全文获取类型
收费全文 | 9060篇 |
免费 | 1211篇 |
国内免费 | 386篇 |
专业分类
电工技术 | 1119篇 |
技术理论 | 1篇 |
综合类 | 754篇 |
化学工业 | 1289篇 |
金属工艺 | 352篇 |
机械仪表 | 400篇 |
建筑科学 | 1029篇 |
矿业工程 | 795篇 |
能源动力 | 639篇 |
轻工业 | 1968篇 |
水利工程 | 251篇 |
石油天然气 | 269篇 |
武器工业 | 101篇 |
无线电 | 323篇 |
一般工业技术 | 430篇 |
冶金工业 | 385篇 |
原子能技术 | 42篇 |
自动化技术 | 510篇 |
出版年
2024年 | 52篇 |
2023年 | 154篇 |
2022年 | 285篇 |
2021年 | 451篇 |
2020年 | 379篇 |
2019年 | 329篇 |
2018年 | 265篇 |
2017年 | 334篇 |
2016年 | 380篇 |
2015年 | 413篇 |
2014年 | 560篇 |
2013年 | 530篇 |
2012年 | 711篇 |
2011年 | 718篇 |
2010年 | 572篇 |
2009年 | 562篇 |
2008年 | 525篇 |
2007年 | 641篇 |
2006年 | 547篇 |
2005年 | 439篇 |
2004年 | 356篇 |
2003年 | 259篇 |
2002年 | 225篇 |
2001年 | 192篇 |
2000年 | 167篇 |
1999年 | 109篇 |
1998年 | 89篇 |
1997年 | 65篇 |
1996年 | 65篇 |
1995年 | 60篇 |
1994年 | 67篇 |
1993年 | 35篇 |
1992年 | 26篇 |
1991年 | 32篇 |
1990年 | 16篇 |
1989年 | 17篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1968年 | 1篇 |
1959年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
The enzymatic degradation of poly(N‐isopropyl acrylamide) (PNIPAM) grafted to carboxymethylcellulose (CMC) copolymers with a cellulasic preparation (Trichoderma viride) was studied. The enzymatic activity of the cellulasic preparation against CMC and the grafted copolymers was determined by the Petterson–Porath method, while their reduced viscosity variation in the presence of the same preparation was also followed. It has been shown that the enzymatic degradation behavior depends on the copolymer composition and the reaction temperature. Reducing sugars analysis showed that the experimental values for the grafted copolymers were higher than the calculated ones. At 50°C, the enzymatic reaction is completed in about 20 min for the copolymers, whereas for CMC it takes more than 40 min. It can be concluded that their enzymatic degradation is facilitated by the presence of the PNIPAM grafts. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1383–1386, 2003 相似文献
84.
薛泷辉 《水动力学研究与进展(A辑)》2017,(2):228-236
该文针对感潮河段魁岐排涝二站?型复杂流道的不利冲刷问题,通过建立整体水工模型,研究城市异形排涝通道消能防冲新技术,提出导流坎、消力坎和消力墩联合消能防冲技术,探索其在宽幅水位变化、多工程交替运行及通航情况下的适应能力,并给出水力设计方法。研究表明,联合消能工对复杂工况适应良好,能有效解决异形排涝通道的消能防冲问题。 相似文献
85.
86.
Multi‐angle laser light scattering (MALLS) was used to characterize birch kraft pulps with respect to their absolute molecular mass distributions (MMDs). The pulps were dissolved in lithium chloride/N,N‐dimethylacetamide and separated by size exclusion chromatography (SEC). The weight‐average and number‐average molecular masses of the cellulose fractions of the pulps obtained from the absolute MALLS measurements were compared with the molar masses obtained by direct‐standard‐calibration relative pullulan standards. Discrepancies between the two detection methods were found, and two ways of correlating the relative pullulan molar masses to the absolute molar masses were examined. In the first method, the correlation was made over a large range of molecular masses. The second method correlated the molecular masses of the standards to the molecular masses of samples by the calculation of fictitious, cellulose‐equivalent molar masses of the standards. With the preferred second method, a more correct MMD of kraft pulp samples could, therefore, be obtained from an SEC system calibrated with narrow standards. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1170–1179, 2003 相似文献
87.
