全文获取类型
收费全文 | 5510篇 |
免费 | 394篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 103篇 |
综合类 | 6篇 |
化学工业 | 1375篇 |
金属工艺 | 206篇 |
机械仪表 | 381篇 |
建筑科学 | 108篇 |
矿业工程 | 2篇 |
能源动力 | 236篇 |
轻工业 | 499篇 |
水利工程 | 13篇 |
石油天然气 | 2篇 |
无线电 | 997篇 |
一般工业技术 | 1123篇 |
冶金工业 | 267篇 |
原子能技术 | 69篇 |
自动化技术 | 525篇 |
出版年
2024年 | 3篇 |
2023年 | 49篇 |
2022年 | 62篇 |
2021年 | 135篇 |
2020年 | 98篇 |
2019年 | 149篇 |
2018年 | 162篇 |
2017年 | 177篇 |
2016年 | 201篇 |
2015年 | 174篇 |
2014年 | 269篇 |
2013年 | 381篇 |
2012年 | 349篇 |
2011年 | 439篇 |
2010年 | 330篇 |
2009年 | 374篇 |
2008年 | 316篇 |
2007年 | 246篇 |
2006年 | 259篇 |
2005年 | 216篇 |
2004年 | 189篇 |
2003年 | 177篇 |
2002年 | 156篇 |
2001年 | 136篇 |
2000年 | 122篇 |
1999年 | 90篇 |
1998年 | 146篇 |
1997年 | 100篇 |
1996年 | 73篇 |
1995年 | 51篇 |
1994年 | 46篇 |
1993年 | 30篇 |
1992年 | 25篇 |
1991年 | 29篇 |
1990年 | 18篇 |
1989年 | 20篇 |
1988年 | 12篇 |
1987年 | 9篇 |
1986年 | 10篇 |
1985年 | 17篇 |
1984年 | 11篇 |
1981年 | 10篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1969年 | 2篇 |
排序方式: 共有5912条查询结果,搜索用时 421 毫秒
61.
Optimization of reduction potential for electroseparation was studied for the recovery of gold, copper, and lead from acidic
solution. A linear sweep voltammetric method enabled us to determine characteristic reduction potentials for each metal and
the kinetics of the metal deposition indicated by current-voltage curves. In order to precipitate the metal species sequentially,
reduction potentials were examined for the individual and mixed solutions of Au(III), Cu(II), and Pb(II). The three metals
were reasonably well isolated from the mixed solutions such as Cu(II)/ Pb(II) and Au(III)/Cu(II)/Pb(II) in the order of the
corresponding reduction potentials, in particular, the mass transfer controlled reduction potentials, obtained from linear
sweep voltammetry (LSV) measurement. 相似文献
62.
Jung Joon Lee Heeyeon Kim Jae Hyun Koh Ara Jo Sang Heup Moon 《Applied catalysis. B, Environmental》2005,61(3-4):274-280
The performance of a new type of CoMoS/Al2O3 catalyst, with added fluorine and prepared by sonochemical and chemical vapor deposition (CVD) methods, was investigated in the hydrodesulfurization (HDS) of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). The catalyst, which was designed to contain optimum amounts of fluorine and cobalt, exhibited a higher activity, ca. 4.6 times higher activity particularly in the HDS of 4,6-DMDBT, than a fluorine-free catalyst prepared by a conventional impregnation method. The enhanced activity of the new catalyst can be attributed to the cumulative effects of individual factors involved in the catalyst preparation. That is, the use of a sonochemical synthesis led to a high dispersion of small MoS2 crystallites on the alumina, and the addition of the Co species to the catalyst by CVD caused a close interaction between the Co species and the MoS2 crystallites to produce numerous CoMoS species, which are the catalytically active species for HDS. The addition of fluorine increased the amounts of acidic sites in the catalyst, which promoted hydrogenation (HYD) route to a greater extent than the direct desulfurization (DDS) route in DBT HDS and both HYD and DDS routes to similar extents in the case of 4,6-DMDBT HDS. Accordingly, the addition of fluorine led to a greater increase in catalytic activity for 4,6-DMDBT HDS than for DBT HDS. 相似文献
63.
