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排序方式: 共有122条查询结果,搜索用时 15 毫秒
1.
Seasonal and Diurnal Variation of Surface Ozone and a Preliminary Analysis of Exceedance of its Critical Levels at a Semi-arid Site in India 总被引:1,自引:0,他引:1
Gur Sumiran Satsangi A. Lakhani P. R. Kulshrestha A. Taneja 《Journal of Atmospheric Chemistry》2004,47(3):271-286
The mixing ratios of surface O3 were measured at St. John's College, Agra, an urban and traffic influenced area for the period of 2000–2002. The monthly
averaged O3 mixing ratios ranged between 8 to 40 ppb with an annual average of 21 ppb. Strong diurnal and seasonal variations in O3 mixing ratios were observed throughout the year except for monsoon season. The mixing ratios of O3 follow the surface temperature cycle and solar radiation (r = 0.72 and r = 0.65 with temperature and solar radiation, respectively). Concentrations were higher with winds associated with NE and
NW direction indicating the impact of pollution sources on surface O3 concentration. Exceedance of ozone critical level was calculated using the AOT 40 index and found to be 840 ppb.h and 2430
ppb.h for summer and winter seasons, respectively. The present O3 exposures are lower than the critical level of O3 and suggest that the present level of O3 does not have any impact on reduction in crop yields. 相似文献
2.
3.
R. L. McKenzie W. A. Matthews Y. Kondo R. Zander Ph. Demoulin P. Fabian D. G. Murcray F. J. Murcray O. Lado-Bordowsky C. Camy-Peyret H. K. Roscoe J. A. Pyle R. D. McPeters 《Journal of Atmospheric Chemistry》1988,7(4):353-367
Column measurements of nitric oxide were made using several techniques during the MAP/GLOBUS campaign in France in September 1985. The data sets are nearly co-located and simultaneous, therefore allowing a valid intercomparison of the various measurement methods. The range of altitudes sampled differs from instrument to instrument. This complicates the comparison because the data sets are to some extent complementary. The NO distributions apparently vary significantly from day to day, and possibly over shorter timescales. Changes in dynamics may be responsible for these variations. The results from the instruments which measure in the infrared and the ultraviolet are self-consistent, and show good agreement with photochemical predictions. On 19 September, when the intercomparison was made, the profile measured by the in-situ chemiluminescent instrument differed significantly from the predicted profile, and the measured columns were generally higher. 相似文献
4.
应用大气光化学模式研究了日间影响NOx光化学转化率的主要物理化学因子.探讨了在不同NMHC/NOx比值时,NOx光化学特征及其转化产物的变化规律.结果表明,影响NOx转化率的主要因子是阳光辐射强度和NMHC/NOx比值.但在NMHC/NOx比值很低时,光强的增加并不能显著提高NOx转化率.温度和初始臭氧浓度对NOx转化率的影响次之.相对湿度对NOx转化率的影响较小.在不同NMHC/NOx比值下,NOx转化特征和产物有很大区别.NMHC/NOx比值高时,产物中PAN>HNO3.NMHC/NOx比值中(低)时,产物主要是HNO3,PAN等有机氮不到10%(1%).最后初步比较了模拟和观测的NOy组成. 相似文献
5.
MEASUREMENTS AND MODEL SIMULATIONS OF SURFACE OZONE VARIATIONS AT DIFFERENT BACKGROUND CONCENTRATIONS OF THE PRECURSORS 总被引:1,自引:0,他引:1
Ozone photochemical production and loss in very different environments at Waliguan baselinestation and Lin'an background station were simulated by using the measurement data and photo-chemical box model.The results show that net ozone photochemical production rate is negative,about 0.5 ppb/d,at Waliguan baseline sation,because of very low precursor concentrations.Butat Lin'an background station,the net photochemical ozone production is positive,about 2—3 ppb/h.which is very closed with the measurement at Lin'an.That means ozone production was con-trolled by photochemical reactions at Lin'an background station,because of the higher precursorconcentrations.The net destruction rate,at Waliguan Mt.,is not large,so that future increase inanthropogenic emission of reactive nitrogen will lead to larger production rates of steady-state O_3concentration. 相似文献
6.
兰州冬季气溶胶光学特性的参数化 总被引:9,自引:1,他引:9
兰州冬季气溶胶的谱分布用双谱模式拟合,即Junge谱加Deirmendjian谱;气溶胶的平均折射率为1.549-0.1i;气溶胶浓度随高度的分布根据天气条件取为高斯、均匀、指数分布三种类型。以此为基础,计算出兰州冬季气溶胶光学厚度的平均值。 经实测的气溶胶光学厚度与本文的计算值比较后发现,我们的参数化方案基本上是成功的。 相似文献
7.
