全文获取类型
收费全文 | 1989篇 |
免费 | 155篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 13篇 |
综合类 | 1篇 |
化学工业 | 790篇 |
金属工艺 | 25篇 |
机械仪表 | 42篇 |
建筑科学 | 75篇 |
矿业工程 | 1篇 |
能源动力 | 59篇 |
轻工业 | 414篇 |
水利工程 | 17篇 |
石油天然气 | 7篇 |
无线电 | 100篇 |
一般工业技术 | 235篇 |
冶金工业 | 119篇 |
原子能技术 | 7篇 |
自动化技术 | 241篇 |
出版年
2024年 | 5篇 |
2023年 | 31篇 |
2022年 | 192篇 |
2021年 | 187篇 |
2020年 | 85篇 |
2019年 | 71篇 |
2018年 | 76篇 |
2017年 | 77篇 |
2016年 | 77篇 |
2015年 | 71篇 |
2014年 | 89篇 |
2013年 | 142篇 |
2012年 | 132篇 |
2011年 | 148篇 |
2010年 | 92篇 |
2009年 | 77篇 |
2008年 | 77篇 |
2007年 | 64篇 |
2006年 | 68篇 |
2005年 | 50篇 |
2004年 | 42篇 |
2003年 | 51篇 |
2002年 | 40篇 |
2001年 | 18篇 |
2000年 | 26篇 |
1999年 | 20篇 |
1998年 | 32篇 |
1997年 | 21篇 |
1996年 | 12篇 |
1995年 | 8篇 |
1994年 | 8篇 |
1993年 | 9篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1976年 | 5篇 |
1975年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有2146条查询结果,搜索用时 15 毫秒
991.
Totan Alexandra Imre Melescanu Marina Miricescu Daniela Stanescu Iulia Ioana BencZe Maria Radulescu Radu Tancu Ana Maria Spinu Tudor Greabu Maria 《International journal of molecular sciences》2020,21(23)
The duration of denture use, oral hygiene, smoking and male sex were identified as risk factors for oral mucosal lesions. As it is well known, all the oral mucosal lesions associated with risk factors have an important degree of malignity. Chronic mechanical irritation can be another cause of oral cancer and it is produced by the constant action of a deleterious agent from the oral cavity. Autophagy represents a complex evolutionary conserved catabolic process in which cells self-digest intracellular organelles in order to regulate their normal turnover and remove the damaged ones with compromised function to further maintain homeostasis. Autophagy is modulated by mTOR kinase and indirectly by PI3K/AKT survival pathway. Due to its dual capacity to either induce cell death or promote cell survival, important evidence pointed that autophagy has a two-faced role in response to chemotherapy in cancer. In conclusion, understanding how to overcome cytoprotective autophagy and how to take advantage of autophagic cell death is critical in order to enhance the cancer cells sensitivity to particular therapeutic agents. 相似文献
992.
Reliability of molecular weight determination methods for oligomers investigated using certified polystyrene reference materials 总被引:1,自引:0,他引:1
Takeshi Saito Marina A. Lusenkova Kayori Shimada Kana Kishine Shinichi Kinugasa 《Polymer》2004,45(25):8355-8365
Using polystyrene certified reference materials (CRMs) whose molecular weights range from 500 to 2400, we investigated the reliability of molecular weight determination by size-exclusion chromatography (SEC), SEC coupled with multi-angle light scattering detection (SEC-MALS), conventional static light scattering (SLS), matrix-assisted laser desorption/inonization time-of-flight mass spectrometry (MALDI-TOFMS), and 1H NMR. Average molecular weights determined by these methods were compared with the certified values which were determined by supercritical fluids chromatography with relative standard uncertainty less than 1%. The comparison showed that recent SEC with calibration constructed by uniform polystyrenes can provide just the same average molecular weights as certified ones within the standard uncertainty. 1H NMR was also found to be a powerful technique to determine number-average molecular weight accurately. Average molecular weights measured by SEC-MALS and SLS nearly agreed with certified values except for lower molecular weights. Although MALDI-TOFMS provided average molecular weights in agreement with certified values, the polydispersity given by MALDI-TOFMS were found to be very small for all the polystyrenes. 相似文献
993.
David Villanueva Bermejo Pilar Luna Marina S. Manic Vesna Najdanovic-Visak Guillermo Reglero Tiziana Fornari 《Food and Bioproducts Processing》2013,91(4):303-309
This paper reports experimental data on the pressurized liquid extraction of caffeine from green coffee beans and green tea leaves using ethyl lactate (ethyl 2-hydroxy-propanoate). This solvent is a new bio-renewable agrochemical solvent, naturally produced by fermentation from corn derived feedstock, which has been recently considered as a very suitable and environmental benign solvent for food industrial applications.Static extraction assays (one step during 10 min) were carried out in an Accelerated solvent extraction (ASE) system at three different extraction temperatures, namely 100, 150 and 200 °C. Extraction yield and caffeine recovery were determined and compared with those obtained when using other liquid solvents, such as ethyl acetate or ethanol. High recovery of caffeine (≈60%) was found in the extracts produced using ethyl lactate, which demonstrates the potential use of this green solvent for the extraction of caffeine from different vegetable sources. 相似文献
994.
