全文获取类型
收费全文 | 316篇 |
免费 | 15篇 |
国内免费 | 1篇 |
专业分类
化学工业 | 180篇 |
金属工艺 | 3篇 |
机械仪表 | 6篇 |
建筑科学 | 4篇 |
矿业工程 | 1篇 |
能源动力 | 8篇 |
轻工业 | 54篇 |
水利工程 | 2篇 |
无线电 | 12篇 |
一般工业技术 | 40篇 |
冶金工业 | 6篇 |
原子能技术 | 2篇 |
自动化技术 | 14篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 38篇 |
2021年 | 55篇 |
2020年 | 14篇 |
2019年 | 12篇 |
2018年 | 9篇 |
2017年 | 5篇 |
2016年 | 16篇 |
2015年 | 13篇 |
2014年 | 18篇 |
2013年 | 18篇 |
2012年 | 22篇 |
2011年 | 19篇 |
2010年 | 18篇 |
2009年 | 22篇 |
2008年 | 14篇 |
2007年 | 5篇 |
2006年 | 8篇 |
2005年 | 5篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 2篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1991年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有332条查询结果,搜索用时 0 毫秒
61.
Ionic liquids as electrolytes 总被引:5,自引:0,他引:5
Salts having a low melting point are liquid at room temperature, or even below, and form a new class of liquids usually called room temperature ionic liquids (RTIL). Information about RTILs can be found in the literature with such key words as: room temperature molten salt, low-temperature molten salt, ambient-temperature molten salt, liquid organic salt or simply ionic liquid. Their physicochemical properties are the same as high temperature ionic liquids, but the practical aspects of their maintenance or handling are different enough to merit a distinction. The class of ionic liquids, based on tetraalkylammonium cation and chloroaluminate anion, has been extensively studied since late 1970s of the XX century, following the works of Osteryoung. Systematic research on the application of chloroaluminate ionic liquids as solvents was performed in 1980s. However, ionic liquids based on aluminium halides are moisture sensitive. During the last decade an increasing number of new ionic liquids have been prepared and used as solvents. The general aim of this paper was to review the physical and chemical properties of RTILs from the point of view of their possible application as electrolytes in electrochemical processes and devices. The following points are discussed: melting and freezing, conductivity, viscosity, temperature dependence of conductivity, transport and transference numbers, electrochemical stability, possible application in aluminium electroplating, lithium batteries and in electrochemical capacitors. 相似文献
62.
Hanna Lewandowska Andrzej Eljaszewicz Izabela Poplawska Marlena Tynecka Alicja Walewska Kamil Grubczak Jordan Holl Hady Razak Hady Slawomir Lech Czaban Joanna Reszec Grayna Przybytniak Wojciech Guszewski Jarosaw Sado Magorzata Dbrowska-Gralak Cezary Kowalewski Piotr Fiedor Tomasz Oldak Artur Kaminski Zbigniew Zimek Marcin Moniuszko 《International journal of molecular sciences》2021,22(16)
Gamma rays and electrons with kinetic energy up to 10 MeV are routinely used to sterilize biomaterials. To date, the effects of irradiation upon human acellular dermal matrices (hADMs) remain to be fully elucidated. The optimal irradiation dosage remains a critical parameter affecting the final product structure and, by extension, its therapeutic potential. ADM slides were prepared by various digestion methods. The influence of various doses of radiation sterilization using a high-energy electron beam on the structure of collagen, the formation of free radicals and immune responses to non-irradiated (native) and irradiated hADM was investigated. The study of the structure changes was carried out using the following methods: immunohistology, immunoblotting, and electron paramagnetic resonance (EPR) spectroscopy. It was shown that radiation sterilization did not change the architecture and three-dimensional structure of hADM; however, it significantly influenced the degradation of collagen fibers and induced the production of free radicals in a dose-dependent manner. More importantly, the observed effects did not disrupt the therapeutic potential of the new transplants. Therefore, radiation sterilization at a dose of 35kGy can ensure high sterility of the dressing while maintaining its therapeutic potential. 相似文献
63.
