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91.
Chao Zhan Junbao Yu Qing Wang Yunzhao Li Di Zhou Qinghui Xing Xiaojing Chu 《中国地理科学(英文版)》2017,27(6):934-947
Accurate assessment of surface suspended sediment concentration(SSSC) in estuary is essential to address several important issues: erosion, water pollution, human health risks, etc. In this study, an empirical cubic retrieval model was developed for the retrieval of SSSC from Yellow River Estuary. Based on sediments and seawater collected from the Yellow River and southeastern Laizhou Bay, SSSC conditions were reproduced in the laboratory at increasing concentrations within a range common to field observations. Continuous spectrum measurements of the various SSSCs ranging from 1 to 5700 mg/l were carried out using an Ava Field-3 spectrometer. The results indicated the good correlation between water SSSC and spectral reflectance(Rrs) was obtained in the spectral range of 726–900 nm. At SSSC greater than 2700 mg/L, the 740–900 nm spectral range was less susceptible to the effects of spectral reflectance saturation and more suitable for retrieval of high sediment concentrations. The best correlations were obtained for the reflectance ratio of 820 nm to 490 nm. Informed by the correlation between Rrs and SSSC, a retrieval model was developed(R2 = 0.992). The novel cubic model, which used the ratio of a near-infrared(NIR) band(740–900 nm) to a visible band(400–600 nm) as factors, provided robust quantification of high SSSC water samples. Two high SSSC centers, with an order of 103 mg/l, were found in the inversion results around the abandoned Diaokou River mouth, the present Yellow River mouth to the abandoned Qingshuigou River mouth. There was little sediment exchange between the two high SSSC centers due to the directions of the residual currents and vertical mixing. 相似文献
92.
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94.
Land use change is the result of the interplay between socioeconomic, institutional and environmental factors, and has important
impacts on the functioning of socioeconomic and environmental systems with important tradeoffs for sustainability, food security,
biodiversity and the vulnerability of people and ecosystems to global change impacts. Based on the results of the First Land
Use Survey in Tibet Autonomous Region carried out in the late 1980s, land use map of Lhasa area in 1990 was compiled for the
main agricultural area in Lhasa valley using aerial photos obtained in April, May and October 1991 and Landsat imagery in
the late 1980s and 1991 as remotely sensed data sources. Using these remotely sensed data, the land use status of Lhasa area
in 1991, 1992, 1993, 1995, 1999 and 2000 were mapped through updating annual changes of cultivated land, artificial forest,
grass planting, grassland restoration, and residential area and so on. Land use map for Lhasa area in 2007 was made using
ALOS AVNIR-2 composite images acquired on October 24 and December 26, 2007 through updating changes of main land use types.
According to land use status of Lhasa area in 1990, 1995, 2000 and 2007, the spatial and temporal land use dynamics in Lhasa
area from 1990 to 2007 are further analyzed using GIS spatial models in this paper. 相似文献
95.
ENVISAT测高数据波形重跟踪分析研究 总被引:9,自引:4,他引:5
对卫星测高技术中的波形重跟踪技术及其算法进行了详细分析讨论.同时分析了波形重跟踪中最小二乘解初值及权的确定,根据ENVISAT的SGDR波形数据,利用波形重跟踪技术研究了开阔海域上的距离改正情况(一般距离改正为20~30cm)。结果表明,重跟踪改正后的精度,18Hz距离优于1Hz距离。 相似文献
96.
A new method for the determination of the critical slip surfaces of slopes is proposed in this paper.In this paper,the original critical slip field method is extended in terms of the total residual moment,values of residual work as well as the unbalanced thrust force at the exit point for a given non-circular slip surface.The most critical slip surface with the maximum representative value for a prescribed factor of safety will be optimized and located using the harmony search algorithm.The prescribed factor of safety is modified with certain tiny interval in order to find the critical slip surface where the maximum representative value is zero.The aforementioned approach to the location of the critical slip surface is greatly different from the traditional limit equilibrium procedure.Three typical soil slopes are evaluated by use of the proposed method,and the comparisons with the classical approaches have illustrated the applicability of the proposed method. 相似文献
97.
