全文获取类型
收费全文 | 5186篇 |
免费 | 135篇 |
国内免费 | 27篇 |
专业分类
电工技术 | 412篇 |
综合类 | 17篇 |
化学工业 | 1500篇 |
金属工艺 | 136篇 |
机械仪表 | 138篇 |
建筑科学 | 189篇 |
矿业工程 | 1篇 |
能源动力 | 244篇 |
轻工业 | 506篇 |
水利工程 | 19篇 |
石油天然气 | 7篇 |
无线电 | 286篇 |
一般工业技术 | 916篇 |
冶金工业 | 180篇 |
原子能技术 | 215篇 |
自动化技术 | 582篇 |
出版年
2023年 | 30篇 |
2022年 | 59篇 |
2021年 | 96篇 |
2020年 | 52篇 |
2019年 | 63篇 |
2018年 | 75篇 |
2017年 | 63篇 |
2016年 | 112篇 |
2015年 | 79篇 |
2014年 | 151篇 |
2013年 | 320篇 |
2012年 | 185篇 |
2011年 | 307篇 |
2010年 | 257篇 |
2009年 | 279篇 |
2008年 | 314篇 |
2007年 | 262篇 |
2006年 | 203篇 |
2005年 | 220篇 |
2004年 | 176篇 |
2003年 | 161篇 |
2002年 | 165篇 |
2001年 | 105篇 |
2000年 | 97篇 |
1999年 | 97篇 |
1998年 | 104篇 |
1997年 | 73篇 |
1996年 | 71篇 |
1995年 | 55篇 |
1994年 | 81篇 |
1993年 | 69篇 |
1992年 | 55篇 |
1991年 | 75篇 |
1990年 | 52篇 |
1989年 | 77篇 |
1988年 | 65篇 |
1987年 | 39篇 |
1986年 | 73篇 |
1985年 | 56篇 |
1984年 | 53篇 |
1983年 | 57篇 |
1982年 | 60篇 |
1981年 | 47篇 |
1980年 | 42篇 |
1979年 | 41篇 |
1978年 | 41篇 |
1977年 | 28篇 |
1976年 | 28篇 |
1975年 | 18篇 |
1973年 | 17篇 |
排序方式: 共有5348条查询结果,搜索用时 20 毫秒
991.
Shogo Takeda Akari Yoneda Kenchi Miyasaka Yoshiaki Manse Toshio Morikawa Hiroshi Shimoda 《International journal of molecular sciences》2023,24(1)
Ceramide (Cer) plays an important role in skin barrier functions in the stratum corneum (SC). The ingestion of food-derived glucosylceramides (GlcCer) attenuates transepidermal water loss (TEWL). However, the moisturizing effects of single molecules of GlcCer and Cer remain unclear. Therefore, we herein purified 13 GlcCer and 6 Cer, including elasticamide, which has the same structure as human Cer[AP], from rice and compared their epidermal moisturizing effects in a reconstructed human epidermal keratinization model. The results obtained showed that 10 µM of 5 GlcCer[d18:2] with a 4E,8Z sphingadienine and C18 to C26 fatty acids and 10 µg/mL of 3 Cer with C23 or C24 fatty acids significantly reduced TEWL. The moisturizing effects of these GlcCer were dependent on the length of fatty acids. Furthermore, 10 µg/mL of elasticamide increased the SC Cer contents by promoting the expression of GlcCer synthase. Electron microscopic observations revealed that 1 µM of GlcCer[d18:2(4E,8Z)/26:0] increased the number of keratohyalin granules and desmosomes. Immunostaining and Western blotting indicated that 1 µM of GlcCer[d18:2(4E,8Z)/26:0] up-regulated the expression of filaggrin and corneodesmosin, which contribute to epidermal hydration. This comparative study on epidermal moisturization by GlcCer and Cer isolated from rice revealed differences in their hydration mechanisms. 相似文献
992.
993.
994.
The unsteady behavior of flow driven by a jet suddenly injected into a cell is numerically studied by solving the axisymmelric two-dimensional compressible Navier-Stokes equations. The system of the calculation is a model of the laser ablation of a certain duration followed by a discharging process through the exit hole at the down- stream end of the cell. In the calculations, the contour of the cell is changed while other parameters such as the Mach number of the jet, its duration, and the diameter of the cell exit are fixed. Monitoring the velocity at the exit hole is used to investigate the influence of the shape on the interaction between the shock wave and the jet. As the result, it was found that the velocity peak value and its arrival time at the downstream end of the cell exit are determined by the diameter of the cell. 相似文献
995.
