全文获取类型
收费全文 | 1543篇 |
免费 | 113篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 20篇 |
化学工业 | 425篇 |
金属工艺 | 51篇 |
机械仪表 | 51篇 |
建筑科学 | 41篇 |
矿业工程 | 2篇 |
能源动力 | 49篇 |
轻工业 | 319篇 |
水利工程 | 19篇 |
石油天然气 | 16篇 |
无线电 | 88篇 |
一般工业技术 | 274篇 |
冶金工业 | 126篇 |
原子能技术 | 11篇 |
自动化技术 | 165篇 |
出版年
2024年 | 4篇 |
2023年 | 16篇 |
2022年 | 41篇 |
2021年 | 89篇 |
2020年 | 46篇 |
2019年 | 64篇 |
2018年 | 69篇 |
2017年 | 82篇 |
2016年 | 67篇 |
2015年 | 41篇 |
2014年 | 66篇 |
2013年 | 120篇 |
2012年 | 101篇 |
2011年 | 124篇 |
2010年 | 81篇 |
2009年 | 90篇 |
2008年 | 89篇 |
2007年 | 61篇 |
2006年 | 46篇 |
2005年 | 34篇 |
2004年 | 35篇 |
2003年 | 27篇 |
2002年 | 19篇 |
2001年 | 15篇 |
2000年 | 11篇 |
1999年 | 15篇 |
1998年 | 39篇 |
1997年 | 27篇 |
1996年 | 24篇 |
1995年 | 18篇 |
1994年 | 21篇 |
1993年 | 11篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 8篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1976年 | 5篇 |
1973年 | 1篇 |
排序方式: 共有1657条查询结果,搜索用时 31 毫秒
141.
Dr. Ricardo Ferraz Prof. João Costa‐Rodrigues Prof. Maria H. Fernandes Dr. Miguel M. Santos Dr. Isabel M. Marrucho Prof. Luís Paulo N. Rebelo Prof. Cristina Prudêncio Prof. João Paulo Noronha Dr. Željko Petrovski Dr. Luís C. Branco 《ChemMedChem》2015,10(9):1480-1483
Significant antiproliferative effects against various tumor cell lines were observed with novel ampicillin salts as ionic liquids. The combination of anionic ampicillin with appropriate ammonium, imidazolium, phosphonium, and pyridinium cations yielded active pharmaceutical ingredient ionic liquids (API‐ILs) that show potent antiproliferative activities against five different human cancer cell lines: T47D (breast), PC3 (prostate), HepG2 (liver), MG63 (osteosarcoma), and RKO (colon). Some API‐ILs showed IC50 values between 5 and 42 nM , activities that stand in dramatic contrast to the negligible cytotoxic activity level shown by the ampicillin sodium salt. Moreover, very low cytotoxicity against two primary cell lines—skin (SF) and gingival fibroblasts (GF)—indicates that the majority of these API‐ILs are nontoxic to normal human cell lines. The most promising combination of antitumor activity and low toxicity toward healthy cells was observed for the 1‐hydroxyethyl‐3‐methylimidazolium–ampicillin pair ([C2OHMIM][Amp]), making this the most suitable lead API‐IL for future studies. 相似文献
142.
Medeiros Sara Fernandes Isabel Fournier Benoit Nunes João Carlos Ramos Violeta 《Bulletin of Engineering Geology and the Environment》2021,80(12):8949-8960
Bulletin of Engineering Geology and the Environment - The alkali-silica reaction (ASR) is a chemical deterioration of concrete that involves reactive forms of silica. Volcanic glass is one of the... 相似文献
143.
Renato Martins da Silva Bárbara Della Noce Camila Fernanda Waltero Evenilton Pessoa Costa Leonardo Araujo de Abreu Naftaly Wang’ombe Githaka Jorge Moraes Helga Fernandes Gomes Satoru Konnai Itabajara da Silva Vaz Jr. Kazuhiko Ohashi Carlos Logullo 《International journal of molecular sciences》2015,16(1):1821-1839
144.
