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   213篇
  免费   2篇
  国内免费   1篇
废物处理   4篇
环保管理   16篇
综合类   90篇
基础理论   61篇
污染及防治   30篇
评价与监测   9篇
社会与环境   5篇
灾害及防治   1篇
  2018年   2篇
  2017年   6篇
  2015年   2篇
  2014年   3篇
  2013年   9篇
  2012年   3篇
  2011年   4篇
  2010年   4篇
  2009年   8篇
  2008年   6篇
  2007年   9篇
  2006年   6篇
  2005年   7篇
  2004年   6篇
  2003年   5篇
  2002年   3篇
  2001年   7篇
  2000年   5篇
  1999年   11篇
  1998年   2篇
  1997年   5篇
  1996年   4篇
  1995年   6篇
  1994年   7篇
  1993年   3篇
  1992年   5篇
  1991年   6篇
  1990年   3篇
  1989年   3篇
  1987年   3篇
  1986年   4篇
  1985年   5篇
  1981年   2篇
  1980年   3篇
  1974年   3篇
  1973年   2篇
  1961年   5篇
  1959年   3篇
  1958年   2篇
  1957年   2篇
  1956年   2篇
  1955年   5篇
  1954年   4篇
  1939年   1篇
  1938年   1篇
  1935年   1篇
  1932年   1篇
  1929年   1篇
  1926年   1篇
  1919年   1篇
排序方式: 共有216条查询结果,搜索用时 15 毫秒
91.
This study deals with the evaluation of water quality of the Three Gorges Reservoir (TGR) in order to assess its suitability as a raw water source for drinking water production. Therefore, water samples from (1) surface water, (2) tap water, and (3) wastewater treatment plant effluents were taken randomly by 2011–2012 in the area of the TGR and were analyzed for seven different organic contaminant groups (207 substances in total), applying nine different analytical methods. In the three sampled water sources, typical contaminant patterns were found, i.e., pesticides and polycyclic aromatic hydrocarbons (PAH) in surface water with concentrations of 0.020–3.5 μg/L and 0.004–0.12 μg/L, disinfection by-products in tap water with concentrations of 0.050–79 μg/L, and pharmaceuticals in wastewater treatment plant effluents with concentrations of 0.020–0.76 μg/L, respectively. The most frequently detected organic compounds in surface water (45 positives out of 57 samples) were the pyridine pesticides clopyralid and picloram. The concentrations might indicate that they are used on a regular basis and in conjunction in the area of the TGR. Three- and four-ring PAH were ubiquitously distributed, while the poorly soluble five- and six-ring members, perfluorinated compounds, polychlorinated biphenyls, and polybrominated diphenyl ethers, were below the detection limit. In general, the detected concentrations in TGR are in the same range or even lower compared to surface waters in western industrialized countries, although contaminant loads can still be high due to a high discharge. With the exception of the two pesticides, clopyralid and picloram, concentrations of the investigated organic pollutants in TGR meet the limits of the Chinese Standards for Drinking Water Quality GB 5749 (Ministry of Health of China and Standardization Administration of China 2006) and the European Union (EU) Council Directive 98/83/EC on the quality of water intended for human consumption (The Council of the European Union 1998), or rather, the EU Directive on environmental quality standards in the field of water policy (The European Parliament and The Council of the European Union 2008). Therefore, the suggested use of surface water from TGR for drinking water purposes is a valid option. Current treatment methods, however, do not seem to be efficient since organic pollutants were detected in significant concentrations in purified tap water.  相似文献   
92.
Metal (i.e. Ag, As, Ca, Cd, Co, Cu, Mn, Pb and Zn) and metallothionein (MT) concentrations in the soft tissue of Littorina littorea were measured along the heavily polluted Western Scheldt (WS) and relatively clean Eastern Scheldt (ES) estuary. Along the WS metal and MT levels in periwinkles reflected the known downstream decreasing pollution gradient. Surprisingly in ES animals As, Mn and Zn concentrations decreased from east to west reflecting past pollution. Compared to the WS metal concentrations of ES periwinkles were significantly lower and both estuaries were maximally discriminated from each other based on their Cd soft tissue concentration using a canonical discriminant analysis. Furthermore, no overall difference was found in MT levels among animals from both estuaries. Using previously obtained condition data (i.e. dry/wet weight ratio and lipid content) the relation between soft tissue metal concentration (i.e. Cd, Cu and Zn) and fitness indicators (i.e. MT and condition data) was examined using a canonical correlation analysis. Periwinkles with a high metal load (i.e. Cd and Zn) also had high MT levels but were in a relatively poor condition.  相似文献   
93.
Islands harbor a disproportionate amount of the earth's biodiversity, but a significant portion has been lost due in large part to the impacts of invasive mammals. Fortunately, invasive mammals can be routinely removed from islands, providing a powerful tool to prevent extinctions and restore ecosystems. Given that invasive mammals are still present on more than 80% of the world's major islands groups and remain a premier threat to the earth's biodiversity, it is important to disseminate replicable, scaleable models to eradicate invasive mammals from islands. We report on a successful model from western México during the past decade. A collaborative effort between nongovernmental organizations, academic biologists, Mexican government agencies, and local individuals has resulted in major restoration efforts in three island archipelagos. Forty-two populations of invasive mammals have been eradicated from 26 islands. For a cost of USD 21,615 per colony and USD 49,370 per taxon, 201 seabird colonies and 88 endemic terrestrial taxa have been protected, respectively. These conservation successes are a result of an operational model with three main components: i) a tri-national collaboration that integrates research, prioritization, financing, public education, policy work, capacity building, conservation action, monitoring, and evaluation; ii) proactive and dedicated natural resource management agencies; and iii) effective partnerships with academic researchers in Mexico and the United States. What is now needed is a detailed plan to eradicate invasive mammals from the remaining islands in the region that integrates the needed additional financing, capacity, technical advances, and policy issues. Island conservation in western Mexico provides an effective approach that can be readily applied to other archipelagos where conservation efforts have been limited.  相似文献   
94.
