全文获取类型
收费全文 | 16131篇 |
免费 | 1848篇 |
国内免费 | 838篇 |
专业分类
电工技术 | 130篇 |
综合类 | 884篇 |
化学工业 | 9629篇 |
金属工艺 | 1248篇 |
机械仪表 | 120篇 |
建筑科学 | 278篇 |
矿业工程 | 324篇 |
能源动力 | 807篇 |
轻工业 | 1856篇 |
水利工程 | 41篇 |
石油天然气 | 749篇 |
武器工业 | 109篇 |
无线电 | 204篇 |
一般工业技术 | 1355篇 |
冶金工业 | 679篇 |
原子能技术 | 283篇 |
自动化技术 | 121篇 |
出版年
2024年 | 46篇 |
2023年 | 237篇 |
2022年 | 376篇 |
2021年 | 479篇 |
2020年 | 469篇 |
2019年 | 483篇 |
2018年 | 487篇 |
2017年 | 580篇 |
2016年 | 601篇 |
2015年 | 561篇 |
2014年 | 788篇 |
2013年 | 1667篇 |
2012年 | 1056篇 |
2011年 | 1014篇 |
2010年 | 791篇 |
2009年 | 851篇 |
2008年 | 732篇 |
2007年 | 949篇 |
2006年 | 888篇 |
2005年 | 672篇 |
2004年 | 671篇 |
2003年 | 610篇 |
2002年 | 507篇 |
2001年 | 437篇 |
2000年 | 381篇 |
1999年 | 311篇 |
1998年 | 262篇 |
1997年 | 258篇 |
1996年 | 222篇 |
1995年 | 171篇 |
1994年 | 204篇 |
1993年 | 155篇 |
1992年 | 154篇 |
1991年 | 149篇 |
1990年 | 108篇 |
1989年 | 81篇 |
1988年 | 52篇 |
1987年 | 50篇 |
1986年 | 36篇 |
1985年 | 63篇 |
1984年 | 55篇 |
1983年 | 35篇 |
1982年 | 44篇 |
1981年 | 12篇 |
1980年 | 11篇 |
1979年 | 12篇 |
1978年 | 7篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1951年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 531 毫秒
51.
Gülü Insel Derin Orhon Peter A Vanrolleghem 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2003,78(4):437-445
Hydrolysis mechanism plays a dominant role in the delicate balance of electron donor/electron acceptor ratios in BNR and EBPR systems as an important carbon source. In this study, the surface‐saturation‐type hydrolysis kinetics was investigated based on respirometric measurements, within the context of the theoretical and the practical identifiability of mathematical models. The identifiable parameters of a selected model were derived from respirograms. In addition, the information from the experiments was evaluated on the basis of Optimal Experimental Design (OED) methodology for different initial conditions of the batch respirometric experiment. © 2003 Society of Chemical Industry 相似文献
52.
环己酮肟液相重排反应机理及动力学研究 总被引:6,自引:0,他引:6
研究了环己酮肟重排反应生成己内酰胺的机理及反应动力学方程。在建立用分光光度法测定环己酮肟浓度方法的基础上,实验研究了反应温度为20~45℃范围内的液相重排反应动力学。提出了此反应的化学反应动力学速率方程式: -r肟= k0exp (-E/RT)Ca肟Cb硫酸,其中环己酮肟反应级数a为2,硫酸反应级数b为1,活化能为-E/R = -19.86 kJmol-1, 频率因子k0为1.35×1027。通过实验研究证实了作为催化剂的硫酸参与重排反应的机理,认为重排反应过程中游离SO3不参与反应,仅作为水的吸收剂,此结论对环己酮肟液相重排反应的生产技术改造提供了有力依据,并在生产中得到了应用。 相似文献
53.
