首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   404篇
  免费   9篇
电工技术   3篇
综合类   3篇
化学工业   136篇
金属工艺   5篇
机械仪表   2篇
建筑科学   27篇
能源动力   9篇
轻工业   91篇
水利工程   2篇
无线电   23篇
一般工业技术   47篇
冶金工业   18篇
自动化技术   47篇
  2023年   3篇
  2022年   21篇
  2021年   18篇
  2020年   9篇
  2019年   5篇
  2018年   8篇
  2017年   3篇
  2016年   4篇
  2015年   9篇
  2014年   18篇
  2013年   18篇
  2012年   17篇
  2011年   24篇
  2010年   20篇
  2009年   19篇
  2008年   27篇
  2007年   16篇
  2006年   12篇
  2005年   7篇
  2004年   14篇
  2003年   9篇
  2002年   10篇
  2001年   10篇
  2000年   5篇
  1998年   9篇
  1997年   7篇
  1996年   5篇
  1994年   6篇
  1993年   5篇
  1992年   2篇
  1991年   6篇
  1989年   4篇
  1985年   3篇
  1982年   5篇
  1979年   2篇
  1978年   2篇
  1977年   2篇
  1975年   2篇
  1974年   3篇
  1964年   2篇
  1957年   5篇
  1956年   2篇
  1955年   14篇
  1954年   4篇
  1940年   1篇
  1938年   3篇
  1934年   2篇
  1932年   1篇
  1931年   1篇
  1930年   1篇
排序方式: 共有413条查询结果,搜索用时 10 毫秒
1.
2.
A semiconductor-based master-oscillator power-amplifier operating at 977 nm is demonstrated to emit more than 10 W continuous wave in a nearly diffraction limited beam with a narrow spectral bandwidth. The device consists of a distributed Bragg reflector laser and a flared amplifier monolithically integrated on a single chip  相似文献   
3.
Sucrose carboxylic acid polyesters are in dependence of the degree of acylation and fatty acid composition more or less undigestible or emulsifying fat substitutes and functional additives for foods. In this connection the relationships between their molecular parameters and functional properties are discussed. New procedures of the solvent-free synthesis are presented. Furthermore, open biochemical and toxicological problems of pinocytosis and accumulation of intact polyesters in organs and tissue being still under investigations are considered.  相似文献   
4.
Summary The rates of polymerization of alpha and beta eleostearates agree with second order kinetics, as would be expected for a bimolecular Diels-Alder addition. The all-trans, beta isomer reacts faster than thecis, trans, trans alpha isomer, in agreement with knowncis, trans effects on diene activity. The polymerization of normal linoleate follows an apparent first order reaction. It is suggested that conjugation is the slow rate determining monomolecular reaction, as has been proposed for the non-conjugated linoleate isomers. Paper No. 177, Journal Series, Research Laboratories, General Mills Inc. Presented at the 28th fall (Paul Bunyan) meeting of the American Oil Chemists’' Society, Oct. 12, 1954, Minneapolis, Minn.  相似文献   
5.
Summary Horizontal SDS electrophoresis of 18 legume seed protein extracts was performed in ultrathin-layer polyacrylamide gels on foil supports. Separation results of the SD S pore gradient electrophoresis (T=4–22.5%) are compared to those of SDS electrophoresis in a constant pore size gel (T=10%). Resolution as well as the sensitivity (0.1 g protein per band) of the ultrathin-layer SDS pore-gradient electrophoresis were extremely high. Because of the very low gel thickness, separation, staining and drying were completed in substantially shorter times than achieved with conventional thick gels. An easy technique for casting ultrathin-layer (360 gm) concave gradient gels for 10 cm separation distance and a width of 25 cm is described. The even distribution of the concave exponential pore-gradient over the whole gel width is demonstrated. Molecular weights of the legume proteins are detected from 5,000 to 110,000 daltons. The protein patterns are genus- and species-specific.
Horizontale Ultradünnschicht SDS-Gradientengel-Elektrophorese von Leguminosensamenproteinen
Zusammenfassung Die ausgezeichnete Trennschärfe der horizontalen Ultradünnschicht-SDS-Gradienten-gel Elektrophorese wird am Beispiel von Samenproteinen 18 verschiedener Leguminosengattungen, -arten und -sorten gezeigt. Es werden die Trennergebnisse der SDS-Elektrophorese mit Gelgradienten (T=4-22,5%) bzw. mit Gelen konstanter Porengröße (T=10%) verglichen. Das höchste Auslösungsvermögen und die beste Trennschärfe zeigen ultradünne Gradientengele. Die Nachweisempfindlichkeit ist bei allen Ultradünn-schicht-SDS-Elektrophoresen sehr hoch (0,1 g Protein/Bande). Da die auf Folie polymerisierten Gele sehr dünn sind (360 m) kann mit wesentlich verkürzten Trenn-, Färbe-, Entfärbe- und Trocknungszeiten gear-beitet werden. Es wird eine einfache Herstellung ultradünner Polyacrylamidgele mit exponentiellen konkaven Gradienten für die Trenndistanz von 10 cm mit einer Breite von 25 cm beschrieben. Die gerade und gleichmäßige Verteilung des Gradienten über die gesamte Gelbreite wird gezeigt. Mit der beschriebenen Methode werden bei den untersuchten Leguminosen-proteinen Molekulargewichte von 5 000 his 110 000 Dalton gefunden. Die Proteinmuster erweisen sich als gattungs- und artspezifisch.
