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野骆驼是世界上骆驼科真驼属唯存的野生种,目前全世界只分布在我国新疆和蒙古国的中蒙边境地区,在世界上仅存730~880头左右,是比大熊猫更为珍稀的野生动物,濒临灭绝。野骆驼的生存环境非常恶劣,气候十分干旱,荒漠化十分严重,蒸发量远远大于降雨量,空气非常干燥,日夜温差极大。分布区的植物也非常稀少,没有淡水,只有零星散布的又苦又咸的盐泉,大部分地区寸草不生,只有在盐泉附近长着稀稀拉拉的盐生草、沙拐枣、骆驼刺等。野骆驼能在严酷的荒漠半荒漠地区生活,对恶劣气候环境有很强的适应性,具有耐饥渴抗风暴等抵抗恶劣环境的能力,是动物界中任何一种动物无可比拟的。 相似文献
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The increasing pace and scale of landscape changes involve objective measurements in order to estimate the effects of changes on people's landscape preferences in a meaningful way. In the literature, some attempts have been made to provide a more conceptual base related to landscape preferences. These concepts and their indicators need to be tested empirically in different contexts and landscape types. In the present study, different items related to theoretical concepts of both aesthetic preference and cognitive rating were examined. They were combined in an in situ questionnaire, which was conducted among undergraduate students in geography during two different field excursions. Stimuli consisted of 11 landscape vistas selected during the excursions. All vistas represent rather rural landscapes but they vary with regard to relief, degree of urbanisation, and degree of agricultural land use. Statistical analysis of all data yielded significant correlations between aesthetic and cognitive ratings. However, these correlations did not appear to be very strong. When considering landscape vistas separately, the relations between all cognitive ratings seemed to vary. Further, not all cognitive aspects had an equal predicting value for aesthetic preference. Moreover, this predicting value appeared to vary between different landscape vistas. The groups of interrelated cognitive aspects could not be associated consistently with theoretical concepts. The results demonstrated the inconsistencies existing between the contents of the theoretical concepts and the indicators found within the landscape. The findings argued for the necessity to distinguish between different ratings and landscape types instead of using unitary preference measures and generalized data when studying landscape preference. 相似文献
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The long-term water quality monitoring program implemented by the Massachusetts Water Resources Authority in 1992 is extensive
and has provide substantial understanding of the seasonality of the waters in both Boston Harbor and Massachusetts Bay and
the response to improvements in effluent quality and offshore transfer of the effluent in September 2000. The monitoring program
was designed with limited knowledge of spatial and temporal variability and long-term trends within the system. This led to
an extensive spatial and temporal sampling program. The data through 2003 showed high correlation within physical parameters
measured (e.g., salinity, dissolved oxygen) and in biological measures such as chlorophyll fluorescence. To address the potential
sampling redundancies in the measurement program, an assessment of the impact of reduced levels of monitoring on the ability
to make water quality decisions was completed. The optimization was conducted by applying statistical models that took into
account whether there was evidence of a seasonal pattern in the data. The optimization used model survey average readings
to identify temporal fixed effects, model survey-average-corrected individual station readings to identify spatial fixed effects,
corrected the individual station readings for temporal and spatial fixed effects and derived a correlation model for the corrected
data, and applied the correlation model to characterize the correlation of annual average readings from reduced monitoring
programs with true parameter levels. Reductions in the number of sampling stations were found less detrimental to the quality
of the data for annual decision-making than reductions in the number of surveys per year, although there is less of a difference
in this regard for dissolved oxygen than there is for chlorophyll. The analysis led to recommendations for a substantially
lower monitoring effort with minimal loss of information. The recommendation supported an annual budget savings of approximately
$183,000. Most of the savings was from fewer surveys as approximately $21,000 came from the reduction in the number of stations
monitored from 21 to 7 and associated laboratory analytical costs. 相似文献
27.
Artificial neural network based carbon monoxide persistence models for episodic urban air quality management 总被引:1,自引:0,他引:1
This paper describes the development of artificial neural network (ANN) based carbon monoxide (CO) persistence (ANNCOP) models
to forecast 8-h average CO concentration using 1-h maximum predicted CO data for the critical (winter) period (November–March).
The models have been developed for three 8-h groupings of 10 p.m. to 6 a.m., 6 a.m. to 2 p.m. and 2–10 p.m., at two air quality control regions (AQCRs) in Delhi city, representing an urban intersection and an arterial road consisting
heterogeneous traffic flows. The result indicates that time grouping of 2–10 pm is dominantly affected by inversion conditions and peak traffic flow. The ANNCOP model corresponding to this grouping predicts
the 8-h average CO concentrations within the accuracy range of 68–71%. The CO persistence values derived from ANNCOP model
are comparable with the persistence values as suggested by the Environmental Protection Agency (EPA), USA. This work demonstrates
that ANN based model is capable of describing winter period CO persistence phenomena. 相似文献
28.
固体废物排放统计对象应覆盖固体废物从原材料到最终处置的整个生命周期的各个环节(机构),即矿业--加工制造业--产品流通领域--用户--固体废物收运体系--固体废物中间处理厂--固体废物最终处置场.统计指标体系包括固体废物排放统计指标和排放管理指标;统计指标区分为指标、主要参数和辅助参数,既便于理解也便于管理.根据固体废物排放量和已知的固体废物资源化技术,对固体废物重新分类、统计并分类填埋,以便将来实现再利用.固体废物排放控制统计的对象主要是规模以上的污染源,实施统计的污染源的规模应当是全国统一的. 相似文献
29.
新形势下对环境统计工作的思考 总被引:1,自引:0,他引:1
分析了环境统计工作的定位和内容,以及第二次全国污染源普查、排污许可证与排污税制度、环境质量考核制度给环境统计工作带来的改革契机。针对固定源、城镇生活源与农业面源、移动源,提出了统计调查工作的设想。建议改变环境统计调查焦点,实现污染源统计空间格局"一张图";开拓环境统计分析品牌,推动环境统计方法研究;以政策管理需求为导向,完成环境统计工作体系的重构。 相似文献
30.
Standard procedures for evaluating environmental impact involve comparison between before and after conditions or scenarios
or between treatment and control site pairs. In many cases, however, endogenous directional change (natural succession) is
expected to occur at a significant rate over the period of concern, particularly for manmade systems such as impoundments.
Static evaluations do not provide an adequate approach to such problems. A new evaluation frame is proposed. Nominal system
behavior over time is characterized by a stochastic envelope around a nominal trajectory. We show that both the state variance
and the sampling variance can change over time. In this context, environmental regulations can be framed as constraints, targets,
or conformance to ideal trajectories. Statistical tests for determining noncompliance are explored relative to process variance,
sample error, and sample size. Criteria are elucidated for choosing properties to monitor, sample size, and sampling interval. 相似文献