全文获取类型
收费全文 | 364篇 |
免费 | 22篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 8篇 |
综合类 | 33篇 |
化学工业 | 75篇 |
金属工艺 | 4篇 |
机械仪表 | 35篇 |
建筑科学 | 46篇 |
矿业工程 | 10篇 |
能源动力 | 16篇 |
轻工业 | 11篇 |
水利工程 | 5篇 |
石油天然气 | 71篇 |
无线电 | 6篇 |
一般工业技术 | 51篇 |
冶金工业 | 2篇 |
原子能技术 | 2篇 |
自动化技术 | 23篇 |
出版年
2024年 | 1篇 |
2023年 | 7篇 |
2022年 | 2篇 |
2021年 | 6篇 |
2020年 | 10篇 |
2019年 | 6篇 |
2018年 | 16篇 |
2017年 | 9篇 |
2016年 | 20篇 |
2015年 | 16篇 |
2014年 | 18篇 |
2013年 | 34篇 |
2012年 | 14篇 |
2011年 | 20篇 |
2010年 | 28篇 |
2009年 | 26篇 |
2008年 | 20篇 |
2007年 | 32篇 |
2006年 | 21篇 |
2005年 | 28篇 |
2004年 | 16篇 |
2003年 | 12篇 |
2002年 | 8篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有398条查询结果,搜索用时 31 毫秒
11.
海相页岩TOC地震定量预测技术及其应用——以四川盆地焦石坝地区为例 总被引:1,自引:0,他引:1
总有机碳含量(TOC)是评价页岩生烃能力和页岩油气藏的一个重要指标,目前国内外利用地震资料直接定量预测TOC的报道很少,因此,有必要对地震预测TOC的方法作进一步的研究。为此,以四川盆地焦石坝地区为例,从岩心实测TOC出发,通过TOC与地球物理参数交会分析,寻找到TOC敏感地球物理参数——密度,并建立密度与TOC之间的最佳拟合方程,得到计算总有机碳含量的经验公式;结合叠前地震反演获得的密度体便可计算出TOC数据体,从而达到定量预测页岩TOC的目的。将改进的预测方法应用于四川盆地焦石坝地区海相页岩气勘探,结果表明:①利用叠前同时反演直接求得的密度体避免了累计误差,稳定性好,多解性少,结果可靠,为精细定量预测TOC提供了基础保证;②预测的TOC与实测结果吻合程度高,相对误差较小。结论认为,该技术在四川盆地海相页岩气勘探中具有广阔的应用前景。 相似文献
12.
The influence of different types of iron salts (i.e., ferrous or ferric cations with sulphate, nitrate or chloride anions) on the reaction between coarse thermomechanical pulp and acid hydrogen peroxide (Fenton chemistry) was studied when the initial pH was 3.2 and 5.3. Also, ferric ions chelated with EDTA or EDG at different molar ratios were compared with ferrous sulphate when the initial pH was extended from about 3 to 8. Different anions of ferric ion salt gave a similar catalytic effect. At an initial pH of 7–8, the ferric-EDTA catalyzed reaction resulted in similar or higher hydrogen peroxide consumption and more detectable hydroxyl radicals than the ferrous sulphate catalyzed reaction, but less reaction with the pulp was indicated. Between pH 5–8, using Fe-EDG as a catalyst gave higher hydrogen peroxide consumption and more detectable hydroxyl radicals than if using ferrous sulphate; however, the measured effect on the pulp was similar or less. 相似文献
13.
大沽排污河底泥污染严重,为了解底泥的特征,研究了大沽排污河底泥的理化性质.结果为:大沽排污河底泥的平均含水量为34.4%,平均pH值为6.8,全河段TOC平均值约为8%;Malven Mastersizer激光粒度仪测定了大沽排污河悬浮物和沉积物的粒径分布,结果表明主要以粉砂为主、占60%左右,其次为黏土、占30%左右,大沽排污河底泥颗粒属于细颗粒;X-射线衍射分析底泥的矿物主要由轻矿物和粘土矿物组成,轻矿物主要为石英、伊利石和方解石,粘土矿物主要由伊利石、绿泥石、蒙托石、高岭石组成;石英和伊利石是大沽排污河底泥悬浮物及沉积物矿物的主要成分,两者之和分别为75.5%和62.2%. 相似文献
14.
