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161.
2005年秋季长江口及其邻近水域浮游植物群集   总被引:3,自引:0,他引:3  
采用Utermhl分析方法,对长江口及其邻近水域(30.5° ~ 32.5° N,121.0° ~ 123.5° E)2005年秋季浮游植物进行了分析,并对其与环境之间的关系做了进一步的探讨。结果表明:调查区初步鉴定浮游植物95种(含变种和变型),硅藻是主要的浮游植物类群,其丰度比例达到93.1%;生态类型多为温带近岸种,少数为暖水种和大洋种;优势种主要为中肋骨条藻〖WTBX〗(Skeletonema costatum)、具槽帕拉藻(Paralia sulcata)、菱形海线藻(Thalassionema nitzschioides)和圆海链藻(Thalassiosira rotula)〖WTBZ〗;浮游植物平均丰度为2.04 cells/mL,高值出现在长江口门偏南水域;Margalef指数、Shannon Wiener指数以及Pielou指数的分布显示:秋季调查区离岸海域浮游植物多样性程度高,物种均一性好。Pearson相关分析结果显示:海水温度和硝酸盐含量是控制调查区浮游植物分布格局的主要环境因子;优势种中肋骨条藻与温度呈极显著负相关,与硝酸盐呈极显著正相关。  相似文献   
162.
基于分形理论的江苏沿江城镇体系研究   总被引:7,自引:0,他引:7  
开放条件下,“全球 地方”作用深刻影响着区域城镇体系,沿江发达地区表现尤其典型。基于分形的相关理论和方法,以2006年为时空断面,对江苏沿江地区城镇体系的空间分布进行实证研究。结果表明:(1)区域城镇规模等级结构服从Zipf定律,首位城市南京在区域城市体系中的垄断性相对较强,但并非处于绝对垄断地位;(2)空间关联维数显示,沿江地区城镇体系的交通网络通达性优良,各城镇间联系紧密;(3)根据分维数和无标度区分析,三大城市群中,宁镇扬城市群分形发育最好,苏锡常次之,通泰城市群分形发育最差;(4)扬州、镇江、南京和苏州的城镇集聚程度较高,分形发育较为成熟;南通、泰州、无锡和常州的集聚程度均较低,分形结构不佳。扬州在区域城镇体系中分形发育最为完善,中心性最好,历史上形成的这种空间格局至今没有变化.  相似文献   
163.
An intensive campaign was conducted in September 2012 to collect surface water samples along the tributaries of the Pearl River in southern China. Thirteen perfluoroalkyl acids (PFAAs), including perfluorocarboxylates (PFCAs, C4–C11) and perfluorosulfonates (PFSAs, C4, C6–C8, and C10), were determined using high-performance liquid chromatography/negative electrospray ionization–tandem mass spectrometry (HPLC/(-)ESI–MS/MS). The concentrations of total PFAAs (ΣPFAAs) ranged from 3.0 to 52 ng L−1, with an average of 19 ± 12 ng L−1. The highest concentrations of ΣPFAAs were detected in the surface water of the Dong Jiang tributary (17–52 ng L−1), followed by the main stream (13–26 ng L−1) and the Sha Wan stream (3.0–4.5 ng L−1). Perfluorooctanoate (PFOA), perfluorobutane sulfonate (PFBS), and perfluorooctane sulfonate (PFOS) were the three most abundant PFAAs and on average accounted for 20%, 24%, and 19% of ΣPFAAs, respectively. PFBS was the most abundant PFAA in the Dong Jiang tributary, and PFOA was the highest PFAA in the samples from the main stream of the Pearl River. A correlation was found between PFBS and PFOA, which suggests that both of these PFAAs originate from common source(s) in the region. Nevertheless, the slope of PFBS/PFOA was different in the different tributaries sampled, which indicates a spatial difference in the source profiles of the PFAAs.  相似文献   
164.
