全文获取类型
收费全文 | 8045篇 |
免费 | 814篇 |
国内免费 | 353篇 |
专业分类
电工技术 | 559篇 |
综合类 | 362篇 |
化学工业 | 1390篇 |
金属工艺 | 386篇 |
机械仪表 | 386篇 |
建筑科学 | 441篇 |
矿业工程 | 173篇 |
能源动力 | 267篇 |
轻工业 | 601篇 |
水利工程 | 102篇 |
石油天然气 | 171篇 |
武器工业 | 74篇 |
无线电 | 1127篇 |
一般工业技术 | 1162篇 |
冶金工业 | 570篇 |
原子能技术 | 70篇 |
自动化技术 | 1371篇 |
出版年
2024年 | 47篇 |
2023年 | 138篇 |
2022年 | 271篇 |
2021年 | 431篇 |
2020年 | 290篇 |
2019年 | 227篇 |
2018年 | 304篇 |
2017年 | 297篇 |
2016年 | 271篇 |
2015年 | 328篇 |
2014年 | 395篇 |
2013年 | 558篇 |
2012年 | 507篇 |
2011年 | 505篇 |
2010年 | 486篇 |
2009年 | 447篇 |
2008年 | 470篇 |
2007年 | 420篇 |
2006年 | 325篇 |
2005年 | 322篇 |
2004年 | 229篇 |
2003年 | 231篇 |
2002年 | 182篇 |
2001年 | 152篇 |
2000年 | 148篇 |
1999年 | 119篇 |
1998年 | 142篇 |
1997年 | 104篇 |
1996年 | 81篇 |
1995年 | 87篇 |
1994年 | 58篇 |
1993年 | 62篇 |
1992年 | 46篇 |
1991年 | 58篇 |
1990年 | 58篇 |
1989年 | 50篇 |
1988年 | 39篇 |
1987年 | 35篇 |
1986年 | 28篇 |
1985年 | 36篇 |
1984年 | 24篇 |
1983年 | 15篇 |
1982年 | 26篇 |
1981年 | 24篇 |
1980年 | 12篇 |
1979年 | 18篇 |
1978年 | 11篇 |
1977年 | 16篇 |
1976年 | 16篇 |
1975年 | 11篇 |
排序方式: 共有9212条查询结果,搜索用时 15 毫秒
11.
SF Zakharov SH Kwok H Sokoloff HT Chang SP Radko A Chrambach 《Canadian Metallurgical Quarterly》1998,19(10):1625-1630
An automated gel electrophoresis apparatus, recently available commercially, allows one to follow the band during electrophoresis in real time, and lends itself therefore to an evaluation of bandwidth as a function of migration time (the dispersion coefficient), resolution and band shape. These determinations assume the constancy of band area with migration time and at various gel concentrations. The purpose of the present study was to verify these assumptions. Representative proteins and sodium dodecyl sulfate (SDS)-proteins, either natively fluorescent or fluorescein carboxylate labeled, were found to exhibit band areas which approach constancy as a function of migration time in both agarose and polyacrylamide gel electrophoresis, provided that (i) the protein concentration under the band was low enough to obviate self-quenching of fluorescence; (ii) the separation of the protein of interest from contaminants had progressed sufficiently during the time at which band areas were measured; (iii) the baseline under the peak was sufficiently well defined. However, band areas decrease with increasing gel concentration. Protein peaks exhibited leading and trailing tails. The ratio of the combined tail area to total area appeared to be near-constant at varying migration times. However, that ratio increases with increasing gel concentration. The tail area does not appear to be an artifact of fluorometric detection since it is reproduced upon fluorimetric analysis of the protein eluted from gel slices after electrophoresis. However, it may be due to photochemical destruction under the conditions of repetitive fluorometric peak detection. 相似文献
12.
G.D. Wignall R.W. Hendricks W.C. Koehler J.S. Lin M.P. Wai E.L. Thomas R.S. Stein 《Polymer》1981,22(7):886-889
A series of small angle neutron scattering measurements on blends of normal polystyrene (PSH) and labelled (deuterated) polystyrene (PSD) have been made with concentrations of PSD from 5 to 50 mol %. It is shown that the single chain form factor of the polymer in bulk can be obtained from a single concentration measurement for any concentration of labelled molecules, providing the molecular weights of the parent and labelled molecules are the same and the molecular weight distributions are narrow. 相似文献
13.
