全文获取类型
收费全文 | 1172篇 |
免费 | 60篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 20篇 |
化学工业 | 500篇 |
金属工艺 | 31篇 |
机械仪表 | 14篇 |
建筑科学 | 5篇 |
矿业工程 | 25篇 |
能源动力 | 27篇 |
轻工业 | 10篇 |
水利工程 | 11篇 |
石油天然气 | 23篇 |
无线电 | 106篇 |
一般工业技术 | 281篇 |
冶金工业 | 28篇 |
原子能技术 | 9篇 |
自动化技术 | 150篇 |
出版年
2023年 | 17篇 |
2022年 | 108篇 |
2021年 | 85篇 |
2020年 | 53篇 |
2019年 | 43篇 |
2018年 | 51篇 |
2017年 | 50篇 |
2016年 | 55篇 |
2015年 | 33篇 |
2014年 | 56篇 |
2013年 | 86篇 |
2012年 | 75篇 |
2011年 | 79篇 |
2010年 | 50篇 |
2009年 | 53篇 |
2008年 | 41篇 |
2007年 | 37篇 |
2006年 | 31篇 |
2005年 | 30篇 |
2004年 | 31篇 |
2003年 | 14篇 |
2002年 | 21篇 |
2001年 | 12篇 |
2000年 | 6篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1997年 | 11篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1992年 | 5篇 |
1991年 | 8篇 |
1990年 | 5篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 4篇 |
1970年 | 3篇 |
1966年 | 2篇 |
1965年 | 5篇 |
排序方式: 共有1240条查询结果,搜索用时 0 毫秒
71.
Constantin Turta Silvia Melnic Denis Prodius Fliur Macaev Helene Stoeckli-Evans Patricia Ruiz Dmitry Muraviev Serghei Pogrebnoi Zinaida Ribkovskaia Valeriu Mereacre Yanhua Lan Annie K. Powell 《Inorganic chemistry communications》2010,13(12):1402-1405
High-temperature solution phase reaction of iron(III)-furoate in sunflower oil, in the presence of trichloroacetic acid and 1,2-hexadecylamine leads to iron(III) oxide (amorphous and γ-Fe2O3) nanoparticles with sizes about 1.3 nm in diameter (method “A”), and about 5.5 nm (amorphous Fe2O3) from the “sunflower oil/oxadiazol” system (method “B”). 相似文献
72.
Yulia V. Gerasimova Dr. Aaron Hayson Jack Ballantyne Dr. Dmitry M. Kolpashchikov Dr. 《Chembiochem : a European journal of chemical biology》2010,11(12):1762-1768
Molecular beacon (MB) probes are dual‐labeled hairpin‐shaped oligodeoxyribonucleotides that are extensively used for real‐time detection of specific RNA/DNA analytes. In the MB probe, the loop fragment is complementary to the analyte: therefore, a unique probe is required for the analysis of each new analyte sequence. The conjugation of an oligonucleotide with two dyes and subsequent purification procedures add to the cost of MB probes, thus reducing their application in multiplex formats. Here we demonstrate how one MB probe can be used for the analysis of an arbitrary nucleic acid. The approach takes advantage of two oligonucleotide adaptor strands, each of which contains a fragment complementary to the analyte and a fragment complementary to an MB probe. The presence of the analyte leads to association of MB probe and the two DNA strands in quadripartite complex. The MB probe fluorescently reports the formation of this complex. In this design, the MB does not bind the analyte directly; therefore, the MB sequence is independent of the analyte. In this study one universal MB probe was used to genotype three human polymorphic sites. This approach promises to reduce the cost of multiplex real‐time assays and improve the accuracy of single‐nucleotide polymorphism genotyping. 相似文献
73.
Dmitry V. Orekhov Oleg A. Kazantsev Sergey V. Orekhov Alexey P. Sivokhin Denis M. Kamorin Alexander S. Simagin Maria V. Savinova Evgeniya A. Bolshakova Michail S. Korotaev 《应用聚合物科学杂志》2021,138(38):50982
Thermoresponsive PEG-based (PEG stands polyethylene glycol) polymers are unique for use in medicine because of their low toxicity, good biocompatibility and biodegradability, but usually more hydrophobic and more toxic comonomers are used to adjust lower critical solution temperature (LCST). A convenient way to overcome this problem and to finely tune LCST is to use alkoxy oligo(ethylene glycol)- or alkoxy oligo(propylene glycol) (meth)acrylates as starting comonomers. Here we report on the conditions for the simple and affordable synthesis of methoxy oligo(propylene glycol) (meth)acrylate- and methoxy oligo(propylene glycol)-block-oligo(ethylene glycol) (meth)acrylate-based macromonomers with high yields (80%–98.7%) by the acid-catalyzed esterification of (meth)acrylic acid with alkoxy oligo(alkylene glycols) containing oligo(ethylene glycol) (OEG) and/or oligo(propylene glycol) (OPG) blocks. p-Toluene sulphonic acid (pTSA), alkyl(C12–C14)benzene sulfonic acid (ABSA) and H2SO4 were used as catalysts. It has been shown that pTSA and ABSA are practically the same in catalytic activity and are superior to sulfuric acid. The reaction orders with respect to catalyst was found to be close to 1 in all cases. It has been shown that the reaction is actually insensitive to the lengths of OEG and OPG blocks, as well as to the structure of the terminal alkyl group, while the esterification of acrylic acid (AA) proceeds much faster compared to methacrylic acid (MAA) one under the same conditions. The influence of temperature on the equilibrium conversions of alcohols was determined, which were found to be 89%–93% for the esterification of AA and 61%–86% for MAA in the temperature range of 60–120°C. A further increase in conversion was achieved by introducing an azeotropic agent (toluene), its optimal concentration was found to be 10%–15%. 相似文献
74.
