全文获取类型
收费全文 | 2408篇 |
免费 | 175篇 |
专业分类
电工技术 | 22篇 |
综合类 | 29篇 |
化学工业 | 974篇 |
金属工艺 | 25篇 |
机械仪表 | 42篇 |
建筑科学 | 104篇 |
矿业工程 | 6篇 |
能源动力 | 55篇 |
轻工业 | 387篇 |
水利工程 | 44篇 |
石油天然气 | 4篇 |
无线电 | 84篇 |
一般工业技术 | 377篇 |
冶金工业 | 124篇 |
原子能技术 | 7篇 |
自动化技术 | 299篇 |
出版年
2024年 | 16篇 |
2023年 | 29篇 |
2022年 | 180篇 |
2021年 | 179篇 |
2020年 | 99篇 |
2019年 | 87篇 |
2018年 | 91篇 |
2017年 | 97篇 |
2016年 | 114篇 |
2015年 | 95篇 |
2014年 | 125篇 |
2013年 | 172篇 |
2012年 | 142篇 |
2011年 | 204篇 |
2010年 | 119篇 |
2009年 | 117篇 |
2008年 | 126篇 |
2007年 | 97篇 |
2006年 | 70篇 |
2005年 | 49篇 |
2004年 | 46篇 |
2003年 | 49篇 |
2002年 | 41篇 |
2001年 | 27篇 |
2000年 | 28篇 |
1999年 | 28篇 |
1998年 | 28篇 |
1997年 | 14篇 |
1996年 | 10篇 |
1995年 | 16篇 |
1994年 | 16篇 |
1993年 | 13篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有2583条查询结果,搜索用时 15 毫秒
141.
Sebastian Granitzer Raimund Widhalm Martin Forsthuber Isabella Ellinger Gernot Desoye Markus Hengstschlger Harald Zeisler Hans Salzer Claudia Gundacker 《International journal of molecular sciences》2021,22(4)
The placental barrier can protect the fetus from contact with harmful substances. The potent neurotoxin methylmercury (MeHg), however, is very efficiently transported across the placenta. Our previous data suggested that L-type amino acid transporter (LAT)1 is involved in placental MeHg uptake, accepting MeHg-L-cysteine conjugates as substrate due to structural similarity to methionine. The aim of the present study was to investigate the antioxidant defense of placental cells to MeHg exposure and the role of LAT1 in this response. When trophoblast-derived HTR-8/SVneo cells were LAT1 depleted by siRNA-mediated knockdown, they accumulated less MeHg. However, they were more susceptible to MeHg-induced toxicity. This was evidenced in decreased cell viability at a usually noncytotoxic concentration of 0.03 µM MeHg (~6 µg/L). Treatment with ≥0.3 µM MeHg increased cytotoxicity, apoptosis rate, and oxidative stress of HTR-8/SVneo cells. These effects were enhanced under LAT1 knockdown. Reduced cell number was seen when MeHg-exposed cells were cultured in medium low in cysteine, a constituent of the tripeptide glutathione (GSH). Because LAT1-deficient HTR-8/SVneo cells have lower GSH levels than control cells (independent of MeHg treatment), we conclude that LAT1 is essential for de novo synthesis of GSH, required to counteract oxidative stress. Genetic predisposition to decreased LAT1 function combined with MeHg exposure could increase the risk of placental damage. 相似文献
142.
Günther Huber Otto Machhammer Maren Lepple Claudia Weidlich Cord-Henrich Dustmann Akane Hartenbach 《化学,工程师,技术》2021,93(4):664-672
A photovoltaic system could supply a single-family house with electrical power, warm water, and room heat if the energy would be distributed over the year to suit the load profile. However, storage systems for this are not state of the art yet. A concrete example is used to estimate which parameters such a power storage system should have. A suitable electrochemical reaction system based on inorganic salt mixtures is proposed. The German Federal Ministry of Education and Research is currently funding the development of a world storage facility based on the same reaction system. 相似文献
143.
144.