Hanh Hong Chu Yoshiki Kobayashi Dan Van Bui Yasutaka Yun Linh Manh Nguyen Akitoshi Mitani Kensuke Suzuki Mikiya Asako Akira Kanda Hiroshi Iwai 《International journal of molecular sciences》2022,23(24)
Eosinophilic chronic rhinosinusitis (ECRS) is a refractory airway disease accompanied by eosinophilic inflammation, the mechanisms of which are unknown. We recently found that CCL4/MIP-1β—a specific ligand for CCR5 receptors—was implicated in eosinophil recruitment into the inflammatory site and was substantially released from activated eosinophils. Moreover, it was found in nasal polyps from patients with ECRS, primarily in epithelial cells. In the present study, the role of epithelial cell-derived CCL4 in eosinophil activation was investigated. First, CCL4 expression in nasal polyps from patients with ECRS as well as its role of CCL4 in eosinophilic airway inflammation were investigated in an in vivo model. Furthermore, the role of CCL4 in CD69 expression—a marker of activated eosinophils—as well as the signaling pathways involved in CCL4-mediated eosinophil activation were investigated. Notably, CCL4 expression, but not CCL5, CCL11, or CCL26, was found to be significantly increased in nasal polyps from patients with ECRS associated with eosinophil infiltration as well as in BEAS-2B cells co-incubated with eosinophils. In an OVA-induced allergic mouse model, CCL4 increased eosinophil accumulation in the nasal mucosa and the bronchoalveolar lavage (BALF). Moreover, we found that CD69 expression was upregulated in CCL4-stimulated eosinophils; similarly, phosphorylation of several kinases, including platelet-derived growth factor receptor (PDGFR)β, SRC kinase family (Lck, Src, and Yes), and extracellular signal-regulated kinase (ERK), was upregulated. Further, CCR5, PDGFRβ, and/or Src kinase inhibition partially restored CCL4-induced CD69 upregulation. Thus, CCL4, which is derived from airway epithelial cells, plays a role in the accumulation and activation of eosinophils at inflammatory sites. These findings may provide a novel therapeutic target for eosinophilic airway inflammation, such as ECRS. 相似文献
996.
This paper analyzes the behaviour of coating particles as well as the gas flow both inside and outside of the High-Velocity Oxy-Fuel (HVOF) thermal spray gun by using a quasi-one-dimensional analysis and a numerical simulation. The HVOF gun in the present analysis is an axially symmetric convergent-divergent nozzle with the design Mach number of 2.0. From the present analysis, the distributions of velocity and temperature of the coating particles flying inside and outside of the HVOF gun are predicted. The velocity and temperature of the coating particles at the exit of the gun calculated by the present method agree well with the previous experimental results. Therefore, the present method of calculation is considered to be useful for predicting the HVOF gas and particle flows. 相似文献
997.
脂肪醇制备叔胺的新型催化剂的最新进展 总被引:2,自引:0,他引:2
对采用脂肪醇和二甲胺一步胺化制备(得率100%)相应的叔胺(烷基二甲基叔胺)的新型催化剂的最新进展进行了论述,对高活性Cu/Ni/Ca/Ba-St胶体催化剂(Cu0/Ni0/Ca0的比为5∶1∶1)和不含镍的Cu/La2O3进行了讨论。由此得出结论:要达到定量制备的关键因素是,通过结合还原钙或更活泼的促进剂,如Ce0和La0,尽可能地增加催化体系的氢解活性,由此形成金属氢化物,在铜/镍的作用下产生活性氢的“自供体系”。这一就地形成金属氢化物的基本功能将可极大地减少催化剂的用量,使铜质量分数减少到2×10-3%,从而极大地降低二甲胺的歧化,增加目的叔胺的选择性。总的来说,观察到在铜/镍固体催化剂以及胶体催化剂作用下,活性氢自供体系的基本功能使充入的大量氢一点都不被消耗掉。 相似文献
998.
Tianhao Wu Zhenzhen Qin Yanbo Wang Yongzhen Wu Wei Chen Shufang Zhang Molang Cai Songyuan Dai Jing Zhang Jian Liu Zhongmin Zhou Xiao Liu Hiroshi Segawa Hairen Tan Qunwei Tang Junfeng Fang Yaowen Li Liming Ding Zhijun Ning Yabing Qi Yiqiang Zhang Liyuan Han 《纳微快报(英文)》2021,(10):113-130
Perovskite solar cells (PSCs) emerging as a promising photovoltaic technology with high efficiency and low manufacturing cost have attracted the attention from ... 相似文献
999.
Generalized-Extended-State-Observer and Equivalent-Input-Disturbance Methods for Active Disturbance Rejection: Deep Observation and Comparison 下载免费PDF全文
Jinhua She Kou Miyamoto Qing-Long Han Min Wu Hiroshi Hashimoto Qing-Guo Wang 《IEEE/CAA Journal of Automatica Sinica》2023,10(4):957-968
Active disturbance-rejection methods are effective in estimating and rejecting disturbances in both transient and steady-state responses.This paper presents a deep observation on and a comparison between two of those methods:the generalized extended-state observer(GESO) and the equivalent input disturbance(EID) from assumptions,system configurations,stability conditions,system design,disturbance-rejection performance,and extensibility.A time-domain index is introduced to assess the disturbance-r... 相似文献
1000.