全文获取类型
收费全文 | 92篇 |
免费 | 3篇 |
国内免费 | 1篇 |
专业分类
安全科学 | 2篇 |
废物处理 | 4篇 |
环保管理 | 21篇 |
综合类 | 26篇 |
基础理论 | 25篇 |
环境理论 | 1篇 |
污染及防治 | 10篇 |
评价与监测 | 5篇 |
社会与环境 | 2篇 |
出版年
2022年 | 1篇 |
2021年 | 3篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2016年 | 3篇 |
2015年 | 5篇 |
2014年 | 1篇 |
2013年 | 4篇 |
2012年 | 5篇 |
2011年 | 11篇 |
2010年 | 3篇 |
2009年 | 3篇 |
2008年 | 5篇 |
2007年 | 4篇 |
2006年 | 7篇 |
2004年 | 2篇 |
2003年 | 4篇 |
2001年 | 3篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 5篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1989年 | 2篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有96条查询结果,搜索用时 62 毫秒
61.
The paper is concerned with the impact of small business advice agencies on their clients. The work of two agencies (an Enterprise Agency and a local authority Development Unit) operating in the same geographical area (Swale in Kent) is evaluated using a survey of clients as evidence. It is concluded that both agencies are meeting real and distinctive needs among start‐up and established small businesses in the area, and have established effective systems for the delivery of their services. Quality of staff is confirmed as a key factor influencing client satisfaction with the agencies. The impact of the agencies on busines efficiency is ambiguous; it is suggested that major beneficiaries of the work of the agencies are the banks. 相似文献
62.
Patterns of fluctuating asymmetry in beetle horns: an experimental examination of the honest signalling hypothesis 总被引:6,自引:0,他引:6
Recent theoretical arguments have claimed that negative relationships between the size and symmetry of secondary sexual traits
are indicative of honest signalling of male quality. The patterns of fluctuating asymmetry in beetle horns have been proposed
to support the honest signalling hypothesis. Here we examine three assumptions of the hypothesis, (1) that traits are costly
to produce; (2) the levels of fluctuating asymmetry are indicative of stress imposed during development; and (3) that males
with larger traits should have more symmetrical traits, using the horned beetle, Onthophagus taurus. Experimental manipulations of brood mass were used to manipulate horn size and asymmetry. The development of horns was found
to be environmentally determined and costly in terms of delayed development and increased risk of pre-adult mortality. Decreasing
resource availability increased relative horn asymmetry. However, horn height was positively related to absolute horn asymmetry.
While the results do support the hypothesis that sexual selection on secondary sexual traits should increase levels of fluctuating
asymmetry, they provide no support for the notion that the patterns of asymmetry honestly signal male quality. Horns are used
in disputes between males and may be indicative of male parental investment. Thus, we conclude that while horn size may be
an indication of male quality, the patterns of fluctuating asymmetry are not.
Received: 16 December 1996 / Accepted after revision: 5 May 1997 相似文献
63.
Calling characteristics of parasitized and unparasitized populations of the field cricket Teleogryllus oceanicus 总被引:4,自引:0,他引:4
Summary Examination of three populations of the field cricket Teleogryllus oceanicus revealed the presence of an acoustically-orienting parasitoid fly, Ormia ochracea (Tachinidae), in the population of crickets that has been introduced to the Hawaiian Islands. The cricket is native to Australia and the Pacific, and the fly is native to North America but has also been introduced to Hawaii. Up to 27% of males and 7% of females in Hawaii were infested with fly larvae. Song structure in the parasitized Hawaiian population was distinct from that of the other two groups, with the Hawaiian crickets showing several reduced song parameters. In addition, onset and cessation of calling at dusk and dawn were more abrupt in the Hawaiian population. These results are consistent with selective pressure from the phonotactic flies to decrease risky calling. Silent males were present in all three populations, suggesting that these noncallers may not represent a unique adaptation to the parasitoid.
