全文获取类型
收费全文 | 104117篇 |
免费 | 1325篇 |
国内免费 | 705篇 |
专业分类
测绘学 | 2268篇 |
大气科学 | 6595篇 |
地球物理 | 20184篇 |
地质学 | 37269篇 |
海洋学 | 9408篇 |
天文学 | 24586篇 |
综合类 | 296篇 |
自然地理 | 5541篇 |
出版年
2022年 | 758篇 |
2021年 | 1286篇 |
2020年 | 1366篇 |
2019年 | 1515篇 |
2018年 | 3137篇 |
2017年 | 2911篇 |
2016年 | 3371篇 |
2015年 | 1676篇 |
2014年 | 3251篇 |
2013年 | 5439篇 |
2012年 | 3561篇 |
2011年 | 4539篇 |
2010年 | 4092篇 |
2009年 | 5216篇 |
2008年 | 4565篇 |
2007年 | 4719篇 |
2006年 | 4305篇 |
2005年 | 3043篇 |
2004年 | 2931篇 |
2003年 | 2747篇 |
2002年 | 2707篇 |
2001年 | 2415篇 |
2000年 | 2306篇 |
1999年 | 1808篇 |
1998年 | 1873篇 |
1997年 | 1758篇 |
1996年 | 1479篇 |
1995年 | 1479篇 |
1994年 | 1264篇 |
1993年 | 1197篇 |
1992年 | 1133篇 |
1991年 | 1139篇 |
1990年 | 1150篇 |
1989年 | 1001篇 |
1988年 | 918篇 |
1987年 | 1081篇 |
1986年 | 929篇 |
1985年 | 1166篇 |
1984年 | 1301篇 |
1983年 | 1251篇 |
1982年 | 1157篇 |
1981年 | 1083篇 |
1980年 | 1012篇 |
1979年 | 893篇 |
1978年 | 908篇 |
1977年 | 770篇 |
1976年 | 751篇 |
1975年 | 751篇 |
1974年 | 727篇 |
1973年 | 801篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Daniel D. Riemer Eric C. Apel John J. Orlando Geoffrey S. Tyndall William H. Brune Eric J. Williams William A. Lonneman James D. Neece 《Journal of Atmospheric Chemistry》2008,61(3):227-242
As part of the 2000 Texas Air Quality Study (TexAQS), we studied the isoprene oxidation process under ambient conditions to
discern the presence of chlorine atom (Cl) chemistry in the Houston, Texas urban area. By measuring chloromethylbutenone (CMBO)
and an isomer of chloromethylbutenal (CMBA), we clearly observed sixteen episodes of active Cl chemistry during the 24-day
experiment. Estimated median Cl concentration during each of these episodes was between the detection limit of ~102 atoms cm−3 and 50 - 30 + 70 ×104 50_{ - 30}^{ + 70} \times {10^4} atoms cm−3. Cl concentration during all the episodes averaged 7.6 - 2.0 + 4.7 ×104 7.6_{ - 2.0}^{ + 4.7} \times {10^4} atoms cm−3 and thus amounted to less than 3% of the OH concentration during the same periods. During the episodes, the fraction of oxidation
chemistry initiated by Cl ranged from 3–43% and was strongly dependent on the quantity and type of hydrocarbons present in
the atmosphere. Because of its intermittent presence and low concentration, Cl is not a broadly influential oxidant in the
Houston, Texas urban area. 相似文献
982.
983.
