全文获取类型
收费全文 | 681篇 |
免费 | 24篇 |
专业分类
电工技术 | 1篇 |
综合类 | 1篇 |
化学工业 | 323篇 |
金属工艺 | 17篇 |
机械仪表 | 14篇 |
建筑科学 | 16篇 |
矿业工程 | 1篇 |
能源动力 | 18篇 |
轻工业 | 16篇 |
水利工程 | 9篇 |
石油天然气 | 38篇 |
无线电 | 48篇 |
一般工业技术 | 144篇 |
冶金工业 | 14篇 |
原子能技术 | 1篇 |
自动化技术 | 44篇 |
出版年
2023年 | 9篇 |
2022年 | 58篇 |
2021年 | 83篇 |
2020年 | 21篇 |
2019年 | 19篇 |
2018年 | 22篇 |
2017年 | 23篇 |
2016年 | 35篇 |
2015年 | 9篇 |
2014年 | 27篇 |
2013年 | 39篇 |
2012年 | 33篇 |
2011年 | 34篇 |
2010年 | 23篇 |
2009年 | 18篇 |
2008年 | 23篇 |
2007年 | 16篇 |
2006年 | 12篇 |
2005年 | 8篇 |
2004年 | 11篇 |
2003年 | 12篇 |
2002年 | 9篇 |
2001年 | 7篇 |
2000年 | 11篇 |
1999年 | 4篇 |
1998年 | 10篇 |
1997年 | 7篇 |
1996年 | 3篇 |
1993年 | 3篇 |
1992年 | 6篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 15篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1970年 | 3篇 |
1969年 | 5篇 |
1968年 | 2篇 |
排序方式: 共有705条查询结果,搜索用时 15 毫秒
1.
Liangtao Yang Liang-Yin Kuo Juan Miguel López del Amo Prasant Kumar Nayak Katherine A. Mazzio Sebastian Maletti Daria Mikhailova Lars Giebeler Payam Kaghazchi Teófilo Rojo Philipp Adelhelm 《Advanced functional materials》2021,31(38):2102939
A known strategy for improving the properties of layered oxide electrodes in sodium-ion batteries is the partial substitution of transition metals by Li. Herein, the role of Li as a defect and its impact on sodium storage in P2-Na0.67Mn0.6Ni0.2Li0.2O2 is discussed. In tandem with electrochemical studies, the electronic and atomic structure are studied using solid-state NMR, operando XRD, and density functional theory (DFT). For the as-synthesized material, Li is located in comparable amounts within the sodium and the transition metal oxide (TMO) layers. Desodiation leads to a redistribution of Li ions within the crystal lattice. During charging, Li ions from the Na layer first migrate to the TMO layer before reversing their course at low Na contents. There is little change in the lattice parameters during charging/discharging, indicating stabilization of the P2 structure. This leads to a solid-solution type storage mechanism (sloping voltage profile) and hence excellent cycle life with a capacity of 110 mAh g-1 after 100 cycles. In contrast, the Li-free compositions Na0.67Mn0.6Ni0.4O2 and Na0.67Mn0.8Ni0.2O2 show phase transitions and a stair-case voltage profile. The capacity is found to originate from mainly Ni3+/Ni4+ and O2-/O2-δ redox processes by DFT, although a small contribution from Mn4+/Mn5+ to the capacity cannot be excluded. 相似文献
2.
