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231.
In this article, we introduce China’s major forest types and discuss the historical development of forest management in China,
including actions taken over the last decade toward achieving SMF. Major challenges are identified, and a strategy for SFM
implementation in China is presented. China’s forests consist of a wide variety of types with distinctive distributional patterns
shaped by complex topography and multiple climate regimes. How to manage this wide array of forest resources has challenged
forest managers and policy-makers since the founding of the country. Excessive exploitation of China's forest resources from
the 1950s to the late 1990s contributed to environmental problems and calamities, such as floods, soil erosion, and desertification.
At the start of the new millennium, the Chinese government decided to shift its emphasis from timber production towards the
achievement of sustainable forest management (SFM). With a series of endeavors such as the implementation of the “Six Key
Forestry Projects” and the reform of forest tenure policies, and the adoption of a classification system for China's forests,
a beginning has been made at reversing the trend of environmental degradation that occurred throughout the latter half of
the last century. At the same time, huge challenges remain to be tackled for the development of forestry in China. 相似文献
232.
The maintenance of a timely, reliable and accurate spatial database on current forest ecosystem conditions and changes is
essential to characterize and assess forest resources and support sustainable forest management. Information for such a database
can be obtained only through a continuous forest inventory. The National Forest Continuous Inventory (NFCI) is the first level
of China’s three-tiered inventory system. The NFCI is administered by the State Forestry Administration; data are acquired
by five inventory institutions around the country. Several important components of the database include land type, forest
classification and ageclass/ age-group. The NFCI database in China is constructed based on 5-year inventory periods, resulting
in some of the data not being timely when reports are issued. To address this problem, a forest growth simulation model has
been developed to update the database for years between the periodic inventories. In order to aid in forest plan design and
management, a three-dimensional virtual reality system of forest landscapes for selected units in the database (compartment
or sub-compartment) has also been developed based on Virtual Reality Modeling Language. In addition, a transparent internet
publishing system for a spatial database based on open source WebGIS (UMN Map Server) has been designed and utilized to enhance
public understanding and encourage free participation of interested parties in the development, implementation, and planning
of sustainable forest management. 相似文献
233.
上覆水营养盐浓度对底泥氮磷释放的影响 总被引:2,自引:0,他引:2
采用校园水体底泥进行上覆水营养盐浓度对底泥释放量之间的关系研究。结果表明,在本实验条件下,上覆水水质影响底泥氮、磷的释放,尤其显著影响氮、磷的初期释放;上覆水氮、磷的浓度越小,底泥氮、磷的释放量越大;上覆水氮、磷的浓度超过一定值,会抑制底泥氮、磷的释放。 相似文献
234.
Chiang CT Chang TK Hwang YH Su CC Tsai KY Yuan TH Lian IeB 《Environmental geochemistry and health》2011,33(5):469-476
The growing incidence of oral cancer (OC) in Taiwan has become a crucial public health concern. In particular, Changhua, a
county in central Taiwan, carries persistently high OC incidence rate, with an alarmingly high male/female ratio of OC incidence.
Previous epidemiological studies had found that the incidence is spatially correlated with the level of soil content to certain
heavy metals in the central Taiwan area. Soil and the human body both intake environmental heavy metals, which can be absorbed
through various ways. The soil metal concentration is an index of possible environmental exposure to heavy metal, and the
blood metal concentration somewhat reflects the level of the exposure on the human body. Metallic carcinogen is likely to
generate free radicals and play a role in many cancers, and many studies had reported that environmental exposure to heavy
metals is an important risk factor for developing cancer. Studies on animals showed that chronic intake of chromium (Cr) could
induce OC. This study aims to explore the association between the Cr concentration in the farm soil and in the blood of OC
patients. We recruited 79 OC patients from Changhua County, with their lifestyle being adjusted in regression analysis. The
results showed that the Cr concentration in the blood of OC patients is significantly higher than the background value, and
is positively associated with the Cr concentration in the soil surrounding their residence (p-value < 0.023). Because Changhua County is only with moderate prevalence of the known OC habitual risk factors, an environmental
factor related to heavy metal Cr exposure is suspected. Future investigations may verify the causal relation between Cr and
OC. 相似文献
235.
Xiang Yang Sun Cheng Da Gao Lin Zhang Su Yan Li Yong Qiao 《Environmental monitoring and assessment》2011,175(1-4):193-200
CO2 release from forest soil is a key driver of carbon cycling between the soil and atmosphere ecosystem. The rate of CO2 released from soil was measured in three forest stands (in the mountainous region near Beijing, China) by the alkaline absorption method from 2004 to 2006. The rate of CO2 released did not differ among the three stands. The CO2 release rate ranged from ??341 to 1,193 mg m???2 h???1, and the mean value over all three forests and sampling times was 286 mg m???2 h???1. CO2 release was positively correlated with soil water content and the soil temperature. Diurnally, CO2 release was higher in the day than at night. Seasonally, CO2 release was highest in early autumn and lowest in winter; in winter, negative values of CO2 release suggested that CO2 was absorbed by soil. 相似文献
236.
