全文获取类型
收费全文 | 3296篇 |
免费 | 51篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 132篇 |
综合类 | 7篇 |
化学工业 | 582篇 |
金属工艺 | 169篇 |
机械仪表 | 57篇 |
建筑科学 | 50篇 |
矿业工程 | 5篇 |
能源动力 | 70篇 |
轻工业 | 151篇 |
水利工程 | 15篇 |
石油天然气 | 2篇 |
无线电 | 415篇 |
一般工业技术 | 525篇 |
冶金工业 | 861篇 |
原子能技术 | 87篇 |
自动化技术 | 232篇 |
出版年
2023年 | 7篇 |
2022年 | 22篇 |
2021年 | 43篇 |
2020年 | 16篇 |
2019年 | 25篇 |
2018年 | 31篇 |
2017年 | 26篇 |
2016年 | 28篇 |
2015年 | 21篇 |
2014年 | 51篇 |
2013年 | 132篇 |
2012年 | 95篇 |
2011年 | 139篇 |
2010年 | 98篇 |
2009年 | 131篇 |
2008年 | 140篇 |
2007年 | 107篇 |
2006年 | 89篇 |
2005年 | 87篇 |
2004年 | 95篇 |
2003年 | 90篇 |
2002年 | 93篇 |
2001年 | 73篇 |
2000年 | 63篇 |
1999年 | 68篇 |
1998年 | 338篇 |
1997年 | 187篇 |
1996年 | 171篇 |
1995年 | 100篇 |
1994年 | 92篇 |
1993年 | 93篇 |
1992年 | 47篇 |
1991年 | 40篇 |
1990年 | 36篇 |
1989年 | 48篇 |
1988年 | 49篇 |
1987年 | 44篇 |
1986年 | 29篇 |
1985年 | 33篇 |
1984年 | 29篇 |
1983年 | 31篇 |
1982年 | 33篇 |
1981年 | 33篇 |
1980年 | 38篇 |
1979年 | 19篇 |
1978年 | 19篇 |
1977年 | 19篇 |
1976年 | 34篇 |
1975年 | 9篇 |
1973年 | 4篇 |
排序方式: 共有3360条查询结果,搜索用时 62 毫秒
61.
连铸中间包内三维湍流流动的数值模拟 总被引:11,自引:0,他引:11
连铸中间包的操作条件决定了其内流动现象的复杂性,为此,本文选择两种不同的湍流模型k-ε和LES(Largeeddysimulation),建立了描述连铸中间包内三维湍流流动的数学模型,并实施了数值计算和模型验证,对单流中间包内的流动现象进行了描述,考察了有,无流动控制情况下中间包内的流动特征和湍流模型的合理性,结果表明,合理的流动控制有利于中间包内非金属夹杂的上浮和吸附,用k-ε模型基本上能够描述 相似文献
62.
Natsuhiko Kuratomi Shinichi Takano Mitsuharu Fukasawa Shinya Maekawa Makoto Kadokura Hiroko Shindo Ei Takahashi Sumio Hirose Yoshimitsu Fukasawa Satoshi Kawakami Hiroshi Hayakawa Hitomi Takada Natsuko Nakakuki Ryoh Kato Tatsuya Yamaguchi Yasuhiro Nakayama Hiromichi Kawaida Hiroshi Kono Taisuke Inoue Tetsuo Kondo Daisuke Ichikawa Nobuyuki Enomoto 《International journal of molecular sciences》2021,22(6)
New biomarkers are needed to further stratify the risk of malignancy in intraductal papillary mucinous neoplasm (IPMN). Although microRNAs (miRNAs) are expected to be stable biomarkers, they can vary owing to a lack of definite internal controls. To identify universal biomarkers for invasive IPMN, we performed miRNA sequencing using tumor-normal paired samples. A total of 19 resected tissues and 13 pancreatic juice samples from 32 IPMN patients were analyzed for miRNA expression by next-generation sequencing with a two-step normalization of miRNA sequence data. The miRNAs involved in IPMN associated with invasive carcinoma were identified from this tissue analysis and further verified with the pancreatic juice samples. From the tumor-normal paired tissue analysis of the expression levels of 2792 miRNAs, 20 upregulated and 17 downregulated miRNAs were identified. In IPMN associated with invasive carcinoma (INV), miR-10a-5p and miR-221-3p were upregulated and miR-148a-3p was downregulated when compared with noninvasive IPMN. When these findings were further validated with pancreatic juice samples, miR-10a-5p was found to be elevated in INV (p = 0.002). Therefore, three differentially expressed miRNAs were identified in tissues with INV, and the expression of miR-10a-5p was also elevated in pancreatic juice samples with INV. MiR-10a-5p is a promising additional biomarker for invasive IPMN. 相似文献
63.
Dr. Daisuke Fujiwara Kousuke Mihara Ryo Takayama Yusuke Nakamura Prof. Mitsuhiro Ueda Prof. Takeshi Tsumuraya Prof. Ikuo Fujii 《Chembiochem : a European journal of chemical biology》2021,22(24):3406-3409
Conformationally constrained peptides hold promise as molecular tools in chemical biology and as a new modality in drug discovery. The construction and screening of a target-focused library could be a promising approach for the generation of de novo ligands or inhibitors against target proteins. Here, we have prepared a protein kinase-focused library by chemically modifying helix-loop-helix (HLH) peptides displayed on phage and subsequently tethered to adenosine. The library was screened against aurora kinase A (AurA). The selected HLH peptide Bip - 3 retained the α-helical structure and bound to AurA with a KD value of 13.7 μM. Bip - 3 and the adenosine-tethered peptide Bip - 3 - Adc provided IC50 values of 103 μM and 7.7 μM, respectively, suggesting that Bip - 3 - Adc bivalently inhibited AurA. In addition, the selectivity of Bip - 3 - Adc to several protein kinases was tested, and was highest against AurA. These results demonstrate that chemical modification can enable the construction of a kinase-focused library of phage-displayed HLH peptides. 相似文献
64.
