全文获取类型
收费全文 | 3319篇 |
免费 | 242篇 |
专业分类
电工技术 | 39篇 |
综合类 | 1篇 |
化学工业 | 973篇 |
金属工艺 | 28篇 |
机械仪表 | 49篇 |
建筑科学 | 118篇 |
矿业工程 | 8篇 |
能源动力 | 66篇 |
轻工业 | 865篇 |
水利工程 | 22篇 |
石油天然气 | 21篇 |
无线电 | 184篇 |
一般工业技术 | 447篇 |
冶金工业 | 312篇 |
原子能技术 | 13篇 |
自动化技术 | 415篇 |
出版年
2024年 | 5篇 |
2023年 | 23篇 |
2022年 | 140篇 |
2021年 | 149篇 |
2020年 | 84篇 |
2019年 | 81篇 |
2018年 | 94篇 |
2017年 | 107篇 |
2016年 | 119篇 |
2015年 | 95篇 |
2014年 | 138篇 |
2013年 | 236篇 |
2012年 | 195篇 |
2011年 | 267篇 |
2010年 | 167篇 |
2009年 | 186篇 |
2008年 | 194篇 |
2007年 | 167篇 |
2006年 | 117篇 |
2005年 | 111篇 |
2004年 | 96篇 |
2003年 | 100篇 |
2002年 | 75篇 |
2001年 | 49篇 |
2000年 | 39篇 |
1999年 | 42篇 |
1998年 | 80篇 |
1997年 | 60篇 |
1996年 | 51篇 |
1995年 | 37篇 |
1994年 | 44篇 |
1993年 | 40篇 |
1992年 | 17篇 |
1991年 | 14篇 |
1990年 | 12篇 |
1989年 | 14篇 |
1988年 | 18篇 |
1987年 | 7篇 |
1986年 | 10篇 |
1985年 | 11篇 |
1984年 | 11篇 |
1983年 | 11篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1977年 | 10篇 |
1976年 | 6篇 |
1974年 | 2篇 |
排序方式: 共有3561条查询结果,搜索用时 15 毫秒
991.
Miguel A Fernndez-Muío M Teresa Sancho Soledad Muniategui Jos F Huidobro M Pilar Snchez Jesús Simal-Lozano 《Journal of the science of food and agriculture》1996,71(2):141-144
The glycerol content of honey has been determined using a Boehringer Mannheim enzymatic method simplified for this purpose. The solution of honey was employed directly, without clarification and without addition of NaOH solution. With these conditions, there were no observed interference effects. It is necessary to use a 1·5 ml micro-cuvette. The enzymatic determination was measured spectrophotometrically at 365 nm using the enzymes in quadruple the quantities recommended by the supplier. The method combines precision, good recovery, sensitivity, simplicity and low cost. 相似文献
992.
Juan Gil Salvador Nadal Diego Luna M Teresa Moreno Antonio De Haro 《Journal of the science of food and agriculture》1996,71(2):179-184
A collection of 50 chickpea accessions (26 kabuli and 24 desi types) was evaluated for 2 years for eight physico-chemical seed characters: 100-seed weight, hydration capacity, hydration index, coat thickness and contents of protein, oil, acid detergent fibre (ADF) and starch. Significant differences were found between desi and kabuli types for the majority of the characters. The variance component due to the genotype×year interaction was important for the hydration index, starch and protein content, showing the importance of the year effect on genotypic expression of these characters. One kabuli accession and five desi accessions with high and stable protein content were selected. There was no overlap between the variation limits of desi and kabuli for coat thickness and ADF content. There were high positive and significant correlations between seed weight and oil content for both types of chickpea. 相似文献
993.
M H Malogolowkin R S Horowitz J A Ortega S E Siegel G D Hammond J M Weiner 《Computers and biomedical research》1989,22(2):190-208
This paper describes a method for the analysis of the clinical trial design process used by experts. With this procedure, the scientific ideas and their sources can be identified and related to the clinical trial protocol actually prepared by the experts. An example is given using the work of the Intergroup Rhabdomyosarcoma Study Committee (IRS). That committee has been the primary contributor of information dealing with the treatment of rhabdomyosarcoma in children. The IRS-III protocol was used in this analysis of expert behavior because the protocol was adopted by the leading pediatric oncology clinical trial groups in North America and Europe. The analysis showed that the experts rely heavily, for much of the design, on ideas presented in numerical displays in published documents. Further, those aspects of the design which are innovative can be traced and better understood by applying the new procedure. 相似文献
994.
