全文获取类型
收费全文 | 415篇 |
免费 | 125篇 |
国内免费 | 53篇 |
专业分类
安全科学 | 17篇 |
废物处理 | 19篇 |
环保管理 | 10篇 |
综合类 | 166篇 |
基础理论 | 328篇 |
污染及防治 | 31篇 |
评价与监测 | 10篇 |
社会与环境 | 6篇 |
灾害及防治 | 6篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 5篇 |
2019年 | 5篇 |
2018年 | 49篇 |
2017年 | 28篇 |
2016年 | 30篇 |
2015年 | 33篇 |
2014年 | 41篇 |
2013年 | 62篇 |
2012年 | 25篇 |
2011年 | 39篇 |
2010年 | 32篇 |
2009年 | 19篇 |
2008年 | 27篇 |
2007年 | 10篇 |
2006年 | 13篇 |
2005年 | 21篇 |
2004年 | 30篇 |
2003年 | 14篇 |
2002年 | 10篇 |
2001年 | 16篇 |
2000年 | 9篇 |
1999年 | 9篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1982年 | 2篇 |
排序方式: 共有593条查询结果,搜索用时 15 毫秒
81.
A number of studies have observed differences in the evaluation of visual, aesthetic stimuli between those with and without professional training in art and design. If exposure to design training underlies such differences it follows that evidence of training effects should be observable when comparing subjects at different stages of design training, and not observable when comparing subjects at different stages of non-design training. In addition, this evidence should be consistent with directional predictions. The study reported in this paper investigated this question using a sample of 192 trained and untrained subjects in an evaluative task. Subjects were from two departments (Design and Computer Studies) of the same educational establishment and comprised balanced groups of lecturers, 1st, 2nd and 3rd year undergraduate students. The results obtained demonstrated evaluative differences and patterns of association both within and between the subject groups consistent with a training hypothesis. 相似文献
82.
83.
R. Saura W. Traore L. Taine Z. Q. Wen D. Roux B. Maugey-Laulom M. Ruffie A. Vergnaud J. Horovitz 《黑龙江环境通报》1995,15(7):609-614
Six prenatally diagnosed cases of trisomy 9 are reported and 22 previously reported cases are reviewed; the difficulty of genetic counselling for such cases and the variation in the percentage of trisomic cells in different tissues, thus making accurate diagnosis of trisomy 9 difficult, are emphasized. In addition to karyotyping results, ultrasound findings are important in achieving diagnoses. Finally, a course of action when prenatal trisomy 9 is detected is proposed. 相似文献
84.
李衍 《中国特种设备安全》2012,(10):34-36
9%镍钢液化天然气储罐制造安装过程中,焊缝检验通常用常规射线照相(RT)进行。本文研讨用相控阵半自动超声检测(AUT)取代射线照相的工艺制定及验证方法。要领分四步:首先带缺陷专用焊接试样的制备;然后相控阵AUT工艺的编制;其次在有已知缺陷的焊接试样上,对AUTT艺作“开放性”验证试验;最后在现场对整个数据采集系统作“封闭性”操作演示和验证评定试验。验证结果表明相控阵AUT取代RT可行可靠,能凸显AUT种种优势。 相似文献
85.
Jurriaan M. De Vos Lucas N. Joppa John L. Gittleman Patrick R. Stephens Stuart L. Pimm 《Conservation biology》2015,29(2):452-462
A key measure of humanity's global impact is by how much it has increased species extinction rates. Familiar statements are that these are 100–1000 times pre‐human or background extinction levels. Estimating recent rates is straightforward, but establishing a background rate for comparison is not. Previous researchers chose an approximate benchmark of 1 extinction per million species per year (E/MSY). We explored disparate lines of evidence that suggest a substantially lower estimate. Fossil data yield direct estimates of extinction rates, but they are temporally coarse, mostly limited to marine hard‐bodied taxa, and generally involve genera not species. Based on these data, typical background loss is 0.01 genera per million genera per year. Molecular phylogenies are available for more taxa and ecosystems, but it is debated whether they can be used to estimate separately speciation and extinction rates. We selected data to address known concerns and used them to determine median extinction estimates from statistical distributions of probable values for terrestrial plants and animals. We then created simulations to explore effects of violating model assumptions. Finally, we compiled estimates of diversification—the difference between speciation and extinction rates for different taxa. Median estimates of extinction rates ranged from 0.023 to 0.135 E/MSY. Simulation results suggested over‐ and under‐estimation of extinction from individual phylogenies partially canceled each other out when large sets of phylogenies were analyzed. There was no evidence for recent and widespread pre‐human overall declines in diversity. This implies that average extinction rates are less than average diversification rates. Median diversification rates were 0.05–0.2 new species per million species per year. On the basis of these results, we concluded that typical rates of background extinction may be closer to 0.1 E/MSY. Thus, current extinction rates are 1,000 times higher than natural background rates of extinction and future rates are likely to be 10,000 times higher. Estimación de la Tasa Normal de Extinción de Especies 相似文献
86.
87.
