全文获取类型
收费全文 | 12869篇 |
免费 | 1000篇 |
国内免费 | 732篇 |
专业分类
电工技术 | 206篇 |
综合类 | 966篇 |
化学工业 | 2278篇 |
金属工艺 | 793篇 |
机械仪表 | 359篇 |
建筑科学 | 610篇 |
矿业工程 | 691篇 |
能源动力 | 493篇 |
轻工业 | 707篇 |
水利工程 | 203篇 |
石油天然气 | 4377篇 |
武器工业 | 165篇 |
无线电 | 408篇 |
一般工业技术 | 867篇 |
冶金工业 | 525篇 |
原子能技术 | 114篇 |
自动化技术 | 839篇 |
出版年
2024年 | 56篇 |
2023年 | 175篇 |
2022年 | 340篇 |
2021年 | 381篇 |
2020年 | 412篇 |
2019年 | 316篇 |
2018年 | 303篇 |
2017年 | 377篇 |
2016年 | 402篇 |
2015年 | 375篇 |
2014年 | 604篇 |
2013年 | 867篇 |
2012年 | 774篇 |
2011年 | 851篇 |
2010年 | 653篇 |
2009年 | 678篇 |
2008年 | 595篇 |
2007年 | 716篇 |
2006年 | 786篇 |
2005年 | 691篇 |
2004年 | 575篇 |
2003年 | 548篇 |
2002年 | 505篇 |
2001年 | 453篇 |
2000年 | 359篇 |
1999年 | 321篇 |
1998年 | 263篇 |
1997年 | 221篇 |
1996年 | 201篇 |
1995年 | 170篇 |
1994年 | 120篇 |
1993年 | 84篇 |
1992年 | 65篇 |
1991年 | 61篇 |
1990年 | 74篇 |
1989年 | 52篇 |
1988年 | 25篇 |
1987年 | 24篇 |
1986年 | 24篇 |
1985年 | 17篇 |
1984年 | 16篇 |
1983年 | 8篇 |
1982年 | 12篇 |
1981年 | 4篇 |
1980年 | 7篇 |
1977年 | 3篇 |
1964年 | 5篇 |
1957年 | 3篇 |
1956年 | 3篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Zhong-Ni Wang Gan-Zuo Li Jian-Hai Mu Wen-Xia Zhang 《Journal of surfactants and detergents》2002,5(4):391-396
The interaction and synergism of some polyoxyethylenated fatty alcohol ether (POE) nonionic surfactants (C12E2, C12E3, C10E5, C10E7, where Cx indicates number of carbon atoms in the chain and Ey indicates number of oxyethylene glycol ethers) with trioxyethylenated dodecyl sulfonate (C12E3S) in mixed monolayer formation at the surface and in mixed micelle formation in aqueous solutions were studied at 25 and
40°C by calculating interaction parameters (βα, βM) from surface tension-concentration data by use of Rosen's equations based on the nonideal solution theory. All the systems
investigated adapt reasonably well to the nonideal model, with negative values of βσ and βM (where M means micelle and σ refers to the air-liquid interface) indicating a favorable interaction between the mixed surfactants.
Either at a monolayer or in a mixed micelle, the attractive interaction becomes stronger when the alkyl chain in the POE surfactant
is longer, i.e., when the POE becomes more hydrophobic. The interaction increases in the order C10E7<C10E5<C12E3, C12E2. For the two C10E
n
(n= 5,7)/C12E3S systems, as temperature increases from 25 to 40°C, the interaction increases in a mixed micelle, but it decreases in a mixed
monolayer. Synergism in mixed micelle formation exists for C12E3S/C10E
n
mixtures when X1
M
, the mole fraction of POE in a mixed micelle, is ≈0.4–0.8, whereas synergism does not occur in the systems of C12E3S/C12E
m
due to the large difference between CMC1 and CMC2, i.e., large |In(C
1
M
/C
2
M
)| value (where CMC=critical micelle concentration). The degree of synergism in mixed micelle formation is temperature independent
and is 0.23, 0.18, and close to zero for C10E5/C12E3S, C10E7/C12E3S, and C12E
m
(m=2,3)/C12E3S systems, respectively. Synergism in surface tension reduction effectiveness occurs in C12E3S/C12E2 and C12E3S/C12E3 systems. The mole fractions of POE in the solution phase are 0.302 and 0.333 for the two mixtures at the point of maximum
synergism. 相似文献
122.
