全文获取类型
收费全文 | 1133篇 |
免费 | 41篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 54篇 |
化学工业 | 357篇 |
金属工艺 | 26篇 |
机械仪表 | 23篇 |
建筑科学 | 17篇 |
能源动力 | 65篇 |
轻工业 | 94篇 |
水利工程 | 4篇 |
石油天然气 | 2篇 |
无线电 | 80篇 |
一般工业技术 | 244篇 |
冶金工业 | 98篇 |
原子能技术 | 38篇 |
自动化技术 | 75篇 |
出版年
2023年 | 11篇 |
2022年 | 38篇 |
2021年 | 37篇 |
2020年 | 18篇 |
2019年 | 29篇 |
2018年 | 33篇 |
2017年 | 29篇 |
2016年 | 36篇 |
2015年 | 21篇 |
2014年 | 50篇 |
2013年 | 84篇 |
2012年 | 75篇 |
2011年 | 67篇 |
2010年 | 64篇 |
2009年 | 61篇 |
2008年 | 67篇 |
2007年 | 48篇 |
2006年 | 41篇 |
2005年 | 36篇 |
2004年 | 30篇 |
2003年 | 36篇 |
2002年 | 21篇 |
2001年 | 19篇 |
2000年 | 20篇 |
1999年 | 10篇 |
1998年 | 24篇 |
1997年 | 14篇 |
1996年 | 17篇 |
1995年 | 11篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1984年 | 6篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 12篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1971年 | 2篇 |
排序方式: 共有1177条查询结果,搜索用时 15 毫秒
51.
Hirotaka Koga Takuya Kitaoka Mitsuyoshi Nakamura Hiroyuki Wariishi 《Journal of Materials Science》2009,44(21):5836-5841
A novel microstructured catalyst that consists of Cu/ZnO catalyst powders and ceramic fibers was successfully prepared using pulp fibers as a tentative matrix by a papermaking technique. As-prepared material, called a paper-structured catalyst, possessed porous microstructure with layered ceramic fiber networks (average pore size ca. 20 μm, porosity ca. 50%). In the process of methanol autothermal reforming (ATR) to produce hydrogen, paper-structured catalysts demonstrated both high methanol conversion and low concentration of undesirable carbon monoxide as compared with catalyst powders and pellets. The catalytic performance of paper-structured catalysts depended on the use of pulp fibers, which were added in the paper-forming process and finally removed by thermal treatment before ATR performance tests. Confocal laser scanning microscopy and mercury intrusion analysis suggested that the tentative pulp fiber matrix played a significant role in regulating the fiber-network microstructure inside paper composites. Various metallic filters with different average pore sizes, used as supports for Cu/ZnO catalysts, were subjected to ATR performance tests for elucidating the pore effects. The tests indicated that the pore sizes of catalyst support had critical effects on the catalytic efficiency: the maximum hydrogen production was achieved by metallic filters with an average pore size of 20 μm. These results suggested that the paper-specific microstructures contributed to form a suitable catalytic reaction environment, possibly by promoting efficient diffusion of heat and reactants. The paper-structured catalyst with a regular pore microstructure is expected to be a promising catalytic material to provide both practical utility and high efficiency in the catalytic gas-reforming process. 相似文献
52.
Takuya Takahashi Motoya Suzuki Ryuji Nomura Yuichi Okuda Koji Kamiya Takenori Numazawa Peter Shirron 《Microgravity science and technology》2011,23(4):365-372
Superfluid 4He was produced on a small jet plane for the first time using a small GM-refrigerator to condense the liquid and a scroll
pump to get the superfluid by evaporation. The surface wave on superfluid under 0.5g
E, 0.1g
E and 0.05g
E, together with 2g
E and 1g
E, was successfully examined by an optical method utilizing parabolic flight. Here, g
E is the gravitational constant on the ground. Assuming that only the fundamental mode was excited as determined by the sample
cell width, the resonance peak in the frequency domain was well reproduced by the gravity wave with corresponding gravity
constant. 相似文献
53.
54.
T. Kato H. Funahashi H. Nakamura M. Fujimoto T. Machida H. Sakata S. Nakao T. Hasegawa 《Journal of Superconductivity and Novel Magnetism》2010,23(5):771-773
We have performed low-temperature scanning tunneling spectroscopy on overdoped Bi2Sr2−x
La
x
CuO6+δ
(x=0.1 and 0.2) at 4.2 K. The tunneling spectra in both samples obviously exhibit two energy gaps: one has clear gap structure
with sharp gap edge peaks, and another is observed as kinks inside the larger gap. Both the energy gaps inhomogeneously vary
on the surface at nanometer scale, and their values positively correlate each other. The distributions of both gaps normalized
to the mean values are identical independent of the doping level. These results suggest that the two gaps are commonly affected
by the source of the electronic disorder. 相似文献
55.
MnO2 nanorods were synthesized by mechanochemical processing with subsequent heat treatment and their photocatalytic activity was studied on the decolourization of aqueous solution of Rhodamine B at different pH levels. A solid state redox reaction 2KMnO4 + MnCl2 → 3MnO2 + 2KCl + O2 was activated during mechanical milling. Excess KCl salt was added in the starting powder mixture to prevent agglomeration of MnO2 nanoparticles. The milling resulted in the production of amorphous MnO2 nanoparticles with a high surface area of 204 m2 g?1. Crystalline MnO2 nanorods of diameters about 15–20 nm were produced by heating the as-milled powder at 350 °C for 1 h in air. Amorphous MnO2 nanoparticles showed higher degradation rate of Rhodamine B than crystalline MnO2 nanorods under simulated sunlight. The degradation rate was higher under acidic conditions. This work demonstrates the potential for cost effective, green and scalable synthesis of MnO2 nano-catalysts for environmental applications. 相似文献
56.
