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   1429篇
  免费   54篇
  国内免费   119篇
安全科学   182篇
废物处理   24篇
环保管理   248篇
综合类   555篇
基础理论   117篇
污染及防治   123篇
评价与监测   280篇
社会与环境   29篇
灾害及防治   44篇
  2023年   4篇
  2022年   24篇
  2021年   25篇
  2020年   41篇
  2019年   13篇
  2018年   14篇
  2017年   27篇
  2016年   25篇
  2015年   39篇
  2014年   62篇
  2013年   61篇
  2012年   64篇
  2011年   93篇
  2010年   67篇
  2009年   88篇
  2008年   76篇
  2007年   99篇
  2006年   98篇
  2005年   89篇
  2004年   63篇
  2003年   83篇
  2002年   55篇
  2001年   60篇
  2000年   62篇
  1999年   48篇
  1998年   47篇
  1997年   32篇
  1996年   30篇
  1995年   18篇
  1994年   15篇
  1993年   20篇
  1992年   15篇
  1991年   6篇
  1990年   7篇
  1989年   6篇
  1988年   2篇
  1987年   3篇
  1986年   5篇
  1984年   3篇
  1982年   2篇
  1981年   1篇
  1980年   1篇
  1979年   4篇
  1978年   1篇
  1977年   2篇
  1975年   1篇
  1972年   1篇
排序方式: 共有1602条查询结果,搜索用时 15 毫秒
921.
全省节水与旱作农业基本情况调查结果表明:干旱缺水是影响旱坡地作物产量提高的主要因子.近年来.我省采用节水灌溉技术、节水耕作技术、优化种植结构等措施,提高了水资源的利用率.今后,在旱坡地上开发节水高效农业大有潜力.  相似文献   
922.
This paper presents the results of the Environmental Monitoring Program for the Radioactive waste repository of Abadia de Goiás, which was originated from the accident of Goiania, conducted by the Regional Center of Nuclear Sciences (CRCN-CO) of the National Commission on Nuclear Energy (CNEN), from 1998 to 2008.The results are related to the determination of 137Cs activity per unit of mass or volume of samples from surface water, ground water, depth sediments of the river, soil and vegetation, and also the air-kerma rate estimation for gamma exposure in the monitored site.In the phase of operational Environmental Monitoring Program, the values of the geometric mean and standard deviation obtained for 137Cs activity per unit of mass or volume in the analyzed samples were (0.08 ± 1.16) Bq.L−1 for surface and underground water, (0.22 ± 2.79) Bq.kg−1 for soil, and (0.19 ± 2.72) Bq.kg−1 for sediment, and (0.19 ± 2.30) Bq.kg−1 for vegetation. These results were similar to the values of the pre-operational Environmental Monitoring Program.With these data, estimations for effective dose were evaluated for public individuals in the neighborhood of the waste repository, considering the main possible way of exposure of this population group.The annual effective dose obtained from the analysis of these results were lower than 0.3 mSv.y−1, which is the limit established by CNEN for environmental impact in the public individuals indicating that the facility is operating safely, without any radiological impact to the surrounding environment.  相似文献   
923.
Accurately determining methane emission factors of dairy herd in China is imperative because of China’s large population of dairy cattle. An inverse dispersion technique in conjunction with open-path lasers was used to quantify methane emissions from a dairy feedlot during the fall and winter seasons in 2009-2010. The methane emissions had a significant diurnal pattern during both periods with three emission peaks corresponding to the feeding schedule. A 10% greater emission rate in the fall season was obtained most likely by the higher methane emission from manure during that period. An annual methane emission rate of 109 ± 6.7 kg CH4 yr−1 characterized with a methane emission intensity of 32.3 ± 1.59 L CH4 L−1 of milk and a methane conversion factor (Ym) of 7.3 ± 0.38% for mature cattle was obtained, indicating the high methane emission intensity and low milk productivity in Northern China.  相似文献   
924.