Won Seok Lyoo Han Do Ghim Hee‐Sam Kim Joon Ho Kim Sam Soo Kim Won Sik Yoon Jinwon Lee Sang‐Seob Lee 《应用聚合物科学杂志》2002,86(14):3667-3672
N‐Vinylcarbazole (VCZ) was solution‐polymerized in tetrahydrofuran (THF) at ?20, 0, and 20°C using the photoinitiation method; the effects of the amount of solvent, polymerization temperature, and photoinitiator concentration were investigated. On the whole, the experimental results corresponded to predicted ones. Low polymerization temperature using photoinitiation proved to be successful in obtaining poly(N‐vinylcarbazole) (PVCZ) of a high molecular weight with a smaller temperature rise during polymerization; nevertheless of free radical polymerization by 2,2′‐azobis(2,4‐dimethylvaleronitrile) (ADMVN). The photo‐solution polymerization rate of VCZ in THF was proportional to the 0.47 power of ADMVN concentration. The molecular weight was higher and the molecular weight distribution was narrower with PVCZ polymerized at lower temperatures. For PVCZ prepared in THF at ?20°C using a photoinitiator concentration of 0.00005 mol/mol of VCZ, a weight‐average molecular weight of 510,000 was obtained, with a polydispersity index of 1.73, and a degree of lightness converged to about 99%. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3667–3672, 2002 相似文献
64.
Neung‐Ju Lee Ja‐Chul Koo Sung‐Suk Ju Seong‐Bae Moon Won‐Jei Cho In‐Cheol Jeong Song‐Jae Lee Moo‐Youn Cho Emmanuel A Theodorakis 《Polymer International》2002,51(7):569-576
The attachment of anticancer agents to polymers is a promising approach towards reducing the toxic side‐effects and retaining the potent antitumour activity of these agents. A new tetrahydrophthalimido monomer containing 5‐fluorouracil (ETPFU) and its homopolymer and copolymers with acrylic acid (AA) and with vinyl acetate (VAc) have been synthesized and spectroscopically characterized. The ETPFU contents in poly(ETPFU‐co‐AA) and poly(ETPFU‐co‐VAc) obtained by elemental analysis were 21 mol% and 20 mol%, respectively. The average molecular weights of the polymers determined by gel permeation chromatography were as follows: Mn = 8900 g mol?1, Mw = 13 300 g mol?1, Mw/Mn = 1.5 for poly(ETPFU); Mn = 13 500 g mol?1, Mw = 16 600 g mol?1, Mw/Mn = 1.2 for poly(ETPFU‐co‐AA); Mn = 8300 g mol?1, Mw = 11 600 g mol?1, Mw/Mn = 1.4 poly(ETPFU‐co‐VAc). The in vitro cytotoxicity of the compounds against FM3A and U937 cancer cell lines increased in the following order: ETPFU > 5‐FU > poly(ETPFU) > poly(ETPFU‐co‐AA) > poly(ETPFU‐co‐VAc). The in vivo antitumour activities of all the polymers in Balb/C mice bearing the sarcoma 180 tumour cell line were greater than those of 5‐FU and monomer at the highest dose (800 mg kg?1). © 2002 Society of Chemical Industry 相似文献
65.
We determined the optimal reaction conditions to minimize the energy cost and the quantities of by‐products for a poly(ethylene terephthalate) process by using the iterative dynamic programming (IDP) algorithm. Here, we employed a sequence of three reactor models: the semibatch transesterification reactor model, the semibatch prepolymerization reactor model, and the rotating‐disc‐type polycondensation reactor model. We selectively chose or developed the reactor models by incorporating experimentally verified kinetic models reported in the literature. We established the model for the entire reactor system by connecting the three reactor models in series and by resolving some joint problems arising when different types of reactor models were interconnected. On the basis of the simulation results of the reactor system, we scrutinized the cause and effect between the reaction conditions and the final quality of the polymer product. Here, we set up the optimization strategy by using IDP on the basis of the integrated reactor model, and the process variables with significant influence on the properties of polymer were selected as control variables with the help of a simulation study. With this method, we could refine the reaction conditions at the end of each iteration step by contracting the spectra of control regions, and the iteration process finally stopped when the profile of the optimal trajectory converged. We also took the constraints on the control variables into account to guarantee polymer quality and to suppress side reactions. Constituting six different strategies by setting weighting vectors differently, we examined the differences in optimal trajectories, the trend of optimality, and the quality of the final polymer product. For each of the strategies, we conducted the optimization to examine whether the number‐average degree of polymerization approached the desired value. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 993–1008, 2002 相似文献
66.
