全文获取类型
收费全文 | 4619篇 |
免费 | 407篇 |
国内免费 | 1328篇 |
专业分类
安全科学 | 351篇 |
废物处理 | 39篇 |
环保管理 | 505篇 |
综合类 | 3276篇 |
基础理论 | 595篇 |
环境理论 | 1篇 |
污染及防治 | 373篇 |
评价与监测 | 394篇 |
社会与环境 | 572篇 |
灾害及防治 | 248篇 |
出版年
2024年 | 27篇 |
2023年 | 103篇 |
2022年 | 179篇 |
2021年 | 196篇 |
2020年 | 173篇 |
2019年 | 164篇 |
2018年 | 158篇 |
2017年 | 214篇 |
2016年 | 257篇 |
2015年 | 268篇 |
2014年 | 267篇 |
2013年 | 383篇 |
2012年 | 402篇 |
2011年 | 428篇 |
2010年 | 319篇 |
2009年 | 272篇 |
2008年 | 187篇 |
2007年 | 292篇 |
2006年 | 291篇 |
2005年 | 241篇 |
2004年 | 188篇 |
2003年 | 217篇 |
2002年 | 170篇 |
2001年 | 147篇 |
2000年 | 128篇 |
1999年 | 132篇 |
1998年 | 107篇 |
1997年 | 88篇 |
1996年 | 59篇 |
1995年 | 55篇 |
1994年 | 44篇 |
1993年 | 38篇 |
1992年 | 46篇 |
1991年 | 22篇 |
1990年 | 13篇 |
1989年 | 11篇 |
1988年 | 14篇 |
1987年 | 6篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1977年 | 4篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1971年 | 1篇 |
排序方式: 共有6354条查询结果,搜索用时 10 毫秒
831.
Peter D. Dijkstra Renske Hekman Rüdiger W. Schulz Ton G. G. Groothuis 《Behavioral ecology and sociobiology》2007,61(4):599-609
The nature of the costs maintaining honesty of sexual signalling in inter- and intrasexual interactions remains a contentious
issue. For carotenoid-based colour ornaments, it has been hypothesized that the honesty of the signal is enforced when carotenoid
allocation to colour expression is traded off against carotenoid availability for immunocompetence. In addition, honesty is
enforced if androgens required for colour expression are immunosuppressive. We tested whether there is a trade-off between
colour expression and immunocompetence in a lek-breeding haplochromine cichlid fish, Pundamilia nyererei, from Lake Victoria with a carotenoid-based nuptial dress. First, we showed that expression of red nuptial colouration and
social rank in a group were positively correlated. We then successfully manipulated the level of colour advertisement by socially
stimulating individually housed males with a rival male: Stimulated males developed larger areas of red nuptial colouration
and had higher levels of circulating 11-ketotestosterone (11-KT) than non-stimulated males. We subsequently tested the humoral
immune response to a novel antigen (sheep red blood cells). There was no overall significant effect of social stimulation
on antibody production, but in the stimulated males, the degree of red colouration and the antibody response were negatively
correlated. This significant interaction between colour and treatment thus shows that the negative correlation between colouration
and antibody production is dependent on the (manipulated) social environment. This study provides correlational and experimental
evidence for a trade-off between expression of a sexual trait and one component of immune function in fish. We found no evidence
for a direct effect of 11-KT on antibody production, and we discuss alternative mechanisms that could mediate the trade-off. 相似文献
832.
云南籼稻核心种质回交后代苗期耐冷性研究 总被引:2,自引:3,他引:2
早春低温和连续阴雨是导致籼稻烂秧的主要因素之一,筛选耐冷的种质资源,将耐冷性基因导入高产的籼稻品种之中是防止低温冷害最为经济有效的方法。加强籼籼稻杂交后代的苗期耐冷性研究,可为籼稻耐冷性育种提供条件。以235份云南籼稻核心种质和云南主栽籼稻品种滇屯502(Oryzasatica)配制的杂种F5、BC1F4、BC2F3和BC3F2代为材料,在昆明自然条件下,对亲本及其后代进行苗期(三叶)耐冷性研究。结果表明,(1)不同回交世代与杂种与亲本间的苗期耐冷强弱差异较大,总体趋势为回交供体亲本>F5>BC1F4>BC2F3>BC3F2;揭示了随着回交世代的增加,其回交杂种苗期耐冷性减弱,越来越趋于轮回亲本,在耐冷育种上对回交供体亲本及其早世代材料进行选择更易获得苗期强耐冷材料。(2)同一稻作区,回交供体亲本的苗期耐冷强于杂种后代;稻作区划间,回交供体亲本及杂种F5总趋势相近,滇中一季籼稻粳稻区和滇东北高原粳稻区材料耐冷最强,而BC1F4、BC2F3和BC3F23个回交世代存在一定差异。 相似文献
833.
