全文获取类型
收费全文 | 37216篇 |
免费 | 839篇 |
国内免费 | 332篇 |
专业分类
测绘学 | 1016篇 |
大气科学 | 3253篇 |
地球物理 | 7791篇 |
地质学 | 14104篇 |
海洋学 | 2898篇 |
天文学 | 7146篇 |
综合类 | 156篇 |
自然地理 | 2023篇 |
出版年
2022年 | 210篇 |
2021年 | 397篇 |
2020年 | 395篇 |
2019年 | 374篇 |
2018年 | 987篇 |
2017年 | 990篇 |
2016年 | 1231篇 |
2015年 | 718篇 |
2014年 | 1193篇 |
2013年 | 2019篇 |
2012年 | 1223篇 |
2011年 | 1506篇 |
2010年 | 1397篇 |
2009年 | 1759篇 |
2008年 | 1470篇 |
2007年 | 1402篇 |
2006年 | 1351篇 |
2005年 | 1016篇 |
2004年 | 982篇 |
2003年 | 897篇 |
2002年 | 927篇 |
2001年 | 851篇 |
2000年 | 822篇 |
1999年 | 662篇 |
1998年 | 657篇 |
1997年 | 702篇 |
1996年 | 583篇 |
1995年 | 583篇 |
1994年 | 588篇 |
1993年 | 446篇 |
1992年 | 445篇 |
1991年 | 409篇 |
1990年 | 427篇 |
1989年 | 393篇 |
1988年 | 391篇 |
1987年 | 417篇 |
1986年 | 367篇 |
1985年 | 491篇 |
1984年 | 488篇 |
1983年 | 524篇 |
1982年 | 480篇 |
1981年 | 434篇 |
1980年 | 468篇 |
1979年 | 387篇 |
1978年 | 388篇 |
1977年 | 356篇 |
1976年 | 314篇 |
1975年 | 336篇 |
1974年 | 341篇 |
1973年 | 332篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
The data obtained on melt and fluid inclusions in minerals of granites, metasomatic rocks, and veins with tin ore mineralization
at the Industrial’noe deposit in the southern part of the Omsukchan trough, northeastern Russia, indicate that the melt from
which the quartz of the granites crystallized contained globules of salt melts. Silicate melt inclusions were used to determine
the principal parameters of the magmatic melts that formed the granites, which had temperatures at 760–1020°C, were under
pressures of 0.3–3.6 kbar, and had densities of 2.11–2.60 g/cm3 and water concentrations of 1.7–7.0 wt %. The results obtained on the fluid inclusions testify that the parameters of the
mineral-forming fluids broadly varied and corresponded to temperatures at 920–275°C, pressures 0.1–3.1 kbar, densities of
0.70–1.90 g/cm3, and salinities of 4.0–75.0 wt % equiv. NaCl. Electron microprobe analyses of the glasses of twelve homogenized inclusions
show concentrations of major components typical of an acid magmatic melt (wt %, average): 73.2% SiO2, 15.3% Al2O3, 1.3% FeO, 0.6% CaO, 3.1% Na2O, and 4.5% K2O at elevated concentrations of Cl (up to 0.51 wt %, average 0.31 wt %). The concentrations and distribution of some elements
(Cl, K, Ca, Mn, Fe, Cu, Zn, Pb, As, Br, Rb, Sr, and Sn) in polyphase salt globules in quartz from both the granites and a
mineralized miarolitic cavity in granite were assayed by micro-PIXE (proton-induced X-ray emission). Analyses of eight salt
globules in quartz from the granites point to high concentrations (average, wt %) of Cl (27.5), Fe (9.7), Cu (7.2), Mn (1.1),
Zn (0.66), Pb (0.37) and (average, ppm) As (2020), Rb (1850), Sr (1090), and Br (990). The salt globules in the miarolitic
quartz are rich in (average of 29 globules, wt %) Cl (25.0), Fe (5.4), Mn (1.0), Zn (0.50), Pb (0.24) and (ppm) Rb (810),
Sn (540), and Br (470). The synthesis of all data obtained on melt and fluid inclusions in minerals from the Industrial’noe
deposit suggest that the genesis of the tin ore mineralization was related to the crystallization of acid magmatic melts.
Original Russian Text@ V.B. Naumov, V.S. Kamenetsky, 2006, published in Geokhimiya, 2006, No. 12, pp. 1279–1289. 相似文献
942.
The Tyrell catchment lies on the western margin of the Riverine Province in the south-central Murray Basin, one of Australia’s most important groundwater resources. Groundwater from the shallow, unconfined Pliocene Sands aquifer and the underlying Renmark Group aquifer is saline (total dissolved solids up to 150,000 mg/L) and is Na-Cl-Mg type. There is no systematic change in salinity along hydraulic gradients implying that the aquifers are hydraulically connected and mixing during vertical flow is important. Stable isotopes (18O+2H) and Cl/Br ratios indicate that groundwater is entirely of meteoric origin and salts in this system have largely been derived by evapotranspiration of rainfall with only minor halite dissolution, rock weathering (mainly feldspar dissolution), and ion exchange between Na and Mg on clays. Similarity in chemistry of all groundwater in the catchment implies relative consistency in processes over time, independent of any climatic variation. Groundwater in both the Pliocene Sands and Renmark Group aquifers yield ages of up to 25 ka. The Tyrrell Catchment is arid to semi-arid and has low topography. This has resulted in relatively low recharge rates and hydraulic gradients that have resulted in long groundwater residence times. 相似文献
943.
