全文获取类型
收费全文 | 491篇 |
免费 | 16篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 146篇 |
金属工艺 | 15篇 |
机械仪表 | 23篇 |
建筑科学 | 11篇 |
矿业工程 | 1篇 |
能源动力 | 10篇 |
轻工业 | 63篇 |
石油天然气 | 3篇 |
无线电 | 25篇 |
一般工业技术 | 89篇 |
冶金工业 | 59篇 |
原子能技术 | 8篇 |
自动化技术 | 52篇 |
出版年
2024年 | 3篇 |
2023年 | 3篇 |
2022年 | 10篇 |
2021年 | 17篇 |
2020年 | 11篇 |
2019年 | 11篇 |
2018年 | 23篇 |
2017年 | 12篇 |
2016年 | 16篇 |
2015年 | 19篇 |
2014年 | 17篇 |
2013年 | 32篇 |
2012年 | 24篇 |
2011年 | 26篇 |
2010年 | 20篇 |
2009年 | 19篇 |
2008年 | 13篇 |
2007年 | 13篇 |
2006年 | 15篇 |
2005年 | 9篇 |
2004年 | 14篇 |
2003年 | 10篇 |
2002年 | 12篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 21篇 |
1997年 | 15篇 |
1996年 | 11篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1990年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1978年 | 2篇 |
1977年 | 5篇 |
1976年 | 8篇 |
1974年 | 4篇 |
1971年 | 4篇 |
1938年 | 1篇 |
1914年 | 1篇 |
1906年 | 5篇 |
1905年 | 1篇 |
排序方式: 共有507条查询结果,搜索用时 31 毫秒
1.
Cz. Woźniak 《Acta Mechanica》1989,78(1-2):81-94
Summary In this paper a new high efficiency C-O grid coupled with the potential flow solver based on the finite volume technique is given. It significantly reduces the CPU time and increases the computational efficiency. In order to improve the accuracy of traditional potential method a shock point operator is used to account for entropy correction. Some calculated results of 2D inviscid, viscous/inviscid interaction and 3D inviscid flow indicate that nonisentropic potential method produces results closer to Euler solution as well as experimental data, while its computational efforts are nearly the same as the usual isentropic potential method.With 9 Figures 相似文献
2.
Victor Chabanenko Roman Puźniak Adam Nabiałek Sergei Vasiliev Vladimir Rusakov Loh Huanqian Ritta Szymczak Henryk Szymczak Jan Jun Janusz Karpiński Vitaly Finkel 《Journal of Low Temperature Physics》2003,130(3-4):175-191
We present a study of magneto-thermal instabilities in polycrystalline MgB2 superconductor, by magnetic hysteresis loop measurements and by investigations of magnetic flux dynamics with a miniature Hall probe. Temperature and magnetic field ranges where the flux jumps may be observed have been determined. On the basis of measurements of the magnetic flux dynamics, an average magnetic diffusivity describing the process of the flux jump is estimated. This parameter is compared with the thermal and magnetic diffusivities calculated on the basis of available data for thermal conductivity, heat capacity and resistivity. It is shown that the estimated value of the field of the first flux jump is influenced significantly by the field dependence of specific heat. In order to explain the observed phenomenon, the temperature reached by the sample during the flux jump at different magnetic fields is calculated. 相似文献
3.
The apparent tensile strength of technical flax fibers was determined in single‐fiber tests at various clamping lengths (20, 40, and 80 mm) and the outcome was compared with literature data. It was demonstrated that the strength of flax at each clamping length obeyed the two‐parameter Weibull model. The failure mode and sequence were studied in situ (i.e., during loading) by SEM and acoustic emission (AE). The failure sequence (axial splitting of the technical fiber along its elementary constituents, radial cracking of the elementary fibers, multiple fracture of the elementary fibers) concluded reflected the hierarchical build‐up of the flax bast fibers. To the above failure events AE amplitude ranges were assigned. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3638–3645, 2003 相似文献
4.
S Thisted Lambertz A Ballagi-Pordány A Nilsson P Norberg ML Danielsson-Tham 《Canadian Metallurgical Quarterly》1996,81(3):303-308
The beige mutation is a murine autosomal recessive disorder, resulting in hypopigmentation, bleeding and immune cell dysfunction. The gene defective in beige is thought to be a homologue of the gene for the human disorder Chediak-Higashi syndrome. We have identified the murine beige gene by in vitro complementation and positional cloning, and confirmed its identification by defining mutations in two independent mutant alleles. The sequence of the beige gene message shows strong nucleotide homology to multiple human ESTs, one or more of which may be associated with the Chediak-Higashi syndrome gene. The amino acid sequence of the Beige protein revealed a novel protein with significant amino acid homology to orphan proteins identified in Saccharomyces cerevisiae, Caenorhabditis elegans and humans. 相似文献
5.
