全文获取类型
收费全文 | 1257篇 |
免费 | 78篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 498篇 |
金属工艺 | 13篇 |
机械仪表 | 29篇 |
建筑科学 | 56篇 |
矿业工程 | 1篇 |
能源动力 | 33篇 |
轻工业 | 289篇 |
水利工程 | 7篇 |
石油天然气 | 6篇 |
无线电 | 47篇 |
一般工业技术 | 131篇 |
冶金工业 | 80篇 |
原子能技术 | 2篇 |
自动化技术 | 142篇 |
出版年
2024年 | 2篇 |
2023年 | 13篇 |
2022年 | 100篇 |
2021年 | 92篇 |
2020年 | 39篇 |
2019年 | 45篇 |
2018年 | 43篇 |
2017年 | 40篇 |
2016年 | 52篇 |
2015年 | 46篇 |
2014年 | 52篇 |
2013年 | 85篇 |
2012年 | 84篇 |
2011年 | 80篇 |
2010年 | 71篇 |
2009年 | 70篇 |
2008年 | 80篇 |
2007年 | 59篇 |
2006年 | 46篇 |
2005年 | 36篇 |
2004年 | 33篇 |
2003年 | 20篇 |
2002年 | 21篇 |
2001年 | 23篇 |
2000年 | 13篇 |
1999年 | 11篇 |
1998年 | 2篇 |
1997年 | 10篇 |
1996年 | 6篇 |
1995年 | 9篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 7篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 6篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1972年 | 2篇 |
排序方式: 共有1335条查询结果,搜索用时 15 毫秒
991.
Weinstock Jeremiah; Burton Steve; Rash Carla J.; Moran Sheila; Biller Warren; Krudelbach Norman; Phoenix Natalie; Morasco Benjamin J. 《Canadian Metallurgical Quarterly》2011,25(2):372
Gambling help-lines are an essential access point, or frontline resource, for treatment seeking. This study investigated treatment engagement after calling a gambling help-line. From 2000–2007 over 2,900 unique callers were offered an in-person assessment appointment. Logistic regression analyses assessed predictors of (a) accepting the referral to the in-person assessment appointment and (b) attending the in-person assessment appointment. Over 76% of callers accepted the referral and 55% of all callers attended the in-person assessment appointment. This treatment engagement rate is higher than typically found for other help-lines. Demographic factors and clinical factors such as gender, severity of gambling problems, amount of gambling debt, and coercion by legal and social networks predicted engagement in treatment. Programmatic factors such as offering an appointment within 72 hr also aided treatment engagement. Results suggest gambling help-lines can be a convenient and confidential way for many individuals with gambling problems to access gambling-specific treatment. Alternative services such as telephone counseling may be beneficial for those who do not engage in treatment. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
992.
Schwartz Sarah E. O.; Rhodes Jean E.; Chan Christian S.; Herrera Carla 《Canadian Metallurgical Quarterly》2011,47(2):450
Associations between youths' relationship profiles and mentoring outcomes were explored in the context of a national, randomized study of 1,139 youths (54% female) in geographically diverse Big Brothers Big Sisters school-based mentoring programs. The sample included youths in Grades 4–9 from diverse racial and ethnic backgrounds, the majority of whom were receiving free or reduced-price lunch. Latent profile analysis, a person-oriented approach, was used to identify 3 distinct relational profiles. Mentoring was found to have differential effects depending on youths' preintervention approach to relationships. In particular, youths who, at baseline, had satisfactory, but not particularly strong, relationships benefited more from mentoring than did youths with profiles characterized by either strongly positive or negative relationships. Implications for research and practice are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
993.
Cristina Chiavari Carla Martini Lars-Gunnar Johansson Alf Åslund 《Corrosion Science》2008,50(9):2444-2455
The corrosion of lead-rich pipes in historical organs in different parts of Europe has been investigated. The influence of the environment and the composition and microstructure of the pipe metal was studied. Pipe corrosion was documented by visual inspection (boroscope). The corrosion attack and the composition and microstructure of the metal were characterized by OM, SEM, XRD, IC and FAAS. It is shown that the degree of corrosion of the pipes is correlated to the concentration of gaseous acetic and formic acid in the organ. The organic acids are emitted by the wood from which the wind system is built. It is also shown that pipe corrosion decreases with increasing tin content in the range 0-4% (wt). Possible conservation strategies are discussed. 相似文献
994.
Fast digestive,leucine‐rich,soluble milk proteins improve muscle protein anabolism,and mitochondrial function in undernourished old rats 下载免费PDF全文
995.
996.
Annalisa Chianese Carla Zannella Alessandra Monti Anna De Filippis Nunzianna Doti Gianluigi Franci Massimiliano Galdiero 《International journal of molecular sciences》2022,23(2)
Viral infections represent a serious threat to the world population and are becoming more frequent. The search and identification of broad-spectrum antiviral molecules is necessary to ensure new therapeutic options, since there is a limited availability of effective antiviral drugs able to eradicate viral infections, and consequently due to the increase of strains that are resistant to the most used drugs. Recently, several studies on antimicrobial peptides identified them as promising antiviral agents. In detail, amphibian skin secretions serve as a rich source of natural antimicrobial peptides. Their antibacterial and antifungal activities have been widely reported, but their exploitation as potential antiviral agents have yet to be fully investigated. In the present study, the antiviral activity of the peptide derived from the secretion of Rana tagoi, named AR-23, was evaluated against both DNA and RNA viruses, with or without envelope. Different assays were performed to identify in which step of the infectious cycle the peptide could act. AR-23 exhibited a greater inhibitory activity in the early stages of infection against both DNA (HSV-1) and RNA (MeV, HPIV-2, HCoV-229E, and SARS-CoV-2) enveloped viruses and, on the contrary, it was inactive against naked viruses (PV-1). Altogether, the results indicated AR-23 as a peptide with potential therapeutic effects against a wide variety of human viruses. 相似文献
997.