Hélida V. P. Vieira Priscila F. Oliveira Josane A. Costa Leonardo A. de Oliveira Letícia S. Mota Claudia R. E. Mansur 《应用聚合物科学杂志》2021,138(44):51301
Partially hydrolyzed polyacrylamide (PHPA) is the most widely used polymer in enhanced oil recovery (EOR) applications. However, under conditions of high temperature and salinity, the PHPA molecules become hydrolyzed, causing a drastic reduction of the viscosity of the polymer solution due to the presence of negative charges, making the molecules more susceptible to interactions with cations. In this sense, in order to increase the stability of these polymers, an anionic monomer more resistant to cations such as 2-acrylamido-2-methylpropane sulfonic acid (AMPS) has been incorporated into the HPAM molecules. This work evaluated the thermal stability of a copolymer (acrylamide and AMPS - AN125) and a terpolymer (acrylamide, acrylate, and AMPS-FP5115) in the time course of 360 days. The tests were carried out in typical conditions of Brazilian offshore reservoirs, such as absence of oxygen, high temperature, and high salt concentration. The test method involved measurements of intrinsic viscosity in function of time and determination of the hydrolysis degree of the polymers by elemental analysis. The copolymer AN125 was more stable under the test conditions than the terpolymer FP 5115 due to the presence of a higher concentration of AMPS in the copolymer. The AMPS group was hydrolyzed to AA at a temperature of 100 °C, however, the increase in salt concentration delayed the onset of this degradation. The tests indicated that the presence of a higher AMPS content in the copolymer does not prevent the polymer from undergoing hydrolysis, but delays the polymer precipitation step in the solution. 相似文献
145.
Claudia Li Jian Song Shude Zhang Xiaoyao Tan Xiuxia Meng Jaka Sunarso Shaomin Liu 《Journal of the American Ceramic Society》2021,104(5):2268-2284
New CO2-resistant dual-phase Sm0.2Ce0.8O1.925–SrCo0.4Fe0.55Zr0.05O3-δ (SDC-SCFZ) ceramics present a promising outlook for potential future applications in membrane reactors and solid oxide fuel cells. Their high oxygen permeation flux and stability in CO2 sweep gas also allow their integration in oxyfuel combustion. Here the structural characteristics, electrical conductivities, thermal expansion behaviors, and oxygen permeabilities of four different SDC-SCFZ membranes with weight ratios of 10:90, 25:75, 50:50, and 75:25 (SDC:SCFZ) are systematically studied. Among these four SDC-SCFZ compositions, 0.6 mm-thick 25 wt% SDC-75 wt% SCFZ displayed the highest oxygen permeation fluxes that reach 1.26 mL min−1 cm−2 at 950°C and retained its phase integrity under alternating He and CO2 sweep gas over 72 hours of operation. This composite also showed a moderate thermal expansion coefficient of 1.90 × 10−5 K−1 between 30°C and 1000°C and an electrical conductivity of at least 16 S cm−1 at 550°C and above. Modeling studies revealed that the oxygen permeation fluxes through 25SDC-75SCFZ are limited by surface exchange reactions from 700°C to 800°C and mixed bulk diffusion and surface exchange reactions above 800°C. 相似文献
146.
Brianna L. Musicó Quinton Wright Cordell Delzer T. Zac Ward Claudia J. Rawn David G. Mandrus Veerle Keppens 《Journal of the American Ceramic Society》2021,104(7):3750-3759
The multicomponent approach has been successfully expanded to the Ruddlesden–Popper structure with the synthesis of two different high-entropy cuprate compositions: (La0.2Nd0.2Gd0.2Tb0.2Dy0.2)2CuO4 and (La0.2Pr0.2Nd0.2Sm0.2Eu0.2)2CuO4. The effect of synthesis method is explored using both solid-state reaction and polymeric steric entrapment (PSE) methods. It is found that PSE leads to more randomly distributed cation species, providing an advantageous method of synthesis for the growing field of high entropy oxides. In situ high-temperature x-ray diffraction tracks the amorphous to crystalline phase transformation in (La0.2Nd0.2Gd0.2Tb0.2Dy0.2)2CuO4 powder, synthesized using the PSE method. Using the High-Temperature XRD data, a method for gaining information on the kinetic behavior is also applied. Magnetometry of both compositions indicates ferrimagnetic behavior at low temperatures. 相似文献
147.
