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171.
Optimum reaction time, performance and exhaust emissions of biodiesel produced by microwave irradiation 总被引:3,自引:3,他引:0
A. A. Refaat S. T. El Sheltawy K. U. Sadek 《International Journal of Environmental Science and Technology》2008,5(3):315-322
While transesterification is well established, there remain considerable inefficiencies in existing transesterification processes. In this study an alternative energy stimulant, “microwave irradiation” was used for the production of the alternative energy source, biodiesel. The optimum parametric conditions obtained from the conventional technique were applied using microwave irradiation in order to compare both systems. The results showed that application of radio frequency microwave energy offers a fast, easy route to this valuable biofuel with advantages of enhancing the reaction rate and improving the separation process. The methodology allows for the use of high free fatty acid content feedstock, including used cooking oil; hence it helps to reduce the cost of production which constitutes a major hurdle towards widespread commercialization of biodiesel. The study also showed that the optimum reaction time for microwave-enhanced biodiesel production should be highly respected. Exceeding the optimum reaction time will lead to deterioration of both biodiesel yield and purity. This paper also reported the performance and exhaust emissions from a diesel engine when fuelled with a petroleum diesel fuel and two different biodiesel fuels; one obtained by the conventional technique and the other by microwave irradiation. It was concluded that microwave-enhanced biodiesel is not, at least, inferior to that produced by the conventional technique. 相似文献
172.
Modification of thermal and oxidative properties of biodiesel produced from vegetable oils 总被引:1,自引:1,他引:0
G. El Diwani Ph.D. S. El Rafie Ph.D. 《International Journal of Environmental Science and Technology》2008,5(3):391-400
Trans esterification of three vegetable oils, sunflower oil, linseed oil and mixed oils as; sunflower-soyabean and olein were carried out using methanol, and potasium hydroxide as catalyst. The methyl esters of the corresponding oils were separated from the crude glycerol and characterized by physical-chemical methods to evaluate their thermal properties. This methods are determination of densities, cloud points, pour points, flash points, kinematic viscosities, hydrogen/carbon ratios, sulfur contents, ash contents and triglycerides. The physico-chemical characteristic of biodiesel treated with ozone showed improvement of pour point and flash point indicating higher degree of safety for fuel. Methyl esters mixed with their corresponding ozonated oil were subjected to comparison and evaluation for their thermal properties by the thermo gravimetric analysis differential thermal analysis from which the calculated heat of enthalpy and comparison with the heat of conventional diesel. The results showed that the oxygen content of biodiesel samples treated with ozone increased weight % and resulted in more extensive chemical reaction, promoted combustion characteristics and less carbon residue was produced. Gas chromatography appeared more suitable to address the problem of determining/verifying biodiesel methyl ester and showed that methyl ester content was impurity free. Ultra violet-detection was used for rapid quantization of triglycerols. From the analyses performed biodiesel treated with ozone modified the thermal and oxidative stability shown by the high combustion efficiency indicated by the high heat of enthalpy and reducing the emission of particulate matter. 相似文献
173.
Safae Berrah El Kheir Jamal Oubbih Nadia Saidi Abdelhak Bouabdli 《Arabian Journal of Geosciences》2008,1(2):87-95
Contaminated soils and mine tailings pose major environmental and agricultural problems worldwide. These problems may be partially
solved by an emerging new technology: phytoremediation. This technique uses plants to extract soil contaminants from the ground.
Thlaspi caerulescens is known to accumulate in their tissues several heavy metals from soil and aerial deposition. This study was conducted to
screen plants growing on a contaminated site to determine their potential for metal accumulation. Seeds of T. caerulescens metallicolous have been collected in the vicinity of F.T. Laurent le Minier in the Pb–Zn mining district of les Malines (North
of Montpellier, Southern France), and seeds of T. caerulescens non-metallicolous were sampled on Larzac Plateau (North of Montpellier, Southern France). Soil substrates were collected
from a mine site of Mibladen and Zaida (West, Morroco). Cultivated plant and surface soil samples were analyzed for zinc,
lead, and cadmium concentrations by inductively coupled plasma mass spectrometry. A non-metallicolous (NM) ecotype of T. caerulescens and a metallicolous (M) ecotype are compared for Pb, Cd, and Zn accumulation in shoot and root in five metal-contaminated
soils and one uncontaminated soil. The growth of individuals from uncontaminated soil was greater than that of individuals
from metal-contaminated soils. The NM populations had markedly higher root/shoot ratio compared to M populations. The results
indicate that both ecotypes of T. caerulescens are highly tolerant of zinc and Cd. Ecotype NM had constitutively higher Zn uptake capacity than the M ecotype. T. caerulescens species accumulate higher amount of Zn and Cd in their tissues in polluted soil and, in both of the two ecotypes, the root
Pb concentrations were much greater than those of the shoot Pb contents. From both uncontaminated and metal-contaminated soils,
we conclude that T. caerulescens are interesting material for phytoremediation of zinc and cadmium. 相似文献
174.
