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   25902篇
  免费   238篇
  国内免费   161篇
安全科学   582篇
废物处理   1065篇
环保管理   3321篇
综合类   4335篇
基础理论   6909篇
环境理论   13篇
污染及防治   5809篇
评价与监测   1775篇
社会与环境   2341篇
灾害及防治   151篇
  2022年   181篇
  2021年   196篇
  2020年   137篇
  2019年   184篇
  2018年   766篇
  2017年   775篇
  2016年   866篇
  2015年   416篇
  2014年   565篇
  2013年   1788篇
  2012年   846篇
  2011年   1517篇
  2010年   1051篇
  2009年   1155篇
  2008年   1407篇
  2007年   1668篇
  2006年   868篇
  2005年   776篇
  2004年   730篇
  2003年   782篇
  2002年   741篇
  2001年   752篇
  2000年   594篇
  1999年   323篇
  1998年   274篇
  1997年   253篇
  1996年   255篇
  1995年   284篇
  1994年   265篇
  1993年   255篇
  1992年   260篇
  1991年   252篇
  1990年   266篇
  1989年   223篇
  1988年   186篇
  1987年   166篇
  1986年   195篇
  1985年   192篇
  1984年   210篇
  1983年   190篇
  1982年   198篇
  1981年   194篇
  1980年   188篇
  1979年   185篇
  1978年   129篇
  1977年   145篇
  1974年   133篇
  1973年   121篇
  1972年   140篇
  1971年   110篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
171.
Laser-induced breakdown spectroscopy (LIBS) is a laser-based optical technique particularly suited for in situ surface analysis. A portable LIBS instrument was tested to detect surface chemical contamination by chemical warfare agents (CWAs). Test of detection of surface contamination was carried out in a toxlab facility with four CWAs, sarin (GB), lewisite (L1), mustard gas (HD), and VX, which were deposited on different substrates, wood, concrete, military green paint, gloves, and ceramic. The CWAs were detected by means of the detection of atomic markers (As, P, F, Cl, and S). The LIBS instrument can give a direct response in terms of detection thanks to an integrated interface for non-expert users or so called end-users. We have evaluated the capability of automatic detection of the selected CWAs. The sensitivity of our portable LIBS instrument was confirmed for the detection of a CWA at surface concentrations above 15 μg/cm2. The simultaneous detection of two markers may lead to a decrease of the number of false positive.  相似文献   
172.
The population of foxes in the central regions of Yakutia has grown by a factor of four to five during the period from 2000 to 2011–2012, following an increase in the abundance of voles from the genus Microtus. A total of 130 carcasses of foxes taken in 2007–2012 have been examined. Age- and sex-related variation in morphological features has been described. The demographic structure of the population has been studied by estimating animal age from annual layers in the recording structures. Changes in female fertility and involvement in reproduction depending on age and feeding conditions have been analyzed. Changes in the composition of fox diet caused by long-term population depression in the mountain hare and their effect on the dynamics of fox abundance have been revealed. Age- and sex-related characteristics of the condition factor in foxes and sex-related differences in their dietary preferences have been demonstrated.  相似文献   
173.
The spatial structure of 10 populations of rare orchid species (Dactylorhiza incarnata, D. traunsteineri, Listera ovata) has been studied in rich fens sporadically occurring in Murmansk oblast. Two levels of plant aggregation within populations have been distinguished: (1) clusters of individuals and (2) isolated population subsets consisting of clusters. General spatial demographic features of orchid populations in the fens are small area (77 m2) and low ecological density (0.009 ind./m2). Characteristics of the population subsets (their number, area, composition, and distance to the neighboring subset) are species-specific and reflect the degree of species rarity in plant communities.  相似文献   
174.
The role of ecotones with different (sharp or smooth) spatial boundaries between forest and meadow in ant biodiversity preservation was studied at the right-of-way of a power line in the Voronezh Reserve. The ecotone with a sharp boundary between forest and meadow (transitional zone 2 m wide) had higher species richness of ants compared to the ecotones (also 2 m wide) with smooth boundary between forest and meadow.  相似文献   
175.
The probable source of stone moroko, Pseudorasbora parva (Temminck & Schlegel, 1846), populations in lake- and stream-type Dnieper reservoirs was revealed. The dynamics and specific growth rates of these populations over 20 years were analyzed. The dynamic phase portrait method was used to determine the timing of stages in the process of invader naturalization and the periods when its populations were in equilibrium. The potential growth rates of P. parva populations in the Kremenchug and Dneprodzerzhinsk reservoirs were estimated.  相似文献   
176.
The sustainability of deltas worldwide is under threat due to the consequences of global environmental change (including climate change) and human interventions in deltaic landscapes. Understanding these systems is becoming increasingly important to assess threats to and opportunities for long-term sustainable development. Here, we propose a simplified, yet inclusive social–ecological system (SES)-centered risk and vulnerability framework and a list of indicators proven to be useful in past delta assessments. In total, 236 indicators were identified through a structured review of peer-reviewed literature performed for three globally relevant deltas—the Mekong, the Ganges–Brahmaputra–Meghna and the Amazon. These are meant to serve as a preliminary “library” of potential indicators to be used for future vulnerability assessments. Based on the reviewed studies, we identified disparities in the availability of indicators to populate some of the vulnerability domains of the proposed framework, as comprehensive social–ecological assessments were seldom implemented in the past. Even in assessments explicitly aiming to capture both the social and the ecological system, there were many more indicators for social susceptibility and coping/adaptive capacities as compared to those relevant for characterizing ecosystem susceptibility or robustness. Moreover, there is a lack of multi-hazard approaches accounting for the specific vulnerability profile of sub-delta areas. We advocate for more comprehensive, truly social–ecological assessments which respond to multi-hazard settings and recognize within-delta differences in vulnerability and risk. Such assessments could make use of the proposed framework and list of indicators as a starting point and amend it with new indicators that would allow capturing the complexity as well as the multi-hazard exposure in a typical delta SES.  相似文献   
177.
