全文获取类型
收费全文 | 1325篇 |
免费 | 20篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 39篇 |
化学工业 | 270篇 |
金属工艺 | 27篇 |
机械仪表 | 27篇 |
建筑科学 | 11篇 |
能源动力 | 41篇 |
轻工业 | 78篇 |
水利工程 | 2篇 |
石油天然气 | 2篇 |
无线电 | 241篇 |
一般工业技术 | 191篇 |
冶金工业 | 304篇 |
原子能技术 | 36篇 |
自动化技术 | 78篇 |
出版年
2023年 | 4篇 |
2022年 | 3篇 |
2021年 | 13篇 |
2020年 | 7篇 |
2019年 | 13篇 |
2018年 | 17篇 |
2017年 | 11篇 |
2016年 | 14篇 |
2015年 | 22篇 |
2014年 | 19篇 |
2013年 | 55篇 |
2012年 | 25篇 |
2011年 | 53篇 |
2010年 | 41篇 |
2009年 | 53篇 |
2008年 | 42篇 |
2007年 | 38篇 |
2006年 | 41篇 |
2005年 | 43篇 |
2004年 | 44篇 |
2003年 | 56篇 |
2002年 | 30篇 |
2001年 | 30篇 |
2000年 | 24篇 |
1999年 | 37篇 |
1998年 | 124篇 |
1997年 | 63篇 |
1996年 | 56篇 |
1995年 | 54篇 |
1994年 | 38篇 |
1993年 | 38篇 |
1992年 | 29篇 |
1991年 | 23篇 |
1990年 | 17篇 |
1989年 | 17篇 |
1988年 | 14篇 |
1987年 | 12篇 |
1986年 | 9篇 |
1985年 | 14篇 |
1984年 | 13篇 |
1983年 | 11篇 |
1982年 | 10篇 |
1981年 | 15篇 |
1980年 | 10篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 11篇 |
1976年 | 10篇 |
1967年 | 5篇 |
1966年 | 3篇 |
排序方式: 共有1347条查询结果,搜索用时 218 毫秒
1.
2.
3.
Russian Journal of Non-Ferrous Metals - In this study, the micro-mechanisms involved in fatigue crack propagation are investigated qualitatively in a Al/Al2O3/SiC hybrid metal matrix composite... 相似文献
4.
Toshihisa Miyazaki Syo Usami Ryo Inoue Yasuo Kogo Yutaro Arai 《Ceramics International》2019,45(7):9560-9566
Si-rich ytterbium silicide was fabricated by through an arc-melting technique for applying use as a bond coat material in an environmental barrier coating system. Evaluation of its potential was accomplished through oxidation tests in dry air and an inert atmosphere. The experimental results showed that the changes in weight and morphologies of ytterbium silicide observed after the tests depended on the oxygen partial pressure. Extensive oxidation and weight gain occurred after oxidation in air. In order to apply this material for hot structures, improvement of the oxidation resistance is needed. 相似文献
5.
Polypropylene plasticization and photodegradation with a TiO2/poly(ethylene oxide)/methyl linoleate paint photocatalyst system 下载免费PDF全文
The photodegradation of polypropylene (PP) film was performed by a TiO2/polyethylene oxide (PEO)/plant oil paint photocatalyst system. The photodegradation underwent two stages of development as follows: Initially PP reacted with linoleic acid radical originated from the photoreaction of plant oil component. Second, the linoleic acid graft‐polymer was decomposed, and then PP chain scission was caused. The process was studied using methyl linoleate (ML) in detail. The melting point of the 24 h‐photodegraded PP slightly decreased, and those of the 48 h‐ and 96 h‐ones drastically did as compared with the pristine PP. The crystallinity (χc) decreased at the 48 h photodegradation time and drastically increased at the 96 h one. The 24 h‐photodegraded PP showed the 77% Young's modulus, 88% tensile strength, and 103% strain at break values to those of the pristine PP. The ML graft‐polymerization and decomposition brought about the PP plasticizing and chemi‐crystallization, causing the PP degradation. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39909. 相似文献
6.
Hiroaki Inoue Yuji Arai Tsunao Kishida Ryu Terauchi Kuniaki Honjo Shuji Nakagawa Shinji Tsuchida Tomohiro Matsuki Keiichirou Ueshima Hiroyoshi Fujiwara Osam Mazda Toshikazu Kubo 《International journal of molecular sciences》2015,16(1):1043-1050
Hypoxia-inducible factor (HIF)-2α is considered to play a major role in the progression of osteoarthritis. Recently, it was reported that pressure amplitude influences HIF-2α expression in murine endothelial cells. We examined whether hydrostatic pressure is involved in expression of HIF-2α in articular chondrocytes. Chondrocytes were cultured and stimulated by inflammation or hydrostatic pressure of 0, 5, 10, or 50 MPa. After stimulation, heat shock protein (HSP) 70, HIF-2α, nuclear factor kappa B (NF-κB), matrix metalloproteinase (MMP)-13, MMP-3, and vascular endothelial growth factor (VEGF) gene expression were evaluated. The levels of all gene expression were increased by inflammatory stress. When chondrocytes were exposed to a hydrostatic pressure of 5 MPa, HIF-2α, MMP-13, and MMP-3 gene expression increased significantly although those of HSP70 and NF-κB were not significantly different from the control group. In contrast, HIF-2α gene expression did not increase under a hydrostatic pressure of 50 MPa although HSP70 and NF-κB expression increased significantly compared to control. We considered that hydrostatic pressure of 5 MPa could regulate HIF-2α independent of NF-κB, because the level of HIF-2α gene expression increased significantly without upregulation of NF-κB expression at 5 MPa. Hydrostatic pressure may influence cartilage degeneration, inducing MMP-13 and MMP-3 expression through HIF-2α. 相似文献
7.
