全文获取类型
收费全文 | 29810篇 |
免费 | 336篇 |
国内免费 | 249篇 |
专业分类
安全科学 | 1006篇 |
废物处理 | 1454篇 |
环保管理 | 3960篇 |
综合类 | 4481篇 |
基础理论 | 7765篇 |
环境理论 | 8篇 |
污染及防治 | 7364篇 |
评价与监测 | 2127篇 |
社会与环境 | 2047篇 |
灾害及防治 | 183篇 |
出版年
2023年 | 141篇 |
2022年 | 263篇 |
2021年 | 323篇 |
2020年 | 197篇 |
2019年 | 243篇 |
2018年 | 437篇 |
2017年 | 461篇 |
2016年 | 722篇 |
2015年 | 532篇 |
2014年 | 856篇 |
2013年 | 2469篇 |
2012年 | 1021篇 |
2011年 | 1356篇 |
2010年 | 1105篇 |
2009年 | 1149篇 |
2008年 | 1414篇 |
2007年 | 1335篇 |
2006年 | 1207篇 |
2005年 | 1080篇 |
2004年 | 1037篇 |
2003年 | 992篇 |
2002年 | 935篇 |
2001年 | 1091篇 |
2000年 | 769篇 |
1999年 | 483篇 |
1998年 | 365篇 |
1997年 | 384篇 |
1996年 | 398篇 |
1995年 | 466篇 |
1994年 | 396篇 |
1993年 | 344篇 |
1992年 | 377篇 |
1991年 | 357篇 |
1990年 | 327篇 |
1989年 | 323篇 |
1988年 | 298篇 |
1987年 | 241篇 |
1986年 | 247篇 |
1985年 | 247篇 |
1984年 | 267篇 |
1983年 | 255篇 |
1982年 | 268篇 |
1981年 | 222篇 |
1980年 | 165篇 |
1979年 | 181篇 |
1978年 | 162篇 |
1977年 | 133篇 |
1975年 | 137篇 |
1973年 | 167篇 |
1972年 | 142篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
René A. Enguehard Rodolphe Devillers Orland Hoeber 《Journal of Coastal Conservation》2013,17(1):105-119
The conservation of wild fisheries resources in the face of an ever-increasing world demand for seafood requires the use of a number of management tools, including no-take zones, and gear, species, and temporal restrictions. One way of enforcing some of these regulations is through the use of Vessel Monitoring System (VMS) data that provides enforcement officers with the position of fishing vessels in the management area. The increasing volume of movement data collected using VMS calls for new methods that could help analysts extract useful knowledge from these large data sets. Various approaches have been proposed for visualizing and exploring movement data and detecting patterns within these data, but those approaches have generally not been tested in a real-world context or compared together, making their actual usability and utility unclear. This paper describes, compares, and assesses three such approaches in the context of fisheries enforcement: an existing system used for fisheries enforcement operations in Canada (VUE), a novel Hybrid Spatio-temporal Filtering (HSF) system developed by the authors, and an automated Behavioural Change Point Analysis (BCPA) system. A field trial was conducted with experienced fisheries enforcement officers to compare and contrast the benefits and drawbacks of the three approaches. While all three presented advantages and disadvantages, the interactivity of VUE and HSF were identified as desirable features, as they provide analysts with more control over the data, while allowing flexible data exploration. BCPA, while providing an automated approach to the data analysis, was pointed out as being too much of a “black box”, causing unease among the experts who require a level of transparency similar to that of legally admissible evidence. In the end, the experts suggested that the best approach would be to merge the analytical power of their existing VUE system with the exploratory power of the HSF system. This study provides insight into the value of using interactive mapping and filtering approaches in support of data analysis in the context of fisheries enforcement. 相似文献
982.
Nikola M. Pavlović Vuk Maksimović Jelena Dragišić Maksimović William H. Orem Calin A. Tatu Harry E. Lerch Joseph E. Bunnell Emina N. Kostić Diana N. Szilagyi Virgil Paunescu 《Environmental geochemistry and health》2013,35(2):215-226
Aristolochic acids (AAs) are nephrotoxic and carcinogenic derivatives found in several Aristolochia species. To date, the toxicity of AAs has been inferred only from the effects observed in patients suffering from a kidney disease called “aristolochic acid nephropathy” (AAN, formerly known as “Chinese herbs nephropathy”). More recently, the chronic poisoning with Aristolochia seeds has been considered to be the main cause of Balkan endemic nephropathy, another form of chronic renal failure resembling AAN. So far, it was assumed that AAs can enter the human food chain only through ethnobotanical use (intentional or accidental) of herbs containing self-produced AAs. We hypothesized that the roots of some crops growing in fields where Aristolochia species grew over several seasons may take up certain amounts of AAs from the soil, and thus become a secondary source of food poisoning. To verify this possibility, maize plant (Zea mays) and cucumber (Cucumis sativus) were used as a model to substantiate the possible significance of naturally occurring AAs’ root uptake in food chain contamination. This study showed that the roots of maize plant and cucumber are capable of absorbing AAs from nutrient solution, consequently producing strong peaks on ultraviolet HPLC chromatograms of plant extracts. This uptake resulted in even higher concentrations of AAs in the roots compared to the nutrient solutions. To further validate the measurement of AA content in the root material, we also measured their concentrations in nutrient solutions before and after the plant treatment. Decreased concentrations of both AAI and AAII were found in nutrient solutions after plant growth. During this short-term experiment, there were much lower concentrations of AAs in the leaves than in the roots. The question is whether these plants are capable of transferring significant amounts of AAs from the roots into edible parts of the plant during prolonged experiments. 相似文献
983.