Francisco Cabrera-Chávez Josafat Marina Ezquerra-Brauer Ronaldo Herrera-Urbina Cristina M. Rosell 《International Journal of Food Properties》2013,16(6):1187-1198
The effect of semi-purified trypsin on the physicochemical properties of durum and bread wheat flour and gluten protein fractions was evaluated. Trypsin was partially isolated from sierra (Scomberomorus sierra) guts extracts by affinity chromatography. Treatment with enzyme caused hydrolysis of 1.16–1.40% in both durum and bread wheat gluten and gluten fractions. The effect of hydrolysis on the isoelectric point was more evident in durum that bread wheat gluten. Addition of the trypsin-like enzyme at three different concentrations induced a decrease in the gluten index. The dough consistency fell after 1.5 h of incubation. It was possible to modify wheat flour proteins by varying S. sierra trypsin-like enzyme concentration and incubation time, depending on the wheat species. 相似文献
995.
Libero DamenMariachiara Lazzari Marina Mastragostino 《Journal of power sources》2011,196(20):8692-8695
A lithium-ion battery featuring graphite anode, LiFePO4-C cathode and an innovative, safe, ionic liquid-based electrolyte, was assembled and characterized in terms of specific energy and power after the USABC-DOE protocol for power-assist hybrid electric vehicle (HEV) application. The test results show that the battery surpasses the energy and power goals stated by USABC-DOE and, hence, this safe lithium-ion battery should be suitable for application in the evolving HEV market. 相似文献
996.
Dr. Maria Antonietta Dettori Dr. Marina Pisano Dr. Carla Rozzo Dr. Giovanna Delogu Dr. Davide Fabbri 《ChemMedChem》2021,16(6):1022-1033
A small collection of C2-symmetric hydroxylated biphenyl derivatives featuring an α,β-unsaturated ketone as a lead structure was prepared, and the capacity of these compounds to act as antiproliferative agents against four human malignant melanoma cell lines was assayed. The prodrug approach was applied in order to improve the delivery of compounds into the cell by modulation of the phenolic hydroxy protecting group. The hydroxylated biphenyl structure bearing an α,β-unsaturated ketone and a phenolic-O-prenylated chain was found to facilitate the delivery of the molecule and interactions with biological targets. Four compounds showed antiproliferative activity resulting in IC50 values in the range of 1.2 to 2.8 μM. 相似文献
997.
Ruth Klendauer Marina Berkovich Richard Gelvin Jan Marco Leimeister Helmut Krcmar 《Information Systems Journal》2012,22(6):475-503
Requirements engineering is a software development discipline, executed by requirements analysts (RAs), that includes requirements elicitation, analysis, specification and validation. Its successful outcome is very often essential to overall project success. However, there is a lack of systematically conducted empirical research on the competencies of RAs. This paper addressed this gap by conducting 64 interviews at eight major North American and European financial services companies. Our qualitative research design follows an interpretive approach and uses critical incident technique. We develop a competency model, which specifies 16 critical competencies, and integrates contextual and situational factors as well as results variables. ‘Consulting others’, ‘Testing assumptions and investigating’ and ‘Explaining concepts and opinions’ were the most frequently identified competencies. This indicates that for an effective analyst, close interaction and communication with customers is indeed crucial – but of equally importance is the critical questioning of the expressed needs. Surprisingly, applying specific tools and advanced techniques did not seem to play a significant role from the interviewees' perspective. This study contributes to theory as it is the first to elaborate a competency model for RAs. It also provides a foundation for the development of competency‐based training in companies and universities. 相似文献
998.
Mirit Kolet Daniel Zerbib Karen Molina Dr. Faina Nakonechny Prof. Marina Nisnevitch 《Israel journal of chemistry》2020,60(5-6):644-651
Biodiesel can be produced by transesterification of oil triglycerides, as well as by esterification of fatty acids using feedstock materials rich in free fatty acids)FFAs). Utilization of such feedstocks can gain substantial economical profit and solve a problem of disposal of residual raw materials. To find an effective method of biodiesel production from FFA, we developed esterification of FFAs under ultrasonic activation using Lewis acids as catalysts. Homologous catalyst BF3 and heterogeneous AlCl3 were highly effective in reactions of model FFAs methylation under ultrasonic activation, when the reaction yield reached 100 %. Ethylation at the same conditions was less successful. 相似文献
999.
Ghoumid Kamal Ghadban Amina Boukricha Sokaina Ar-reyouchi El Miloud Yahiaoui Reda Mekaoui Slimane Raschetti Marina Lepers Catherine 《Telecommunication Systems》2020,73(3):433-441
Telecommunication Systems - Optical code division multiple access (OCDMA) systems are attracting an increasing interest in optical fiber communication. This is due to the various advantages that... 相似文献
1000.
Angel Edgardo Tapia-Vasquez Josafat Marina Ezquerra-Brauer Enrique Márquez-Ríos Juan Carlos Ramírez-Suárez José Ángel Huerta-Ocampo Hisila Santacruz-Ortega Wilfrido Torres-Arreola 《International Journal of Food Science & Technology》2020,55(10):3246-3253
To perform improvements in food science, it is fundamental to understand the physicochemical properties of proteins since their interaction with other macromolecules plays an essential role in food systems. Collagen and paramyosin help in the maintenance of the matrix structure cells, the textural behaviour and the technical functionality of the protein concentrates; because of this, their identification and characterisation are necessary. Cephalopods species have shown differences in the distribution of its muscle fibres. The amino acid profile of jumbo squid showed a high content of glycine and hydroxyproline, while octopus showed a high content of acidic amino acids. The thermal profile of jumbo squid showed an endothermic transition at 117 °C, which octopus did not present. Moreover, the proteomic identification confirms the identity of paramyosin with 33% coverage to paramyosin from Dosidicus gigas and a 4% coverage to collagen type II from Sepia pharaonis on octopus and jumbo squid, respectively. 相似文献