全文获取类型
收费全文 | 21660篇 |
免费 | 484篇 |
国内免费 | 4728篇 |
专业分类
安全科学 | 816篇 |
废物处理 | 1529篇 |
环保管理 | 2121篇 |
综合类 | 7756篇 |
基础理论 | 5006篇 |
环境理论 | 6篇 |
污染及防治 | 6332篇 |
评价与监测 | 1433篇 |
社会与环境 | 1309篇 |
灾害及防治 | 564篇 |
出版年
2024年 | 2篇 |
2023年 | 198篇 |
2022年 | 579篇 |
2021年 | 479篇 |
2020年 | 352篇 |
2019年 | 359篇 |
2018年 | 1880篇 |
2017年 | 1851篇 |
2016年 | 1781篇 |
2015年 | 957篇 |
2014年 | 987篇 |
2013年 | 1278篇 |
2012年 | 1464篇 |
2011年 | 2492篇 |
2010年 | 1518篇 |
2009年 | 1434篇 |
2008年 | 1749篇 |
2007年 | 1903篇 |
2006年 | 657篇 |
2005年 | 500篇 |
2004年 | 384篇 |
2003年 | 498篇 |
2002年 | 480篇 |
2001年 | 326篇 |
2000年 | 352篇 |
1999年 | 401篇 |
1998年 | 337篇 |
1997年 | 311篇 |
1996年 | 295篇 |
1995年 | 260篇 |
1994年 | 177篇 |
1993年 | 156篇 |
1992年 | 113篇 |
1991年 | 94篇 |
1990年 | 64篇 |
1989年 | 54篇 |
1988年 | 44篇 |
1987年 | 19篇 |
1986年 | 22篇 |
1985年 | 11篇 |
1984年 | 22篇 |
1983年 | 18篇 |
1982年 | 10篇 |
1981年 | 2篇 |
1935年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
541.
Lu Y Beeman RW Campbell JF Park Y Aikins MJ Mori K Akasaka K Tamogami S Phillips TW 《Die Naturwissenschaften》2011,98(9):755-761
We report that the abdominal epidermis and associated tissues are the predominant sources of male-produced pheromones in the
red flour beetle, Tribolium castaneum and, for the first time, describe the stereoisomeric composition of the natural blend of isomers of the aggregation pheromone
4,8-dimethyldecanal (DMD) in this important pest species. Quantitative analyses via gas chromatography–mass spectrometry showed
that the average amount of DMD released daily by single feeding males of T. castaneum was 878 ± 72 ng (SE). Analysis of different body parts identified the abdominal epidermis as the major source of aggregation
pheromone; the thorax was a minor source, while no DMD was detectable in the head. No internal organs or obvious male-specific
glands were associated with pheromone deposition. Complete separation of all four stereoisomers of DMD was achieved following
oxidation to the corresponding acid, derivatization with (1R, 2R)- and (1S, 2S)-2-(anthracene-2,3-dicarboximido)cyclohexanol to diastereomeric esters, and their separation on reversed-phase high-performance
liquid chromatography at −54°C. Analysis of the hexane eluate from Porapak-Q-collected volatiles from feeding males revealed
the presence of all four isomers (4R,8R)/(4R,8S)/(4S,8R)/(4S,8S) at a ratio of approximately 4:4:1:1. A walking orientation bioassay in a wind tunnel with various blends of the four synthetic
isomers further indicated that the attractive potency of the reconstituted natural blend of 4:4:1:1 was equivalent to that
of the natural pheromone and greater than that of the 1:1 blend of (4R,8R)/(4R,8S) used in commercial lures. 相似文献
542.
A postanal tail is a major synapomorphy of the phylum Chordata, which is composed of three subphyla: Vertebrata, Cephalochordata,
and Tunicata (Urochordata). Among tunicates, appendicularians are the only group that retains the tail in the adult, and the
adult tail functions in locomotion and feeding in combination with a cellulose-based house structure. Given the phylogenetic
position of tunicates, the appendicularian adult tail may possess ancestral features of the chordate tail. We assess the ultrastructural
development of the tail epidermis of the appendicularian Oikopleura dioica. The epidermis of the larval tail is enclosed by the larval envelope, which is a thin sheet similar to the outer tunic layer
of ascidian larvae. The epidermis of the adult tail seems to bear no tunic-like cellulosic integuments, and the tail fin is
a simple folding of the epidermis. Every epidermal cell, except for the triangular cells at the edge of the tail fin, has
a conspicuous matrix layer of fibrous content in the apical cytoplasm without enclosing membranes. The epidermis of the larval
tail does not have a fibrous matrix layer, suggesting the production of the layer during larval development and metamorphosis.