Adele Leggieri Chiara Attanasio Antonio Palladino Paolo de Girolamo Carla Lucini Livia DAngelo 《International journal of molecular sciences》2022,23(3)
Collagens are the most abundant proteins in vertebrates and constitute the major components of the extracellular matrix. Collagens play an important and multifaceted role in the development and functioning of the nervous system and undergo structural remodeling and quantitative modifications during aging. Here, we investigated the age-dependent regulation of col4a1 and col25a1 in the brain of the short-lived vertebrate Nothobranchius furzeri, a powerful model organism for aging research due to its natural fast-aging process and further characterized typical hallmarks of brain aging in this species. We showed that col4a1 and col25a1 are relatively well conserved during vertebrate evolution, and their expression significantly increases in the brain of N. furzeri upon aging. Noteworthy, we report that both col4a1 and col25a1 are expressed in cells with a neuronal phenotype, unlike what has already been documented in mammalian brain, in which only col25a1 is considered a neuronal marker, whereas col4a1 seems to be expressed only in endothelial cells. Overall, our findings encourage further investigation on the role of col4a1 and col25a1 in the biology of the vertebrate brain as well as the onset of aging and neurodegenerative diseases. 相似文献
998.
Direct detection of antibiotic resistance genes in specimens of chicken and pork meat 总被引:1,自引:0,他引:1
Garofalo C Vignaroli C Zandri G Aquilanti L Bordoni D Osimani A Clementi F Biavasco F 《International journal of food microbiology》2007,113(1):75-83
Antibiotic resistance (AR) in bacteria, a major threat to human health, has emerged in the last few decades as a consequence of the selective pressure exerted by the widespread use of antibiotics in medicine, agriculture and veterinary practice and as growth promoters in animal husbandry. The frequency of 11 genes [tet(M), tet(O), tet(K), erm(A), erm(B), erm(C), vanA, vanB, aac (6')-Ie aph (2')-Ia, mecA, blaZ] encoding resistance to some antibiotics widely used in clinical practice was analysed in raw pork and chicken meat and in fermented sausages as well as in faecal samples from the relevant farm animals using a molecular approach based on PCR amplification of bacterial DNA directly extracted from specimens. Some of the 11 AR genes were highly prevalent, the largest number being detected in chicken meat and pig faeces. The genes found most frequently in meat were tet(K) and erm(B); vanB and mecA were the least represented. All 11 determinants were detected in faecal samples except mecA, which was found only in chicken faeces. erm(B) and erm(C) were detected in all faecal samples. The frequency of AR genes was not appreciably different in meat compared to faecal specimens of the relevant animal except for vanB, which was more prevalent in faeces. Our findings suggest that AR genes are highly prevalent in food-associated bacteria and that AR contamination is likely related to breeding rather than processing techniques. Finally, the cultivation-independent molecular method used in this work to determine the prevalence of AR genes in foods proved to be a rapid and reliable alternative to traditional tools. 相似文献
999.
Marta S. Saraiva Newton L. Dias Filho Carla D. Nunes Pedro D. Vaz Teresa G. Nunes Maria José Calhorda 《Microporous and mesoporous materials》2009,117(3):670-677
[Mo(η3-C3H5)X(CO)2(NCCH3)2] (X = Br, 1a; X = Cl, 1b) complexes reacted with the bidentate ligand RNC(Ph)–C(Ph)NR, R = (CH2)2CH3 (DAB, 2) affording [Mo(η3-C3H5)X(CO)2(DAB)] (X = Br, 4a; X = Cl, 4b), which were characterized by elemental analysis, FTIR and 1H and 13C NMR spectroscopy. The modified silylated ligand RNC(Ph)C(Ph)NR, R = (CH2)3Si(OCH2CH3)3 (DAB–Si, 3), was used to immobilize the two complexes in MCM-41 (MCM) mesoporous silica. The new materials were characterized by powder X-ray diffraction, N2 adsorption analysis, FTIR and 29Si and 13C CPMAS solid state NMR spectroscopy. Both the materials and the complexes were tested in the oxidation of cyclooctene and styrene and behaved as active catalyst precursors for cyclooctene and styrene epoxidation with TBHP (t-butylhydroperoxide), leading selectively to epoxides with high conversions and TOFs. Although the homogeneous systems reach 100% conversion of cyclooctene and slightly less for styrene, the loss of catalytic activity in the heterogeneous systems is small, with a 98% conversion of styrene achieved by the chloride containing material. 相似文献
1000.
A new polymeric solid electrolyte based on a PEO/PMVE-MAc blend, complexed with LiClO4, was obtained and characterized by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), polarized light optical microscopy, electrochemical impedance and cyclic voltammetry. DSC traces indicated miscibility for all the PSE samples. Crystallinity was suppressed for samples with LiClO4 concentrations higher than 2.5 wt%. FTIR associated with DSC studies indicated that there is a preferential formation of complexes PEO/Li+/PMVE-MAc in all PSE samples studied here. The ionic conductivity of PSE reaches a maximum of about 10−5 S/cm at ambient temperature and 7.5 wt% LiClO4. The electrochemical stability window is 4.5 V and associated with the other characteristics, make the PSE studied here suitable for applications in ‘smart-windows’, batteries, sensors, etc. 相似文献