全文获取类型
收费全文 | 1610篇 |
免费 | 44篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 112篇 |
综合类 | 2篇 |
化学工业 | 542篇 |
金属工艺 | 59篇 |
机械仪表 | 57篇 |
建筑科学 | 41篇 |
矿业工程 | 1篇 |
能源动力 | 111篇 |
轻工业 | 117篇 |
水利工程 | 4篇 |
石油天然气 | 4篇 |
无线电 | 55篇 |
一般工业技术 | 306篇 |
冶金工业 | 43篇 |
原子能技术 | 39篇 |
自动化技术 | 174篇 |
出版年
2023年 | 7篇 |
2022年 | 33篇 |
2021年 | 44篇 |
2020年 | 22篇 |
2019年 | 21篇 |
2018年 | 36篇 |
2017年 | 23篇 |
2016年 | 29篇 |
2015年 | 16篇 |
2014年 | 31篇 |
2013年 | 81篇 |
2012年 | 63篇 |
2011年 | 120篇 |
2010年 | 69篇 |
2009年 | 75篇 |
2008年 | 88篇 |
2007年 | 63篇 |
2006年 | 55篇 |
2005年 | 63篇 |
2004年 | 48篇 |
2003年 | 52篇 |
2002年 | 42篇 |
2001年 | 34篇 |
2000年 | 25篇 |
1999年 | 31篇 |
1998年 | 46篇 |
1997年 | 45篇 |
1996年 | 27篇 |
1995年 | 25篇 |
1994年 | 39篇 |
1993年 | 25篇 |
1992年 | 21篇 |
1991年 | 19篇 |
1990年 | 12篇 |
1989年 | 17篇 |
1988年 | 20篇 |
1987年 | 18篇 |
1986年 | 25篇 |
1985年 | 19篇 |
1984年 | 14篇 |
1983年 | 18篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 15篇 |
1979年 | 19篇 |
1978年 | 13篇 |
1977年 | 8篇 |
1974年 | 4篇 |
1971年 | 4篇 |
1967年 | 4篇 |
排序方式: 共有1667条查询结果,搜索用时 0 毫秒
991.
洋麻以其价廉质轻、纤维拉伸强度高和产量高等特性而广泛应用于各种环保领域。文中综述了近年来洋麻增强复合材料的研究开发,介绍了洋麻秆芯和其韧皮纤维增强复合材料的制备成型方法、力学性能和应用,并展望了该类复合材料的未来发展趋势。 相似文献
992.
Arpita Varadwaj Pradeep R. Varadwaj Helder M. Marques Koichi Yamashita 《International journal of molecular sciences》2022,23(9)
A stibium bond, i.e., a non-covalent interaction formed by covalently or coordinately bound antimony, occurs in chemical systems when there is evidence of a net attractive interaction between the electrophilic region associated with an antimony atom and a nucleophile in another, or the same molecular entity. This is a pnictogen bond and are likely formed by the elements of the pnictogen family, Group 15, of the periodic table, and is an inter- or intra-molecular non-covalent interaction. This overview describes a set of illustrative crystal systems that were stabilized (at least partially) by means of stibium bonds, together with other non-covalent interactions (such as hydrogen bonds and halogen bonds), retrieved from either the Cambridge Structure Database (CSD) or the Inorganic Crystal Structure Database (ICSD). We demonstrate that these databases contain hundreds of crystal structures of various dimensions in which covalently or coordinately bound antimony atoms in molecular entities feature positive sites that productively interact with various Lewis bases containing O, N, F, Cl, Br, and I atoms in the same or different molecular entities, leading to the formation of stibium bonds, and hence, being partially responsible for the stability of the crystals. The geometric features, pro-molecular charge density isosurface topologies, and extrema of the molecular electrostatic potential model were collectively examined in some instances to illustrate the presence of Sb-centered pnictogen bonding in the representative crystal systems considered. 相似文献
993.
Sakai S Antoku K Yamaguchi T Kawakami K 《Journal of Bioscience and Bioengineering》2008,105(6):687-689
We entrapped lipase in electrospun poly(vinyl alcohol) fibers of approximately 1 mum in diameter and evaluated the transesterification activity by converting (s)-glycidol to glycidyl n-butyrate with vinyl n-butyrate. The initial transesterification rate of the entrapped lipase was 5.2-fold faster than that of non-treated lipase. The fibrous membrane could be used as a component of a flow-through reactor for continuous transesterification. 相似文献
994.
