全文获取类型
收费全文 | 2923篇 |
免费 | 36篇 |
国内免费 | 20篇 |
专业分类
安全科学 | 70篇 |
废物处理 | 111篇 |
环保管理 | 367篇 |
综合类 | 959篇 |
基础理论 | 564篇 |
环境理论 | 4篇 |
污染及防治 | 636篇 |
评价与监测 | 161篇 |
社会与环境 | 100篇 |
灾害及防治 | 7篇 |
出版年
2023年 | 20篇 |
2022年 | 21篇 |
2021年 | 29篇 |
2020年 | 29篇 |
2019年 | 25篇 |
2018年 | 47篇 |
2017年 | 62篇 |
2016年 | 46篇 |
2015年 | 56篇 |
2014年 | 59篇 |
2013年 | 164篇 |
2012年 | 105篇 |
2011年 | 136篇 |
2010年 | 99篇 |
2009年 | 119篇 |
2008年 | 118篇 |
2007年 | 141篇 |
2006年 | 110篇 |
2005年 | 104篇 |
2004年 | 108篇 |
2003年 | 99篇 |
2002年 | 102篇 |
2001年 | 46篇 |
2000年 | 34篇 |
1999年 | 22篇 |
1998年 | 30篇 |
1997年 | 27篇 |
1996年 | 22篇 |
1995年 | 37篇 |
1994年 | 37篇 |
1993年 | 22篇 |
1992年 | 23篇 |
1991年 | 20篇 |
1990年 | 18篇 |
1989年 | 19篇 |
1988年 | 18篇 |
1986年 | 18篇 |
1979年 | 18篇 |
1965年 | 18篇 |
1963年 | 28篇 |
1962年 | 19篇 |
1961年 | 17篇 |
1960年 | 25篇 |
1959年 | 25篇 |
1958年 | 17篇 |
1957年 | 19篇 |
1955年 | 31篇 |
1954年 | 41篇 |
1953年 | 22篇 |
1951年 | 24篇 |
排序方式: 共有2979条查询结果,搜索用时 0 毫秒
261.
Martin J. Atkins Michael R.W. Walmsley James R. Neale 《Journal of Cleaner Production》2010,18(9):927-934
The integration of non-continuous processes such as a milk powder plant presents a challenge for existing process integration techniques. Current techniques are generally based on steady and continuous operation which for some industries is not the case. Milk production varies considerably during the year as dairy cows in New Zealand are grazed on pasture. In this paper the potential for indirect heat transfer between the several plants using a heat recovery loop and stratified tank at a typical New Zealand dairy factory is investigated. The maximum amount of heat recovery is calculated for a range of recirculation loop temperatures. The maximum amount of heat recovery can be increased considerably if the temperature of the hot fluid in the recirculation loop is varied depending on which condition the site is operating under. 相似文献
262.
J. Besseau-Ayasse C. Violle-Poirsier A. Bazin N. Gruchy A. Moncla F. Girard M. Till F. Mugneret A. Coussement F. Pelluard M. Jimenez P. Vago M. F. Portnoï C. Dupont C. Beneteau F. Amblard M. Valduga J. L. Bresson F. Carré-Pigeon N. Le Meur S. Tapia C. Yardin A. Receveur J. Lespinasse E. Pipiras M. P. Beaujard P. Teboul S. Brisset M. Catty E. Nowak N. Douet Guilbert H. Lallaoui S. Bouquillon V. Gatinois G. Joly-Helas F. Prieur F. Cartault D. Martin P. Kleinfinger D. Molina Gomes M. Doco-Fenzy F. Vialard 《黑龙江环境通报》2014,34(5):424-430
263.
Molly Johnston Chanelle Warton Mark D. Pertile Michelle Taylor-Sands Martin B. Delatycki Lisa Hui Julian Savulescu Catherine Mills 《黑龙江环境通报》2023,43(2):226-234
Prenatal screening for sex chromosome aneuploidies (SCAs) is increasingly available through expanded non-invasive prenatal testing (NIPT). NIPT for SCAs raises complex ethical issues for clinical providers, prospective parents and future children. This paper discusses the ethical issues that arise around NIPT for SCAs and current guidelines and protocols for management. The first section outlines current practice and the limitations of NIPT for SCAs. It then outlines key guidelines before discussing the ethical issues raised by this use of NIPT. We conclude that while screening for SCAs should be made available for people seeking to use NIPT, its implementation requires careful consideration of what, when and how information is provided to users. 相似文献
264.
265.
Choosy males from the underground: male mating preferences in surface- and cave-dwelling Atlantic mollies (Poecilia mexicana) 总被引:3,自引:0,他引:3
Atlantic mollies (Poecilia mexicana) inhabit a variety of surface habitats, but they also occur in a sulfur cave in southern Mexico. We examined male mate choice
relative to female body size in the cave population and in the most closely related surface-dwelling population from a nearby
river. Males from both populations were either light- or dark-reared and could choose between two differently sized females
either on the basis of visual cues in light or on the basis of solely nonvisual cues in darkness. Sexual preferences were
estimated from the degree of association. Cave molly males always showed a preference for the larger female, both in light
and in darkness. Among the surface males, only light-reared males showed a preference in the visual cues test, but not in
darkness. In a control experiment, we demonstrated that male association preferences directly translate into actual mating
preferences. Apparently, using visual cues for mate choice is the ancestral state in this system, and using nonvisual cues
has evolved as a novel trait in the cave population. We discuss the evolution of nonvisual male mate choice in the context
of changed environmental conditions, namely the absence of light, hypoxia, and toxic hydrogen sulfide in the cave. 相似文献
266.
