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101.
V.?Botella V.?Timon E.?Escamilla-Roa A.?Hernández-Languna C.I.?Sainz-DíazEmail author 《Physics and Chemistry of Minerals》2004,31(8):475-486
The hydroxy groups of the crystal lattice of dioctahedral 2:1 phyllosilicates were investigated by means of quantum-mechanical calculation. The standard Kohn-Sham self-consistent density functional theory (DFT) method was applied using the generalized gradient approximation (GGA) with numerical atomic orbitals and double-zeta polarized functions as basis set. Isomorphous cation substitution of different cations in the octahedral and tetrahedral sheet was included along with several interlayer cations reproducing experimental crystal lattice parameters. The effect of these substitutions and the interlayer charge on the hydroxyl group properties was also studied. These structures represent different cation pairs among Al3+, Fe3+ and Mg2+ in the octahedral sheet of clays joined to OH groups. The geometrical disposition of the OH bond in the crystal lattice and the hydrogen bonds and other electrostatic interactions of this group were analyzed. The frequencies of different vibrational modes of the OH group [(OH), (OH) and (OH)] were calculated and compared with experimental data, finding a good agreement. These frequencies depend significantly on the nature of cations which are joined with, and the electrostatic interactions with, the interlayer cations. Besides, hydrogen-bonding interactions with tetrahedral oxygens are important for the vibrational properties of the OH groups; however, also the electrostatic interactions of these OH groups with the rest of tetrahedral oxygens within the tetrahedral cavity should be taken into account. The cation substitution effect on the vibration modes of the OH groups was analyzed reproducing the experimental behaviour.Dr. V. Botella passed away last February 相似文献
102.
Kinetics of hydrogen extraction were investigated by FTIR spectroscopy on a Dora Maira pyrope single crystal. Annealing experiments were performed at ambient pressure, between 1073 and 1323 K, and under two different redox conditions (pO2=0.21 atm and pO2 10–16 atm). During hydrogen extraction the two principal OH absorption bands behave independently. The OHa triplet, centred on 3651 cm–1, decreases at least five times faster than the OHb band at 3602 cm–1. This suggests the presence of two distinct H defects, each with its own kinetics, which are slightly dependent on oxygen partial pressure:Both kinetics are slower than previous data (Wang et al. 1996), but activation energies are similar. At the same time as the OHa bands decrease, an exchange of hydrogen from OHa to OHb occurs. The extent of this transfer can be modelled by assuming it is directly proportional to the fraction of OHa band which has been removed, independent of temperature. This suggests that OHb defects could be produced by partial dehydrogenation of OHa defects. Activation energies and values of diffusion coefficients are very close to those found by Kohlstedt and Mackwell (1998) for the diffusion of metal vacancies in olivine. Thus it is very likely that cation vacancies control the kinetics of dehydrogenation reactions in pyrope. 相似文献
103.
大柴旦温泉沟泉水作为柴达木盆地出露的典型富矿水体,对于揭示柴达木盆地成盐、成矿至关重要。为了研究泉水的地球化学成因,开展了热泉水、冷泉水和八里沟河流水体的元素和氢氧同位素地球化学研究及其对比分析,并结合区域地质构造特征对其水体的来源、水文过程形成了较为细化的新认识:温泉沟的泉水来源于冰雪融水,而与雨水关系不大;八里沟水体相对富集B、Li,且具有类似于泉水的地球化学特征,推断其成因与断裂带密切相关。对于岩浆水与泉水的关系,需要进一步开展研究。 相似文献
104.
105.
