全文获取类型
收费全文 | 37094篇 |
免费 | 379篇 |
国内免费 | 262篇 |
专业分类
安全科学 | 990篇 |
废物处理 | 1438篇 |
环保管理 | 4656篇 |
综合类 | 5695篇 |
基础理论 | 10062篇 |
环境理论 | 28篇 |
污染及防治 | 9806篇 |
评价与监测 | 2364篇 |
社会与环境 | 2474篇 |
灾害及防治 | 222篇 |
出版年
2022年 | 307篇 |
2021年 | 370篇 |
2020年 | 225篇 |
2019年 | 311篇 |
2018年 | 601篇 |
2017年 | 607篇 |
2016年 | 836篇 |
2015年 | 639篇 |
2014年 | 1010篇 |
2013年 | 2780篇 |
2012年 | 1230篇 |
2011年 | 1655篇 |
2010年 | 1353篇 |
2009年 | 1326篇 |
2008年 | 1629篇 |
2007年 | 1755篇 |
2006年 | 1507篇 |
2005年 | 1300篇 |
2004年 | 1261篇 |
2003年 | 1172篇 |
2002年 | 1134篇 |
2001年 | 1450篇 |
2000年 | 1034篇 |
1999年 | 629篇 |
1998年 | 481篇 |
1997年 | 490篇 |
1996年 | 489篇 |
1995年 | 542篇 |
1994年 | 487篇 |
1993年 | 441篇 |
1992年 | 454篇 |
1991年 | 415篇 |
1990年 | 428篇 |
1989年 | 446篇 |
1988年 | 376篇 |
1987年 | 333篇 |
1986年 | 316篇 |
1985年 | 341篇 |
1984年 | 328篇 |
1983年 | 345篇 |
1982年 | 362篇 |
1981年 | 304篇 |
1980年 | 281篇 |
1979年 | 307篇 |
1978年 | 251篇 |
1977年 | 220篇 |
1976年 | 220篇 |
1975年 | 213篇 |
1973年 | 199篇 |
1972年 | 229篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
331.
Social insects use complex chemical communication systems to govern many aspects of their life. We studied chemical changes in Dufours gland secretions associated with ovary development in several genotypes of honeybees. We found that C28–C38 esters were associated only with cavity nesting honeybee queens, while the alcohol eicosenol was associated only with their non-laying workers. In contrast, both egg-laying anarchistic workers and all parasitic Cape workers from queenright colonies showed the typical queen pattern (i.e. esters present and eicosenol absent), while egg-laying wild-type and anarchistic workers in queenless colonies showed an intermediate pattern, producing both esters and eicosenol but at intermediate levels. Furthermore, neither esters nor eicosenol were found in aerial nesting honeybee species. Both esters and eicosenol are biosynthetically similar compounds since both are recognizable products of fatty acid biosynthesis. Therefore, we propose that in honeybees the biosynthesis of esters and eicosenol in the Dufours gland is caste-regulated and this pathway has been conserved over evolutionary time. 相似文献
332.
333.
E. A. Loupian A. A. Mazurov E. V. Flitman D. V. Ershov G. N. Korovin V. P. Novik N. A. Abushenko D. A. Altyntsev V. V. Koshelev S. A. Tashchilin A. V. Tatarnikov I. Csiszar A. I. Sukhinin E. I. Ponomarev S. V. Afonin V. V. Belov G. G. Matvienko T. Loboda 《Mitigation and Adaptation Strategies for Global Change》2006,11(1):113-145
334.
L. V. Mukhortova I. N. Bezkorovainaya 《Mitigation and Adaptation Strategies for Global Change》2006,11(1):191-202
The evaluation of biospheric role of the boreal forests in the accumulation of carbon is connected with the evaluation of
organic matter (OM) pool in soils. The research sites were larch forests, they are situated on Nizhne-Tungusskoe Plateau.
Larch forests of feather-moss and lichen types (110 and 380 years old) were formed on 'ochric podbur' soils. Litter stocks
are 3.5–4.5 kg m− 2 with thickness 10–25 cm. Cryomezomorphic northern taiga soils contains 38–73 t (carbon) ha− 1. Pool of fast mineralized OM has average value 38.1 t (carbon) ha− 1, including 20.5 and 6.4 t (Carbon) ha− 1 of labile compounds on surface and in the soil, and 11.2 t (carbon) ha− 1 of mobile OM. Microbial mass reaches 1.78–3.47 t (carbon) ha− 1, its proportion is 3.6–4.9% of the total OM carbon. Zoomass of feather-moss larch forest is 0.20–0.61 * 10− 2, in lichen larch forest −0.01–0.07 * 10− 2 t (carbon) ha− 1. A pool of resistant to biological decomposition and bonded to mineral soil matrix OM is 17.7 t (carbon) ha− 1 and it varies from 18.6 to 29.0 in feather-moss larch forest, and from 6.4 to 17.0 t (carbon) ha− 1 in lichen larch forest. Two-years field experiment has been performed to determine transformation rates of various plant
litter fractions and to clarify the role of soil biota in these processes. The results showed participation of all biota groups
in the decomposition of plant residues caused weight loss of larch-needles and root mortmass. Isolation of organic matter
from all-size invertebrate groups leads to some decrease of decomposition activity. 相似文献
335.
Among social insects such as ants, scouts that modulate their recruiting behaviour, following simple rules based on local information, generate collective patterns of foraging. Here we demonstrate that features of the abiotic environment, specifically the foraging substrate, may also be influential in the emergence of group-level decisions such as the choice of one foraging path. Experimental data and theoretical analyses show that the collective patterns can arise independently of behavioural changes of individual scouts and can result, through self-organising processes, from the physico-chemical properties of the environment that alter the dynamics of information transfer by chemical trails. 相似文献
336.
337.
338.
339.
J. Heinze H. Remmert F. L. Boschke D. Reinen L. Jaenicke 《Die Naturwissenschaften》1983,70(11):575-576
340.
Pheromones — semiochemicals used by insects for intraspecific chemical communication — can be isolated and with special analytical techniques their chemical structure elucidated. With stereoselective synthesis methods, presented by the preparation of sex attractants and aggregating pheromones of moths and beetles, respectively, a synthetic access to compounds is given which can be used for behavior manipulation of insects. Aside the importance of these compounds for investigations of the sensoric process the possibility of their application in an integrated and biological pest control is discussed. 相似文献