全文获取类型
收费全文 | 224篇 |
免费 | 8篇 |
专业分类
电工技术 | 1篇 |
综合类 | 1篇 |
化学工业 | 84篇 |
金属工艺 | 2篇 |
机械仪表 | 2篇 |
建筑科学 | 2篇 |
能源动力 | 4篇 |
轻工业 | 41篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 7篇 |
一般工业技术 | 38篇 |
冶金工业 | 30篇 |
原子能技术 | 1篇 |
自动化技术 | 17篇 |
出版年
2023年 | 6篇 |
2022年 | 14篇 |
2021年 | 14篇 |
2020年 | 3篇 |
2019年 | 9篇 |
2018年 | 4篇 |
2017年 | 8篇 |
2016年 | 7篇 |
2014年 | 4篇 |
2013年 | 14篇 |
2012年 | 15篇 |
2011年 | 17篇 |
2010年 | 11篇 |
2009年 | 12篇 |
2008年 | 9篇 |
2007年 | 17篇 |
2006年 | 9篇 |
2005年 | 7篇 |
2004年 | 11篇 |
2003年 | 3篇 |
2002年 | 3篇 |
2001年 | 1篇 |
1999年 | 4篇 |
1998年 | 6篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有232条查询结果,搜索用时 3 毫秒
221.
It is generally accepted that oxidation of carotenoids begins with epoxidation and cleavage to apocarotenals. However, systematic studies to demonstrate occurrence of these reactions are lacking. In this study, the products formed by epoxidation with m-chloroperbenzoic acid (MCPBA), oxidative cleavage with KMnO4 and autoxidation in model systems, in the presence and absence of light, at ambient condition were identified. The presence of oxidation products was also verified in processed products. β-carotene-5,6-epoxide, β-carotene-5,8-epoxide, β-carotene-5,6,5′,6′-diepoxide, β-carotene-5,6,5′,8′-diepoxide and β-carotene 5,8,5′,8′-diepoxide were formed by the reaction of β-carotene with MCPBA. The oxidation products with KMnO4 were identified as β-apo-8′-carotenal, β-apo-10′-carotenal, β-apo-12′-carotenal, β-apo-14′-carotenal and β-apo-15-carotenal, along with semi-β-carotenone and monohydroxy-β-carotene-5,8-epoxide. Except for β-carotene 5,6,5′,6′-diepoxide, these products were detected in the model systems. Some of these products were also found in mango juice, acerola juice and dried apricot. Increased Z-isomerization was also observed and Z-isomers of the oxidation products were detected. 相似文献
222.
223.
Maria Maddalena Storelli Arianna Storelli Delia Franchini 《The Science of the total environment》2009,408(1):64-68
PCB and DDT concentrations were determined in the adipose tissue of cats and dogs from Southern Italy. In cats p,p′-DDE was the most abundant DDT component (95.0%), while in dogs these compounds were absent, except in two specimens. PCB concentrations were higher in cats (199.02 ng g− 1 lipid weight) than in dogs (41.61 ng g− 1 lipid weight). Also there were inter-specific differences in the contribution of the different congeners to PCBs, although PCB 138, PCB 153 and PCB 180 were the most representative congeners in both species. Animals from one location, Taranto City, had significantly elevated concentrations of dioxin-like PCBs compared to the other locations. Consequently the estimated mean 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalents (TEQs) of coplanar PCBs were higher in these animals (cats: 0.65 pg g− 1 lipid weight; dogs 0.29 pg g− 1 lipid weight) than in the other ones (cats: 0.12 pg g− 1 lipid weight; dogs: 0.001 pg g− 1 lipid weight). 相似文献
224.
225.
226.
The retinamide-mediated apoptosis of promyelocytic cells was investigated using pHi- and DNA-sensitive fluorescent probes (BCECF and Hoechst 33342). Acidification and apoptosis were observed during prolonged (0-12 h) exposure to retinamide (1 microM), but were absent in a retinamide-resistant clone. The analysis of experiments performed by simultaneous staining with the two dyes showed that acidification and apoptosis are correlated; the half-time for acidification is about 5 h while that for apoptosis is 80% longer. On the whole, these results suggest that apoptosis is preceded by an early mechanism of acidification in human leukemia cells treated by a retinoid of clinical interest in cancer chemo prevention and therapy. 相似文献
227.
Polking MJ Urban JJ Milliron DJ Zheng H Chan E Caldwell MA Raoux S Kisielowski CF Ager JW Ramesh R Alivisatos AP 《Nano letters》2011,11(3):1147-1152
The question of the nature and stability of polar ordering in nanoscale ferroelectrics is examined with colloidal nanocrystals of germanium telluride (GeTe). We provide atomic-scale evidence for room-temperature polar ordering in individual nanocrystals using aberration-corrected transmission electron microscopy and demonstrate a reversible, size-dependent polar-nonpolar phase transition of displacive character in nanocrystal ensembles. A substantial linear component of the distortion is observed, which is in contrast with theoretical reports predicting a toroidal state. 相似文献
228.