The Yuanba gas field in the Permian Changxing Formation (P2c), which exhibits wide variations in its hydrogen sulfide (H2S) concentration (1.20–12.16%), is a typical sour gas field in the northern Sichuan Basin. The sulfur-rich reservoir's solid bitumen (atomic S/C ratios are 0.032–0.142), and late calcite cement δ13C values, which are smaller than the δ13C values of the host dolostone, indicate that the H2S originated from thermal sulfate reduction (TSR) and oil was involved in TSR. The gas souring index (GSI) of P2c's gases is generally lower than 0.1. The ethane δ13C values increase as the GSI increases, although no obvious increase was observed in the methane δ13C values. The calcite cements' δ13C values (−15.36 to +4.56‰) in dolostone are heavier than the typical reported values, which implies that only limited heavy hydrocarbon gases were involved in TSR. No anhydrites developed in P2c's reservoirs, and dissolved sulfate anions (SO42−) were mainly enriched during dolomitization. Insufficient dissolved SO42− most likely caused the lower H2S concentrations in the Permian to Triassic reservoirs in the northeastern Sichuan Basin compared to the Permian Khuff Formation in Saudi Arabia and the Jurassic Smackover Formation in Mississippi. Except for the SO42− in residual water in paleo-oil zones, SO42− from bottom water may also be involved in TSR; therefore, oil reservoirs with bottom water have more SO42− and can produce more H2S than pure oil reservoirs. This phenomenon may be the main cause of the great difference in the H2S concentrations between reservoirs, while gravitational differentiation during late uplift most likely creates differences in H2S concentrations in a single reservoir. Carbon dioxide (CO2), which has a relatively heavy δ13C value (−3.9 to −0.3‰), may be the combined result of TSR, the balance between CO2 and inorganic fluid systems, and carbonate decomposition. 相似文献
106.
The hydrogen sulfide rich waters of the Black Sea pose a potential danger for the surrounding land regions. The impact of
an asteroid exceeding tens of meters in size may cause both a tsunami wave and a catastrophic poisonous gas release in the
atmosphere. Some effects of this last phenomenon on the Southern Black Sea coastal regions are evaluated in this paper. The
initial surface area of the poisonous cloud depends on asteroid size. The initial thickness of the cloud depends, in addition,
on sea depth at impact location. The wind speed plays an important role in H2S cloud dynamics. At 10 m/s wind speed, the cloud margins reach 185 km from the impact location in about 3 h. The maximum
distance traveled by the hydrogen sulfide cloud increases by increasing the asteroid size and wind speed. The influence of
the impact position on the distance traveled by hydrogen sulfide clouds is rather weak, as long as the seawater depth does
not change significantly. The land surface area covered by the H2S cloud generated by a 1,000 m size asteroid ranges between about 6,400 and 12,000 km2. This may affect up to 3,000,000 people. When a 250 m size asteroid is considered, the covered land surface area ranges between
about 1,400 and 2,100 km2 and up to 120,000 people may be affected. In case of a 70 m size asteroid, the cloud covers up to 280 km2 of land. This may affect up to about 70,000 people. These evaluations do not include the population of the towns on or near
the seashore. A simple methodology to estimate the environmental risks of the potential asteroid impact was proposed. Sites
less than 160 km from the impact place are at risk. 相似文献
107.
108.
以天津汉沽盐场高镁卤水为研究对象,分析其成色原因,建立了过氧化氢氧化-氢氧化锆吸附联合脱色工艺,分别考察了脱色剂用量、温度、pH值等因素对卤水色度、CODCr及镁离子损失率的影响,确定了最佳的脱色工艺条件:用卤水处理量1%(体积比)的过氧化氢于室温下将卤水氧化2 h后,在pH值为2~3的条件下经氢氧化锆吸附脱色40 min,氢氧化锆用量为60 g/L。在此条件下,卤水色度及CODCr去除率分别可达99%和85%,镁离子的损失率可控制在1%以下,均高于目前使用的工艺方法。吸附剂氢氧化锆经脱附后可循环使用,大大降低了工艺运行成本。 相似文献
109.
During several campaigns focused on prominences we have obtained coordinated spectral observations from the ground and from
space. The SOHO/SUMER spectrometer allows us to observe, among others, the whole Lyman series of hydrogen, while the Hα line was observed by the MSDP spectrograph at the VTT. For the Lyman lines, non-LTE radiative-transfer computations have
shown the importance of the optical thickness of the prominence – corona transition region (PCTR) and its relation to the
magnetic field orientation for the explanation of the observed line profiles. Moreover, Heinzel, Anzer, and Gunár (2005, Astron. Astrophys.
442, 331) developed a 2D magnetostatic model of prominence fine structures that demonstrates how the shapes of Lyman lines vary,
depending on the orientation of the magnetic field with respect to the line of sight. To support this result observationally,
we focus here on a round-shaped filament observed during three days as it was crossing the limb. The Lyman profiles observed
on the limb are different from day to day. We interpret these differences as being due to the change of orientation of the
prominence axis (and therefore the magnetic field direction) with respect to the line of sight. The Lyman lines are more reversed
if the line of sight is across the prominence axis as compared to the case when it is aligned along its axis. 相似文献
110.