全文获取类型
收费全文 | 1946篇 |
免费 | 214篇 |
国内免费 | 772篇 |
专业分类
安全科学 | 362篇 |
废物处理 | 14篇 |
环保管理 | 200篇 |
综合类 | 1566篇 |
基础理论 | 217篇 |
污染及防治 | 161篇 |
评价与监测 | 138篇 |
社会与环境 | 203篇 |
灾害及防治 | 71篇 |
出版年
2024年 | 26篇 |
2023年 | 79篇 |
2022年 | 135篇 |
2021年 | 180篇 |
2020年 | 115篇 |
2019年 | 144篇 |
2018年 | 92篇 |
2017年 | 130篇 |
2016年 | 153篇 |
2015年 | 149篇 |
2014年 | 124篇 |
2013年 | 175篇 |
2012年 | 170篇 |
2011年 | 213篇 |
2010年 | 131篇 |
2009年 | 107篇 |
2008年 | 120篇 |
2007年 | 125篇 |
2006年 | 114篇 |
2005年 | 86篇 |
2004年 | 61篇 |
2003年 | 71篇 |
2002年 | 52篇 |
2001年 | 34篇 |
2000年 | 19篇 |
1999年 | 18篇 |
1998年 | 17篇 |
1997年 | 18篇 |
1996年 | 14篇 |
1995年 | 10篇 |
1994年 | 7篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有2932条查询结果,搜索用时 15 毫秒
131.
132.
133.
在不同工况下,通过采取不同的岩土体物理力学参数来计算沙坝沟滑坡的稳定系数并分析影响因素,得到影响该滑坡稳定性的主要因素为降雨、地下水作用及人类工程活动,在一定条件下可能成为滑坡失稳破坏的诱导因素。最后为滑坡防治提出一些建议,对滑坡的预测和防护提供依据。 相似文献
134.
Zhalong National Nature Reserve in the northeast of China is a large wetland and a habitat of hundreds species of fauna and
flora. The rare red-crowned crane is one kind of endangered birds in it. Recently, Zhalong wetland is shrinking and it encounters
many problems including occasional fires, bad water quality, human activities, etc. In order to find out a proper way to protect
and restore the wetland, this study, using a geographic information system, the global positioning system and remote sensing
techniques, analyses the spatial characteristics of the changes in marsh landscape pattern and examines the driving factors
for these changes. Data sources include 8 Landsat Thematic Mapper satellite images of Zhalong area in the period of 1986–2002
and the investigation information on site. Based on the analysis of changes of marsh area and annual precipitation during
the 16 years, it is found that there is a close correlation between annual precipitation and marsh area. It means that climate
is one of driving factors of marsh pattern changes. To understand influences of other kinds of land uses on marsh spatial
distribution in Zhalong wetland, this paper analyses the relationship between marsh and different kinds of land uses, such
as water surface, residential area, farmland, salina land and grass land, respectively. According to the patch analysis theory,
a fragmental index and a fractal dimension of the marsh are calculated with perimeter-area method. The results indicate that
the marsh pattern is affected by human activities significantly. In addition, the location alteration of marsh centroid point
over the 16 years is studied. The movement trace of marsh centroid point is concerned with different hydrological situation
in different areas of the wetland. In summary the characteristics of the marsh landscape pattern evolution during the 16 years
are affected by multiple driving factors. The main driving factors are climate, human activities, distribution of other kinds
of land uses and hydrological situation in different areas. 相似文献
135.
Schröder P Scheer CE Diekmann F Stampfl A 《Environmental science and pollution research international》2007,14(2):114-122
Background, Aim and Scope
Numerous herbicides and xenobiotic organic pollutants are detoxified in plants to glutathione conjugates. Following this enzyme
catalyzed reaction, xenobiotic GS-conjugates are thought to be compartmentalized in the vacuole of plant cells. In the present
study, evidence is presented for long range transport of these conjugates in plants, rather than storage in the vacuole. To
our knowledge this is the first report about the unidirectional long range transport of xenobiotic conjugates in plants and
the exudation of a glutathione conjugate from the root tips. This could mean that plants possess an excretion system for unwanted
compounds which give them similar advantages as animals.
Materials and Methods:
Barley plants (Hordeum vulgare L. cv. Cherie) were grown in Petri dishes soaked with tap water in the greenhouse.
