全文获取类型
收费全文 | 645篇 |
免费 | 11篇 |
国内免费 | 7篇 |
专业分类
安全科学 | 52篇 |
废物处理 | 19篇 |
环保管理 | 167篇 |
综合类 | 86篇 |
基础理论 | 128篇 |
环境理论 | 3篇 |
污染及防治 | 124篇 |
评价与监测 | 55篇 |
社会与环境 | 25篇 |
灾害及防治 | 4篇 |
出版年
2023年 | 2篇 |
2022年 | 9篇 |
2021年 | 11篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2018年 | 15篇 |
2017年 | 13篇 |
2016年 | 26篇 |
2015年 | 9篇 |
2014年 | 17篇 |
2013年 | 57篇 |
2012年 | 23篇 |
2011年 | 39篇 |
2010年 | 16篇 |
2009年 | 20篇 |
2008年 | 27篇 |
2007年 | 31篇 |
2006年 | 24篇 |
2005年 | 27篇 |
2004年 | 11篇 |
2003年 | 27篇 |
2002年 | 22篇 |
2001年 | 11篇 |
2000年 | 15篇 |
1999年 | 10篇 |
1998年 | 3篇 |
1997年 | 10篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 13篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1991年 | 7篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 11篇 |
1983年 | 8篇 |
1982年 | 11篇 |
1981年 | 16篇 |
1980年 | 9篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1947年 | 1篇 |
排序方式: 共有663条查询结果,搜索用时 656 毫秒
471.
Summary. Male locust borers, Megacyllene robiniae
(Förster), responded to females only after contacting them
with their antennae, indicating that mate recognition was
mediated by a contact sex pheromone. GC-MS analyses of
whole-body extracts of males and females determined that the
profiles of compounds in the extracts were qualitatively similar,
but differed considerably in the ratios of compounds
between sexes. Biological activities of reconstructed blends
of the most abundant straight-chain (nC23, nC24, nC25, nC26),
methyl-branched (3me-C23, 3me-C25), and unsaturated
(Z9:C23, Z9:C25, Z9:C27 compounds in extracts from females
were assessed in arena bioassays, assessing four distinct steps
in the mating behavior sequence of males (orientation, arrestment,
body alignment, mounting and attempting to couple the
genitalia). Males were unresponsive to freeze-killed, solventwashed
females treated with blends of straight-chain and
methyl-branched alkanes, but responded strongly to females
treated with the blend of alkenes. Further trials determined
that the complete sequence of mating behaviors, up to and
including coupling the genitalia, was elicited by Z9:C25 alone.
Z9:C25 comprised 16.4 ± 1.3% of the total hydrocarbons in
whole-body hexane extracts of females and was co-dominant
with two other hydrocarbons that were not active. In contrast,
in solid phase microextraction (SPME) wipe samples from
several areas of the cuticle, Z9:C25 appeared as the single
dominant peak, comprising 34.6 – 37.8% of the sampled
hydrocarbons. Our data indicate that Z9:C25 is a contact sex
pheromone of M. robiniae, being the most abundant hydrocarbon
on the surface of the cuticular wax layer of females
where it is readily accessible to the antennae of males. 相似文献
472.
473.
Postelsia palmaeformis were collected from the lower intertidal at Pigeon Point, California, USA, in May 1987, and the proximate composition and allocation of energy to the various body components were determined. The holdfast and stipe have a proximate composition (% dry weight) of ca. 40% ash, 5.3% protein, 1% lipid, 2% soluble carbohydrate, and 55% insoluble carbohydrate. The fronds have a proximate composition of ca. 25% ash, 6.5% protein, 2% lipid, 3% soluble carbohydrate, and 65% insoluble carbohydrate. The energetic level was ca. 12 kJ g-1 dry wt and ca. 19 kJ g-1 ash-free dry wt. The relative proportion of three plant components varied, comprising 26, 39, and 35% wet wt and 20, 42, and 38% kJ for the holdfast, stipe, and fronds, respectively. A plant with a basal stipe diameter of 33 mm contains 114 g wet wt and 266 kJ. The maximal density found in May 1987 was 826 plants, 49 301 g wet wt, and 106 157 kJ m-2.P. palmaeformis differs in these characteristics from another intertidal pheophyte,Durvillaea antarctica, that is found in a high-energy intertidal zone. 相似文献
474.
Summary. The purpose of this study was to identify plant volatiles that provide host location cues for adult females of the gall wasp Antistrophus rufus Gillette (Hymenoptera: Cynipidae). Larvae of this species inhabit flowering stems of the prairie perennial Silphium laciniatum L. (Asteraceae). Adult females responded to volatile compounds emitted by stems of S. laciniatum in field olfactometer bioassays. Plant volatiles were monoterpenes, including, in descending order of abundance, racemic - and -pinene (~50% + enantiomer for both), (+)-limonene, (–)-camphene, and -myrcene. In laboratory bioassays, females responded to aeration extracts of plant stems, the full blend of synthetic monoterpenes, and the four-component blend of -pinene, -pinene, (+)-limonene, and (–)-camphene. This monoterpene blend apparently serves as an olfactory cue for host plant location for female A. rufus and is the first such cue to be reported for a cynipid gall wasp. Species-specific ratios of plant monoterpenes may provide cues for gall wasp females to distinguish between plant species and choose appropriate hosts for oviposition. The olfactometer and bioassay techniques developed for this research may be useful for field bioassays of other types of minute arthropods. 相似文献
475.