By using mathematical formulae developed in previous studies, certain pollution parameters of dye effluent obtained from reactive dyeing with a single dye can be predicted with good accuracy. In this study, the degree of pollution of reactive dyeing effluent using dye mixtures was also predicted by other approaches, such as linear and non-linear regression. The prediction accuracy was found to be satisfactory. 相似文献
14.
15.
2008年29届奥运会在北京举行,使得有关奥运的话题成为热门中的热门,与运动有关或无关的众多品牌、厂商对北京奥运年均寄予厚望,为赢取更大的收获和提升品牌知名度作最大的努力。其实早在几年前,国内外运动鞋品牌企业就已经大张旗鼓,在产品研发与广告宣传等多方面投入重金,为在这次北京奥运年带来的难得契机中处于市场制高点或明或隐地博杀着。 相似文献
16.
Meng Wai Woo 《Drying Technology》2008,26(1):15-26
Current methods in alleviating the wall deposition problem in spray drying emphasize mainly controlling the stickiness of the drying particles and less attention is placed on the properties of the dryer wall. In this experimental study, the effect of wall surface properties on the deposition mechanism has been investigated. Properties considered in classifying different wall materials were surface energy, roughness, and dielectric properties. The model solution contained sucrose, representing low-molecular-weight sugars commonly encountered in spray drying of fruit and vegetable juices. The effect of wall properties on deposition was explored at different drying rates producing particles of different surface rigidity. Larger surface roughness produced higher deposition fluxes for particles with high impact velocity and moisture. Surface energy and surface roughness were found to have no significant effect for dry rigid particles at the middle and bottom elevation of the drying chamber. However, material with lower surface energy (Teflon) exhibited less deposition for rubbery particles at such elevations. Analysis shows that dielectric wall material (Teflon) tends to enhance deposition of dry particles because of attrition at the surface. Higher wall temperature was found to produce slightly more deposition. The results of this work give a general indication of the effect of wall material on the deposition problem and provide the fundamental understanding for further studies along this line. Proper selection of dryer wall material will provide potential alternatives for reducing the deposition problem. 相似文献
17.
18.
This paper presents a hyperstability theorem for a class of hybrid dynamic systems composed of coupled differential and difference equations subject to (possibly) time-varying nonlinearities satisfying a Popov-type inequality. The nonlinear controller generates the plant input at all times from its sampled values by defining an extended discrete system. The hyperstability results are obtained from this discrete system of special type whose state consists of the sampled continuous substate and the digital substate of the given hybrid system. Some corollaries and related physical interpretations are also given 相似文献
19.
The synthetic substrate anthraniloyl-beta-glycerol-P binds to myoinositol monophosphatase with a Kd = 5 microM at pH 7.5. The anthraniloyl chromophore, excited at 330 nm, sensitizes the long lived luminescence of bound Tb(III) at 490, 545, 585 and 620 nm. Assuming a mechanism of radiationless energy transfer, the actual distance of separation between the donor-acceptor pair was calculated to be R = 10 A. Tb(III) binds to the monophosphatase with a Kd = 2 microM, whereas Ca-(II) displaces the lanthanide at concentrations above 0.1 mM. The binding studies support the notion that Tb(III), Ca(II) and Mg(II) interact with a common binding site on the protein. Phosphate ion, a strong competitive inhibitor, perturbs the luminescence of bound Tb(III), whereas the substrate beta-glycero-P has no effect on the luminescence yield and long-lived emission of bound Tb(III). It is suggested that the phosphate group of the substrate is not in direct contact with the metal ion coordinated to several amino acid residues of the enzyme. 相似文献
20.
An analytic theory is presented which demonstrates that the noise induced Gordon-Haus timing jitter in arbitrary dispersion-managed transmission systems is reduced by the power-enhancement factor required to support a dispersion-managed solitons provided the path-average soliton period is much greater than the dispersion-map period. The analysis further predicts the behaviour of the amplitude, width, and quadratic chirp fluctuations due to the amplified spontaneous emission (ASE) noise 相似文献