Simulations of seasonal variations of sulfur compounds in the remote marine atmosphere 总被引:1,自引:0,他引:1
A photochemical box model is used to simulate seasonal variations in concentrations of sulfur compounds at latitude 40° S. It is assumed that the hydroxyl radical (OH) addition reaction to sulfur in the dimethyl sulfide (DMS) molecule is the predominant pathway for methanesulfonic acid (MSA) production, and that the rate constant increases as the air temperature decreases. Concentration of the nitrate radical (NO3) is a function of the DMS flux, because the reaction of DMS with NO3 is the most important loss mechanism of NO3. While the diurnally averaged concentration of OH in winter is a factor of about 8 smaller than in summer, due to the weak photolysis process, the diurnally averaged concentration of NO3 in winter is a factor of about 4–5 larger than in summer, due to the decrease of DMS flux. Therefore, at middle and high latitudes in winter, atmospheric DMS is mainly oxidized by the reaction with NO3. The calculated ratio of the MSA to SO2 production rates is smaller in winter than in summer, and the MSA to non-sea-salt sulfate (nssSO4
2-) molar ratio varies seasonally. This result agrees with data on the seasonal variation of the MSA/nssSO4
2- molar ratio obtained at middle and high latitudes. The calculations indicate that during winter the reaction of DMS with NO3 is likely to be a more important sink of NOx (NO+NO2) than the reaction of NO2 with OH, and to serve as a significant pathway of the HNO3 production. If dimethyl sulfoxide (DMSO) is produced through the OH addition reaction and is heterogeneously oxidized in aqueous solutions, half of the nssSO4
2- produced in summer may be through the oxidation process of DMSO. It is necessary to further investigate the oxidation products by the reaction of DMS with OH, and the possibility of the reaction of DMS with NO3 during winter. 相似文献
8.
Two years of individual nonmethane hydrocarbon (NMHC) measurements at a rural site close to the south coast of Norway show that there was a distinct annual cycle with a late winter maximum and late summer minimum in the slowly reacting NMHCs acetylene, ethane, propane and i- and n-butane. The average January—March concentrations were a factor 2–4 higher than the July-September concentrations. Also ethene, propene and the pentanes show a similar annual cycle, but the individual scatter in the measurements in particular of propene, is large. The highest concentrations of NMHC were found in winter for easterly transport on a regional scale (out to 1500 km from the site), and for southeasterly transport in the summer. 相似文献
9.
Harald Geiger Ian Barnes Karl H. Becker Birger Bohn Theo Brauers Birgit Donner Hans-Peter Dorn Manfred Elend Carlos M. Freitas Dinis Dirk Grossmann Heinz Hass Holger Hein Axel Hoffmann Lars Hoppe Frank Hülsemann Dieter Kley Björn Klotz Hans G. Libuda Tobias Maurer Djuro Mihelcic Geert K. Moortgat Romeo Olariu Peter Neeb Dirk Poppe Lars Ruppert Claudia G. Sauer Oleg Shestakov Holger Somnitz William R. Stockwell Lars P. Thüner Andreas Wahner Peter Wiesen Friedhelm Zabel Reinhard Zellner Cornelius Zetzsch 《Journal of Atmospheric Chemistry》2002,42(1):323-357
Within the German Tropospheric Research Programme (TFS) numerous kinetic and mechanistic studies on the tropospheric reaction/degradation of the following reactants were carried out: oxygenated VOC, aromatic VOC, biogenic VOC, short-lived intermediates, such as alkoxy and alkylperoxy radicals.At the conception of the projects these selected groups were classes of VOC or intermediates for which the atmospheric oxidation mechanisms were either poorly characterised or totally unknown. The motivation for these studies was the attainment of significant improvements in our understanding of the atmospheric chemical oxidation processes of these compounds, particularly with respect to their involvement in photooxidant formation in the troposphere. In the present paper the types of experimental investigations performed and the results obtained within the various projects are briefly summarised. The major achievements are highlighted and discussed in terms of their contribution to improving our understanding of the chemical processes controlling photosmog formation in the troposphere. 相似文献
10.
The time damping rate of gravity wave in the range of 30-70 km is calaclated in three circumstances:(1) adiabatic process,(2) diabatic process caused by atmospheric cooling,and(3) diabatic process resulting from atmospheric photochemical heating and cooling.The results indicate that the photochemical heating is as important as Newtonian cooling and its contribution to the time damping rate of gravity wave can not he negligible. 相似文献