全文获取类型
收费全文 | 5281篇 |
免费 | 108篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 51篇 |
综合类 | 3篇 |
化学工业 | 682篇 |
金属工艺 | 64篇 |
机械仪表 | 65篇 |
建筑科学 | 141篇 |
矿业工程 | 23篇 |
能源动力 | 76篇 |
轻工业 | 255篇 |
水利工程 | 26篇 |
石油天然气 | 14篇 |
无线电 | 339篇 |
一般工业技术 | 599篇 |
冶金工业 | 2582篇 |
原子能技术 | 37篇 |
自动化技术 | 437篇 |
出版年
2022年 | 31篇 |
2021年 | 62篇 |
2020年 | 43篇 |
2019年 | 30篇 |
2018年 | 39篇 |
2017年 | 41篇 |
2016年 | 62篇 |
2015年 | 43篇 |
2014年 | 62篇 |
2013年 | 201篇 |
2012年 | 95篇 |
2011年 | 151篇 |
2010年 | 106篇 |
2009年 | 124篇 |
2008年 | 112篇 |
2007年 | 103篇 |
2006年 | 102篇 |
2005年 | 107篇 |
2004年 | 112篇 |
2003年 | 90篇 |
2002年 | 80篇 |
2001年 | 55篇 |
2000年 | 57篇 |
1999年 | 125篇 |
1998年 | 739篇 |
1997年 | 414篇 |
1996年 | 298篇 |
1995年 | 192篇 |
1994年 | 140篇 |
1993年 | 175篇 |
1992年 | 75篇 |
1991年 | 70篇 |
1990年 | 65篇 |
1989年 | 79篇 |
1988年 | 63篇 |
1987年 | 61篇 |
1986年 | 61篇 |
1985年 | 77篇 |
1984年 | 58篇 |
1983年 | 39篇 |
1982年 | 51篇 |
1981年 | 57篇 |
1980年 | 46篇 |
1979年 | 39篇 |
1978年 | 42篇 |
1977年 | 94篇 |
1976年 | 145篇 |
1975年 | 23篇 |
1974年 | 28篇 |
1973年 | 21篇 |
排序方式: 共有5394条查询结果,搜索用时 46 毫秒
1.
Nitsa Buaron Antonella Mangraviti Francesco Volpin Ann Liu Mariangela Pedone Eric Sankey Dina Aranovich Itay Adar Fausto J. Rodriguez Abraham Nyska Riki Goldbart Tamar Traitel Henry Brem Betty Tyler Joseph Kost 《Advanced functional materials》2021,31(44):2100643
Treating neuroinflammation-related injuries and disorders through manipulation of neuroinflammation functions is being heralded as a new therapeutic strategy. In this study, a novel pectic galactan (PG) polysaccharide based gene therapy approach is developed for targeting reactive gliosis in neuroinflammation. Galectin-3 (Gal-3) is a cell protein with a high affinity to β-galactoside sugars and is highly expressed in reactive gliosis. Since PG carries galactans, it can target reactive gliosis via specific carbohydrate interaction between galactan and Gal-3 on the cell membrane, and therefore can be utilized as a carrier for delivering genes to these cells. The carrier is synthesized by modifying quaternary ammonium groups on the PG. The resulting quaternized PG (QPG) is found to form complexes with plasmid DNA with a mean diameter of 100 nm and have the characteristics required for targeted gene therapy. The complexes efficiently condense large amounts of plasmid per particle and successfully bind to Gal-3. The in vivo study shows that the complexes are biocompatible and safe for administration and can selectively transfect reactive glial cells of an induced cortical lesion. The results confirm that this PG-based delivery system is a promising platform for targeting Gal-3 overexpressing neuroinflammation cells for treating neuroinflammation-related injuries and neurodegenerative diseases. 相似文献
2.
