全文获取类型
收费全文 | 97篇 |
免费 | 0篇 |
专业分类
大气科学 | 3篇 |
地球物理 | 29篇 |
地质学 | 52篇 |
海洋学 | 3篇 |
天文学 | 6篇 |
自然地理 | 4篇 |
出版年
2023年 | 2篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 1篇 |
2014年 | 6篇 |
2013年 | 9篇 |
2012年 | 5篇 |
2011年 | 6篇 |
2010年 | 6篇 |
2009年 | 1篇 |
2008年 | 1篇 |
2007年 | 2篇 |
2005年 | 2篇 |
2004年 | 5篇 |
2003年 | 1篇 |
2002年 | 2篇 |
2001年 | 3篇 |
1999年 | 6篇 |
1998年 | 2篇 |
1997年 | 5篇 |
1995年 | 1篇 |
1989年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1979年 | 1篇 |
1978年 | 9篇 |
1976年 | 1篇 |
1973年 | 4篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1960年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有97条查询结果,搜索用时 15 毫秒
81.
Summary The article first describes in chronological order the observations on the propagation of radio waves during the solar eclipses, and the development of the conflicting results on the similar transmissions of radio signals. The general theory of the absorption of radio waves in the ionosphere is briefly described and therefrom a method is derived to estimate the variation of the absorption of obliquely incident radio waves during a solar eclipse.The variation of field-strength can be studied in terms of the relationship between the vertical incident equivalent frequency of the signals and the critical frequencies of the ionospheric layers at the regions of reflection. The total absorption of radio waves consists of the non-deviative absorption in theD region and the deviative absorption in the higher layers of the ionosphere. During the eclipse, theD region absorption decreases in phase with the progress of the eclipse, but the variation of deviative absorption may differ in each observation. The deviative absorption is large when the equivalent frequency is close to the critical frequency of the layer reflecting the waves or of the layer just penetrated by the waves. The changes in the deviative absorption during an eclipse can be estimated on the basis of the variation of the critical frequencies of the ionospheric layers. The resultant changes in the total absorption during a solar eclipse may thus be estimated. The different types of field strength variation expected during an eclipse are given.The observations of the vertical incident absorption of radio waves and the field strength variations of obliquely incident continuous wave radio signals during the solar eclipse are described and the changes are explained on the basis of the above theory. 相似文献
82.
83.
Ankam Durga Prasad Lori Rastogi Shanmugam Thangavel Kulamani Dash 《Geostandards and Geoanalytical Research》2023,47(2):403-413
An acid assisted microwave-based method for the complete dissolution of bauxite using mixture of H2SO4, H3PO4 and HF acids in a single step was developed for the determination of various analytes (Al2O3, Fe2O3, SiO2, TiO2, Cr2O3, MgO, MnO and V2O5) using ICP-AES. The method was validated with respect to ruggedness, linearity, trueness, precision, limit of detection (LOD), limit of quantification (LOQ), working range and measurement uncertainties by analysing a bauxite reference material (Alcan BXT-12) and four certified reference materials (IPT-131, BXBA-4, NIST SRM 600, NIST SRM 697). The expanded uncertainties obtained for Al2O3 (40.0%), Fe2O3 (17.0%), SiO2 (20.3%), TiO2 (1.31%), Cr2O3 (0.024%), MgO (0.05), MnO (0.013), and V2O5 (0.60%), were 0.80, 0.40, 0.50, 0.033, 0.0008, 0.002, 0.0007 and 0.002 respectively, which are fit for the intended use to characterise bauxite. The developed method was also evaluated through participation in an interlaboratory comparison exercise organised by the Jawaharlal Nehru Aluminium Research Development and Design Centre (JNARDDC), Nagpur, India, using bauxite sample (BXT-JNA), with satisfactory z-scores achieved. 相似文献
84.