Valentina Peluso Laura Rinaldi Teresa Russo Olimpia Oliviero Anna Di Vito Corrado Garbi Amerigo Giudice Roberto De Santis Antonio Gloria Vincenzo DAnt 《International journal of molecular sciences》2022,23(1)
The aim of this study was to evaluate the effect of a time-dependent magnetic field on the biological performance of periodontal ligament stem cells (PDLSCs). A Western blot analysis and Alamar Blue assay were performed to investigate the proliferative capacity of magnetically stimulated PDLSCs (PDLSCs MAG) through the study of the MAPK cascade (p-ERK1/2). The observation of ALP levels allowed the evaluation of the effect of the magnetic field on osteogenic differentiation. Metabolomics data, such as oxygen consumption rate (OCR), extracellular acidification rate (ECAR) and ATP production provided an overview of the PDLSCs MAG metabolic state. Moreover, the mitochondrial state was investigated through confocal laser scanning microscopy. Results showed a good viability for PDLSCs MAG. Magnetic stimulation can activate the ERK phosphorylation more than the FGF factor alone by promoting a better cell proliferation. Osteogenic differentiation was more effectively induced by magnetic stimulation. The metabolic panel indicated significant changes in the mitochondrial cellular respiration of PDLSCs MAG. The results suggested that periodontal ligament stem cells (PDLSCs) can respond to biophysical stimuli such as a time-dependent magnetic field, which is able to induce changes in cell proliferation and differentiation. Moreover, the magnetic stimulation also produced an effect on the cell metabolic profile. Therefore, the current study demonstrated that a time-dependent magnetic stimulation may improve the regenerative properties of PDLSCs. 相似文献
995.
Inmaculada Ribera-Cortada Jos Guerrero-Pineda Isabel Trias Luis Veloza Adriana Garcia Lorena Marimon Sherley Diaz-Mercedes Jos Ramon Alamo Maria Teresa Rodrigo-Calvo Naiara Vega Ricardo Lpez del Campo Rafael Parra-Medina Tarek Ajami Antonio Martínez Oscar Reig Maria J. Ribal Juan Manuel Corral-Molina Pedro Jares Jaume Ordi Natalia Rakislova 《International journal of molecular sciences》2022,23(1)
Penile squamous cell carcinoma (PSCC) is a rare but aggressive neoplasm with dual pathogenesis (human papillomavirus (HPV)-associated and HPV-independent). The development of targeted treatment is hindered by poor knowledge of the molecular landscape of PSCC. We performed a thorough review of genetic alterations of PSCC focused on somatic mutations and/or copy number alterations. A total of seven articles have been identified which, overall, include 268 PSCC. However, the series are heterogeneous regarding methodologies employed for DNA sequencing and HPV detection together with HPV prevalence, and include, in general, a limited number of cases, which results in markedly different findings. Reported top-ranked mutations involve TP53, CDKN2A, FAT1, NOTCH-1 and PIK3CA. Numerical alterations involve gains in MYC and EGFR, as well as amplifications in HPV integration loci. A few genes including TP53, CDKN2A, PIK3CA and CCND1 harbor both somatic mutations and copy number alterations. Notch, RTK-RAS and Hippo pathways are frequently deregulated. Nevertheless, the relevance of the identified alterations, their role in signaling pathways or their association with HPV status remain elusive. Combined targeting of different pathways might represent a valid therapeutic approach in PSCC. This work calls for large-scale sequencing studies with robust HPV testing to improve the genomic understanding of PSCC. 相似文献
996.
Raquel V. Barrulas Clara Lpez-Iglesias Marcileia Zanatta Teresa Casimiro Gonzalo Mrmol Manuela Ribeiro Carrott Carlos A. García-Gonzlez Marta C. Corvo 《International journal of molecular sciences》2022,23(1)
CO2 levels in the atmosphere are increasing exponentially. The current climate change effects motivate an urgent need for new and sustainable materials to capture CO2. Porous materials are particularly interesting for processes that take place near atmospheric pressure. However, materials design should not only consider the morphology, but also the chemical identity of the CO2 sorbent to enhance the affinity towards CO2. Poly(ionic liquid)s (PILs) can enhance CO2 sorption capacity, but tailoring the porosity is still a challenge. Aerogel’s properties grant production strategies that ensure a porosity control. In this work, we joined both worlds, PILs and aerogels, to produce a sustainable CO2 sorbent. PIL-chitosan aerogels (AEROPILs) in the form of beads were successfully obtained with high porosity (94.6–97.0%) and surface areas (270–744 m2/g). AEROPILs were applied for the first time as CO2 sorbents. The combination of PILs with chitosan aerogels generally increased the CO2 sorption capability of these materials, being the maximum CO2 capture capacity obtained (0.70 mmol g−1, at 25 °C and 1 bar) for the CHT:P[DADMA]Cl30% AEROPIL. 相似文献
997.