以提取于马桑皮的植物鞣剂为原料,与铝盐进行绵羊酸皮结合鞣制,优化鞣制工艺并建立基于马桑皮鞣剂的植铝结合鞣制方法,对鞣制后皮革性能及鞣制机理进行研究。结果表明,当马桑皮鞣剂用量为酸皮质量的15%、Al3(SO4)2•18H2O用量为酸皮质量的20%、渗透pH为4.0、结合pH为4.5的条件下,皮革收缩温度可达110.5 ℃。皮革表观性能良好,增厚率为82.2%,抗张强度为10.0 MPa,撕裂强度为52.5 N/mm,断裂伸长率为76.8%,优于橡椀植物鞣剂结合鞣制的皮革。鞣制后皮革胶原纤维变粗,形成紧密的网状结构。马桑皮植物鞣剂能充分渗透至皮革胶原纤维中,并与其产生氢键交联。在结合鞣制时,铝盐与皮革胶原纤维中结合的单宁类成分产生络合,使交联作用增强,从而显著提高成革的热稳定性能和机械性能。 相似文献
88.
The oxidation and reforming kinetics of methane by O2, CO2 and H2O were studied on a stepped Pt(5 5 7) single crystal from 623 to 1050 K under methane rich conditions. The rate of carbon deposition was followed by ex-situ Auger electron spectroscopy under non-oxidative conditions. The apparent activation energy for methane decomposition was significantly lower than the apparent barriers measured for both total oxidation, CO2 and H2O reforming. Total oxidation of methane to CO2 and H2O followed by combined dry and steam reforming (combined combustion-reforming) led to CO production rates which were higher than direct CO2 or H2O reforming rates. The enhanced rates are most likely due to the ability of adsorbed oxygen to prevent carbon nucleation and/or scavenge carbon enabling the reforming reaction to turnover on a larger fraction of sites. Comparable amounts of carbon were found by Auger electron spectroscopy measurements after both direct dry or steam reforming, while combined oxidation-reforming had considerable less carbon. During direct dry or steam reforming, CO2 and H2O serve only to scavenge adsorbed atomic carbon, while in the presence of oxygen, carbon is removed by both combustion and reforming routes. 相似文献
89.
Ju Kumanotani 《Progress in Organic Coatings》1997,34(1-4):135-146
The chemistry and technology of oriental lacquer, proof of long-term durability by a laboratory test, and morphological features of the closely packed shell (polysaccharides–glycoproteins)–core (polymerized urushiol) microgel particles, which are chiefly responsible for degradation due to efflorescence outdoors, are described. The dimerization mechanism of urushiol was demonstrated by separation of over 20 urushiol dimer derivatives. Physiological dimerization of urushiol in the lacquer is very much influenced by the humidity in drying, and the interaction of semiquinone radicals with metal ions, hydrophilic polysaccharides and amphipathic glycoproteins contained in the lacquer. A mechanism for renewable oriental lacquer is proposed, involving harmony of technology and nature within the lacquer tree plantations in south-east Asia. A brief review of studies of lacquer chemistry and synthetic coatings is given. 相似文献
90.
由于混凝土抗拉能力较差,双曲组合扭壳抵抗悬垂线方向的主拉应力控制至关重要.如果拆模顺序不当,可能会使壳体结构产生过大的拉应力.为解决此问题,以华工扭壳为例,对平行四边形底面双曲组合扭壳的满堂脚手架施工拆模顺序进行全面优化分析,并与工程实测进行对比,得出较为合理的拆模方式. 相似文献