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921.
针对碳排放和经济增长的协调性关系,基于环境库兹涅茨曲线(EKC)假说和脱钩理论,选取中国、美国、印度、俄罗斯、日本、德国、韩国、沙特阿拉伯、加拿大、英国10个主要碳排放国家的年度数据进行实证研究。碳排放与经济增长的协调性分析结果表明:欧盟等国协调性较好,中、印等发展中国家需要加强。EKC与脱钩理论在度量低碳方面是统一的(2种方法下考察碳强度得到的弹性和结论基本一致),在构建低碳指标长、短期目标时,可分别参考EKC回归系数(β)和Tapio脱钩弹性系数(e);在促进低碳经济发展方面,发展中国家可借鉴欧盟等国经验,力求较低碳排放和较高经济增长之间的协调发展。  相似文献   
922.
导游是旅游从业一线人员,代表着旅游业的形象,关系着旅游业的良性发展。在游客追求低廉出游价格时,导游因其弱势群体地位最终成为旅游服务利益方的牺牲品,导游生存、发展与管理已成为困扰旅游业的一大难题。SPC理论即服务利益链理论强调顾客与员工的让渡价值,认为企业盈利能力的增强主要源于顾客和员工的企业忠诚度并最终源于企业对内部员工的服务质量。基于SPC理论,探讨了我国服务型导游管理模式的构建,指出旅游服务各利益方应服务导游,创造导游良好的就业和发展环境,以解决导游管理难题。  相似文献   
923.
The importance of accounting for economic costs when making environmental‐management decisions subject to resource constraints has been increasingly recognized in recent years. In contrast, uncertainty associated with such costs has often been ignored. We developed a method, on the basis of economic theory, that accounts for the uncertainty in population‐management decisions. We considered the case where, rather than taking fixed values, model parameters are random variables that represent the situation when parameters are not precisely known. Hence, the outcome is not precisely known either. Instead of maximizing the expected outcome, we maximized the probability of obtaining an outcome above a threshold of acceptability. We derived explicit analytical expressions for the optimal allocation and its associated probability, as a function of the threshold of acceptability, where the model parameters were distributed according to normal and uniform distributions. To illustrate our approach we revisited a previous study that incorporated cost‐efficiency analyses in management decisions that were based on perturbation analyses of matrix population models. Incorporating derivations from this study into our framework, we extended the model to address potential uncertainties. We then applied these results to 2 case studies: management of a Koala (Phascolarctos cinereus) population and conservation of an olive ridley sea turtle (Lepidochelys olivacea) population. For low aspirations, that is, when the threshold of acceptability is relatively low, the optimal strategy was obtained by diversifying the allocation of funds. Conversely, for high aspirations, the budget was directed toward management actions with the highest potential effect on the population. The exact optimal allocation was sensitive to the choice of uncertainty model. Our results highlight the importance of accounting for uncertainty when making decisions and suggest that more effort should be placed on understanding the distributional characteristics of such uncertainty. Our approach provides a tool to improve decision making.  相似文献   
924.
The extinction of large herbivores, often keystone species, can dramatically modify plant communities and impose key biotic thresholds that may prevent an ecosystem returning to its previous state and threaten native biodiversity. A potentially innovative, yet controversial, landscape‐based long‐term restoration approach is to replace missing plant‐herbivore interactions with non‐native herbivores. Aldabran giant (Aldabrachelys gigantea) and Madagascan radiated (Astrochelys radiata) tortoises, taxonomically and functionally similar to the extinct Mauritian giant tortoises (Cylindraspis spp.), were introduced to Round Island, Mauritius, in 2007 to control the non‐native plants that were threatening persistence of native species. We monitored the response of the plant community to tortoise grazing for 11 months in enclosures before the tortoises were released and, compared the cost of using tortoises as weeders with the cost of using manual labor. At the end of this period, plant biomass; vegetation height and cover; and adult, seedling, flower, and seed abundance were 3–136 times greater in adjacent control plots than in the tortoise enclosures. After their release, the free‐roaming tortoises grazed on most non‐native plants and significantly reduced vegetation cover, height, and seed production, reflecting findings from the enclosure study. The tortoises generally did not eat native species, although they consumed those native species that increased in abundance following the eradication of mammalian herbivores. Our results suggest that introduced non‐native tortoises are a more cost‐effective approach to control non‐native vegetation than manual weeding. Numerous long‐term outcomes (e.g., change in species composition and soil seed bank) are possible following tortoise releases. Monitoring and adaptive management are needed to ensure that the replacement herbivores promote the recovery of native plants. Estudiando el Potencial para Restaurar Ecosistemas Históricos de Forrajeo con Reemplazos Ecológicos de Tortugas Terrestres  相似文献   
925.
突变理论在矿山安全中的应用   总被引:1,自引:0,他引:1  
矿山企业的安全状况,直接关系到我国资源工业的发展,如何提高矿山安全,是矿山重大危险源辨识与评价技术研究的重点。笔者应用突变理论这一工具,对矿井内因火灾、矿山安全投资、煤层注水效果进行研究,其中的结论可服务于生产实际  相似文献   
926.