Konstantin V. Dergilev Evgeny K. Shevchenko Zoya I. Tsokolaeva Irina B. Beloglazova Ekaterina S. Zubkova Maria A. Boldyreva Mikhail Yu. Menshikov Elizaveta I. Ratner Dmitry Penkov Yelena V. Parfyonova 《International journal of molecular sciences》2020,21(24)
Cell therapy of the post-infarcted myocardium is still far from clinical use. Poor survival of transplanted cells, insufficient regeneration, and replacement of the damaged tissue limit the potential of currently available cell-based techniques. In this study, we generated a multilayered construct from adipose-derived mesenchymal stromal cells (MSCs) modified to secrete stem cell factor, SCF. In a rat model of myocardium infarction, we show that transplantation of SCF producing cell sheet induced activation of the epicardium and promoted the accumulation of c-kit positive cells in ischemic muscle. Morphometry showed the reduction of infarct size (16%) and a left ventricle expansion index (0.12) in the treatment group compared to controls (24–28%; 0.17–0.32). The ratio of viable myocardium was more than 1.5-fold higher, reaching 49% compared to the control (28%) or unmodified cell sheet group (30%). Finally, by day 30 after myocardium infarction, SCF-producing cell sheet transplantation increased left ventricle ejection fraction from 37% in the control sham-operated group to 53%. Our results suggest that, combining the genetic modification of MSCs and their assembly into a multilayered construct, we can provide prolonged pleiotropic effects to the damaged heart, induce endogenous regenerative processes, and improve cardiac function. 相似文献
3.
T. I. Voronina T. S. Lagunova M. P. Mikhailova K. D. Moiseev M. A. Sipovskaya Yu. P. Yakovlev 《Semiconductors》1997,31(8):763-767
Galvanomagnetic phenomena and photoconductivity in broken-gap type-II GaInAsSb/p-InAs heterojunctions with different levels of doping of the solid solution with donor (Te) or acceptor (Zn) impurities have
been investigated. It has been determined that in such structures an electronic channel, which determines the galvanomagnetic
effects in a wide range of doping levels, is present at the heterojunction. A sharp decrease of the Hall mobility was observed
in the experimental heterostructures with a high level of doping of the epitaxial layer with an acceptor impurity. The observed
effect is due to exhaustion of the electronic channel as a result of carrier localization in potential wells at the heterojunction.
Fiz. Tekh. Poluprovodn. 31, 897–901 (August 1997) 相似文献
4.
Nemenchinskaya Ekaterina O. Kondratenko Yuri V. Sadovsky Michael G. 《Open Systems & Information Dynamics》2004,11(2):161-175
The new method of a gap recovery in symbol sequences is presented. A covering is combined from the suitable reasonably short strings of the parts of a sequence available for observation. Two criteria are introduced to choose the best covering. It must yield the maximum of entropy of a frequency dictionary developed over the sequence obtained due to the recovery, if an overlapping combined from the copies of strings from the available parts of the sequence exists. The second criterion identifies the best covering in case when one has to use any string to cover the gap; here the best covering must yield the minimum of specific entropy of the frequency dictionary developed over the available parts of the sequence against the one developed over the entire sequence obtained due to the recovery. Kirdin kinetic machine which is the ideal fine-grained structureless computer has been used to resolve the problem of the reconstruction of a gap in symbol sequence. 相似文献
5.
Conclusions -- A gas-phase method of depositing one- or multiple-component carbide coatings on CFM of various textile structures has been developed. With preservation of the strength and elastic characteristics of the CFM, the thermo-oxidative resistance of the material is increased, plus the temperature range for the decomposition is shifted into the higher temperature region — by 150–250°C as compared with the starting material.-- CFM with protective coatings are finding ever greater use in making filters for cleaning up high-temperature gas-air mixtures.VNIIPV. Translated from Khimicheskie Volokna, No. 3, pp. 47–48, May–June, 1991. 相似文献
6.
7.
We have theoretically and experimentally studied the possibility of using nonlinear recording of holographic mirrors for creating
a spectrum divider capable of spatially separating wavelengths in the spectral region of 290–330 nm. 相似文献
8.