Sumer Chopra Dinesh Kumar B. K. Rastogi Pallabee Choudhury R. B. S. Yadav 《Natural Hazards》2012,60(2):517-540
In this study, the modified stochastic method based on dynamic corner frequency has been used for the simulation of strong
ground motions in Gujarat region. The earthquake-generating faults have been identified in the Gujarat region on the basis
of past seismicity of the region. In all, 19 probable faults have been identified with 12 in Kachchh region, 5 in Saurashtra
and 2 in Mainland Gujarat region. The maximum magnitude has been assigned to each fault based on the regional tectonic environment
and past seismicity. The strong ground motions from these identified sources have been estimated at numerous points distributed
all over Gujarat region on a grid. The peak ground acceleration (PGA) values have been extracted from the accelerograms and
contoured. The spatial distribution of maximum of 19 PGA values at every grid point have been described and discussed. The
ground motions at the surface of 32 important cities of the Gujarat have been estimated by incorporating the site amplification
functions. The site amplification functions are obtained using the local earthquake data. These cities are located on various
types of geological formations. We note that the site amplification functions have modified the character of the records and
amplified the acceleration values at almost all the sites. The Kachchh region can expect surface accelerations between 400
and 800 cm/s2, Saurashtra between 100 and 200 cm/s2 and Mainland less than 50 cm/s2 from a future large earthquake. The obtained results are useful for disaster mitigation measures, strengthening the existing
built environment and design of structures in the region. 相似文献
85.
Archana Das Falguni Bhattacharya B K Rastogi Gaurav Chauhan Mamata Ngangom M G Thakkar 《Journal of Earth System Science》2016,125(6):1119-1138
Dryland rivers, dominated by short-lived, localised and highly variable flow due to discrete precipitation events, have characteristic preservation potential, which serves as suitable archives towards understanding the climate–tectonic coupling. In the present study, we have investigated the fluvial records of a major, southerly-draining river – the Rukmawati River in the dryland terrain of southern Kachchh, in western India. The sediment records along the bedrock rivers of Kachchh register imprints of the Indian summer monsoon (ISM), which is the major source of moisture to the fluvial system in western India. The Rukmawati River originates from the Katrol Hill Range in the north and flows towards the south, into the Gulf of Kachchh. The field stratigraphy, sedimentology, along with the optical chronology suggests that a braided-meandering system existed during 37 ka period due to an overall strengthened monsoon. A gradual decline in the monsoon strength with fluctuation facilitated the development of a braided channel system between 20 and 15 ka. A renewed phase of strengthened monsoon with seasonality after around 15 ka which persisted until around 11 ka, is implicated in the development of floodplain sequences. Two zones of relatively high bedrock uplift are identified based on the geomorphometry and morphology of the fluvial landform. These zones are located in the vicinity of the North Katrol Hill Fault (NKHF) and South Katrol Hill Fault (SKHF). Geomorphic expression of high bedrock uplift is manifested by the development of beveled bedrock prior to or around 20 ka during weak monsoon. The study suggests that the terrain in the vicinity of NKHF and SKHF is uplifting at around 0.8 and >0.3 mm/a, respectively. Simultaneously, the incision in the Rukmawati River basin, post 11 ka, is ascribed to have occurred due to lowered sea level during the LGM and early Holocene period. 相似文献
86.
