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991.
Spencer A. Peterson David P. Larsen Steven G. Paulsen N. Scott Urquhart 《Environmental management》1998,22(5):789-801
N = 11,076). Results were compared to a large, nonrandomly sampled data set for the same area compiled by Rohm and others and
contrasted with lake trophic state information published in the National Water Quality Inventory: 1994 Report to Congress
[305(b) report. Lakes across the entire Northeast were identified by EMAP data as 37.9% (±8.4%) oligotrophic, 40.1% (±9.7%)
mesotrophic, 12.6% (±7.9%) eutrophic, and 9.3% (±6.3%) hypereutrophic. Lakes in the ADI and NEU generally are at a low, nearly
identical trophic state (96% oligotrophic/mesotrophic), while those in the CLP are much richer (45% eutrophic). EMAP results
are similar to results of the Rohm data set across the entire region. In the CLP, however, EMAP identified approximately 45%
of the lakes as eutrophic/hypereutrophic, while the Rohm data set identified only 21% in these categories. Across the entire
Northeast, the 305(b) report identified a much higher proportion (32.2%) of lakes in eutrophic condition and a much smaller
proportion (19.8%) in oligotrophic condition than did the EMAP survey data (12.5% ± 7.9% and 37.9% ± 8.5%, respectively).
Probability sampling has several advantages over nonrandom sampling when regional resource condition assessment is the goal. 相似文献
992.
The relationship between long-term dynamics of reproductive parameters and body condition were studied in female water voles from a cycling population. Body condition was estimated from the deviation of body weight (excluding the weight of the uterus with embryos) from the theoretically expected weight calculated from the equation of body weight regression with respect to body length. As the index of body condition increases upon transition from decline to peak in the population cycle, the numbers of corpora lutea and live embryos also increase and the risk of resorption of the entire litter becomes lower. 相似文献
993.
通过对冷原子荧光法测定水中汞的实验条件的探讨,指出水样在采集,保存,所用实验容器,实验试剂,实验预处理,仪器使用等方面应注意的问题,从而保证实验结果的准确性,可靠性。 相似文献
994.
995.
Joshua J. Traylor Ray T. Alisauskas F. Patrick Kehoe 《Behavioral ecology and sociobiology》2008,62(7):1085-1097
Young waterfowl can frequently join foster females shortly after hatch, resulting in post-hatch brood amalgamation. Much uncertainty
remains about physiological or ecological factors that motivate adoption including potential costs and benefits to fostered
offspring as well as to females that either lose or accept young. Several hypotheses have been put forth to explain adoption.
In this paper, we examine the salvage strategy (SSH) and accidental-mixing (AMH) hypotheses. According to the SSH, females
abandon or lose their young due to substantial energetic constraints from incubation and brood rearing. The AMH posits that
adoption results from local ecological conditions on breeding areas (i.e., adverse weather conditions, high brood densities)
which act to separate offspring and mothers. We used multistate modeling to estimate relationships between probabilities of
adoption by white-winged scoter (Melanitta fusca) ducklings from natal to foster females and a set of hypothesized ecological covariates. Results showed that most adoption
occurred within 6 days of hatch; additionally, likelihood of adoption was positively related to inclement weather and negatively
related to hatch date, size, and condition of natal females, and duckling condition. We conclude that adoption in this population
is consistent with both the salvage strategy and accidental-mixing hypotheses. Ultimately, we suggest that adoption in our
study population was foremost an outcome of intense gull predation but also of local environmental conditions. 相似文献
996.
997.
谢琼中 《湖南环境生物职业技术学院学报》2014,(2):7-10
通过对湖南省绥宁县黄桑自然保护区的植物群落特征及物种多样性的分析,结果表明:1)可将黄桑自然保护区的滩地、撂荒地和山坡地划分为3种群落类型:鱼腥草-蕨群丛、早熟禾-井栏边草群丛和杉木+马尾松-三尖杉+水苏-莎草+地稔群丛;2)植物多样性指数的大小顺序为:Patrick丰富度指数(R)、Simpson指数(D)和ShannonWiener指数(H)的大小顺序为:山坡地(S,D,H)撂荒地(S,D,H)滩地(S,D,H),Pielou均匀度指数(E)的大小顺序为:潍地(E)撂荒地(E)山坡地(E);3)3种样地之间的物种Czekanowski相似性系数(CC)较低,在0.0001~0.356 8之间,样地内的物种相似性指数(CC)沿滩地→撂荒地→山坡地的顺序递减;(4)相关分析表明:S、D、H之间呈极显著正相关(P0.01),E与S、D、H呈显著负相关(P0.05).生境条件差异是物种多样性差异形成的直接原因.表3,参16. 相似文献
998.
通过对机场运行安全规划中安全指标体系定位的分析,遵循可接受、可实施、可量化、可调控的原则,以结果和过程管理思想为指导,结合风险管理理论,构建机场运行安全规划中的安全指标体系。这个体系包括3个子体系,它们分别涉及运行安全的结果、运行安全的业务过程和运行安全管理绩效3个方面。其中,有关运行安全结果的子指标体系包括事故、事故征候、其他不安全事件3个维度11项指标;有关运行安全业务过程的子指标体系包括飞行区管理、机坪运行管理等7个维度20项指标;有关安全管理绩效的子指标体系包括安全政策与目标、风险管理等4个维度7项指标。 相似文献
999.
高效絮凝剂产生菌的筛选及培养条件 总被引:2,自引:0,他引:2
从活性污泥中分离出36株菌株,培养、筛选得到具有絮凝活性的菌株9株,其中有一株絮凝活性较高,命名为B-8,同时考察了培养时间、温度、pH和碳源对絮凝效果的影响。结果表明,培养时间72h,最佳温度为37℃,pH为7.0,葡萄糖为最佳碳源时,该微生物所产生的絮凝剂的絮凝效果最好,絮凝率可达95.75%。 相似文献
1000.
城市大型停车场的数量随着经济的发展在迅速增长,这些新建的停车场均向高层和地下空间发展,其投资费用都较大,一旦发生火灾,往往会造成严重的经济损失和人员伤亡事故,国内外停车场发生的一系列火灾事故充分证明了这一点.因此,对停车场进行火灾风险评价具有十分重要的意义.分析了停车场火灾的特点,并从停车场的火灾场景、发生轰燃的烟气条件、释放辐射热的大小、对面汽车被引燃的临界条件等几方面对停车场潜在的火灾风险性进行了探讨.以某地下停车场为例,对其火灾风险性进行了具体评价. 相似文献