全文获取类型
收费全文 | 115627篇 |
免费 | 8274篇 |
国内免费 | 3233篇 |
专业分类
电工技术 | 5088篇 |
技术理论 | 5篇 |
综合类 | 4256篇 |
化学工业 | 19854篇 |
金属工艺 | 5590篇 |
机械仪表 | 6580篇 |
建筑科学 | 6443篇 |
矿业工程 | 1558篇 |
能源动力 | 3940篇 |
轻工业 | 7788篇 |
水利工程 | 1313篇 |
石油天然气 | 3423篇 |
武器工业 | 505篇 |
无线电 | 17244篇 |
一般工业技术 | 18487篇 |
冶金工业 | 8408篇 |
原子能技术 | 1395篇 |
自动化技术 | 15257篇 |
出版年
2024年 | 263篇 |
2023年 | 1543篇 |
2022年 | 2328篇 |
2021年 | 3954篇 |
2020年 | 2797篇 |
2019年 | 2495篇 |
2018年 | 3030篇 |
2017年 | 3234篇 |
2016年 | 3315篇 |
2015年 | 3644篇 |
2014年 | 4860篇 |
2013年 | 6959篇 |
2012年 | 6990篇 |
2011年 | 7935篇 |
2010年 | 6627篇 |
2009年 | 6547篇 |
2008年 | 6418篇 |
2007年 | 5800篇 |
2006年 | 5604篇 |
2005年 | 4776篇 |
2004年 | 3868篇 |
2003年 | 3519篇 |
2002年 | 3552篇 |
2001年 | 2988篇 |
2000年 | 2672篇 |
1999年 | 2766篇 |
1998年 | 3357篇 |
1997年 | 2466篇 |
1996年 | 2210篇 |
1995年 | 1779篇 |
1994年 | 1394篇 |
1993年 | 1172篇 |
1992年 | 923篇 |
1991年 | 818篇 |
1990年 | 632篇 |
1989年 | 581篇 |
1988年 | 477篇 |
1987年 | 367篇 |
1986年 | 317篇 |
1985年 | 284篇 |
1984年 | 232篇 |
1983年 | 169篇 |
1982年 | 182篇 |
1981年 | 146篇 |
1980年 | 145篇 |
1979年 | 110篇 |
1978年 | 96篇 |
1977年 | 123篇 |
1976年 | 158篇 |
1975年 | 80篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
Video transmission over IEEE 802.11e wireless networks still shows poor performance for large bandwidth demand and frequently changed environments. Thus, several enhancements of IEEE 802.11e were proposed. On the other hand, big frames and simultaneous sending of adjacent frames always cause packet dropping for buffer overflow. In the past, we proposed an IEEE 802.11e enhancement named DFAA and a content aware mechanism to solve the above problems. The motivation of this paper is to find a proper way to integrate these two mechanisms. A DFAA enhancement (DFAA-E) is proposed to make up the insufficiency of content aware mechanism. Experiments results show that the combination of DFAA-E and content aware mechanism improves the video decoded quality greatly. And its performance can be further enhanced by selecting the suitable settings of certain parameters. 相似文献
113.
Yang Yang Yibei Zhou Juan Ren Qiaoji Zheng Kwok Ho Lam Dunmin Lin 《Journal of the European Ceramic Society》2018,38(2):557-566
Perovskite ferroelectrics possess the fascinating piezoelectric properties near a morphotropic phase boundary, attributing to a low energy barrier that the results in structural instability and easy polarization rotation. In this work, a new lead-free system of (1-x)BaTiO3-xCaHfO3 was designed, and characterized by a coexistence of ferroelectric rhombohedral-orthorhombic-tetragonal (R-O-T) phases. With the increase amount of CaHfO3 (x), a stable coexistence region of three ferroelectric phases (R-O-T) exists at 0.06 ≤ x ≤ 0.08. Both large piezoelectric coefficient (d33~400 pC/N), inverse piezoelectric coefficient (d33*~547 pm/V) and planar electromechanical coupling factor (kp~58.2%) can be achieved for the composition with x = 0.08 near the coexistence of three ferroelectric phases. Our results show that the materials with the composition located at a region where the three ferroelectric R-O-T phases coexist would have the lowest energy barrier and thus greatly promote the polarization rotation, resulting in a strong piezoelectric response. 相似文献
114.
115.
