全文获取类型
收费全文 | 43392篇 |
免费 | 489篇 |
国内免费 | 1405篇 |
专业分类
安全科学 | 1224篇 |
废物处理 | 1806篇 |
环保管理 | 5707篇 |
综合类 | 7549篇 |
基础理论 | 12261篇 |
环境理论 | 22篇 |
污染及防治 | 11149篇 |
评价与监测 | 2641篇 |
社会与环境 | 2560篇 |
灾害及防治 | 367篇 |
出版年
2022年 | 411篇 |
2021年 | 357篇 |
2020年 | 285篇 |
2019年 | 347篇 |
2018年 | 1055篇 |
2017年 | 1028篇 |
2016年 | 1192篇 |
2015年 | 800篇 |
2014年 | 1133篇 |
2013年 | 2996篇 |
2012年 | 1488篇 |
2011年 | 2401篇 |
2010年 | 1857篇 |
2009年 | 1874篇 |
2008年 | 2299篇 |
2007年 | 2470篇 |
2006年 | 1633篇 |
2005年 | 1454篇 |
2004年 | 1305篇 |
2003年 | 1360篇 |
2002年 | 1331篇 |
2001年 | 1635篇 |
2000年 | 1158篇 |
1999年 | 736篇 |
1998年 | 618篇 |
1997年 | 592篇 |
1996年 | 598篇 |
1995年 | 644篇 |
1994年 | 554篇 |
1993年 | 497篇 |
1992年 | 526篇 |
1991年 | 469篇 |
1990年 | 486篇 |
1989年 | 510篇 |
1988年 | 424篇 |
1987年 | 362篇 |
1986年 | 321篇 |
1985年 | 366篇 |
1984年 | 356篇 |
1983年 | 395篇 |
1982年 | 381篇 |
1981年 | 323篇 |
1980年 | 287篇 |
1979年 | 321篇 |
1978年 | 259篇 |
1977年 | 230篇 |
1976年 | 235篇 |
1975年 | 228篇 |
1973年 | 212篇 |
1972年 | 226篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
981.
分析了救灾行为的经济学特性,提出救灾应包括两方面的内容,一方面它是一种人道主义救助,另一方面,它又是一种投资活动。指出帮助灾区恢复生产是整个社会扩大再生产的组成部分.并通过分析阐明摆脱以往单纯将救灾看成是人道主义救助的旧观点,充分考虑到在经济社会里救灾行为的经济学特点,用经济学原理指导救灾工作. 相似文献
982.
气象卫星遥感在干旱监测中的应用 总被引:23,自引:1,他引:23
本文根据NOAA极轨气象卫星AVHRR资料计算生成植被指数相对距平图用于旱情监测,并在江苏省1994年特大干旱中进行了应用服务 相似文献
983.
In 1992 a comprehensive health-promotion project was initiated in seven nursing-homes in the Netherlands. This project was designed to implement an ergonomic-educational programme, with the intention of reducing physical workload and to bring about safe working in order to prevent work-related musculoskeletal complaints. After a period of external support, employees of the nursing-homes should be able to proceed with the programme independently. In this paper the content of the programme and its underlying strategies and theories are described. So far, the programme has got off to a good start in all the nursing-homes. Positive effects of the programme could be demonstrated and guidelines and protocols for safe working were introduced. However, it is as yet too early for definitive conclusions to be drawn regarding the aspect of continuity. 相似文献
984.
The use of pressure-volume-temperature (PVT) studies in processing of a biodegradable plastic composition made from soy protein
isolate and corn starch is described. The ability of PVT measurements to predict the combined effects of pressure, volume,
and temperature effects is demonstrated. The results show that the PVT relations of the plastic can be predicted by using
a regression analysis similar to the Tait equations of state. A change in slope of the PVT curves was observed at around 80‡C,
which is ascribed to the glass-transition process of the plastic. Evidence of onset of thermal degradation of the plastic
was observed at ca. 160‡C under 0 to 200 MPa isobaric pressure. This thermal degradation precluded determination of the crystal
melting point of the plastic. 相似文献
985.
