全文获取类型
收费全文 | 2664篇 |
免费 | 227篇 |
国内免费 | 370篇 |
专业分类
安全科学 | 481篇 |
废物处理 | 47篇 |
环保管理 | 424篇 |
综合类 | 1430篇 |
基础理论 | 349篇 |
环境理论 | 1篇 |
污染及防治 | 94篇 |
评价与监测 | 135篇 |
社会与环境 | 224篇 |
灾害及防治 | 76篇 |
出版年
2024年 | 7篇 |
2023年 | 27篇 |
2022年 | 79篇 |
2021年 | 87篇 |
2020年 | 85篇 |
2019年 | 89篇 |
2018年 | 75篇 |
2017年 | 94篇 |
2016年 | 119篇 |
2015年 | 116篇 |
2014年 | 116篇 |
2013年 | 137篇 |
2012年 | 201篇 |
2011年 | 205篇 |
2010年 | 187篇 |
2009年 | 177篇 |
2008年 | 105篇 |
2007年 | 213篇 |
2006年 | 197篇 |
2005年 | 128篇 |
2004年 | 107篇 |
2003年 | 102篇 |
2002年 | 95篇 |
2001年 | 68篇 |
2000年 | 82篇 |
1999年 | 58篇 |
1998年 | 48篇 |
1997年 | 40篇 |
1996年 | 44篇 |
1995年 | 36篇 |
1994年 | 20篇 |
1993年 | 26篇 |
1992年 | 29篇 |
1991年 | 14篇 |
1990年 | 12篇 |
1989年 | 6篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有3261条查询结果,搜索用时 187 毫秒
941.
942.
Coral Reef Habitats as Surrogates of Species, Ecological Functions, and Ecosystem Services 总被引:3,自引:0,他引:3
PETER J. MUMBY††† KENNETH BROAD† DANIEL R. BRUMBAUGH‡§ CRAIG P. DAHLGREN ALASTAIR R. HARBORNE ALAN HASTINGS†† KATHERINE E. HOLMES‡ CARRIE V. KAPPEL‡‡ FIORENZA MICHELI§§ JAMES N. SANCHIRICO 《Conservation biology》2008,22(4):941-951
Abstract: Habitat maps are often the core spatially consistent data set on which marine reserve networks are designed, but their efficacy as surrogates for species richness and applicability to other conservation measures is poorly understood. Combining an analysis of field survey data, literature review, and expert assessment by a multidisciplinary working group, we examined the degree to which Caribbean coastal habitats provide useful planning information on 4 conservation measures: species richness, the ecological functions of fish species, ecosystem processes, and ecosystem services. Approximately one‐quarter to one‐third of benthic invertebrate species and fish species (disaggregated by life phase; hereafter fish species) occurred in a single habitat, and Montastraea‐dominated forereefs consistently had the highest richness of all species, processes, and services. All 11 habitats were needed to represent all 277 fish species in the seascape, although reducing the conservation target to 95% of species approximately halved the number of habitats required to ensure representation. Species accumulation indices (SAIs) were used to compare the efficacy of surrogates and revealed that fish species were a more appropriate surrogate of benthic species (SAI = 71%) than benthic species were for fishes (SAI = 42%). Species of reef fishes were also distributed more widely across the seascape than invertebrates and therefore their use as a surrogate simultaneously included mangroves, sea grass, and coral reef habitats. Functional classes of fishes served as effective surrogates of fish and benthic species which, given their ease to survey, makes them a particularly useful measure for conservation planning. Ecosystem processes and services exhibited great redundancy among habitats and were ineffective as surrogates of species. Therefore, processes and services in this case were generally unsuitable for a complementarity‐based approach to reserve design. In contrast, the representation of species or functional classes ensured inclusion of all processes and services in the reserve network. 相似文献
943.