Comparing different methods to fix and to dehydrate cells on alginate hydrogel scaffolds using scanning electron microscopy
下载免费PDF全文
![点击此处可从《Microscopy research and technique》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Camila Perelló Ferrúa Ricardo Marques e Silva Adriana Fernandes da Silva Flávio Fernando Demarco Neftali Lenin Villarreal Carreño 《Microscopy research and technique》2015,78(7):553-561
Scanning electron microscopy (SEM) is commonly used in the analysis of scaffolds morphology, as well as cell attachment, morphology and spreading on to the scaffolds. However, so far a specific methodology to prepare the alginate hydrogel (AH) scaffolds for SEM analysis has not been evaluated. This study compared different methods to fix/dehydrate cells in AH scaffolds for SEM analysis. AH scaffolds were prepared and seeded with NIH/3T3 cell line; fixed with glutaraldehyde, osmium tetroxide, or the freeze drying method and analyzed by SEM. Results demonstrated that the freeze dried method interferes less with cell morphology and density, and preserves the scaffolds structure. The fixation with glutaraldehyde did not affect cells morphology and density; however, the scaffolds morphology was affected in some level. The fixation with osmium tetroxide interfered in the natural structure of cells and scaffold. In conclusion the freeze drying and glutaraldehyde are suitable methods for cell fixation in AH scaffold for SEM, although scaffolds structure seems to be affected by glutaraldehyde. Microsc. Res. Tech. 78:553–561, 2015. © 2015 Wiley Periodicals, Inc. 相似文献
145.
Steroid bioconversion: Towards green processes 总被引:1,自引:0,他引:1
Marco P.C. Marques Filipe Carvalho Carla C.C.R. de Carvalho Joaquim M.S. Cabral Pedro Fernandes 《Food and Bioproducts Processing》2010,88(1):12-20
There is an increasing trend towards reducing the use of organic solvents in industry due to environmental constraints and the adoption of green chemistry guidelines. To overcome the low volumetric productivity of aqueous bioconversion systems involving sparingly water soluble hydrophobic compounds, processes are being developed and designed to incorporate green solvent such as supercritical fluids, ionic liquids and natural oils, and liquid polymers, among others as an alternative to organic solvents. Moreover, processes are developed and redesigned to use/reuse chemicals and reagents derived from waste or renewable feed stocks in order to diminish E-factors.In this work, the use of green solvents as key components in the bioconversion media for a multi-step microbial bioconversion was assessed in a suspended whole cell system, combined with the use of by-products as raw materials, ultimately used as carbon source for cell growth and as sterol substrate for bioconversion. The model system is the selective cleavage of the side-chain of β-sitosterol performed by free resting cells of Mycobacterium sp. NRRL B-3805, a well-established industrial multi-enzymatic process involving the use of nine catabolic enzymes in a 14-step metabolic pathway.Bioconversion yields in silicone media were higher than the ones obtained in polyethylene glycol (PEG), polypropylene glycol (PPG) and ionic liquids, as well as in dioctyl phthalate (DOP), an organic solvent that has previously been shown to allow high conversion yields. Total conversion of 12 mM substrate in silicone media was consistently obtained at the end of 120-h bioconversion runs. Similar bioconversion profiles were attained during a 50-fold scale-up, maintaining constant the power consumption per unit of volume. 相似文献
146.
Suellen Cadorin Fernandes Iolanda Cruz Vieira Ademir Neves 《Electrochimica acta》2010,55(23):7152-7157
A gold electrode surface was modified using a dinuclear copper complex [CuII2 (Ldtb)(μ-OCH3)](BPh4) and then coated with a chitosan film. This biomimetic polymer film-coated electrode was employed to eliminate the interference from ascorbic acid and uric acid in the sensitive and selective determination of dopamine. The optimized conditions obtained for the biomimetic electrode were 0.1 M phosphate buffer solution (pH 8.0), complex concentration of 2.0 × 10−4 M, 0.1% of chitosan and 0.25% of glyoxal. Under the optimum conditions, the calibration curve was linear in the concentration range of 4.99 × 10−7 to 1.92 × 10−5 M, and detection and quantification limits were 3.57 × 10−7 M and 1.07 × 10−6 M, respectively. The recovery study gave values of 95.2-102.6%. The lifetime of this biomimetic sensor showed apparent loss of activity after 70 determinations. The results obtained with the modified electrode for dopamine quantification in the injection solution matrix were in good agreement with those of the pharmacopoeia method. 相似文献
147.