Piotr
witek Teresa Glomb Agnieszka Dobosz Tomasz Gbarowski Kamil Wojtkowiak Aneta Jezierska Jarosaw J. Panek Magorzata
witek Magorzata Strzelecka 《International journal of molecular sciences》2022,23(1)
To date, chronic inflammation is involved in most main human pathologies such as cancer, and autoimmune, cardiovascular or neurodegenerative disorders. Studies suggest that different prostanoids, especially prostaglandin E2, and their own synthase (cyclooxygenase enzyme-COX) can promote tumor growth by activating signaling pathways which control cell proliferation, migration, apoptosis, and angiogenesis. Non-steroidal anti-inflammatory drugs (NSAIDs) are used, alongside corticosteroids, to treat inflammatory symptoms particularly in all chronic diseases. However, their toxicity from COX inhibition and the suppression of physiologically important prostaglandins limits their use. Therefore, in continuation of our efforts in the development of potent, safe, non-toxic chemopreventive compounds, we report herein the design, synthesis, biological evaluation of new series of Schiff base-type hybrid compounds containing differently substituted N-acyl hydrazone moieties, 1,3,4-oxadiazole ring, and 4,6-dimethylpyridine core. The anti-COX-1/COX-2, antioxidant and anticancer activities were studied. Schiff base 13, containing 2-bromobenzylidene residue inhibited the activity of both isoenzymes, COX-1 and COX-2 at a lower concentration than standard drugs, and its COX-2/COX-1 selectivity ratio was similar to meloxicam. Furthermore, the results of cytotoxicity assay indicated that all of the tested compounds exhibited potent anti-cancer activity against A549, MCF-7, LoVo, and LoVo/Dx cell lines, compared with piroxicam and meloxicam. Moreover, our experimental study was supported by density functional theory (DFT) and molecular docking to describe the binding mode of new structures to cyclooxygenase. 相似文献
998.
Kayla Kauffman Courtney S. Werner Georgia Titcomb Michelle Pender Jean Yves Rabezara James P. Herrera Julie Teresa Shapiro Alma Solis Voahangy Soarimalala Pablo Tortosa Randall Kramer James Moody Peter J. Mucha Charles Nunn 《Journal of the Royal Society Interface》2022,19(186)
Social and spatial network analysis is an important approach for investigating infectious disease transmission, especially for pathogens transmitted directly between individuals or via environmental reservoirs. Given the diversity of ways to construct networks, however, it remains unclear how well networks constructed from different data types effectively capture transmission potential. We used empirical networks from a population in rural Madagascar to compare social network survey and spatial data-based networks of the same individuals. Close contact and environmental pathogen transmission pathways were modelled with the spatial data. We found that naming social partners during the surveys predicted higher close-contact rates and the proportion of environmental overlap on the spatial data-based networks. The spatial networks captured many strong and weak connections that were missed using social network surveys alone. Across networks, we found weak correlations among centrality measures (a proxy for superspreading potential). We conclude that social network surveys provide important scaffolding for understanding disease transmission pathways but miss contact-specific heterogeneities revealed by spatial data. Our analyses also highlight that the superspreading potential of individuals may vary across transmission modes. We provide detailed methods to construct networks for close-contact transmission pathogens when not all individuals simultaneously wear GPS trackers. 相似文献
999.
Teresa M. Dunn Dale Haak Erin Monaghan Troy J. Beeler 《Yeast (Chichester, England)》1998,14(4):311-321
Saccharomyces cerevisiae mutants lacking Scs7p fail to accumulate the inositolphosphorylceramide (IPC) species, IPC-C, which is the predominant form found in wild-type cells. Instead scs7 mutants accumulate an IPC-B species believed to be unhydroxylated on the amide-linked C26-fatty acid. Elimination of the SCS7 gene suppresses the Ca2+-sensitive phenotype of csg1 and csg2 mutants. The CSG1 and CSG2 genes are required for mannosylation of IPC-C and accumulation of IPC-C by the csg mutants renders them Ca2+-sensitive. The SCS7 gene encodes a protein that contains both a cytochrome b5-like domain and a domain that resembles the family of cytochrome b5-dependent enzymes that use iron and oxygen to catalyse desaturation or hydroxylation of fatty acids and sterols. Scs7p is therefore likely to be the enzyme that hydroxylates the C26-fatty acid of IPC-C. © 1998 John Wiley & Sons, Ltd. 相似文献
1000.
Gema Cabrera Teresa Linares Maria Elena de la Calle Domingo Cantero Antonio Valle Jorge Bolivar 《International journal of molecular sciences》2020,21(22)
D-DIBOA (4-hydroxy-(2H)-1,4-benzoxazin-3-(4H)-one) is an allelopathic-derived compound with interesting herbicidal, fungicidal, and insecticide properties whose production has been successfully achieved by biocatalysis using a genetically engineered Escherichia coli strain. However, improvement and scaling-up of this process are hampered by the current methodology for D-DIBOA quantification, which is based on high-performance liquid chromatographic (HPLC), a time-consuming technique that requires expensive equipment and the use of environmentally unsafe solvents. In this work, we established and validated a rapid, simple, and sensitive spectrophotometric method for the quantification of the D-DIBOA produced by whole-cell biocatalysis, with limits of detection and quantification of 0.0165 and 0.0501 µmol·mL−1 respectively. This analysis takes place in only a few seconds and can be carried out using 100 µL of the sample in a microtiter plate reader. We performed several whole-cell biocatalysis strategies to optimize the process by monitoring D-DIBOA production every hour to keep control of both precursor and D-DIBOA concentrations in the bioreactor. These experiments allowed increasing the D-DIBOA production from the previously reported 5.01 mM up to 7.17 mM (43% increase). This methodology will facilitate processes such as the optimization of the biocatalyst, the scaling up, and the downstream purification. 相似文献