首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   22776篇
  免费   209篇
  国内免费   370篇
安全科学   618篇
废物处理   1149篇
环保管理   2651篇
综合类   3162篇
基础理论   5866篇
环境理论   6篇
污染及防治   6360篇
评价与监测   1834篇
社会与环境   1573篇
灾害及防治   136篇
  2023年   113篇
  2022年   283篇
  2021年   259篇
  2020年   164篇
  2019年   216篇
  2018年   428篇
  2017年   370篇
  2016年   596篇
  2015年   427篇
  2014年   656篇
  2013年   1942篇
  2012年   746篇
  2011年   989篇
  2010年   902篇
  2009年   896篇
  2008年   1011篇
  2007年   1108篇
  2006年   972篇
  2005年   810篇
  2004年   814篇
  2003年   787篇
  2002年   742篇
  2001年   1062篇
  2000年   725篇
  1999年   439篇
  1998年   305篇
  1997年   280篇
  1996年   311篇
  1995年   299篇
  1994年   282篇
  1993年   264篇
  1992年   262篇
  1991年   224篇
  1990年   234篇
  1989年   236篇
  1988年   208篇
  1987年   169篇
  1986年   144篇
  1985年   149篇
  1984年   186篇
  1983年   167篇
  1982年   205篇
  1981年   148篇
  1980年   127篇
  1979年   159篇
  1978年   126篇
  1977年   115篇
  1976年   106篇
  1975年   93篇
  1974年   92篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
192.
The present investigation deals with the limnobiotic status of Almatti reservoir from February, 2003 to January, 2005. The study revealed that, the distribution and population density of zooplankton species depend upon the physico-chemical factors of the environment. Statistical analysis showed that there exists a significant relation between the biological and non-biological factors. The benthic fauna constituting the food of fish can be utilized for extensive culture operation so that the nutrients in the reservoir are not only properly cycled but also serve as a check on further eutrophication.  相似文献   
193.
The river Ganges has been one of the major recipients of industrial effluents in India. The present paper deals with the study related to occurrence and bioaccumulation of heavy metals (Cu, Cr, Cd, Pb, Zn) in the riverine water, sediment, and the muscles of two cat fish species, Channa punctatus (C. punctatus) and Aorichthys aor (A. aor) procured from the river Ganges at Allahabad. The data obtained after water analysis reflected the order of occurrence of heavy metals to be Zn > Pb > Cu > Cr > Cd, respectively. The analysis of heavy metals in sediment indicated that among the five heavy metals tested; Zn was maximally accumulated followed by Pb, Cr, Cu and Cd. The trend of heavy metals accumulation in fish muscles was found to be similar to that observed in sediment and water such as Zn > Pb > Cu > Cr > Cd. Data indicated that Zn accumulated maximally in the sediment as well as muscles of both of the fish species in comparison to other metals.  相似文献   
194.
Reject fly ash (rFA) represents a significant portion of the fly ashes produced from coal-fired power plants. Due to the high carbon content and large particle mean diameter, rFA is not utilized in the construction sector (for example, as supplementary cementing material) and is currently dumped into landfills, thus representing an additional environmental burden. Recently, the feasibility of using rFA in a relatively small number of applications, like solidification/stabilization of other wastes, has been investigated by different researchers. However, as the overall amount of fly ash utilized in such applications is still limited, there is a need to investigate other possibilities for rFA utilization starting from a deeper understanding of its properties. In the work presented herein, mechanical and hydration properties of cementitious materials prepared by blending the coarse fraction of a lignite high-calcium fly ash with ordinary cement were monitored and compared with the respective ones of a good quality fly ash-cement mixture. The results of this work reveal that a relatively cheap, bilateral classification-grinding method is able to promote the pozzolanic behavior of the rFAs, so that the overall performances of rFA containing cements are drastically improved. The evaluation of these results supports the belief that appropriate utilization of non-standardized materials may lead to new environmental-friendly products of superior quality.  相似文献   
195.
This paper describes the feasibility of an aerobic system (rotating biological contactor, RBC) and a biological anaerobic system (upward-flow anaerobic sludge bed reactor) at small scale for the treatment of a landfill leachate. In the first phase of the aerobic system study, a cyclic-batch RBC system was used to select perforated acetate discs among three different acetate disc configurations. These discs were chosen on the basis of high COD removal (65%) and biological stability. In the second phase, the RBC system (using four stages) was operated continuously at different hydraulic retention times (HRT), at different rotational speeds, and with varying organic concentrations of the influent leachate (2500-9000mgL(-1)). Forty percent of the total surface area of each perforated disc was submerged in the leachate. A COD removal of about 52% was obtained at an HRT of 24h and a rotational speed of 6rpm. For the anaerobic system, the reactor was evaluated with a volumetric organic load of 3273g-COD m(-3) day(-1) at an HRT of 54, 44, 39, 24 and 17h. At these conditions, the system reached COD removal efficiencies of 62%, 61%, 59%, 44% and 24%, respectively.  相似文献   
196.
