全文获取类型
收费全文 | 5886篇 |
免费 | 784篇 |
国内免费 | 3538篇 |
专业分类
安全科学 | 614篇 |
废物处理 | 253篇 |
环保管理 | 653篇 |
综合类 | 5891篇 |
基础理论 | 984篇 |
环境理论 | 1篇 |
污染及防治 | 1206篇 |
评价与监测 | 251篇 |
社会与环境 | 239篇 |
灾害及防治 | 116篇 |
出版年
2024年 | 19篇 |
2023年 | 172篇 |
2022年 | 308篇 |
2021年 | 390篇 |
2020年 | 349篇 |
2019年 | 368篇 |
2018年 | 302篇 |
2017年 | 295篇 |
2016年 | 411篇 |
2015年 | 462篇 |
2014年 | 522篇 |
2013年 | 601篇 |
2012年 | 723篇 |
2011年 | 692篇 |
2010年 | 510篇 |
2009年 | 533篇 |
2008年 | 396篇 |
2007年 | 585篇 |
2006年 | 515篇 |
2005年 | 369篇 |
2004年 | 307篇 |
2003年 | 270篇 |
2002年 | 211篇 |
2001年 | 182篇 |
2000年 | 161篇 |
1999年 | 125篇 |
1998年 | 75篇 |
1997年 | 83篇 |
1996年 | 55篇 |
1995年 | 52篇 |
1994年 | 38篇 |
1993年 | 30篇 |
1992年 | 29篇 |
1991年 | 13篇 |
1990年 | 10篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
1.
以天津市河道、水库为研究对象,在藻类增殖期采用连续流动法与碱性过硫酸钾消解法对水体中总氮进行比对监测,同时分析水中藻类分类和藻细胞密度。试验表明:虽然两种方法测定总氮的结果精密度基本相同,但二者之间的系统误差存在显著差异,连续流动法较碱性过硫酸钾消解法的测定结果低5.4%。两种方法测定总氮结果的相对偏差与水体中藻细胞密度呈正相关性,当水体中藻细胞密度﹥2.41×108L-1时,对连续流动法测定总氮的结果产生显著影响,相对偏差超过标准规范要求。 相似文献
2.
3.
4.
A new approach to Assess Atmospheric Nitrogen Deposition by Way of Standardized Exposition of mosses
A standardized method of moss exposition for assessing variations in nitrogen deposition was tested in the western part of
Germany. Six pleurocarpous moss species were transplanted to two sites differing in their deposition rates but being comparable
as to their climatic conditions. The mosses were exposed in standardized containers over a period of 12 months; the focus
of interest was the effect of N deposition on nitrogen content and on 15N natural abundance (δ15N-values). Within the first nine months only trends could be observed. However, after one year all species tested showed significantly
higher N concentrations at the highly polluted site. Besides, more negative δ15N-values possibly reflecting the higher ammonium input were detected at this site. Surprisingly, most of the plants though
being kept in plastic containers without a favourable substratum did not show any conspicuous deficiency symptoms. The potential
advantages of a standardized moss exposition for N monitoring purposes are discussed. It is concluded that the method presented
here can yield significant results in particular if the number of testing sites is increased. 相似文献
5.
A. L. Heathwaite 《Chemistry and Ecology》1993,8(3):217-231
Although most research has focussed on inorganic nutrient forms of nitrate (NO-3) and phosphorus (PO34) in runoff and receiving waters, nitrogen loss from agricultural land can also occur in organic and ammonium-nitrogen form; phosphorus losses, although often dominated by particulate transport, may occur in soluble organic and inorganic form. Furthermore, fluxes between different species may take place during transport from the land to the stream and as a result of in-stream, in-river or in-lake transformations. Knowledge of the spatial and temporal variation in all nitrogen species and phosphorus fractions in a drainage basin is therefore essential if the wider environmental significance of elevated nutrient concentrations in natural waters are to be assessed. This paper reviews recent work on N and P losses from agricultural land and presents some results from two intensive agricultural catchments: Slapton, Devon and the river Windrush catchment in the Cotswolds. 相似文献
6.