Yu. V. Plotkina E. B. Sal’nikova A. B. Kotov M. D. Tolkachev M. R. Pavlov 《Petrology》2006,14(2):201-208
The paper reports results obtained by the complex studying of zircon crystals from rocks of various genesis. Zircon is one of the minerals most often used as geochronometers. It also provides genetic information on superimposed processes that is “recorded” in the external and internal morphology of its crystals. This mineral is thoroughly examined to select its unaltered crystals for U-Pb dating by the single-grain method. Zircon grains are selected with the use of optical and electron microscopy and cathodoluminescence. This publication presents the first results obtained by examining zircon by computer microtomography (μCT) and the results of the studying of the external and internal structure by conventional techniques ([optical microscopy and SEM (SE and CL)]. The paper demonstrates the advantages of the application of the μCT techniques to the selection of targets for U-Pb zircon dating: there is no need for the special preparation of the samples and no material is destructed. However, this technique may be not informative enough if the zircon contains inherited core whose density does not differ from the density of the surrounding mineral. 相似文献
944.
The origin of reaction textures in mantle peridotite xenoliths from Sal Island, Cape Verde: the case for “metasomatism” by the host lava 总被引:1,自引:1,他引:1
Cliff S. J. Shaw Florian Heidelbach Donald B. Dingwell 《Contributions to Mineralogy and Petrology》2006,151(6):681-697
Reaction zones around minerals in mantle xenoliths have been reported from many localities worldwide. Interpretations of the origins of these textures fall into two groups: mantle metasomatic reaction or reaction during transport of the xenoliths to the surface. A suite of harzburgitic mantle xenoliths from Sal, Cape Verde show clear evidence of reaction during transport. The reactions resulted in the formation of olivine–clinopyroxene and Si- and alkali-rich glass reaction zones around orthopyroxene and sieve-textured clinopyroxene and sieve textured spinel, both of which are associated with a Si- and alkali-rich glass similar to that in the orthopyroxene reaction zones. Reaction occurred at pressures less than the mantle equilibration pressure and at temperatures close to the liquidus temperature of the host magma. In addition, there is a clear spatial relation of reaction with the host lava: reaction is most intense near the lava/xenolith contact. The residence time of the xenoliths in the host magma, determined from Fe–Mg interdiffusion profiles in olivine, was approximately 4 years. Our results cannot be reconciled with a recent model for the evolution of the mantle below the Cape Verde Archipelago involving mantle metasomatism by kimberlitic melt. We contend that alkali-rich glasses in the Sal xenoliths are not remnants of a kimberlitic melt, but rather they are the result of reaction between the host lava or a similar magma and xenolith minerals, in particular orthopyroxene. The formation of a Si- and alkali-rich glass by host magma–orthopyroxene reaction appears to be a necessary precursor to formation of sieve textured spinel and clinopyroxene. 相似文献
945.
Daily zenith scattered light intensity observations were carried out in the morning twilight hours using home-made UV-visible
spectrometer over the tropical station Pune (18‡31′, 73‡51′) for the years 2000–2003. These observations are obtained in the
spectral range 462–498 nm for the solar zenith angles (SZAs) varying from 87‡ to 91.5‡. An algorithm has been developed to
retrieve vertical profiles of ozone (O3) and nitrogen dioxide (NO2) from ground-based measurements using the Chahine iteration method. This retrieval method has been checked using measured
and recalculated slant column densities (SCDs) and they are found to be well matching. O3 and NO2 vertical profiles have been retrieved using a set of their air mass factors (AMFs) and SCDs measured over a range of 87–91.5‡
SZA during the morning. The vertical profiles obtained by this method are compared with Umkehr profiles and ozonesondes and
they are found to be in good agreement. The bulk of the column density is found near layer 20–25 km. Daily total column densities
(TCDs) of O3 and NO2 along with their stratospheric and tropospheric counterparts are derived using their vertical profiles for the period 2000–2003.
The total column, stratospheric column and tropospheric column amounts of both trace gases are found to be maximum in summer
and minimum in the winter season. Increasing trend is found in column density of NO2 in stratospheric, tropospheric and surface layers, but no trend is observed in O3 columns for above layers during the period 2000–2003 相似文献
946.
The devastating 1999 Marmara and Düzce earthquakes led to a significant increase in the earthquake studies in Turkey in geological,
engineering and financial aspects. Extreme Value Theory (EVT) has a range of applications from stock market changes to natural
disasters like floods and hurricanes. Here EVT is fitted to the ordinary and earthquake reinsurance claims of Turkey. 相似文献
947.
A. B. Yavuz 《Environmental Geology》2006,51(2):211-227
?zmir is the third largest city in Turkey and has being the centre of art, culture, tourism and trade activities throughout the 5,000 years of its history. Natural stones brought from different parts of the world have been widely used for construction of the prestigious buildings, monuments and roads etc., in the past in the city. Renovation of the street pavements and public gathering areas in the city centre has been undertaken by the Metropolitan Municipality in 2000 and continued through the year of 2001. These renovation activities have mainly been carried out in the streets running parallel to the sea shore. Volcanic rocks brought from the Central Anatolia Ankara-Gölba?? (andesites) and Kayseri-?ncesu (tuffs) have been used in the renovation works. These rocks have shown extensive deteriorations within 4 years of their usage between 2001 and 2005 under the influence of different environmental factors. In this study, the deteriorations developed in the recently placed volcanic rocks used as kerb and pavement stones in the city centre of ?zmir in the light of their mineralogical, chemical, physical and mechanical properties, used locations and the environmental factors are presented. 相似文献
948.
949.
A debris flow originating from the Alcamayo River on 10th April 2004 destroyed a part of the town of Aguas Calientes, resulting
in 11 victims, and with serious affects to the tourist flow to the Machupicchu inka citadel. On the same day, as well as in
January and March 2004, other similar phenomena occurred on the Cedrobamba and Leonchayoq Rivers, affecting the railway and
an electrical tower, and disrupting the train service. 相似文献
950.