  相似文献   
6.
Purified Brassica napus enoyl acyl carrier protein reductase (ENR) was used to select specific antibodies from a library of antibody fragments, single-chain Fv (scFv), displayed on filamentous phage. Analysis of the selected clones by BstNl fingerprinting and nucleotide sequencing showed that the scFv were derived from three different human VH germline genes. The binding specificities were confirmed by Western blots and ELISA. The scFv preparations reacted with B. napus ENR, but not with β-keto reductase, nor enoyl reductase from Escherichia coli. Analysis of fragments generated by CNBr treatment indicates that the scFv 3.13 recognizes an epitope located within the n-terminal 80 amino acids of the enzyme molecule. The scFv were used to detect ENR directly in extracts of B. napus seeds.  相似文献   
7.
8.
Nanoparticles of metal–organic frameworks (MOF NPs) are crystalline hybrid micro- or mesoporous nanomaterials that show great promise in biomedicine due to their significant drug loading ability and controlled release. Herein, we develop porous capsules from aggregate of nanoparticles of the iron carboxylate MIL-100(Fe) through a low-temperature spray-drying route. This enables the concomitant one-pot encapsulation of high loading of an antitumor drug, methotrexate, within the pores of the MOF NPs, and the collagenase enzyme (COL), inside the inter-particular mesoporous cavities, upon the formation of the capsule, enhancing tumor treatment. This association provides better control of the release of the active moieties, MTX and collagenase, in simulated body fluid conditions in comparison with the bare MOF NPs. In addition, the loaded MIL-100 capsules present, against the A-375 cancer cell line, selective toxicity nine times higher than for the normal HaCaT cells, suggesting that MTX@COL@MIL-100 capsules may have potential application in the selective treatment of cancer cells. We highlight that an appropriate level of collagenase activity remained after encapsulation using the spray dryer equipment. Therefore, this work describes a novel application of MOF-based capsules as a dual drug delivery system for cancer treatment.  相似文献   
9.
Background: Severe outcomes of COVID-19 account for up to 15% of all cases. The study aims to check if any gene variants related to cardiovascular (CVD) and pulmonary diseases (PD) are correlated with a severe outcome of COVID-19 in a Polish cohort of COVID-19 patients. Methods: In this study, a subset of 747 samples from unrelated individuals collected across Poland in 2020 and 2021 was used and whole-genome sequencing was performed. Results: The GWAS analysis of SNPs and short indels located in genes related to CVD identified one variant significant in COVID-19 severe outcome in the HADHA gene, while for the PD gene panel, we found two significant variants in the DRC1 gene. In this study, both potentially protective and risk variants were identified, of which variants in the HADHA gene deserve the most attention. Conclusions: This is the first study reporting the association between the HADHA and DRC1 genetic variants and COVID-19 severe outcome based on the cohort WGS analysis. Although all the identified variants are localised in introns, they may be correlated and therefore inherited along with other risk variants, potentially causative to severe outcome of COVID-19 but not discovered yet.  相似文献   
10.
Determination of residual amounts of pesticides and polychlorinated biphenyls (PCBs) in food samples requires the use of specific techniques regarding sample preparation as well as instrumental analysis which should be characterized by a very low detection limit. A problem associated with the use of pesticides and PCBs is the need for controlling their residues in the environment, particularly in food, as these chemicals show a propensity to accumulate. The analysis of food samples for the presence of pesticides and PCBs brings on many difficulties because of the specificity of sample preparation consisting of multistep purification procedures of samples that contain trace amounts of an analyte. Concentration determinations of pollutants that easily dissolve in complex matrices, particularly in the presence of a large apportionment of interfering substances, pose a big challenge. Therefore, the basic step in food analysis for the presence of pesticides and PCBs is sample preparation which mainly consists of analyte enrichment and the removal of interfering substances. But all steps of the analytical procedure that include sample collection and preparation, extraction of analytes from matrix, extract purification, and final determination, are very significant; their precision and correct application have a decisive effect on the final result.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号