全文获取类型
收费全文 | 16397篇 |
免费 | 172篇 |
国内免费 | 137篇 |
专业分类
安全科学 | 449篇 |
废物处理 | 630篇 |
环保管理 | 2287篇 |
综合类 | 2569篇 |
基础理论 | 4468篇 |
环境理论 | 4篇 |
污染及防治 | 4334篇 |
评价与监测 | 1009篇 |
社会与环境 | 853篇 |
灾害及防治 | 103篇 |
出版年
2022年 | 113篇 |
2021年 | 130篇 |
2020年 | 105篇 |
2019年 | 148篇 |
2018年 | 226篇 |
2017年 | 225篇 |
2016年 | 358篇 |
2015年 | 240篇 |
2014年 | 358篇 |
2013年 | 1289篇 |
2012年 | 446篇 |
2011年 | 636篇 |
2010年 | 537篇 |
2009年 | 519篇 |
2008年 | 690篇 |
2007年 | 691篇 |
2006年 | 661篇 |
2005年 | 508篇 |
2004年 | 588篇 |
2003年 | 521篇 |
2002年 | 482篇 |
2001年 | 702篇 |
2000年 | 471篇 |
1999年 | 282篇 |
1998年 | 241篇 |
1997年 | 217篇 |
1996年 | 227篇 |
1995年 | 247篇 |
1994年 | 272篇 |
1993年 | 219篇 |
1992年 | 247篇 |
1991年 | 222篇 |
1990年 | 254篇 |
1989年 | 238篇 |
1988年 | 193篇 |
1987年 | 173篇 |
1986年 | 159篇 |
1985年 | 167篇 |
1984年 | 192篇 |
1983年 | 180篇 |
1982年 | 185篇 |
1981年 | 179篇 |
1980年 | 137篇 |
1979年 | 153篇 |
1978年 | 131篇 |
1977年 | 117篇 |
1975年 | 118篇 |
1974年 | 115篇 |
1973年 | 110篇 |
1972年 | 133篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
491.
492.
493.
494.
Numerous studies have focussed on the relationship between female choice and the multiple exaggerated sexual traits of males.
However, little is known about the ability of males to actively enhance specific components of their display in response to
the loss of one component. We investigated the capacity of male satin bowerbirds (Ptilonorhynchus violaceus) to respond to the loss of one of their sexual signals by performing an experiment in which we removed decorations at their
bowers. We found that males compensated for decoration loss by increasing bower construction behaviour and decreasing their
latency to bower painting. These results are novel because they suggest that males can assess the quality of their own display
and make decisions about how to augment their displays. We discuss these results in the context of previous studies of mate
choice in satin bowerbirds, as both of the supplementary behaviours we observed are known correlates of male mating success. 相似文献
495.
Mikołaj Urbanowski Paweł Socha Paweł Dąbrowski Wioletta Nowaczewska Anna Sadakierska-Chudy Tadeusz Dobosz Krzysztof Stefaniak Adam Nadachowski 《Die Naturwissenschaften》2010,97(4):411-415
An upper second permanent molar from a human was found alongside numerous tools of the Micoquian tradition and was excavated
in Stajnia Cave, which is located over 100 km North of the Carpathian Mountains in southern Poland. The age of these finds
has been established within a time-span of late Saalian to early Weichselian, most likely to OIS 5c or 5a, according to the
palaeontological, geological, archaeological and absolute dating of the layer from which they were obtained. An examination
of the morphology of the human molar indicates that this tooth exhibits many traits frequently occurring in Neanderthal upper
molars. Although the occurrence of derived Neanderthal traits in the Stajnia molar cannot be firmly established because of
degradation of its cusps, the presence of the above-mentioned features allows the assertion that this tooth belonged to a
Neanderthal. The age of the Stajnia tooth and the archaeological context of this find also indicate that this molar is of
Neanderthal origin. 相似文献
496.
497.
498.
