全文获取类型
收费全文 | 8588篇 |
免费 | 587篇 |
国内免费 | 373篇 |
专业分类
电工技术 | 240篇 |
综合类 | 460篇 |
化学工业 | 1276篇 |
金属工艺 | 320篇 |
机械仪表 | 310篇 |
建筑科学 | 643篇 |
矿业工程 | 109篇 |
能源动力 | 406篇 |
轻工业 | 712篇 |
水利工程 | 214篇 |
石油天然气 | 125篇 |
武器工业 | 37篇 |
无线电 | 1014篇 |
一般工业技术 | 1533篇 |
冶金工业 | 1138篇 |
原子能技术 | 471篇 |
自动化技术 | 540篇 |
出版年
2024年 | 22篇 |
2023年 | 147篇 |
2022年 | 171篇 |
2021年 | 250篇 |
2020年 | 219篇 |
2019年 | 227篇 |
2018年 | 214篇 |
2017年 | 270篇 |
2016年 | 285篇 |
2015年 | 262篇 |
2014年 | 369篇 |
2013年 | 699篇 |
2012年 | 427篇 |
2011年 | 629篇 |
2010年 | 476篇 |
2009年 | 451篇 |
2008年 | 431篇 |
2007年 | 512篇 |
2006年 | 485篇 |
2005年 | 351篇 |
2004年 | 359篇 |
2003年 | 277篇 |
2002年 | 297篇 |
2001年 | 220篇 |
2000年 | 168篇 |
1999年 | 152篇 |
1998年 | 207篇 |
1997年 | 131篇 |
1996年 | 120篇 |
1995年 | 83篇 |
1994年 | 78篇 |
1993年 | 61篇 |
1992年 | 48篇 |
1991年 | 54篇 |
1990年 | 55篇 |
1989年 | 49篇 |
1988年 | 32篇 |
1987年 | 23篇 |
1986年 | 20篇 |
1985年 | 37篇 |
1984年 | 24篇 |
1983年 | 21篇 |
1982年 | 16篇 |
1981年 | 7篇 |
1966年 | 7篇 |
1964年 | 22篇 |
1963年 | 11篇 |
1960年 | 9篇 |
1959年 | 7篇 |
1958年 | 6篇 |
排序方式: 共有9548条查询结果,搜索用时 0 毫秒
51.
本文阐述了充分考虑矿石性质,探索出混合浮选的分步流程,恰当的施用多元扑收剂所产出的“协同效应”,稳定和强化选别工艺,收到提高选金技术指标的效果。 相似文献
52.
Nicholas P. Petropolis Harrison M. Petropolis Nicole E. MacNeil Taylor M. Doucet D. Gerrard Marangoni 《Journal of surfactants and detergents》2021,24(1):51-66
The critical micelle concentrations (CMC) values and counterion dissociation (α values) have been determined for a number of mixed micellar systems consisting of two typical ionic surfactants and glycol ethers (glymes) as cosurfactants, namely diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. Conductance experiments were used to determine the CMC and α values of the mixed micelles as a function of glyme concentration in the aqueous mixed solvent. Favorable interactions between sodium dodecyl sulfate micelles and glyme cosurfactants were deduced from the decreases in the CMC values and the large increase in the α values of these systems as a function of increasing glyme concentration in the mixed solvents. In contrast to the anionic surfactant/glyme systems, in general, there appeared to be little favorable interactions between the surfactant and glymes when micelles of the cationic surfactant dodecyltrimethylammonium bromide were formed in water/glyme solvent systems containing an increasing amount of the glymes. The interaction of glymes with the surfactant micelles was examined closely via 13C nuclear magnetic resonance (NMR) chemical shifts for both surfactant and glyme carbons; these chemical shifts changes were interpreted in terms of the distribution and the localization of the glymes in the aggregates. Finally, partition constants, determined from two-dimensional diffusion-oriented spectroscopy (2D-DOSY) experiments, were used to calculate thermodynamic quantities of transfer of the glymes between the bulk phase and the self-assembled aggregates. All these results are interpreted in terms of the key contributions that both the glyme ethoxylated groups and alkyl endgroups make to the hydrophobic interactions. 相似文献
53.
Shishan Xue Guanfei Liu Jingjuan Lai Peng An Yang Liu Yuanpeng Wu Yu Wang Zhiyong Ye Qiao Tang Hongwei Zhou 《大分子材料与工程》2021,306(11):2100415
Self-healing hydrogels often possess poor mechanical properties which largely limits their applications in many fields. In this work, boron nitride nanosheets are introduced into a network of the poly(vinyl alcohol)/borax (PVA/borax) hydrogels to enhance the mechanical properties of the hydrogel without compromising the self-healing abilities. The obtained hydrogels exhibit excellent mechanical properties with a tensile strength of 0.410 ± 0.007 MPa, an elongation at break of 1712%, a Young's Modulus of 0.860 ± 0.023 MPa, and a toughness of 3.860 ± 0.075 MJ m−3. In addition, the self-healing efficiency of the hydrogels is higher than 90% within 10 min at room temperature. Benefiting from the excellent self-healing properties, the shapeability of the hydrogel fragments is observed using different molds. In addition, the hydrogels display rapid pH-driven shape memory effects and can recover to their original shape within 260 s. Overall, this work provides a new approach to hydrogels with integrated excellent mechanical properties, self-healing abilities, and rapid pH-driven shape memory effects. 相似文献
54.