Izabela Koodziejczyk Andrzej Ka
mierczak Magorzata M. Posmyk 《International journal of molecular sciences》2021,22(16)
The aim of the study was to demonstrate the biostimulating effect of exogenous melatonin (MEL) applied to seeds via hydroconditioning. It was indicated that only well-chosen application technique and MEL dose guarantees success concerning seed germination and young seedlings growth under stress conditions. For maize seed, 50 μM of MEL appeared to be the optimal dose. It improved seed germination and embryonic axes growth especially during chilling stress (5 °C/14 days) and during regeneration after its subsided. Unfortunately, MEL overdosing lowered IAA level in dry seeds and could disrupt the ROS-dependent signal transduction pathways. Very effective antioxidant MEL action was confirmed by low level of protein oxidative damage and smaller quantity of lipid oxidation products in embryonic axes isolated from seeds pre-treated with MEL and then exposed to cold. The stimulatory effects of MEL on antioxidant enzymes: SOD, APX and GSH-PX and on GST-a detoxifying enzyme, was also demonstrated. It was indicated for the first time, that MEL induced defence strategies against stress at the cytological level, as appearing endoreplication in embryonic axes cells even in the seeds germinating under optimal conditions (preventive action), but very intensively in those germinating under chilling stress conditions (intervention action), and after stress removal, to improve regeneration. 相似文献
64.
Woclawek-Potocka I Komiyama J Saulnier-Blache JS Brzezicka E Bah MM Okuda K Skarzynski DJ 《Reproduction (Cambridge, England)》2009,137(1):95-105
Lysophosphatidic acid (LPA) modulates prostaglandin (PG) synthesis via LPA receptor 3 (LPAR3) in the murine endometrium. The lack of functional LPAR3 in mice may lead to embryo mortality. In the present study, we examined the role of LPA in the bovine uterus. We confirmed that LPA is locally produced and released from the bovine endometrium. Moreover, there are enzymes involved in LPA synthesis (phospholipase (PL) D(2) and PLA2G1B) in the bovine endometrium during estrous cycle and early pregnancy. Expression of the receptor for LPA (LPAR1) was positively correlated with the expression of PGE(2) synthase (PGES) and negatively correlated with the expression of PGF(2alpha) synthase (aldose reductase with 20 alpha-hydroxysteroid dehydrogenase activity - PGFS) during early pregnancy. In vivo LPA induced P4 and PGE(2) secretion was inhibited by LPAR1 antagonist (Ki16425). The overall results indicate that LPA is locally produced and released from the bovine endometrium. Moreover, LPAR1 gene expression in the endometrium during the estrous cycle and early pregnancy indicates that LPA may play autocrine and/or paracrine roles in the bovine uterus. LPAR1 gene expression is positively correlated with the expression of the enzyme responsible for luteotropic PGE(2) production (PGES) in endometrium. In cow, LPA stimulates P4 and PGE(2) secretion. Thus, LPA in the bovine reproductive tract may indirectly (via endometrium) or directly support corpus luteum action via the increase of P4 synthesis and the increase of PGE(2)/PGF(2)(alpha) ratio. It suggests that LPA may serve as an important factor in the maintenance of early pregnancy in cow. 相似文献
65.
Slomkowski S Gadzinowski M Sosnowski S Radomska-Galant I Pucci A De Vita C Ciardelli F 《Journal of nanoscience and nanotechnology》2006,6(9-10):3242-3251
Polylactide-b-polyglycidol-b-poly(ethylene oxide) terpolymers and their derivatives with carboxyl and 4-(phenylazo)phenyl labels in polyglycidol blocks were used for formation of nanoparticles. Nanoparticles were produced by self assembly of terpolymer macromolecules in water above the critical aggregation concentration and by dialysis of terpolymer solutions in 1,4-dioxane against water. For terpolymers with 4-(phenylazo)phenyl labels critical aggregation concentrations increased after irradiation with UV light (300 < lambda < 400 nm) inducing conformational change of the label from trans- to cis-conformation. Diameters of nanoparticles obtained by self-assembly of macromolecules ranged from 20 to 44 nm. Dialysis yielded nanoparticles with bimodal diameter distribution. One fraction had diameters below 35 nm and diameters of the second fraction were in a range from 350 to 2300 nm, depending on terpolymer structure. Mixtures of terpolymers with poly(L,L-lactide) and poly(D,D-lactide) blocks yielded nanoparticles with diameters from 350 to 440 nm. Pyrene was incorporated into nanoparticles by partition between solution and nanoparticles or directly during particle formation by dialysis. Monitoring of pyrene release from nanoparticles suggests that a fraction of this compound was entrapped into the polylactide core whereas the remaining one was located in the polyether rich shell. The release from shells is faster for nanoparticles made from copolymers with carboxyl labels in polyglycidol blocks. 相似文献
66.