A GIS based pesticide risk indicator that integrates exposure variables (i.e. pesticide application, geographic, physicochemical and crop data) and toxicity endpoints (using species sensitivity distributions) was developed to estimate the Predicted Relative Exposure (PREX) and Predicted Relative Risk (PRRI) of applied pesticides to aquatic ecosystem health in the Lourens River catchment, Western Cape, South Africa. Samples were collected weekly at five sites from the beginning of the spraying season (October) till the beginning of the rainy season (April) and were semi quantitatively analysed for relevant pesticides applied according to the local farmers spraying programme. Monitoring data indicate that physicochemical data obtained from international databases are reliable indicators of pesticide behaviour in the Western Cape of South Africa. Sensitivity analysis identified KOC as the most important parameter influencing predictions of pesticide loading derived from runoff. A comparison to monitoring data showed that the PREX successfully identified hotspot sites, gave a reasonable estimation of the relative contamination potential of different pesticides at a site and identified important routes of exposure (i.e. runoff or spray drift) of different pesticides at different sites. All pesticides detected during a monitored runoff event, were indicated as being more associated with runoff than spray drift by the PREX. The PRRI identified azinphos-methyl and chlorpyrifos as high risk pesticides towards the aquatic ecosystem. These results contribute to providing increased confidence in the use of risk indicator applications and, in particular, could lead to improved utilisation of limited resources for monitoring and management in resource constrained countries.  相似文献   
165.
根据2007~2009年在长江干流的泸州、珞璜、宜都、武穴4个江段分别采集的数据,对这些江段鱼卵及仔鱼漂流特征的昼夜变化规律进行初步分析。结果显示,长江上游泸州江段和珞璜江段鱼卵及仔鱼昼夜漂流密度有一定差异,但不显著;长江中游宜都江段,鱼卵漂流密度在昼夜时间上有显著性差异(〖WTBX〗n=38,p〖WTBZ〗=000),表现为6〖DK〗∶00的平均漂流密度13.02 ind./100 m3明显大于18〖DK〗∶00的密度3.28 ind./100 m3,仔鱼夜间漂流密度明显大于白天,于22〖DK〗∶00达到高峰值;武穴江段仔鱼漂流密度在昼夜时间上有显著性差异(〖WTBX〗n=62,p〖WTBZ〗=000),8〖DK〗∶00的平均漂流密8621 ind./100 m3明显大于18〖DK〗∶00的密度4485 ind./100 m3。不同物种的鱼卵及仔鱼漂流密度亦呈现出一定的昼夜差异,宜都江段贝氏〖FK(W*5/5。1〗〖PS黎明政造字2.EPS;%84%84,BP〗〖FK)〗,草鱼和银鲴鱼卵主要分布在白天,鳙、鲢等种类分布在夜间;另外,鳙、银鮈、铜鱼和翘嘴鲌等多数种类的仔鱼仅在夜间有分布,而飘鱼属的种类主要分布在白天。通过采集到鱼卵发育期推算,四大家鱼、贝氏〖FK(W*5/5。1〗〖PS黎明政造字2.EPS;%84%84,BP〗〖FK)〗、银鲴和翘嘴鲌的繁殖时间主要集中在夜间,而花斑副沙鳅和鳊全天均有繁殖  相似文献   
166.
For over two decades, a manufacturer of electrical capacitors disposed of its waste within the karstic hinterland of the Krupa River (Slovenia) resulting in the surroundings becomming heavily polluted with PCB. Albeit the extent of the contamination has been known since 1983 and the Krupa River has become one of the most PCB polluted river in Europe, the effects on the cave fauna of the region remain unknown. The most famous cave dweller of the Krupa hinterland is the endemic cave salamander Proteus anguinus anguinus. In this study we determine the levels of PCB in the tissues of the Proteus and in river sediments. The total concentration of PCB in individual tissue samples from specimens of the Krupa spring was between 165.59 μg g−1 and 1560.20 μg g−1 dry wt, which is at least 28-times higher than those from an unpolluted site. The kidneys contained the lowest concentration, while the highest concentration was in subcutaneous fat and tissues with high lipid contents like visceral fat and liver. Total PCB concentrations in sediment samples from the Krupa River were between 5.47 and 59.20 μg g−1 dry wt showing that a high burden of PCB still remains in the region. The most abundant PCB congeners in all analyzed samples were di-ortho substituted (PCB #101, #118, #138 and #158), but higher proportion of mono-ortho PCB was present in sediments. The ability of Proteus to survive a high PCB loading in its environment and especially in its tissues is remarkable. Its partial elimination of low chlorinated and mono-ortho substituted congeners is also reported.  相似文献   
167.