6.
Laura Nicolle Jens Casper Melanie Willimann Cline M. A. Journot Pascal Detampel Toma Einfalt Hiu Man Grisch-Chan Beat Thny Sandrine Gerber-Lemaire Jrg Huwyler 《International journal of molecular sciences》2021,22(8)
There is an increasing interest in cationic polymers as important constituents of non-viral gene delivery vectors. In the present study, we developed a versatile synthetic route for the production of covalent polymeric conjugates consisting of water-soluble depolymerized chitosan (dCS; MW 6–9 kDa) and low molecular weight polyethylenimine (PEI; 2.5 kDa linear, 1.8 kDa branched). dCS-PEI derivatives were evaluated based on their physicochemical properties, including purity, covalent bonding, solubility in aqueous media, ability for DNA condensation, and colloidal stability of the resulting polyplexes. They were complexed with non-integrating DNA vectors coding for reporter genes by simple admixing and assessed in vitro using liver-derived HuH-7 cells for their transfection efficiency and cytotoxicity. Using a rational screening cascade, a lead compound was selected (dCS-Suc-LPEI-14) displaying the best balance of biocompatibility, cytotoxicity, and transfection efficiency. Scale-up and in vivo evaluation in wild-type mice allowed for a direct comparison with a commercially available non-viral delivery vector (in vivo-jetPEI). Hepatic expression of the reporter gene luciferase resulted in liver-specific bioluminescence, upon intrabiliary infusion of the chitosan-based polyplexes, which exceeded the signal of the in vivo jetPEI reference formulation by a factor of 10. We conclude that the novel chitosan-derivative dCS-Suc-LPEI-14 shows promise and potential as an efficient polymeric conjugate for non-viral in vivo gene therapy. 相似文献
7.
Hybrid Model of High Speed Machining Centre Headstock 总被引:1,自引:0,他引:1
A hybrid high-speed machining centre headstock model based on two computation methods: the finite element method and the finite difference method is presented. The model allows one to calculate precisely the headstock's indices on the basis of which its optimal operating characteristics can be determined. The presented modelling methods allow one to evaluate a design from thermal, stiffness and durability points of view. By way of illustration, the behaviour of three machining centre headstocks with: an electrospindle on rolling bearings, a conventional spindle and an electrospindle on aerostatic bearings are modelled using the hybrid model. 相似文献
8.
In this paper we consider robust stabilization of the class of nonlinear plants of the form $$\dot x = f(x) + \sum\limits_{i = 1}^m {g_i } (x)u_i (t),$$ which are equivalent, under smooth state space coordinate transformations and nonlinear state feedback, to controllable systems. This approach is very sensitive for unknown parameters' values. Parameter adaptation may be used as a technique to robustify minimum-phase systems [3]. We give an example of a locally stable adaptive tracking system in which the last assumption is weakened. The minimum-phase plant considered in the paper is a current-controlled squirrel cage induction motor. 相似文献
9.
10.
G.D. Lei B.J. Adelman J. Srkny W.M.H. Sachtler 《Applied catalysis. B, Environmental》1995,5(3):245-256
A combined Fourier transform IR (FT-IR) and electron paramagnetic resonance (EPR) study shows that copper in ‘excessively exchanged’ Cu/ZSM-5 is initially present as OH bridged Cu2+ dimers, besides isolated Cu2+ ions. Upon heating, the dimers lose water and become oxygen bridged [Cu---O---Cu]2+ complexes. These are ‘EPR-silent’, presumably as a consequence of antiferromagnetic coupling of the unpaired electrons in each Cu2+; they are, however, detectable by their perturbation of the lattice vibrations, detected by a FT-IR band at 918–923 cm−1. Reduction by hydrogen or carbon monoxide converts the [Cu---O---Cu]2+ complexes to pairs of Cu+ ions, while the color changes from green to grey. Reductive adsorption of nitrogen monoxide on Cu2+ results in the formation of Cu+---NO+. Destructive thermal desorption of nitrogen monoxide at 100°C not only restores the Cu2+ ions, but also appears to regenerate the [Cu---O---Cu]2+ complex. The results suggest that pairs of copper ions are instrumental in the catalytic decomposition of nitrogen monoxide. 相似文献