A. El Mandour F. El Yaouti Y. Fakir Y. Zarhloule J. Benavente 《Environmental Geology》2008,54(3):491-503
The Bou-Areg plain in the Mediterranean coast at the North-eastern of Morocco is characterized by a semi-arid climate. The
aquifer consists of two sedimentary formations of Plio-quaternary age: the upper formation of fine silts and the lower one
of coarse silts with sand and gravels. The aquifer is underlain by marly bedrock of Miocene age that dips toward the coastal
lagoon of Bou-Areg. The hydrodynamic characteristics vary between 10−4 and 10−3 m/s; and transmissivities range between 10−4 and 10−1 m2/s. The general direction of flow is SW to NE, toward the lagoon. The aquifer is crossed by the river Selouane, which also
ends in the lagoon. The groundwater is characterized by a high salinity that can reach 7.5 g/l. The highest values are observed
in the upstream and in the downstream sectors of the aquifer. The temporal evolution of the physico-chemical parameters depends
on the climatic conditions and piezometric variations. The analysis of the spatio-temporal distribution of the physico-chemical
parameters suggests different sources of groundwater salinization: the seawater intrusion, the influence of marly gypsum-bearing
terrains, and the influence of anthropogenic products as the agricultural fertilizers, which cause great nitrate concentrations
that vary between 80 and 140 mg/l. 相似文献
175.
Groundwater of Egypt: “an environmental overview” 总被引:1,自引:0,他引:1
Although Egypt has the great Nile River, which is the main supply of water, Egypt’s water is limited to 55.5 billion m3 per annum. Owing to the rapid growth of the population and the increasing consumption of water in agriculture, industry,
domestic use, etc., it is expected that Egypt will rely to some extent on groundwater to develop the new projects such as
Tushka in Upper Egypt and East Oweinat. Issues related to groundwater in Egypt are identified with the common geological features
associated with formation of the aquifers and demonstrating the location of the main resources of groundwater, followed by
the main objective of this paper, which is addressing the environmental issues related to groundwater in Egypt. Several studies
have been reviewed and personal communication made with the authorities to introduce this work and provide an overview of
the groundwater quality problems in Egypt with examples from different parts of the country. 相似文献
176.
Mohamed El Wartiti Amina Malaki Mohamed Zahraoui Abdelilah El Ghannouchi Felice Di Gregorio 《Environmental Geology》2008,55(2):415-422
Across the northwestern Tabular Middle Atlas of Morocco there are many examples of landscapes, rocks and fossils that provide
key evidence of a particular moment or period in Earth history. Such Earth heritage sites are important for educating the
general public in environmental matters. They also serve as tools for demonstrating sustainable development and for illustrating
methods of site conservation as well as remembering that rocks, minerals, fossils, soils, landforms form an integral part
of the natural world. The significance of certain sites for aesthetic or tourism reasons is obvious. There are numerous geosites,
which could contribute to effective exploitation of geotourism, often in conjunction with ecotourism. The strategy employed
to such sites involves close consultation with all communities in the vicinity of the respective geosite and is not only aimed
at tourism and education, but also at sustainable improvement of the infrastructure of the people of this area. Geological
heritage sites, properly managed, can generate employment and new economic activities, especially in regions in need of new
or additional sources of income. 相似文献
177.
The effects of dry summer ambient temperature on some physiological and productive responses were studied in an exotic European breed (Holstein–Friesian) and a local zebu breed (Butana ecotype) of cattle in Sudan. Rectal temperature and respiration rate were positively correlated, and dry matter intake and milk yield were negatively correlated with variation in ambient temperature. However, significant adverse effects on high ambient temperature were only observed in the exotic breed. 相似文献
178.
Electron microprobe analyses of small chlorite grains (10–20 μm width) in diagenetically altered rocks from three deep wells
and a series of outcrop samples ranging in maximum age from 4 to 1300 Ma show an increasingly smaller range in grain-to-grain
composition as a function of the average age of the specimens in a series. The scatter of composition in a sample in each
series changes little with depth despite present day, or estimated maximum temperature differences of 70° C to 100° C from
top to bottom. Comparison of these chlorite compositions with those published for geothermal and metamorphic rocks formed
under conditions of 300–450° C indicates that the homogeneity of chlorite composition is a function of both the temperature
of equilibration and its duration. Apparently total homogenization of Fe/(Fe+Mg), Al/(Al+Mg+Fe) content will occur after 1010 years at low temperatures. Simple calculations indicate that a slow process such as solid state diffusion could be responsible
for the eventual homogenization of mineral grain composition to reach chemical equilibrium after phase equilibrium has been
reached. 相似文献
179.
180.
Arid to semi-arid regions are characterized by low levels of surface water and low annual precipitation (generally <350 mm/year). In such areas, groundwater must be used to meet all the needs of the population for water. As a consequence, careful management is required to ensure the sustainability of this scarce resource in response to the demands of urban centers, industry, agriculture, and tourism. The concept of the aquifer recharge rate is particularly useful in the quantification of these groundwater resources and can be used to form the basis of a decision support system. This study determined the potential recharge rate in the Haouz aquifer using a multi-criteria analysis that included both the major and minor factors influencing the rate of infiltration of water into the aquifer. The analysis was based on the use of a geographical information system supported by remote sensing techniques to develop thematic data layers. These layers were then used to describe the spatial variation of the factors influencing the recharge rate of the aquifer and were subsequently integrated and analyzed to derive the spatial distribution of the potential recharge. This approach was used to classify the Haouz Plain (Morocco) into three different zones with respect to the recharge rate, with recharge rates ranging from 3.5 to 18.2 %. 相似文献