65.
The effect of the buffer capacity of test solution on the corrosion rate of cast pure (>99.95 mass%) and high-purity (>99.9999 mass%) magnesium, and AZ31 and AZ91E has been studied. Their corrosion rates were measured gravimetrically in a pH 6.5 and a pH 9 borate buffer including chloride ions, and in a conventional chloride solution. Except for the AZ91E in the pH 6.5, the corrosion rates of all the examined materials depended solely on the pH of the test solution, although the materials had a variety of purity and alloying elements. Higher buffer capacity probably masked the detrimental effect of the “cathodic impurities”. The corrosion rates measured in the buffers were considered as giving the resistivity of the passive film to anodic reactions. The high-purity magnesium had a fair corrosion resistance even in conventional chloride solution. 相似文献
66.
In Situ Observation of Phase Separation of a Barium Borate Melt in a Stable Immiscibility Region under Microgravity 总被引:1,自引:0,他引:1
Satoru Inoue Akio Makishima Hiroyuki Inoue Kohei Soga Tomoya Konishi Tomoyoshi Asano Yuu Ishii Masato Koyama 《Journal of the American Ceramic Society》1997,80(9):2413-2417
The precipitation of droplets was directly observed on a BaO–B2 O3 melt in a drop shaft experiment. This is the first time that precipitation of droplets has been observed in a 4.5 s drop test. The melt film of 4BaOz96B2 O3 (mol%) held on a platinum wire loop was heated above the critical tem-perature to produce uniformity and was cooled down to the phase separation temperature range. Phase separation of the melt was observed directly with a video camera. The IR image of the melt was simultaneously detected with a CCD array and was converted into a two-dimensional thermograph. 相似文献
67.
Synthesis of Thermally Stable χ-Alumina by Thermal Decomposition of Aluminum Isopropoxide in Toluene
Okorn Mekasuwandumrong Hiroshi Kominami Piyasan Praserthdam Masashi Inoue 《Journal of the American Ceramic Society》2004,87(8):1543-1549
Thermal decomposition of aluminum isopropoxide in toluene at 315°C resulted in χ-alumina that had high thermal stability, whereas the reaction at lower temperatures resulted in formation of an amorphous product. The χ-alumina thus obtained directly transformed to α-alumina at ∼1150°C, bypassing the other transition alumina phases, whereas the amorphous product transformed to γ-alumina and then to θ-alumina before final transformation to α-alumina. When the χ-alumina, solvothermally synthesized at 315°C, was recovered by the removal of the solvent at the reaction temperature, thermal stability of the product was improved further. This procedure is convenient because it avoids bothersome work-up processes that yield large-surface-area and large-pore-volume alumina. 相似文献
68.
Hydrothermal reactions of fumed silica with lime at 80°C were studied at starting Ca/Si of 0.8–2.0 and water/solid ratio of 20 by weight under periods of reaction time from 10 to 100 days.In the early ages of reaction, CSH having weak and diffuse basal reflections between 10–15Å was formed. On prolonging the reaction, CSH from the starting Ca/Si of 1.2–1.5 crystallised to jennite, and that from the starting Ca/Si of 0.9 to 14Å tobermorite.Lattice parameters were determined on the well crystalline jennite obtained by the reaction for 100 days at the starting Ca/Si of 1.4; i.e. ao 10.59, bo 7.21, co 10.82Å, α 99.60°, β 97.78°, γ 109.85°. Its crystals were lath-like elongated parallel to b with (001) cleavage.It was confirmed that the synthetic jennite was converted to meta-jennite by losing a part of its water on heating in air at 90°C. At higher temperatures it became poorly crystalline, and then crystallised to β-CaSiO3 and β-Ca2SiO4 at 800°C. 相似文献
69.
A poled ferroelectric LiNbO3 single crystal with high spontaneous polarization was employed as a catalyst support, and the static and dynamic effects of the polar substrate surfaces on the adsorptive and catalytic properties of thin film catalysts deposited were shown. For the static effect, it was demonstrated that the surface conductivity of copper and metal-free phthalocyanine films increased by the adsorption of NO gas, to a larger extent, when the substrate was the negative polar surface, compared to the positive one. The role of the polar substrates is explained In terms of a band bending model. For the dynamic effect, the Rayleigh surface acoustic wave generated on the LiNbO3 substrate was shown to enhance the catalytic activity for ethanol oxidation on Cu and Ag thin film catalysts deposited on the propagation path. It is proposed that the catalyst activation is mainly due to an electric Held produced. The use of poled LiNbO3 is suggested to be effective for the development of a device-type catalyst with activity controllable functions. 相似文献
70.
Curing catalyst for epoxy resins was newly found. The catalyst consists of aluminum complex and silanol. Lack of one component of the pair does not cure epoxy resins. The epoxy resins cured with the catalyst are characterized by excellent electrical properties, especially at high temperature, due to the absence of strong acid species in the cured epoxy resin matrix. Heat-resistant property of the resin was also excellent. These properties were compared with those of epoxy resin cured with commonly used BF3 complex. 相似文献