全文获取类型
收费全文 | 2396篇 |
免费 | 40篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 108篇 |
综合类 | 3篇 |
化学工业 | 458篇 |
金属工艺 | 98篇 |
机械仪表 | 32篇 |
建筑科学 | 38篇 |
能源动力 | 71篇 |
轻工业 | 130篇 |
水利工程 | 3篇 |
石油天然气 | 2篇 |
无线电 | 215篇 |
一般工业技术 | 339篇 |
冶金工业 | 681篇 |
原子能技术 | 73篇 |
自动化技术 | 196篇 |
出版年
2022年 | 21篇 |
2021年 | 29篇 |
2020年 | 22篇 |
2019年 | 18篇 |
2018年 | 26篇 |
2017年 | 25篇 |
2016年 | 43篇 |
2015年 | 22篇 |
2014年 | 42篇 |
2013年 | 71篇 |
2012年 | 88篇 |
2011年 | 95篇 |
2010年 | 64篇 |
2009年 | 78篇 |
2008年 | 88篇 |
2007年 | 80篇 |
2006年 | 80篇 |
2005年 | 74篇 |
2004年 | 70篇 |
2003年 | 69篇 |
2002年 | 51篇 |
2001年 | 51篇 |
2000年 | 42篇 |
1999年 | 58篇 |
1998年 | 283篇 |
1997年 | 148篇 |
1996年 | 92篇 |
1995年 | 62篇 |
1994年 | 68篇 |
1993年 | 72篇 |
1992年 | 51篇 |
1991年 | 29篇 |
1990年 | 27篇 |
1989年 | 29篇 |
1988年 | 21篇 |
1987年 | 27篇 |
1986年 | 16篇 |
1985年 | 26篇 |
1984年 | 17篇 |
1983年 | 15篇 |
1982年 | 26篇 |
1981年 | 25篇 |
1980年 | 9篇 |
1979年 | 13篇 |
1978年 | 11篇 |
1977年 | 13篇 |
1976年 | 29篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1972年 | 3篇 |
排序方式: 共有2447条查询结果,搜索用时 15 毫秒
121.
Akiko?Kawashima Toshihiro?NagaoEmail author Yomi?Watanabe Takashi?Kobayashi Ikuo?Ikeda Yoshio?Tominaga Yuji?Shimada 《Journal of the American Oil Chemists' Society》2004,81(11):1013-1020
TAG (MLM) with medium-chain FA (MCFA) at the 1,3-positions and long-chain FA (LCFA) at the 2-position, and TAG (LMM) with
LCFA at the 1(3)-position and MCFA at 2,3(1)-positions are a pair of TAG regioisomers. Large-scale preparation of the two
TAG regioisomers was attempted. A commercially available FFA mixture (FFA-CLA) containing 9-cis, 11-trans (9c, 11t)- and 10t,12c-CLA was selected as LCFA, and caprylic acid (C8FA) was selected as MCFA. The MLM isomer was synthesized by acidolysis of acyglycerols (AG) containing two CLA isomers with
C8FA: A mixture of AG-CLA/C8 FA (1∶10, mol/mol) and 4 wt% immobilized Rhizomucor miehei lipase was agitated at 30°C for 72 h. The ratio of MLM to total AG was 51.1 wt%. Meanwhile, LMM isomer was synthesized by
acidolysis of tricaprylin with FFA-CLA: A mixture of tricaprylin/FFA-CLA (1∶2, mol/mol) and 4 wt% immobilized R. miehei lipase was agitated at 30°C for 24 h. The ratio of LMM to total AG was 51.8 wt%. MLM and LMM were purified from 1,968 and
813 g reaction mixtures by stepwise short-path distillation, respectively. Consequently, MLM was purified to 92.3% with 49.1%
recovery, and LMM was purified to 93.2% with 52.3% recovery. Regiospecific analyses of MLM and LMM indicated that the 2-positions
of MLM and LMM were 95.1 mol% LCFA and 98.3 mol% C8 FA, respectively. The results showed that a process comprising lipase reaction and short-path distillation is effective for
large-scale preparation of high-purity regiospecific TAG isomers. 相似文献
122.
