全文获取类型
收费全文 | 801篇 |
免费 | 60篇 |
专业分类
电工技术 | 7篇 |
综合类 | 1篇 |
化学工业 | 238篇 |
金属工艺 | 15篇 |
机械仪表 | 15篇 |
建筑科学 | 10篇 |
矿业工程 | 1篇 |
能源动力 | 22篇 |
轻工业 | 26篇 |
水利工程 | 3篇 |
石油天然气 | 1篇 |
无线电 | 90篇 |
一般工业技术 | 284篇 |
冶金工业 | 37篇 |
原子能技术 | 7篇 |
自动化技术 | 104篇 |
出版年
2023年 | 11篇 |
2022年 | 40篇 |
2021年 | 37篇 |
2020年 | 25篇 |
2019年 | 17篇 |
2018年 | 33篇 |
2017年 | 26篇 |
2016年 | 27篇 |
2015年 | 15篇 |
2014年 | 40篇 |
2013年 | 52篇 |
2012年 | 45篇 |
2011年 | 67篇 |
2010年 | 29篇 |
2009年 | 33篇 |
2008年 | 52篇 |
2007年 | 34篇 |
2006年 | 31篇 |
2005年 | 36篇 |
2004年 | 34篇 |
2003年 | 39篇 |
2002年 | 27篇 |
2001年 | 12篇 |
2000年 | 9篇 |
1999年 | 14篇 |
1998年 | 13篇 |
1997年 | 7篇 |
1996年 | 8篇 |
1995年 | 12篇 |
1994年 | 6篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 6篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1984年 | 1篇 |
1981年 | 2篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有861条查询结果,搜索用时 0 毫秒
841.
Yulia Plekhanova Sergei Tarasov Aleksandr Bykov Anatoly Reshetilov 《IET nanobiotechnology / IET》2019,13(3):332
This work considers the effects of various carbon nanomaterials and fibres on bioelectrocatalytic and respiratory activity of bacterial cells during the oxidation of ethanol in the presence of an electron transport mediator. Gluconobacter oxydans sbsp. industrius VKM B‐1280 cells were immobilised on the surfaces of graphite electrodes and had an adsorption contact with a nanomaterial (multi‐walled carbon nanotubes, thermally expanded graphite, highly oriented pyrolytic graphite, graphene oxide, reduced graphene oxide). The electrochemical parameters of the electrodes (the polarisation curves, the value of generated current at the introduction of substrate, the impedance characteristics) were measured in two‐electrode configuration. Modification by multi‐walled carbon nanotubes led to the increase of microbial fuel cell (MFC) electric power by 26%. The charge transfer resistance of modified electrodes was 47% lower than unmodified ones. Thermally expanded and pyrolytic graphites had a slight negative effect on the electrochemical properties of modified electrodes. The respiratory activity of bacterial cells did not change in the presence of nanomaterials. The data can be used in the development of microbial biosensors and MFC electrodes based on Gluconobacter cells.Inspec keywords: nanofabrication, catalysis, microorganisms, adsorption, charge exchange, microbial fuel cells, electrochemical electrodes, graphite, graphene, oxidation, multi‐wall carbon nanotubes, cellular biophysicsOther keywords: reduced graphene oxide, electrochemical parameters, two‐electrode configuration, multiwalled carbon nanotubes, microbial fuel cell, respiratory activity, bacterial cells, microbial biosensors, MFC electrodes, microbial living cells, electron transport mediator, graphite electrodes, adsorption contact, highly oriented pyrolytic graphite, Gluconobacter oxydans sbsp. industrius VKM B‐1280 cells, polarisation curves, bioelectrocatalytic activity, ethanol, thermally expanded graphite, charge transfer resistance, C 相似文献
842.
Michael J. Spriggs J. Mark Keil Sergei Bespamyatnikh Michael Segal Jack Snoeyink 《Algorithmica》2004,38(4):577-589
Given a set P of points in the plane,
a geometric minimum-diameter spanning tree (GMDST) of P is a
spanning tree of P such that the longest path through the
tree is minimized.
For several years, the best upper bound on the time to
compute a GMDST was cubic with respect to the
number of points in the input set.
Recently, Timothy Chan introduced a subcubic time
algorithm.
In this paper we present an algorithm
that generates a tree whose diameter is no more than (1 + )
times that of a GMDST, for any > 0.
Our algorithm reduces the problem to several grid-aligned versions of the
problem and runs within time $O(-3+ n)
and space O(n). 相似文献
843.