The precipitation events (n = 91), collected for 3 years (2000–2002) during the period of SW-monsoon (Jun–Aug) from an urban
site (Ahmedabad, 23.0°N, 72.6°E) of a semi-arid region in western India, are found to exhibit characteristic differences in
terms of their solute contents. The low solute (<700 μeq L−1) events are either marked by heavy precipitation amount or successive events collected during an extended rain spell; whereas
light precipitation events occurring after antecedent dry period are characterized by high solutes (>700 μeq L−1). The ionic composition of low solute events show large variability due to varying contribution of anthropogenic species
(: 1%–74%; : 1%–25%; and : 8%–68%) to the respective ion balance. In high solute events, ionic abundances are dominated by mineral dust (Ca2+ and ) and sea-salts (Na+ and Cl−). These differences are also reflected in the pH of low solute events (range: 5.2–7.4, VWM: 6.4) and high solute events (range:
6.6–8.2, VWM: 7.3). The comparison of Ca2+/Na+ and nss- ratios (on equivalent basis) in rain and aerosols suggests that the ionic composition of high solute events is influenced
by below-cloud scavenging; whereas evidence for in-cloud scavenging is significantly reflected in low solute events. The annual
wet-deposition fluxes of and are 330 and 480 mg m−2 y−1, respectively, in contrast to their corresponding dry-deposition fluxes (14 and 160 mg m−2 y−1); whereas wet and dry removal of Ca2+, Mg2+ and are comparable. 相似文献
87.
This paper describes the morphology of the equatorial electrojet (EEJ) along 45°W longitude in east Brazil, where the ground
magnetic (dip) equator is associated with the largest declination in the world. Daily range of the horizontal field (ΔH), as expected, was largest at the station in the chain closest to the dip equator, Sao Luiz (inclination −0.25°S). ΔZ was largest positive at Eusebio (inclination 9.34°S) and largest negative at Belem (inclination 7.06°N); both near the fringe
of EEJ belt. ΔZ at Sao Luiz during the daytime was unexpectedly large negative in-spite of a small dip and also located south of the dip
equator where ΔZ should be positive. Center of EEJ was found to be shifted southward of the dip equator by about 1° in latitude. During southern
summer, ΔY started decreasing from 00 h and reached a minimum value in the afternoon, an abnormal feature not discussed for any station
so far. The mid-day value of the direction of ΔH vector was 22°–24°W compared to the declination of 19°–21°W in the region. 相似文献
88.
89.
Malkiat Singh H S Gurm M R Deshpande R G Rastogi G Sethia A R Jain A V Janve R K Rai V M Patwari B S Subbarao 《Journal of Earth System Science》1978,87(3):47-55
Radio beacon from ATS-6 at 140 MHz was used to measure the changes in the polarization angle (Faraday rotation) at Bombay,
Rajkot, Ahmedabad, Udaipur and Patiala during October 1975 to July 1976. In this paper, results of diurnal, seasonal and latitudinal
variations in total electron content (TEC) derived from these measurements are reported. The amplitude of diurnal peak is
found to be higher at Rajkot, Ahmedabad and Udaipur as compared to that at Patiala or Bombay, indicating that the peak of
Appleton anomaly in the latitudinal variation of TEC was close to the latitude of Ahmedabad. The diurnal maximum of TEC occurs
around the same time during summer and winter months. The peak electron content shows a semiannual variation at all the stations
with large values in equinoxes as compared to winter and summer. The TEC at Bombay shows a seasonal anamoly with high values
in winter as compared to summer. The paper describes the development of latitudinal anomaly with the time of the day for different
seasons. This anomaly is maximum during 1000 to 1800 LT and is located between 12° and 14° N (dip latitude) in summer and
equinoxes and at about 10°N in winter. 相似文献
90.
R G Rastogi 《Journal of Earth System Science》1978,87(3):57-60
It is shown that the storm sudden commencement (SSC) inH field at low latitude station consists of only a positive excursion when the interplanetary shock due to the solar plasma
impinging on the magnetosphere is associated with a southward excursion of the interplanetary magnetic field (IMF). When the
signature of SSC at low latitude station consists of a preliminary negative excursion preceding the main positive excursion
of theH field, the solar plasma causing the compression is associated with a northward excursion of the IMF. It is suggested that
the signature of SSC(H) at equatorial stations is the result of combined effect of the compression of magnetosphere by the solar plasma as well
as due to the electric field effects associated with the velocity of the solar plasma (v) interacting with the northward component (Bz) of the interplanetary field (i.e.,E =−v
x Bz). 相似文献