Summary Tropical cyclone (TC)—ocena feedbacks are studied using a coupled tropical cyclone-ocean model consisting of an eightlayer triply-nested movable grid model of a TC and a three-layer primitive equation ocean model. The numerical results indicate that the TC-ocean interaction influences intensities, structures, and the trajectories of tropical cyclones. Two possible mechanisms, barotropic and baroclinic, influencing TC tracks under TC-ocean interaction are suggested. The barotropic mechanism is related to the changes of the vertically averaged TC structure, induced by the TC-ocean coupling. The baroclinic mechanism is related to the asymmetry of the condensation heating within the TC caused by the asymmetry of heat and moisture fluxes at the sea surface. This asymmetry arises due to the asymmetry in sea surface cooling relative to the storm center. The experiments indicate that the influence of TC-ocean interaction on the TC tracks is the greatest for the case of a zero background flow. In the case of a non-zero background flow the sensitivity of storm tracks to the coupling with the ocean decreases. It is found that the influence of the ocean coupling on the TC track is quite sensitive to the method of convective heating parameterization in the TC model. The TC-ocean interaction also results in a change of the amount and spatial distribution of precipitation. 相似文献
984.
Observations were made of a shallow stratus of upslope origin using an aircraft equipped with insitu probes and with a vertically-pointing radar of 3-mm wavelength. A cloud layer of 300 m thickness was found below the inversion; an additional layer of 100 m thickness was located within the inversion. The coldest temperature within the cloud was -2°C and the cloud contained no ice particles. Drizzle drops up to 180 Am were present in both cloud layers.The observations reveal precipitation and air motion structures of approximately 1 km horizontal dimensions. The origin of this organization appears to be weak convection. In addition, mixing played an important role in forming the cloud droplet and drizzle drop size distributions. 相似文献
985.
Measured spectra ofθ
x,θ
y,θ
z, the derivatives of temperature in streamwise, lateral and vertical directions, respectively, indicate that the spectral
densities ofθ
z andθ
y are nearly similar but significantly different from the spectral density ofθ
x. The high-frequency parts of the three spectra satisfy, in a qualitative sense, local isotropy requirements. In the high-frequency
end of the inertial subrange, the relative behaviour of spectra ofθ
x,θ
y andθ
z is also consistent with local isotropy. 相似文献
986.
S.A. Hsu 《Dynamics of Atmospheres and Oceans》1984,8(3-4)
Field experiments have shown that an internal boundary layer (IBL) can develop when the wind blows perpendicularly from the cold-water side of a warm oceanic current to the warmer side. The height of this IBL downwind from the thermal front as computed by an equation originally developed by Venkatram is in excellent agreement with observations. 相似文献
987.
988.
M. Teresa Pardo M.A. Esteve A. Gimnez J. Martínez-Fernndez M.F. Carreo J. Serrano J. Miano 《Journal of Arid Environments》2008,72(10):1803-1810
Changes in wandering beetle assemblages (Carabidae and Tenebrionidae) of different habitats situated in coastal wetlands of a Mediterranean arid area (Mar Menor, SE Spain) were analysed in 1984, 1992 and 2003 by pitfall trapping. Over two decades, the increase in irrigated lands at watershed scale led to rising water tables in the Mar Menor wetlands, which affected their beetle communities. These hydrological changes caused an increase in the carabid population, particularly in the sites most affected by flooding, where halobionts and halophiles, which were practically absent in 1984 and 1992, had become dominant by 2003. In contrast, tenebrionid assemblages simplified with time and by 2003 were dominated by one or two generalist species. 相似文献
989.
This paper deals with the periodic fluctuation of precipitation at three meteorological stations (Atar, Chenguitti, and Akjoujt) in the Adrar and Inchiri provinces in northern Mauritania and its links with sea surface temperature (SST). Trends for these three meteorological stations were evaluated using the Mann–Kendall (MK) nonparametric test, regression analysis, and autocorrelation for persistence analysis. The MK test showed a significant decreasing trend for Akjoujt and an insignificant trend for the other rainfall time series. However, the decreasing linear regression trends were highly significant for the different time series. On the other hand, persistence analysis indicated the presence of a linear Markov type. The cycles found by power spectrum analysis ranged from 0.5 years to about 11 years. The possibility of a connection between precipitation in this region and sunspot numbers was suggested. SST of the Atlantic Ocean, Indian Ocean, and Mediterranean Sea have significant cross-correlations with precipitation in the study area. The El Niño-Southern Oscillation effect was found to be marginal. 相似文献
990.