L. Viridiana Soto-Robles María Fernanda Lpez Vernica Torres-Banda Claudia Cano-Ramírez Gabriel Obregn-Molina Gerardo Zúiga 《International journal of molecular sciences》2021,22(1)
Dendroctonus-bark beetles are natural agents contributing to vital processes in coniferous forests, such as regeneration, succession, and material recycling, as they colonize and kill damaged, stressed, or old pine trees. These beetles spend most of their life cycle under stem and roots bark where they breed, develop, and feed on phloem. This tissue is rich in essential nutrients and complex molecules such as starch, cellulose, hemicellulose, and lignin, which apparently are not available for these beetles. We evaluated the digestive capacity of Dendroctonus rhizophagus to hydrolyze starch. Our aim was to identify α-amylases and characterize them both molecularly and biochemically. The findings showed that D. rhizophagus has an α-amylase gene (AmyDr) with a single isoform, and ORF of 1452 bp encoding a 483-amino acid protein (53.15 kDa) with a predicted signal peptide of 16 amino acids. AmyDr has a mutation in the chlorine-binding site, present in other phytophagous insects and in a marine bacterium. Docking analysis showed that AmyDr presents a higher binding affinity to amylopectin compared to amylose, and an affinity binding equally stable to calcium, chlorine, and nitrate ions. AmyDr native protein showed amylolytic activity in the head-pronotum and gut, and its recombinant protein, a polypeptide of ~53 kDa, showed conformational stability, and its activity is maintained both in the presence and absence of chlorine and nitrate ions. The AmyDr gene showed a differential expression significantly higher in the gut than the head-pronotum, indicating that starch hydrolysis occurs mainly in the midgut. An overview of the AmyDr gene expression suggests that the amylolytic activity is regulated through the developmental stages of this bark beetle and associated with starch availability in the host tree. 相似文献
148.
149.
150.
Claudia Penna Saveria Femmin Fabrizio Caldera Alberto Rubin Pedrazzo Claudio Cecone Edoardo Alfì Stefano Comit Takanobu Higashiyama Francesco Trotta Pasquale Pagliaro Roberta Cavalli 《International journal of molecular sciences》2021,22(8)
Heart failure (HF) prevalence is increasing among the aging population, and the mortality rate remains unacceptably high despite improvements in therapy. Myocardial ischemia (MI) and, consequently, ischemia/reperfusion injury (IRI), are frequently the basis of HF development. Therefore, cardioprotective strategies to limit IRI are mandatory. Nanocarriers have been proposed as alternative therapy for cardiovascular disease. Controlled reoxygenation may be a promising strategy. Novel nanocarriers, such as cyclic nigerosyl-nigerose (CNN), can be innovative tools for oxygen delivery in a controlled manner. In this study we analyzed new CNN-based formulations as oxygen nanocarriers (O2-CNN), and compared them with nitrogen CNN (N2-CNN). These different CNN-based formulations were tested using two cellular models, namely, cardiomyoblasts (H9c2), and endothelial (HMEC) cell lines, at different concentrations. The effects on the growth curve during normoxia (21% O2, 5% CO2 and 74% N2) and their protective effects during hypoxia (1% O2, 5% CO2 and 94% N2) and reoxygenation (21% O2, 5% CO2 and 74% N2) were studied. Neither O2-CNN nor N2-CNN has any effect on the growth curve during normoxia. However, O2-CNN applied before hypoxia induces a 15–30% reduction in cell mortality after hypoxia/re-oxygenation when compared to N2-CNN. O2-CNN showed a marked efficacy in controlled oxygenation, which suggests an interesting potential for the future medical application of soluble nanocarrier systems for MI treatment. 相似文献