Correspondence to: M. Zuk 相似文献
64.
George M. Leigh William S. Hearn Kenneth H. Pollock 《Environmental and Ecological Statistics》2006,13(1):89-108
Instantaneous natural mortality rates and a nonparametric hunting mortality function are estimated from a multiple-year tagging
experiment with arbitrary, time-dependent fishing or hunting mortality. Our theory allows animals to be tagged over a range
of times in each year, and to take time to mix into the population. Animals are recovered by hunting or fishing, and death
events from natural causes occur but are not observed. We combine a long-standing approach based on yearly totals, described
by Brownie et al. (1985, Statistical Inference from Band Recovery Data: A Handbook, Second edition, United States Fish and Wildlife Service, Washington, Resource Publication, 156), with an exact-time-of-recovery
approach originated by Hearn, Sandland and Hampton (1987, Journal du Conseil International pour l’Exploration de la Mer, 43, 107–117), who modeled times at liberty without regard to time of tagging. Our model allows for exact times of release
and recovery, incomplete reporting of recoveries, and potential tag shedding. We apply our methods to data on the heavily
exploited southern bluefin tuna (Thunnus maccoyii). 相似文献
65.
In our previous work we have isolated fetal cells from maternal blood and used fluorescent in situ hybridization (FISH) for chromosome-specific probes to detect aneuploidy. Current efforts in the Baylor College of Medicine programme are focusing on obtaining consistency in flow-sorting methodology and on determining sensitivity and specificity. To this end, systematic evaluation of five glycophorin A (gly A) antibodies all produced agglutination, leading us to abandon the use of gly A antibodies for positive selection of fetal cells. Conversely, we have found LDS-751 to be useful for nuclear selection. CD45 negative selection can best be accomplished by the use of flasks coated with goat antibodies against mouse antibodies. Positive selection by flow sorting for either CD71+ cells or gamma-globin-positive cells seems to be successful. Using these two approaches, we have recently detected male (fetal) cells in pregnancies in which the fetus was 46, XY in 10 of 18 and in 12 of 14 cases, respectively. 相似文献
66.
Lee P. Shulman MD Nabil A. Raafat Phyllis C. Mace Donald S. Emerson Richard E. Felker Joe Leigh Simpson Sherman Elias 《黑龙江环境通报》1994,14(3):223-226
Recent reports have indicated an increased risk for fetal chromosome abnormalities, especially autosomal trisomy, in fetuses with isolated cystic hygroma, or prominent nuchal membranes, detected by ultrasonography during the first trimester. However, these reports present contradictory information regarding the prognostic significance of septations within the cystic hygroma. We evaluated, in blind fashion, 55 consecutive cases of isolatd fetal cystic hygroma detected at or before 13·9 weeks' gestation to determine the association between septations and fetal chromosome complement. Septations were associated (P<0·05) with an increased risk for fetal chromosome abnormalities. However, the incidence of chromosome abnormalities was also increased (12·5 per cent) among cases not characterized by septations. Thus, we believe it prudent to offer invasive prenatal testing to all women found to be carrying fetuses with cystic hygroma, irrespective of the presence or absence of septations. 相似文献
67.
Fetal cells unequivocally exist in and can be isolated from maternal blood. Erythroblasts, trophoblasts, granulocytes and lymphocytes have all been isolated by various density gradient and flow sorting techniques. Chromosomal abnormalities detected on isolated fetal cells include trisomy 21, trisomy 18, Klinefelter syndrome (47,XXY) and 47,XYY. Polymerase chain reaction (PCR) technology has enabled the detection of fetal sex, Mendelian disorders (e.g. β-globin mutations), HLA polymorphisms, and fetal Rhesus (D) blood type. The fetal cell type that has generated the most success is the nucleated erythrocyte; however, trophoblasts, lymphocytes and granulocytes are also considered to be present in maternal blood. Fetal cells circulate in maternal blood during the first and second trimesters, and their detection is probably not affected by Rh or ABO maternal-fetal incompatibilities. Emphasis is now directed toward determining the most practical and efficacious manner for this technique to be applied to prenatal genetic diagnosis. Only upon completion of clinical evaluations could it be considered appropriate to offer this technology as an alternative to conventional invasive and non-invasive methods of prenatal cytogenetic diagnosis. 相似文献
68.