Sergei A. Decterov Youn-Bae Kang In-Ho Jung 《Journal of Phase Equilibria and Diffusion》2009,30(5):443-461
Computerized thermodynamic databases for solid and liquid metals, slag, and solid oxide phases in the Al2O3-CaO-CoO-CrO-Cr2O3-FeO-Fe2O3-MgO-MnO-NiO-SiO2 system (with dissolved S and P) have been developed by critical evaluation/optimization of various available phase equilibrium
and thermodynamic data. The databases contain parameters of models specifically developed for molten slags, liquid steel,
and solid oxide solutions such as spinel, pyroxenes, olivine, monoxide (wustite, periclase, lime), corundum, etc. By means
of the optimization process, model parameters are found which reproduce various thermodynamic and phase equilibrium data within
experimental error limits. Furthermore, the models permit extrapolation into regions of temperature and composition where
data are not available. The databases are automatically accessed by user-friendly software that calculates complex equilibria
involving slag, metals, refractories, and gases simultaneously, for systems with many components, over wide ranges of temperature,
oxygen potential, and pressure. A short review of the available databases is presented. The critical evaluation/optimization
procedure is outlined using the Al2O3-CaO-FeO-Fe2O3-MgO-SiO2 and Al2O3-CaO-MnO-SiO2 systems as examples. Several applications of the databases to deoxidation, dehydrogenation, and dephosphorization of iron
and to inclusion control in steel are discussed. 相似文献
844.
Benny Applebaum Sergei Artemenko Ronen Shaltiel Guang Yang 《Computational Complexity》2016,25(2):349-418
A circuit C compresses a function \({f : \{0,1\}^n\rightarrow \{0,1\}^m}\) if given an input \({x\in \{0,1\}^n}\), the circuit C can shrink x to a shorter ?-bit string x′ such that later, a computationally unbounded solver D will be able to compute f(x) based on x′. In this paper we study the existence of functions which are incompressible by circuits of some fixed polynomial size \({s=n^c}\). Motivated by cryptographic applications, we focus on average-case \({(\ell,\epsilon)}\) incompressibility, which guarantees that on a random input \({x\in \{0,1\}^n}\), for every size s circuit \({C:\{0,1\}^n\rightarrow \{0,1\}^{\ell}}\) and any unbounded solver D, the success probability \({\Pr_x[D(C(x))=f(x)]}\) is upper-bounded by \({2^{-m}+\epsilon}\). While this notion of incompressibility appeared in several works (e.g., Dubrov and Ishai, STOC 06), so far no explicit constructions of efficiently computable incompressible functions were known. In this work, we present the following results:
相似文献
- (1)Assuming that E is hard for exponential size nondeterministic circuits, we construct a polynomial time computable boolean function \({f:\{0,1\}^n\rightarrow \{0,1\}}\) which is incompressible by size n c circuits with communication \({\ell=(1-o(1)) \cdot n}\) and error \({\epsilon=n^{-c}}\). Our technique generalizes to the case of PRGs against nonboolean circuits, improving and simplifying the previous construction of Shaltiel and Artemenko (STOC 14).
- (2)We show that it is possible to achieve negligible error parameter \({\epsilon=n^{-\omega(1)}}\) for nonboolean functions. Specifically, assuming that E is hard for exponential size \({\Sigma_3}\)-circuits, we construct a nonboolean function \({f:\{0,1\}^n\rightarrow \{0,1\}^m}\) which is incompressible by size n c circuits with \({\ell=\Omega(n)}\) and extremely small \({\epsilon=n^{-c} \cdot 2^{-m}}\). Our construction combines the techniques of Trevisan and Vadhan (FOCS 00) with a new notion of relative error deterministic extractor which may be of independent interest.
- (3)We show that the task of constructing an incompressible boolean function \({f:\{0,1\}^n\rightarrow \{0,1\}}\) with negligible error parameter \({\epsilon}\) cannot be achieved by “existing proof techniques”. Namely, nondeterministic reductions (or even \({\Sigma_i}\) reductions) cannot get \({\epsilon=n^{-\omega(1)}}\) for boolean incompressible functions. Our results also apply to constructions of standard Nisan-Wigderson type PRGs and (standard) boolean functions that are hard on average, explaining, in retrospect, the limitations of existing constructions. Our impossibility result builds on an approach of Shaltiel and Viola (STOC 08).
845.
Sergei V. Voitekhovich Tatiyana V. Serebryanskaya Pavel N. Gaponik Ludmila S. Ivashkevich Alexander S. Lyakhov Oleg A. Ivashkevich 《Inorganic chemistry communications》2010,13(8):949-951
Tetrazol-2-ylacetic acid (2-TzaH) was found to react with CuCl2, PdCl2, and K2PtCl4 in water giving Cu(2-Tza)2, PdCl2(2-TzaH)2·2H2O and PtCl2(2-TzaH)2, correspondingly. Obtained complexes, being the first reported examples of coordination compounds derived from 2-TzaH, have been characterized by IR spectroscopy, thermal and X-ray diffraction methods. 2-TzaH was found to act as a monodentate ligand coordinated to the metal ion via N4 atom of heteroring in palladium complex and as tridentate bridging ligand coordinated via N4 atom and two oxygen atoms in copper complex. Cu(2-Tza)2 presents 2D coordination polymer, whereas PdCl2(2-TzaH)2·2H2O is molecular complex. 相似文献
846.
