全文获取类型
收费全文 | 1166篇 |
免费 | 25篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 90篇 |
综合类 | 2篇 |
化学工业 | 555篇 |
金属工艺 | 20篇 |
机械仪表 | 23篇 |
建筑科学 | 19篇 |
矿业工程 | 1篇 |
能源动力 | 27篇 |
轻工业 | 91篇 |
水利工程 | 1篇 |
石油天然气 | 2篇 |
无线电 | 41篇 |
一般工业技术 | 194篇 |
冶金工业 | 9篇 |
原子能技术 | 41篇 |
自动化技术 | 81篇 |
出版年
2023年 | 4篇 |
2022年 | 11篇 |
2021年 | 9篇 |
2020年 | 7篇 |
2019年 | 5篇 |
2018年 | 14篇 |
2017年 | 11篇 |
2016年 | 13篇 |
2015年 | 14篇 |
2014年 | 21篇 |
2013年 | 80篇 |
2012年 | 34篇 |
2011年 | 70篇 |
2010年 | 44篇 |
2009年 | 53篇 |
2008年 | 55篇 |
2007年 | 41篇 |
2006年 | 39篇 |
2005年 | 35篇 |
2004年 | 44篇 |
2003年 | 31篇 |
2002年 | 42篇 |
2001年 | 19篇 |
2000年 | 17篇 |
1999年 | 23篇 |
1998年 | 16篇 |
1997年 | 37篇 |
1996年 | 20篇 |
1995年 | 18篇 |
1994年 | 13篇 |
1993年 | 13篇 |
1992年 | 21篇 |
1991年 | 12篇 |
1990年 | 15篇 |
1989年 | 23篇 |
1988年 | 12篇 |
1987年 | 11篇 |
1986年 | 17篇 |
1985年 | 23篇 |
1984年 | 19篇 |
1983年 | 34篇 |
1982年 | 27篇 |
1981年 | 24篇 |
1980年 | 13篇 |
1979年 | 29篇 |
1978年 | 15篇 |
1977年 | 15篇 |
1976年 | 10篇 |
1975年 | 5篇 |
1973年 | 7篇 |
排序方式: 共有1197条查询结果,搜索用时 0 毫秒
41.
42.
Although the production of electro‐conductive aramid fibers is efficient, the method needs to be modified before it can be applied to aramid films. Whereas impregnation of an aramid film with a metal complex using supercritical CO2 is achievable, the relatively low adhesion strength of the metal layer applied using electroless copper plating is problematic. To solve this problem, thermal treatment was conducted before, after, or both before and after electroless plating. The rationale for using thermal treatment to improve the adhesiveness of the plated layer was based on the findings that (1) an aramid film contains a significant amount of water (about 3.5 % w.o.f.), which might have a negative impact on adhesion; and (2) because an impregnated metal complex liberates metal catalyst by thermal decomposition during impregnation, a supplementary thermal action might liberate more catalyst and thereby improve adhesion. We found that thermal treatment improved adhesion of the metal layer to the aramid film. Moreover, we discovered that with respect to electroless copper plating, a short time‐lag was crucial to obtaining a thin and homogeneous metal layer with strong adhesion. In addition, we demonstrate the affinity of an aramid film for Pd(acac)2. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
43.
1H and 13C n.m.r. chemical shifts and also spin-lattice relaxation times of phospholipids, mainly egg yolk lecithin, were measured in organic solvents, especially aromatic solvents. The use of aromatic solvents promotes the difference in the magnetic shielding environment of the internal methylene protons of the fatty acyl chains and as a result, a doublet peak for the methylene groups was observed in the solvents, especially mesitylene. The 1H and 13C n.m.r. T1 measurements indicate the remarkable gradient in the motional freedom along the fatty acyl chains as well as the marked decrease in the motional freedom of the polar head group and also, the high-field component of the doublet peak for internal methylene protons has a shorter T1 value than the low-field component. Thus, it was concluded that the low-field component in the doublet comes from the methylene protons located relatively in the neighbourhood of the carbonyl groups and the high-field component the methylene protons located relatively in the neighbourhood of the terminal methyl groups of the fatty acyl chains. 相似文献
44.
Inside Cover: Molecular Design of an Environmentally Sensitive Fluorescent Nucleoside, 3‐Deaza‐2′‐Deoxyadenosine Derivative: Distinguishing Thymine by Probing the DNA Minor Groove (ChemBioChem 11/2014) 下载免费PDF全文
45.
Iron Deposition from Aluminosilicate Containing Trace Amount of Iron Oxide by Borate‐Enhanced Hydrogen Reduction 下载免费PDF全文
Isao Tsuyumoto 《Journal of the American Ceramic Society》2015,98(12):3666-3669
Aluminosilicate containing 0.50 wt% of iron oxide as impurity yields metallic iron deposit by heating with sodium borate (3Na2O·B2O3) in H2 at 950°C, while it remains unchanged by heating without the borate under the same condition. The SEM and EDX measurements indicate that the metallic iron deposit is formed on the sodium borate glass layer. We first find that the reduction in minor constituents in oxides is enhanced by the addition of borate as a flux. 相似文献
46.
Dong-Pyo Hong Ryoichi Kuboi Isao Komasawa 《Korean Journal of Chemical Engineering》1997,14(5):334-340
Specific interfacial properties, which affect protein extraction in AOT and AOT-lecithin reverse micellar systems (RVMS),
have been studied by using their percolation processes. Solubilization of proteins or synthetic polymers into RVMS by the
injection method and its effect on the percolation processes could be easily evaluated by the measurement of electrical conductivity.