???DNSC08-GRA????е????????????????????????????????Stokes??????????????????????????????????????????????Stokes????????-??????????????????3.4 cm???????????????????????????????GPS/????????м??????????????????????1.17 m???????????????С?7 cm?? 相似文献
98.
ZHANG WeiGuo JIANG JingShan LIU HeGuang ZHANG XiaoHui ZHANG DeHai LI DiHui & XU Chu ong Centre for Space Science Applications Research Chinese Academy of Sciences Beijing China 《中国科学:地球科学(英文版)》2010,(3)
Investigation on Lunar polar area is almost every lunar mission’s primary objective in recent years. The rationale behind it is that illumination and ice resources in this area can be potentially very helpful for constructing lunar human base. In this paper, we analyze microwave radiometric characteristics of the Moon by using the newly acquired Chang’E-1 Lunar Microwave Sounder (CELMS) data. Microwave brightness temperature at Lunar South Pole (LSP) is distributed regularly with a style of "ring-in-ring", decreasing from equator to pole. Regolith temperature gradient is bigger at lunar equator than at polar area. Brightness temperature diurnal difference decreases with observation frequency. Microwave brightness temperature distribution maps at LSP and Lunar North Pole (LNP) have been made based on the analysis. It is found that microwave brightness temperature becomes to synchronize with elevation beyond -85° latitude. This phenomenon is related to lightening condition and indicates temperature distribution at LSP. The brightness temperature anomaly cold points are potentially cold trap areas for water or ice while hot points imply plenty of illumination resources there. 相似文献
99.
Phase relations of phlogopite with magnesite from 4 to 8 GPa 总被引:2,自引:2,他引:0
Andreas?EnggistEmail author Linglin?Chu Robert?W.?Luth 《Contributions to Mineralogy and Petrology》2012,163(3):467-481
To evaluate the stability of phlogopite in the presence of carbonate in the Earth’s mantle, we conducted a series of experiments
in the KMAS–H2O–CO2 system. A mixture consisting of synthetic phlogopite (phl) and natural magnesite (mag) was prepared (phl90-mag10; wt%) and run at pressures from 4 to 8 GPa at temperatures ranging from 1,150 to 1,550°C. We bracketed the solidus between
1,200 and 1,250°C at pressures of 4, 5 and 6 GPa and between 1,150 and 1,200°C at a pressure of 7 GPa. Below the solidus,
phlogopite coexists with magnesite, pyrope and a fluid. At the solidus, magnesite is the first phase to react out, and enstatite
and olivine appear. Phlogopite melts over a temperature range of ~150°C. The amount of garnet increases above solidus from
~10 to ~30 modal% to higher pressures and temperatures. A dramatic change in the composition of quench phlogopite is observed
with increasing pressure from similar to primary phlogopite at 4 GPa to hypersilicic at pressures ≥5 GPa. Relative to CO2-free systems, the solidus is lowered such, that, if carbonation reactions and phlogopite metasomatism take place above a
subducting slab in a very hot (Cascadia-type) subduction environment, phlogopite will melt at a pressure of ~7.5 GPa. In a
cold (40 mWm−2) subcontinental lithospheric mantle, phlogopite is stable to a depth of 200 km in the presence of carbonate and can coexist
with a fluid that becomes Si-rich with increasing pressure. Ascending kimberlitic melts that are produced at greater depths
could react with peridotite at the base of the subcontinental lithospheric mantle, crystallizing phlogopite and carbonate
at a depth of 180–200 km. 相似文献
100.
The objective of this research is to investigate the role of geography in the venture capital investment in the US biotechnology
industry. Data include 4,409 quarterly investment deals from the MoneyTree Survey during 1995 and 2008. Strong spatial concentration
patterns are identified. Using both ordinary squares regressions and geographically weighted regressions, we find that as
the geographic distance between biotechnology firms and their investors decreases, deal size increases. Location in established
biotechnology clusters, such as New England and California, helps to bring a larger deal into individual firms as well. Also,
the impact of distance decay in these two clusters is more significant than that in other regions. In addition, we find that
a global venture capital investing syndication network brings large deals. Furthermore, firms in later stages of development,
and/or with few financing rounds, tend to receive more capital per deal. 相似文献