A hyperspectral imaging system was used to monitor vegetation during a subsurface controlled release of carbon dioxide (CO2). From August 3 to 10, 2007, 0.3 tons CO2/day were released through a 70 m horizontal pipe located at a nominal depth of 1.8 m below the surface. Hyperspectral images of alfalfa plants were collected during the controlled release and used along with classification tree analysis to study changes in the reflectance spectra as a function of perpendicular distance from the horizontal pipe. Changes in the reflectance spectra near the red edge (650–750 nm) were observed over the course of the controlled release experiment for plants within a perpendicular distance of 1 m of the release pipe. These results indicate monitoring vegetation over a carbon sequestration site has the potential to allow monitoring of the integrity of the CO2 storage.  相似文献   
925.
煤矿生产安全风险管理机制的研究与应用   总被引:3,自引:1,他引:2  
通过对我国煤炭行业及典型煤炭企业的安全及安全管理的现状分析,找出煤炭企业在安全风险管理方面存在的主要问题;利用系统安全科学理论、风险管理理论、个体及群体行为理论、数理统计方法等,以平煤集团为样本,根据安全管理的3E原则,从技术保障、组织保障、文化教育保障等方面全方位地研究煤矿生产安全风险管理模型。通过该模型研究,为煤矿生产安全风险管理提供一套系统的理论体系和思路;在模型研究的基础上,应用先进的计算机技术,开发出网络版的煤矿生产安全风险管理系统,为生产现场提供先进、便捷的安全风险管理手段。  相似文献   
926.
In order to better understand the spatial and temporal distribution pattern of metals and sulfur present in Shanghai, moss bags with Haplocladium microphyllum (Hedw.) Broth. were suspended at 14 local monitoring stations from April through June 2006 in Shanghai, the largest city in China. The results showed that the concentrations of S, Cu, Pb, and Zn in the moss bags after exposure were higher at the sites in the industrial district and most urban districts and lower at the sites in suburban areas, and well correlated with SO2 API and PM10 API in the air both in terms of space and time. The present study provided evidence that the moss H. microphyllum is suitable for bio-monitoring air pollution with moss bags and further confirmed that the moss-bag method is a simple, inexpensive and useful technique.  相似文献   
927.
This paper reviews four commonly used statistical methods for environmental data analysis and discusses potential pitfalls associated with application of these methods through real case study data. The four statistical methods are percentile and confidence interval, correlation coefficient, regression analysis, and analysis of variance (ANOVA). The potential pitfall for estimation of percentile and confidence interval includes the automatic assumption of a normal distribution to environmental data, which so often show a log-normal distribution. The potential pitfall for correlation coefficient includes the use of a wide range of data points in which the maximum in value may trivialize other smaller data points and consequently skew the correlation coefficient. The potential pitfall for regression analysis includes the propagation of uncertainties of input variables to the regression model prediction, which may be even more uncertain. The potential pitfall for ANOVA includes the acceptance of a hypothesis as a weak argument to imply a strong conclusion. As demonstrated in this paper, we may draw very different conclusions based on statistical analysis if the pitfalls are not identified. Reminder and enlightenment obtained from the pitfalls are given at the end of this article.  相似文献   
928.
The introduction of anthropogenic sounds into the marine environment can impact some marine mammals. Impacts can be greatly reduced if appropriate mitigation measures and monitoring are implemented. This paper concerns such measures undertaken by Exxon Neftegas Limited, as operator of the Sakhalin-1 Consortium, during the Odoptu 3-D seismic survey conducted during 17 August–9 September 2001. The key environmental issue was protection of the critically endangered western gray whale (Eschrichtius robustus), which feeds in summer and fall primarily in the Piltun feeding area off northeast Sakhalin Island. Existing mitigation and monitoring practices for seismic surveys in other jurisdictions were evaluated to identify best practices for reducing impacts on feeding activity by western gray whales. Two buffer zones were established to protect whales from physical injury or undue disturbance during feeding. A 1 km buffer protected all whales from exposure to levels of sound energy potentially capable of producing physical injury. A 4–5 km buffer was established to avoid displacing western gray whales from feeding areas. Trained Marine Mammal Observers (MMOs) on the seismic ship Nordic Explorer had the authority to shut down the air guns if whales were sighted within these buffers. Additional mitigation measures were also incorporated: Temporal mitigation was provided by rescheduling the program from June–August to August–September to avoid interference with spring arrival of migrating gray whales. The survey area was reduced by 19% to avoid certain waters <20 m deep where feeding whales