Fox A Harley W Feigley C Salzberg D Sebastian A Larsson L 《Journal of environmental monitoring : JEM》2003,5(2):246-252
Our group previously demonstrated that carbon dioxide (CO2) levels in heavily occupied schools correlate with the levels of airborne bacterial markers. Since CO2 is derived from the room occupants, it was hypothesized that in schools, bacterial markers may be primarily increased in indoor air because of the presence of children; directly from skin microflora or indirectly, by stirring up dust from carpets and other sources. The purpose of this project was to test the hypothesis. Muramic acid (Mur) is found in almost all bacteria whereas 3-hydroxy fatty acids (3-OH FAs) are found only in Gram-negative bacteria. Thus Mur and 3-OH FA serve as markers to assess bacterial levels in indoor air (pmol m(-3)). In our previous school studies, airborne dust was collected only from occupied rooms. However, in the present study, additional dust samples were collected from the same rooms each weekend when unoccupied. Samples were also collected from outside air. The levels of dust, Mur and C10:0, C12:0, C14:0, and C16:0 3-OH FAs were each much higher (range 5-50 fold) in occupied rooms than in unoccupied school rooms. Levels in outdoor air were much lower than that of indoor air from occupied classrooms and higher than the levels in the same rooms when unoccupied. The mean CO2 concentrations were around 420 parts per million (ppm) in unoccupied rooms and outside air; and they ranged from 1017 to 1736 ppm in occupied rooms, regularly exceeding 800-1000 ppm, which are the maximum levels indicative of adequate indoor ventilation. This indicates that the children were responsible for the increased levels of bacterial markers. However, the concentration of Mur in dust was also 6 fold higher in occupied rooms (115.5 versus 18.2 pmole mg(-1)). This further suggests that airborne dust present in occupied and unoccupied rooms is quite distinct. In conclusion in unoccupied rooms, the dust was of environmental origin but the children were the primary source in occupied rooms. 相似文献
476.
A. Mansingh D. E. Robinson C. Henry V. Lawrence 《Environmental monitoring and assessment》2000,63(3):459-480
Only organochlorine (OC) residues were monitored by gas chromatographyin water, sediment and shrimp samples collected everymonth between July 1982 and August 1983 from therivers of Rio Cobre basin. In samples collected everyfour months during 1989–1990, and seven times duringJuly 1995–March 1996, OC and OP (organophosphates)residues were monitored. Carbamate and pyrethroidresidues were not monitored. The detection ofresidues in 1982–1983 was 54 to 100% in water andsediment, and 83 to 100% in shrimp samples fromvarious sampling stations in the four rivers. In otheryears, it ranged from about 40 to 100% in the threetypes of samples.In 1982–1983, DDE and dieldrin residues were found tobe much higher than those of lindane and - and-endosulfan in Black River, Rio Pedro, ThomasRiver and Rio Cobre in the watershed. The ranges ofmeans of each residue in water (g L-1), sediment(ng g-1) and shrimp (ng g-1) samples, respectively, were:DDE, 0.059–102.0, 3.44–13.97, 0.344–14.57;dieldrin, 0.026–173.6, 1.21–2.75, 0.427–5.59;-endosulfan, bdl, 1.75–4.00, bdl;-endosulfan, bdl (below detectable limits), 2.51–9.48, bdl;and lindane, (bdl), 0.110–0.319, 2.90.In 1989–1990 and 1995–1996, residues of six OCs and two OPs were detected quite regularly. DDE, dieldrinand Chlorpyrifos residues were much higher than thoseof the other insecticides. The range of their meansin water (g L-1), sediment and shrimp (ng g-1),respectively, were: DDE, 1.66–19.76, 0.941–5.84,1.11–8.32; dieldrin, 0.077–7.22, 0.425–3.31,0.385–1.59; -endosulfan, 0.034–1.25, 0.021–1.22, 0.032–3.62; -endosulfan, 0.665–1.23,0.008–3.60, 0.005–3.97; endosulfan sulphate, 0.959–1.34, 0.035–3.08, 0.012–1.80; lindane, bdl,0.005–0.82, 1.19–1.56; chlorpyrifos, 0.702–4.06,0.005–1.51, 0.156–7.04; and diazinon, bdl, 0–0.150, 0.001–0.006. At the mouth of the river, whereit discharges into the sea, the levels of almost allthe residues were higher than upstream. 相似文献
477.
A strategic framework to eco-regionalize Ontario 总被引:1,自引:0,他引:1
478.
479.
Hwan-Man Park Amar K. Mohanty Lawrence T. Drzal Ellen Lee Deborah F. Mielewski Manjusri Misra 《Journal of Polymers and the Environment》2006,14(1):27-35
Injection molded nanocomposites have been successfully fabricated from cellulose acetate (CA), eco-friendly triethyl citrate
(TEC) plasticizer, and organically modified clay with and without maleic anhydride grafted cellulose acetate butyrate (CAB-g-MA)
as a compatibilizer. The effects of processing conditions such as mixing methods, pre-plasticizing times, extruder retention
times (RT) and addition of compatibilizer on the performance of these nanocomposites have been evaluated. The cellulosic plastic
with CA/TEC (80/20 wt%) was used as the polymer matrix for nanocomposite fabrication. The morphologies of these nanocomposites
were evaluated through X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies. The mechanical properties
of the nanocomposites were measured and have been correlated with the XRD and TEM observations. From all of the sequential
mixing methods used, powder–powder mixing leads to the most transparent nanocomposites. Cellulosic plastic-based nanocomposites
obtained using increased pre-plasticizing times and RT showed better exfoliated structures. In the system containing compatibilizer,
the minimum retention time required for obtaining almost completely exfoliated hybrid nanocomposites was shorter than in the
system without compatibilizer. 相似文献
480.