Patterns of expansion of geographical ranges of red deer and Siberian roe deer in Yakutia during the 20th century are considered. The area inhabited by red deer in Yakutia has increased almost fourfold over the past 50 years, with an expansion of over 200000 km2 toward the northwest. The geographical range of roe deer in the Lena–Amga interfluve has also changed considerably during the same period. Roe deer sightings in the subarctic zone were reported. The structure of geographical ranges of the species under investigation in different ecological and geographical regions of Yakutia is discussed, and the factors influencing the transformation of geographical range borders are characterized.  相似文献   
178.
An analysis is made of the spatial variability of snowmelt water composition (within and between biogeocenoses), with regard to its long-term dynamics, in pine and spruce forests exposed to airborne industrial pollution from the Europe’s largest Severonikel Copper–Nickel Smelter Complex. Snowmelt waters from under the tree canopy, compared to those from intercrown areas, contain higher concentrations of chemical elements due to their washing and leaching from tree crowns. This is especially true of spruce forests, since the crowns of spruce trees have a high sorption capacity. Distinct trends in the long-term dynamics of snowmelt water composition, related to reduction of industrial emissions, are observed in background forest areas and defoliating forests but not in the vicinity of pollution sources. It is shown that the main factors determining these dynamics in forests of the Kola Peninsula are edificator tree species, airborne industrial pollution, and, possibly, an increase in the number of days with above-zero temperatures in the period of snow accumulation, which facilitates washing and leaching of chemical compounds from tree crowns.  相似文献   
179.
In case of an avian-influenza-derived human flu pandemic, an inordinately high use of medicines over several weeks is predicted, in particular for the recommended influenza antiviral oseltamivir (Tamiflu). While the risk of oseltamivir to sewage works and freshwater bodies has already been assessed, the fact that a large percentage of the human population worldwide lives relatively close to the sea raises concern for its environmental compatibility in coastal marine waters. The potential risk of high oseltamivir use to the marine compartment is assessed in this publication, based on the 2003 European Community Technical Guidance Document (TGD) for risk assessment. Subchronic embryo–larval ecotoxicity tests with three marine invertebrates (Pomatoceros triqueter, Annelida; Mytilus edulis, Mollusca; Paracentrotus lividus, Echinodermata) and chronic growth inhibition tests with two different groups of marine microalgae (Isochrysis galbana, Haptophyta; Skeletonema costatum, Heterokontophyta) were performed with the active substance oseltamivir carboxylic acid to derive a dependable marine predicted no-effect concentration (PNEC). This was compared to a predicted environmental concentration (PEC) for oseltamivir in coastal waters, based on the worst-case freshwater PEC. The PEC/PNEC risk characterisation ratio for the marine compartment is well below 1, which in the terminology of the TGD signifies no immediate concern. Further, while oseltamivir may be persistent (P), it is not bioaccumulative (B) nor highly ecotoxic (T) and therefore not a PBT substance. In conclusion, even a high pandemic use of oseltamivir would not lead to a significant risk for the marine compartment, in confirmation of the risk assessment for sewage works and freshwaters.  相似文献   
180.
The very significant impact of European legislation (Directive 91/414/EEC) on the authorization of plant protection products is reviewed herein, which has resulted in withdrawal of 704 active substances (AS) out of 889 assessed so far. The list of currently approved 276 AS includes 194 AS “existing” in the market before 1993 and 82 “new” AS introduced during the last 15 years. Results of toxicity characterization of the approved AS are also summarized, utilizing several well-known databases. Although significant data gaps exist for a rather large part of the approved AS, it is found that 84 AS are positive for at least one health effect (after chronic and/or acute exposure) including carcinogenicity, reproductive and neuro-developmental disorders, as well as endocrine disruption. The toxicity characterization results of this study are compared to those of recent assessments by other organizations (KemI, the Swedish Chemicals Agency, and the Pesticide Safety Directorate of the UK), where interpretation and use is made of AS “cut-off” criteria foreseen in new EU legislation. These studies report a comparatively smaller AS number with positive toxicity characterization. The possibility of some additional AS withdrawal in the near future, combined with the rather small rate of new AS introduction (approx. 5 per year) suggest that the list of approved AS over the next 10–15 years may not change very drastically. Consideration of the above trends is necessary and instructive in evaluating results of existing health impact assessment (HIA) studies, as well as in planning new ones. Due to the very drastic change in the number and type of marketed AS, that took place within the past 8–9 years, it is suggested that new HIA studies (based on epidemiological data after year 2000) should focus on a rather short time frame and, therefore, on appropriate cohort groups, e.g. young children. For the same reason, results of epidemiological studies of the past (involving banned AS) should be carefully interpreted and used with caution.  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