Quantification of anaerobic ammonium-oxidizing bacteria in enrichment cultures by real-time PCR 总被引:7,自引:0,他引:7
The anaerobic ammonium-oxidizing (ANAMMOX) bacteria were enriched from a rotating disk reactor (RDR) biofilm in semi-batch cultures. Based on fluorescence in situ hybridization (FISH) analysis, this enrichment led to a relative population size of 36% ANAMMOX bacteria. Phylogenetic analysis revealed that all the detected clones were related to the previously reported ANAMMOX bacteria, Candidatus Brocadia anammoxidans (AF375994), with 92% sequence similarity. Furthermore, we successfully developed a real-time polymerase chain reaction (PCR) assay to quantify populations of ANAMMOX bacteria in the enrichment cultures. For this real-time PCR assay, PCR primer sets targeting 16S ribosomal RNA genes of ANAMMOX bacteria were designed and used. The quantification range of this assay was 6 orders of magnitude, from 8.9x10(1) to 8.9x10(6) copies per PCR, corresponding to the detection limit of 3.6x10(3) target copies mL(-1). A significant correlation was found between the increase in copy numbers of 16S rRNA gene of ANAMMOX bacteria and the increase in nitrogen removal rates in the enrichment cultures. Quantifying ANAMMOX bacterial populations in the enrichment culture made it possible to estimate the doubling time of the enriched ANAMMOX bacteria to be 3.6 to 5.4 days. The real-time PCR assay gave comparable population sizes in the enrichment cultures with the FISH results. These results suggest that the real-time PCR assay developed in this study is useful and reliable for quantifying the populations of ANAMMOX bacteria in environmental and engineering samples. 相似文献
123.
Melt pool behaviour and the characteristics of the surrounding metal powder during selective laser melting (SLM) are captured using high-speed imaging, and the influence of the substrate temperature and the line building sequence on the formation of the built structure and the generation of spatter particles is experimentally investigated. The results indicate that the substrate temperature has a measurable effect on the formation of droplets and the generation of spatter particles, while the volume specific energy density of the process was the principal factor affecting the built structure. 相似文献
124.
Takeyuki Gotoh Fuyuki Abe Takenori Ishizu Masaki Yoshio 《Journal of power sources》1996,60(2):193-196
A study of the pyrolysis of an aqueous solution of manganese nitrate in the presence of silver compounds has been carried out. Thermal analysis showed that the MnO2 formation temperature and the transformation temperature from MnO2 to Mn2O3 shifted towards a lower temperature in the presence of silver acetate. A large particle-size and high crystallinity MnO2 was formed; this may be a useful method of making an excellent tantalum capacitor with high capacitance. 相似文献
125.
Kiyomi Ohmori Asuka Kamei Yuki Watanabe Keiko Abe 《International journal of molecular sciences》2022,23(6)
The Bhas 42 cell transformation assay (Bhas 42 CTA) is the first Organization for Economic Cooperation and Development (OECD)-certificated method used as a specific tool for the detection of the cell-transformation potential of tumor-promoting compounds, including non-genotoxic carcinogens (NGTxCs), as separate from genotoxic carcinogens. This assay offers the great advantage of enabling the phenotypic detection of oncotransformation. A key benefit of using the Bhas 42 CTA in the study of the cell-transformation mechanisms of tumor-promoting compounds, including non-genotoxic carcinogens, is that the cell-transformation potential of the chemical can be detected directly without treatment with a tumor-initiating compound since Bhas 42 cell line was established by transfecting the v-Ha-ras gene into a mouse fibroblast cloned cell line. Here, we analyzed the gene expression over time, using DNA microarrays, in Bhas 42 cells treated with the tumor-promoting compound 12-O-tetradecanoylphorbol-13-acetate (TPA), and NGTxC, with a total of three repeat experiments. This is the first paper to report on gene expression over time during the process of cell transformation with only a tumor-promoting compound. Pathways that were activated or inactivated during the process of cell transformation in the Bhas 42 cells treated with TPA were related not only directly to RAS but also to various pathways in the hallmarks of cancer. 相似文献
126.
Ziqing Zhai Yuichi Miyahara Hiroshi Abe Yutaka Watanabe 《Metallurgical and Materials Transactions A》2014,45(13):6163-6172
The grain boundary segregation of phosphorus and alloying elements in the heat-affected zone (HAZ) of a low alloy steel was studied quantitatively with atom probe tomography. Non-equilibrium segregation mainly occurred during welding and subsequent fast cooling, leading to remarkable segregation of P, C, Mn, and Mo. The segregation of these four types of solutes showed similar microstructure-dependence at this stage, in which the segregation levels are higher in coarse-grained HAZ and intercritically reheated coarse-grained HAZ than in fine-grained HAZ. After simulated aging, P and Mn showed further enrichment at grain boundaries through equilibrium segregation, while desegregation was observed for C and Mo. In addition, it seems that precipitation of Mo at dislocations was greatly promoted during aging, which probably also contributed to the increase of P and Mn at grain boundaries. 相似文献
127.