Yasuaki Tatsumi Ayako Kato Naoko Niimi Hideji Yako Tatsuhito Himeno Masaki Kondo Shin Tsunekawa Yoshiro Kato Hideki Kamiya Jiro Nakamura Koji Higai Kazunori Sango Koichi Kato 《International journal of molecular sciences》2022,23(8)
Autophagy is the process by which intracellular components are degraded by lysosomes. It is also activated by oxidative stress; hence, autophagy is thought to be closely related to oxidative stress, one of the major causes of diabetic neuropathy. We previously reported that docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) induced antioxidant enzymes and protected Schwann cells from oxidative stress. However, the relationship between autophagy and oxidative stress-induced cell death in diabetic neuropathy has not been elucidated. Treatment with tert-butyl hydroperoxide (tBHP) decreased the cell survival rate, as measured by an MTT assay in immortalized Fischer rat Schwann cells 1 (IFRS1). A DHA pretreatment significantly prevented tBHP-induced cytotoxicity. tBHP increased autophagy, which was revealed by the ratio of the initiation markers, AMP-activated protein kinase, and UNC51-like kinase phosphorylation. Conversely, the DHA pretreatment suppressed excessive tBHP-induced autophagy signaling. Autophagosomes induced by tBHP in IFRS1 cells were decreased to control levels by the DHA pretreatment whereas autolysosomes were only partially decreased. These results suggest that DHA attenuated excessive autophagy induced by oxidative stress in Schwann cells and may be useful to prevent or reduce cell death in vitro. However, its potentiality to treat diabetic neuropathy must be validated in in vivo studies. 相似文献
995.
Syahputra Wibowo Jessica Costa Maria Camilla Baratto Rebecca Pogni Sri Widyarti Akhmad Sabarudin Koichi Matsuo Sutiman Bambang Sumitro 《International journal of molecular sciences》2022,23(9)
Glycated human serum albumin (gHSA) undergoes conformational changes and unfolding events caused by free radicals. The glycation process results in a reduced ability of albumin to act as an endogenous scavenger and transporter protein in diabetes mellitus type 2 (T2DM) patients. Astaxanthin (ASX) in native form and complexed with metal ions (Cu2+ and Zn2+) has been shown to prevent gHSA from experiencing unfolding events. Furthermore, it improves protein stability of gHSA and human serum albumin (HSA) as it is shown through molecular dynamics studies. In this study, the ASX/ASX-metal ion complexes were reacted with both HSA/gHSA and analyzed with electronic paramagnetic resonance (EPR) spectroscopy, rheology and zeta sizer (particle size and zeta potential) analysis, circular dichroism (CD) spectroscopy and UV-Vis spectrophotometer measurements, as well as molecular electrostatic potential (MEP) and molecular docking calculations. The addition of metal ions to ASX improves its ability to act as an antioxidant and both ASX or ASX-metal ion complexes maintain HSA and gHSA stability while performing their functions. 相似文献
996.
Koichi Okada Atsushi Fushimi Shun Sekimoto Tsutomu Ohtsuki 《Journal of Nuclear Science and Technology》2020,57(5):514-522
ABSTRACTMonitoring only neutron flux in a nuclear reactor core has an advantage of offering reactor power monitoring accuracy. We started the development of a new nuclear instrumentation based on the measurement of prompt gamma rays emitted from metals placed at the neutron flux monitoring positions. The thermal neutron flux at the position of each placed metal piece can be monitored by measuring the prompt gamma rays as the count rate of each energy. The gamma-ray energy range was limited from 6 to 10 MeV to mitigate the interference of environmental gamma rays. Four metals, Ti, V, Ni, and Cu, were chosen as candidates in consideration of their neutron emission rates and self-absorption. In an experiment with a high-purity germanium semiconductor detector, we considered the identification of individual peak energies in an assumed situation where prompt gamma rays were emitted from the four different metals at the same time. Energy resolutions of the peak with the largest energy gap from the nearest energy peak of the other candidate metals were smaller than the gap. Thus, we confirmed that at least one peak for each candidate metal was able to be separated from the peaks derived from other candidate metals. 相似文献
997.