The percolation process is found to be a sensitive and convenient measure of micro-interface of RVMS solubilizing various
polymers or proteins, which clearly reflects the polymer(protein)-micellar and micellar-micellar interactions. The stability
of RVMS or micellar-micellar interaction was dependent on the kinds, concentration and molecular weight of solubilized polymers.
The value of p, defined as the variation of percolation threshold with the concentration of solubilized polymers, can be utilized
to evaluate the stability of RVMS solubilizing polymers or micellar-micellar interactions. The values of Β are affected by
the hydrophobicity, molecular weight and absolute value of the net charge of the polymers solubilized into the AOT reverse
micelles, which were evaluated by using Aqueous Two-Phase Systems (ATPS). 相似文献
47.
(Na,K)NbO3 ceramics was synthesized by an ordinal solid state reaction method. Thermally stimulated depolarization current (TSDC) pattern of the poled ceramics was measured. Electrically poled Na0.5K0.5NbO3 ceramics generated anomalous large discharge current at around 370 °C during the heating step due to the thermal relaxation of oxygen vacancy. The oxygen vacancy piled up around electrodes and formed the electrically inhomogeneous structure in the ceramics. In addition, the anomalous current of K-riched ceramics was larger than that of Na-riched one. This result suggested that the equilibrium composition of NaNbO3–KNbO3 system was near to Na-riched composition against Na0.5K0.5NbO3. 相似文献
48.
The reaction of N-(2,4-dinitrophenyl)pyridinium anion ( salt(A) ; A = Cl−, FeCl4−, and (CN)2N−) with linear polyethyleneimine (LPEI; Mn = 20 380) and branched polyethyleneimines (BPEI1; Mn = 600, BPEI2; Mn = 10 000) at various molar feed ratios without using a catalyst resulted in pyridinium ring opening to yield ionic LPEI and BPEIs that were crosslinked by conjugated penta-2,4-dienylideneammonium (PDA) units, LPEI-PDA , BPEI1-PDA , and BPEI2-PDA , respectively. A model compound was synthesized by the reaction of salt(Cl) with diethylamine. The solubilities of BPEI1-PDA and BPEI2-PDA depended on the feed ratios between salt(Cl) and BPEI1 or BPEI2. Dipping LPEI-PDA into water and methanol yielded hydro- and organogels, respectively. UV–vis and reflection measurements revealed an expanded π-conjugation length between the polymer chains due to the through-space orbital interaction of the electrons on the two nitrogen atoms at the crosslinked positions in LPEI-PDA , BPEI1-PDA , and BPEI2-PDA . Cyclic voltammetry analysis suggested that the polymers underwent electrochemical oxidation. Measurement using a superconducting quantum interference device (SQUID) indicated that LPEI-PDA having FeCl4− anions was paramagnetic. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48712. 相似文献
49.
Kimoto H Yoshimune K Matsuyma H Yumoto I 《International journal of molecular sciences》2012,13(2):1733-1746
A psychrotolerant bacterium, strain T-3 (identified as Psychrobacter piscatorii), that exhibited an extraordinarily high catalase activity was isolated from the drain pool of a plant that uses H(2)O(2) as a bleaching agent. Its cell extract exhibited a catalase activity (19,700 U·mg protein(-1)) that was higher than that of Micrococcus luteus used for industrial catalase production. Catalase was approximately 10% of the total proteins in the cell extract of the strain. The catalase (PktA) was purified homogeneously by only two purification steps, anion exchange and hydrophobic chromatographies. The purified catalase exhibited higher catalytic efficiency and higher sensitivity of activity at high temperatures than M. luteus catalase. The deduced amino acid sequence showed the highest homology with catalase of Psycrobacter cryohalolentis, a psychrotolelant bacterium obtained from Siberian permafrost. These findings suggest that the characteristics of the PktA molecule reflected the taxonomic relationship of the isolate as well as the environmental conditions (low temperatures and high concentrations of H(2)O(2)) under which the bacterium survives. Strain T-3 efficiently produces a catalase (PktA) at a higher rate than Exiguobacterium oxidotolerans, which produces a very strong activity of catalase (EktA) at a moderate rate, in order to adapt to high concentration of H(2)O(2). 相似文献
50.
Yuki Otsuka Isao Yamamoto Motoyuki Iijima Junichi Tatami 《International Journal of Applied Ceramic Technology》2023,20(2):708-717
Controlling the crystal orientation of hydroxyapatite, an inorganic material that is a major component of human hard tissues is important to fabricate better artificial bones and artificial tooth roots. To obtain highly oriented hydroxyapatite ceramics under a strong magnetic field, a good dispersion of the raw materials in the slurry must be obtained. This study investigates the effect of wet-jet milling of a slurry on the orientation of hydroxyapatite ceramics fabricated using a strong magnetic field. Although the prolonged ball milling with ZrO2 balls of the raw powder fractures the primary particles of hydroxyapatite, wet-jet milling is used to successfully pulverize agglomerated hydroxyapatite raw powder without changing the morphology of the primary particles. Evidently, ceramics with a highly oriented c-axis of hydroxyapatite are obtained by molding the wet-jet milled slurry in a strong rotating magnetic field. They exhibit anisotropy in fracture toughness, and the fracture toughness calculated from the crack length perpendicular to the rotating axis is higher than that calculated from the crack length parallel to it. Furthermore, these values are higher than those of randomly oriented hydroxyapatite ceramics, which may be owing to the crystal orientation dependence of the fracture toughness of the hydroxyapatite grains and grain boundaries. 相似文献