotypes were determined at the six loci for most of the individuals. Population differentiation was quantified in three different ways both within the total population and pairwise between all populations. The tests were Fisher's exact test, Rho estimates and Fst estimates, all of which supported a highly significant subdivision of the total population, and they showed significant differentiation in allele frequencies between all pairs of localities. It is concluded that the known long-distance migration of the Greenlandic Arctic fox has not resulted in complete genetic mixing of the populations. Fisher's exact test was also used to estimate levels of genetic differentiation between the two colour morphs: white and blue. No difference was found between allele frequencies of the two color morphs in any of the locations, and it was concluded that the white and blue morphs of the Greenlandic Arctic fox share the same habitat, at least during the mating season. 相似文献
900.
Four thousand years of atmospheric lead pollution in northern Europe: a summary from Swedish lake sediments 总被引:8,自引:7,他引:8
This paper presents a large palaeolimnological study of the pre-industrial and industrial history of atmospheric lead pollution deposition in Sweden. Both lead concentrations and 206Pb/207Pb ratios have been analysed in 31 lakes covering most of Sweden, plus one lake in north-west Russia. Four of the lakes have varved (annually-laminated) sediments. Isotope analysis is a sensitive and effective method to distinguish pollution lead from natural catchment lead and to detect early pollution influence, because the 206Pb/207Pb ratio in unpolluted background sediments in Sweden was > 1.3, while that of lead from pollution, derived from ores and coal, was < 1.2. The sediments show a consistent picture of past temporal changes in atmospheric lead pollution. These changes include: the first traces of pollution 3,500-3,000 yrs ago; a pollution peak in Greek-Roman Times (about 0 AD); lower lead fall-out between 400 and 900 AD; a significant and permanent increase in atmospheric lead fall-out from about 1000 AD; an increase with the Industrial revolution; a major increase following World War II; the maximum peak in the 1970s; and decreasing fall-out over the last decades. The four varved sediments provide high-resolution records of atmospheric pollution. They reveal pollution peaks about 1200 and 1530 AD which match the history of metal production in Europe. According to the varve records the lead pollution level in the late 1990s had decreased beneath the level of the 1530s. The pollution level 1200 AD was about 35% of the 1980s, when lead pollution was still near its all time high. About 50% of the total accumulated atmospheric lead pollution deposition through time was deposited in the pre-industrial period. The sediments also show a consistent picture of the geographic distribution of atmospheric lead deposition over time, with higher deposition in south Sweden and declining levels to the north, which supports the hypothesis that the main sources of pre-industrial atmospheric lead pollution in Sweden were cultural areas in mainland Europe and Great Britain. 相似文献