Michiyo Honda Koichi Kikushima Yusuke Kawanobe Toshiisa Konishi Minori Mizumoto Mamoru Aizawa 《Journal of materials science. Materials in medicine》2012,23(12):2923-2932
The influence of silicon-substituted hydroxyapatite (Si-HAp) on osteogenic differentiation was assessed by biological analysis. Si-HAp was prepared by ultrasonic spray pyrolysis (USSP) technique using various amounts of Si (0, 0.8, and 1.6 mass%). Chemical analysis revealed that Si was incorporated into the hydroxyapatite (HAp) lattice with no other crystalline phase and which caused the change of crystal structure. Biological analyses showed that the Si contents affected the cell proliferation and morphology, suggesting that there is an optimal Si content for cell culture. As for differentiation, alkaline phosphatase activity and osteocalcin production of Si-HAp were higher than those of HAp. Gene expression profiles also revealed that substitution of Si (0.8 mass%) up-regulated the expression levels of osteocalcin and especially Runx2, a master gene for osteoblast development. These results suggest that incorporating Si into the HAp lattice may enhance the bioactivity, particularly during early osteoblast development. 相似文献
998.
Nakamura T Kashima Y Mine S Oku T Uegaki K 《Journal of Bioscience and Bioengineering》2012,114(2):150-154
We characterized and determined the crystal structure of a putative glucokinase/hexokinase from Thermus thermophilus that belongs to the ROK (bacterial repressors, uncharacterized open reading frames, and sugar kinases) family. The protein possessed significant enzymatic activity against glucose and mannose, with V(max) values of 260 and 68 μmol·min(-1)·mg(-1) protein, respectively. Therefore, we concluded that the enzyme is a hexokinase. However, the hexokinase showed little catalytic capacity for galactose and fructose. Circular dichroism measurements indicated that the enzyme was structurally stable at 90°C. The crystal structure of the enzyme was determined at a resolution of 2.02 ?, with R(cryst) and R(free) values of 18.1% and 22.6%, respectively. The polypeptide structure was divided into large and small domains. The ROK consensus sequences 1 and 2 were included in the large domain. The cysteine-rich consensus sequence 2 folded into a zinc finger, and the bound zinc was confirmed by both electron density and X-ray absorption fine structure (XAFS) spectrum. The overall structure was a homotetramer that consisted of a dimer of dimers. The accessible surface area buried by the association of the dimers into the tetrameric structures was significantly higher in the T. thermophilus enzyme than in a homologous tetrameric ROK sugar kinase. 相似文献
999.
Flaxseed lignan, secoisolariciresinol has been reported to possess health benefits. We previously synthesized each stereoisomer of secoisolariciresinol and found that (-)-secoisolariciresinol reduces lipid accumulation and induces adiponectin production in 3T3-L1 adipocytes. Here we show the effects of (-)-secoisolariciresinol on high-fat diet-induced obesity in C57BL/6 male mice. Oral administration of (-)-secoisolariciresinol for 28 consecutive days significantly suppressed the gain of body weight. Increased serum adiponectin level and decreased gene expression of fatty acid synthase and sterol regulatory element-binding protein-1c in liver, which are related to fatty acid synthesis, were observed in the mice orally administered with (-)-secoisolariciresinol. In addition, subcutaneous injection of (-)-secoisolariciresinol also significantly suppressed the gain of body weight. Serum leptin levels were significantly increased by treating with (-)-secoisolariciresinol or (-)-enterolactone. Subcutaneous injection of (-)-secoisolariciresinol, (-)-enterolactone, or (-)-enterodiol promoted gene expression of acyl-CoA oxidase, carnitine palmitoyl transferase-1, and peroxisome proliferator-activated receptor α, which are related to β-oxidation. Overall results suggest that (-)-secoisolariciresinol exerts a suppressive effect on the gain of body weight of mice fed a high-fat diet by inducing gene expression of adiponectin, resulting in the altered expression of various genes related to the synthesis and β-oxidation of fatty acids. 相似文献
1000.
In this paper, focusing on visual management (VM) as one of the kaizen technologies, a procedure for its new case development is discussed. This procedure consists of two portions. The first portion is construction of kaizen case-base, namely: (1) correction and analysis of kaizen cases; (2) establishment of drivers and instances of investigated kaizen case; and (3) analysis of proximity relationship among kaizen cases. The second portion is utilisation of kaizen case-base, namely: (4) selection of kaizen case from kaizen case-base; (5) consideration of the other related kaizen cases; and (6) new kaizen case design. A case study is performed to assure the relevance of the proposed procedure by focusing on ‘dispatching board’, a typical VM technology. Through collaboration with a factory eager to implement VM, the proposed procedure is qualified by experts as a useful method for kaizen knowledge transfer. 相似文献