The famous idea of Ernst Mach concerning the non-absolute but relational character of particle inertia is taken up in this paper and is reinvestigated with respect to its cosmological implications. From Thirring’s general relativistic study of the old Newtonian problem of the relativity of rotations in different reference systems, it appears that the equivalence principle with respect to rotating reference systems, if at all, can only be extended to the system of the whole universe, if the mass of the universe scales with the effective radius or extent of the universe. A reanalysis of Thirring’s derivations still reveals this astonishing result, and thus the general question must be posed: how serious this result has to be taken with respect to cosmological implications. As we will show, the equivalence principle is, in fact, fulfilled by a universe with vanishing curvature, i.e. with a curvature parameter, which just has the critical density , where is the Hubble constant. It turns out, however, that this principle can only permanently be fulfilled in an evolving cosmos, if the cosmic mass density, different from its conventional behaviour, varies with the reciprocal of the squared cosmic scale. This, in fact, would automatically be realized, if the mass of each cosmic particle scales with the scale of the universe. The latter fact, on one hand, is a field-theoretical request from a general relativistic field theory which fulfills H. Weyl’s requirement of a conformal scale invariance. On the other hand, it can perhaps also be concluded on purely physical grounds, when taking into account that as source of the cosmic metrics only an effective mass density can be taken. This mass density represents the bare mass density reduced by its mass equivalent of gravitational self-binding energy. Some interesting cosmological conclusions connected with this fact are pointed out in this paper. 相似文献
267.
Herman Hedriana Kimberly Martin Daniel Saltzman Paul Billings Zachary Demko Peter Benn 《黑龙江环境通报》2020,40(2):179-184
Objectives
The performance of noninvasive prenatal screening (NIPS) for fetal aneuploidy in twin pregnancies is dependent on the amount of placentally derived cell-free DNA, the “fetal fraction (FF),” present in maternal plasma. We report FF values in monozygotic (MZ) and dizygotic (DZ) pregnancies.Methods
We reviewed FF in pregnancies at 10 to 20 completed weeks gestational age based on single-nucleotide polymorphism (SNP)-based NIPS where zygosity was routinely established in twin pregnancies. The cohort included 121 446 (96.3%) singleton, 1454 (1.2%) MZ, and 3161 (2.5%) DZ pregnancies. For DZ twins, individual FFs were measured.Results
Combined FF for DZ and MZ fetuses were 35% and 26% greater than singletons, respectively. The individual FF contributions from each fetus in DZ twins were, on average, 32% less than singletons. FF in DZ twin pairs were moderately correlated (Pearson correlation coefficient.66). When a threshold of 2.8% FF was applied to define uninterpretable results, 1.7% (2102/121 446) of singletons, 0.8% (11/1454) of MZ pairs, and 5.6% (178/3161) of DZ pairs were uninterpretable.Conclusion
For optimal aneuploidy NIPS in twin pregnancies, zygosity should be established and in DZ twins FF for both fetuses should be determined to identify those cases where results can be reliably interpreted. 相似文献268.
Lisa Smeester Elizabeth M. Martin Pete Cable Wanda Bodnar Kim Boggess Neeta L. Vora Rebecca C. Fry 《黑龙江环境通报》2017,37(13):1364-1366
Both exposures to toxic metals, as well as deficiencies in essential metals, during pregnancy has been linked to a variety of negative reproductive outcomes. The exact etiologies of such outcomes and the effects of fetal exposure to these metals are largely unknown. Therefore, the ability to assess levels of these elements is critical to determining the underlying causes of such conditions and the effects that both essential and nonessential metals have on fetal development. Thus, using cell-free fetal RNA from amniotic fluid, we set out to measure the association between amniotic fluid levels of toxic and essential metals and fetal gene expression. We find that arsenic was associated with increased expression of 3 genes known to play roles in both birth-related and reproductive effects. The results highlight the potential for detrimental health effects of prenatal metals exposure and the potential to identify biomarkers of environmental exposure during this critical developmental period. 相似文献
269.
270.
气候变化对淡水珍珠蚌种群的威胁 总被引:3,自引:0,他引:3
引言 在过去的100年中,淡水珍珠蚌Margaritfera margaritifera(L.)的数量在地球北区范围内已经下降到被IUCN列为濒危品种[1].人们认为主要原因是严重的工业污染和农业(有机)污染,采珠渔民的过度开采,寄主鲑科鱼类的减少,以及由于水力发电和河流管理计划的实施所造成的自然河床栖息环境的退化[2]. 相似文献