全文获取类型
收费全文 | 363篇 |
免费 | 19篇 |
国内免费 | 3篇 |
专业分类
安全科学 | 13篇 |
废物处理 | 5篇 |
环保管理 | 71篇 |
综合类 | 56篇 |
基础理论 | 103篇 |
污染及防治 | 88篇 |
评价与监测 | 32篇 |
社会与环境 | 15篇 |
灾害及防治 | 2篇 |
出版年
2023年 | 8篇 |
2022年 | 7篇 |
2021年 | 4篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 10篇 |
2016年 | 18篇 |
2015年 | 12篇 |
2014年 | 6篇 |
2013年 | 30篇 |
2012年 | 12篇 |
2011年 | 22篇 |
2010年 | 17篇 |
2009年 | 14篇 |
2008年 | 19篇 |
2007年 | 27篇 |
2006年 | 24篇 |
2005年 | 7篇 |
2004年 | 15篇 |
2003年 | 13篇 |
2002年 | 10篇 |
2001年 | 4篇 |
2000年 | 7篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1984年 | 4篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1970年 | 1篇 |
1966年 | 1篇 |
1954年 | 1篇 |
1953年 | 1篇 |
1935年 | 1篇 |
排序方式: 共有385条查询结果,搜索用时 859 毫秒
71.
Forest Certification: stakeholders, constraints and effects 总被引:1,自引:0,他引:1
72.
Postfire stand structure in a semiarid savanna: cross-scale challenges estimating biomass. 总被引:1,自引:0,他引:1
Cho-Ying Huang Stuart E Marsh Mitchel P McClaran Steven R Archer 《Ecological applications》2007,17(7):1899-1910
Algorithms relating remotely sensed woody cover to biomass are often the basis for large-scale inventories of aboveground carbon stocks. However, these algorithms are commonly applied in a generic fashion without consideration of disturbances that might alter vegetation structure. We compared field and remote sensing estimates of woody biomass on savannas with contrasting disturbance (fire) histories and assessed potential errors in estimating woody biomass from cover without considering fire history. Field surveys quantified multilayer cover (MLC) of woody and succulent plants on sites experiencing wildfire in 1989 or 1994 and on nearby unburned (control) sites. Remote sensing estimates of the woody cover fraction (WCF) on burned and control sites were derived from contemporary (2005) dry-season Landsat Thematic Mapper imagery (during a period when herbaceous cover was senescent) using a probabilistic spectral mixture analysis model. Satellite WCF estimates were compared to field MLC assessments and related to aboveground biomass using allometry. Field-based MLC and remotely sensed WCFs both indicated that woody cover was comparable on control areas and areas burned 11-16 years ago. However, biomass was approximately twofold higher on control sites. Canopy cover was a strong predictor of woody biomass on burned and control areas, but fire history significantly altered the linear cover-biomass relationship on control plots to a curvilinear relationship on burned plots. Results suggest predictions of woody biomass from "generic" two-dimensional (2-D) cover algorithms may underestimate biomass in undisturbed stands and overestimate biomass in stands recovering from disturbance. Improving the accuracy of woody-biomass estimates from field and/or remotely sensed cover may therefore require disturbance-specific models or detection of vegetation height and transforming 2-D vegetation cover to 3-D vegetation volume. 相似文献
73.