The Clean Development Mechanism (CDM) under the Kyoto Protocol to the UN Framework Convention on Climate Change (UNFCCC) has
its origins in the decade of UNFCCC negotiations. ‘Joint implementation’ and ‘activities implemented jointly pilot’ opened
the door for the project-based mechanisms between developed and developing countries. The US proposal of the Joint Implementation
in the Kyoto Protocol negotiations was almost identical with CDM approved in Kyoto; however, a detour around the Clean Development
Fund (CDF) concept raised by Brazil in the negotiations catalyzed the mutual understanding on the win-win nature of the concept
of joint implementation.CDM has been played an important role to bridge the developed and developing countries in its development
process initiated as the joint implementation in the UNFCCC, and can lead to the cooperative future in the implementation
stage starting from the year 2003, including the development of future commitments beyond 2013.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
Frede Ø. Andersen Michael Jørgensen Henning S. Jensen 《Water, Air, & Soil Pollution: Focus》2006,6(5-6):465-474
One of the methods to diminish the internal phosphorus (P) loading is inactivation of P by aluminum (Al). After addition of
Al to lake water an Al(OH)3 floc is formed, which settles to the bottom and initially form a lid on the sediment surface. The effects of Chironomus
plumosus larvae on sediment nutrient fluxes and P binding-sites in the sediment after addition of Al were tested. C.
plumosus larvae were added to sediment cores in which sediment–water fluxes of nutrients were measured four times. After one month,
the sediment was sectioned with depth and P fractions were measured by sequential chemical extraction. The chironomids created
burrows through the Al layer which caused a significantly increased efflux of P from the Al treated sediment, because the
P had only limited contact to the added Al. The chironomids also affected the P fractions in the sediment by their bioturbating
activity. Thus, they caused increased Al concentrations in the upper part of the Al treated sediment. This created an enhanced
contact between Al and P in the upper 7 cm of the sediment and, as a result, an increased binding of P to Al and a lowered
porewater P. The DIP efflux is therefore expected to be lowered after the initial phase. Al had no effects on the nitrogen
fluxes, but the chironomids enhanced the release, and decreased the release or increased the uptake by the sediments. 相似文献
8.
论环境产业 总被引:1,自引:0,他引:1
曹曼 《中国人口.资源与环境》2008,18(6)
本文在可持续发展视角下,把环境的保护、修复、维护的生产活动及与之直接相关的服务活动称为环境产韭,包括发挥减少、避免污染环境作用的资源再利用鼗和发挥治理污染物与修复、改善环境作用的环境维护业.通过探讨环境产业的内涵、发展历程、运行机制和在产业体系中的位置与作用,指出环境产业是在法规保障下政府强行推动产生和发展起来的,是产业体系中不可缺少的重要组成部分;考虑自然环境对社会行为的影响,改进政府行为构建适台环境产业与传统产业协调发展的经济体制是加快发展环境产业的关键. 相似文献
9.
10.
我国南方冰雪灾害的特征与城市救灾对策研究 总被引:3,自引:1,他引:2
在对2008年初中国南方所发生的冰雪灾害的损失、影响和成因进行分析的基础上,指出该次灾害具有受灾范围的全面性、灾害过程的发展性和救灾行动的艰难性等特征,阐明冰雪灾害在城市会造成停电停水、交通瘫痪和通讯中断等严重灾情,进而引发断油断粮、物价飞涨和人心恐慌等综合性灾害。通过冰雪灾害对城市救灾行动的总结,指出冰雪灾害给城市政府的深刻启示在于城市规模的急速扩张必须同时加强防灾救灾的软硬件建设,并提出城市必须采取持久开展防灾救灾知识宜传教育、大力加强防灾救灾基础设施建设、科学制订各类灾害的专业性应急预案和努力构建协同联动救灾机制等对策,有效提升城市应对灾害的能力,减少灾害造成的损失。 相似文献