Polyvinylchloride (PVC) was successfully recycled through the solvent extraction from waste pipe with an extraction yield of ca. 86%. The extracted PVC was pyrolyzed by a two-stage process (260 and 410 degrees C) to obtain free-chlorine PVC based pitch through an effective removal of chlorine from PVC during the heat-treatment. As-prepared pitch (softening point: 220 degrees C) was spun, stabilized, carbonized into carbon fibers (CFs), and further activated into activated carbon fibers (ACFs) in a flow of CO2. As-prepared CFs show comparable mechanical properties to commercial CFs, whose maximum tensile strength and modulus are 862 MPa and 62 GPa, respectively. The resultant ACFs exhibit a high surface area of 1200 m2/g, narrow pore size distribution and a low oxygen content of 3%. The study provides an effective insight to recycle PVC from waste PVC and develop a carbon precursor for high performance carbon materials such as CFs and ACFs.  相似文献   
197.
Twenty four hours diel cycles of arsenic speciation in Acid Mine Drainage (AMD) due to photooxidation have been reported for the first time. AMD samples were taken during 48 h (31st March and 1st April, 2005) at 6 h intervals from the effluent of a massive abandoned polymetallic sulphide mine of the Iberian Pyrite Belt (Sw Spain). Samples were preserved in situ using cationic exchange prior to analysis by coupled high performance liquid chromatography, hydride generation and atomic fluorescence spectrometry (HPLC-HG-AFS) for arsenic speciation. The results indicated the presence of inorganic arsenic species with daily means of 262mugl(-1) for As(V) and 107 microg l(-1) for As(III). No marked diel trend was observed for As(V). However, a marked diel trend was observed for As(III) in the two studied days, with maximum concentrations during nighttime (141-143 microg l(-1)) and minimum concentrations at daytime (72-77 microg l(-1)). This difference in concentration during daytime and nighttime is ca. 100%. A similar diel cycle was observed for iron. An explanation for the arsenic diel cycles observed is the light induced photooxidation of As(III) and the elimination of As(V) due to its adsorption onto Fe precipitates during the daytime. Furthermore, the diel changes in arsenic speciation emphasize the importance of designing suitable sampling strategies in AMD systems.  相似文献   
198.
Malaysia is in dire need of alternatives to landfilling for solid waste management. Recently, landfills have faced the problems of overfilling, overflowing of leachates leading to pollution of water resources, and uncontrolled dust emissions adversely affecting the local environment. With the rising cost of urbanization coupled with the high rate of waste generation, one possible method of waste treatment that is receiving particular attention by the government is incineration. Incineration of solid waste is rather new in Malaysia, with limited usage in handling small sources of waste generation such as the municipal solid waste (MSW) of resort islands; however, its potential in ameliorating the problems associated with solid waste treatment may make it an attractive alternative to landfill. This article presents the results of test runs conducted to investigate the performance of a locally designed and manufactured rotary kiln incinerator (RKI). The test runs were conducted using MSW collected from the Shah Alam municipality. The combustion efficiency was analyzed by looking at the temperature profiles and chemical species concentrations. To complement the combustion characteristics measurements, predictions of the air flow in the incinerator during the process were also investigated. The overall performance of the RKI suggests that it is suitable for treating MSW.  相似文献   
199.
Sorbitol and glycerol were used to plasticize sugar beet pulp-poly(lactic acid) green composites. The plasticizer was incorporated into sugar beet pulp (SBP) at 0%, 10%, 20%, 30% and 40% w/w at low temperature and shear and then compounded with poly(lactic acid) (PLA) using twin-screw extrusion and injection molding. The SBP:PLA ratio was maintained at 30:70. As expected, tensile strength decreased by 25% and the elongation increased. Acoustic emission (AE) showed correlated debonding and fracture mechanisms for up to 20% w/w plasticizer and uncorrelated debonding and fracture for 30–40% sorbitol and 30% glycerol content in SBP–PLA composites. All samples had a well dispersed SBP phase with some aggregation in the PLA matrix. However, at 40% glycerol plasticized SBP–PLA composites exhibited unique AE behavior and confocal microscopy revealed the plasticized SBP and PLA formed a co-continuous two phase system.
V. L. FinkenstadtEmail:
  相似文献   
200.
Schultz J  Søreide T 《Disasters》2008,32(4):516-536
Corruption in emergency procurement reduces the resources available for life‐saving operations, lowers the quality of products and services provided, and diverts aid from those who need it most. 1 1 The paper is based on a study for a project of the Chr Michelsen Institute (CMI)'s U4 Anti‐Corruption Resource Centre entitled ‘Corruption in Emergencies’ (see http://www.u4.no ).
It also negatively influences public support for humanitarian relief, both in the affected country and abroad. This paper aims to unpack and analyse the following question in order to mitigate risk: how and where does corruption typically occur, and what can be done? Suggested strategies reflect a multi‐layered approach that stresses internal agency control mechanisms, conflict‐sensitive management, and the need for common systems among operators.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号