Christopher D. Pull William O. H. Hughes Mark J. F. Brown 《Die Naturwissenschaften》2013,100(12):1125-1136
Pathogens exert a strong selection pressure on organisms to evolve effective immune defences. In addition to individual immunity, social organisms can act cooperatively to produce collective defences. In many ant species, queens have the option to found a colony alone or in groups with other, often unrelated, conspecifics. These associations are transient, usually lasting only as long as each queen benefits from the presence of others. In fact, once the first workers emerge, queens fight to the death for dominance. One potential advantage of co-founding may be that queens benefit from collective disease defences, such as mutual grooming, that act against common soil pathogens. We test this hypothesis by exposing single and co-founding queens to a fungal parasite, in order to assess whether queens in co-founding associations have improved survival. Surprisingly, co-foundresses exposed to the entomopathogenic fungus Metarhizium did not engage in cooperative disease defences, and consequently, we find no direct benefit of multiple queens on survival. However, an indirect benefit was observed, with parasite-exposed queens producing more brood when they co-founded, than when they were alone. We suggest this is due to a trade-off between reproduction and immunity. Additionally, we report an extraordinary ability of the queens to tolerate an infection for long periods after parasite exposure. Our study suggests that there are no social immunity benefits for co-founding ant queens, but that in parasite-rich environments, the presence of additional queens may nevertheless improve the chances of colony founding success. 相似文献
499.
Stuart W. Krasner Ai Ji Chih-Fen T. Lee Raha Shirkhani Joshua M. Allen Susan D. Richardson Michael J. Plewa 《环境科学学报(英文版)》2022,34(7):161-172
A survey was conducted at eight U.S. drinking water plants, that spanned a wide range of water qualities and treatment/disinfection practices. Plants that treated heavily-wastewater-impacted source waters had lower trihalomethane to dihaloacetonitrile ratios due to the presence of more organic nitrogen and HAN precursors. As the bromide to total organic carbon ratio increased, there was more bromine incorporation into DBPs. This has been shown in other studies for THMs and selected emerging DBPs (HANs), whereas this study examined bromine incorporation for a wider group of emerging DBPs (haloacetaldehydes, halonitromethanes). Moreover, bromine incorporation into the emerging DBPs was, in general, similar to that of the THMs. Epidemiology studies that show an association between adverse health effects and brominated THMs may be due to the formation of brominated emerging DBPs of heath concern. Plants with higher free chlorine contact times before ammonia addition to form chloramines had less iodinated DBP formation in chloraminated distribution systems, where there was more oxidation of the iodide to iodate (a sink for the iodide) by the chlorine. This has been shown in many bench-scale studies (primarily for iodinated THMs), but seldom in full-scale studies (where this study also showed the impact on total organic iodine. Collectively, the THMs, haloacetic acids, and emerging DBPs accounted for a significant portion of the TOCl, TOBr, and TOI; however, ∼50% of the TOCl and TOBr is still unknown. The correlation of the sum of detected DBPs with the TOCl and TOBr suggests that they can be used as reliable surrogates. 相似文献
500.
基于对风险全过程控制的思想,利用层次分析法,构建了综合考虑危险废物填埋场自身属性、污染场地水文地质条件以及污染受体等因素的危险废物填埋场地下水污染风险分级指标体系,该体系共包括14项指标;并采用MCDA(multi-criteria decision analysis,多准则决策分析)模型,对我国37个危险废物填埋场(不包括港澳台数据,下同)地下水污染风险进行了分级研究. 结果表明:14项风险分级指标之间具有很好的独立性,指标体系能够较为完整、准确地反映危险废物填埋场对地下水的污染风险程度;37个危险废物填埋场地下水污染风险可分为高、中、低3个级别,其中81%处于中、低级风险级别;地下水中特征污染物ρ(Cr)监测值与风险分级分值的距平指数为0.802 9,验证了风险分级结果的可靠性;同时采用MDCA模型对风险分级指标权重的敏感性进行分析,验证了风险分级过程中指标权重赋值的准确性,并降低了指标权重赋值过程中的不确定性,进一步提高了分级结果的可靠性.风险分级结果在一定程度上可为危险废物填埋场地下水污染风险管理提供依据. 相似文献