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991.
M. V. Maya Melena A. Soares Rajesh Agnihotri A. K. Pratihary Supriya Karapurkar Hema Naik S. W. A. Naqvi 《Environmental monitoring and assessment》2011,175(1-4):501-517
Chemical and isotopic (??13C and ??15N) investigation of the Mandovi estuary along the Indian west coast affected strongly by the seasonal monsoon cycle was carried out. The Mandovi estuary is a major waterway for Goa and extensively used for transportation of iron and manganese ore. In addition, with large population centers as well as agricultural fields located on its shores, the estuary is assumed to have been influenced by human activities. Measurements of chemical and isotopic parameters made in the lower part of the estuary during the southwest (SW) monsoon and post-monsoon seasons reveal distinct changes, and it is observed that despite considerable enrichment of macronutrients during the SW monsoon, productivity of the estuary (phytoplankton biomass), as inferred from the chlorophyll-a content, is not as high as expected. This is due to occurrences of high turbidity and cloud cover that limits photosynthetic productivity. The isotopic characterization (C and N isotopes) of suspended organic matter produced/transported during the monsoon and post-monsoon seasons of year 2007 provides a baseline dataset for future isotopic studies in such type of tropical estuaries. 相似文献
992.
Soumya Chatterjee Mridul Chetia Lokendra Singh Buddhadeb Chattopadhyay Siddhartha Datta S. K. Mukhopadhyay 《Environmental monitoring and assessment》2011,178(1-4):361-371
Some wetland plant species are adapted to growing in the areas of higher metal concentrations. Use of such vegetation in remediation of soil and water contaminated with heavy metals is a promising cost-effective alternative to the more established treatment methods. Throughout the year, composite industrial effluents bringing various kinds of heavy metals contaminate our study site, the East Calcutta Wetlands, a Ramsar site at the eastern fringe of Kolkata city (formerly Calcutta), India. In the present study, possible measures for remediation of contaminated soil and water (with elements namely, Ca, Cr, Cu, Pb, Zn, Mn, and Fe) of the ecosystem had been investigated. Ten common regional wetland plant species were selected to study their efficiency and diversity in metal uptake and accumulation. Results showed that Bermuda grass (Cynodon dactylon) had the highest total Cr concentration (6,601 ± 33 mg kg???1 dw). The extent of accumulation of various elements in ten common wetland plants of the study sites was: Pb (4.4?C57 mg kg???1 dw), Cu (6.2?C39 mg kg???1 dw), Zn (59?C364 mg kg???1 dw), Mn (87?C376 mg kg???1 dw), Fe (188?C8,625 mg kg???1 dw), Ca (969?C3,756 mg kg???1 dw), and Cr (27?C660 mg kg???1 dw) indicating an uptake gradient of elements by plants as Ca>Fe>Mn>Cr>Zn>Cu>Pb. The present study indicates the importance of identification and efficiency of metal uptake and accumulation capabilities by plants in relation to their applications in remediation of a contaminated East Calcutta Wetland ecosystem. 相似文献
993.
Parvesh Chandna M. L. Khurana Jagdish K. Ladha Milap Punia R. S. Mehla Raj Gupta 《Environmental monitoring and assessment》2011,178(1-4):545-562
Increased use of nitrogenous fertilizers in the intensively cultivated rice (Oryza sativa)?Cwheat (Triticum aestivum) cropping system (covers a 13.5-ha m area in South Asia) has led to the concentration of nitrates (NO3-N) in the groundwater (GW) in Haryana State of India. Six districts from the freshwater zone were selected to identify factors affecting NO3-N enrichment in GW. Water and soil samples were collected from 1,580 locations and analyzed for their chemical properties. About 3% (26,796, and 10,588 ha) of the area was estimated to be under moderately high (7.5?C10 mg l???1) and high (>10 mg l???1) risk categories, respectively. The results revealed that NO3-N was 10?C50% higher during the pre-monsoon season than in the monsoon season. Nitrate-N decreased with the increase in aquifer depth (r 2?=?0.99). Spatial and proximity analyses using ArcGIS (9.2) revealed that (1) clay material in surface and sub-surface texture restricts N leaching, (2) piedmont and rolling plains act as an N sink, and (3) perennial rivers bring a dilution effect whereas seasonal rivers provide favorable conditions for NO3 ? enrichment. The study concludes that chemical N fertilizers applied in agro-ecosystems are not the sole factor determining the NO3 in groundwater; rather, it is an integrated process governed by several other factors including physical and chemical properties of soils, proximity and type of river, and geomorphologic and geographical aspects. Therefore, future studies should adopt larger area (at least watershed scale) to understand the mechanistic pathways of NO3 enrichment in groundwater and interactive role of the natural drainage system and surrounding physical features. In addition, the study also presents a conceptual framework to describe the process of nitrate formation and leaching in piedmont plains and its transportation to the mid-plain zone. 相似文献
994.