PJ Oefner SP Hunicke-Smith L Chiang F Dietrich J Mulligan RW Davis 《Canadian Metallurgical Quarterly》1996,24(20):3879-3886
Based on a high-performance liquid chromatographic pump, we have built a device that allows recirculation of DNA through a 63-microm orifice with ensuing fractionation to a minimum fragment size of approximately 300 base pairs. Residence time of the DNA fragments in the converging flow created by a sudden contraction was found to be sufficiently long to allow extension of the DNA molecules into a highly extended conformation and, hence, breakage to occur at midpoint. In most instances, 30 passages sufficed to obtain a narrow size distribution, with >90% of the fragments lying within a 2-fold size distribution. The shear rate required to achieve breakage was found to be inversely proportional to the 1.0 power of the molecular weight. Compared with a restriction digest, up to 40% of all fragments could be cloned directly, with only marginal improvements in cloning efficiency having been observed upon prior end repair with Klenow, T4 polymerase or T4 polynucleotide kinase. Sequencing revealed a fairly random distribution of the fragments. 相似文献
3.
4.
F Koumanov C Henry C Ghezzi JP Mathieu C Morin M Vidal J de Leiris M Comet D Fagret 《Canadian Metallurgical Quarterly》1997,24(6):519-525
Two anomeric analogues of glucose labelled with 123 iodine in position 6, proposed as tracers of glucose transport in vivo, have been synthesized: alpha- and beta-methyl-6-deoxy-6-iodo-D-glucopyranoside (alpha MDIG and beta MDIG). The aim of this study was to determine whether these molecules interact with the glucose transporter and whether they could be used as tracers of glucose transport in vivo. The biodistribution of alpha MDIG and beta MDIG was studied in the mouse in vivo. To determine if these two anomers enter the cell via the glucose transporter, their uptake was measured in isolated perfused rat hearts, in human erythrocytes in suspension, and in cardiomyocytes of neonatal rat in culture. Both alpha MDIG and beta MDIG had similar repartitions in the mouse: myocardial uptake averaged 7% of the injected dose/g of organ at 2 min postinjection and alpha MDIG competed with D-glucose to enter the cells. Insulin produced a 123% increase of its uptake in isolated perfused rat hearts and a 100% increase in cardiomyocytes of neonatal rat in culture. alpha MDIG uptake was lowered in the presence of glucose transport inhibitors in each experimental model. An interaction between beta MDIG and glucose transporters was observed only in human erythrocytes in suspension. Only alpha MDIG interacts with the glucose transporter, and thus could be used to estimate glucose transport in vivo. 相似文献
5.
6.
7.
SF Zakharov SH Kwok H Sokoloff HT Chang SP Radko A Chrambach 《Canadian Metallurgical Quarterly》1998,19(10):1625-1630
An automated gel electrophoresis apparatus, recently available commercially, allows one to follow the band during electrophoresis in real time, and lends itself therefore to an evaluation of bandwidth as a function of migration time (the dispersion coefficient), resolution and band shape. These determinations assume the constancy of band area with migration time and at various gel concentrations. The purpose of the present study was to verify these assumptions. Representative proteins and sodium dodecyl sulfate (SDS)-proteins, either natively fluorescent or fluorescein carboxylate labeled, were found to exhibit band areas which approach constancy as a function of migration time in both agarose and polyacrylamide gel electrophoresis, provided that (i) the protein concentration under the band was low enough to obviate self-quenching of fluorescence; (ii) the separation of the protein of interest from contaminants had progressed sufficiently during the time at which band areas were measured; (iii) the baseline under the peak was sufficiently well defined. However, band areas decrease with increasing gel concentration. Protein peaks exhibited leading and trailing tails. The ratio of the combined tail area to total area appeared to be near-constant at varying migration times. However, that ratio increases with increasing gel concentration. The tail area does not appear to be an artifact of fluorometric detection since it is reproduced upon fluorimetric analysis of the protein eluted from gel slices after electrophoresis. However, it may be due to photochemical destruction under the conditions of repetitive fluorometric peak detection. 相似文献
8.
9.
10.
JH Meador-Woodruff KY Little SP Damask A Mansour SJ Watson 《Canadian Metallurgical Quarterly》1993,34(6):348-355
The effects of chronic cocaine exposure on dopamine D1 and D2 receptor gene expression in the human brain were studied in postmortem samples from chronic cocaine abusing and matched control subjects. Using in situ hybridization of receptor autoradiography to examine messenger ribonucleic acid (RNA) and binding sites, respectively, neither D1 nor D2 receptor expression was found to be changed in the nucleus accumbens, caudate, putamen, or substantia nigra of the cocaine-exposed subjects. Although chronic cocaine exposure can produce alterations in dopaminergic neurotransmission, sustained compensatory changes in dopamine receptor expression do not appear to occur in the human. 相似文献