Takeshi Takahashi Kyosuke Kojima Wei Zhang Kanae Sasaki Masaru Ito Hironori Suzuki Masato Kawasaki Soichi Wakatsuki Terunao Takahara Hideki Shibata Masatoshi Maki 《International journal of molecular sciences》2015,16(2):3677-3699
ALG-2, a 22-kDa penta-EF-hand protein, is involved in cell death, signal transduction, membrane trafficking, etc., by interacting with various proteins in mammalian cells in a Ca2+-dependent manner. Most known ALG-2-interacting proteins contain proline-rich regions in which either PPYPXnYP (type 1 motif) or PXPGF (type 2 motif) is commonly found. Previous X-ray crystal structural analysis of the complex between ALG-2 and an ALIX peptide revealed that the peptide binds to the two hydrophobic pockets. In the present study, we resolved the crystal structure of the complex between ALG-2 and a peptide of Sec31A (outer shell component of coat complex II, COPII; containing the type 2 motif) and found that the peptide binds to the third hydrophobic pocket (Pocket 3). While amino acid substitution of Phe85, a Pocket 3 residue, with Ala abrogated the interaction with Sec31A, it did not affect the interaction with ALIX. On the other hand, amino acid substitution of Tyr180, a Pocket 1 residue, with Ala caused loss of binding to ALIX, but maintained binding to Sec31A. We conclude that ALG-2 recognizes two types of motifs at different hydrophobic surfaces. Furthermore, based on the results of serial mutational analysis of the ALG-2-binding sites in Sec31A, the type 2 motif was newly defined. 相似文献
8.
Regime shifts observed in Lake Kasumigaura,a large shallow lake in Japan: Analysis of a 40‐year limnological record 下载免费PDF全文
Lake Kasumigaura, which is composed of the two basins (Nishiura and Kitaura), is a large, shallow, hypereutrophic lake. Phytoplankton and water quality records from the past forty years were analysed to elucidate whether or not, when, and what type of certain regime shifts may have occurred, based on using inferential regime shift detectors. Characteristics of the phytoplankton and water quality changes were similar at 6 sampling sites in the two basins, with 20 water quality parameters being classified into four groups, based on cluster analysis. Shifts in dominant plankton groups (DPGs) and water quality occurring almost concomitantly, concentration on the period from 1987 to 1992 (Shift A) and from 1997 to 2001 (Shift B), with those observed for the two basins usually being similar with small differences. Two types of inferential regime shift detectors (sequential t‐test type; Rodionov's RSD and sequential F‐test type: package strucchange in R) yielded similar timings and significances of the shifts. Furthermore, changes in skewness and conditional heteroskedasticity (package early warnings in R) usually represented early warning signals before the shifts. Correlation analysis and ratios of dissolved inorganic nitrogen (DIN) vs. total phosphorus (TP) supported the hypothesis that phosphorus was the phytoplankton biomass limiting nutrient, except for one period for the Nishiura basin. Neither the nitrogen:phosphorus (N/P) ratio hypothesis and ammonia–nitrate (NH4‐N/NO3‐N) hypothesis satisfactorily explain the DPGs before and after Shift A (Microcystis spp. and Planktothrix spp., respectively), although it may be possible that these ratios triggered the DPG change in this shift. A considerable increase in silicon was observed for Shift B when the DPGs changed from cyanobacteria to diatoms. Further studies on the accurate types and triggers of the regime shifts are necessary to better understand the interactions between ecosystem and water quality for this and similar lakes elsewhere. 相似文献
9.
Abstract A method of describing centrosymmetric gratings (radial, circular and spiral) is presented. The moiré-fringe profile produced by centrosymmetric gratings is analysed using polar coordinates. The concept of the angle of intersection for two superimposed gratings is examined and it is shown how from this study moiré patterns formed from centrosymmetric gratings can be analysed automatically by digital computer. Examples of theoretically predicted patterns, generated by the proposed procedure, are compared with actual moiré-fringe patterns. This method provides for the first time a procedure that can be used in engineering for improving the contrast of moiré patterns and for sharpening these patterns. 相似文献
10.
Recent progress in thermal analysis of polymers: experimental techniques and a new aspect of temperature in measurement of material properties 下载免费PDF全文
Thermal analysis has been utilized in polymer research for a long time and its usefulness is widely recognized. High‐performance commercial instruments have driven significant progress in the thermal studies of polymers. On the other hand, new experimental instruments have been developed in laboratories as well. In this paper attention is paid to the latter category. The laboratory‐made instrument focused on the target material and/or phenomena provides data that are not available from other techniques. Experiments using the temperature modulation technique, which has been successfully utilized in laboratory‐made instruments, are introduced in this paper. The temperature modulation technique reveals a new aspect of temperature useful for studies of material properties. © 2016 Society of Chemical Industry 相似文献