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151.
152.
E.C. Sittler Jr. A. Ali J.F. Cooper R.E. Johnson D.T. Young 《Planetary and Space Science》2009,57(13):1547-17884
Discovery by Cassini's plasma instrument of heavy positive and negative ions within Titan's upper atmosphere and ionosphere has advanced our understanding of ion neutral chemistry within Titan's upper atmosphere, primarily composed of molecular nitrogen, with ~2.5% methane. The external energy flux transforms Titan's upper atmosphere and ionosphere into a medium rich in complex hydrocarbons, nitriles and haze particles extending from the surface to 1200 km altitudes. The energy sources are solar UV, solar X-rays, Saturn's magnetospheric ions and electrons, solar wind and shocked magnetosheath ions and electrons, galactic cosmic rays (GCR) and the ablation of incident meteoritic dust from Enceladus’ E-ring and interplanetary medium. Here it is proposed that the heavy atmospheric ions detected in situ by Cassini for heights >950 km, are the likely seed particles for aerosols detected by the Huygens probe for altitudes <100 km. These seed particles may be in the form of polycyclic aromatic hydrocarbons (PAH) containing both carbon and hydrogen atoms CnHx. There could also be hollow shells of carbon atoms, such as C60, called fullerenes which contain no hydrogen. The fullerenes may compose a significant fraction of the seed particles with PAHs contributing the rest. As shown by Cassini, the upper atmosphere is bombarded by magnetospheric plasma composed of protons, H2+ and water group ions. The latter provide keV oxygen, hydroxyl and water ions to Titan's upper atmosphere and can become trapped within the fullerene molecules and ions. Pickup keV N2+, N+ and CH4+ can also be implanted inside of fullerenes. Attachment of oxygen ions to PAH molecules is uncertain, but following thermalization O+ can interact with abundant CH4 contributing to the CO and CO2 observed in Titan's atmosphere. If an exogenic keV O+ ion is implanted into the haze particles, it could become free oxygen within those aerosols that eventually fall onto Titan's surface. The process of freeing oxygen within aerosols could be driven by cosmic ray interactions with aerosols at all heights. This process could drive pre-biotic chemistry within the descending aerosols. Cosmic ray interactions with grains at the surface, including water frost depositing on grains from cryovolcanism, would further add to abundance of trapped free oxygen. Pre-biotic chemistry could arise within surface microcosms of the composite organic-ice grains, in part driven by free oxygen in the presence of organics and any heat sources, thereby raising the astrobiological potential for microscopic equivalents of Darwin's “warm ponds” on Titan. 相似文献
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磷灰石结构通道离子对晶胞参数的影响 总被引:8,自引:1,他引:8
磷灰石晶胞参数受其结构中Ca多面体,磷氧四面体及结构通道位置上的类质同角替换的影响,本文探讨了54个磷灰石样吕的晶胞参数与结构通道离子F,OH,Cl相同象替换的影响,本文讨论了54个磷灰石样品的晶胞参数与结构通道离子F,OH,Cl相对含量的关系,发现Cl和取代是影响岩浆型磷灰石晶胞参数的主要因素,每原子/晶胞的Cl使a增大0.121 1(6)nm,c减少0.0633 (3)nm,根据成分与结构的经验关系式,可以验证电子探针对F的分析结果。 相似文献
155.
B. Galle J. Mellqvist D.W. Arlander I. Fløisand M.P. Chipperfield A.M. Lee 《Journal of Atmospheric Chemistry》1999,32(1):147-164
Vertical columns of HF, HCl, HNO3, ClONO2, N2O, ClO and COF2 were measured at Harestua, Norway (60.22° N, 10.75° E, Elevation 600 a.s.l.) beginning on 24 November 1994 and concluding on 1 May 1995 during Phase-III of the SESAME (Second European Stratospheric Arctic and Mid-latitude Experiment) measurement campaign. The vertical columns of HCl, HNO3 and ClONO2 measured on 81 days were compared with columns calculated by the 3-D Cambridge model SLIMCAT. In addition the results were also interpreted by comparison with a photochemical trajectory model. Good agreement was seen for HCl while the nitrogen compounds showed larger discrepancies, especially for ClONO2. Evidence for chlorine activation was seen with 65% reduction of the chlorine reservoirs (HCl + ClONO2) while the levels of ClO were greatly enhanced. Interpretation of the loss with the trajectory model indicated condensation of chlorine on PSCs. The vertical column ratio of COF2 and HF was measured to 0.21 outside the vortex and a factor of two lower inside. The recovery of ClONO2 was seen to be much faster than that of HCl in the early spring. 相似文献
156.
