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951.
Giovanni Di Virgilio Shawn W. Laffan 《International journal of geographical information science》2014,28(8):1658-1673
Species ranges are often represented using polygons, with the attendant issues that they show uniform ranges with abrupt boundaries and can overestimate species ranges. We demonstrate that such uniform species ranges can be supplemented by mapping the gradational variation in species turnover across a landscape. Directional variation in species turnover for 15 skink species (Reptilia: Scincidae) and topographic and climatic turnover in south-eastern Australia were measured using directional moving window analyses, rotated through 360°. The resultant species turnover maps were compared with published polygon range maps for two species within the group (Liopholis whitii and L. inornata). We also assessed how the relationships between species and environmental turnover varied in areas of low or high species turnover. Continuous transitions between distinct areas of low and high species turnover were mapped. Low turnover comprised only 19% of the L. whitii polygon species range within the study area extent. These low turnover areas were more densely populated by L. whitii (67% of observations), whereas areas of medium to high turnover contained substantially fewer observations (25%). Regions with the highest species turnover contained only 6% of observations. L. inornata observations were also clustered in low species turnover areas. Averaged climatic and elevation values were higher in low-turnover areas despite their close adjacency to high-turnover zones. The environmental turnover in low species turnover regions was also lower than in high-turnover areas. Correlations between environmental turnover and low species turnover areas were positive, whereas the opposite relationship applied in high species turnover areas. We identified both abrupt and gradual distributional breaks between separate reptile assemblages; an example of the latter is located in the Hunter Valley in the south-eastern coastal region. This break has been mapped using solid, uniform lines in species ranges and thus implicitly as an abrupt break. Environmental conditions may be more favourable to skinks in low-turnover areas. Since L. whitii and other skink species have very large populations in low-turnover areas, other squamate species may also be more likely to occur in these areas. This has potential implications for conservation prioritisation. The turnover maps used here can supplement the information provided about reptile distributions by the equivalent polygon ranges. This approach can be applied to point occurrence data for any taxonomic group or any similar georeferenced diversity data set. 相似文献
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954.
Songjun Han Di Xu Shaoli Wang Zhiyong Yang 《Theoretical and Applied Climatology》2014,117(3-4):501-510
Local actual evapotranspiration can be estimated with routinely measured meteorological variables using the Penman–Monteith model with surface resistance parameterized via the Katerji and Perrier approach (Agronomie 3(6):513–521, 1983; PM–KP model), or the nonlinear complementary relationship (CR) model proposed by Han et al. (Hydrol Process 26:3973–3981, 2012). A comparative study was carried out to evaluate the consistencies and differences of two models, as well as the performances of them for a cropland and grassland in northeast China. The departure of the actual evapotranspiration from the potential evaporation is described as a function of the ratio of the surface resistance to the aerodynamic resistance in the Penman–Monteith model, but the ratio of the aerodynamic term to the radiation term in the CR models. The two ratios are connected using a semi-empirical linear function by the Katerji and Perrier approach. The nonlinear CR model can be regarded as replacing the linear function by a power function after mathematical processing. On the other hand, the PM–KP model can be also considered as a CR-type model. On the daily basis at a maize cropland and degraded grassland in semiarid Northeast China, the nonlinear CR model with locally calibrated parameters performed better with data occupying all the growth stages, but the performances of the two models are similar during the early-, mid-, and late-season stages, respectively. On the half-hourly basis, the PM–KP model and the nonlinear CR model both performed well. It is deduced that on the daily basis the nonlinear CR model is more suitable for the cropland and grassland, but further comparisons are needed on the hourly basis. 相似文献
955.
Frost-free season lengthening and its potential cause in the Tibetan Plateau from 1960 to 2010 总被引:1,自引:0,他引:1
Dan Zhang Wenhui Xu Jiayun Li Zhe Cai Di An 《Theoretical and Applied Climatology》2014,115(3-4):441-450
Frost-free season was an important index for extreme temperature, which was widely discussed in agriculture and applied meteorology research. The frost-free season changed, which was associated with global warming in the past few decades. In this study, the changes in three indices (the last frost day in spring, the first frost day in autumn, and the frost-free season length) of the frost-free season were investigated at 73 meteorological stations in the Tibetan Plateau from 1960 to 2010. Results showed that the last frost day in spring occurred earlier, significantly in 39 % of the 73 stations. For the regional average, the last frost day in spring occurred earlier, significantly at the rate of 1.9 days/decade during the last 50 years. The first frost day in autumn occurred later, significantly in 31 % of the stations, and the regional average rate was 1.5 days/decade from 1960 to 2010. The changing rate of the first frost day in autumn below 3,000 m was 1.8 times larger than the changing rate above 3,000 m. In addition, the first frost day in autumn above 3,000 m fluctuated dramatically before the early 1990s and then it was later sharply after the early 1990s. The frost-free season length increased significantly at almost all stations in the Tibetan Plateau from 1960 to 2010. For the regional average, the frost-free season lengthened at the rate of 3.1 days/decade. The changing rate of the frost-free season length below 3,000 m was more significant than the changing rate above 3,000 m. Eight indices of large-scale atmospheric circulation were employed to investigate the potential cause of the frost-free season length change in the Tibetan Plateau during the past 50 years. There was a significant relationship between the frost-free season length and the Northern Hemisphere Polar Vortex indices. The weakening cold atmospheric circulation might be an essential factor to the Tibetan Plateau warming since 1960. 相似文献
956.
