全文获取类型
收费全文 | 262篇 |
免费 | 19篇 |
专业分类
电工技术 | 3篇 |
综合类 | 13篇 |
化学工业 | 110篇 |
金属工艺 | 2篇 |
机械仪表 | 9篇 |
建筑科学 | 10篇 |
能源动力 | 2篇 |
轻工业 | 35篇 |
水利工程 | 2篇 |
无线电 | 13篇 |
一般工业技术 | 45篇 |
冶金工业 | 19篇 |
自动化技术 | 18篇 |
出版年
2023年 | 4篇 |
2022年 | 12篇 |
2021年 | 23篇 |
2020年 | 9篇 |
2019年 | 10篇 |
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 11篇 |
2015年 | 11篇 |
2014年 | 9篇 |
2013年 | 24篇 |
2012年 | 15篇 |
2011年 | 16篇 |
2010年 | 19篇 |
2009年 | 10篇 |
2008年 | 19篇 |
2007年 | 9篇 |
2006年 | 5篇 |
2005年 | 9篇 |
2004年 | 6篇 |
2003年 | 8篇 |
2002年 | 6篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1934年 | 1篇 |
排序方式: 共有281条查询结果,搜索用时 15 毫秒
141.
Beatrica Sevcikova Bronislava Rezuchova Vladimira Mazurakova Dagmar Homerova Renata Novakova Lubomira Feckova Jan Kormanec 《International journal of molecular sciences》2021,22(15)
In contrast to Bacillus subtilis, Streptomyces coelicolor A3(2) contains nine homologues of stress response sigma factor SigB with a major role in differentiation and osmotic stress response. The aim of this study was to further characterize these SigB homologues. We previously established a two-plasmid system to identify promoters recognized by sigma factors and used it to identify promoters recognized by the three SigB homologues, SigF, SigG, and SigH from S. coelicolor A3(2). Here, we used this system to identify 14 promoters recognized by SigB. The promoters were verified in vivo in S. coelicolor A3(2) under osmotic stress conditions in sigB and sigH operon mutants, indicating some cross-recognition of these promoters by these two SigB homologues. This two-plasmid system was used to examine the recognition of all identified SigB-, SigF-, SigG-, and SigH-dependent promoters with all nine SigB homologues. The results confirmed this cross-recognition. Almost all 24 investigated promoters were recognized by two or more SigB homologues and data suggested some distinguishing groups of promoters recognized by these sigma factors. However, analysis of the promoters did not reveal any specific sequence characteristics for these recognition groups. All promoters showed high similarity in the -35 and -10 regions. Immunoblot analysis revealed the presence of SigB under osmotic stress conditions and SigH during morphological differentiation. Together with the phenotypic analysis of sigB and sigH operon mutants in S. coelicolor A3(2), the results suggest a dominant role for SigB in the osmotic stress response and a dual role for SigH in the osmotic stress response and morphological differentiation. These data suggest a complex regulation of the osmotic stress response in relation to morphological differentiation in S. coelicolor A3(2). 相似文献
142.
143.
Die Zulässigkeit genetischer Untersuchungen an Arbeitnehmern wird in Deutschland neu diskutiert, nachdem einer hessischen Lehrerin die Verbeamtung auf Probe zunächst verweigert wurde, weil ihr Vater an der Huntington-Krankheit leidet. Es soll untersucht werden, ob eine gesetzliche Regelung genetischer Untersuchungen in der Arbeitsmedizin wünschenswert ist und welche ethischen Maßstäbe dabei zu berücksichtigen wären. Gendiagnostische Untersuchungsverfahren im engeren Sinn finden noch keine breite Anwendung in der Arbeits- und Betriebsmedizin. Die Nutzung genetischer Informationen gehört aber auch hier zum Standard. Damit sind verschiedene ethische Konflikte verbunden, die insbesondere die Bereiche Autonomie und Diskriminierung betreffen. Gesetzliche Regelungen sollten sich daher nicht an der jeweiligen gendiagnostischen Technologie orientieren, sondern an der prognostisch-prädiktiven Qualität genetischen Wissens. Das Machtungleichgewicht am Arbeitsplatz und die immanenten Interessenkonflikte machen gesetzliche Regelungen erforderlich, die angesichts der zunehmenden Verfügbarkeit prädiktiver medizinischer Informationen Personenrechte schützen und einen fairen Interessenausgleich fördern. 相似文献
144.
A new analytical technique for the determination of oxygen permeability/transmissibility of contact lenses is presented in this paper. The method is based on high performance liquid chromatography (HPLC) with reductive electrochemical detection at -750 mV (vs Ag/AgCl) in combination with a patented sampling chamber that was designed especially for the purpose to determine oxygen at nanomolar levels. Compared to conventional method, the new technique exhibits higher sensitivity, selectivity, and versatility. The method permits the selective determination of oxygen permeability (Dk/L)/transmissibility (Dk) of soft as well as rigid contact lenses with good agreement with the Dk/L (Dk) values reported in the literature. Precision was determined by repeated measurements and yielded relative standard deviations of 3-8% for hydrophile lenses and 5-13% for rigid contact lenses. Because of the extraordinarily high sensitivity of the chromatographic oxygen sensor for the first time, the capability of hydrogel lenses to store oxygen could also be directly monitored. 相似文献
145.