A sequential aerobic completely stirred tank reactor (CSTR) following the anaerobic migrating blanket reactor (AMBR) was used to treat a synthetic wastewater containing 2,4-dinitrotoluene (2,4-DNT). A Box-Wilson statistical experiment design was used to determine the effects of 2,4-DNT and the hydraulic retention times (HRTs) on 2,4-DNT and COD removal efficiencies in the AMBR reactor. The 2,4-DNT concentrations in the feed (0-280 mg/L) and the HRT (0.5-10 days) were considered as the independent variables while the 2,4-DNT and chemical oxygen demand (COD) removal efficiencies, total and methane gas productions, methane gas percentage, pH, total volatile fatty acid (TVFA) and total volatile fatty acid/bicarbonate alkalinity (TVFA/Bic.Alk.) ratio were considered as the objective functions in the Box-Wilson statistical experiment design in the AMBR. The predicted data for the parameters given above were determined from the response functions by regression analysis of the experimental data and exhibited excellent agreement with the experimental results. The optimum HRT which gave the maximum COD (97.00%) and 2,4-DNT removal (99.90%) efficiencies was between 5 and 10 days at influent 2,4-DNT concentrations 1-280 mg/L in the AMBR. The aerobic CSTR was used for removals of residual COD remaining from the AMBR, and for metabolites of 2,4-DNT. The maximum COD removal efficiency was 99% at an HRT of 1.89 days at a 2,4-DNT concentration of 239 mg/L in the aerobic CSTR. It was found that 280 mg/L 2,4-DNT transformed to 2,4-diaminotoluene (2,4-DAT) via 2-amino-4-nitrotoluene (2-A-4-NT) and 4-amino-2-nitrotoluene (4-A-2-NT) in the AMBR. The maximum 2,4-DAT removal was 82% at an HRT of 8.61 days in the aerobic CSTR. The maximum total COD and 2,4-DNT removal efficiencies were 99.00% and 99.99%, respectively, at an influent 2,4-DNT concentration of 239 mg/L and at 1.89 days of HRT in the sequential AMBR/CSTR. 相似文献
229.
Luigi Bellocchio Alessio Danilo Inchingolo Angelo Michele Inchingolo Felice Lorusso Giuseppina Malcangi Luigi Santacroce Antonio Scarano Ioana Roxana Bordea Denisa Hazballa Maria Teresa DOria Ciro Gargiulo Isacco Ludovica Nucci Rosario Serpico Gianluca Martino Tartaglia Delia Giovanniello Maria Contaldo Marco Farronato Gianna Dipalma Francesco Inchingolo 《International journal of molecular sciences》2021,22(15)
Background: marijuana, the common name for cannabis sativa preparations, is one of the most consumed drug all over the world, both at therapeutical and recreational levels. With the legalization of medical uses of cannabis in many countries, and even its recreational use in most of these, the prevalence of marijuana use has markedly risen over the last decade. At the same time, there is also a higher prevalence in the health concerns related to cannabis use and abuse. Thus, it is mandatory for oral healthcare operators to know and deal with the consequences and effects of cannabis use on oral cavity health. This review will briefly summarize the components of cannabis and the endocannabinoid system, as well as the cellular and molecular mechanisms of biological cannabis action in human cells and biologic activities on tissues. We will also look into oropharyngeal tissue expression of cannabinoid receptors, together with a putative association of cannabis to several oral diseases. Therefore, this review will elaborate the basic biology and physiology of cannabinoids in human oral tissues with the aim of providing a better comprehension of the effects of its use and abuse on oral health, in order to include cannabinoid usage into dental patient health records as well as good medicinal practice. Methods: the paper selection was performed by PubMed/Medline and EMBASE electronic databases, and reported according to the PRISMA guidelines. The scientific products were included for qualitative analysis. Results: the paper search screened a total of 276 papers. After the initial screening and the eligibility assessment, a total of 32 articles were considered for the qualitative analysis. Conclusions: today, cannabis consumption has been correlated to a higher risk of gingival and periodontal disease, oral infection and cancer of the oral cavity, while the physico-chemical activity has not been completely clarified. Further investigations are necessary to evaluate a therapeutic efficacy of this class of drugs for the promising treatment of several different diseases of the salivary glands and oral diseases. 相似文献
230.
Corina Danciu Codruta Soica Mircea Oltean Stefana Avram Florin Borcan Erzsebet Csanyi Rita Ambrus Istvan Zupko Delia Muntean Cristina A. Dehelean Marius Craina Ramona A. Popovici 《International journal of molecular sciences》2014,15(2):1962-1982
Genistein is one of the most studied phytocompound in the class of isoflavones, presenting a notable estrogenic activity and in vitro and/or in vivo benefits in different types of cancer such as those of the bladder, kidney, lung, pancreatic, skin and endometrial cancer. A big inconvenience for drug development is low water solubility, which can be solved by using hydrophilic cyclodextrins. The aim of this study is to theoretically analyze, based on the interaction energy, the possibility of a complex formation between genistein (Gen) and three different ramified cyclodextrins (CD), using a 1:1 molar ratio Gen:CD. Theoretical data were correlated with a screening of both in vitro and in vivo activity. Proliferation of different human cancer cell lines, antimicrobial activity and angiogenesis behavior was analyzed in order to see if complexation has a beneficial effect for any of the above mentioned activities and if so, which of the three CDs is the most suitable for the incorporation of genistein, and which may lead to future improved pharmaceutical formulations. Results showed antiproliferative activity with different IC50 values for all tested cell lines, remarkable antimicrobial activity on Bacillus subtilis and antiangiogenic activity as revealed by CAM assay. Differences regarding the intensity of the activity for pure and the three Gen complexes were noticed as explained in the text. The data represent a proof that the three CDs can be used for furtherer research towards practical use in the pharmaceutical and medical field. 相似文献