Arsenic and other trace element concentrations were determined for tube-well water collected in the Lao PDR provinces of Attapeu, Bolikhamxai, Champasak, Savannakhet, Saravane, and Vientiane. Water samples, especially from floodplain areas of central and southern Laos, were significantly contaminated not only with As, but with B, Ba, Mn, U, and Fe as well. Total As concentrations ranged from <0.5 μg L−1 to 278 μg L−1, with over half exceeding the WHO guideline of 10 μg L−1. 46% of samples, notably, were dominated by As(III). Samples from Vientiane, further north, were all acceptable except on pH, which was below drinking water limits. A principal component analysis found associations between general water characteristics, As, and other trace elements. Causes of elevated As concentrations in Lao tube wells were considered similar to those in other Mekong River countries, particularly Cambodia and Vietnam, where young alluvial aquifers give rise to reducing conditions.  相似文献   
168.
Hu Z  Shi Y  Cai Y 《Chemosphere》2011,85(2):262-267
Seven typical synthetic musks (SMs) in the samples from the surface water, sediment and fish of the Haihe River were measured. The SM concentrations in the sediment and surface water of the Haihe River were significantly lower than those in the Dagu Drainage River and Chentaizi Drainage River (< 0.05). Along the flow direction, the SM concentrations in surface water and sediment tended to increase from the upstream to the downstream of Dagu Drainage River. The Bioaccumulation factors (BAFs) of galaxolide (HHCB) and tonalide (AHTN) were calculated at high levels in the muscles of crucian carp, common carp, and silver carp. Most of the biota-sediment accumulation factors (BSAFs) for HHCB and AHTN were higher than 1.7, suggesting magnification possibly exist in the musk bioaccumulations of the three fishes in the Haihe River. No significant differences in HHCB/AHTN ratios were observed among the water, fish, and sediment samples (p > 0.05). However, the HHCB/AHTN values in the Haihe River were much lower than those in the Dagu Drainage River and Chentaizi Drainage River (p < 0.05). Compared with several typical persistent organic pollutants (POPs), the musk concentrations were higher or comparable in the Haihe River.  相似文献   
169.
太湖流域的稻麦两熟复种大约产生于东晋南朝时期(317~589年),此后这一种植制度长期存在,并不断有所发展。考察发现,此一区域的稻麦两熟在历史上的大多数时候并无突出的季节矛盾,只是有两个时期例外。这两个时期一是明末清初,一是19世纪。太湖流域历史上突出的季节矛盾不由人口、品种等社会原因引起,而由气候变化这一自然因素导致。明末清初和19世纪分别是历史上最为寒冷的时期,是气候变冷造成了这一区域稻麦两熟突出的季节矛盾  相似文献   
170.
Kolen B  Helsloot I 《Disasters》2012,36(4):700-722
On 30 May 2008, the Government of the Netherlands informed the national parliament about the effectiveness of preventive evacuation of coastal and river areas in case of flooding. Analysis of a case study showed that it is impossible to evacuate coastal areas preventively within a 48-hour time span preceding a worst credible scenario flood caused by a storm surge. This fact illustrates the need for alternative evacuation strategies, such as vertical evacuation (evacuating to safe havens, inside the flood zone) or shelter-in-place (hiding), to reduce loss of life and the impact of the evacuation. This paper defines these strategies and demonstrates, by returning to the case study used by the Dutch government, that they require different measures, methods of approach, and crisis management processes. In addition, it addresses the need for flexible and scalable preparation so that after detecting and understanding the threat, authorities and citizens can make decisions about different evacuation strategies.  相似文献   
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