全文获取类型
收费全文 | 16354篇 |
免费 | 4721篇 |
国内免费 | 28099篇 |
专业分类
安全科学 | 1682篇 |
废物处理 | 693篇 |
环保管理 | 1375篇 |
综合类 | 32447篇 |
基础理论 | 3217篇 |
环境理论 | 2篇 |
污染及防治 | 7102篇 |
评价与监测 | 1662篇 |
社会与环境 | 405篇 |
灾害及防治 | 589篇 |
出版年
2024年 | 32篇 |
2023年 | 205篇 |
2022年 | 512篇 |
2021年 | 487篇 |
2020年 | 985篇 |
2019年 | 2131篇 |
2018年 | 2322篇 |
2017年 | 2408篇 |
2016年 | 2203篇 |
2015年 | 2631篇 |
2014年 | 3250篇 |
2013年 | 3557篇 |
2012年 | 3369篇 |
2011年 | 2918篇 |
2010年 | 2615篇 |
2009年 | 2568篇 |
2008年 | 2254篇 |
2007年 | 2238篇 |
2006年 | 1658篇 |
2005年 | 1254篇 |
2004年 | 1098篇 |
2003年 | 904篇 |
2002年 | 737篇 |
2001年 | 742篇 |
2000年 | 873篇 |
1999年 | 778篇 |
1998年 | 605篇 |
1997年 | 572篇 |
1996年 | 573篇 |
1995年 | 491篇 |
1994年 | 358篇 |
1993年 | 255篇 |
1992年 | 302篇 |
1991年 | 290篇 |
1990年 | 244篇 |
1989年 | 208篇 |
1988年 | 146篇 |
1987年 | 74篇 |
1986年 | 74篇 |
1985年 | 53篇 |
1984年 | 55篇 |
1983年 | 42篇 |
1982年 | 45篇 |
1981年 | 35篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 5篇 |
1972年 | 5篇 |
1971年 | 5篇 |
1957年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Geng Jinju Wang Qiang Niu Xiaojun Wang Xiaorong 《Frontiers of Environmental Science & Engineering in China》2007,1(1):120-124
Effects of pH, temperature, and oxygen on the production and release of phosphine in eutrophic lake sediments were investigated
under laboratory tests. Results indicated that the elimination of matrix-bound phosphine was accelerated under initial pH
1 or 12. Phosphine levels could reach maximum under initial pH 10. The contents of phosphine increased with the addition of
alkali under pH 4–12. The rates of phosphine production and release from lake sediments varied with temperature. 20°C was
the most favorable temperature for the production of matrix-bound phosphine. Oxygen showed little effect on matrix-bound phosphine.
Matrix-bound phosphine concentrations in lake sediments were concluded to be dependent on a balance of natural generation
and depletion processes.
Translated from Acta Scientise Circumstantiae, 2005, 25(5): 681–685 [译自: 环境科学学报] 相似文献
12.
主要介绍了工业牌号高强铝合金在供应态或经简单预处理后在通用油压机上超塑成形的实例,并分析探讨了非理想组织材料超塑成形中微观组织的变化。 相似文献
13.
Rapid detection of numerical aberrations of chromosomes 13, 18 and 21 in chorionic mesenchymal cells
We have devised and evaluated a rapid screening method for the detection of numerical aberrations of chromosomes13, 18 and 21 in chorionic villus cells. We used non-radioactive in situ hybridization (ISH) with three chromosome-specific probes on overnight-attached mesenchymal cells from chorionic villi. A blind study was performed of 47 karyotypically normal samples, one triploid sample, two samples trisomic for chromosome 21, and two samples from a fetus with putative mosaicism (46/47, +21). All samples were hybridized with the chromosome 18- and 21-specific probes. Thirty samples were additionally hybridized with the chromosome 13-specific probe. The test could be completed within 3-4 days of sampling. In samples disomic with respect to the probed chromosomes, an average of 2 per cent (range 0-9 per cent) had three hybridization signals. By contrast, in the samples trisomic for the probed chromosome(s), 57 per cent (chromosome 13), 51 per cent (chromosome 18), and an average of 74 per cent (55-86 per cent) (chromosome 21) of the nuclei exhibited three signals. In the putative mosaic samples, the number of nuclei with three chromosome 21-specific signals ranged from 41 to 69 per cent. We conclude that this technique rapidly and clearly distinguishes between normal and trisomic/triploid samples, and consequently may be of use in future prenatal diagnosis. 相似文献
14.
