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   2687篇
  免费   17篇
  国内免费   33篇
安全科学   75篇
废物处理   138篇
环保管理   260篇
综合类   480篇
基础理论   550篇
环境理论   2篇
污染及防治   788篇
评价与监测   242篇
社会与环境   182篇
灾害及防治   20篇
  2023年   26篇
  2022年   86篇
  2021年   104篇
  2020年   51篇
  2019年   41篇
  2018年   98篇
  2017年   100篇
  2016年   123篇
  2015年   71篇
  2014年   114篇
  2013年   167篇
  2012年   127篇
  2011年   165篇
  2010年   113篇
  2009年   104篇
  2008年   118篇
  2007年   110篇
  2006年   74篇
  2005年   115篇
  2004年   155篇
  2003年   150篇
  2002年   96篇
  2001年   74篇
  2000年   34篇
  1999年   33篇
  1998年   14篇
  1997年   26篇
  1996年   16篇
  1995年   22篇
  1994年   17篇
  1993年   8篇
  1992年   12篇
  1991年   16篇
  1990年   9篇
  1989年   11篇
  1988年   5篇
  1987年   10篇
  1986年   8篇
  1985年   10篇
  1984年   10篇
  1983年   11篇
  1982年   5篇
  1981年   7篇
  1979年   8篇
  1977年   3篇
  1975年   3篇
  1970年   3篇
  1966年   3篇
  1964年   4篇
  1961年   3篇
排序方式: 共有2737条查询结果,搜索用时 15 毫秒
971.
Journal of Polymers and the Environment - Macadamia is a nut widely used globally in food, personal hygiene products, and human health. After removing the nut, high amounts of the shell residual,...  相似文献   
972.
微型、小型和中型企业创造了巴西的主要财富.但是这些企业却难以遵守环境法律.在这种情况下,清洁生产意义重大;它使得应用简便、廉价、持续的解决方案帮助小企业减少其环境影响、降低雇员的健康和安全风险成为可能.清洁生产战略通过把中心放在减少浪费和损耗上而改善环境条件.在实施清洁生产措施的同时,对一些措施的环境效率和经济可行性进行评估.采用最多的是良好的内务管理等简便措施.良好的内务管理包括业务参数的最优化、程序的标准化、改进买卖系统以及维护、信息和培训程序的最优化.巴西良好的内务管理战略所占的优势表明了对低成本解决方案的优先选择.  相似文献   
973.
Bite damage patterns have long been used to estimate shark species and body size, with somewhat limited success. The lack of fit between damage patterns and shark size is partially due to variation in tooth size and shape within an individual. The ability to accurately predict body size from bite patterns is important for better understanding the ecological and behavioral underpinnings of shark bites/attacks on marine organisms, humans, and submarine equipment. To this end, we measured interdental distance (IDD) between the most labial teeth in the first six tooth files on both the upper and lower jaws, as well as the circumference of the portion of each jaw that bears teeth, for prepared jaw sets from fourteen shark species and regressed these data against total length. IDD is allometric as well as an accurate predictor of total length in all species examined, except Carcharhinus acronotus. Tooth-bearing circumference is also allometric and predictive of total length in all species. Though considerable overlap exists in IDD and circumference ranges among species for the total length ranges examined, Carcharodon carcharias and Isurus sp. can be differentiated from Carcharhinus limbatus, Carcharhinus brevipinna, and C. acronotus based on these values alone. When combined with knowledge of species-specific feeding behavior, geographic distribution, and habitat preferences, these simple measures from bite damage patterns allow quick, accurate assessment of shark size and potential species.  相似文献   
974.
This essay is a trial on measuring complexity in a three-trophic level system by using a convex function of the informational entropy. The complexity measure defined here is compatible with the fact that real complexity lies between ordered and disordered states. Applying this measure to the data collected for two three-trophic level systems some hints about their organization are obtained.  相似文献   
975.
The Manila clam Ruditapes philippinarum (Adams and Reeve, 1850) is one of the mollusc species that, driven mainly by the shellfish market industry, has extended throughout the world, far beyond the limits of its original habitat. The Manila clam was introduced into France for aquaculture purposes, between 1972 and 1975. In France, this venerid culture became increasingly widespread and, since 1988, this species has colonised most of the embayments along the French Atlantic coast. In 2004, this development resulted in a fishery of ca. 520 t in Arcachon Bay.  相似文献   
976.