2013年土地资源形势分析 总被引:1,自引:0,他引:1
2013年土地资源运行总体平稳。土地供应稳步增加,保障经济平稳运行;中西部地区土地供应持续快速增长,地区差距逐渐缩小;土地市场量价齐涨,地价环比增幅连续小幅上涨;房地产市场全面回暖,土地购置面积实现正增长。 相似文献
957.
958.
Education,politics and opinions about climate change evidence for interaction effects 总被引:4,自引:2,他引:2
Lawrence C. Hamilton 《Climatic change》2011,104(2):231-242
U.S. public opinion regarding climate change has become increasingly polarized in recent years, as partisan think tanks and
others worked to recast an originally scientific topic into a political wedge issue. Nominally “scientific” arguments against
taking anthropogenic climate change seriously have been publicized to reach informed but ideologically receptive audiences.
Reflecting the success of such arguments, polls have noted that concern about climate change increased with education among
Democrats, but decreased with education among Republicans. These observations lead to the hypothesis that there exist interaction
(non-additive) effects between education or knowledge and political orientation, net of other background factors, in predicting
public concern about climate change. Two regional telephone surveys, conducted in New Hampshire (n = 541) and Michigan (n = 1, 008) in 2008, included identical climate-change questions that provide opportunities to test this hypothesis. Multivariate
analysis of both surveys finds significant interactions. These empirical results fit with theoretical interpretations and
several other recent studies. They suggest that the classically identified social bases of concern about the environment in
general, and climate in particular, have shifted in recent years. Narrowcast media, including the many Web sites devoted to
discrediting climate-change concerns, provide ideal conduits for channeling contrarian arguments to an audience predisposed
to believe and electronically spread them further. Active-response Web sites by climate scientists could prove critical to
counterbalancing contrarian arguments. 相似文献
959.
A pilot cropland carbon sequestration program within north central Montana has allowed farmers to receive carbon credit for management adjustments associated with changing from tillage-based agricultural systems to no-till. Carbon credit can also be obtained by adopting conservation reserve, where cropland is planted into perennial vegetation. Summer fallowing is also considered within the crediting process as credit is not given in years that a field is left un-vegetated. The carbon sequestration program has been advocated as a means to mitigate climate change while providing an added source of income for Montana farmers. There is lack of data, however, pertaining to the percentage of lands within this region that have not converted to no-till management, lands under certain crop intensities (e.g. those that are cropped every growing season vs. those that use a fallow-crop-fallow system), or cropland that have converted to perennial vegetation outside of the popular Conservation Reserve Program. Data is also sparse concerning the amount of soil organic carbon that might be sequestered given a conversion to no-till or conservation reserve. This study established regional percentage estimates of cropland under no-till, various degrees of crop intensity, and conservation reserve within north central Montana. Literature-based carbon sequestration estimates were used to generate carbon gain data associated with the conversation to no-till and to conservation reserve. These estimates were then applied to the area-based cropland statistics to estimate potential regional carbon sequestration associated with these management changes. 相似文献
960.
Ballast water is a potential source of invasive species, including viruses that target a variety of hosts. We sampled ballast during two trans-Pacific voyages and analyzed the efficacy of mid-oceanic exchange in reducing virus-like particle (VLP) abundance. Exchange did not significantly reduce virus abundance during the first voyage (P = 0.874), whereas it reduced viral abundance 3.9-fold from 1.8 × 107 to 0.47 × 107 VLP mL−1 during the second voyage (P < 0.0001). Despite the impact of exchange during the second voyage, virus abundances were not significantly different between exchanged and unexchanged tanks upon arrival in Canada (P = 0.363) and Canadian port water samples (P = 0.502). Regressions between environmental parameters and VLP abundance uncovered negative correlations between salinity and viral abundance during one, and dissolved oxygen and viral abundance during the second voyage. In summary, ballast tanks are highly variable with respect to total virus abundance, and the efficacy of exchange requires investigation into the dynamics of specific viruses. 相似文献