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251.
Reed M. Maxwell Andrew F.B. Tompson Stefan Kollet 《Journal of contaminant hydrology》2009,108(1-2):12-28
Underground nuclear weapons testing at the Nevada Test Site introduced numerous radionuclides that may be used subsequently to characterize subsurface hydrologic transport processes in arid climates. In 1965, a unique, 16-year pumping experiment designed to examine radionuclide migration away from the CAMBRIC nuclear test, conducted in the saturated zone beneath Frenchman Flat, Nevada, USA, gave rise to an unintended second experiment involving radionuclide infiltration through the vadose zone, as induced by seepage of pumping effluents beneath an unlined discharge trench. The combined experiments have been reanalyzed using a detailed, three-dimensional numerical model of transient, variably saturated flow and mass transport in a heterogeneous subsurface, tailored specifically for large-scale and efficient calculations. Simulations have been used to estimate tritium travel and residence times in various parts of the system for comparison with observations in wells. Model predictions of mass transport were able to clearly demonstrate radionuclide recycling behavior between the trench and pumping well previously suggested by isotopic age dating information; match travel time estimates for radionuclides moving between the trench, the water table, and monitoring and pumping wells; and provide more realistic ways in which to interpret the pumping well elution curves. Collectively, the results illustrate the utility of integrating detailed numerical modeling with diverse observational data in developing more accurate interpretations of contaminant migration processes. 相似文献
252.
随着现代信息网络技术的不断发展和广泛使用,使用电子阅览室查阅各种文献的读者迅速增加,电子阅览室的安全问题也愈发突出。从计算机及辅助设备的安全管理和维护、加强对计算机病毒的防治、加强对用户的管理等方面探讨了在网络环境下如何实现对电子阅览室日常的安全管理。 相似文献
253.
LCA法在韩国环境标志产品评价中的应用研究 总被引:2,自引:0,他引:2
中国在大力发展和推广环境标志产品的同时,对环境标志产品的系统评价工作却显得薄弱,仍主要停留在能源消耗、污染物排放、废弃回收等单一因素或简单组合方式,缺乏客观性、全面性。因此借鉴国外有关先进经验,尽快建立系统的环境标志产品评价体系是很有必要的。韩国环境标志产品LCA评价的最大优点是将复杂、专业的数据转变为易于国民理解的简单形式,而有利于环境标志产品的宣传与发展。文章以LCA法在评价韩国环境标志产品中的应用为实例,系统说明其评价过程,并探讨其优势和不足,为中国相关工作的开展提供可借鉴的经验。 相似文献
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255.
公路声屏障计算机辅助设计系统初步研究与实现 总被引:4,自引:1,他引:4
基于CAD二次开发技术的基本原理,步骤和方法,研究了声屏障计算机辅助设计系统的框架和结构,利用Visual Ba-sic的ActiveX Automaiton技术,初步开发了基于AutoCAD的公路声屏障计算机辅助设计软件,该软件在输入必要的环境条件和公路噪声的参数后,可自由进行公路交通噪声预测,评价和声屏的设计,并以表格的形式输出交通噪声预测值,以AutoCAD图形格式输出声屏障设计平面图,断面图,立面图等以及有无声屏障时交通噪声的空间等声级曲线图。 相似文献
256.
Integrated assessment (IA) can be defined as a structured process of dealing with complex issues, using knowledge from various
scientific disciplines and/or stakeholders, such that integrated insights are made available to decision makers (J. Rotmans,
Enviromental Modelling and Assessment 3 (1998) 155). There is a growing recognition that the participation of stakeholders
is a vital element of IA. However, only little is known about methodological requirements for such participatory IA and possible
insights to be gained from these approaches. This paper summarizes some of the experiences gathered in the ULYSSES project,
which aims at developing procedures that are able to bridge the gap between environmental science and democratic policy making
for the issue of climate change. The discussion is based on a total of 52 IA focus groups with citizens, run in six European
and one US city. In these groups, different computer models were used, ranging from complex and dynamic global models to simple
accounting tools. The analysis in this paper focuses on the role of the computer models. The findings suggest that the computer
models were successful at conveying to participants the temporal and spatial scale of climate change, the complexity of the
system and the uncertainties in our understanding of it. However, most participants felt that the computer models were less
instrumental for the exploration of policy options. Furthermore, both research teams and participants agreed that despite
considerable efforts, most models were not sufficiently user-friendly and transparent for being accessed in an IA focus group.
With that background, some methodological conclusions are drawn about the inclusion of the computer models in the deliberation
process. Furthermore, some suggestions are made about how given models should be adapted and new ones developed in order to
be helpful for participatory IA.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
257.
为了深入探讨絮体破碎行为对其分形成长及结构的影响,借助一种简化的絮体破碎模式对絮体破碎/再形成过程进行计算机模拟。通过对比分析破碎前后虚拟絮体的形态特征及其统计特性,得出如下主要结论:(1)絮体发生破碎后,所形成碎片的形态特征直接影响着再形成絮体的形态及恢复程度;(2)絮体外围枝杈结构的破坏,有利于运动粒子进入絮体内部或者均匀地排列在凝聚核周围,改善絮体质心附近颗粒的空间分布,从而有效地提高其致密性和抗剪切破坏能力;(3)在絮体分形成长过程中,存在一个使其由各向同性向各向异性过渡的临界状态,之后发育良好的枝杈对其余枝杈生长的抑制作用增强。此外,在实际操作时还应严格控制絮凝体系的物化条件,不宜使絮体过度破碎,以获得较好的絮凝效果。 相似文献
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