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   283篇
  免费   17篇
电工技术   1篇
化学工业   180篇
金属工艺   4篇
机械仪表   4篇
建筑科学   6篇
能源动力   13篇
轻工业   24篇
水利工程   3篇
无线电   8篇
一般工业技术   30篇
冶金工业   2篇
自动化技术   25篇
  2024年   2篇
  2023年   5篇
  2022年   63篇
  2021年   63篇
  2020年   15篇
  2019年   8篇
  2018年   12篇
  2017年   9篇
  2016年   16篇
  2015年   6篇
  2014年   5篇
  2013年   15篇
  2012年   17篇
  2011年   18篇
  2010年   13篇
  2009年   11篇
  2008年   6篇
  2007年   7篇
  2006年   6篇
  2005年   2篇
  2004年   1篇
排序方式: 共有300条查询结果,搜索用时 15 毫秒
41.
The use of assisted reproductive technologies (ART) still requires strategies through which to maximize individual fertility chances. In vitro folliculogenesis (ivF) may represent a valid option to convey the large source of immature oocytes in ART. Several efforts have been made to set up ivF cultural protocols in medium-sized mammals, starting with the identification of the most suitable gonadotropic stimulus. In this study, Equine Chorionic Gonadotropin (eCG) is proposed as an alternative to Follicle Stimulating Hormone (FSH) based on its long superovulation use, trans-species validation, long half-life, and low costs. The use of 3D ivF on single-ovine preantral (PA) follicles allowed us to compare the hormonal effects and to validate their influence under two different cultural conditions. The use of eCG helped to stimulate the in vitro growth of ovine PA follicles by maximizing its influence under FBS-free medium. Higher performance of follicular growth, antrum formation, steroidogenic activity and gap junction marker expression were recorded. In addition, eCG, promoted a positive effect on the germinal compartment, leading to a higher incidence of meiotic competent oocytes. These findings should help to widen the use of eCG to ivF as a valid and largely available hormonal support enabling a synchronized in vitro follicle and oocyte development.  相似文献   
42.
Cytotoxic necrotizing factor 1 (CNF1) is a bacterial virulence factor, the target of which is represented by Rho GTPases, small proteins involved in a huge number of crucial cellular processes. CNF1, due to its ability to modulate the activity of Rho GTPases, represents a widely used tool to unravel the role played by these regulatory proteins in different biological processes. In this review, we summarized the data available in the scientific literature concerning the observed in vitro effects induced by CNF1. An article search was performed on electronic bibliographic resources. Screenings were performed of titles, abstracts, and full-texts according to PRISMA guidelines, whereas eligibility criteria were defined for in vitro studies. We identified a total of 299 records by electronic article search and included 76 original peer-reviewed scientific articles reporting morphological or biochemical modifications induced in vitro by soluble CNF1, either recombinant or from pathogenic Escherichia coli extracts highly purified with chromatographic methods. Most of the described CNF1-induced effects on cultured cells are ascribable to the modulating activity of the toxin on Rho GTPases and the consequent effects on actin cytoskeleton organization. All in all, the present review could be a prospectus about the CNF1-induced effects on cultured cells reported so far.  相似文献   
43.
Taxane efficacy in triple negative breast cancer(TNBC)is limited by insufficient tumor accumulation and severe off-target effects.Nanomedicines offer a unique opportunity to enhance the anti-cancer potency of this drug.Here,1,000 nm×400 nm discoidal polymeric nanoconstructs(DPN)encapsulating docetaxel(DTXL)and the near infrared compound Iipid-Cy5 were engineered.DPN were obtained by filling multiple times cylindrical wells in a poly(vinyl alcohol)template with a polymer mixture comprising poly(lactic-co-glycolic acid)(PLGA)and poly(ethylene glycol)diacrylate(PEG-DA)chains together with therapeutic and imaging agents.The resulting“multi-passage”DPN exhibited higher DTXL loading,Iipid-Cy5 stability,and stiffness as compared to the conventional"single-passage"approach.Confocal microscopy confirmed that DTXL-DPN were not taken up by MDA-MB-231 cells but would rather sit next to the cell membrane and slowly release DTXL thereof.Empty DPN had no toxicity on TNBC cells,whereas DTXL-DPN presented a cytotoxic potential comparable to free DTXL(IC50=2.6 nM±1.0 nM vs.7.0 nM±1.09 nM at 72 h).In orthotopic murine models,DPN accumulated in TNBC more efficiently than free-DTXL.With only 2 mg/kg DTXL,intravenously administered every 2 days for a total of 13 treatments,DTXL-DPN induced tumor regression and were associated to an overall 80%survival rate as opposed to a 30%survival rate for free-DTXL,at 120 days.All untreated mice succumbed before 90 days.Collectively,this data demonstrates that vascular confined multi-passage DPN,biomimicking the behavior of circulating platelets,can efficiently deliver chemotherapeutic molecules to malignant tissues and effectively treat orthotopic TNBC at minimal taxane doses.  相似文献   
44.