E. A. Levashov A. S. Rogachev V. V. Kurbatkina Yu. K. Epishko N. A. Kochetov 《International Journal of Self-Propagating High-Temperature Synthesis》2007,16(4):218-224
Biocompatible composites (Ti, Ta)C
x
+ Ca3(PO4)2 for deposition of nanofilms onto load-bearing implants by ion-plasma sputtering were prepared from Ti + Ta + C + Ca3(PO4)2 mixtures by forced SHS compaction. The effect of Ta + C addition to green mixtures (characterized by parameter z) on the structure/phase formation in combustion products was explored. The addition of tantalum and carbon was found to have
little or no influence on the burning velocity U and combustion temperature T
c. Two thermal spikes exhibited by thermograms were associated with the occurrence of two consecutive reactions leading to
formation of titanium and tantalum carbides. With increasing z, the grain size of (Ti, Ta)C was found to diminish, its relative density to decrease, while the hardness to markedly grow.
相似文献
123.
Effect of natural antioxidants in virgin olive oil on oxidative stability of refined,bleached, and deodorized olive oil 总被引:1,自引:0,他引:1
M. Teresa Satue Shu-Wen Huang Edwin N. Frankel 《Journal of the American Oil Chemists' Society》1995,72(10):1131-1137
The factors influencing the oxidative stability of different commercial olive oils were evaluated. Comparisons were made of
(i) the oxidative stability of commercial olive oils with that of a refined, bleached, and deodorized (RBD) olive oil, and
(ii) the antioxidant activity of a mixture of phenolic compounds extracted from virgin olive oil with that of pure compounds
andα-tocopherol added to RBD olive oil. The progress of oxidation at 60°C was followed by measuring both the formation (peroxide
value, PV) and the decomposition (hexanal and volatiles) of hydroperoxides. The trends in antioxidant activity were different
according to whether PV or hexanal were measured. Although the virgin olive oils contained higher levels of phenolic compounds
than did the refined and RBD oils, their oxidative stability was significantly decreased by their high initial PV. Phenolic
compounds extracted from virgin olive oils increased the oxidative stability of RBD olive oil. On the basis of PV, the phenol
extract had the best antioxidant activity at 50 ppm, as gallic acid equivalents, but on the basis of hexanal formation, better
antioxidant activity was observed at 100 and 200 ppm.α-Tocopherol behaved as a prooxidant at high concentrations (>250 ppm) on the basis of PV, but was more effective than the
other antioxidants in inhibiting hexanal formation in RBD olive oil.o-Diphenols (caffeic acid) and, to a lesser extent, substitutedo-diphenols (ferulic and vanillic acids), showed better antioxidant activity than monophenols (p- ando-coumaric), based on both PV and hexanal formation. This study emphasizes the need to measure at least two oxidation parameters
to better evaluate antioxidants and the oxidative stability of olive oils. The antioxidant effectiveness of phenolic compounds
in virgin olive oils can be significantly diminished in oils if their initial PV are too high. 相似文献
124.
The isotopic exchange has been studied between catalyst radiosulfur and H2S, formed in thiophene hydrodesulfurization (HDS) (named S-displace) on alumina supported molybdena, on CoMoOx, PdMoOx, PtMoOx and on silica–alumina supported NiWOx. S-displace was compared with radiosulfur exchange data between catalyst radiosulfur and gas phase H2S (Sexc) determined previously. The extent of Sexc was higher than that of the S-displace for Mo, CoMo in and NiW, whereas the extent of S-displace from PdMoO and PtMoO was
significantly higher, than that of Sexc. Thiophene HDS product distribution data are discussed in terms of increased C=C hydrogenation and C–C hydrogenolysis activity,
explained by increasing H2S production with longer circulation time of the thiophene/H2 mixture, The C1/C3<1 ratios among C4-hydrogenolysis products indicate some coke formation. The decrease of thiophene HDS activity is presumably a consequence
of increasing site-blocking with the formation of more H2S and coke with longer duration of thiophene treatment. 相似文献
125.
Ralph Schreiber Britta ReinkeCarsten Vogt Joachim WertherGerd Brunner 《Powder Technology》2003,138(1):31-38
Various particles with sizes between 100 and 200 μm were encapsulated with waxes commonly used in technical coating applications. For this, a homogeneous mixture of molten paraffin and supercritical carbon dioxide was prepared in an autoclave and injected into the high-pressure fluidized bed through a nozzle from the bottom. Due to the different conditions in the mixing autoclave and the fluidized bed, the paraffin precipitated in the vicinity of the nozzle and adhered to the solid particles. A complete, thin, uniform, and solvent-free coating was produced. The use of two paraffins with different alkane compositions resulted in dissimilar spreads on glass beads due to their different glass transition temperatures. A smaller pressure drop across the nozzle led to more uniform and even coatings. Glass beads, ceramic spheres, potassium chloride, and lactose showed similar coating results, whereas different morphologies were observed with a plastic material, characterized by a rougher surface and a lower surface energy. The high quality of the coating was confirmed by standard dissolution tests with coated potassium chloride crystals and lactose agglomerates. 相似文献
126.
