全文获取类型
收费全文 | 26269篇 |
免费 | 2043篇 |
国内免费 | 3669篇 |
专业分类
安全科学 | 4726篇 |
废物处理 | 387篇 |
环保管理 | 4052篇 |
综合类 | 13296篇 |
基础理论 | 2880篇 |
环境理论 | 30篇 |
污染及防治 | 1472篇 |
评价与监测 | 1273篇 |
社会与环境 | 2354篇 |
灾害及防治 | 1511篇 |
出版年
2024年 | 64篇 |
2023年 | 313篇 |
2022年 | 602篇 |
2021年 | 794篇 |
2020年 | 833篇 |
2019年 | 719篇 |
2018年 | 626篇 |
2017年 | 925篇 |
2016年 | 1074篇 |
2015年 | 1074篇 |
2014年 | 1131篇 |
2013年 | 1552篇 |
2012年 | 1911篇 |
2011年 | 2067篇 |
2010年 | 1535篇 |
2009年 | 1541篇 |
2008年 | 1185篇 |
2007年 | 1775篇 |
2006年 | 1723篇 |
2005年 | 1423篇 |
2004年 | 1192篇 |
2003年 | 1255篇 |
2002年 | 1040篇 |
2001年 | 817篇 |
2000年 | 807篇 |
1999年 | 739篇 |
1998年 | 544篇 |
1997年 | 466篇 |
1996年 | 371篇 |
1995年 | 374篇 |
1994年 | 350篇 |
1993年 | 271篇 |
1992年 | 229篇 |
1991年 | 155篇 |
1990年 | 110篇 |
1989年 | 60篇 |
1988年 | 52篇 |
1987年 | 28篇 |
1986年 | 21篇 |
1985年 | 34篇 |
1984年 | 20篇 |
1983年 | 19篇 |
1982年 | 21篇 |
1981年 | 15篇 |
1980年 | 16篇 |
1979年 | 23篇 |
1978年 | 14篇 |
1977年 | 17篇 |
1973年 | 10篇 |
1971年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
简要叙述了电捕焦油器开工以来存在的问题,对电捕捕焦油器不能安全稳定运行的原因进行了分析,并采取改进措施。实践证明,改进工艺技术合理,方法可行,电捕焦油器运行效果达到指标要求。 相似文献
2.
Ismael A.S. Ehtiwesh Fernando Neto Da Silva Antonio C.M. Sousa 《International Journal of Green Energy》2019,16(1):72-85
The study addresses the potential of using concentrated solar power plants (CSPs) as a sustainable alternative of clean energy generation in the Mediterranean region and, in particular, in its North Africa shore. This location presents attractive conditions for the installation of CSPs, in particular high solar irradiation, good manpower concentration, and proximity and availability of water resources for condenser cooling. Energetic, exergetic, and economic analyses were conducted taking into consideration a particular type of CSPs - the parabolic trough concentrated solar power plant, which incorporates the most proven technology and it is already used in Southern Europe (Spain). In addition, the study considered the impact of project financing and incentives on the cost of energy. The combination of higher values for performance and potentially lower levelized cost of electricity (LCE) for the North Africa Mediterranean Rim than the South of Spain region can yield a very favorable return for the invested capital. Tripoli compared to Almeria presented superior performance and potentially lower LCE values ($0.18/kWh versus $0.22/kWh). This is significant, even when it is taken into consideration the fact that the plant in Tripoli, despite a relatively modest capacity factor of 34%, has a large gross power output of 173,886 MWhe. In addition, the implementation at the Tripoli location of a plant similar to the Anadsol plant has a slight advantage (2–3%) in terms of overall efficiency. 相似文献
3.
Amirhossein Moosavi Adel Nikfarjam 《International Journal of Sustainable Engineering》2019,12(3):174-188
In this paper, the inventory-routing problem is studied for a closed-loop supply chain. This closed-loop supply chain considers suppliers, manufacturers, whole-sellers, and disposal centers. To formulate this problem, a mixed integer linear programming model is proposed. This mathematical model minimizes the total costs of the supply chain, including the fixed and variable costs of vehicles, and holding inventory costs of final products and scraps. The proposed model considers the road roughness degree, multi-path setting and the heterogeneous fleet of vehicles, which increases its flexibility and the quality of solutions. Then, two symmetry-breaking constraints are proposed to reduce the complexity of the mathematical model. In order to evaluate the integrity of the proposed model, 20 instances of different sizes are randomly generated and solved. Finally, a comprehensive sensitivity analysis is conducted with respect to five key features of the problem, such as the impact of the symmetry-breaking constraints on the CPU time, multi-path setting, fixed cost of vehicles, heterogeneous fleet of vehicles, and lost sales. The results indicate that the consideration of multi-path setting and the heterogeneous fleet of vehicles improves the quality of solutions significantly. 相似文献
4.
Quantitative methods have been applied to the study of floristic structure and diversity in Samarskaya Luka. The results show that Samarskaya Luka is a floristically heterogeneous area in which six elementary floras can be distinguished. This area has been assessed as a floristically autonomous formation, and its floristic representativeness was estimated. 相似文献
5.
基于复杂系统建模的水管理政策研究进展 总被引:3,自引:0,他引:3
基于Agent的建模方法(ABSS)通过自下而上的方式,考察系统中主体的不同状态和行为特征、主体与环境的作用、主体之间的作用,来表征系统的宏观特征,是进行复杂社会环境系统分析和政策研究的重要手段,在水资源、水环境管理系统中得到了有效的应用。本文在大量文献调研的基础上,讨论了ABSS建模方法的基本原理、主要特征、系统构成、分类方法和开发工具等特征,总结了其供水系统发展、水资源分配和流域水资源管理、农业土地和水资源利用、居民用水行为、农业污染控制及人类活动的水环境影响等方面的应用,分析了其在研究内容、研究方法、研究结果等方面的发展趋势,讨论了利用该方法研究我国水资源管理和水污染控制政策的必要性和重要性。 相似文献
6.
7.
8.
S. N. Goroshkevich 《Russian Journal of Ecology》2008,39(3):168-175
A statistical analysis of interannual variation in a set of vegetative and generative characters over 13 years has been performed to characterize the growth and seed production dynamics of the Siberian stone pine (Pinus sibirica Du Tour) in the southeast of the forest zone in western Siberia. The results have shown that the range of fluctuations in most of vegetative characters is ordinary and their distribution is close to normal. The range of fluctuations in many generative characters is enormous (from 0 to +∞), and the distribution of their values is usually skewed, with low values being recorded several times more frequently than high values. Most variable are the proportion of abortive cones and other characters that are determined mainly in the spring of the pollination year. These characters account for a very high level of variation in the total seed production. 相似文献
9.
面对人口老龄化对经济发展的影响.应以养老和健康保障为先导.逐步加大对社会保障基金的投入.充实基本养老保险和医疗保险基金.建立和完善与生产力发展水平相适应的社会保障制度.继续推进社会保障社会化和产业结构调整的力度.建议政府应大力发展老龄产业。政府必须从实际出发.坚持科学发展观.逐步建立和完善老年社会养老制度和福利制度.根据老年消费市场状况.规范、引导投资.调整、优化产业结构用产业化、市场化、社会化的新运行机制.推进安老、养老产业的发展.根据老年人的不同需求,有计划的发展老龄产业、开发老年用品.增设老年服务项目.满足老年人在物质和文化方面的发展需要.以促使人口老龄化与经济的协调发展。 相似文献
10.