Conclusions -- The possibility of using dispersions of technical carbon in a medium of ethylene glycol, an aqueous solution of a binder of the Sokrat-binder type, or an alcoholic solution of polyvinyl butyral for the modification of polyacrylonitrile fibres before thermo-oxidation, which ensure obtaining a stable and uniform carbon-containing film on the fibre surface has been established.-- The use of ethylene glycol as the dispersion medium leads to retention of the strength of fibres after heat treatment at the level of the starting fibres and reduces the specific bulk electrical resistance.-- Application of aqueous solutions of the Sokrat-binder aids in preserving fibre strength during thermo-oxidation. The linear density of the fibre and its ability to be oxidized are increased, but the specific bulk electrical resistance and elongation are reduced.-- The use of alcoholic solutions of polyvinyl butyral makes it possible not only to preserve fibre strength but also to considerably increase it during the thermo-oxidation process. Thereupon, the linear density of the fibres is significantly reduced, and at a dispersion content of 10% by wt. technical carbon, one can obtain electrically-conducting oxidized fibres.Translated from Khimicheskie Volokna, No. 4, pp. 36–37, July–August, 1991. 相似文献
9.
Galina M. Viryasova Ekaterina A. Golenkina Tibor Hianik Nataliya V. Soshnikova Nina G. Dolinnaya Tatjana V. Gaponova Yulia M. Romanova Galina F. Sudina 《International journal of molecular sciences》2021,22(5)
Neutrophil-mediated innate host defense mechanisms include pathogen elimination through bacterial phagocytosis, which activates the 5-lipoxygenase (5-LOX) product synthesis. Here, we studied the effect of synthetic oligodeoxyribonucleotides (ODNs), which mimic the receptor-recognized sites of bacterial (CpG-ODNs) and genomic (G-rich ODNs) DNAs released from the inflammatory area, on the neutrophil functions after cell stimulation with Salmonella typhimurium. A possible mechanism for ODN recognition by Toll-like receptor 9 (TLR9) and RAGE receptor has been proposed. We found for the first time that the combination of the magic peptide LRR11 from the leucine-rich repeat (LRR) of TLR9 with the CpG-ODNs modulates the uptake and signaling from ODNs, in particular, dramatically stimulates 5-LOX pathway. Using thickness shear mode acoustic method, we confirmed the specific binding of CpG-ODNs, but not G-rich ODN, to LRR11. The RAGE receptor has been shown to play an important role in promoting ODN uptake. Thus, FPS-ZM1, a high-affinity RAGE inhibitor, suppresses the synthesis of 5-LOX products and reduces the uptake of ODNs by neutrophils; the inhibitor effect being abolished by the addition of LRR11. The results obtained revealed that the studied peptide-ODN complexes possess high biological activity and can be promising for the development of effective vaccine adjuvants and antimicrobial therapeutics. 相似文献
10.
Oleksandr Gryshkov Vitalii Mutsenko Dmytro Tarusin Diaa Khayyat Ortwin Naujok Ekaterina Riabchenko Yuliia Nemirovska Arseny Danilov Alexander Y. Petrenko Birgit Glasmacher 《International journal of molecular sciences》2021,22(6)
Alginate as a versatile naturally occurring biomaterial has found widespread use in the biomedical field due to its unique features such as biocompatibility and biodegradability. The ability of its semipermeable hydrogels to provide a favourable microenvironment for clinically relevant cells made alginate encapsulation a leading technology for immunoisolation, 3D culture, cryopreservation as well as cell and drug delivery. The aim of this work is the evaluation of structural properties and swelling behaviour of the core-shell capsules for the encapsulation of multipotent stromal cells (MSCs), their 3D culture and cryopreservation using slow freezing. The cells were encapsulated in core-shell capsules using coaxial electrospraying, cultured for 35 days and cryopreserved. Cell viability, metabolic activity and cell–cell interactions were analysed. Cryopreservation of MSCs-laden core-shell capsules was performed according to parameters pre-selected on cell-free capsules. The results suggest that core-shell capsules produced from the low viscosity high-G alginate are superior to high-M ones in terms of stability during in vitro culture, as well as to solid beads in terms of promoting formation of viable self-assembled cellular structures and maintenance of MSCs functionality on a long-term basis. The application of 0.3 M sucrose demonstrated a beneficial effect on the integrity of capsules and viability of formed 3D cell assemblies, as compared to 10% dimethyl sulfoxide (DMSO) alone. The proposed workflow from the preparation of core-shell capsules with self-assembled cellular structures to the cryopreservation appears to be a promising strategy for their off-the-shelf availability. 相似文献