Zonulae adhaerentes firmly bind the epidermal cells of the adult tail to one another, and the dense microfilaments lining
the cell borders constitute a mechanical support for the cell membranes. The intracellular matrix, cell junctions, and cytoskeletons
probably make the tail epidermis a tough, flexible shell supporting the active beating of the oikopleuran adult tail. 相似文献
543.
544.
探索了电渗析法再生CO2电还原电解液的可行性。以HCOOK溶液作为CO2电还原反应后的模拟液,采用单室电渗析装置对其进行再生,考察了电流、时间、温度等操作条件对电流效率和再生率的影响,研究结果表明:在常温条件下,操作电流低于极限电流时,采用电渗析法再生CO2电还原电解液具有高的电流效率和再生率。 相似文献
545.
针对大蒜废水特点,采用了铁屑微电解-UASB-接触氧化工艺进行处理.运行结果表明:在设计进水水质、水量范围内,COD、BOD5、氨氮和ss去除率分别为98%、99%、70%和98%,出水各项指标均达到GB 8978--1996<污水综合排放标准>中的一级排放标准,系统运行费用为1.19元/m3. 相似文献
546.
以模拟印染废水和实际印染废水为实验对象,检验了一种新合成有机-无机复合絮凝剂(PST)的絮凝效果。结果表明,PST具有良好的絮凝性能。在受试条件下,絮凝效果与絮凝剂投加量、染料浓度有较大相关性。废水的pH值应用范围较宽;搅拌时间对COD去除率和脱色率没有显著影响。采用PST处理广东省高明市某印染厂的印染废水后,COD去除率为75.16%,脱色率为76.18%,处理效果良好,处理成本明显低于目前市场上普遍使用的聚铝等絮凝剂。 相似文献
547.
548.
Remediation of copper polluted red soils with clay materials 总被引:2,自引:0,他引:2
Attapulgite and montmorillonite were utilized to remediate heavy metal polluted red soils in Guixi City, Jiangxi Province, China.
The e ects of clay minerals on availability, chemical distribution, and biotoxicity of Cu and Zn were evaluated. The results provided
a reference for the rational application of clay materials to remediate heavy metal contaminated soils. From the sorption experiment,
the maximum adsorbed Cu2+ by attapulgite and montmorillonite was 1501 and 3741 mg/kg, respectively. After polluted red soil was
amended with attapulgite or montmorillonite and cultured at 30 and 60 days, soil pH increased significantly compared to the control. An
8% increase in the amount of montmorillonite in soil and 30 days incubation decreased acid exchangeable Cu by 24.7% compared to the
control red soil. Acid exchangeable Cu decreased with increasing amounts of attapulgite and montmorillonite, with best remediation
e ect reached at a dose of 8%. Results also showed that the Cu poisoning e ect on earthworms was reduced with the addition of
attapulgite and montmorillonite. Montmorillonite showed the best e ect, with the addition of a 2% dose the mortality of earthworms
decreased from 60% to zero compared to the control. Our results indicated that the bioavailability of Cu in soils was reduced more
e ectively with the application of montmorillonite than attapulgite. 相似文献
549.
The competition between submersed plants has been recognized as an important factor influencing the structure of plant communities
in shallow lakes. The ability of different species to take up and store nutrients from the surrounding ambience varies, and hence plant
community structure might be expected to affect the cycling of nutrients in lake ecosystems. In this study, the uptake of phosphorus
by Hydrilla verticillata and Vallisneria natans was studied and compared in monoculture and competitive mixed-culture plantings.
Results showed that for both studied species the phosphorus concentrations of different tissues and of whole plants was unaffected by
competition. However, the quantity of phosphorus accumulated by whole plants of H. verticillata was significantly higher in mixture
culture than in monoculture, while that of V. natans was lower in the mixed culture. The results indicated that H. verticillata has a
competitive advantage over V. natans, when the two species are grown in competition, and is able to accumulate a greater quantity of
phosphorus. 相似文献
550.