55.
采用相互兼顾的原则,进行中小批量的铸铁车间就地技术改造,较好地解决了工人劳动强度、作业环境、铸件质量、产量与技改投入的矛盾。 相似文献
56.
四异丁氧基镍酞菁的合成及其溶剂效应 总被引:2,自引:0,他引:2
4 异丁氧基邻苯二腈与氯化镍在强有机碱 1 ,8 二氮杂双环 (5 ,4,0 )十一碳烯 7催化下反应 ,合成了四异丁氧基镍酞菁 ,产物经FT -IR、元素分析、UV -Vis吸收光谱和1 H NMR表征了结构 ;并研究了其溶剂效应 ,结果表明 :最大吸收峰波数ν与函数 f(n ,ε)存在一定的线性关系 ,线性相关系数为 0 940 2 ,而Bayliss函数项 (n2 - 1 ) /(2n2 +1 )决定了最大吸收波长 (λmax)的位移变化 ;化合物的λmax在不同溶剂中随聚集程度增加 ,发生一定程度的蓝移 相似文献
57.
Equilibrium exchange isotherms were determined for the exchange of Cu2+ with NaZSM-5 at varying Cu(Ac)2 concentrations in solutions of constant volume and zeolite weight. At low Cu2+ levels the solid scavenged all the copper ions. When copper could be detected in the equilibrated solutions, overexchange was observed. The extent of overexchange was higher at pH 6 than at pH 4. These results were analyzed in relation to catalytic activity.On leave from the Central Institute for Chemistry, Hungarian Academy of Sciences, H1525 Budapest, Hungary. 相似文献
58.
Anthony G. Dixon 《Chemical Engineering Communications》1988,71(1):217-237
The effective radial thermal conductivity and apparent heat transfer coefficient for a packed bed were experimentally determined for beds of spheres, full cylinders and hollow cylinders, for flow rates giving particle Reynolds numbers in the range 100-1000, and for tube to particle diameter ratios of 5-12. Over these ranges the radial Peclet number Per showed significant dependence on solid conductivity, gas flow rate and particle shape, while the wall Biot number Bi showed significant dependence on tube to particle diameter ratio, gas flow rate and particle shape. These dependencies were predicted well by equations incorporating the effects of these variables into individual gas and solid phase parameters, which were then combined to give the effective or lumped parameters 相似文献
59.
Paola Scarfato Elvira Avallone Pio Iannelli Vincenzo De Feo Domenico Acierno 《应用聚合物科学杂志》2007,105(6):3568-3577
In this paper we report on the preparation and characterization of polyurea‐based microencapsulated systems, containing essential oils as core materials, for potential applications in controlled‐release formulations of agrochemicals. Microcapsules were synthesized by interfacial polymerization in o/w emulsion between polyfunctional isocyanates and diamines, to investigate the effect of the monomer kind on the morphology and properties of the produced samples. The synthetic conditions that gave the best results were used to microencapsulate four essential oils, able to interfere with the seed germination and radicle elongation of some test plants. The produced samples were characterized, with the aim to analyze their morphology and to verify the effectiveness of essential oil microencapsulation. Moreover, preliminary bioassay based on seed germination and subsequent radical growth were carried out to study the effects of the microencapsulated essential oils. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
60.
This study determines the influences of siloxane flow agents’ migration on the outermost surface composition of clearcoats, before and after ethanol cleaning. This evaluation is undertaken to improve adhesion of pressure-sensitive adhesives (PSAs) on automotive paint systems. Most of the siloxane flow agents segregate from the bulk to the clearcoat outermost surface during curing. These additives can cover until 50% of the surface area but X-ray photoelectron spectroscopy (XPS) and time of flight-secondary ion mass spectrometry (ToF-SIMS) analyses indicate that they can be removed by ethanol cleaning. Composition of the cleaned clearcoats surfaces are similar as the composition of clearcoat formulated without siloxane additives: the polyester-(melamine)-polyurethane network is more detected than before cleaning. However, outermost surface analyses show that several aging weeks increase the siloxane additives segregation. This post-cleaning migration modifies the clearcoat surface composition and cancels the chemical modifications due to the ethanol cleaning. XPS analyses show that silicon concentrations after cleaning and aging are inversely proportional to the initial silicon concentrations measured after curing. It highlights that aging has to be controlled to improve adhesion of PSAs on clearcoats. A second ethanol cleaning on aged clearcoats is not effective to remove these new siloxane additives. Their formulation should be different from the flow agents and it could modify their solubility in ethanol. This result could also indicate that these new siloxane additives are not located on the last molecular layer of surface and they would not be soluble in ethanol. 相似文献