Zhenya Wang Hao Guo De Ning Xiaobai Ma Lirong Zheng Dmitry Smirnov Kai Sun Dongfeng Chen Limei Sun Xiangfeng Liu 《Journal of the American Ceramic Society》2021,104(11):5934-5945
Li4Ti5O12 (LTO) attracts great interest due to the “zero strain” during cycles but the poor electronic and ionic conductivity critically impede the practical application. Herein, we report a synergy strategy of tuning localized electrons to shift Fermi level and band gap by Mg/Zr co-doping and oxygen vacancy incorporation, which significantly improves Li+ and electronic transport. More importantly, the intrinsic synergistic mechanism has been revealed by neutron diffraction, X-ray absorption spectra, and first-principles calculations. The “elastic effect” of lattice induced by Mg/Zr co-doping allows LTO to accommodate more oxygen vacancies to a certain degree without a severe lattice distortion, which largely improves the electronic conductivity. Mg/Zr co-doping and oxygen vacancy incorporation effectively enhanced the dynamic characteristics of LTO electrode, achieving the excellent rate performance (90 mAh/g at 20C) and cycle stability (96.9% after 500 cycles at 10C). First-principles calculations confirm Fermi level shifts to the conduction band, and the band gap becomes narrowed due to the synergistic modulation, and the intrinsic mechanism of the enhanced electronic and Li-ion conductivity is clarified. This study offers some insights into achieving the fast Li+ insertion/extraction by tuning the crystal and electronic structure with lattice doping and oxygen vacancy engineering. 相似文献
75.
Diana Salikhova Tatiana Bukharova Elvira Cherkashova Daria Namestnikova Georgy Leonov Maria Nikitina Ilya Gubskiy Gevorg Akopyan Andrey Elchaninov Konstantin Midiber Natalia Bulatenco Victoria Mokrousova Andrey Makarov Konstantin Yarygin Vladimir Chekhonin Liudmila Mikhaleva Timur Fatkhudinov Dmitry Goldshtein 《International journal of molecular sciences》2021,22(9)
Transplantation of various types of stem cells as a possible therapy for stroke has been tested for years, and the results are promising. Recent investigations have shown that the administration of the conditioned media obtained after stem cell cultivation can also be effective in the therapy of the central nervous system pathology (hypothesis of their paracrine action). The aim of this study was to evaluate the therapeutic effects of the conditioned medium of hiPSC-derived glial and neuronal progenitor cells in the rat middle cerebral artery occlusion model of the ischemic stroke. Secretory activity of the cultured neuronal and glial progenitor cells was evaluated by proteomic and immunosorbent-based approaches. Therapeutic effects were assessed by overall survival, neurologic deficit and infarct volume dynamics, as well as by the end-point values of the apoptosis- and inflammation-related gene expression levels, the extent of microglia/macrophage infiltration and the numbers of formed blood vessels in the affected area of the brain. As a result, 31% of the protein species discovered in glial progenitor cells-conditioned medium and 45% in neuronal progenitor cells-conditioned medium were cell type specific. The glial progenitor cell-conditioned media showed a higher content of neurotrophins (BDNF, GDNF, CNTF and NGF). We showed that intra-arterial administration of glial progenitor cells-conditioned medium promoted a faster decrease in neurological deficit compared to the control group, reduced microglia/macrophage infiltration, reduced expression of pro-apoptotic gene Bax and pro-inflammatory cytokine gene Tnf, increased expression of anti-inflammatory cytokine genes (Il4, Il10, Il13) and promoted the formation of blood vessels within the damaged area. None of these effects were exerted by the neuronal progenitor cell-conditioned media. The results indicate pronounced cytoprotective, anti-inflammatory and angiogenic properties of soluble factors secreted by glial progenitor cells. 相似文献
76.
77.
78.
Dmitry A. Bratsun 《Microgravity science and technology》2009,21(Z1):153-158
We study two-phase flow in a tall vertical slot differently heated from the side walls and subjected to finite-frequency horizontal
vibrations along the layer. One of the phases is fluid and another phase consists of the small solid particles. We show that
there is the maximum vibration frequency higher which the unsteady forces, such as the Basset history force and virtual mass
effect, may, generally, be of great importance and have to be taken into account. By using the asymptotic expansion technique
we derive the set of governing equations describing the dynamics of such a system within the framework of the generalized
Boussinesq approximation. The pulsed base flow is obtained and its linear stability is analysed. The comparison with the recent
experimental data is made. 相似文献
79.
The object of this paper is to explain a system of Internet traffic caching. The task is to create an analytical model of a cache system linking its size with other parameters by boundary conditions. A definition of a dynamic cache model is introduced. The parameters of a cache system are calculated using the Zipf's first law and Zipf-like distribution. The correspondence between size of a cache system and aggregated bandwidth of external links is derived. 相似文献
80.
Zimnyakov DA Agafonov DN Sviridov AP Omel'chenko AI Kuznetsova LV Bagratashvili VN 《Applied optics》2002,41(28):5989-5996
Measurements of the contrast value of time-averaged speckle-modulated images of cartilage tissue are used to study tissue thermal modification in the case of laser-light treatment. This modification is related to thermally induced internal stress relaxation in the matrix of the treated tissue. The specific feature of the evolution of time-averaged speckle contrast with a change in the current temperature of modified collagen tissue is the typical looplike form of the contrast-temperature dependencies associated with irreversible changes in tissue structure and correlated with changes in the tissue diffuse transmittance and the tissue internal stress mentioned by other researchers. 相似文献