全文获取类型
收费全文 | 23036篇 |
免费 | 188篇 |
国内免费 | 120篇 |
专业分类
安全科学 | 480篇 |
废物处理 | 1425篇 |
环保管理 | 3054篇 |
综合类 | 2514篇 |
基础理论 | 6653篇 |
环境理论 | 5篇 |
污染及防治 | 5054篇 |
评价与监测 | 1920篇 |
社会与环境 | 2153篇 |
灾害及防治 | 86篇 |
出版年
2023年 | 57篇 |
2022年 | 115篇 |
2021年 | 105篇 |
2020年 | 92篇 |
2019年 | 103篇 |
2018年 | 1740篇 |
2017年 | 1656篇 |
2016年 | 1534篇 |
2015年 | 365篇 |
2014年 | 318篇 |
2013年 | 981篇 |
2012年 | 874篇 |
2011年 | 1999篇 |
2010年 | 1283篇 |
2009年 | 1186篇 |
2008年 | 1583篇 |
2007年 | 1986篇 |
2006年 | 556篇 |
2005年 | 548篇 |
2004年 | 455篇 |
2003年 | 616篇 |
2002年 | 575篇 |
2001年 | 583篇 |
2000年 | 398篇 |
1999年 | 240篇 |
1998年 | 202篇 |
1997年 | 169篇 |
1996年 | 172篇 |
1995年 | 199篇 |
1994年 | 165篇 |
1993年 | 136篇 |
1992年 | 147篇 |
1991年 | 144篇 |
1990年 | 143篇 |
1989年 | 141篇 |
1988年 | 111篇 |
1987年 | 107篇 |
1986年 | 78篇 |
1985年 | 109篇 |
1984年 | 119篇 |
1983年 | 114篇 |
1982年 | 100篇 |
1981年 | 96篇 |
1980年 | 73篇 |
1979年 | 77篇 |
1978年 | 51篇 |
1977年 | 61篇 |
1975年 | 56篇 |
1974年 | 57篇 |
1973年 | 55篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Francesca Porri Gerardo I. Zardi Christopher D. McQuaid Sarah Radloff 《Marine Biology》2007,152(3):631-637
Settlement is a major determinant of intertidal populations. However, the energy costs of lost larvae are very high. Accordingly,
arrival and attachment on suitable substrata are essential requirements for species’ survival. On the intertidal, the presence
of cues left by adult or juvenile conspecifics could be vital for the successful establishment of larvae arriving on the shore.
Two mussel species, the indigenous Perna perna and the invasive Mytilus galloprovincialis, co-occur on the lower eulittoral zone on the south coast of South Africa. P.
perna dominates the low and M. galloprovincialis the high mussel zones, with co-existence in the mid mussel zone. This study tested the hypothesis of settlement selectivity
for conspecifics in these two mussel species, to understand whether the final adult distribution of mussels on the shores
is determined by active behavioural and chemical mechanisms. Preferential selection by larvae for conspecifics was tested
in the field during the peak settlement period in 2004 in natural mussel beds across zones and through manipulative experiments
in the mid-zone where the species co-exist. On natural beds, settlement was determined by counts of settlers attached over
48 h onto artificial collectors. Collectors were placed on beds of P. perna and M. galloprovincialis present at both high- and low-adult densities, as well as in mixed beds. On such natural beds, settlers of both species consistently
favored low-zone P. perna beds. Settlement patterns over 24 h onto experimentally created mussel patches consisting of P.
perna, M. galloprovincialis or the two species combined beds, set in the mixed zone, did not conform with the results of the natural beds study: settlers
of both species settled with no discrimination among different patches. The results indicate that mussels, which are sedentary,
lack attraction to conspecifics at settlement. This highlights the importance of tidal height in setting settlement rates,
and of post-settlement events in shaping populations of these broadcast spawners. 相似文献
982.
983.
This paper is concerned with the sustainable development of a self-drive tourist destination in the remote region in Northern
Australia. It first compares officially used data on visitor profiles to the information collected in the survey. Differences
between data collected and available secondary data imply that tourism planning should include collection of region-specific
tourism information to guide and mitigate potential environmental changes. Natural landscape features are the key attraction
for visitors to the region. Visitor satisfaction levels with the current state of the destination are high. However, local
residents reported perceived negative impacts of tourism, in particular on amenities and the ecology of the landscape. Visitors
also reported behavior that might contribute to environmental impacts. Implications of the findings, in the context of future
destination planning, are discussed. 相似文献
984.
In the framework of dynamic morphology theory, the centers of gravity and geometric centers of projections have been determined for the bodies of more than 182 forms of invertebrates, and these data have been used to distinguish four types of dynamic body shapes. It has been demonstrated that specific dynamic types of body shape are characteristic of individual taxa. In addition, there are a group of “transformers,” which may assume any dynamic type of shape, and a group of invertebrates with one predominant dynamic type. 相似文献
985.
Direct solid sampling Zeeman atomic absorption spectrometric methods were developed and successfully applied to the determination of mercury, cadmium, lead and manganese in aquatic plants. Mercury was determined using a specially designed furnace. The other elements were determined by a third generation spectrometer. In 3-field- and dynamic mode the working range was substantially extended and high amounts of analyte were detectable without laborious dilution of solid samples. The measurements were based on calibrations using certified reference materials of organic origin. No matrix effects were observed under the optimised conditions. Results obtained were in good agreement with the certified values. 相似文献
986.
987.
988.
Fabio Orecchini 《Sustainability Science》2007,2(2):245-252
Human society consumes resources that it is not able to reproduce. Human activities are still based on “open cycles,” starting
from a condition of natural environmental balance and reaching an environmental imbalance. The challenging scope of scientific
and technological research towards sustainability appears clear if it is based on this analysis: to find development systems
based on “closed cycles” of resources. The challenging objective of realizing closed cycles leads to a definition of sustainability
that indicates the path to sustainable development, as well as stating the general principle. It also provides a key to the
qualitative measurement of sustainability. This means that the sustainability level of a system can be measured by measuring
its capacity to avoid the consumption of resources. Zero consumption is a necessary condition for sustainability, and brings
about as a side effect the highly desired “zero-waste” result. Materials entering the proposed endless scheme pass through
the process of usefulness without losing their capacity to feed the system again after being used. Thus, the concept of “consumption”
itself is replaced by one of “use” when resources are inserted into closed loops capable of feeding human development. The
application of the closed cycle sustainability criterion particularly displays its feasibility, and a theoretical guiding
role, in the energy sector. Energy vectors such as hydrogen and electricity enable the closure of the energy resources loop
by effectively approaching the objective of “zero consumption” (and the side result of “zero waste”) through already demonstrated
technological solutions. 相似文献
989.
Advanced terrestrial ecosystem analysis and modelling 总被引:1,自引:0,他引:1
Wolfgang Cramer 《Regional Environmental Change》2008,8(3):89-90
990.
This study estimates efficient nitrogen load reductions to the Stockholm archipelago, a Swedish coastal zone in the Baltic
Sea, and compares these with politically determined and implemented nitrogen abatement programs. The region is relatively
well equipped with necessary data, and a simple programming model is constructed. The results show a large divergence in efficient
nitrogen reductions, mainly due to the divergences in benefit estimates from water quality improvements in the archipelago.
However, the results need to be interpreted with caution due to all uncertainties related to predicting net values from changes
in nitrogen load to a coastal zone. In spite of this, it is still of policy relevance to infer results which show that the
politically determined target coincides with an efficient nitrogen reduction at relatively low benefit estimate, but that
actual net benefits could be increased from a reallocation of abatement measures towards more low cost measures. 相似文献