全文获取类型
收费全文 | 788篇 |
免费 | 92篇 |
国内免费 | 107篇 |
专业分类
安全科学 | 271篇 |
废物处理 | 18篇 |
环保管理 | 76篇 |
综合类 | 352篇 |
基础理论 | 92篇 |
污染及防治 | 70篇 |
评价与监测 | 80篇 |
社会与环境 | 9篇 |
灾害及防治 | 19篇 |
出版年
2024年 | 3篇 |
2023年 | 21篇 |
2022年 | 40篇 |
2021年 | 38篇 |
2020年 | 50篇 |
2019年 | 40篇 |
2018年 | 23篇 |
2017年 | 36篇 |
2016年 | 32篇 |
2015年 | 40篇 |
2014年 | 45篇 |
2013年 | 50篇 |
2012年 | 62篇 |
2011年 | 61篇 |
2010年 | 36篇 |
2009年 | 39篇 |
2008年 | 47篇 |
2007年 | 51篇 |
2006年 | 37篇 |
2005年 | 35篇 |
2004年 | 25篇 |
2003年 | 29篇 |
2002年 | 20篇 |
2001年 | 18篇 |
2000年 | 11篇 |
1999年 | 10篇 |
1998年 | 18篇 |
1997年 | 11篇 |
1996年 | 13篇 |
1995年 | 10篇 |
1994年 | 8篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1972年 | 1篇 |
排序方式: 共有987条查询结果,搜索用时 0 毫秒
421.
This study investigated the effects of multiple cognitive tasks on human performance. Twenty-four students at North Carolina A&;T State University participated in the study. The primary task was auditory signal change perception and the secondary task was a computational task. Results showed that participants' performance in a single task was statistically significantly different from their performance in combined tasks: (a) algebra problems (algebra problem primary and auditory perception secondary); (b) auditory perception tasks (auditory perception primary and algebra problems secondary); and (c) mean false-alarm score in auditory perception (auditory detection primary and algebra problems secondary). Using signal detection theory (SDT), participants' performance measured in terms of sensitivity was calculated as ?0.54 for combined tasks (algebra problems the primary task) and ?0.53 auditory perceptions the primary task. During auditory perception tasks alone, SDT was found to be 2.51. Performance was 83% in a single task compared to 17% when combined tasks. 相似文献
422.
423.
Earlier studies on fault diagnosis of the pipeline and pump unit systems (PPU) relied mainly on independent equipment analyses, which usually lead to false alarms because of the loss of information fusion. The aim of this study is to utilize the status coupling relationship to improve fault detection sensitivity and reduce false alarm rate. A real-time status identification of related equipment step is added between capturing abnormal signals and listing out diagnosis results. For example, when the pipeline pressure fluctuation is found abnormal, a status analysis of pump units is performed immediately, if the pump units are proven to be operational normally, then the pipeline leak alarm is acknowledged valid. The logical reasoning algorithm is used to capture abnormal conditions of pipeline pressures. The pump unit faults are captured by combining information from multiple sources. Field applications show that the proposed method significantly improves the PPU fault detection capability on fault detection sensitive and accuracy. 相似文献
424.
通过开展真实火灾实验和数值模拟研究,考察隧道内温度变化情况,对比分析不同高度的分布式感温光纤对温升或温差的响应规律,进一步研究光纤敷设间隔与隧道高度的关系。结果表明,光纤敷设的最大间隔应随着隧道高度的增加而逐渐减小。最后,对照国内各地方标准及其他国家的标准规定,得到不同敷设高度感温光纤对应的最优光纤敷设间距。该研究结果对分布式光纤火灾探测系统的实际应用有一定指导作用。 相似文献
425.
This paper presents an effective decision making system for leak detection based on multiple generalized linear models and clustering techniques. The training data for the proposed decision system is obtained by setting up an experimental pipeline fully operational distribution system. The system is also equipped with data logging for three variables; namely, inlet pressure, outlet pressure, and outlet flow. The experimental setup is designed such that multi-operational conditions of the distribution system, including multi pressure and multi flow can be obtained. We then statistically tested and showed that pressure and flow variables can be used as signature of leak under the designed multi-operational conditions. It is then shown that the detection of leakages based on the training and testing of the proposed multi model decision system with pre data clustering, under multi operational conditions produces better recognition rates in comparison to the training based on the single model approach. This decision system is then equipped with the estimation of confidence limits and a method is proposed for using these confidence limits for obtaining more robust leakage recognition results. 相似文献
426.
427.
428.
429.
430.
Jaroslav Pochop Miroslava Kačániová Lukáš Hleba Jadža Lejková Martina Fikselová Simona Kunová 《Journal of environmental science and health. Part. B》2013,48(8):697-702
The aim of this study was to follow contamination of ready to eat milk and meat products with Salmonella spp. by using the StepOne real-time polymerase chain reaction (PCR). Classical microbiological methods for detection of foodborne bacteria involve the use of pre-enrichment and/or specific enrichment, following isolation of bacteria in solid media and the final confirmation by biochemical and/or serological tests. We used the PrepSEQ Rapid Spin Sample Preparation Kit for isolation of DNA and MicroSEQ® Salmonella spp. Detection Kit for pursuance of the real-time PCR (Applied Biosystems). In samples without incubation we detected strain of Salmonella sp. in 5 out of 25 samples (swabs), as well as in the internal positive control (IPC), which was positive in all samples. This StepOne real-time PCR assay is extremely useful for any laboratory equipped by real-time PCR. It is a fast, reproducible, simple, specific and sensitive way to detect nucleic acids, which could be used in clinical diagnostic tests in the future. Our results indicated that real-time PCR assay developed in this study could sensitively detect Salmonella spp. in ready-to-eat food. This could prevent infection caused by Salmonella, and also could benefit food manufacturing companies by extending their product's shelf-life as well as saving the cost of warehousing their food products while awaiting pathogen testing results. 相似文献