- Fluorescence Microscopy. Monobromo- and Monochlorobimane, two model xenobiotics that are conjugated rapidly in plant cells
with glutathione, hereby forming fluorescent metabolites, were used as markers for our experiments. Their transport in the
root could be followed sensitively with very good temporal and spatial resolution. Roots of barley seedlings were cut under
water and the end at which xenobiotics were applied was fixed in an aperture with a thin latex foil and transferred into a
drop of water on a cover slide. The cover slide was fixed in a measuring chamber on the stage of an inverse fluorescence microscope
(Zeiss Axiovert 100).
- Spectrometric enzyme assay. Glutathione S-transferase (GST) activity was determined in the protein extracts following established
methods. Aliquots of the enzyme extract were incubated with 1-chloro-2,4-dinitrobenzene (CDNB), or monochlorobimane. Controls
lacking enzyme or GSH were measured.
- Pitman chamber experiments. Ten days old barley plants or detached roots were inserted into special incubation chambers, either
complete with tips or decapitated, as well as 10 days old barley plants without root tips. Compartment A was filled with a
transport medium and GSH conjugate or L-cysteine conjugate. Compartments B and C contained sugar free media. Samples were
taken from the root tip containing compartment C and the amount of conjugate transported was determined spectro-photometrically.
Results:
The transport in roots is unidirectional towards the root tips and leads to exsudation of the conjugates at rates between
20 and 200 nmol min-1. The microscopic studies have been complemented by transport studies in small root chambers and spectroscopic
quantification of dinitrobenzene-conjugates. The latter experiments confirm the microscopic studies. Furthermore it was shown
that glutathione conjugates are transported at higher rates than cysteine conjugates, despite of their higher molecular weights.
This observation points to the existence of glutathione specific carriers and a specific role of glutathione in the root.
Discussion:
It can be assumed that long distance transport of glutathione conjugates within the plant proceeds like GSH or amino acid
transport in both, phloem and xylem. The high velocity of this translocation of the GS-X is indicative of an active transport.
For free glutathione, a rapid transport-system is essential because an accumulation of GSH in the root tip inhibits further
uptake of sulfur. Taking into account that all described MRP transporters and also the GSH plasmalemma ATPases have side activities
for glutathione derivatives and conjugates, co-transport of these xenobiotic metabolites seems credible.
- On the other hand, when GS-B was applied to the root tips from the outside, no significant uptake was observed. Thus it can
be concluded that only those conjugates can be transported in the xylem which are formed inside the root apex. Having left
the root once, there seems to be no return into the root vessels, probably because of a lack of inward directed transporters.
Conclusions:
Plants seem to possess the capability to store glutathione conjugates in the vacuole, but under certain conditions, these
metabolites might also undergo long range transport, predominantly into the plant root. The transport seems dependent on specific
carriers and is unidirectional, this means that xenobiotic conjugates from the rhizosphere are not taken up again. The exudation
of xenobiotic metabolites offers an opportunity to avoid the accumulation of such compounds in the plant.
Recommendations and Perspectives:
The role of glutathione and glutathione related metabolites in the rhizosphere has not been studied in any detail, and only
scattered data are available on interactions between the plant root and rhizosphere bacteria that encounter such conjugates.
The final fate of these compounds in the root zone has also not been addressed so far. It will be interesting to study effects
of the exuded metabolites on the biology of rhizosphere bacteria and fungi. 相似文献
136.
Relation of waste generation and composition to socio-economic factors: a case study 总被引:3,自引:0,他引:3
Bandara NJ Hettiaratchi JP Wirasinghe SC Pilapiiya S 《Environmental monitoring and assessment》2007,135(1-3):31-39
To develop an effective waste management strategy for a given region, it is important to know the amount of waste generated
and the composition of the waste stream. Past research has shown that the amount of waste generated is proportional to the
population and the average mean living standards or the average income of the people. In addition, other factors may affect
the amount and composition of waste. These are climate, living habits, level of education, religious and cultural beliefs,
and social and public attitudes. This paper presents the findings of a study carried out in a suburban municipal area in Sri
Lanka to determine the solid waste generation rate and waste composition based on field surveys and to determine the related
socio-economic factors. A database was developed that included information on the quantity and composition of waste generated
in a sample of households in the study area over a time period. The collected data was analysed to relate waste generation
and composition data to various socio-economic factors. Over 400 sample households were selected for the study using a stratified
random sampling methodology based on municipal wards and property values. A technique that considers both the number of households
in a particular income group (property value range) and the standard deviation of property values within a given income group
was used to determine the appropriate sample size for each municipal ward. Through category and regression analyses, the quantities
of waste and waste composition were related to several socio-economic factors. The paper describes the basis for the sample
selection, the methodology adopted for data collection, the socio-economic parameters used for the analysis, and the relationships
developed from the analysis. 相似文献
137.
138.