Gierl L Steffen D Ihracky D Schmidt R 《Computer methods and programs in biomedicine》2003,72(2):139-154
In this paper, we discuss the usability of an antibiotics therapy adviser, with a broad, complex spectrum of functions which we have developed within the ICONS project. We present the architecture of the system, case-based reasoning methods used, steps and results of medical evaluations, which are concerning the quality of the recommended therapies, the user friendliness of the system and the interpretation of laboratory results. Furthermore, we discuss problems of transferability of such a system from one site to another as well as problems of local susceptibility patterns and individual dose regimens. 相似文献
146.
147.
Philipp?BraunEmail author Christian?Uhlmann André?Weber Heike?St?rmer Dagmar?Gerthsen Ellen?Ivers-Tiffée 《Journal of Electroceramics》2017,38(2-4):157-167
The transport properties of lithium-ion conducting Li3xLa2/3-xTiO3 are studied for bulk and grain-boundary effects. This paper introduces a procedure for investigating bulk and grain-boundary polarization contributions using electrochemical impedance spectroscopy (EIS) and subsequent analysis via the distribution function of relaxation times (DRT) [1]. The frequency range of impedance spectroscopy is extended up to 120 MHz to resolve all conductivity contributions occurring in a polycrystalline solid electrolyte. Intra grain (bulk) and inter grain (grain boundary) conductivity contributions are separated using (i) a systematic variation of solid electrolyte contacting, (ii) two different solid electrolyte microstructures and activation energies were determined using adequate equivalent circuit models. Finally, these results are supported by SEM analysis, revealing different grain size distributions and different contents of inhomogeneities in Li3xLa2/3-xTiO3 solid electrolytes sintered at 1400°C and at 1450°C. 相似文献
148.
An evaluation of the impact of SG1 disproportionation and the addition of styrene in NMP of methyl methacrylate
下载免费PDF全文
![点击此处可从《American Institute of Chemical Engineers》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Stijn K. Fierens Paul H. M. Van Steenberge Florence Vermeire Marie‐Françoise Reyniers Guy B. Marin Dagmar R. D'hooge 《American Institute of Chemical Engineers》2018,64(7):2545-2559
A kinetic modeling study is presented for batch nitroxide mediated polymerization (NMP) of methyl methacrylate (MMA; nitroxide: N‐tert‐butyl‐N‐[1‐diethylphosphono‐(2,2‐dimethylpropyl)] (SG1)). Arrhenius parameters for SG1 disproportionation (A = 1.4 107 L mol?1 s?1; Ea = 23 kJ mol?1) are reported, based on homopolymerization data accounting for unavoidable temperature variations with increasing time, that is, nonisothermicity. For low targeted chain lengths (TCLs ≤ 300), this nonisothermicity is also relevant for NMP of MMA with a small amount of styrene. Parameter tuning to copolymerization data confirms a penultimate monomer unit effect for activation (sa2 = ka12/ka22=6.7; 363 K; 1: MMA; 2: styrene). To obtain, for a broad TCL range (up to 800), a dispersity well below 1.3 an initial styrene mass fraction of ca. 10% is required. An interpretation of the comonomer incorporation is performed by calculating the fractions of activation‐growth‐deactivation cycles with a given amount of monomer units and the copolymer composition distribution. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2545–2559, 2018 相似文献
149.
Katharina B. Kuentzel Ivan Bradi Alena Akhmetshina Melanie Korbelius Silvia Rainer Dagmar Kolb Martin Gauster Nemanja Vuji Dagmar Kratky 《International journal of molecular sciences》2021,22(19)
Cholesterol and fatty acids are essential lipids that are critical for membrane biosynthesis and fetal organ development. Cholesteryl esters (CE) are degraded by hormone-sensitive lipase (HSL) in the cytosol and by lysosomal acid lipase (LAL) in the lysosome. Impaired LAL or HSL activity causes rare pathologies in humans, with HSL deficiency presenting less severe clinical manifestations. The infantile form of LAL deficiency, a lysosomal lipid storage disorder, leads to premature death. However, the importance of defective lysosomal CE degradation and its consequences during early life are incompletely understood. We therefore investigated how defective CE catabolism affects fetus and infant maturation using Lal and Hsl knockout (-/-) mouse models. This study demonstrates that defective lysosomal but not neutral lipolysis alters placental and fetal cholesterol homeostasis and exhibits an initial disease pathology already in utero as Lal-/- fetuses accumulate hepatic lysosomal lipids. Immediately after birth, LAL deficiency exacerbates with massive hepatic lysosomal lipid accumulation, which continues to worsen into young adulthood. Our data highlight the crucial role of LAL during early development, with the first weeks after birth being critical for aggravating LAL deficiency. 相似文献
150.
Brbel Schulze Dagmar Selke Sabine Kirrbach Rhett Kempe 《Advanced Synthesis \u0026amp; Catalysis》1994,336(2):115-120
Synthesis of New N-Aroylisothiazole-2-imines and N-Aroylaminoisothiazolium Salts by Cyclisation of Thiocyanato-substituted Hydrazones The synthesis of new N-aroylisothiazole-2-imines ( 4g-n ) as well as the corresponding acceptor-substituted 2-amino-isothiazolium salts ( 6f-n ) by cyclocondensation of thiocyanatovinylaldehyde hydrazones ( 3 ) is reported. The structure of these N-imines was proved by spectroscopic methods. The alternative cyclization route to 1,2,3-thiadiazines ( 8 ) is not observed. The hydrazones ( 3a-e ) could not be cyclized to N-imines, only sulfides ( 5a-c ) were obtained. The reaction of 2-thiocyanatomethylen-cycloheptan-2-one ( 9 ) with benzhydrazides gave the same ring closure to the salts ( 10a,b ). The structure of the N-imine 11b has been confirmed unequivocally by X-ray structure analysis. 相似文献