Mobilization and plant accumulation of prometryne in soil by two different sources of organic matter
Prometryne is a selective herbicide of the s-triazine chemical family. Due to its weak absorption onto soil, it readily leaches down through the soil and contaminates underground water. Application of organic manure to soil has become a widespread practice as a disposal strategy to improve soil properties. In this study, we demonstrated the effect of pig manure compost (PMC) and lake-bed sludge (SL) on the sorption/desorption, mobility and bioavailability of prometryne in soil using comprehensive analysis approaches. Downward movement of prometryne was monitored in the packed soil column. Addition of PMC or SL decreased considerably the mobility and total concentration of prometryne in the soil leachate. Bioavailability analyses with wheat plants revealed that addition of the organic matter reduced accumulation of prometryne in tissues and increased plant elongation and biomass. These results indicate that the organic amendments are effective in modifying adsorption and mobility of the pesticide in soil. 相似文献
237.
采用溶剂热法将Bi单质附着于草酸亚铁(FeOx)上,制备了系列Bi-FeOx复合催化剂并用于活化过硫酸盐.通过X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FT-IR)、扫描电子显微镜(SEM)、X射线光电子能谱仪(XPS)等表征方法对复合催化剂的结构、形貌和元素价态进行表征.以罗丹明B(RhB)为降解对象,研究了Bi-FeOx/过硫酸盐/可见光体系中Bi单质含量、催化剂投加量、pH及过硫酸盐浓度等因素对RhB的降解影响.在最佳条件下,反应5 min后,RhB的降解率高达99.8%.Bi的引入,使得复合催化剂增强了对可见光的吸收,提高了光生电子的传输效率,从而加速了对RhB的降解. 相似文献
238.
Sodium hypochlorite (NaClO) is a commonly applied cleaning agent for ultrafiltration membranes in water and wastewater treatment. Long-term exposure to NaClO might change the properties and performance of polymeric membranes, and ultimately shorten membrane lifespan. Active species in NaClO solution vary with solution pH, and the aging effects can change depending on the membrane material. In this study, the aging of polyvinylidene fluoride (PVDF) and polyethersulfone (PES) membranes by NaClO at pH 3–11 was investigated by examining variations in chemical composition, surface charge, surface morphology, mechanical strength, permeability, and retention ability. Polyvinyl pyrrolidone (PVP), which was blended in both membranes, was oxidized and dislodged due to NaClO aging at all investigated pH values, but the oxidation products and dislodgement ratio of PVP varied with solution pH. For the PVDF membrane, NaClO aging at pH 3–11 caused a moderate increase in permeability and decreased retention due to the oxidation and release of PVP. The tensile strength decreased only at pH 11 because of the defluorination of PVDF molecules. For the PES membrane, NaClO aging at all investigated pH resulted in chain scission of PES molecules, which was favored at pH 7 and 9, potentially due to the formation of free radicals. Therefore, a decrease in tensile strength and retention ability, as well as an increase in permeability, occurred in the PES membrane for NaClO aging at pH 3–11. Overall, the results can provide a basis for selecting chemical cleaning conditions for PVDF and PES membranes. 相似文献
239.
湖泊富营养化模型的研究进展 总被引:1,自引:0,他引:1
湖泊的富营养化是全球普遍关注的环境问题之一.湖泊的富营养化模型是防治、修复和治理湖泊富营养化的重要决策工具.按研究的侧重点不同,将湖泊富营养化模型分为简单回归模型、水质模型、生态模型和生态-水动力水质模型,并分别回顾了四类模型的研究进展.最后指出湖泊富营养化模型的发展趋势,强调不确定理论、3S技术、耦合模型是今后湖泊富营养化模型研究的重点,应在此基础上建立通用的模拟、预测、评价和优化模型,为湖泊富营养化管理提供科学依据. 相似文献
240.
Ma Xiaoling Tan Hongbin Su Xuemei Hou Xiong Dong Faqin Yang Feihua 《Journal of Material Cycles and Waste Management》2022,24(4):1542-1550
Journal of Material Cycles and Waste Management - Red gypsum comes from TiO2 production industry by sulfate method, which comes from the low acidic liquid stream treatment using lime or limestone.... 相似文献