Inam Ridha Ali Basiri Sudhakar Godeshala Md Zubair Ebne Rafique Deepanjan Ghosh Jason Williams Nikhilesh Chawla Jung Keun Lee Jacquelyn Kilbourne Yu Yao Kaushal Rege 《Advanced functional materials》2021,31(6):2007811
Poor strength, infection, leakage, long procedure times, and inflammation limit the efficacy of common tissue sealing devices in surgeries and trauma. Light-activated sealing is attractive for tissue sealing and repair, and can be facilitated by the generation of local heat following absorption of nonionizing laser energy by chromophores. Here, the inherent ability of biomaterials is exploited to absorb nonionizing, mid-infrared (midIR) light in order to engender rapid photothermal sealing and repair of soft tissue wounds. In this approach, the biomaterial simultaneously acts as a photothermal convertor as well as a biosealant, which dispenses the need for exogeneous light-absorbing nanoparticles or dyes. Biomechanical recovery, mathematical modeling, histopathology analyses, tissue strain mapping using digital imaging correlation, and visualization of the biosealant-tissue interface using hyperspectral imaging indicate superior performance of midIR sealing in live mice compared to conventional sutures and glue. The midIR-biosealant approach demonstrates rapid sealing of soft tissues, improves cosmesis, lowers potential for scarring, obviates safety concerns because of the nonionizing light used, and allows adoption of a wide diversity of biomaterials. Taken together, the studies demonstrate a novel advance both in biomaterials for surgical sealing along with the use of nonionizing midIR light, with high potential for clinical translation. 相似文献
116.
117.
Youngseok Lee Cheolmin Park Nagarajan Balaji Youn-Jung Lee Vinh Ai Dao 《Israel journal of chemistry》2015,55(10):1050-1063
Over the past few decades, crystalline silicon solar cells have been extensively studied due to their high efficiency, high reliability, and low cost. In addition, these types of cells lead the industry and account for more than half of the market. For the foreseeable future, Si will still be a critical material for photovoltaic devices in the solar cell industry. In this paper, we discuss key issues, cell concepts, and the status of recent high-efficiency crystalline silicon solar cells. 相似文献
118.
Since researchers began studying the mechanism of flavonoids’ anticancer activity, little attention has been focused on the modulation of redox state in cells as a potential chemotherapeutic strategy. However, recent studies have begun identifying that the anticancer effect of flavonoids occurs both in their antioxidative activity which scavenges ROS and their prooxidative activity which generates ROS. Against this backdrop, this study attempts to achieve a comprehensive analysis of the individual and separate study findings regarding flavonoids’ modulation of redox state in cancer cells. It focuses on the mechanism behind the anticancer effect, and mostly on the modulation of redox potential by flavonoids such as quercetin, hesperetin, apigenin, genistein, epigallocatechin-3-gallate (EGCG), luteolin and kaempferol in both in vitro and animal models. In addition, the clinical applications of and bioavailability of flavonoids were reviewed to help build a treatment strategy based on flavonoids’ prooxidative potential. 相似文献
119.
Ha-Nul Lee Joo-Hee Choi Ji-Yeon Park Jae-Hun Ahn Da Eun Jang Jae Gun Shim Jong-Hwan Park Young-Min Kim 《Food science and biotechnology》2021,30(4):583
Vegetable soup (VS), a plant-based functional food, has been used as a traditional folk medicine and is attracting attention for its ability to enhance the immune response. β-Glucan, a well-established and effective immunomodulator, has synergistic effects when used in combination with some bioactive compounds. In the present study, we aimed to evaluate the synergistic immunomodulatory effects of the combination of VS and β-glucan on macrophage-mediated immune responses. β-Glucan was demonstrated to synergistically enhance the VS-stimulated immune response, including the production of interleukin-6, tumor necrosis factor-α, and nitric oxide, mainly through the mitogen-activated protein kinase pathway in macrophages. In addition, this combination has the potential for further development in functional foods with immune-enhancing activity.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10068-021-00888-x. 相似文献
120.
苏6井区下石盒子组高分辨率层序地层学特征 总被引:1,自引:0,他引:1
以高分辨率层序地层学理论和技术方法为指导,在苏里格气田苏6井区地表露头、钻井岩心、测井、地震资料综合研究的基础上,通过基准面旋回结构、叠加样式的沉积动力学分析,将该井区下石盒子组划分为2个长期、5个中期和14个短期旋回层序;并较为详细地讨论了各期旋回层序特征;建立了以长期旋回层序界面和最大洪泛面为等时年代地层框架,以中期旋回层序为等时地层单元的高分辨率层序地层格架;通过分析,认为下石盒子组盒8下段天然气储、盖条件最为有利;有利于储层发育的河道砂体主要出现在长、中期上升半旋回的中、下部,层序界面上相当短期旋回级别的单河道砂体是下石盒子组天然气勘探开发的主要目标。 相似文献