生态恢复过程中的种群遗传学考虑 总被引:9,自引:3,他引:6
陈小勇 《长江流域资源与环境》2000,9(3):313-319
生态恢复是生态科学的最终实验,从种群角度看,恢复的目标是使种群(尤其是优势种或建群种)到具有生长、繁殖和适应进化变化的能力。要达到这个目标,种群遗传学知识必不可少。遗传变异是物种适应变化环境的基础,而局部适应则是种群适应局部环境遗传分化的结果,它们在生态恢复中起着重要的作用。分析了生态恢复过程中影响种群遗传变异因素,主要有取样误差和小种群效应(主要是瓶颈或建立者事件及其以后的近交和漂变等),在进行 相似文献
139.
本文运用IPCC的二氧化碳排放量测算方法,在省际层面测度了我国家庭部门直接能源消费碳排放,并基于扩展的STIRPAT和Kaya模型,构建家庭部门直接能源消费碳排放影响因子动态面板数据模型,对我国2003-2012年分省面板数据样本及城乡子样本进行系统GMM估计。本文研究表明,第一,我国城乡家庭部门碳排放总量和人均碳排放在近十年都呈快速上升趋势,家庭部门碳排放的空间分布具有明显的地域差异特征,高碳排放地区主要集中在东、中部地区,西部地区的碳排放水平较低;第二,城乡家庭部门生活能源消费的上期碳排放量对本期碳排放产生重要的正向影响,这反映出我国家庭部门碳排放具有显著的惯性特征和路径依赖性,是一种动态自适应机制;人口规模、居民消费水平、能源消费结构、碳排放强度、能源消费强度和城镇化因素,都对我国居民能源消费碳排放总量及人均碳排放具有显著的影响,城乡之间的家庭能源消费碳排放驱动因素存在差异。本文研究得到如下启示及政策含义:家庭部门碳减排将是一个有步骤、分区域的渐进过程,我国碳减排政策应当兼顾消费升级和碳排放的双重目标,努力构建分层次碳减排的适应性预期机制。具体而言,一方面应着眼于引导和激励居民低碳消费,缓解人口规模增加、消费水平提升和城镇化对家庭部门碳减排的压力;另一方面要通过能源价格改革、财政政策和环境规制政策等优化我国能源消费结构,不断降低煤炭消费比重,提高清洁能源的消费。同时,通过技术创新、设备改造等科技手段提高煤炭利用效率,降低碳排放强度,这些政策将更有利于城镇家庭部门碳减排。 相似文献
140.
少数民族聚集区乡村空间重构的影响机理——以新疆和田地区为例 总被引:1,自引:0,他引:1
乡村空间重构不仅是农村现代化的必由之路,还是实现土地集约利用的重要途径。和田地区,经济发展缓慢,其村庄基础设施差,而且由于人口迅速发展,其人地矛盾突出,因此对和田地区进行乡村空间重构势在必行。基于此,本文依据2015年对和田地区入户调查的1 162份问卷,选取了农户的个体特征、家庭特征、职业特征和居住环境特征四个方面的19个影响因素作为自变量,选取农户是否愿意整治作为因变量,运用二元Logistic模型对农户迁居至中心村的影响因素和迁居意愿进行了回归分析。对问卷的统计可知,有64%的被调查者表示接受整治。通过与其他区域的调查对比可知,经济越是发达的地区,其中心村整治的进展越快,农民接受整治的意愿也越强烈。相反,经济越不发达的地区,其中心村整治的进展越缓慢,农民接受搬迁的意愿越低。农户是否愿意接受乡村重构,是农户家庭特征、居民点的基础设施和农户的职业特征共同作用的结果。就农户的家庭特征来看,家庭劳动力数量偏少、家庭年收入越高、耕地面积适中的农户,其搬迁意愿是最强烈的。在农户的职业特征中,愿意参与土地流转、有外出务工经验的农户,其搬迁意愿是最强烈的。在环境特征中,若农户对居住环境和现居住村的建设越不满意、居住环境中需要改善的项目越多,农户的搬迁意愿越强烈。因此,对于和田地区来说,在引导居民集中居住的同时,要引导农户流转土地,促进更多人就业,积极推动特色农业的发展,走农业现代化的道路,以促进农民收入的持续增长。此外,农户对于整治的一个很重要的期望就是改善居住环境,因此在未来的村庄总体建设和规划中,应积极改善村庄内基础设施,并与居住建设同步进行。一直以来,对少数民族聚集区的乡村空间重构的研究比较少。本文对和田地区中心村的研究,是对少数民族地区乡村空间重构研究的重要补充。 相似文献