Harrad S Robson M Hazrati S Baxter-Plant VS Deplanche K Redwood MD Macaskie LE 《Journal of environmental monitoring : JEM》2007,9(4):314-318
The environmentally prevalent polybrominated diphenyl ether (PBDE) #47 and polychlorinated biphenyls (PCBs) #28 and #118 were challenged for 24 hours with a novel biomass-supported Pd catalyst (Bio-Pd(0)). Analysis of the products via GC-MS revealed the Bio-Pd(0) to cause the challenged compounds to undergo stepwise dehalogenation with preferential loss of the least sterically hindered halogen atom. A mass balance for PCB #28 showed that it is degraded to three dichlorobiphenyls (33.9%), two monochlorobiphenyls (12%), and biphenyl (30.7%). The remaining mass was starting material. In contrast, while PCB #118 underwent degradation to yield five tetra- and five trichlorinated biphenyls, no less chlorinated products or biphenyl were detected, and the total mass of degraded products was 0.3%. Although the Bio-Pd(0) material was developed for treatment of PCBs, a mass balance for PBDE #47 showed that the biocatalyst could prove a potentially useful method for treatment of PBDEs. Specifically, 10% of PBDE #47 was converted to identifiable lower brominated congeners, predominantly the tribrominated PBDE #17 and the dibrominated PBDE #4, 75% remained intact, while 15% of the starting mass was unaccounted for. 相似文献
74.
Occurrence of alternative flame retardants in indoor dust from New Zealand: indoor sources and human exposure assessment 总被引:4,自引:0,他引:4
Ali N Dirtu AC Van den Eede N Goosey E Harrad S Neels H 't Mannetje A Coakley J Douwes J Covaci A 《Chemosphere》2012,88(11):1276-1282
Due to worldwide restrictions on polybrominated diphenyl ethers (PBDEs), the demand for alternative flame retardants (AFRs), such as organophosphate flame retardants (OPFRs), novel brominated FRs (NBFRs) and hexabromocyclododecanes (HBCDs), has recently increased. Little is known about human exposure to NBFRs and OPFRs and that their levels in dust have been scarcely evaluated worldwide. To increase the knowledge regarding these chemicals, we measured concentrations of five major NBFRs, ten OPFRs and three HBCD isomers in indoor dust from New Zealand homes. Dust samples were taken from living room floors (n=34) and from mattresses of the same houses (n=16). Concentrations (ngg(-1)) of NBFRs were: 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) (<2-175), decabromodiphenyl ethane (DBDPE) (<5-1430), 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (TBB) (<2-2285) and bis(2-ethylhexyl)-3,4,5,6-tetrabromophthalate (TBPH) (<2-640). For OPFRs, concentrations (ngg(-1)) ranged between: tri-ethyl-phosphate (TEP) (<10-235), tri-n-butyl-phosphate (TnBP) (<20-7545), tris-(2-chloroethyl)-phosphate (TCEP) (<20-7605), tris-(1-chloro-2-propyl) phosphate (TCPP) (20-7615), tri-(2-butoxyethyl)-phosphate (TBEP) (50-27325), tris-(2,3-dichloropropyl)-phosphate (TDCPP) (20-16560), tri-phenyl-phosphate (TPhP) (20-35190), and tri-cresyl-phosphate (TCP) (<50-3760). HBCD concentrations fell in the range <2-4100ngg(-1). BTBPE, DBDPE, TBPH, TBEP, and TnBP showed significant positive correlation (p<0.05) between their concentrations in mattresses and the corresponding floor dust (n=16). These data were used to derive a range of plausible exposure scenarios. Although the estimated exposure is well below the corresponding reference doses (RfDs), caution is needed given the likely future increase in use of these FRs and the currently unknown contribution to human exposure by other pathways such as inhalation and diet. 相似文献
75.
Metaphase chromosomes and interphase nuclei from nine amniotic fluid cultures were studied with fluorescence in situ hybridization (FISH). The samples were initially analyzed with routine G-banding and were diagnosed as having true mosaicism (five patients) or pseudomosaicism (four patients). In our study, FISH analysis could provide additional information to distinguish pseudo– from true mosaicism by allowing interphase studies and analysis of an increased number of metaphase spreads. These results suggest a multilinear origin of ‘in situ’ colonies of cells. 相似文献
76.