厌氧升流式污泥层反应器在较高的COD容积负荷和水力负荷下稳定运行的关键是要有良好的固液分离,而固液分离的必要条件是污泥的沉降速度大于混合液在三相分离器的沉降区的最小断面上的向上流速。通过小型装置的试验表明,污泥的沉降速度与污泥的性状和浓度有关,使反应器内的污泥颗粒化能改善污泥沉降性、提高固液分离效果,使反应器能在相当高的COD容积负荷(20—30kgCOD/m~3·d)和水力负荷(0.8m~3/m~2·h)下稳定运行。本文叙述了厌氧升流式污泥层反应器内的污泥颗粒化过程,并简要地讨论了培养颗粒污泥的基本条件。 相似文献
15.
故障安全控制系统在催化裂化装置的应用 总被引:1,自引:0,他引:1
介绍霍尼韦尔公司故障安全控制系统FSC的技术特点以及在我厂重油催化裂化装置的应用情况,说明了该装置故障安全控制系统组成和操作界面,并总结了应用效果。 相似文献
16.
Wu Rui Li Guangyi Zhang Zongyi Ren Yulong Han Weijian 《Frontiers of Environmental Science & Engineering in China》2007,1(3):292-298
Road transport produces significant amounts of emissions by using crude oil as the primary energy source. A reduction of emissions
can be achieved by implementing alternative fuel chains. The objective of this study is to carry out an economic, environmental
and energy (EEE) life cycle study on natural gas-based automotive fuels with conventional gasoline in an abundant region of
China. A set of indices of four fuels/vehicle systems on the basis of life cycle are assessed in terms of impact of EEE, in
which natural gas produces compressed natural gas (CNG), methanol, dimethylether (DME) and Fischer Tropsch diesel (FTD). The
study included fuel production, vehicle production, vehicle operation, infrastructure and vehicle end of life as a system
for each fuel/vehicle system. A generic gasoline fueled car is used as a baseline. Data have been reviewed and modified based
on the best knowledge available to Chongqing local sources. Results indicated that when we could not change electric and hydrogen
fuel cell vehicles into commercial vehicles on a large scale, direct use of CNG in a dedicated or bi-fuel vehicle is an economical
choice for the region which is most energy efficient and more environmental friendly. The study can be used to support decisions
on how natural gas resources can best be utilized as a fuel/energy resource for automobiles, and what issues need to be resolved
in Chongqing. The models and approaches for this study can be applied to other regions of China as long as all the assumptions
are well defined and modified to find a substitute automotive energy source and establish an energy policy in a specific region. 相似文献
17.
南水北调中线不同调水方案下的汉江水华发生概率分析 总被引:1,自引:0,他引:1
为评估南水北调中线工程对汉江中下游水华的影响,从汉江水华的成因机理分析入手,提出了汉江水华发生概率的计算模型.该模型由河流一维水动力学模型、水体富营养化模型以及随机数生成模型组成,它不仅可以模拟汉江水华的发生机理,而且可以对诱发水华的各种因子进行随机抽样组合,从而求出中线调水不同方案实施后汉江水华的发生概率.计算结果表明,在现状情况下汉江水华的发生概率为9.2%,南水北调中线各调水方案(无引江济汉工程)实施后,汉江水华发生的概率将有一定程度的增加,而如果调水方案与引江济汉工程同时兴建将大大减少汉江水华发生的概率.最后提出建议,汉江自身的水污染治理是减少水华发生概率的最根本措施,而丹江口水库和引江济汉工程的联合调度将会减小汉江水华发生的概率. 相似文献
18.
多层印制板生产过程中的废水处理技术 总被引:2,自引:0,他引:2
本文对我国多层印制板生产中的废水处理问题,结合国内外相关企业的经验,提出了一种行之有效的多层印制板生产过程中的废水处理技术. 相似文献
19.
Zhong Runsheng Zhu Chunwei Zhang Xihui Guan Yuntao 《Frontiers of Environmental Science & Engineering in China》2007,1(3):276-279
The turbidity variation in artificial water and samples from a water plant was investigated in the presence of organics with
different relative molecular mass. The results show that recessive turbidity existed when water chemical conditions were changing.
The formation of turbidity depended on organic relative molecular mass and their conformations on particles. At higher pH
and lower ionic strength, the organic chains with a more extended conformation resulted in rising turbidity of the suspension.
At lower pH, the reconformation of organics took place due to charge neutralization by the proton, resulting in a decline
in turbidity. The addition of NaCl and MgCl2 at pH 7.00 also resulted in a decrease of turbidity in the suspension. It is believed that the occurrence of recessive turbidity
has a significant influence on the stability of water supply quality. 相似文献
20.
浅谈混凝沉淀在炼油污水中的应用 总被引:1,自引:0,他引:1
杨洪波 《石油化工环境保护》2000,(1):15-18
随着国家对环保的重视,为确保处理效果,混凝沉淀技术在一些炼油污水中得到应用,并取得了较好的效果。 相似文献