Raafat A. Mandour Abdel-Aziz Ghanem Somaia M. El-Azab 《Environmental geochemistry and health》2013,35(2):251-256
This study was performed on fifty-two drinking tap water samples (surface and groundwater) collected from different districts of Dakahlia Governorate and fifty-two breast milk samples from lactating mothers hosted in Dakahlia Governorate hospitals. All these samples were subjected to lead analysis. Lead level in drinking groundwater showed higher levels than in drinking surface water. Also, an elevation of lead levels in breast milk of mothers drinking groundwater was noticed when compared with that of mothers drinking surface water. The comparison between mean lead levels in drinking water and mothers’ breast milk samples showed positive relationship. Lead concentrations in breast milk of the studied samples were elevated by exposure to smoking. We conclude that prolonged contact with lead plumbing can increase the lead content in tap water with subsequent increase in lead burden in infant fed formula and infant blood. Also, we recommend that chemical analyses must be carried out periodically for the surface and groundwater to ensure the water suitability for drinking purposes. Passive exposure to smoking during lactation should be avoided. Capsule: Prolonged contact with lead plumbing can increase the lead content in tap water with subsequent increase in lead burden in infant fed formula and infant blood. 相似文献
984.
New analytical formulations are presented for calculation of most effective parameters in the Gaussian plume dispersion model; the standard deviations of concentration for horizontal and vertical dispersion in neutral atmosphere conditions. Employing parallel Computational Fluid Dynamics (CFD) as a powerful tool, some well-known analytical generations of Pasquill–Gifford–Turner experimental data are modified. To achieve this aim, CFD simulations are carried out for single stack dispersion on flat terrain surface and ground level concentrations are determined in different distances. An inverse procedure in Gaussian plume dispersion model is then applied and standard deviations of horizontal and vertical dispersions are obtained. The values are compared with those of the well-known methods of Doury, Briggs and Hanna in two cases: the experimental data for release of krypton-85 from 100 m high and pollution dispersion from three 28 m high stacks of Besat power plant near Tehran. The comparison indicates that new formulations for plume dispersion are more accurate than other well-known formulations. 相似文献
985.
R. C. Anderson A. L. DuBois D. K. Piech W. A. Searcy S. Nowicki 《Behavioral ecology and sociobiology》2013,67(4):593-600
Signaling often involves complex suites of behaviors that incorporate different sensory modalities. Whatever modality is used to establish that a signal functions in communication researchers must demonstrate that receivers respond to it. The territory defense response of male swamp sparrows involves a variety of behaviors that includes both vocal and visual displays. One of these, the “wing wave” display, is a distinctive movement that predicts physical attack. Here, we use robotic taxidermic mounts paired with song to test the hypothesis that wing waving is a signal and, specifically, that male receivers respond to wing waving as a signal of aggressive intent. As predicted, subjects responded more aggressively to the mount during wing waving trials than during stationary trials. A second experiment demonstrated that this effect cannot be attributed simply to increased attention to movement. Less expectedly, subjects did not alter their own display behavior in response to wing waving as compared to a static mount. We conclude that the wing wave display in the context of singing is a signal that functions in male–male aggressive communication. Questions remain, including whether wing waving functions as a signal in the absence of singing and whether wing waving and song are redundant signals or communicate different information. 相似文献
986.
Koebele Elizabeth A. Crow Deserai A. Albright Elizabeth A. 《Environmental management》2020,65(1):1-18
The 17 Sustainable Development Goals (SDGs) underpinned by 169 targets presents national governments with huge challenges for implementation. We developed a proposal for a National Blueprint Framework (NBF) with 24 water-related indicators, centered on SDG 6 (clean water and sanitation for all), each with a specific target. We applied the NBF to 28 EU Member States (EU-28) and conclude that: 相似文献
987.
