全文获取类型
收费全文 | 1617篇 |
免费 | 64篇 |
国内免费 | 669篇 |
专业分类
安全科学 | 120篇 |
废物处理 | 92篇 |
环保管理 | 132篇 |
综合类 | 940篇 |
基础理论 | 299篇 |
污染及防治 | 595篇 |
评价与监测 | 48篇 |
社会与环境 | 45篇 |
灾害及防治 | 79篇 |
出版年
2024年 | 2篇 |
2023年 | 26篇 |
2022年 | 84篇 |
2021年 | 67篇 |
2020年 | 49篇 |
2019年 | 38篇 |
2018年 | 57篇 |
2017年 | 72篇 |
2016年 | 82篇 |
2015年 | 73篇 |
2014年 | 132篇 |
2013年 | 159篇 |
2012年 | 156篇 |
2011年 | 128篇 |
2010年 | 116篇 |
2009年 | 113篇 |
2008年 | 128篇 |
2007年 | 108篇 |
2006年 | 90篇 |
2005年 | 77篇 |
2004年 | 34篇 |
2003年 | 60篇 |
2002年 | 59篇 |
2001年 | 49篇 |
2000年 | 48篇 |
1999年 | 58篇 |
1998年 | 53篇 |
1997年 | 43篇 |
1996年 | 39篇 |
1995年 | 38篇 |
1994年 | 22篇 |
1993年 | 25篇 |
1992年 | 20篇 |
1991年 | 14篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 8篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
排序方式: 共有2350条查询结果,搜索用时 265 毫秒
721.
Shumei Jiang Xiang Li Long Zhang Wei Sun Shikun Dai Lianwu Xie Yonghong Liu Kyung Jin Lee 《Marine Biology》2008,153(5):945-952
The study describes the diversity of actinobacteria isolated from the marine sponge Iotrochota sp. collected in the South China Sea. Species and natural product diversity of isolates were analyzed, including screening
for genes encoding polyketide synthases (PKS) and nonribosomal peptide synthetase (NRPS), and 16S rRNA gene restriction fragment
length polymorphism (RFLP). PKS and NRPS sequences were detected in more than half of the isolates and the different “PKS-I–PKS-II–NRPS”
combinations in different isolates belonging to the same species indicated a potential natural product diversity and divergent
genetic evolution. The phylogenetic analysis based on 16S rRNA gene sequencing showed that the isolates belonged to genera
Streptomyces, Cellulosimicrobium, and Nocardiopsis. The majority of the strains tested belonged to the genus Streptomyces and one of them may be a new species. To our knowledge, this is the first report of a bacterium classified as Cellulosimicrobium sp. isolated from a marine sponge.
Key Laboratory of Marine Bio-recourses Sustainable Utilization (LMB-CAS), Guangdong Key Laboratory of Marine Materia Medica
(LMMM-GD), South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, People’s Republic of China. 相似文献
722.
The mantle of the pearl oyster Pinctada fucata was adopted for the proliferation profile study in our work and a proliferation hot spot was found in the outer epithelia
of mantle central zone using the BrdU immunohistochemistry method. This result contradicts the previous research that the
mantle has numerous growth centers all over the mantle epithelium, with the same proliferation activity throughout the whole
mantle outer epithelial cells. This is the first report on the different proliferation features on the whole mantle where
Alcian Blue/PAS staining analysis and ultrastructural observation with the aid of transmission electron microscope (TEM) demonstrated
distinct features of the epithelium in four different regions of the mantle. Results from the present investigation displayed
that in the outer epithelium of the marginal zone in mantle outer fold, organelles such as mitochondria and endoplasmic reticulum
(ER) were well-developed and double membrane bounded vesicles were present; in the outer epithelia of mantle central zone,
stem-like cells with a high ratio of nucleus to cytoplasm and comparatively undeveloped organelles were detected. Together
with the observations of the cell proliferation profile of different regions of the mantle, a hypothetic model for the proliferation
and differentiation of the pearl oyster’s mantle is proposed: there exists a proliferation “hot spot” in the outer epithelial
cells of central zone and the proliferation ability decreases progressively from this “hot spot” towards the marginal zone;
the whole mantle’s differentiation occurs continuously with its growth and the direction is from the proliferation ‘hot spot’
(central zone) towards the marginal zone. Furthermore, another interesting result was found when the proliferation rate was
investigated together with the tidal rhythm: the proliferation activity was found to be closely correlated with the tidal
rhythm, indicating that the mantle outer epithelia’s proliferation rhythm might be the impetus of the shell’s daily growth
bands. 相似文献
723.
724.