Statistical characterization of past fire regimes is important for both the ecology and management of fire-prone ecosystems. Survival analysis—or fire frequency analysis as it is often called in the fire literature—has increasingly been used over the last few decades to examine fire interval distributions. These distributions can be generated from a variety of sources (e.g., tree rings and stand age patterns), and analysis typically involves fitting the Weibull model. Given the widespread use of fire frequency analysis and the increasing availability of mapped fire history data, our goal has been to review and to examine some of the issues faced in applying these methods in a spatially explicit context. In particular, through a case study on the massive Cedar Fire in 2003 in southern California, we examine sensitivities of parameter estimates to the spatial resolution of sampling, point- and area-based methods for assigning sample values, current age surfaces versus historical intervals in generating distributions, and the inclusion of censored (i.e., incomplete) observations. Weibull parameter estimates were found to be roughly consistent with previous fire frequency analyses for shrublands (i.e., median age at burning of ~30–50 years and relatively low age dependency). Results indicate, however, that the inclusion or omission of censored observations can have a substantial effect on parameter estimates, far more than other decisions about specifics of sampling.
Max A. MoritzEmail:
  相似文献   
977.
The aim of this study was to evaluate the effect of a dietary highly unsaturated fatty acid (HUFA) deficiency on winter flounder Pseudopleuronectes americanus metamorphosis by examining the growth and the expression of genes involved in some key metabolic processes: lipid digestion, oxidative stress, and growth. Three groups of fish were fed rotifers enriched with different blends of microalgae providing different HUFA profiles: (1) a diet comprising a mixture of three microalgae, Nannochloropsis oculata, Isochrysis galbana, and Pavlova lutheri (Cocktail diet), which contained a balanced combination of ecosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid (AA); (2) the N. oculata diet (Nanno diet), with a low level of DHA; and (3) the I. galbana diet (Tiso diet), characterized by low levels of EPA and AA. The results indicate that the need for DHA increased from settlement and for EPA and AA from 15 days after settlement. The lower HUFA content in the Tiso and Nanno diets did not affect larval development or lipid reserve accumulation. The superoxide dismutase gene expression suggests a reduced oxidative stress in the Cocktail group, and overall results indicate that gh gene expression could be a valuable indicator of development at the molecular level in response to dietary HUFA quality during metamorphosis in winter flounder.  相似文献   
978.
Thermal stratification is increasing in strength as a result of higher surface water temperature. This could influence the vertical distribution of vertically migrating dinoflagellates. We studied the diel vertical distribution of the dinoflagellates Heterocapsa triquetra and Prorocentrum minimum using stratified laboratory columns with two thermoclines of different strength (ΔT° = 10 or 17 °C), with below cline temperature of 8 °C. Above the thermocline, nutrient depletion simulated the natural summer conditions in the Baltic Sea. Our study shows that H. triquetra and P. minimum can behave differently in terms of their vertical occurrence, both in space and in time when subjected to thermoclines of different strength. Also, both dinoflagellate species showed species-specific distribution patterns. In the ΔT° = 10 °C treatment, H. triquetra cells performed a diel vertical migration (DVM) behavior just above the thermocline, but not in the ΔT° = 17 °C. In the ΔT° = 17 °C, the cells did not migrate and cell densities in the water column decreased over time. Opposing results were observed for P. minimum, where a DVM pattern was found exclusively below the thermocline of ΔT° = 17 °C, while in the ΔT° = 10 °C treatment, no clear DVM pattern was observed, and the highest number of cells were found in the cold bottom water. These results indicate that an increase in thermal stratification can influence species-specific dinoflagellate distribution, behavior, and survival.  相似文献   
979.
Most migrating birds alternate flight bouts with stopovers, during which they rest and replenish the fuel used during flight (refueling). The rate of refueling (fuel deposition rate, FDR) affects stopover duration, and hence is an important determinant of the overall time required for migration. Although environmental and endogenous factors affect FDR, the urge to refuel depends on the anticipated distance to be travelled and possibly also on the amount of fuel used during the flight preceding stopover. Combining a field study with a fasting–refueling experiment on long-term captive songbirds, we tested whether the extent of fuel loss prior to refueling indeed affects FDR. In the field study, we took a comparative approach and determined FDR in two subspecies of northern wheatear (Oenanthe oenanthe) that differ greatly in the distance flown, and thus the extent of fuel used to reach our study (stopover) site. As both winter in western sub-Sahelian Africa, they face the same remaining migration distance. We found that FDR was higher in the subspecies that uses more fuel to get to our study site. Solidifying this result, in the experiment on captive northern wheatears, we found that the extent of fuel loss as a consequence of fasting explained most of the variation in subsequent FDR. The observation that experimental birds losing little fuel did not maximize their FDR suggests there are costs to rapid refueling. Our study shows that FDR is shaped not just by current environmental and endogenous conditions but also by fuel loss prior to refueling.  相似文献   
980.
Environmental Chemistry Letters - A broad variety of materials of biological origin have been successfully used in recent decades for the removal of pollutants from waters. These biosorbents...  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