This article theoretically investigates the drying of uncoated paper with gas-fired infrared (IR) emitters installed within the drying section of a given commercial paper machine. Specifically, it presents the ideal location of two opposing IR emitters within the drying section. The ideal location of the two opposing IR emitters corresponds to the highest machine speed with specified average moisture content of paper sheet at the end of the drying section. This article also presents the average evaporation rate, temperature, and moisture content of the paper sheet as it travels through the drying section with the two opposing IR emitters operating at the optimum location. In addition, the temperature and moisture profiles in the sheet thickness direction, before and after the IR emitters, are provided. This article is not concerned with the potential effects of drying with IR emitters on paper sheet properties and machine runnability issues. 相似文献
54.
Acid Green 25, which is a diazoic dye bearing two sulfonic groups, is efficiently sorbed on chitosan. The protonation of chitosan may explain the electrostatic attraction of this anionic dye and that its optimum pH is close to 3. Preliminary protonation of amine groups (obtained by contact with a sulfuric acid solution) reduced the variation of solution pH following sorbent addition but significantly reduced sorption performance: the maximum sorption capacity of raw chitosan, 525 mg dye/g (0.84 mmol dye/g), was halved by acidic preconditioning. The acidic conditioning also reduced the kinetic rate—the time necessary to reach equilibrium increased up to threefold depending on the experimental conditions. The size of sorbent particles influenced sorption kinetics and equilibrium because of resistance to intraparticle diffusion, but the sorption appeared to occur not only at the surface of the sorbent but also in the intraparticle network of the polymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1073–1080, 2003 相似文献
55.
56.
Theoretical predictions using a modified radical species ternary diagram for C–H–O system indicate that addition of sulfur expands the C–H–O gas phase compositional window for diamond deposition. Sulfur addition to no-growth domain increases the carbon super-saturation by binding the oxygen and the addition of sulfur to the non-diamond domain reduces the heavy carbon super-saturation by decreasing CnHm species concentration in the gas phase. The overall effect of sulfur addition to gas phase mixtures is characterized as that of oxygen addition to the C–H system, i.e. expansion of the compositional window over which diamond can be deposited from the gas phase. In addition, the increasing sulfur concentration to diamond domain feed gases beyond 2000 ppm did not affect the steady state gas phase composition but the quality of diamond was reduced. 相似文献
57.
双环戊二烯聚合反应热力学和动力学研究 总被引:1,自引:1,他引:0
研究了DCPD-WOCl4-AlEt3体系前阶段的反应动力学,采用GC法分析了不同反应条件下的动力学数据,发现lg([DCPD]0/[DCPD]) ̄t存在线性关系,说明该体系在前段的聚合反应为一链式反应符合二级反应模型。同时还对该体系聚合反应热力学也进行了研究;对聚合反应的ΔHp、ΔSp、ΔGp进行了讨论。 相似文献
58.
In the last rice harvest season, experimental results have been obtained on the efficiency and drying quality of a solar assisted heat pump drying prototype system. The system has been operated as a solar and heat pump system and drying curves for the different options have been obtained. The advantage of the low temperature and better control in the drier shows that the heat pump assisted solar drying system is an excellent alternative to traditional drying systems. 相似文献
59.
高分子材料辐射接枝苯乙烯的研究进展 总被引:6,自引:0,他引:6
对各高分子材料辐射接枝苯乙烯的动力学,接枝方法及接枝材料的应用进行了综述,讨论限辐射剂量,剂量率,温度,后效应,溶剂,添加剂和高分子材料厚度及结晶性等方面对接枝反应的影响。 相似文献
60.
This paper deals with the non-steady-state kinetics of direct thermal initiated polymerization. The initiation is assumed to be a bimolecular reaction of the monomer. The relationship between the radical concentration and the monomer conversion is rigorously derived. In further treatment a few very close approximations are introduced based on the fact that the number of monomer molecules reacting in the initiation step is much less than that consumed in the propagation step for a process producing high polymer, and the value of the rate constant for propagation or chain transfer is much lower than that for chain termination. Expressions for various molecular parameters, such as molecular weight distribution, number-average and weight-average degrees of polymerization, and dispersity, are given. Several numerical examples are provided. 相似文献