全文获取类型
收费全文 | 55656篇 |
免费 | 7072篇 |
国内免费 | 4211篇 |
专业分类
电工技术 | 3664篇 |
技术理论 | 7篇 |
综合类 | 6357篇 |
化学工业 | 5314篇 |
金属工艺 | 2233篇 |
机械仪表 | 2351篇 |
建筑科学 | 10524篇 |
矿业工程 | 4093篇 |
能源动力 | 1496篇 |
轻工业 | 3453篇 |
水利工程 | 2904篇 |
石油天然气 | 3750篇 |
武器工业 | 276篇 |
无线电 | 3915篇 |
一般工业技术 | 4530篇 |
冶金工业 | 3192篇 |
原子能技术 | 550篇 |
自动化技术 | 8330篇 |
出版年
2024年 | 261篇 |
2023年 | 1625篇 |
2022年 | 2745篇 |
2021年 | 2986篇 |
2020年 | 2604篇 |
2019年 | 2016篇 |
2018年 | 1538篇 |
2017年 | 1594篇 |
2016年 | 1677篇 |
2015年 | 1816篇 |
2014年 | 3222篇 |
2013年 | 2812篇 |
2012年 | 3657篇 |
2011年 | 3785篇 |
2010年 | 3004篇 |
2009年 | 3176篇 |
2008年 | 2811篇 |
2007年 | 3646篇 |
2006年 | 3346篇 |
2005年 | 3024篇 |
2004年 | 2449篇 |
2003年 | 2268篇 |
2002年 | 1905篇 |
2001年 | 1602篇 |
2000年 | 1375篇 |
1999年 | 1092篇 |
1998年 | 763篇 |
1997年 | 670篇 |
1996年 | 605篇 |
1995年 | 521篇 |
1994年 | 401篇 |
1993年 | 339篇 |
1992年 | 266篇 |
1991年 | 176篇 |
1990年 | 193篇 |
1989年 | 173篇 |
1988年 | 136篇 |
1987年 | 104篇 |
1986年 | 77篇 |
1985年 | 66篇 |
1984年 | 62篇 |
1983年 | 26篇 |
1982年 | 27篇 |
1981年 | 33篇 |
1980年 | 33篇 |
1979年 | 41篇 |
1977年 | 18篇 |
1976年 | 21篇 |
1975年 | 22篇 |
1974年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
81.
82.
《岩石力学与岩土工程学报(英文版)》2020,12(6):1214-1225
With rapid development of infrastructures like tunnels and open excavations in Shanghai, investigations on deeper soils have become critically important. Most of the existing laboratory works were focused on the clayey strata up to Layer 6 in Shanghai, i.e. at depth of up to 40 m. In this paper, Layers 7, 9, and 11, which were mostly formed of sandy soils at depth of up to 150 m, were experimentally investigated with respect to physico-mechanical behaviors. The stress–strain behaviors were analyzed by the consolidated drained/undrained (CD/CU) triaxial tests under monotonic loading. One-dimensional (1D) oedometer tests were performed to investigate the consolidation properties of the sandy soils. Specimens were prepared at three different relative densities for each layer. Also, the micro-images and particle size analyzers were used to analyze the shape and size of the sand grains. The influences of grain size, density, and angularity on the stress–strain behaviors and compressibility were also studied. Compared to the other layers, Layer 11 had the smallest mean grain size (D50), highest compressibility, and lowest shear strength. In contrast, Layer 9 had the largest mean grain size, lowest compressibility, and highest shear strength. Layer 7 was of intermediate mean grain size, exhibiting more compressibility and less shear strength than that of Layer 9. Also, the critical state parameters and maximum dilatancy rate of different layers were discussed. 相似文献
83.
Zhuang CHENG Jianfeng WANG Matthew Richard COOP Guanlin YE 《Frontiers of Structural and Civil Engineering》2020,14(2):357
The development of a miniature triaxial apparatus is presented. In conjunction with an X-ray micro-tomography (termed as X-ray μCT hereafter) facility and advanced image processing techniques, this apparatus can be used for in situ investigation of the micro-scale mechanical behavior of granular soils under shear. The apparatus allows for triaxial testing of a miniature dry sample with a size of (diameter height). In situ triaxial testing of a 0.4–0.8 mm Leighton Buzzard sand (LBS) under a constant confining pressure of 500 kPa is presented. The evolutions of local porosities (i.e., the porosities of regions associated with individual particles), particle kinematics (i.e., particle translation and particle rotation) of the sample during the shear are quantitatively studied using image processing and analysis techniques. Meanwhile, a novel method is presented to quantify the volumetric strain distribution of the sample based on the results of local porosities and particle tracking. It is found that the sample, with nearly homogenous initial local porosities, starts to exhibit obvious inhomogeneity of local porosities and localization of particle kinematics and volumetric strain around the peak of deviatoric stress. In the post-peak shear stage, large local porosities and volumetric dilation mainly occur in a localized band. The developed triaxial apparatus, in its combined use of X-ray μCT imaging techniques, is a powerful tool to investigate the micro-scale mechanical behavior of granular soils. 相似文献
84.