Kania-Korwel I Garrison AW Avants JK Hornbuckle KC Robertson LW Sulkowski WW Lehmler HJ 《Environmental science & technology》2006,40(12):3704-3710
The enantiomeric enrichment of polychlorinated biphenyl (PCB) atropisomers has been reported in both wildlife and in humans. The biological processes causing this enrichment are only poorly investigated, a fact that limits the use of enantiomeric fractions (EFs) as a tool to study various processes of environmental relevance. To further understand these enantioselective processes, this study investigates the tissue distribution and EFs of some PCB atropisomers after administration of PCB mixtures to immature male Sprague-Dawley rats. The mixtures selected for this study, Aroclor 1254 and an environmental mixture extracted from Chlorofen-contaminated soil, are qualitatively different and are known to induce different groups of hepatic enzymes. Animals were sacrificed 6 days after dosing, PCBs were extracted, and, whenever possible, the EFs of PCBs 84, 91, 95, 149, 174, and 176 were determined by chiral gas chromatography. The EFs of PCB 95 (adipose tissue, liver, and skin) and PCB 149 (adipose tissue, liver, skin, and blood) in tissues from Aroclor 1254-treated animals differed significantly from EFs in the Aroclor standard, while only EFs of PCB 95 (blood) and PCB 174 (adipose tissue) in tissues from soil-extract-treated animals were different from those of the Chlorofen soil extract. PCB 149 in tissues from soil-extract-treated animals underwent no statistically significant enantiomeric enrichment. These differences in the EFs clearly suggest that the enantioselective enrichment of PCB atropisomers may correlate with exposure history, and with the induction of hepatic enzymes, and that EFs may be useful chemical markers of physiologic and biochemical changes following exposure to PCBs. 相似文献
67.
The self-assembled formation of a one-dimensional lanthanum salicylald imine coordination polymer was proved by the X-ray diffraction analysis of new l anthanum(Ⅲ) nitrate complex containing N,N’-bis(salicylidene)-1,5-pentanediami ne ligand(H2L) . It was obtained in situ in a one-step,metal-templated condensa tion of salicylaldehyde with 1,5-pentanediamine(cadaverine,biogenic polyamine) and characterized by microanalysis and spectroscopic(IR,ESI-MS,UV-Vis,and 1 H NMR) data. The [La(NO3) 3(μ-H2L) 2]∞ complex displayed 10-coordinate distorted bicapped dodecahedron geometry with unusual coordination pattern of undeprotonat ed salicylaldimines which acted as μ-bridging ditopic ligands using exclusivel y the oxygens as donor atoms with the nitrogen atoms not being involved in the c oordination environment. 相似文献
68.
Microwave synthesis of large few-layer graphene sheets in aqueous solution of ammonia 总被引:1,自引:0,他引:1
Izabela Janowska Kambiz Chizari Ovidiu Ersen Spyridon Zafeiratos Driss Soubane Victor Da Costa Virginie Speisser Christine Boeglin Matthieu Houllé Dominique Bégin Dominique Plee Marc-Jacques Ledoux Cuong Pham-Huu 《Nano Research》2010,3(2):126-137
Few-layer graphene (FLG) sheets with sizes exceeding several micrometers have been synthesized by exfoliation of expanded graphite in aqueous solution of ammonia under microwave irradiation, with an overall yield approaching 8 wt.%. Transmission electron microscopy (in bright-field and dark-field modes) together with electron diffraction patterns and atomic force microscopy confirmed that this graphene material consisted mostly of mono-, bi- or few-layer graphene (less than ten layers). The high degree of surface reduction was confirmed by X-ray photoelectron and infrared spectroscopies. In addition, the high stability of the FLG in the liquid medium facilitates the deposition of the graphene material onto several substrates via low-cost solution-phase processing techniques, opening the way to subsequent applications of the material. 相似文献
69.
Activated carbon (AC) fiber cloths and hydrophobic microporous polypropylene (PP) membrane, both modified by plasma-induced graft polymerization of acrylic acid (AAc) under UV irradiation, and filled with saturated lithium hydroxide solution were used as electrodes, a separator and electrolyte in electric double layer capacitors (EDLCs). The modification process changed the hydrophobic character of AC and PP materials to hydrophilic, made them wettable and serviceable as components of an electrochemical capacitor. The presence of poly(acrylic acid) on the AC and PP surface was confirmed by SEM and XPS methods. Electrochemical characteristics of EDLCs were investigated by cyclic voltammetry and galvanostatic charge-discharge cycle tests and also by impedance spectroscopy. At the 1000th cycle of potential cycling (1 A g−1) the specific capacitance of 110 F g−1 was obtained with a specific energy of 11 Wh kg−1 at power density of 1 kW kg−1. The above results provide valuable information which may be used when developing novel compositions of EDLCs. 相似文献
70.