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511.
G. F. Peterken 《Global Ecology and Biogeography》1999,8(5):321-328
Near-to-nature forestry is an attractive concept, but it is difficult to apply in a landscape where (i) the remaining fragments of original-natural forests are small and far apart; (ii) most large forests are secondary and very artificial; (iii) long-naturalized trees and other forest species are present throughout the country, and; (iv) natural disturbance regimes and their consequences cannot readily be observed. This paper summarizes the issues and problems relating to ancient seminatural woods and conifer plantation forests in Britain. Measures are indicated that would bring their management nearer to nature. Natural elements can be incorporated into stand composition, stand structure, processes and patterns, provided general principles are interpreted in a pragmatic and flexible manner. 相似文献
512.
JOAN WATSON F.L.S. 《Botanical journal of the Linnean Society. Linnean Society of London》1983,86(1-2):161-167
Conifer fragments from the Lower Cretaceous of Sudan are preserved as internal and external silica moulds. Low viscosity silicone rubber has been used to prepare casts showing fine epidermal details which enable identification of the plants. One is I'seudofrenelopsis parceramosa (Fontaine) Watson, the other is described as a new species of Frenelopsis Schenk. 相似文献
513.
Effect of Planting Season, Bunchgrass Species, and Neighbor Control on the Success of Transplants for Grassland Restoration 总被引:1,自引:0,他引:1
Constraints to grassland and open forest restoration (e.g., poor seed sources, yearly variation in establishment, and the persistence of weeds) necessitate the development of innovative methods to restore bunchgrass communities. We assessed the use of two native bunchgrass transplants, Bluebunch wheatgrass (Pseudoroegneria spicata) and Spreading needlegrass (Achnatherum richardsonii), for restoration within thinned montane forest communities of southeastern British Columbia, Canada. Fall and spring plantings were examined, either with or without glyphosate treatments to Pinegrass (Calamagrostis rubescens) neighbors. Calamagrostis rubescens is abundant in grassland affected by tree encroachment and may limit transplant establishment. Bunchgrass survival was positively associated (p < 0.05) with transplant size. Although P. spicata survival was greater (p < 0.01) with fall (81%) than with spring (44%) planting, survival of A. richardsonii was greater (p < 0.01) when planted in the spring (68 vs. 23%). Reduction of C. rubescens led to a relatively small but significant increase (p < 0.05) in bunchgrass survival by 7%. The summer after planting, changes in transplant tiller number varied by bunchgrass species, planting season, and treatment of neighboring C. rubescens. Removal of neighboring C. rubescens generally increased the number of tillers (or reduced tiller loss) but only within fall‐planted A. richardsonii and spring‐planted P. spicata. Both A. richardsonii and P. spicata transplants have potential for understory restoration within thinned montane forests, particularly using larger individuals, although to maximize survival, these species should be planted in the spring and fall, respectively. Reduction of C. rubescens may also enhance transplant survival and in some cases growth. 相似文献
514.
Participatory planning, management and alternative livelihoods for poor wetland-dependent communities in Kampala, Uganda 总被引:1,自引:0,他引:1
The paper is based on an on-going 3-year study in the wetland communities of Kampala. The study uses participatory methods and aims to contribute to (i) the development of low-income wetland communities, (ii) to prepare these communities to become less dependent on wetlands without receding into poverty, and (iii) the better management of the wetlands. The communities in direct dependence and intimate interaction with Nakivubo wetlands are mainly poor, live and work under hazardous conditions, and their activities pose a threat to the ecological function of the wetlands. Yet these wetlands are important for filtering the city's waste and storm water before it flows into Lake Victoria's Murchison Bay, which is Kampala's source of piped water. Government approaches to the problem of wetland encroachment have largely failed because they are confrontational, and are not consistent or participatory. The study has in the first year conducted a series of activities including stakeholder analysis, resource analysis, livelihood analysis, a questionnaire survey and action planning. Preliminary data show that wetland dependency is very high among the poor nearby communities. They practice cultivation, brick-making and harvesting of wetland vegetation. However, these activities are under threat because wetland resources are dwindling due to increasing population and over-use. Livelihoods are threatened not only by the decreasing productivity of the wetland, but also by the ever-present government threat to evict wetland encroachers to restore its ecology. The study therefore works with communities to prepare for less dependence on wetlands so that they do not suddenly recede into worse poverty if they are evicted. They formulate strategies to enhance alternative livelihood, and for management of the wetland. Action plans have been formulated to address the situation through a newly created association. 相似文献
515.
In our previous article (Odion and Hanson, Ecosystems 9:1177–89, 2006), we reported that fire severity in the conifer forests of the Sierra Nevada mountains of California, contrary
to prevailing assumptions, did not burn with predominately stand-replacing, high severity fire. The reply by Safford and others
(Ecosystems, this issue) using a new mapping approach also found this pattern. Their methods identify more high severity fire; however,
as we illustrate here, this may be attributed to the different mapping approaches used. We previously also found that condition
class based upon fire return interval departure (FRID) was not an effective predictor of fire severity. Safford and others
(this issue) concluded that there was a strong correlation between FRID-based condition class and fire severity based upon
data from the McNally fire of 2002. The difference between these findings about McNally fire reflects the fact that they combined
FRID categories whereas we kept the categories separate. Here, using their fire severity data to evaluate all three fires,
we found that severity was not predicted by FRID. Developing a consensus definition of fire severity within the scientific
community might help alleviate future contradictions regarding fire effects. 相似文献
516.