concentrated and where seismic acquisition was a lower priority. The number of air guns and total volume of the air guns were reduced by about half (from 28 to 14 air guns and from 3,390 in3 to 1,640 in3) relative to initial plans. “Ramp-up” (=“soft-start”) procedures were implemented. Monitoring activities were conducted as needed to implement some mitigation measures, and to assess residual impacts. Aerial and vessel-based surveys determined the distribution of whales before, during and after the seismic survey. Daily aerial reconnaissance helped verify whale-free areas and select the sequence of seismic lines to be surveyed. A scout vessel with MMOs aboard was positioned 4 km shoreward of the active seismic vessel to provide better visual coverage of the 4–5 km buffer and to help define the inshore edge of the 4–5 km buffer. A second scout vessel remained near the seismic vessel. Shore-based observers determined whale numbers, distribution, and behavior during and after the seismic survey. Acoustic monitoring documented received sound levels near and in the main whale feeding area. Statistical analyses of aerial survey data indicated that about 5–10 gray whales moved away from waters near (inshore of) the seismic survey during seismic operations. They shifted into the core gray whale feeding area farther south, and the proportion of gray whales observed feeding did not change over the study period. Five shutdowns of the air guns were invoked for gray whales seen within or near the buffer. A previously unknown gray whale feeding area (the Offshore feeding area) was discovered south and offshore from the nearshore Piltun feeding area. The Offshore area has subsequently been shown to be used by feeding gray whales during several years when no anthropogenic activity occurred near the Piltun feeding area. Shore-based counts indicated that whales continued to feed inshore of the Odoptu block throughout the seismic survey, with no significant correlation between gray whale abundance and seismic activity. Average values of most behavioral parameters were similar to those without seismic surveys. Univariate analysis showed no correlation between seismic sound levels and any behavioral parameter. Multiple regression analyses indicated that, after allowance for environmental covariates, 5 of 11 behavioral parameters were statistically correlated with estimated seismic survey-related variables; 6 of 11 behavioral parameters were not statistically correlated with seismic survey-related variables. Behavioral parameters that were correlated with seismic variables were transient and within the range of variation attributable to environmental effects. Acoustic monitoring determined that the 4–5 km buffer zone, in conjunction with reduction of the air gun array to 14 guns and 1,640 in3, was effective in limiting sound exposure. Within the Piltun feeding area, these mitigation measures were designed to insure that western gray whales were not exposed to received levels exceeding the 163 dB re 1 μPa (rms) threshold. This was among the most complex and intensive mitigation programs ever conducted for any marine mammal. It provided valuable new information about underwater sounds and gray whale responses during a nearshore seismic program that will be useful in planning future work. Overall, the efforts in 2001 were successful in reducing impacts to levels tolerable by western gray whales. Research in 2002–2005 suggested no biologically significant or population-level impacts of the 2001 seismic survey. M. W. Newcomer is deceased.  相似文献   
929.
突出行业特点的安全工程专业教育研究   总被引:6,自引:2,他引:4  
以我国安全工程专业学科建设过程为背景,分析安全工程专业教育存在的学科建设速度快、涉及知识面广、注重通识性教育等现状,结合我国近两年特大安全事故所表现的行业特点,从解决当前我国生产安全问题、培养高层次安全专业人才、促进安全学科发展3个方面入手,阐明安全工程专业教育中突出行业特点,进一步加强该领域安全工程专业教育建设的重要性,针对突出行业特点的安全工程专业教育模式提出了几点建议,特别强调安全科学与安全技术联系与独立的重要性,学科建设结合每个学校自己的特色方向和以点带面的建设及发展模式.  相似文献   
930.
Enhanced knowledge of water and solute pathways in catchments would improve the understanding of dynamics in water quality and would support the selection of appropriate water pollution mitigation options. For this study, we physically separated tile drain effluent and groundwater discharge from an agricultural field before it entered a 43.5-m ditch transect. Through continuous discharge measurements and weekly water quality sampling, we directly quantified the flow route contributions to surface water discharge and solute loading. Our multi-scale experimental approach allowed us to relate these measurements to field-scale NO3 concentration patterns in shallow groundwater and to continuous NO3 records at the catchment outlet. Our results show that the tile drains contributed 90-92% of the annual NO3 and heavy metal loads. Considering their crucial role in water and solute transport, enhanced monitoring and modeling of tile drainage are important for adequate water quality management.  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