Joanna Kisaa Anna Tomaszewska Adriana Barylyak Yaroslav Bobitski Maciej Balawejder 《International journal of molecular sciences》2022,23(7)
Flame retardants have attracted growing environmental concern. Recently, an increasing number of studies have been conducted worldwide to investigate flame-retardant sources, environmental distribution, living organisms’ exposure, and toxicity. The presented studies include the degradation of 4,4′-isopropylidenebis(2,6-dibromophenol) (TBBPA) by ozonolysis and photocatalysis. In the photocatalytic process, nano- and micro-magnetite (n-Fe3O4 and μ-Fe3O4) are used as a catalyst. Monitoring of TBBPA decay in the photocatalysis and ozonolysis showed photocatalysis to be more effective. Significant removal of TBBPA was achieved within 10 min in photocatalysis (ca. 90%), while for ozonation, a comparable effect was observed within 70 min. To determine the best method of TBBPA degradation concentration on COD and TOC, the removals were examined. The highest oxidation state was obtained for photocatalysis on μ-Fe3O4, whereas for n-Fe3O4 and ozonolysis, the COD/TOC ratio was lower. Acute toxicity results show noticeable differences in the toxicity of TBBPA and its degradation products to Artemia franciscana and Thamnocephalus platyurus. The EC50 values indicate that TBBPA degradation products were toxic to harmful, whereas the TBPPA and post-reaction mixtures were toxic to the invertebrate species tested. The best efficiency in the removal and degradation of TBBPA was in the photocatalysis process on μ-Fe3O4 (reaction system 1). The examined crustaceans can be used as a sensitive test for acute toxicity evaluation. 相似文献
15.
我国后处理工业示范厂和后处理大厂产生的非工艺低放废水具有年产生量大、成分复杂、污染核素种类多等特点。针对后处理非工艺低放废水的特点,初步探究了使用混凝剂处理非工艺低放废水的可行性。研究用非离子型聚丙烯酰胺(NPAM)为助凝剂,比较了聚合氯化铝(PAC)、聚合硫酸铁(PFS)、阴离子型聚丙烯酰胺(PAM)3种混凝剂对模拟非工艺低放废水中总有机碳(TOC)的去除效果。通过正交实验探讨了混凝效果的影响因素。结果表明:聚合氯化铝对模拟非工艺低放废水的混凝效果最佳,混凝剂的投加量是影响混凝效果的主要因素。当混凝剂和助凝剂的加入量分别为348 mg/L和24 μg/L、混凝时间为30 min、pH=5时,得到去除模拟非工艺低放废水中TOC的最优方案,TOC去除率达到24%。 相似文献
16.
中性常压条件下研究了不同因素对CuO-H2O2矿化模型底物苯酚的影响。引入H2O2矿化指数(X)、矿化半衰期(t1/2)概念,结合总碳(TOC)去除及氧化剂分解规律,对催化矿化进行分析。结果表明:温度、催化剂、氧化剂、初始TOC质量浓度的增加均能不同程度地加速TOC去除,矿化半衰期t1/2更短。随温度、氧化剂浓度提高,H202矿化指数X先增加后减小,随初始TOC及催化剂质量浓度提高X分别增加和减小。提出了羟基自由基矿化机理,紫外可见分光光谱分析表明底物先被氧化为某些中间产物,再被矿化为CO2和H2O。 相似文献
17.
18.
Carbon dioxide emission and its regulation at land–water interface downstream of a point source at Ganga River (India)
下载免费PDF全文
![点击此处可从《Water and Environment Journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Deepa Jaiswal Ekabal Siddiqui Kavita Verma Jitendra Pandey 《Water and Environment Journal》2018,32(3):351-357
The streams and rivers are considered hotspots of CO2 exchange; and representative direct CO2 emission measurements are essential for a correct regional estimate. We measured CO2 emission flux at 15 sites at land–water interface downstream of a point source during low flow for three consecutive months for the year 2017. The general range of CO2 efflux observed here was close to the results of regional studies, although values near the point source were disproportionately high (>350 mg/m2/h). CO2 emission flux showed strong dependence on total organic carbon (TOC; R2 = 0.96; P < 0.001), (R2 = 0.88; P < 0.001), soluble reactive‐P (SRP; R2 = 0.91; P < 0.001) and microbial activity measured in terms of fluorescein diacetate activity (FDAase; R2 = 0.92; P < 0.001) and substrate induced respiration (SIR; R2 = 0.96; P < 0.001). Because point source‐associated interfaces provide heterogeneous habitats, our study suggests the need for large scale monitoring of CO2 emission at land–water interface of major rivers for more correctly presenting the regional scale CO2 budget. 相似文献
19.
20.