全文获取类型
收费全文 | 681篇 |
免费 | 19篇 |
国内免费 | 8篇 |
专业分类
测绘学 | 43篇 |
大气科学 | 26篇 |
地球物理 | 166篇 |
地质学 | 249篇 |
海洋学 | 17篇 |
天文学 | 171篇 |
综合类 | 14篇 |
自然地理 | 22篇 |
出版年
2022年 | 17篇 |
2021年 | 18篇 |
2020年 | 24篇 |
2019年 | 18篇 |
2018年 | 40篇 |
2017年 | 35篇 |
2016年 | 33篇 |
2015年 | 39篇 |
2014年 | 42篇 |
2013年 | 37篇 |
2012年 | 40篇 |
2011年 | 28篇 |
2010年 | 27篇 |
2009年 | 27篇 |
2008年 | 19篇 |
2007年 | 19篇 |
2006年 | 21篇 |
2005年 | 5篇 |
2004年 | 9篇 |
2003年 | 7篇 |
2002年 | 9篇 |
2001年 | 6篇 |
2000年 | 12篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 9篇 |
1995年 | 6篇 |
1994年 | 7篇 |
1993年 | 7篇 |
1989年 | 3篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 6篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1971年 | 7篇 |
1970年 | 4篇 |
排序方式: 共有708条查询结果,搜索用时 0 毫秒
591.
The impact assessment of molasses‐based distillery‐effluent irrigation on groundwater quality around village Gajraula in the district of Jyotiba Phule Nagar, Uttar Pradesh, India was studied by sampling groundwater on monthly intervals consecutively for summer, winter and monsoon seasons during 2006–2007 and water quality parameters, viz. pH, electrical conductivity (EC), chloride (Cl?), sulphate (SO), nitrate (NO), chemical oxygen demand (COD), total solids (TS), total dissolved solids (TDS), sodium (Na+), potassium (K+), calcium (Ca2+), magnesium (Mg2+), zinc (Zn2+), iron (Fe3+), and total coliforms (TC) were monitored. Results depicted that the values of all parameters decreased with increasing depth of water table. Sulphate, nitrate and potassium contents were maximal in agricultural site during monsoon while EC, Cl?, TS, TDS, Na+, Ca2+, Mg2+, Zn, and Fe were maximal in industrial sites during summer. Groundwater samples of residential site harboured maximum coliforms especially during monsoon, highlighting threat to groundwater. Significant positive correlation matrix between coliforms with nitrate, sulphate and potassium ions explained their survival on these nutrients. To overcome this, important measures emphasizing improvement in effluent treatment technology matching site‐specific characteristics are recommended for eco‐friendly ferti‐irrigation. 相似文献
592.
Mallick Javed Islam Abu Reza Md. Towfiqul Ghose Bonosri Islam H. M. Touhidul Rana Yousuf Hu Zhenghua Bhat Shakeel Ahmed Pal Subodh Chandra Ismail Zulhilmi Bin 《Theoretical and Applied Climatology》2022,147(1-2):307-324
Theoretical and Applied Climatology - The rise in the frequency and magnitude of extreme temperature phenomena across the globe has led to the recurrent incidence of global climate hazards, which... 相似文献
593.
This paper presents tsunami intensity mapping and damage patterns along the surveyed coast of Tamilnadu (India) of the deadly
Indian Ocean tsunami of December 26, 2004. The tsunami caused severe damage and claimed many victims in the coastal areas
of eleven countries bordering the Indian Ocean. A twelve-stage tsunami intensity scale proposed by Papadopoulos and Imamura
(2001) was followed to assign the intensity at the visited localities. Along the coast of the Indian mainland, tsunami damage
sustained exclusively. Most severe damage was observed in Nagapattinam Beach, Nabiyarnagar, Vellaipalyam, and the Nagapattinam
Port of Nagapattinum District on the east coast and Keelamanakudy village of Kanyakumari District on the western coast of
Tamilnadu. The maximum assigned tsunami intensity was X+ at these localities. Minimum intensity V+ was received along the coast of Thanjavur, Puddukkotai and Ramnathpuram Districts in Palk Strait. The general observation
reported by many people was that the first arrival was a tsunami crest. The largest tsunami waves were first arrivals on the
eastern coast and the second arrivals on the western coast. Along the coast, people were unaware of the tsunami, and no anomalous
behavior of ocean animals was reported. Good correlation was observed between the severity of damage and the presence of shadow
zone of Sri Lanka, reflected waves from Sri Lanka and the Maldives Islands, variation in the width of the continental shelf,
elevation of the coast and the presence of breakwaters. The presence of medu (naturally elevated landmass very close to the
sea shore and elongated parallel to the coast) reduced the impact of the tsunami on the built environment. 相似文献
594.
