首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   177篇
  免费   5篇
  国内免费   2篇
安全科学   6篇
废物处理   4篇
环保管理   17篇
综合类   25篇
基础理论   64篇
环境理论   2篇
污染及防治   46篇
评价与监测   5篇
社会与环境   15篇
  2023年   1篇
  2022年   1篇
  2021年   1篇
  2020年   6篇
  2019年   3篇
  2018年   1篇
  2017年   11篇
  2016年   8篇
  2015年   2篇
  2014年   10篇
  2013年   12篇
  2012年   8篇
  2011年   17篇
  2010年   5篇
  2009年   8篇
  2008年   7篇
  2007年   6篇
  2006年   8篇
  2005年   5篇
  2004年   8篇
  2003年   6篇
  2002年   8篇
  2001年   7篇
  2000年   2篇
  1999年   4篇
  1996年   1篇
  1995年   1篇
  1994年   2篇
  1993年   1篇
  1991年   5篇
  1990年   1篇
  1986年   3篇
  1985年   1篇
  1984年   1篇
  1983年   1篇
  1982年   1篇
  1978年   1篇
  1976年   1篇
  1970年   1篇
  1958年   1篇
  1944年   4篇
  1943年   2篇
  1930年   1篇
排序方式: 共有184条查询结果,搜索用时 15 毫秒
1.
Chinese life cycle impact assessment factors   总被引:5,自引:0,他引:5  
IntroductionLifecycleassessment(LCA)isanenvironmentalmanagementtoolthatisusedtoexamineandevaluatetheenvironmentalimpactsassociatedwiththeexistenceofproducts(Jensen,1998;Weidema,1997;Wenzel,1997).ThefocusofLCAisontheentirelifecycleoftheproduct,i.e.fromtheextracti…  相似文献   
2.
The diurnal variation in apical length growth rate of five benthic macroalgae from the Swedish West Coast (Fucus spiralis L., F. vesiculosus L., F. serratus L., Ascophyllum nodosum (L.) Le Jolis, and Chondrus crispus Stackhouse) was measured during 1.5 to 2.0-h intervals for 3 to 5 d in September 1984. All species showed a maximum in growth rate in the morning, followed by a continuous decline throughout the rest of the day (most pronounced in F. serratus, A. nodosum and C. crispus). By comparing the growth rates with the average irradiance during the same interval, saturation irradiances for length growth in natural daylight regime were estimated; 60 to 70 Wm-2 for F. spiralis and F. vesiculosus, 90 to 100 Wm-2 for A. nodosum, 30 to 40 Wm-2 for F. serratus and 10 to 20 Wm-2 for C. crispus. Average growth rates during the dark hours ranged from 33% of average day growth rates in A. nodosum to 63% in C. crispus, respectively.  相似文献   
3.
The vertical distribution of copepods, fecal pellets and the fecal pellet production of copepods were measured at seven stations across the Southern Indian Ocean from productive areas off South Africa to oligotrophic waters off Northern Australia during October/November 2006. We quantified export of copepod fecal pellet from surface waters and how much was retained. Furthermore, the potential impact of Oncaea spp. and harpacticoid copepods on fecal pellets degradation was evaluated and found to be regional substantial. The highest copepod abundance and fecal pellet production was found in the western nutrient-rich stations close to South Africa and the lowest at the central oligotrophic stations. The in situ copepod fecal pellet production varied between 1 and 1,000 μg C m−3 day−1. At all stations, the retention of fecal pellets in the upper 400 m of the water column was more than 99% and the vertical export of fecal pellets was low (<0.02 mg m−2 day−1).  相似文献   
4.
Male crabs infected by parasitic barnacles (Rhizocephala) are known to be morphologically feminized. Here, we investigate morphological chances in green crabs, Carcinus maenas, induced by the parasitic barnacle Sacculina carcini. Infected males acquire a broader, longer and segmented abdomen, fringed with marginal setae. Copulatory appendages and pereopods are reduced in length, and the chelae become smaller. The feminization show great individual variation. Males with scars from lost externae, the parasites reproductive organ situated under the abdomen, are less modified than males carrying an externa, and the feminization is more pronounced in smaller than in larger males. No super-feminization is evident in female crabs that remain morphologically unaffected by infection. The protective value of a parasitically induced enlargement of the male abdomen may constitute an adaptation that increases parasite longevity. The additional effects on male morphology are viewed as pleiotropic side effects of the main adaptive value of enlarging the abdomen.  相似文献   
5.
6.