In this paper, we investigate iterative learning control (ILC) for non‐minimum phase systems from a novel viewpoint. For non‐minimum phase systems, the magnitude of a desiredinput obtained by ILC using forward‐time updating and Silverman's inversion are too large because of the influence of the unstable zeros. On the other hand, stable inversion constructs a bounded desired input by using non‐causal inverse for non‐minimum phase systems. In this paper, we first clarify that ILC using an adjoint system achieves the desired input defined by stable inversion. Hence, ILC using an adjoint system is an effective method for the control of non‐minimum phase systems with uncertainty. However, a useful convergence condition of ILC using an adjoint system was not achieved. Next, we develop a simple convergence condition in the frequency domain. 相似文献
57.
Machida Y Hattori K Miyake K Kawase Y Kawase M Iijima S 《Journal of Bioscience and Bioengineering》2000,90(1):62-68
Bacteriophage 63D, previously isolated from sewage, is associated with alpha-2,8-linked polysialic acid degrading activity. We cloned a DNA fragment containing the sialidase gene from a 63D phage genomic library and the enzyme was functionally expressed in Escherichia coli. Determination of the nucleotide sequence of the fragment revealed that it contained one open reading frame (ORF) coding for a 108-kDa polypeptide consisting of 984 amino acid residues. The fragment had promoter sequences similar to the E. coli consensus promoters for sigma70. The deduced amino acid sequence of the central region of the ORF showed homology to those of phages K1F (51.6% identity) and PK1E (51.7% identity) endosialidases. Two Asp-box motifs that are widely found in sialidases were conserved. Purification of the soluble enzyme from lysed culture broth of infected E. coli yielded a 90-kDa protein upon SDS polyacrylamide gel electrophoresis, suggesting that the primary translational product is processed to the mature 90-kDa protein. The molecular mass of the enzyme was determined as 360 kDa by gel filtration, indicating that the native enzyme was probably a tetramer of identical 90-kDa subunits. 相似文献
58.
Kenji Goto Takuya Kawashima Nobuo Tanabe 《Solar Energy Materials & Solar Cells》2006,90(18-19):3251-3260
We developed new heat-resisting transparent conductive oxide (TCO) films with resistivity of 1.4×10−4 Ω cm, an optical transmittance of above 80% (at 550 nm) and heat-resisting temperature at above 600 °C. The TCO films consists of fluorine-doped tin oxide films coated on indium–tin oxide films. They were prepared by a spray pyrolysis deposition method on glass substrates. The 100×100 mm2 dye-sensitized solar cells (DSCs) were prepared with the TCO films. An energy conversion efficiency of the DSC was improved drastically in comparison to the case with conventional TCO films. 相似文献
59.
Film-type electrodes of hydrogen absorbing intermetallic compound and alloys, LaNi5, Ni0.11 Ti0.89, Ni0.50 Ti0.50 and Ni0.76 Ti0.24 were prepared by a flash evaporation method. The hydrogen electrode reaction characteristics of the LaNi5 and NiTi alloy films in 1 M NaOH are very similar to each other. The reaction proceeds via the Volmer-Tafel reaction route with mixed rate-determining characteristics. The exchange current densities of the constituent steps, as well as the overall reaction, are in the range of 10?6 A cm?2 (true). Surface analysis by an XPS technique has shown that La or Ti on the electrode surface exists as an electrocatalytically innert oxide of La2O3 or TiO2. Close similarities of these electrodes with pure Ni electrodes indicate that Ni is responsible for the electrocatalytic activity. No synergistic effect is thus noticeable. 相似文献
60.
AC Lidral PA Romitti AM Basart T Doetschman NJ Leysens S Daack-Hirsch EV Semina LR Johnson J Machida A Burds TJ Parnell JL Rubenstein JC Murray 《Canadian Metallurgical Quarterly》1998,63(2):557-568
Nonsyndromic cleft lip with or without cleft palate (CL/P) and nonsyndromic cleft palate only (CPO) are common congenital anomalies with significant medical, psychological, social, and economic ramifications. Both CL/P and CPO are examples of complex genetic traits. There exists sufficient evidence to hypothesize that disease loci for CL/P and CPO can be identified by a candidate-gene linkage-disequilibrium (LD) strategy. Candidate genes for clefting, including TGFA, BCL3, DLX2, MSX1, and TGFB3, were screened for LD with either CL/P or CPO in a predominantly Caucasian population, with both case-control- and nuclear-family-based approaches. Previously reported LD for TGFA with both CL/P and CPO could not be confirmed, except in CL/P patients with a positive family history. Also, in contrast to previous studies, no LD was found between BCL3 and either CL/P or CPO. Significant LD was found between CL/P and both MSX1 and TGFB3 and between CPO and MSX1, suggesting that these genes are involved in the pathogenesis of clefting. In addition, a mutation search in the genes DLX2, MSX1, and TGFB3 was performed in 69 CPO patients and in a subset of the CL/P patients. No common mutations were found in the coding regions of these genes; however, several rare variants of MSX1 and TGFB3 were found that may alter the latters' normal function. These results form the basis for future research, including (a) mutation searches in the MSX1 and TGFB3 genes in Caucasian CL/P patients and (b) extension of the search for MSX1 mutations in CPO patients to the noncoding regions. 相似文献