Polyurethane macroiniferter/poly(methyl methacrylate) block copolymer dispersions with inverse core‐shell morphologies were obtained from 1,1,2,2,‐tetraphenylethane‐1,2‐diol, dimethylol propionic acid, 4,4′‐diphenylmethane diisocyanate, and poly(propylene glycol) via a living radical mechanism. Molecular weight, particle size and dispersion viscosity, and thermal, mechanical, and dynamic mechanical properties of the dispersion cast films are reported as a function of copolymerization time. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1971–1975, 2003 相似文献
67.
Inorganic–organic hybrid materials for the optical waveguide were synthesized by the sol–gel process starting from the acid-catalyzed solutions of phenyltrimethoxysilane, methyltriethoxysilane, and tetraethylorthosilicate. The control of the refractive index in the organically modified silicate films was achieved by varying the content of phenyltrimethoxysilane incorporated as a refractive index modifier. A single spin-coating with the precursor solution produced a crack-free buffer layer of 22-μm thickness with a dense microstructure. For the fabrication of the patterned guiding layer on top of the buffer layer, the microfluidic lithography method was used. The patterned microlines of the linewidth of 20–35 μm with a sharp edge definition could form by filling the precursor solutions into the microchannels associated with the polydimethylsiloxane microfluidic device. The patterned guiding layer was optically transparent as similar as the bare quartz glass at the wavelength above 500 nm and had a low propagation loss of 0.77 dB/cm at 1310 nm. 相似文献
68.
Young Tae Moon Do Kyung Kim Chong Hee Kim 《Journal of the American Ceramic Society》1995,78(4):1103-1106
Based on the principle that the solubility of a salt decreases as the dielectric constant of the solvent decreases, zirconia powders were prepared by heating a zirconyl chloride solution with a 2-PrOH-water mixture as the solvent. The morphology, size, and size distribution of the resulting particles were highly sensitive to the heating method used on the starting solution. Particles formed under conventional heating methods were polydisperse, agglomerated spherical, or irregularly shaped because of inhomogeneous precipitation through the temperature gradient, the shear force induced by stirring, compositional nonuniformity, and the low heating rate. The present study demonstrated that microwaves provide an excellent means of heating uniformly and rapidly without stirring. The particles resulting from microwave treatment were monodisperse and spherical, with a mean diameter of 0.28 μm. 相似文献
69.
Electrochemical cell current requirements for toxic organic waste destruction in Ce(IV)-mediated electrochemical oxidation process 总被引:1,自引:0,他引:1
Vasily V. Kokovkin Sang Joon Chung Subramanian Balaji Manickam Matheswaran Il-Shik Moon 《Korean Journal of Chemical Engineering》2007,24(5):749-756
The electrochemical cell for cerium oxidation and reactor for organic destruction are the most important operation units for
the successful working mediated electrochemical oxidation (MEO) process. In this study, electrochemical cells with DSA electrodes
of two types, single stack and double stack connected in series, were used. The performances towards the electrochemical generation
of Ce(IV) in nitric acid media at 80 °C were studied. The current-voltage curves and cerium electrolysis kinetics showed the
dependence on number of cell stacks needed to be connected in series for the destruction of a given quantity of organic pollutant.
The presence of an optimum region for Ce(III) oxidation with a contribution of oxygen evolution, especially at low Ce(III)
concentration (high conversion ratios), was found. The cells were applied for the Ce(IV) regeneration during the organic destruction.
The cell and reactor processes were fitted in a simple model proposed and used to calculate the current needed in terms of
Ce(III) oxidation rate and the number of cell stacks required for maintaining Ce(IV)/Ce(III) ratio at the same level during
the organic destruction. This consideration was based on the kinetic model previously developed by us for the organic destruction
in the MEO process. 相似文献
70.
The dynamical behavior of polymers with molecular weight distribution is analyzed from the standpoint of reptation and tube
renewal. In a binary blend where the entanglements between longer chains are prominent, the shorter chain relaxes only by
reptation, whereas the longer chain shows more complex behavior, i.e., reptation in the original tube, short-range tube renewal
causing the tube enlargement, and thereafter reptation again in the expanded tube. Dynamic moduli data from literature are
used for determining the compositional dependence of the relaxation times. Also on the basis of the relaxation mechanism considered
here, the critical composition due to the onset of entanglements between different longer chains is proposed as a function
of their component molecular weighl ratio. 相似文献