The anionic polymerization of lauryllactam was initiated at 270°C using sodium hydride as an initiator and N,N′‐ethylene‐bisstearamide (EBS) as an activator (NaH:EBS molar ratio of 2). Polymerization occurred in less than 2 min and was successfully performed in an internal mixer and a twin‐screw extruder with corotating intermeshing screws (Werner & Pfleiderer ZSK 25). The content of residual monomer, as determined by thermogravimetric analysis, was lower than 0.5 wt %. Molecular weight, as measured by size exclusion chromatography, was governed by the lauryllactam:NaH molar ratio calculated on a Mn of 25 kg/mol at a constant NaH:EBS molar ratio of 2. Blends were prepared in situ by polymerization of lauryllactam solutions of various polymers. When poly(ethylene‐co‐butylacrylate) (Lotryl®; Atofina) was dissolved in lauryllactam, rubber‐toughened polyamide 12 blends were obtained. Mechanical properties of the injection‐molded polymers were examined by stress–strain as well as notched Charpy impact tests at different temperatures. Blend morphologies were imaged by scanning electron microscopy (SEM). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 344–351, 2003 相似文献
127.
The processes occurring in aprotic electrolyte on a lithium electrode in the steady state conditions and under polarization
are studied using the method of electrochemical noise characterization. The evidence of the electro-chemical noise measurements
on polarized lithium electrodes indicates that the discharge of lithium ions under cathodic polarization, as well as lithium
anodic dissolution, is localized under the passive film rather than on its surface. An increase in the polarizing current
results in local breakdown of the film; in this case, the electrochemical process emerges on the electrode surface affecting
the character of potential fluctuations. The intensity of electrochemical noise significantly increases in the course of cathodic
polarization with high currents. The reason is that lithium metal crystals, which are formed under the passive film, perforate
the film, and dendrites grow on its surface. The method shows the dependence of electrochemical noise intensity on the nature
of the electrolyte and establishes the correlation between the stability of the lithium electrode in the course of cycling
and the intensity of fluctuations. This offers an opportunity of using the method of electrochemical noise for screening organic
electrolytes for lithium batteries. 相似文献
128.
Daan Verkoeijen Gerard A. PouwGabriël M. H. Meesters Brian Scarlett 《Chemical engineering science》2002,57(12):2287-2303
Population balance models have been used in chemical engineering since the 1960s and have evolved to become the most important tools for design and control of particulate processes. In this paper we show that the intrinsic particle parameter that determines changes in the process and should thus be included in the population balance is the particle volume. The basic population that is modeled should be the mass distribution, or the volume distribution if the density is constant. The population balance thus describes the change of the volume distribution of volume with time. Furthermore, we suggest that the “birth” and “death” terms that are often used to describe discrete events in particulate processes can almost always be replaced by a rate of change term.To design and control existing and future processes, a multi-dimensional population balance model is required. We propose a volume-based model in which the particle properties that are modeled are the volumes of solid, liquid, and air, respectively. In the most general case the model will consist of a properties vector and a distribution tensor. Depending on the complexity of the process, one or more of the properties may be omitted from the model. This is shown in three examples of increasing complexity: comminution, sintering, and granulation. 相似文献
129.
介绍了在团粒法工艺的基础上,将尿素熔融成尿液进行喷浆造粒生产复混 肥过程中存在的问题,分析产生的原因并提出改进措施,对改造效果进行了总结。 相似文献
130.
Wen‐Bin Liau Yu‐Ting Sun Ling‐Yueh Yang Lee‐Yih Wang Wen‐Yen Chiu Kuo‐Huang Hsieh Sheng‐Mao Tseng 《应用聚合物科学杂志》2006,102(6):5406-5413
The polyaniline (PANI)‐coated polystyrene (PS) latexes were synthesized, and the electrically conductive films were prepared thereafter. The weight ratio of PANI was 5%. Thermal analysis of the latices was performed using DSC and TGA. In this study, the electrically conductive films were prepared above the PS glass transition temperature (Tg). During the film formation, the effects of the annealing temperature and atmosphere (air or N2) on the film resistance were investigated. In addition, the film morphology was observed utilizing scanning electron microscopy. The film resistance decreased in the initial heating stage due to the increasing temperature and the compaction of film. Then the film resistance increased with further annealing due to the aging of PANI. Typically, the film resistance was about 6000 Ω/sq, and the conductivity was 0.3 S/cm. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5406–5413, 2006 相似文献