The model LINKopt is a mixed-integer, linear programming model for mid- and long-term planning of waste management options on an inter-company level. There has been a large increase in the transportation of waste material in Germany, which has been attributed to the implementation of the European Directive 75/442/EEC on waste. Similar situations are expected to emerge in other European countries. The model LINKopt has been developed to determine a waste management system with minimal decision-relevant costs considering transportation, handling, storage and treatment of waste materials. The model can serve as a tool to evaluate various waste management strategies and to obtain the optimal combination of investment options. In addition to costs, ecological aspects are considered by determining the total mileage associated with the waste management system. The model has been applied to a German case study evaluating different investment options for a co-operation between Daimler-Chrysler AG at Rastatt, its suppliers, and the waste management company SITA P+R GmbH. The results show that the installation of waste management facilities at the premises of the waste producer would lead to significant reductions in costs and transportation.  相似文献   
95.
96.
97.
Amniotic fluid from 135 pregnancies was assayed for human chorionic gonadotropin (hCG) and its free alpha (ahCG) and free beta (bhCG) subunits. Forty-six chromosomally abnormal pregnancies between 14 and 20 weeks' gestation were matched with 89 chromosomally normal samples. Compared with controls, trisomy 21 pregnancies exhibited significantly elevated levels of all three peptides, whereas trisomy 18 gestations gave rise only to significant elevation of ahCG. Female fetuses in both the trisomy 21 and trisomy 18 pregnancies provided significantly elevated levels of hCG and bhCG compared to their male counterparts. On converting the values to multiples of the median, it was determined that 6 of 7 trisomy 18 samples had abnormally elevated alpha/beta ratios, as did 6 of 21 Down's syndrome pregnancies. Further, 11 of 21 trisomy 21 gestations had abnormal amniotic fluid hCG levels. Using only ahCG, bhCG and their ratio, a 61 per cent sensitivity was found for these trisomies, with a 96 per cent specificity.  相似文献   
98.
99.
Es wird über Kontaminationen mit synthetischen benzoiden Nitromoschus-Verbindungen Moschus Xylol, Moschus Keton, Moschus Ambrette, Moschus Mosken in verschiedenen Fischarten aus Binnengew?ssern und Forellen aus Aquakulturen, Muscheln, Muttermilch und Humanfett berichtet. Bromocyclen wurde in Sü?wasserfischen — besonders Forellen aus dem Ausland — gefunden. Die Nitromoschus-Verbindungen werden in gro?en Mengen unter anderem als Duftstoffe in Waschmitteln, Seifen, Cremes und Lotions verwendet. Es wird über ?kotoxikologische Wirkungen (Fischtoxizit?t), den biologischen Abbau und das Biokonzentrationspotential dieser Umweltchemikalien in Fischen berichtet. Neben der oralen Aufnahme über die Nahrung mu? beim Menschen die Hautresorption und die inhalative Aufnahme von Nitromoschus-Verbindungen berücksichtigt werden. Um diese Rückst?nde im Menschen und in Lebensmitteln zu reduzieren bzw. zu vermeiden, wird an die Hersteller von Nitromoschus-Verbindungen bzw. an die Riechstoff-, Kosmetik- und Reinigungsmittelindustrie appelliert, aus Vorsorgegründen auf die Herstellung bzw. den Einsatz von Nitromoschus-Verbindungen und Bromocyclen in allen ihren Produkten zu verzichten.  相似文献   
100.
Among brooding species, passive and active means to provide oxygen to embryos can be observed. Among passive oxygen providers, lower oxygen availability in the center than at the periphery of embryo masses seems to delay development of inner embryos. We investigated the differences in patterns of oxygen supply to the periphery and the center of embryo masses in two active oxygen providers, the brachyuran crabs Cancer setosus and Homalaspis plana, and evaluated the consequences on: (1) the proportion of time that early- and late-stage embryos were exposed to low or high oxygen partial pressure (PO2), (2) oxygen consumption of the embryos from the center (inner) and the periphery (outer) of the embryo mass at those PO2 levels that the embryos experience throughout development, and (3) development of inner and outer embryos. We found that oxygen availability in the embryo masses of brachyuran crabs exhibited dramatic contrasts between the periphery and the center during early development and that these differences decreased throughout embryonic development. These dissimilar patterns of oxygen availability produced differences in the proportion of the time that the embryos were exposed to high and low PO2 levels throughout development. PO2 affected oxygen consumption of the inner and outer embryos in the same fashion, but the oxygen demand of inner embryos was lower. Furthermore, development of inner embryos was delayed, in comparison to outer embryos of the same female. We suggest that the asynchrony in the development of inner embryos, in comparison to outer embryos, is due to oxygen limitation, since oxygen availability affects embryonic oxygen consumption. The differences between development of inner and outer embryos is relatively small, when compared to other marine invertebrates, probably because female crabs are able to adjust oxygen supply to the embryos according their needs, while passive oxygen providers are not. However, active oxygen provision may affect investment in reproduction. Our results could have important implications both on studies of larval development and survival and in understanding the life-history tradeoffs of aquatic invertebrates.  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