运用生态学的方法,结合实地调查与数理统计分析,对珠江三角洲城市群的大气微生物与环境的相关性问题进行探讨,拟为珠江三角洲城市环境污染的综合防治和卫生防疫工作提供依据,研究结果表明.(1)珠江三角洲城市群中广州和东莞的大气微生物含量较高,其中细菌比真菌含量高;室内较室外,无绿化地较有绿化地的大气微生物含量高,在全年中,春、夏季节的大气微生物含量相对较高.(2)大气风速、湿度、气温、可吸入颗粒、总悬浮颗粒、人口流动,绿化状况等环境因子与大气微生物真菌、细菌的平均含量有较明显的相关关系,大气微生物含量与气象因子多数呈正或负的线性关系.相关分析的计算结果为:真菌、细菌平均含量在春、夏、秋、冬四个季度中与大气温度、湿度、风速大多数地区相关程度比较高,其值R在0.583~0.988之间,真菌、细菌与可吸人颗粒数和总悬浮颗粒数,R值分别为为0.525,0.388和0.081,-0.044.一元线性回归分析和多元线性回归分析计算结果为:大气微生物含量与气象因子有明显的正或负的线性关系.真菌、细菌的平均含量与温度、湿度、风速一元线性回归模型的置信水平较高,其p值大多在0.019~0.483之间,T值在0.001~0.246之间;多元线性回归模型的置信水平也较高,其P值大多数在0.083~0.220之间,T值在0.026~0.132之间;排序值显示:温度、风速变化是大气微生物含量高低影响重要性最大的环境因子.(3)统计数据比较分析表明:大气微生物含量与人口密集状况、人口流动大小和绿化状况好坏也有较明显的相关性,火车站,汽车客运站售票厅,人口流量大,绿化无,大气微生物(真菌细菌)平均含量高;而人口流量相对较少,但车流量大,有一定的绿化带的道路大气微生物平均含量较低;环境条件、绿化较好的公园绿地大气微生物含量低,车流、人流多,绿化少的地段、商业中心大气微生物含量较高. 相似文献
725.
生态工业园中企业的动力机制分析 总被引:17,自引:0,他引:17
本文分析了生态工业园中企业的社会和经济属性以及其决策的关键约束条件,指出企业能够参与生态工业园建设是由于生态工业园合乎企业的基本性质的要求,能够使得企业实现经济价值的同时实现社会价值,这就是生态工业园中企业参与生态工业园建设的驱动力之所在。最后,根据生态工业园中企业的特性和生态工业园的特点提出了若干促进企业参与生态工业园建设的建议。 相似文献
726.
中孔分子筛Al-MCM-41催化裂解聚烯烃反应研究 总被引:2,自引:0,他引:2
采用水热合成法制备了不同硅铝比的中孔分子筛A l-MCM-41,将其应用于高密度聚乙烯(HDPE)和聚丙烯(PP)的催化裂解反应。通过改变硅铝比、反应温度和催化剂用量,对A l-MCM-41催化HDPE和PP裂解反应的规律进行了探讨,研究表明,HDPE裂解反应受硅铝比的影响较大;而对于PP裂解反应,硅铝比在一定范围内对催化剂活性的影响不明显。另外,与热裂解和HZSM-5小孔分子筛的催化裂解结果进行了比较,结果证明A l-MCM-41具有较高的催化活性和较高的液体产物收率,尤其适合于空间位阻较大的PP的催化裂解反应。 相似文献
727.
728.
729.
This article proposed the concept of"climate capacity"as a way of measuring human’s adaptiveness to climate change.This article also focused on the related concepts like ecological carrying capacity,water resources carrying capacity,land carrying capacity as well as population carrying capacity.The concept of climate capacity was articulated against a background of global climate and environmental change.Essentially,China’s efforts to adapt to climate change was a matter of improving climate capacity,which is the ecosystem as well as the frequency,the intensity and the scale of human’s social activities that the climatic resources of a particular geographic area were supposed to support.The climate capacity has two components.One is the natural climate capacity,which includes temperature,sunlight,precipitation,extreme climatic events,etc.The other is the derived climate capacity,which includes water resources,land resources,ecological systems,climatic risks,etc.The climate capacity can be developed or be transferred between regions by taking engineering,technology or regime-based adaptive measures.However,these adaptive measures must be implemented under the principle of economic rationalism,ecological integrity,climate protection,and social justice.It is expected that by combining the climate capacity and its threshold value with the assessment of climate change risks,we are able to predict the optimal population carrying capacity and the scale of socioeconomic development,and furthermore,provide policy support for the socioeconomic development strategy and adaptive planning.In the regions with high climate capacity,there is a symbiotic relationship between adaptation and socioeconomic development.But,in the regions with limited climate capacity,irrational development may further damage the environment.Taking the Yangtze River delta,a region with high climate capacity,and a region of Ningxia,a region with limited climate capacity,as illustrative examples,the authors of this article analyzed the policy implications of climate capacity and further made suggestions on the problems of capacitylimited adaptation and development-driven adaptation.This article argued that the concept of climate capacity can not only be used as an analytical instrument of climate change economics,but also it can provide research support for planning regional adaptation and development with climate change impact and risk assessments. 相似文献
730.