Tatiana A. Kolesnikova Dmitry A. Gorin Paulo Fernandes Stefanie Kessel Gennady B. Khomutov Andreas Fery Dmitry G. Shchukin Helmuth Möhwald 《Advanced functional materials》2010,20(7):1189-1195
A water suspension of nanocomposite microcapsules with embedded ZnO nanoparticles in the capsule shell is reported. The microcapsule morphology is characterized by confocal microscopy, TEM, SEM, and AFM before and after ultrasound treatment. A remarkably high capsule sensitivity to ultrasound is evidenced, and it is observed to grow with increasing number of ZnO nanoparticle layers in the nanocomposite shell. This effect is correlated with the mechanical properties of microcapsules measured with AFM. 相似文献
148.
Groundwater Assessment at Santiago Island (Cabo Verde): A Multidisciplinary Approach to a Recurring Source of Water Supply 总被引:1,自引:0,他引:1
Paula Maria Carreira José M. Marques António Pina António Mota Gomes Paula A. Galego Fernandes Fernando Monteiro Santos 《Water Resources Management》2010,24(6):1139-1159
Groundwater resources are in many parts of the world the only source for private domestic, agricultural and public water supply.
Subsurface has also become major recipient of wastewater and solid waters especially in the developing countries. Overexploitation
of coastal aquifers and pollution are among the main problems related to groundwater resources assessment and management in
Santiago Island (Cabo Verde). Brackish groundwater is the only available water type in the region that is being provided to
numerous parts of the Island such as Praia Baixo, Montenegro, and Charco for agriculture and human supply. Solute and isotope
data obtained in different groundwater systems were used in the identification of groundwater resources degradation. In order
to understand the influence of the anthropogenic activities on the water quality and the main origin of the salts in groundwater,
a statistical approach (Principal Components Analyses—PCA) was performed on the physico-chemical data. The results obtained
indicate water–rock interaction mechanisms as the major process responsible for the groundwater quality (mainly calcium-bicarbonate
type), reflecting the lithological composition of the subsurface soil. Also, anthropogenic contamination was identified, in
several points of the island. Isotopic techniques (δ2H, δ18O and 3H content) combined with geochemistry provided comprehensive information on groundwater recharge, as well as on the identification
of salinization mechanisms (e.g. seawater intrusion, salt dissolution, and marine aerosols) of the groundwater systems, at
Santiago Island. 相似文献
149.
150.
For the adaptation of cells of Saccharomyces cerevisiae, a period of latency is necessary before exponential growth is resumed in a medium supplemented with a highly inhibitory concentration of copper. In this work, we have examined some physiological responses occurring during this period of adaptation. The results revealed that plasma membrane H(+)-ATPase (PM-ATPase) activity is strongly stimulated (up to 24-fold) during copper-induced latency in growth medium with glucose, reaching maximal levels when the cells were about to start inhibited exponential growth. This in vivo activation of the ATPase activity by copper was accompanied by the stimulation of the H(+)-pumping activity of the enzyme in vivo and was essentially due to the increase of the apparent V(max) for MgATP. Although the exact molecular basis of the reported plasma membrane ATPase activation was not clarified, no increase in the mRNA levels from the encoding genes PMA1 and PMA2 was apparently detected during copper-induced latency. The physiological response reported here may allow the cells to cope with copper-induced lipid peroxidation and consequent decrease in plasma membrane lipid ordering and increase in the non-specific permeability to protons. The consequences of these copper deleterious effects were revealed by the decrease of the intracellular pH (pH(i)) of the yeast population, from approximately pH(i) 6 to pH(i) 5, during copper-induced latency in growth medium at pH 4.3. The time-dependent patterns of plasma membrane ATPase activation and of the decrease of pH(i) during the period of adaptation to growth with copper correlate, suggesting that the regulation of this membrane enzyme activity may be triggered by intracellular acidification. Consistent with this idea, when exponential growth under copper stress was resumed and the pH(i) of the yeast population recovered up to physiological values, plasma membrane ATPase activity simultaneously decreased from the highly stimulated level attained during the adaptation period of latency. 相似文献