Determination of only total element in sediments does not give an accurate estimate of the likely environmental impacts. Speciation study of metals in sediment provides information on the potential availability of metals (toxic) to biota under various environmental conditions. In water, the toxic metal specie is the free hydrated metal ion. The toxicity of metals depends especially on their chemical forms rather than their total metal content. The present study focuses on Qaraaoun Reservoir, Lebanon. Earlier studies focused only on total metal concentrations in sediment and water. The objective of this study was to determine metal speciation (Fe, Cr, Ni, Zn, Cu, Pb, Cd) in the (operationally defined) sediment chemical fractions and metal speciation in reservoir water. This would reflect on metal bioavailability and toxicity. Water samples and bed sediments were collected from nine sites during the dry season and a sequential chemical fraction scheme was applied to the <75-??m sieve sediment fraction. Metal content in each fraction was determined by the FAAS technique. The data showed that the highest percentages of total metal content in sediment fractions were for: Fe in residual followed by reducible, Cr and Ni in residual and in reducible, Cu in organic followed by exchangeable, Zn in residual and in organic, Pb in organic and carbonate, Cd was mainly in carbonate. Total metal content in water was determined by ICP-MS technique and aqueous metal speciation was predicted using AQUACHEM software interfaced to PHREEQC geochemical computer model. The water speciation data predicted that a high percentage of Pb and Ni were present as carbonate complex species and low percentages as free hydrated ions, highest percentage of Zn as carbonate complex species followed by free hydrated ion, highest percentage of Cd as free hydrated ion followed by carbonate complex species. The sensitivity attempt of free hydrated ion of Ni, Zn, Pb, and Cd in reservoir water revealed dependence of Zn and Cd on pH and alkalinity, while Ni and Pb were only dependent on pH. 相似文献
995.
Volatiles from leaves or bark of nonhost birch (Betula pendula) and Norway spruce (Picea abies) dramatically reduced the attraction of the bark beetle, Pityogenes bidentatus (Coleoptera: Scolytidae), to their aggregation pheromone components (cis-verbenol and grandisol) in the field. In addition, odors from both the needles and bark of the host Scots pine (Pinus sylvestris) similarly inhibited attraction. Monoterpenes of pine and spruce (α-pinene, β-pinene, terpinolene, and 3-carene) as well
as ethanol, chalcogran and some nonhost green leaf alcohols [(Z)-3-hexen-1-ol, (E)-2-hexen-1-ol, and 1-hexanol], also reduced catches. Collections of volatiles from the field-tested plant tissues indicated
they released monoterpenes in amounts similar to the synthetics that inhibited responses. The various plant and insect sources
of these inhibitory compounds indicate that P. bidentatus bark beetles have evolved several strategies to increase their fitness by avoiding nonhost and unsuitable host trees in a
complex olfactory landscape.
Received: 6 June 2000 / Accepted in revised form: 25 September 2000 相似文献
996.
The "Henze solution", derived originally from the aqueous extraction of pelleted whole blood from the ascidian Phallusia mammillata, was examined using spectral studies. The aqueous extraction of fractionated blood cells including compartment cells, signet
ring cells, and morula cells obtained using cell separation techniques were also examined. It was found that this Henze solution,
and the Henze precipitate itself derived from this solution, emanated solely from the morula cells. Furthermore, it was found
that this solution is formed independently of the vanadium metal ions otherwise associated with the vanadocytes. Observation
of the Henze precipitate by light microscopy shows that this material partially forms crystallites or microglasses.
Received: 27 July 1999 / Accepted in revised form: 28 February 2000 相似文献
997.
Chemical synapses are highly specialized cell–cell junctions designed for efficient signaling between nerve cells. Distinct
cytoskeletal matrices are assembled at either side of the synaptic junction. The presynaptic cytomatrix at the active zone
(CAZ) defines and organizes the site of neurotransmitter release from presynaptic nerve terminals. The postsynaptic density
(PSD) tethers neurotransmitter receptors and the postsynaptic signal transduction machinery. Recent progress in the identification
and characterization of novel CAZ and PSD components has revealed new insights into the molecular organization and assembly
mechanisms of the synaptic neurotransmission apparatus. On the presynaptic side, Bassoon and Piccolo, two related giant proteins,
are crucially involved in scaffolding the CAZ. On the postsynaptic side, two families of multi-domain adaptor proteins, the
MAGuKs (membrane-associated guanylate kinase homologs) and the ProSAP (proline-rich synapse-associated protein, also termed
Shank) family members are thought to be major organizing molecules of the PSD. 相似文献
998.
999.
职业接触苯乙烯工人静脉血中蛋白质环氧苯乙烯加合物的分析测定 总被引:1,自引:0,他引:1
静脉血中蛋白质-环氧苯乙烯(SO)加合物的分析测定是将蛋白质中半胱氨酸残留经分解后,用Raney Ni催化反应生成两种加合物:α-苯己醇,β-苯已醇,再用五氟苯氯衍生,GC/MS测定,用同样的方法测SD大鼠血的蛋白质加合物,结果表明动物血中蛋白质加的与实验的苯乙烯或SO剂量有较好的相关性;而且SO与半胱氨酸的反应α位强于β位,在人群实验中,对一个石棉厂职业接触苯乙烯工人静脉血中的蛋白质加合物进行测 相似文献
1000.