利用精密量热仪测定了MgCl_2、MgCl_2·2H_2O、MgCl_2·4H_2O和MgCl_2·6H_2O在298.15°K溶于水的积分溶解热,并利用Pitzer电解质溶液的。~ΦL方程,计算了溶质的相对表观摩尔热焓,从而得到标准溶解焓分别为(KJ·mol~(-1))—155.86±0.17、—79.45±O.17,—41.78±O.18和—14.58±0.16;晶格能分别为—2490.36,—3158.37,—3772.70和—4376.56。二、四、六水合物的标准生成焓分别为—1289.39,—1898.72和—2497.58;水合焓分别为—76.41,—114.08和—141.28。 相似文献
157.
Porewater geochemistry and solute flux from bottom sediments,Devils Lake,North Dakota 总被引:1,自引:0,他引:1
Sediment cores were collected for pore-water analysis from the eastern end of Devils Lake, located in northeastern North Dakota, to determine diagenetic reactions occurring in surficial bottom sediments and to evaluate the impact of these reactions on chemical concentrations in the overlying lake water. Sediment pore waters are enriched in major ions and nutrients relative to lake water. The principal sources of major ions to pore water are saline sediments located in the upper 1 m of bottom sediment. The principal source of titration alkalinity and nutrients to pore water is microbial decomposition of sedimentary organic matter by sulfate reduction. Sediment pore waters in the eastern part of Devils Lake have higher major-ion concentrations and solute-flux rates than the sediment pore waters in the central part of the lake. In contrast, sediment pore waters in the central part of Devils Lake have significantly higher nutrient concentrations and solute-flux rates. Major-ion concentrations and solute-flux rates in sediment pore water increase from west to east. These trends indicate that bottom-sediment diagenetic processes are, in part, responsible for the observed concentration gradient in the lake. The higher nutrient concentrations and the higher nutrient diffusional-flux rates in Main Bay are the result of more labile sedimentary organic matter and the occurrence of sulfate reduction. Environmentally-reactive trace-metal concentrations (Cu, Pb, Zn, and Fe) in bottom sediments decrease from west to east with distance from the surface-water sources and with increasing surface-water salinity. 相似文献
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Mohd Harun Abdullah Baba musta Mazlin Mokhtar Ahmad Zaharin Aris 《中国地球化学学报》2006,25(B08):151-152
The Sipadan island is the only oceanic island found in Malaysia, and is popularly known for its beautiful corals and diving activities. The aquifer of the island is affected by seawater intrusion associated with groundwater exploitation. Geologically, the aquifer is composed of several series of Quaternary bioherm facies, and its recharge merely depends on rainfall. This research attempts to understand the chemical changes of the groundwater attributed to the salinization processes based on major ion composition (Ca^2+, Mg^2+, Na^+, K^+, HCO, SO, Cl^-). The initial assessments were done in years 1993 - 1994, followed by subsequent assessment in years 2004-2005. Methods of analyses were adopted from APHA (1995). The hydrogeochemical saturation indices (SI) were computed using the PHREEQC program in order to assess the state of equilibrium between groundwater and the minerals present. The results of analyses indicated that the groundwater has been highly enriched in Na^+, SO and CI, reflecting an encroachment of saline water into the aquifer. The groundwater facies can be classified as sodium chloride (Na-Cl) water type. There are positive correlations (moderate to strong), except HCO3^-, between the studied parameters. The weak and inconsistent correlation of HCO3^- with the cations and anions related to dissolved salts suggests that saltwater intrusion has an insignificant impact on the chemistry of HCO3^- in the groundwater. Strong correlations (r 〉0.70) exist among the major elements (Na^+, Mg^2+, K^+, Cl^- and SO4^-) and salinity (EC). These relationships clearly identify the main elements contributing to the groundwater salinity and their tendency to depict a similar trend of salinization pattern. Chloride has a major influence on the salinity of groundwater based on the positive and strong correlation that exist between Cl^- and EC (r=0.97). 相似文献