Dr. Avirachan T. Tharapel Sherman Elias Lee P. Shulman Linda Seely Donald S. Emerson Joe Leigh Simpson 《黑龙江环境通报》1989,9(7):467-472
Non-mosaic trisomy 16 was observed in chorionic villus cytotrophoblasts (direct) as well as cultured mesenchymal core cells derived from the pregnancy of a 38-year-old woman. Chromosome preparations from amniotic fluid and neonatal cultures (cord blood) were 46,XX. Normal fetal growth as determined by serial ultrasound examinations occurred throughout the pregnancy, which resulted in a healthy 2724 g female. Multiple biopsies taken from the umbilical cord, placental cotyledons, and fetal membranes were 46,XX. However, a placental nodule and three of six cultures initiated from membranes (amnion and chorion) showed 46,XX/47,XX, + 16 mosaicism. We propose that the trisomy 16 cells arose from residual villi derived from a trisomic cotwin that never developed. This case further demonstrates that normal fetal growth may presage normal outcome irrespective of cytogenetic findings in cytotrophoblasts (direct) and cultured mesenchymal core cells. 相似文献
69.
Lee P. Shulman MD Joe Leigh Simpson Richard E. Felker Donald S. Emerson Carole M. Meyers Owen P. Phillips Sherman Elias 《黑龙江环境通报》1992,12(3):229-234
Transvaginal chorionic villus sampling (CVS) using concurrent transabdominal ultrasound guidance was performed in six women who desired CVS but could not be offered transcervical or transabdominal approaches because of uterine position and placental location. Satisfactory amounts of chorionic villi were obtained in all six cases with no maternal discomfort, an occurrence that contrasts with our experience in transvaginal CVS using endovaginal ultrasound guidance. We believe that transvaginal CVS using concurrent transabdominal ultrasound guidance warrants consideration as an alternative technique for first-trimester CVS in selected patients. 相似文献
70.
On the otherwise low-biomass seafloor of the Gulf of Mexico (GoM) continental slope, natural oil and gas seeps are oases of local primary production that support lush animal communities. Hundreds of seep communities have been documented on the continental slope, and nutrition derived from seeps could be an important link in the overall GoM food web. Here, we present a uniquely large and cohesive data set of δ(13)C, δ(15)N, and δ(34)S compositions of the vestimentiferan tubeworms Escarpia laminata and Lamellibrachia sp. 1, which dominate biomass at GoM seeps and provide habitat for hundreds of other species. Our sampling design encompassed an entire region of the GoM lower slope, allowing us for the first time to assess spatial variability in isotope compositions and to robustly address long-standing hypotheses about how vestimentiferans acquire and cycle nutrients over their long lifespan (200+?years). Tissue δ(13)C values provided strong evidence that larger adult vestimentiferans use their buried roots to take up dissolved inorganic carbon from sediment pore water, while very small individuals use their plume to take up carbon dioxide from the seawater. δ(34)S values were extremely variable among individuals of the same species within one location (<1?m(2) area), indicating high variability in the inorganic sulfur pools on a very small spatial scale. This finding supports the hypothesis that vestimentiferans use their roots to cycle sulfate and sulfide between their symbionts and free-living consortia of sulfate-reducing archaea in the sediment. Finally, consistent differences in δ(15)N between two cooccurring vestimentiferan species provided the first strong evidence for partitioning of inorganic resources, which has significant implications for the ecology and evolution of this taxonomic group. 相似文献