全文获取类型
收费全文 | 204篇 |
免费 | 23篇 |
国内免费 | 72篇 |
专业分类
安全科学 | 17篇 |
废物处理 | 11篇 |
环保管理 | 37篇 |
综合类 | 149篇 |
基础理论 | 26篇 |
污染及防治 | 18篇 |
评价与监测 | 4篇 |
社会与环境 | 35篇 |
灾害及防治 | 2篇 |
出版年
2024年 | 1篇 |
2023年 | 7篇 |
2022年 | 10篇 |
2021年 | 7篇 |
2020年 | 7篇 |
2019年 | 13篇 |
2018年 | 6篇 |
2017年 | 10篇 |
2016年 | 19篇 |
2015年 | 14篇 |
2014年 | 14篇 |
2013年 | 21篇 |
2012年 | 12篇 |
2011年 | 20篇 |
2010年 | 11篇 |
2009年 | 9篇 |
2008年 | 6篇 |
2007年 | 25篇 |
2006年 | 15篇 |
2005年 | 12篇 |
2004年 | 6篇 |
2003年 | 11篇 |
2002年 | 6篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1983年 | 1篇 |
1977年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有299条查询结果,搜索用时 15 毫秒
161.
Effects of cultivation conditions on the diversity of microbes involved in the conversion of rice straw to fodder 总被引:1,自引:0,他引:1
To confirm the optimum cultivation conditions for analyzing lactic acid bacterial communities and to provide the cultivation foundation for lactic acid bacterial communities that were used to convert straw into fodder, fermented rice straw was inoculated into 13 different broths. After 48 h of cultivation, pH values, volatile products, and microbial diversity were analyzed. Except for LAB broth, the pH values of the other broths could decrease to approximately 4.5. GC/MS analysis showed that lactic acid in Tomato MRS broth, MRS broth, LAB broth, and Tomato juice broth was higher than that in the other broths. DNA concentration analysis showed that the counts of microbes in Tomato MRS broth were 2.5 times of those in other broths and that tomato juice favored the reproduction of the microbes. Denaturing gradient gel electrophoresis (DGGE) analysis showed that the number of lactic acid bacterial species in HYA broth, Tomato juice broth, and Tomato MRS broth were higher than those in the other broths. 相似文献
162.
A study was conducted to compare the diversity of 2-, 3-, and 4-chlorobenzoate degraders in two pristine soils and one contaminated sewage sludge. These samples contained strikingly different populations of mono-chlorobenzoate degraders. Although fewer cultures were isolated in the uncontaminated soils than contaminated one, the ability of microbial populations to mineralize chlorobenzoate was widespread. The 3- and 4-chlorobenzoate degraders were more diverse than the 2-chlorobenzoate degraders. One of the strains isolated from the sewage sludge was obtained. Based on its phenotype, chemotaxonomic properties and 16S rRNA gene, the organism S-7 was classified as Rhodococcus erythropolis. The strain can grow at temperature from 4 to 37℃. It can utilize several (halo)aromatic compounds. Moreover, strain S-7 can grow and use 3-chlorobenzoate as sole carbon source in a temperatures range of 10-30℃ with stoichiometric release of chloride ions. The psychrotolerant ability was significant for bioremediation in low temperature regions. Catechol and chlorocatechol 1,2-dioxygenase activities were present in cell free extracts of the strain, but no (chloro)catechol 2,3- dioxygenase activities was detected. Spectral conversion assays with extracts from R. erythropolis S-7 showed accumulation of a compound with a similar UV spectrum as chloro-cis,cis-muconate from 3-chlorobenzoate. On the basis of these results, we proposed that S-7 degraded 3-chlorobenzoate through the modified ortho-cleave pathway. 相似文献
163.
164.
气相化学反应中的云盖效应 总被引:7,自引:0,他引:7
本文在CBM-I机理的基础上考虑了OH和HO2自由基对SO2的氧化作用和云对光解率的影响,定量研究了气相色化学反应中的云盖效应。结果表明,云的存在将改变整个反应体系的平衡,气态物对云的响应是非线的。 相似文献
165.
西部地区生态退耕的"效益问题"及其评价方法探讨 总被引:11,自引:2,他引:11
在剖析了西部地区退耕还林还草生态效益、经济效益和社会效益内涵的基础上.指出退耕还林还草项目首先追求的是较好的生态效益,并在此前提下要求尽量做到社会效益和经济效益的协调统一。目前评价退耕效益可采用以下两种思路:生态效益经济价值化法与综合评价法。生态效益经济价值化,可以从国民经济的角度考察退耕还林还草的投资成本和获得的情况,为国家制定宏观政策提供客观依据。按照综合评价法获得的结果,则能为退耕前选择退耕预案、退耕过程中及时发现问题和调整政策以及退耕后进行实施成效评价提供参考。 相似文献
166.
中国东南沿海风能资源评价 总被引:4,自引:1,他引:4
本文选取322个气象台站(自记158个,非自记174个)10年(1971—1980)风速资料统计计算了3.5—20.4m/s有效风速出现的小时数,年(月)风能和风能密度,风速、风能变化规律;绘制了年有效风能和有效风速频率分布图,进而按风能资源分布规律做出风能区划及风能的高度变化。其次,结合实际风能资料,阐明风能与风力机输出能量转换关系,从而测算出该地区农田灌溉和风力发电的风能资源利用转换值。最后,根据当地实际风能资源、环境、地形及地下水位高低,为选择合理的设计风速或引进适合当地的风力机以及解决当地部分能源提供合理化建议和对该区发展风力机的前景提出了看法。实践证明具有一定的实际应用价值。 相似文献
167.
目前我国已发布实施了一些新烟度排放、测量和仪器标准,并规定烟度符号采用SF,烟度单位为FSN。但由于尚未发布实施新的标准烟度卡,而仍然使用旧的标准烟度卡(烟度值为Rb),因此给烟度测量造成了一定的误差。本文论述了旧标准烟度卡烟度值Rb与新标准烟度值SF之间的关系 相似文献
168.
The paper presents the novel design of double glazing helical coil solar cavity receiver for solar thermal applications. Performance model has been developed for the experimental setup based on energy balance equations. The results obtained were compared with horizontal tube receiver for the same experimental setup. The result shows that the 87.96% improvement in the convective heat transfer coefficient for the double glazing helical coil solar cavity receiver. Maximum conversion efficiency achieved is 21% more than that would be obtained for horizontal tube receiver. This paper also investigates how the quality of vacuum degraded with the temperature of the glass cover. 相似文献
169.
170.
耕地转为建设用地价格评估——以河南省南阳市为例 总被引:4,自引:0,他引:4
以经济增长理论为基础的传统土地估价理论与方法,对耕地价值缺乏完整认识,造成了耕地价格与转用建设用地价格的不连续性,论文在土地资源总价值理论基础上,通过对耕地价值的重建、耕地转为建设用地增值空间分析以及权益归属的研究,重新构建了城乡交错带耕地转为建设用地价格评估体系,提出耕地价格是经过外部性内在化以后的耕地资源权利的价值体现,它包括耕地实际生产收益价格、社会保障价格、社会稳定价格、生态安全价格和发展权价格5部分。同时以河南省南阳市为例,对该方法进行了实际应用,得出南阳市水田单位面积价值总量价格测算结果为139.81元/m2,该评估较好地反映了耕地的转用价格。 相似文献