Chandra S Rai Shiv K Sharma David W Muenow Dean W Matson Charles D Byers 《Geochimica et cosmochimica acta》1983,47(5):953-958
The temperature dependence of carbon dioxide solubility in glasses of diopside composition, quenched from 20 kbar, has been investigated using a combination of high-temperature mass spectrometry and Raman spectroscopy.CO2-charged diopside glasses were synthesized in a piston-cylinder apparatus. Because of diffusion of hydrogen through the platinum capsules, significant amounts of H2O, CH4 and CO were detected along with CO: in the diopside glasses. All three carbon species show a bimodal release pattern in the mass pyrograms. The CO2 solubility shows a linear and negative temperature dependence. We do not observe any maxima in the solubility curve as was reported previously (Mysen and virgo, 1980a).None of the additional bands observed in Raman spectra of CO2-charged diopside glasses compared to those in the spectrum of diopside glass can be assigned to molecular CO2. These bands are caused by CO?23 ions and indicate that the physical solubility of molecular carbon dioxide is negligible. The bimodal release pattern observed for CO2 in the mass pyrograms, is consistent with the Raman data which strongly suggests that CO?23 ions are present in at least two distinct sites in the glass. 相似文献
595.
Ramesh Chandra Rajmal Jain Wahab Uddin Keiji Yoshimura Takeo Kosugi Taro Sakao Anita Joshi M. R. Deshpande 《Solar physics》2006,239(1-2):239-256
We present Hα observations from ARIES (Nainital) of a compact and impulsive solar flare that occurred on March 10, 2001 and
which was associated with a CME. We have also analyzed HXT, SXT/Yohkoh observations as well as radio observations from the Nobeyama Radio Observatory to derive the energetics and dynamics of this
impulsive flare. We coalign the Hα, SXR, HXR, MW, and magnetogram images within the instrumental spatial-resolution limit.
We detect a single HXR source in this flare, which is found spatially associated with one of the Hα bright kernels. The unusual
feature of HXR and Hα sources, observed for the first time, is the rotation during the impulsive phase in a clockwise direction.
We propose that the rotation may be due to asymmetric progress of the magnetic reconnection site or may be due to the change
of the peak point of the electric field. In MW emission we found two sources. The main source is at the main flare site and
another is in the southwest direction. It appears that the remote source is formed by the impact of accelerated energetic
electrons from the main flare site. From the spatial correlation of multiwavelength images of the different sources, we conclude
that this flare has a three-legged structure. 相似文献
596.
This article presents a new approach for the implementation of a planar-free surface boundary condition. It is based on a
vertical grid-size reduction above the free surface during the explicit computation of a free surface boundary condition.
This technique is very much similar to the well-known stress imaging technique. VGR-stress imaging technique name is proposed
for this new free surface boundary condition (VGR stands for ‘vertical grid-size reduction’). To study the performance of
the proposed VGR-stress imaging technique, it was implemented in a newly developed second order accurate in time and fourth-order
accurate in space (2, 4) staggered grid SH-wave finite-difference (FD) algorithm with variable grid size. It was confirmed
that the effective thickness (ETH) of first soil layer becomes less by one-half of vertical grid size than the assigned thickness
(ATH), if stress imaging technique is used as a free surface boundary condition. The qualitative and quantitative results
of various numerical experiments revealed that the proposed VGR-stress imaging technique is better than the stress imaging
technique since it is free from the thickness discrepancy arising due to the use of images of stress components across the
free surface. On the basis of iterative numerical experiments, it was confirmed that the stability condition for this FD scheme
with variable grid size is
It was also inferred that at least five to six grid points per shortest wavelength are required to avoid the grid dispersion.
The maximum grid-spacing ratio up to 12.5 or even more did not affect the accuracy of (2,4) SH-wave algorithm. The obtained
reduction of 10.46 and 5.38 folds in the requirement of computational memory and time for a particular basin-edge model, as
compared with the homogeneous grid size, reflects the efficacy of the new FD algorithm. 相似文献
597.