Effects of Climate and Land-Use Change on Species Abundance in a Central European Bird Community 总被引:2,自引:0,他引:2
NICOLE LEMOINE† HANS-GÜNTHER BAUER‡§ MARKUS PEINTINGER KATRIN BÖHNING-GAESE†‡‡ 《Conservation biology》2007,21(2):495-503
Abstract: Although it is known that changes in land use and climate have an impact on ecological communities, it is unclear which of these factors is currently most important. We sought to determine the influence of land-use and climate alteration on changes in the abundance of Central European birds. We examined the impact of these factors by contrasting abundance changes of birds of different breeding habitat, latitudinal distribution, and migratory behavior. We examined data from the semiquantitative Breeding Bird Atlas of Lake Constance, which borders Germany, Switzerland, and Austria. Changes in the regional abundance of the 159 coexisting bird species from 1980–1981 to 2000–2002 were influenced by all three factors. Farmland birds, species with northerly ranges, and long-distance migrants declined, and wetland birds and species with southerly ranges increased in abundance. A separate analysis of the two decades between 1980–1981 and 1990–1992 and between 1990–1992 and 2000–2002 showed that the impact of climate change increased significantly over time. Latitudinal distribution was not significant in the first decade and became the most significant predictor of abundance changes in the second decade. Although the spatial scale and temporal resolution of our study is limited, this is the first study that suggests that climate change has overtaken land-use modification in determining population trends of Central European birds. 相似文献
834.
根据浙江省丽水市 1 986— 2 0 0 2年酸雨监测数据 ,对该市酸雨污染的现状特征及成因进行了分析。结果表明 ,丽水市酸雨污染严重 ,并呈逐年加重的趋势。冬、春季酸雨率高 ,降水 pH值低 ;降水的主要离子SO42 -与NO-3比值逐年下降 ,说明大气污染有从煤烟型转为煤烟型与机动车尾气混合型的趋势 ;煤耗量、地型地貌特点、低空逆温层频率、地面弱风频率对酸雨率和降水 pH值有明显的影响。 相似文献
835.
煤矿自燃火灾治理关键技术的研究与应用 总被引:10,自引:2,他引:8
介绍了使用同位素测氡法探测煤矿自燃火源位置的原理及应用效果。实践证明,该方法是解决煤矿自燃火灾治理难题的关键技术,由于投资少,精度高,软件处理直观可靠,它有重要推广价值 相似文献
836.
溜管噪声产生的原因是物料颗粒与溜管壁及物料颗粒之间相互撞击的结果,提出了降低噪声的简单措施,在溜管中安装缓冲箱和降速板可取得较好的降噪效果。 相似文献
837.
系统介绍用计算机辅助确定矿井外因火灾位置方法的原理,给出该方法的具体步骤,剖析其定性分析、定量分析和定量分析结果评价三大步骤中的各技术关键,并借助一个实例验证了该方法实用的可行性 相似文献
838.
Simulation of sludge-dredging effects in controlling nutrient release of Lake Kasumigaura with large-size core samples 总被引:2,自引:0,他引:2
Simulationofsludge-dredgingeffectsincontrollingnutrientreleaseofLakeKasumigaurawithlarge-sizecoresamples¥FanChengxin(NanjingI... 相似文献
839.
840.
V. Cacheux G. Tachdjian L. Druart J. F. Oury S. Sérero P. Blot C. Nessmann 《黑龙江环境通报》1994,14(2):79-86
The major aneuploidies diagnosed prenatally involve the autosomes 13, 18, and 21, and sex chromosomes. Fluorescence in situ hybridization (FISH) allows rapid analysis of chromosome copy number in interphase cells. This prospective study evaluated the use of four commercially available centromeric DNA probes (DXZ1, DYZ1, D18Z1, and D13Z1/D21Z1) for direct analysis of uncultured amniocytes. One hundred and sixteen amniotic fluid samples were analysed by FISH and standard cytogenetics. This evaluation demonstrated that FISH with, X, Y, and 18 alpha satellite DNA probes could accurately and rapidly detect aneuploidies involving these chromosomes and could be used in any prenatal clinical laboratory. In contrast, the 13/21 alpha satellite DNA probe hybridizing both chromosomes 13 and 21 was unreliable for prenatal diagnosis in uncultured amniocytes. 相似文献