Employing a special batch technique which involves extremely low concentrations of the alga Selenastrum capricornutum, it is shown that a growth rate of ca. 75% of optimum growth occurs at a concentration of 0.02 g-at N(NH4 +) l-1. The low concentrations of this N-source in the oligotrophic parts of the oceans (ca. 0.06 g-at l-1) thus give rise to a borderline deficiency. As the half-saturation constant (K S) for growth was recorded at 0.05 g-at N(NO3 -), this ion can hardly be of much importance at the low concentrations present in these parts of the oceans. It is wrong to assert that N is the primary limiting nutrient. Phosphate also is found at concentrations giving rise to a borderline deficiency.  相似文献   
7.
Growth dynamics of Saccharina latissima in a Danish embayment (56°03.793N, 10°16.148E) were investigated through an annual cycle (March 1999–March 2000) and related to patterns found in previous studies covering the distribution range of the species. The kelps exhibited meristematic growth as well as distal tissue loss all year around. Elongation rate peaked in spring (March–May, 0.75 cm day?1), whereas maximum biomass growth occurred in May–July at higher insolation. S. latissima accumulated nitrogen (N) in November–March, when ambient N levels were high and the fast growth in March–July was followed by a depletion of these reserves. Light regimes and seasonal fluctuations of nutrients were, thus, major factors explaining the seasonal growth pattern of S. latissima in this temperate bay. Differences in light and exposure along depth gradients affected the growth, loss and storage product dynamics. High losses of N and carbon (C) through summer abscission of distal tissue question the efficiency of translocation, especially at shallower depths, where losses are accelerated by, e.g., high temperature. A large-scale comparison further highlighted that warming advanced the timing, increased the level of peak growth and also seemed to expand the growth period. Growth rates of the studied Danish population fell in the low end of the range for similar latitudes and temperatures, probably due to sub-optimal salinities (avg. 23.3 psu) in combination with periodically high summer temperatures (max. 21.1 °C).  相似文献   
8.
This research seeks for improved understanding regarding the interaction of meaningful work and the work–family interface. Existing literature suggests that experiencing a sense of calling toward work makes the work domain particularly salient to employees compared to other life domains. In this article, we draw on this idea, rooted in identity theory, to hypothesize that a sense of calling toward work diminishes the effects of work–family conflict and work–family enrichment on employee's job and life satisfaction. We test these ideas in two studies. First, we surveyed an alumni sample of 598 employees from various jobs, industries, and job levels. Then, in a constructive replication, we surveyed 327 employees using a time-lagged design. Calling was found to significantly buffer the effect of work–family conflict on job satisfaction in Study 2, but not Study 1. Calling did not buffer the effect of conflict on life satisfaction in either study. However, both studies demonstrated that calling attenuated (substituted for) the effect of work–family enrichment on job satisfaction. Study 1 supported the idea that calling attenuates the effect of enrichment on life satisfaction; however, this interactive effect was reversed in Study 2, contrary to expectations. We discuss implications for theory and practice related to callings and career choices, as well as for the role of calling and work identity in the work–family interface.  相似文献   
9.
The infrared spectrum of HCF2OCF2OCF2CF2OCF2H (CAS# 188690-77-9) has been re-measured. The integrated absorption intensity over the range 1000–1500 cm?1 measured in the present work is (6.65 ± 0.33) × 10?17 cm2 molecule?1 cm?1 in 700 Torr of air at 296 K. The radiative efficiency of HCF2OCF2OCF2CF2OCF2H is calculated to be 1.02 W m?2 ppb?1. The value reported in the 2007 Intergovernmental Panel on Climate Change (IPCC) report is approximately 35% larger reflecting what we believe to be an erroneously high value for the absorption strength of HCF2OCF2OCF2CF2OCF2H adopted by the IPCC.  相似文献   
10.
Floating, organic crusts on liquid manure, stored as a result of animal production, reduce emission of ammonia (NH3) and other volatile compounds during storage. The occurrence of NO2- and NO3- in the crusts indicate the presence of actively metabolizing NH3-oxidizing bacteria (AOB) which may be partly responsible for this mitigation effect. Six manure tanks with organic covers (straw and natural) were surveyed to investigate the prevalence and potential activity ofAOB and its dependence on the O2 availability in the crust matrix as studied by electrochemical profiling. Oxygen penetration varied from <1 mm in young, poorly developed natural crusts and old straw crusts, to several centimeters in the old natural crusts. The AOB were ubiquitously present in all crusts investigated, but nitrifying activity could only be detected in old natural crusts and young straw crust with high O2 availability. In old natural crusts, total potential NH3 oxidation rates were similar to reported fluxes of NH3 from slurry without surface crust. These results indicate that old, natural surface crusts may develop into a porous matrix with high O2 availability that harbors an active population of aerobic microorganisms, including AOB. The microbial activity may thus contribute to a considerable reduction of ammonia emissions from slurry tanks with well-developed crusts.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号