Y. Liu S. Tsukamoto T. Shirane F. Abe 《Metallurgical and Materials Transactions A》2013,44(10):4626-4633
The mechanism of type IV failure has been investigated by using a conventional 9Cr ferritic heat-resistant steel Gr.92. In order to clarify the main cause of type IV failure, different heat treatments were performed on the base metal in order to change the prior austenite grain (PAG) size and precipitate distribution after applying the heat-affected zone (HAZ) simulated thermal cycle at the peak temperature of around A c3 (A c3 HAZ thermal cycle) and postweld heat treatment (PWHT). The microstructural evolution during the A c3 HAZ thermal cycle and PWHT was investigated by means of scanning electron microscope (SEM), electron backscatter diffraction (EBSD), electron probe microanalysis (EPMA), and transmission electron microscope (TEM). It was found that M23C6 carbides were scarcely precipitated at the newly formed fine PAG, block, and lath boundaries in A c3 HAZ-simulated Gr.92, because the carbide forming elements such as Cr and C were segregated at the former PAG and block boundaries of the base metal. On the other hand, if all the boundaries were covered by sufficient M23C6 carbides by homogenization of the alloying elements prior to applying the HAZ thermal cycle, the creep strength was much improved even if the fine PAG was formed. From these results, it is concluded that fine-grained microstructure cannot account for the occurrence of type IV failure, and it only has a small effect during long-term creep. The most important factor is the precipitate formation behavior at various boundaries. Without sufficient boundary strengthening by precipitates, the microstructure of A c3 HAZ undergoes severe changes even during PWHT and causes premature failure during creep. 相似文献
128.
Polyvinyl borate (PVBO) was prepared by the condensation of poly(vinyl alcohol) (PVA) and boric acid, and used as a precursor for boron carbide. Boron carbide powder was synthesized by the pyrolysis of the PVBO precursor in air at 600 °C for 2 h, followed by heat treatment in Ar flow at 1300 °C for 5 h, which is a relatively low temperature compared with conventional carbothermal methods. Pyrolysis of the PVBO precursor resulted in submicron-size particles of B2O3 dispersed in a carbon matrix. In addition, the pyrolysis temperature governed the carbon content in the pyrolyzed product of the PVBO precursor, which led to the synthesis of crystalline boron carbide powder with little free carbon. 相似文献
129.
Yasuyoshi Kaneko Shinya Matsushita Yasufumi Oikawa Shigeru Abe 《Electrical Engineering in Japan》2010,172(2):47-54
The equivalent circuit, the efficiency, and the important characteristics of moving pick‐up type contactless power transfer systems are described. If the primary series capacitor and the secondary parallel capacitors are chosen correctly and the winding resistances are ignored, the equivalent circuit of the transformer with these capacitors becomes the same as an ideal transformer at the resonant frequency. This simple approximation helps to understand the phenomena occurring with load changes. Because the circuit analysis becomes simple, the approximate value of the power transfer efficiency can be derived. This paper describes the determination of the capacitor values, the derivation of the equivalent circuit and the efficiency, and test results. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 172(2): 47–54, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20970 相似文献
130.
Atsunori Nozoe Minoru Abe Keisuke Ohto Hidetaka Kawakita 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2011,86(11):1374-1378
BACKGROUND: The formation of polyphenol microspheres by the polymerization of 3‐methylcatechol was performed in a methanol/phosphate buffer solution using horseradish peroxidase (HRP), without the use of a surfactant or a water/oil interface, to be used for germanium recovery. RESULTS: The polyphenol microspheres were of diameter 1 mm. The functional group density of phenol group in the polymer was approximately 15 mol kg?1 determined by the Folin‐Denis method. In batchwise experiments, the amount of germanium adsorbed was 0.23 mol kg?1. CONCLUSION: Because germanium is a rare metal, a system for its recovery is required. Using the proposed system, continuous recovery of germanium can be achieved using multilayered microspheres. Copyright © 2011 Society of Chemical Industry 相似文献