为了科学预防并控制煤矿运输险兆事件发生,需明确煤矿运输险兆事件影响因素,以便采取相应的管控策略。在文献研究与调研访谈的基础上,运用扎根理论质性研究方法,深入分析访谈资料及煤矿运输险兆事件案例,通过开放性译码、主轴译码、选择性译码、理论饱和检验等环节对煤矿运输险兆事件影响因素进行研究。结果表明,安全培训、安全意识、监督检查等16个主范畴对煤矿运输险兆事件有影响,从中选择4个核心范畴,即运输设备系统、运输作业场所、组织管理体系、工作人员素质,概括为物理性因素与行为性因素,构建了包含2个主要因素、4个核心范畴及16个主范畴的煤矿运输险兆事件影响因素评价指标体系,最后提出了推行标准作业流程、建立管理机制、加强安全文化建设、开展闭环教育培训等策略,减少并预防煤矿运输险兆事件的发生。  相似文献   
927.
We developed a stochastic simulation model incorporating most processes likely to be important in the spread of Phytophthora ramorum and similar diseases across the British landscape (covering Rhododendron ponticum in woodland and nurseries, and Vaccinium myrtillus in heathland). The simulation allows for movements of diseased plants within a realistically modelled trade network and long-distance natural dispersal. A series of simulation experiments were run with the model, representing an experiment varying the epidemic pressure and linkage between natural vegetation and horticultural trade, with or without disease spread in commercial trade, and with or without inspections-with-eradication, to give a 2 × 2 × 2 × 2 factorial started at 10 arbitrary locations spread across England. Fifty replicate simulations were made at each set of parameter values. Individual epidemics varied dramatically in size due to stochastic effects throughout the model. Across a range of epidemic pressures, the size of the epidemic was 5–13 times larger when commercial movement of plants was included. A key unknown factor in the system is the area of susceptible habitat outside the nursery system. Inspections, with a probability of detection and efficiency of infected-plant removal of 80% and made at 90-day intervals, reduced the size of epidemics by about 60% across the three sectors with a density of 1% susceptible plants in broadleaf woodland and heathland. Reducing this density to 0.1% largely isolated the trade network, so that inspections reduced the final epidemic size by over 90%, and most epidemics ended without escape into nature. Even in this case, however, major wild epidemics developed in a few percent of cases. Provided the number of new introductions remains low, the current inspection policy will control most epidemics. However, as the rate of introduction increases, it can overwhelm any reasonable inspection regime, largely due to spread prior to detection.  相似文献   
928.
为了有效提高机场不停航施工的安全监管效果,减少施工人员不安全行为,结合机场不停航施工特点,充分考虑安全监管和施工人员的有限理性及心理作用,基于前景理论和心理账户理论对传统博弈价值感知矩阵进行优化,进而构建安全监管演化博弈模型并对关键因素的影响情况进行模拟仿真研究。研究结果表明:决策群体初始安全能力、低估安全事故损失、安全监管和施工成本等因素对安全施工和监管行为策略选择的影响显著。机场管理部门和施工单位可以从提高工作人员安全能力,加强安全知识宣讲、警示教育、心理疏导,努力降低监管和施工成本等方面入手,进一步完善机场不停航施工安全管理和相应监管制度,充分引导施工和监管人员从事安全生产,遵守安全管理规定。  相似文献   
929.
为了解决由于地铁深基坑施工风险因素不确定性和基坑工程事故资料缺失导致传统风险分析方法不再满足实际需要的问题。探讨模糊集理论(FST)和贝叶斯网络(BN)的结合,介绍1种专家置信度指标,建立地铁深基坑渗漏风险评估指标体系,得到基于模糊贝叶斯网络(FBN)地铁深基坑施工渗漏风险评估模型。研究结果表明:将该方法应用于广州地铁十三号线某车站深基坑施工渗漏风险评估中,结果符合施工实际,接缝密封质量差等风险因素需加以措施控制,该方法可为后续施工风险评估提供实时支持。  相似文献   
930.
目的 针对某机电引信加速寿命试验数据,采用传统统计分析方法存在计算量大、寿命预测精度难以保证的问题,开展与智能算法相结合的引信贮存寿命预测研究。方法 针对步进应力加速寿命试验数据,采用贝叶斯理论的环境因子法,对各级应力下的贮存时间进行折合计算。利用进化策略对粒子群算法进行改进,进而对所建立的BP神经网络预测模型的全局参数进行调整和优化,突破传统方法的局限。将折合后的试验时间、样本量、应力水平作为网络输入,失效数作为输出,来预测引信贮存寿命。结果 利用训练好的 BP神经网络预测引信在正常应力水平下的失效数,计算其贮存可靠度。在迭代402次后,模型找到最优解,且预测误差在1%以内。结论 步进应力加速寿命试验与智能算法相结合的方法计算过程简单,预测精度较高,可有效提高引信贮存寿命的预测精度。  相似文献   
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