Some characteristics of the distribution of heavy metals
in urban topsoil of Xuzhou,China 总被引:3,自引:0,他引:3
An assessment is presented of distribution characteristics of heavy metals in the urban topsoil from the city of Xuzhou. The
concentrations of Ag, Al, As, Au, Ba, Be, Bi, Cd, Co, Cr, Cu, Fe, Ga, Hg, Li, Mn, Mo, Ni, Pb, Pd, Pt, Sb, Sc, Se, Sn, V and
Zn have been determined from 21 soil samples. Examination of lognormal distribution plots indicates that the diagrams of Al,
Be, Fe, Ga, Li, and V are almost linear suggesting that these metals are almost unaffected by anthropogenic activities while
the plots for As, Cd, Cu, Pb, Pd, Pt, Se, Zn and others are not linear probably due to anthropogenic activities from which
these metals are delivered to the soils. Al is used for mineralogical normalization of these data. An evaluation of background
values for topsoil is also carried out by means of lognormal distribution plots. The results show our background values obtained
from the lognormal distribution plots are comparable to those values of uncontaminated soils of Xuzhou obtained by previous
work except for Cd and Hg. At present, no explanation for the exceptions Cd and Hg can be given. 相似文献
944.
pH5条件下生物制氢反应器的启动及运行特性 总被引:12,自引:2,他引:10
采用连续流搅拌槽式反应器(CSTR),以糖蜜废水为底物,探讨了pH5条件下生物制氢反应器的启动和运行特性.结果表明,保持反应器内pH为5,污泥接种量为6g/L、COD启动负荷为7.0kg/(m3·d)、水力停留时间(HRT)为6h等条件,可在30d内完成产氢发酵菌群的驯化.此时系统氧化还原电位(ORP)稳定在-460mV~-480mV之间,系统呈现明显的混合酸发酵特性.其液相末端发酵产物比例分布相当,乙酸、乙醇、丁酸、丙酸和戊酸含量分别占发酵产物总含量的36%,33%,18%,13%.没有占绝对优势的发酵产物.气相中的氢气含量30%~35%,其最大产氢能力为1.3m3/(m3·d).生物制氢反应器混合酸发酵稳定运行期各种产酸发酵细菌处于均势地位,以球菌和杆菌为主. 相似文献
945.
946.
947.
948.
949.
Conservation of representative facets of geophysical diversity may help conserve biological diversity as the climate changes. We conducted a global classification of terrestrial geophysical diversity and analyzed how land protection varies across geophysical diversity types. Geophysical diversity was classified in terms of soil type, elevation, and biogeographic realm and then compared to the global distribution of protected areas in 2012. We found that 300 (45%) of 672 broad geophysical diversity types currently meet the Convention on Biological Diversity's Aichi Target 11 of 17% terrestrial areal protection, which suggested that efforts to implement geophysical diversity conservation have a substantive basis on which to build. However, current protected areas were heavily biased toward high elevation and low fertility soils. We assessed 3 scenarios of protected area expansion and found that protection focused on threatened species, if fully implemented, would also protect an additional 29% of geophysical diversity types, ecoregional‐focused protection would protect an additional 24%, and a combined scenario would protect an additional 42%. Future efforts need to specifically target low‐elevation sites with productive soils for protection and manage for connectivity among geophysical diversity types. These efforts may be hampered by the sheer number of geophysical diversity facets that the world contains, which makes clear target setting and prioritization an important next step. 相似文献
950.
Stefano Canessa Sarah J. Converse Matt West Nick Clemann Graeme Gillespie Michael McFadden Aimee J. Silla Kirsten M. Parris Michael A. McCarthy 《Conservation biology》2016,30(3):599-609
Ex situ conservation strategies for threatened species often require long‐term commitment and financial investment to achieve management objectives. We present a framework that considers the decision to adopt ex situ management for a target species as the end point of several linked decisions. We used a decision tree to intuitively represent the logical sequence of decision making. The first decision is to identify the specific management actions most likely to achieve the fundamental objectives of the recovery plan, with or without the use of ex‐situ populations. Once this decision has been made, one decides whether to establish an ex situ population, accounting for the probability of success in the initial phase of the recovery plan, for example, the probability of successful breeding in captivity. Approaching these decisions in the reverse order (attempting to establish an ex situ population before its purpose is clearly defined) can lead to a poor allocation of resources, because it may restrict the range of available decisions in the second stage. We applied our decision framework to the recovery program for the threatened spotted tree frog (Litoria spenceri) of southeastern Australia. Across a range of possible management actions, only those including ex situ management were expected to provide >50% probability of the species’ persistence, but these actions cost more than use of in situ alternatives only. The expected benefits of ex situ actions were predicted to be offset by additional uncertainty and stochasticity associated with establishing and maintaining ex situ populations. Naïvely implementing ex situ conservation strategies can lead to inefficient management. Our framework may help managers explicitly evaluate objectives, management options, and the probability of success prior to establishing a captive colony of any given species. 相似文献