Robert Barouki Manolis Kogevinas Karine Audouze Kristine Belesova Ake Bergman Linda Birnbaum Sandra Boekhold Sebastien Denys Celine Desseille Elina Drakvik Howard Frumkin Jeanne Garric Delphine Destoumieux-Garzon Andrew Haines Anke Huss Genon Jensen Spyros Karakitsios Jana Klanova Iida-Maria Koskela Francine Laden Paolo Vineis 《Chemie der Erde / Geochemistry》2011
The outbreak of COVID-19 raised numerous questions on the interactions between the occurrence of new infections, the environment, climate and health. The European Union requested the H2020 HERA project which aims at setting priorities in research on environment, climate and health, to identify relevant research needs regarding Covid-19. The emergence and spread of SARS-CoV-2 appears to be related to urbanization, habitat destruction, live animal trade, intensive livestock farming and global travel. The contribution of climate and air pollution requires additional studies. Importantly, the severity of COVID-19 depends on the interactions between the viral infection, ageing and chronic diseases such as metabolic, respiratory and cardiovascular diseases and obesity which are themselves influenced by environmental stressors. The mechanisms of these interactions deserve additional scrutiny. Both the pandemic and the social response to the disease have elicited an array of behavioural and societal changes that may remain long after the pandemic and that may have long term health effects including on mental health. Recovery plans are currently being discussed or implemented and the environmental and health impacts of those plans are not clearly foreseen. Clearly, COVID-19 will have a long-lasting impact on the environmental health field and will open new research perspectives and policy needs. 相似文献
598.
Robert Barouki Manolis Kogevinas Karine Audouze Kristine Belesova Ake Bergman Linda Birnbaum Sandra Boekhold Sebastien Denys Celine Desseille Elina Drakvik Howard Frumkin Jeanne Garric Delphine Destoumieux-Garzon Andrew Haines Anke Huss Genon Jensen Spyros Karakitsios Jana Klanova Paolo Vineis 《Chemie der Erde / Geochemistry》2013
The outbreak of COVID-19 raised numerous questions on the interactions between the occurrence of new infections, the environment, climate and health. The European Union requested the H2020 HERA project which aims at setting priorities in research on environment, climate and health, to identify relevant research needs regarding Covid-19. The emergence and spread of SARS-CoV-2 appears to be related to urbanization, habitat destruction, live animal trade, intensive livestock farming and global travel. The contribution of climate and air pollution requires additional studies. Importantly, the severity of COVID-19 depends on the interactions between the viral infection, ageing and chronic diseases such as metabolic, respiratory and cardiovascular diseases and obesity which are themselves influenced by environmental stressors. The mechanisms of these interactions deserve additional scrutiny. Both the pandemic and the social response to the disease have elicited an array of behavioural and societal changes that may remain long after the pandemic and that may have long term health effects including on mental health. Recovery plans are currently being discussed or implemented and the environmental and health impacts of those plans are not clearly foreseen. Clearly, COVID-19 will have a long-lasting impact on the environmental health field and will open new research perspectives and policy needs. 相似文献
599.
Margarita Safonova Joice Mathew Rekhesh Mohan A. G. Sreejith Jayant Murthy Noah Brosch Norbert Kappelmann Arpit Sharma Rahul Narayan 《Astrophysics and Space Science》2014,353(2):329-346
Space astronomy in the last 40 years has largely been done from spacecraft in low Earth orbit (LEO) for which the technology is proven and delivery mechanisms are readily available. However, new opportunities are arising with the surge in commercial aerospace missions. We describe here one such possibility: deploying a small instrument on the Moon. This can be accomplished by flying onboard the Indian entry to the Google Lunar X PRIZE competition, Team Indus mission, which is expected to deliver a nearly 30 kgs of payloads to the Moon, with a rover as its primary payload. We propose to mount a wide-field far-UV (130–180 nm) imaging telescope as a payload on the Team Indus lander. Our baseline operation is a fixed zenith pointing but with the option of a mechanism to allow observations of different attitudes. Pointing towards intermediate ecliptic latitude (50° or above) ensures that the Sun is at least 40° off the line of sight at all times. In this position, the telescope can cover higher galactic latitudes as well as parts of Galactic plane. The scientific objectives of such a prospective are delineated and discussed. 相似文献
600.
We present results from a series of piezometers installed in the foreshore flat and mangrove environments of the Gillman Marshes, South Australia in an interdisciplinary study of the propagation of the ocean tide into the coastal aquifers. A unique feature of the analysis is that all water level records were harmonically analysed so that the behaviour of the four major tidal constituents could be independently examined. The main findings were that: (1) the decay of the groundwater tide in the coastal aquifers was greater than that predicted by the Ferris solution. A theoretical model has been developed and applied to the study site. The model suggests that this behaviour is due to the occurrence of a time delay in the Darcian response in the shelly and muddy sand substrate; (2) when the tide is incident over a gently sloping bank, the time delay in response gives rise to a spiked signal in which high water is confined to a small fraction of the tidal cycle; and (3) at the coastal interface tidal propagation across a sloping bank causes a rise in the water table relative to mean sea level which is proportional to the variance of tidal elevation and inversely proportional to the decay constant of the groundwater tide. The model developed in this study is also applicable to other coastal groundwater systems with tidal influence. 相似文献