全文获取类型
收费全文 | 4291篇 |
免费 | 70篇 |
国内免费 | 199篇 |
专业分类
安全科学 | 78篇 |
废物处理 | 99篇 |
环保管理 | 554篇 |
综合类 | 1010篇 |
基础理论 | 2012篇 |
污染及防治 | 356篇 |
评价与监测 | 119篇 |
社会与环境 | 222篇 |
灾害及防治 | 110篇 |
出版年
2021年 | 1篇 |
2018年 | 114篇 |
2017年 | 116篇 |
2016年 | 207篇 |
2015年 | 43篇 |
2014年 | 13篇 |
2013年 | 23篇 |
2012年 | 239篇 |
2011年 | 283篇 |
2010年 | 95篇 |
2009年 | 43篇 |
2008年 | 22篇 |
2007年 | 41篇 |
2006年 | 42篇 |
2005年 | 593篇 |
2004年 | 1009篇 |
2003年 | 819篇 |
2002年 | 123篇 |
2001年 | 62篇 |
2000年 | 55篇 |
1999年 | 95篇 |
1998年 | 59篇 |
1997年 | 132篇 |
1996年 | 41篇 |
1995年 | 35篇 |
1994年 | 37篇 |
1993年 | 72篇 |
1992年 | 58篇 |
1991年 | 51篇 |
1990年 | 6篇 |
1989年 | 16篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 7篇 |
1974年 | 1篇 |
1916年 | 1篇 |
排序方式: 共有4560条查询结果,搜索用时 46 毫秒
881.
Influences of organic matters of soil and water on speciation and biological utilization of selenium are discussed. Humic acid is found to be the main pool of selenium in soil and affects the bio-availability of the element in soil-plant system. Fulvic acid from drinking water inhibits the absorption of selenium taken from diet. The relationship between high content of organic matters of water and selenium deficiency on the causes of KBD could be reflected in the limited synthesis of glutathione peroxidase, which is generally stimulated by fulvic acid from drinking water. 相似文献
882.
本文探讨了变分理论在超塑性成形方面的应用,建立了适合超塑性材料的变分理论的基本方程,并比超塑性材料轴对称镦粗为例验证了这些方程的正确性。 相似文献
883.
Ernst Mayr: the doyen of twentieth century evolutionary biology 总被引:1,自引:0,他引:1
Hölldobler B 《Die Naturwissenschaften》2004,91(6):249-254
884.
885.
886.
Al/Si configurations in some natural and synthetic Rb-feldspars have been examined carefully by EMPA and XPS analyses. Our results indicate that a small amount of H2O and excess Si and Al are incorporated in hydrothermally synthesized Rb-feldspar. The quantities of excess Al are 0.056 atoms per formula unit and are negatively correlated with those of the Rb, suggesting the presence of excess Al occupying non-tetrahedral sites in feldspar structures. This leads to incorporation of Al(Al3Si)O8 endmember into Rb-feldspars, estimated as one appropriate endmember indication for unusual chemistry of feldspars. In addition, Si2p, Al2p and O1s XPS signals of Rb-feldspars shift drastically toward the higher energy side than those of any natural feldspars. These provide conclusive evidence not only for existence of perceptible excess Si and Al, but also for Al at both extra-framework and tetrahedral sites in feldspar structures. 相似文献
887.
The mechanism of caste differentiation in a social aphid Tuberaphis styraci, which has a sterile soldier caste in the 2nd instar, was investigated using an artificial diet rearing system. High aphid density induced soldier production. Combinatorial prenatal and postnatal density treatments revealed that (1) either prenatal high density or postnatal high density is sufficient for soldier induction; (2) thus, embryos in the maternal body and newborn 1st instar nymphs are both responsive to high density; (3) the combination of prenatal high density and postnatal high density enhances soldier differentiation in a synergistic manner; and (4) the final determination of soldier differentiation occurs postnatally, probably at a late 1st instar stage. This study first throws light on the developmental aspects of caste differentiation in a social aphid. 相似文献
888.
Food sharing among unrelated same-sex individuals has received considerable interest from primatologists and evolutionary biologists because of its apparent altruistic nature and implications for the evolution of complex social cognition. In contrast to primates, food sharing in birds has received relatively little attention. Here we describe three types of food sharing in jackdaws, with the initiative for the transfer either with the receiver or the giver. The latter situation is of particular interest because the food transfer takes place through active giving. Compared to primates, jackdaws show high rates of food sharing. Finally we discuss the implications of food sharing in jackdaws, and in birds in general. 相似文献
889.
Gao Qing xian Ren Zhen hai Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China. E mail: gaoqx@public.east.cn.net Zhang Yun gang Center of Satellite Meteorology Beijing China Zhang Cheng chang Beijin 《环境科学学报(英文版)》1999,(3)
1 IntroductionOzoneisoneofthetracegasesinatmosphere.Itcanabsorbnearlyallsolarultravioletradiation(UVB)rangedfrom0-20—0-35μm.Thechangeofstratosphericozoneconcentrationanditsverticalstructurewillinfluencethetemperaturestructureofstratosphere.Thedecrea… 相似文献
890.
Social insect colonies respond to challenges set by a variable environment by reallocating work among colony members. In many social insects, such colony-level task allocation strategies are achieved through individual decisions that produce a self-organized adapting group. We investigated colony responses to parasitoids and native ant competitors in the red imported fire ant (Solenopsis invicta). Parasitoid flies affected fire ants by decreasing the proportion of workers engaged in foraging. Competitors also altered colony-level behaviours by reducing the proportion of foraging ants and by increasing the proportion of roaming majors, whose role is colony defence. Interestingly, the presence of both parasitism and competition almost always had similar effects on task allocation in comparison to each of the biotic factors on its own. Thus, our study uniquely demonstrates that the interactive effect of both parasitism and competition is not necessarily additive, implying that these biotic factors alter colony behaviour in distinct ways. More generally, our work demonstrates the importance of studying the dynamics of species interactions in a broader context. 相似文献