Andrew S. Jones Allan A. Andales Jos L. Chvez Cullen McGovern Garvey E.B. Smith Olaf David Steven J. Fletcher 《Journal of the American Water Resources Association》2020,56(2):201-211
We apply predictive weather metrics and land model sensitivities to improve the Colorado State University Water Irrigation Scheduler for Efficient Application (WISE). WISE is an irrigation decision aid that integrates environmental and user information for optimizing water use. Rainfall forecasts and verification performance metrics are used to estimate predictive rainfall probabilities that are used as input data within the irrigation decision aid. These input data errors are also used within a land model sensitivity study to diagnose important prognostic water movement behaviors for irrigation tool development purposes simultaneously performing the analysis in space and time. Thus, important questions such as “how long can a crop water application be delayed while maintaining crop yield production?” are addressed by evaluating crop growth stage interactions as a function of soil depth (i.e., space), rainfall events (i.e., time), and their probabilistic uncertainties. Editor’s note : This paper is part of the featured series on Optimizing Ogallala Aquifer Water Use to Sustain Food Systems. See the February 2019 issue for the introduction and background to the series. 相似文献
988.
W.I. Ford J.F. Fox D.T. Mahoney G. DeGraves A. Erhardt S. Yost 《Journal of the American Water Resources Association》2020,56(4):692-711
In the Ohio River (OR), backwater confluence sedimentation dynamics are understudied, however, these river features are expected to be influential on the system’s ecological and economic function when integrated along the river’s length. In the following paper, we test the efficacy of organic and inorganic tracers for sediment fingerprinting in backwater confluences; we use fingerprinting results to evidence sediment dynamics controlling deposition patterns in confluences used for wetland and marina functions; and we quantify the spatial extent of tributary drainages with wetland and marina features in OR confluences. Both organic and inorganic tracers statistically differentiate sediment from stream and river end‐members. Carbon and nitrogen stable isotopes produce greater uncertainty in fingerprinting results than inorganic elemental tracers. Uncertainty analysis of the nonconservative tracer term in the organic matter fingerprinting application estimates an apparent enrichment of the carbon stable isotopes during instream residence, and the nonconservativeness is quantified with a statistical approach unique to the fingerprinting literature. Wetland and marina features in OR confluences impact 42% and 11% of tributary drainage areas, respectively. Sediment dynamics show wetland and marina confluences experience deposition from river backwaters with longitudinally linear and nonlinear patterns, respectively, from sediment sources. 相似文献
989.
Ahmed I. El-Seesy Mohamed Nour Ali M. A. Attia Hamdy Hassan 《International Journal of Green Energy》2020,17(3):233-253
ABSTRACTThis article aims to study the influence of the addition of graphene oxide nanoparticles (GO) to diesel/higher alcohols blends on the combustion, emission, and exergy parameters of a CI engine under various engine loads. The higher alcohols mainly n-butanol, n-heptanol, and n-octanol are blended with diesel at a volume fraction of 50%. Then, the 25 and 50 mg/L concentrations of GO are dispersed into diesel/higher alcohols blends using an ultrasonicator. The GO structures are examined using TEM, TGA, XRD and FTIR. The findings show that there is a reduction in pmax. and HRR when adding higher alcohols with diesel fuel. Regarding engine emission, there is a significant improvement in emissions formation with adding higher alcohols. The addition of GO into diesel/higher alcohols blends improves the brake thermal efficiency by 15%. Moreover, the pmax. and HRR are both enhanced by 4%. The CO, UHC and smoke formation are reduced considerably by 40%, 50 and 20%, respectively, while NOx level is increased by 30% with adding GO. Finally, adding high percentages of n-butanol, n-heptanol, and n-octanol with diesel fuel with the presence of GO has the potential to achieve ultra-low CO, UHC, and smoke formation meanwhile keeping high thermal efficiency level. 相似文献
990.
Investigation of sustainable energy alternatives for powering remote communities in northern Ontario
ABSTRACT Remote communities in the North of Ontario survive in isolation as their proximity to the southern industrial sector of the province limits their accessibility to the major grid. The lack of grid connection has led to antiquated methods of power generation which pollute the environment and deplete the planet of its natural resources. Aside from the primary means of electricity generation being by diesel generators, generation infrastructure is deteriorating due to age and the stagnation of the power supply has led to communities facing load restrictions. These challenges may be resolved by introducing clean energy alternatives and providing a fuel blend option. The primary energy sources investigated in this research are solar, wind, and hydrogen. To assess the viability of these energy production methods in Northern communities, an exergy analysis is employed as it utilizes both the first and second law of thermodynamics to determine systems’ efficiency and performance in the surroundings. Local weather patterns were used to determine the viability of using wind turbines, solar panels and/or hydrogen fuel cells in a remote community. Through analysis of the resources available at the community, it was determined that the hydrogen fuel cell was best suited to provide clean energy to the community. Wind resulted in low efficiency in the range of 2–3% while solar efficiencies resulted in ranges of 18 – 19%, as the seasonal variations between the three years is not very great. Due to the higher operating efficiencies observed of the PV panels it would also be an attractive alternative to diesel generators however, the lack of consistent operation above 30% efficiency throughout the year, resulted in hydrogen fuel cells being a better alternative. 相似文献