以某斜齿轮为研究对象,分析齿轮剃齿加工成形原理,运用MASTA对斜齿轮剃齿加工成形进行仿真分析。仿真结果表明:在斜齿轮径向剃齿成形加工过程中,剃齿刀做径向进给运动和沿自轴旋转运动,对旋转的加工齿轮进行剃齿加工成形;不同半径、齿宽、齿高下加工斜齿轮和剃齿刀齿面变化不同;剃齿加工成形的斜齿轮形状与设计斜齿轮形状基本一致。该研究为斜齿轮加工成形、成形质量和加工效率的提高提供理论依据。 相似文献
85.
86.
Isocyanate and amine solution are microencapsulated, respectively, via in situ polymerization to realize the self-healing function in epoxy matrix. First, the isophorone diisocyanate (IPDI) microcapsules prepared with different core/shell ratios, emulsifier dosages and emulsification rates are characterized by field emission scanning electron microscope (FE-SEM). They exhibit integral spherical shape when the core/shell ratio is 3:1 and emulsifier concentration is 2.52 wt %, and the diameter of IPDI microcapsules ranged from 2.66 μm to 11.25 μm is manufactured by adjusting emulsification rate over the range of 3000–9000 rpm. Besides, during the microencapsulation of polyaspartic acid ester (PAE), urea, tung oil, as well as aqueous isocyanate are proposed to improve the stability of PAE emulsion. SEM and FTIR results reveal that aqueous isocyanate can react with partial PAE and form polyurea (PU) layer to take protection effectively. Further, IPDI-PAE dual microcapsules are incorporated into epoxy coatings, the self-healing and anticorrosion performance of coatings with various amounts of microcapsules are investigated systematically. It was found that the degree of repair and anticorrosion are increased with increasing microcapsules loading, and the appropriate amount of microcapsules addition is 15 wt %, which corresponding to 93% repair efficiency. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48478. 相似文献
87.
Yali Liu Peng Li Rong Qian Tianyu Sun Fangzhi Fang Zonghua Wang 《Drug development and industrial pharmacy》2018,44(8):1317-1327
88.
Intercalation structure and toughening mechanism of graphene/urea‐formaldehyde nanocomposites prepared via in situ polymerization 下载免费PDF全文
Based on the industrialized graphene (GN) product, a series of graphene/urea‐formaldehyde nanocomposites were synthesized via in situ polymerization by incorporation of silicon coupling agent with terminal amino groups (SA) as the compatibilizer. The results showed that addition of SA coupling agent led to much more efficient grafting of UF molecules on the GN surface with high layer thickness by formation of hydrogen bonding, and thus complete exfoliation and uniform dispersion of GN were achieved for the composites. Compared with neat UF, the addition of 1.0 wt% GN resulted in a roughly 25% increase in tensile strength and 12% increase in impact strength; meanwhile the impact fracture surfaces of the composite showed obvious ductile fracture characteristics, indicating the reinforcing and toughening effect of GN on the UF matrix. With increasing GN content, the storage modulus, glass transition temperature and crosslinking density of UF increased, while the tan δmax decreased, suggesting that a double crosslinking network structure with GN centered crosslinking point and chemical crosslinking point of UF molecular chains formed, leading to improvement in the stiffness of the composites. The present work showed promising potential for developing high performance UF resin on an industrial scale. © 2017 Society of Chemical Industry 相似文献
89.
90.
Siegrid De Baere Thomas De Mil Gunther Antonissen Mathias Devreese Siska Croubels 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2018,35(9):1728-1738
Mycotoxin binders are feed additives which are mixed in the feed to adsorb mycotoxins and thereby reducing their toxic effects on animals. Interactions with orally administered veterinary medicinal products, such as antimicrobials or coccidiostats, have been reported previously. This paper describes an in vitro model to screen the interaction between mycotoxin binders and veterinary drugs with respect to the non-specific binding of drugs. It is designed as a static setup using a single concentration of drug and binder in a feed-containing or a feed-plus-mycotoxin-containing matrix, buffered at different pH values. The model was applied to two frequently used antimicrobials in veterinary medicine, doxycycline (DOX) and tylosin (TYL), one major mycotoxin, aflatoxin B1 (AFB1), and four mycotoxin binders. Proportions of feed, DOX or TYL, AFB1, and binder are equivalent to the in vivo situation for broiler chickens, while pH and volume of the buffer are representative of the gastrointestinal tract of chickens. A substantial binding of DOX (~ 88%) and TYL (~ 66%) to the feed-matrix was observed. For the mycotoxin binders, similar results were obtained for DOX and TYL; more specifically up to an inclusion rate of 20 g binder/kg feed, no significant binding was demonstrated, determined as the free concentration of DOX and TYL. A single exception was noticed for TYL and one specific bentonite-based mycotoxin binder, for which no significant interaction could be demonstrated up to 10 g binder/kg but there was an effect at 20 g/kg. In all cases, there was no competition between the tested drugs DOX or TYL and the mycotoxin AFB1 for binding to the bentonite-based mycotoxin binder. 相似文献