Sergei Kniajanski Robert E. Colborn Brian C. Bales Orrie Riccobono Aaron J. Dulgar‐Tulloch Judith Stein Binil I. I. Kandapallil 《应用聚合物科学杂志》2013,129(4):1726-1733
Superparamagnetic iron oxide (SPIO) incorporated polystyrene beads of uniform size distribution (~170 nm) and high magnetic content (~40%) are synthesized by emulsion styrene polymerization in the presence of functionalized SPIO. The role of surface functionality on the polymerization process and SPIO incorporation is investigated by carrying out styrene emulsion polymerizations with different functionalities on SPIO. A unique combination of oleic acid and (2‐acetoacetoxy) ethyl methacrylate as surface ligands for SPIO is used to attain the best magnetic beads. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
847.
Sergey E. Lyubimov Ilya V. Kuchurov Eugenie A. Rastorguev Sergei G. Zlotin 《The Journal of Supercritical Fluids》2010,54(2):218-221
Pd-catalyzed amination of allylic carbonates with N-(ortho-carboran-3-yl)-N-methylamine was carried out in supercritical CO2. It has been demonstrated that complete conversion of allylic carbonates to the corresponding carborane amines with excellent regioselectivity may be achieved in scCO2 (170 atm, 60 °C) using NaHCO3 as the acceptor base. The reaction offers a selective method for the preparation of allylic amines and provides a useful approach to new terpenoids. 相似文献
848.
Ian Rowe Min Guo Anthony Yasmann Abigail Cember Herman O. Sintim Sergei Sukharev 《International journal of molecular sciences》2015,16(8):17909-17932
Membrane permeability is a desired property in drug design, but there have been difficulties in quantifying the direct drug partitioning into native membranes. Platensimycin (PL) is a new promising antibiotic whose biosynthetic production is costly. Six dialkylamine analogs of PL were synthesized with identical pharmacophores but different side chains; five of them were found inactive. To address the possibility that their activity is limited by the permeation step, we calculated polarity, measured surface activity and the ability to insert into the phospholipid monolayers. The partitioning of PL and the analogs into the cytoplasmic membrane of E. coli was assessed by activation curve shifts of a re-engineered mechanosensitive channel, MscS, in patch-clamp experiments. Despite predicted differences in polarity, the affinities to lipid monolayers and native membranes were comparable for most of the analogs. For PL and the di-myrtenyl analog QD-11, both carrying bulky sidechains, the affinity for the native membrane was lower than for monolayers (half-membranes), signifying that intercalation must overcome the lateral pressure of the bilayer. We conclude that the biological activity among the studied PL analogs is unlikely to be limited by their membrane permeability. We also discuss the capacity of endogenous tension-activated channels to detect asymmetric partitioning of exogenous substances into the native bacterial membrane and the different contributions to the thermodynamic force which drives permeation. 相似文献
849.
Fires that involve upholstered furniture frequently begin as a smoldering combustion and, with time, transition to a flaming combustion, which sharply increases the level of hazard. Therefore, understanding how the compositions of the primary flammable components of the furniture, ie, flexible foam and upholstery fabric, affect this transition is important for fire safety considerations. In the current study, an experiment was designed to observe this transition using a sample consisting of 30 × 15 × 6 cm3 rectangular foam block covered with 30 × 15 cm2 piece of fabric. For a representative system of 1.8 lb/ft3 (29 kg/m3) flexible polyurethane foam and 11 oz (0.37 kg/m2) cotton fabric, 0.69 transition probability was measured. This probability decreased by a factor of 4 when a small amount of phosphorus‐based flame retardant, Fyrol® HF‐9, was added to the foam. The transition to flaming was speculated to be associated with the formation of adjacent pyrolysis and smoldering regions within the foam. The pyrolysis region, dominated by anaerobic decomposition, provided gaseous fuel, the ignition of which resulted in the transition. The smoldering region, dominated by oxidation reactions at the solid‐gas interface, generated the heat necessary to maintain the pyrolysis process and ignite the gaseous fuel. 相似文献
850.
The von Mises yield criterion and its associated flow rule are adopted to provide the exact analytic solution for the elastic-plastic stress and strain distributions within the discs with temperature-dependent properties subject to thermal loading by a uniform temperature field and subsequent unloading. This article examines the effect of temperature-dependent properties on the size of the plastic zone. Qualitative features of the solution are emphasized. The primary objective of the article is to provide a benchmark problem having the exact analytic solution for justifying the possibility to neglect or the necessity to account for temperature-dependency of thermomechanical properties in analysis of elastic-plastic discs under plane stress conditions. 相似文献