Robin J. Stuart 《Behavioral ecology and sociobiology》1992,30(6):403-408
Summary In social insects, there is often a brief period following eclosion when workers are highly acceptable in alien nests of their own or other species. This study tested for such an acceptance period in the facultatively polygynous ant, Leptothorax curvispinosus, and compared the duration and effectiveness of this period for conspecific and heterospecific introductions. Workers that eclosed and aged for 1–70 h or 30 days in isolation were introduced into either their parental nests (n=24), alien conspecific nests (n=265), or nests of the closely related and biologically similar species, L. longispinosus (n=341). In alien conspecific nests, acceptance was maximal for workers aged 1–12 h at introduction (67.7% not attacked, 75.8% adopted) and gradually decreased until the level of nonaggression (after 60 h) and adoption (after 36 h) were not significantly different from 30-day-old workers (5.9% not attacked, 17.6% adopted). In heterospecific nests, acceptance was maximal for workers aged 1–4 h at introduction (34.8% not attacked, 37.0% adopted) but thereafter was not significantly different from 30-day-old workers (5.6% not attacked, 8.3% adopted). In their parental nests, workers were generally accepted regardless of age (4–56 h posteclosion, 95.8% not attacked, 100% adopted); a result that is consistent with previous research on older workers (38–157 days posteclosion). This study demonstrates an acceptance period that is more effective and of longer duration within than between these species but that, under uniform laboratory conditions, is often not necessary for the integration of workers into their parental colonies. Within colonies, acceptance periods might only be important during relatively brief periods in a colony's life history when eclosing workers produce genetically based nestmate recongition cues that are not already represented in the colony and must be learned by colony members (e.g., during early colony growth or following adoption of queens), or when young workers must acquire environmentally based nestmate recognition cues to achieve and maintain acceptability. 相似文献
77.
Stuart Mcminn 《The Environmentalist》1997,17(2):135-141
The paradigm of sustainable tourism is discussed in terms of analysing what it actually means. Certain questions are raised and these include the means of its measurement, the question of intergenerational impacts and how these may be assessed, the determination of what exactly is meant by environment, the aspect of tourism as an industry and, with specific reference to tourism in the developing world, the potential for neocolonialism. It is argued that, although sustainable tourism may be a worthwhile goal, inherent problems in the definition and measurement of its success make it an elusive if not academic target. The challenge of sustainable tourism is to see it in a broader context as but one tool of development and to ensure that it is examined in the context of the local community as well as a global perspective. 相似文献
78.
Real-time examination of the fetal heart in 350 pregnancies has allowed a composite picture of normal fetal cardiac anatomy to be established and echocardiographic interpretation has been confirmed by anatomical studies. Two echocardiographic sections are readily obtainable and are suggested as applicable to routine scanning but the specialist nature of interpreting abnormalities is stressed. Six abnormalities have been suspected during the study and five confirmed anatomically or at cardiac catheterization. In view of the low incidence of congenital heart disease in a normal obstetric population, high risk groups should perhaps be selected for cardiac scanning at the present time. These include mothers of previously affected babies, diabetic mothers and certain abnormalities of pregnancy. Fetal ascites is particularly important, being present in three of the four proven cases of cardiac abnormality. 相似文献
79.
Eric Jauniaux Sanjay Vyas Caroline Finlayson Gonzalo Moscoso Marie Driver Stuart Campbell 《黑龙江环境通报》1990,10(2):127-132
Ultrasonographic features of a fetus at 18 weeks of gestation suggesting a body stalk anomaly are presented. These included a large abdominal anterior wall defect in apparent continuity with the placenta, severe kyphoscoliosis of the lower spine, the absence of one kidney, and a very short umbilical cord with only one umbilical artery. The amniotic fluid was reduced and the fetus was almost immobile at short-interval ultrasound examinations. The pregnancy was terminated and autopsy of the fetus showed abnormalities compatible with maldevelopment of both cephalic and caudal embryonic folds. 相似文献
80.
The prenatal diagnosis of micrognathia is usually based on a subjective impression of the size of the jaw when examining the fetal profile. We have constructed a centile chart for mandibular length between 12 and 27 post-menstrual weeks in a cross-sectional study of 184 fetuses. The application of this chart in clinical practice may permit a more objective diagnosis of micrognathia in the prenatal period. 相似文献