全文获取类型
收费全文 | 297569篇 |
免费 | 6971篇 |
国内免费 | 3258篇 |
专业分类
电工技术 | 7227篇 |
技术理论 | 7篇 |
综合类 | 3391篇 |
化学工业 | 48320篇 |
金属工艺 | 13054篇 |
机械仪表 | 9965篇 |
建筑科学 | 9494篇 |
矿业工程 | 2574篇 |
能源动力 | 6442篇 |
轻工业 | 28019篇 |
水利工程 | 3401篇 |
石油天然气 | 8577篇 |
武器工业 | 444篇 |
无线电 | 32216篇 |
一般工业技术 | 53698篇 |
冶金工业 | 49200篇 |
原子能技术 | 6004篇 |
自动化技术 | 25765篇 |
出版年
2022年 | 2394篇 |
2021年 | 3862篇 |
2020年 | 2704篇 |
2019年 | 2989篇 |
2018年 | 4325篇 |
2017年 | 4489篇 |
2016年 | 4702篇 |
2015年 | 4123篇 |
2014年 | 6266篇 |
2013年 | 13497篇 |
2012年 | 9788篇 |
2011年 | 12576篇 |
2010年 | 10265篇 |
2009年 | 10660篇 |
2008年 | 11428篇 |
2007年 | 11536篇 |
2006年 | 10423篇 |
2005年 | 9113篇 |
2004年 | 7818篇 |
2003年 | 7207篇 |
2002年 | 7186篇 |
2001年 | 7147篇 |
2000年 | 6776篇 |
1999年 | 6948篇 |
1998年 | 13773篇 |
1997年 | 10333篇 |
1996年 | 8083篇 |
1995年 | 6136篇 |
1994年 | 5618篇 |
1993年 | 5318篇 |
1992年 | 4272篇 |
1991年 | 4002篇 |
1990年 | 4011篇 |
1989年 | 3935篇 |
1988年 | 3659篇 |
1987年 | 3119篇 |
1986年 | 3124篇 |
1985年 | 3465篇 |
1984年 | 3373篇 |
1983年 | 3103篇 |
1982年 | 2735篇 |
1981年 | 2925篇 |
1980年 | 2659篇 |
1979年 | 2848篇 |
1978年 | 2738篇 |
1977年 | 2848篇 |
1976年 | 3698篇 |
1975年 | 2459篇 |
1974年 | 2294篇 |
1973年 | 2325篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
Sol–gel films are actively investigated during the last decade as possible candidates for environmentally friendly pre-treatments. However, the important drawback in this case is the lack of active corrosion protection and self-healing ability. 相似文献
53.
I. Revilla & M. L. González-San José 《International Journal of Food Science & Technology》2003,38(1):29-36
Summary The effect of the addition of four commercial pectolytic preparations on the visual characteristics (colour and turbidity) of red wines has been evaluated. The effect of both clarifying and colour extracting enzymes and the effect of different doses used, were evaluated and compared. All the red wines treated enzymatically, independent of the type of enzyme and dose, present chromatic characteristics which can be considered better than those of the control wines. Also, those wines treated with enzymes had greater stability during 2 years storage in bottles, in particular the turbidity was better than untreated wines. 相似文献
54.
A novel series of temperature‐sensitive poly[(N‐isopropylacrylamide)‐co‐(ethyl methacrylate)] (p(NIPAM‐co‐EMA)) microgels was prepared by the surfactant‐free radical polymerization of N‐isopropylacrylamide (NIPAM) with ethyl methacrylate (EMA). The shape, size dispersity and volume‐phase transition behavior of the microgels were investigated by transmission electron microscopy (TEM), ultraviolet–visible (UV–Vis) spectroscopy, dynamic light scattering (DLS) and differential scanning calorimetry (DSC). The transmission electron micrographs and DLS results showed that microgels with narrow distributions were prepared. It was shown from UV–Vis, DLS and DSC measurements that the volume‐phase transition temperature (VPTT) of the p(NIPAM‐co‐EMA) microgels decreased with increasing incorporation of EMA, but the temperature‐sensitivity was impaired when more EMA was incorporated, causing the volume‐phase transition of the microgels to become more continuous. It is noteworthy that incorporation of moderate amounts of EMA could not only lower the VPTT but also enhance the temperature‐sensitivity of the microgels. The reason for this phenomenon could be attributed to changes in the complicated interactions between the various molecules. Copyright © 2004 Society of Chemical Industry 相似文献
55.
56.
The benefits of adhesively bonded structures are well known. However, the most significant factor limiting the extensive application of metal bonding in primary aerospace structures is the prevailing lack of confidence in its long term durability under hostile environmental conditions.1,2 相似文献
57.
The graft copolymerization of methyl methacrylate onto natural rubber (NR) was carried out varying the concentration of monomer, initiator, thiourea, and silver nitrate over a wide range. The grafting reaction was temperature-dependent. From the Arrhenius plot, the overall energy of activation was computed. A suitable reaction scheme and rate expression for the rate of polymerization was suggested. 相似文献
58.
J. T. DICKINSON L. C. JENSEN W. DAVID WILLIAMS 《Journal of the American Ceramic Society》1985,68(5):235-240
We present measurements of the electron, positive ion, and photon emission accompanying the fracture in vacuum of poly-crystalline 95/5 lead zirconate-titanate. The intensities of the charged-particle components of this fractoemission are shown to depend strongly on the direction (relative to the direction of fracture) and magnitude of polarization. The most intense emission is observed when the fracture surfaces are perpendicular to the polarization direction. The emission intensity increases monotonically with polarization. These results are interpreted in terms of a model involving charge separation on the fracture surfaces leading to a microdischarge during fracture. Implications to the interpretation of triboluminesence effects are discussed. 相似文献
59.
A. J. Hugo D. M. Jakelski G. Stanitsas G. R. Sullivan R. R. Hudgins P. L. Silveston 《加拿大化工杂志》1986,64(2):349-351
In the approach to a cycle-invariant state in the forced feed concentration cycling of the CO oxidation over a NiO catalyst, a very long transient has been observed lasting 80 ks or more. This transient appears to be associated only with CO pretreatment of the catalyst and is not a general phenomenon. The slow convergence to the cycle-invariant state reported in certain modelling calculations in the literature appears to have a different cause. 相似文献
60.
The comfort diagrams and the so-called PMV-PPD values are already used today directly and indirectly in a wide field in technical practice, even at a standard level. This theory is known also in Hungary, and the PMV-PPD values have been used by us for the solution of a design problem. The task was to elaborate a calculation method, an index number suitable for the determination of the thermal confort effect in the case of occasional underheating of residential and communal buildings in winter.The results of this work are presented in this paper. 相似文献