The angiogenin protein (ANG) is one of the most potent endogenous angiogenic factors. In this work we characterized by means of potentiometric, spectroscopic and voltammetric techniques, the copper complex species formed with peptide fragments derived from the N-terminal domain of the protein, encompassing the sequence 1-17 and having free amino, Ang1-17, or acetylated N-terminus group, AcAng1-17, so to explore the role of amino group in metal binding and cellular copper uptake. The obtained data show that amino group is the main copper anchoring site for Ang1-17. The affinity constant values, metal coordination geometry and complexes redox-potentials strongly depend, for both peptides, on the number of copper equivalents added. Confocal laser scanning microscope analysis on neuroblastoma cells showed that in the presence of one equivalent of copper ion, the free amino Ang1-17 increases cellular copper uptake while the acetylated AcAng1-17 strongly decreases the intracellular metal level. The activity of peptides was also compared to that of the protein normally present in the plasma (wtANG) as well as to the recombinant form (rANG) most commonly used in literature experiments. The two protein isoforms bind copper ions but with a different coordination environment. Confocal laser scanning microscope data showed that the wtANG induces a strong increase in intracellular copper compared to control while the rANG decreases the copper signal inside cells. These data demonstrate the relevance of copper complexes’ geometry to modulate peptides’ activity and show that wtANG, normally present in the plasma, can affect cellular copper uptake.  相似文献   
45.
A novel GC/MS analytical procedure for the identification of lipids, waxes, proteins, and resinous materials in the same microsample from painted works of art has been optimized. It is based on a sample multistep chemical pretreatment (solvent extractions and microwave-assisted chemolysis) that is able to separate the various organic components into different fractions, which are suitably treated and derivatized before analysis. In particular, the procedure allows the complete saponification of wax esters and the completeness of the Cannizzaro type reaction of shellac acids in conditions that are suitable also for glycerides saponification. The method was tested on reference materials for the identification of proteinaceous binders (egg, collagen, casein) on the basis of the quantitative determination of the amino acid profile and the identification of glycerolipids (linseed oil, poppy seed oil, walnut oil, and egg), plant resins (Pinaceae resins, sandarac, mastic, and dammar), animal resins (shellac), tars or pitches, and natural waxes (beeswax, carnauba wax) on the basis of the determination of fatty acid, alcohol, and hydrocarbon profiles and of significant terpenic molecular markers. The procedure was applied to the characterization of three old paint microsamples. Animal glue, egg, linseed oil, beeswax, Pinaceae resin, dammar, and shellac were the identified materials found in mixtures and recognized as original and/or restoration substances.  相似文献   
46.
47.
48.
49.
An experimental test campaign has been carried out in order to investigate the performances in terms of pure hydrogen production of a multi-membrane module coupled with a methane reforming fixed bed reactor. The effect of operating parameters such as the temperature, the pressure, the water/methane feed flow rates and the feed molar ratio has been studied. The hydrogen produced into the traditional reformer has been recovered in the shell side of the membrane module by vacuum pumping. The membrane module consists of 19 Pd/Ag permeator tubes of wall thickness 150 μm, diameter 10 mm and length 250 mm: these dense permeators permitted to separate ultra-pure hydrogen.The experiments have been carried out with the reaction pressure of 100-490 kPa, the temperature of the reformer of 570-720 °C and the temperature of the Pd/Ag membranes module of 300-400 °C. A water/methane stream of molar ratio of 4/1 and 5/1 has been fed into the methane reformer at GSHV of 1547.6 and 1796.1 L(STP) kg−1 h−1. Hydrogen yield value of about 3 has been measured at reaction pressure of 350 kPa, temperature reformer of 720 °C and methane feed flow rate of 6.445 × 10−4 mol s−1.  相似文献   
50.
The polycrystalline silicon material grown by the edge-defined film-fed growth technique, and often used in solar cell production, is known to be carbon and dislocation rich. Aim of this work was to explore the effect of low-temperature annealing in vacuum on properties of these structural defects, often present in different solar-grade materials. Electrical measurements by deep level transient spectroscopy revealed the presence of the defects typically found in dislocated silicon. Detailed analysis further suggested that they are also carbon related, exhibiting quite unexpected behavior at such low-temperature annealing. Moreover, photoluminescence results showed electron-hole droplet condensation at dislocations after such low-temperature annealing. This further supports the hypothesis that point defects are incorporated at dislocation cores rather than in a cloud at its proximity.  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