The genetic diversity of populations, which contributes greatly to their adaptive potential, is negatively affected by anthropogenic habitat fragmentation and destruction. However, continental‐scale losses of genetic diversity also resulted from the population expansions that followed the end of the last glaciation, an element that is rarely considered in a conservation context. We addressed this issue in a meta‐analysis in which we compared the spatial patterns of vulnerability of 18 widespread European amphibians in light of phylogeographic histories (glacial refugia and postglacial routes) and anthropogenic disturbances. Conservation statuses significantly worsened with distances from refugia, particularly in the context of industrial agriculture; human population density also had a negative effect. These findings suggest that features associated with the loss of genetic diversity in post‐glacial amphibian populations (such as enhanced fixation load or depressed adaptive potential) may increase their susceptibility to current threats (e.g., habitat fragmentation and pesticide use). We propose that the phylogeographic status of populations (i.e., refugial vs. post‐glacial) should be considered in conservation assessments for regional and national red lists. 相似文献
88.
Assessing the components of adaptive capacity to improve conservation and management efforts under global change
下载免费PDF全文
![点击此处可从《Conservation biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Adrienne B. Nicotra Erik A. Beever Amanda L. Robertson Gretchen E. Hofmann John O'Leary 《Conservation biology》2015,29(5):1268-1278
Natural‐resource managers and other conservation practitioners are under unprecedented pressure to categorize and quantify the vulnerability of natural systems based on assessment of the exposure, sensitivity, and adaptive capacity of species to climate change. Despite the urgent need for these assessments, neither the theoretical basis of adaptive capacity nor the practical issues underlying its quantification has been articulated in a manner that is directly applicable to natural‐resource management. Both are critical for researchers, managers, and other conservation practitioners to develop reliable strategies for assessing adaptive capacity. Drawing from principles of classical and contemporary research and examples from terrestrial, marine, plant, and animal systems, we examined broadly the theory behind the concept of adaptive capacity. We then considered how interdisciplinary, trait‐ and triage‐based approaches encompassing the oft‐overlooked interactions among components of adaptive capacity can be used to identify species and populations likely to have higher (or lower) adaptive capacity. We identified the challenges and value of such endeavors and argue for a concerted interdisciplinary research approach that combines ecology, ecological genetics, and eco‐physiology to reflect the interacting components of adaptive capacity. We aimed to provide a basis for constructive discussion between natural‐resource managers and researchers, discussions urgently needed to identify research directions that will deliver answers to real‐world questions facing resource managers, other conservation practitioners, and policy makers. Directing research to both seek general patterns and identify ways to facilitate adaptive capacity of key species and populations within species, will enable conservation ecologists and resource managers to maximize returns on research and management investment and arrive at novel and dynamic management and policy decisions. 相似文献
89.
Implications of genetics and current protected areas for conservation of 5 endangered primates in China
下载免费PDF全文
![点击此处可从《Conservation biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Christian Roos Ziming Wang ZuoFu Xiang Pingfen Zhu Boshi Wang Baoping Ren Fanglei Shi Huijuan Pan Ming Li 《Conservation biology》2015,29(6):1508-1517
Most of China's 24–28 primate species are threatened with extinction. Habitat reduction and fragmentation are perhaps the greatest threats. We used published data from a conservation genetics study of 5 endangered primates in China (Rhinopithecus roxellana, R. bieti, R. brelichi, Trachypithecus francoisi, and T. leucocephalus); distribution data on these species; and the distribution, area, and location of protected areas to inform conservation strategies for these primates. All 5 species were separated into subpopulations with unique genetic components. Gene flow appeared to be strongly impeded by agricultural land, meadows used for grazing, highways, and humans dwellings. Most species declined severely or diverged concurrently as human population and crop land cover increased. Nature reserves were not evenly distributed across subpopulations with unique genetic backgrounds. Certain small subpopulations were severely fragmented and had higher extinction risk than others. Primate mobility is limited and their genetic structure is strong and susceptible to substantial loss of diversity due to local extinction. Thus, to maximize preservation of genetic diversity in all these primate species, our results suggest protection is required for all sub‐populations. Key priorities for their conservation include maintaining R. roxellana in Shennongjia national reserve, subpopulations S4 and S5 of R. bieti and of R. brelichi in Fanjingshan national reserve, subpopulation CGX of T. francoisi in central Guangxi Province, and all 3 T. leucocephalus sub‐populations in central Guangxi Province. 相似文献
90.
Seed plant phylogenetic diversity and species richness in conservation planning within a global biodiversity hotspot in eastern Asia
下载免费PDF全文
![点击此处可从《Conservation biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
One of the main goals of conservation biology is to understand the factors shaping variation in biodiversity across the planet. This understanding is critical for conservation planners to be able to develop effective conservation strategies. Although many studies have focused on species richness and the protection of rare and endemic species, less attention has been paid to the protection of the phylogenetic dimension of biodiversity. We explored how phylogenetic diversity, species richness, and phylogenetic community structure vary in seed plant communities along an elevational gradient in a relatively understudied high mountain region, the Dulong Valley, in southeastern Tibet, China. As expected, phylogenetic diversity was well correlated with species richness among the elevational bands and among communities. At the community level, evergreen broad‐leaved forests had the highest levels of species richness and phylogenetic diversity. Using null model analyses, we found evidence of nonrandom phylogenetic structure across the region. Evergreen broad‐leaved forests were phylogenetically overdispersed, whereas other vegetation types tended to be phylogenetically clustered. We suggest that communities with high species richness or overdispersed phylogenetic structure should be a focus for biodiversity conservation within the Dulong Valley because these areas may help maximize the potential of this flora to respond to future global change. In biodiversity hotspots worldwide, we suggest that the phylogenetic structure of a community may serve as a useful measure of phylogenetic diversity in the context of conservation planning. 相似文献