通过对安全投资与事故经济损失的规律性的分析研究,确立安全投资与经济效益的内在关系,进一步探索在我国现有财力和安全水平的基础上,找准安全投资的投向,优化安全投资的合理分配,从而实现最大限度地提高企业安全生产水平和安全投资效益。为政府部门或企业提供一套经过优化、科学合理、操作性又比较强的安全投资方案,供各级领导进行安全决策,实现本部门、本单位的安全投资计划时参考 相似文献
986.
987.
Jeffrey H. Kahn Kimberly T. Schneider Theresa M. Jenkins‐Henkelman Laura L. Moyle 《组织行为杂志》2006,27(6):793-807
The authors investigated whether the relationship between the contents of emotional social support and job burnout among high‐school teachers is spurious because of the role of dispositional positive and negative affectivity. A national sample of 339 teachers was surveyed via a web‐based procedure. Hierarchical regression analyses did not support spuriousness; emotional social support was uniquely predictive of three dimensions of burnout controlling for affectivity. As positive emotional social support increased, emotional exhaustion and cynicism decreased, and professional efficacy increased. As negative emotional social support increased, emotional exhaustion and cynicism also increased. Commonality analyses based on the present data and data reported by K. L. Zellars and P. L. Perrewé (2001; Journal of Applied Psychology, 86, 459–467) provided additional support for the unique role of emotional social support on burnout, but these analyses suggest a greater role of affectivity than emotional social support. These findings have implications for research on burnout as well as the prevention of burnout among teachers. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
988.
This study meta‐analyzed the relationships between locus of control (LOC) and a wide range of work outcomes. We categorized these outcomes according to three theoretical perspectives: LOC and well‐being, LOC and motivation, and LOC and behavioral orientation. Hypotheses reflecting these three perspectives were proposed and tested. It was found that internal locus was positively associated with favorable work outcomes, such as positive task and social experiences, and greater job motivation. Our findings are discussed in relation to research on core self‐evaluation and the Big Five personality traits. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
989.
Aaron I. Packman Andrea Marion Mattia Zaramella Cheng Chen Jean-François Gaillard Denis T. Keane 《Water, Air, & Soil Pollution: Focus》2006,6(5-6):433-442
Hyporheic exchange is known to provide an important control on nutrient and contaminant fluxes across the stream-subsurface
interface. Similar processes also mediate interfacial transport in other permeable sediments. Recent research has focused
on understanding the mechanics of these exchange processes and improving estimation of exchange rates in natural systems.
While the structure of sediment beds obviously influences pore water flow rates and patterns, little is known about the interplay
of typical sedimentary structures, hyporheic exchange, and other transport processes in fluvial/alluvial sediments. Here we
discuss several processes that contribute to local-scale sediment heterogeneity and present results that illustrate the interaction
of overlying flow conditions, the development of sediment structure, pore water transport, and stream-subsurface exchange.
Layered structures are shown to develop at several scales within sediment beds. Surface sampling is used to analyze the development
of an armor layer in a sand-and-gravel bed, while innovative synchrotron-based X-ray microtomography is used to observe patterns
of grain sorting within sand bedforms. We show that layered bed structures involving coarsening of the bed surface increase
interfacial solute flux but produce an effective anisotropy that favors horizontal pore water transport while limiting vertical
penetration. 相似文献
990.
Elvis G. Ngwenya Maud Walsh Caroline A. Metosh‐Dickey Ralph J. Portier 《补救:环境净化治理成本、技术与工艺杂志》2006,16(2):79-90
Biological and physicochemical approaches were utilized in a treatment train for acid mine dis charge (AMD) waters. Anaerobic bioreactors, chemical precipitation reactors, and biopolymer chelation reactors, operated in static, semicontinuous, and continuous flow modes, removed significant quantities of metals and sulfates associated with AMD water. Static tests indicated accept able copper removal via precipitation by generation of hydrogen sulfide in anaerobic reactors. However, low pH affected the biopolymer coating in the chelation reactor, resulting in loss of bed surface. Corrections of AMD to pH > 7 resulted in some metal precipitationprior to biopolymer treatment. A series of static semicontinuous tests at pH 5.0 provided improved metal and sulfate removal. Copper (Cu+) was reduced to trace concentrations, while manganese (Mn+), although reduced, proved to be the most recalcitrant of the metals. © 2006 Wiley Periodicals, Inc. 相似文献