全文获取类型
收费全文 | 351807篇 |
免费 | 11665篇 |
国内免费 | 5320篇 |
专业分类
电工技术 | 10592篇 |
技术理论 | 11篇 |
综合类 | 6839篇 |
化学工业 | 54061篇 |
金属工艺 | 16412篇 |
机械仪表 | 13647篇 |
建筑科学 | 14799篇 |
矿业工程 | 3553篇 |
能源动力 | 9274篇 |
轻工业 | 30635篇 |
水利工程 | 3528篇 |
石油天然气 | 7523篇 |
武器工业 | 694篇 |
无线电 | 44510篇 |
一般工业技术 | 58232篇 |
冶金工业 | 55715篇 |
原子能技术 | 5065篇 |
自动化技术 | 33702篇 |
出版年
2023年 | 2145篇 |
2022年 | 3693篇 |
2021年 | 5489篇 |
2020年 | 4075篇 |
2019年 | 3961篇 |
2018年 | 5222篇 |
2017年 | 5542篇 |
2016年 | 5314篇 |
2015年 | 5709篇 |
2014年 | 7984篇 |
2013年 | 16882篇 |
2012年 | 11892篇 |
2011年 | 14799篇 |
2010年 | 12405篇 |
2009年 | 12973篇 |
2008年 | 13582篇 |
2007年 | 13220篇 |
2006年 | 12916篇 |
2005年 | 11824篇 |
2004年 | 9816篇 |
2003年 | 9371篇 |
2002年 | 9014篇 |
2001年 | 9019篇 |
2000年 | 8580篇 |
1999年 | 9719篇 |
1998年 | 19342篇 |
1997年 | 14068篇 |
1996年 | 11159篇 |
1995年 | 8556篇 |
1994年 | 7413篇 |
1993年 | 6898篇 |
1992年 | 5002篇 |
1991年 | 4698篇 |
1990年 | 4144篇 |
1989年 | 3986篇 |
1988年 | 3812篇 |
1987年 | 3196篇 |
1986年 | 3041篇 |
1985年 | 3578篇 |
1984年 | 3150篇 |
1983年 | 2819篇 |
1982年 | 2627篇 |
1981年 | 2625篇 |
1980年 | 2475篇 |
1979年 | 2302篇 |
1978年 | 2255篇 |
1977年 | 2830篇 |
1976年 | 4204篇 |
1975年 | 1909篇 |
1974年 | 1802篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Wireless Networks - In such mobile platforms as ships and aircraft, the detection and reconnaissance devices are near to the communication facilities. When working at the same time, they will... 相似文献
32.
Ebrahim A. Mahdy Khadega M. Sahbal Hanan H. Beherei Yasser K. Abdel-Monem 《Ceramics International》2021,47(5):6251-6261
A new TiO2-containing bioactive glass and glass-ceramics based on 50SiO2-(45-X)CaO-(XTiO2)-5P2O5 system was designed using a sol–gel technique (where X = 5, 7.5 and 10 wt %). The roles of the crystallization behavior and physicochemical characteristics of the designed glass and glass-ceramics which were played in the introduction of TiO2 substitutions were investigated. Moreover, cell proliferation and differentiation were evaluated against human osteosarcoma cells (Saos-2). The TiO2/CaO replacements led to the formation of a stronger glass structure and thus increased thermal parameters and the chemical stabilization of the designed materials. The FTIR data confirmed the existence of Ti within the glass and glass-ceramics samples, and no remarkable effect on their chemical integrity was observed. The XRD patterns indicated that calcium-containing minerals, including Ca2SiO4,Ca3(PO4)2, Ca(Ti,Si)O5, CaTiSiO5, and Ca15(PO4)2·(SiO4)6 phases were developed as a role of structure/texture under the applied heat-treatment. The results of the cytotoxicity test proved that a safe sample dose is 12–50 μg/ml, at which cell viability is ≥ 85%. The cell differentiation determined by ALP test proved the superiority of glass-ceramics compared with their native glasses. Therefore, the obtained materials could be safely used as novel biocompatible materials for the regeneration of bone tissue. 相似文献
33.
Moustapha Moussa Amudhan Ponrajan Osvaldo H. Campanella Martin R. Okos Mario M. Martinez Bruce R. Hamaker 《International Journal of Food Science & Technology》2022,57(7):4594-4601
Traditional West African pearl millet couscous products are popular; however, their preparation is laborious, time-consuming and energy-demanding, involving agglomeration, steaming, drying and sieving steps. In this study, a process was developed to produce millet couscous using a high pressure, high temperature and low-cost single-screw extruder. The innovation was to directly process the cooked low-moisture extrudate to a couscous product by drying and milling to the appropriate particle size (ranging between 1 and 2 mm). Throughput for the traditional process as prepared for commercial sale is 50 kg per day, but with the same amount of labour, the extrusion process yields ~350 kg per day. A consumer sensory study held in Niamey (Niger) showed that the extruded millet couscous was comparable to traditional couscous, though this was dependent on selection of the proper millet variety. This novel extrusion process could stimulate small- to medium-scale manufacturing of couscous and couscous-type products in West Africa. 相似文献
34.
Chuncheng Wei Zhen Liu Yun Wu Yeqing Liu Heng Zhang Peng Wang Qiyan Sun Lijuan Zhou 《Ceramics International》2021,47(13):18693-18698
Laminated Si3N4/SiCw ceramics were successfully prepared by tape casting and hot-pressing. Its mechanical properties were measured and the impact resistance was discussed. The toughness of the laminated Si3N4/SiCw ceramics was 13.5 MPa m1/2, which was almost 1.6 times that of Si3N4/SiCw composite ceramics, namely 8.5 MPa m1/2. Moreover, the indentation strength of laminated Si3N4/SiCw ceramics was not sensitive to increasing indentation loads and exhibited a rising R-curve behaviour, indicating that the laminated Si3N4/SiCw ceramics had excellent impact resistance. The improved toughness and impact resistance of laminated Si3N4/SiCw ceramics was attributed to the residual stress caused by a thermal expansion coefficient mismatch between the different layers, resulting in crack deflection and bridging of SiC whiskers in the interface layer, thus consuming a large amount of fracture work. 相似文献
35.
36.
Nan Wu Xiaodong Li Mu Zhang Yi Ren Qi Zhu Haijun Peng Hongqiang Ru Xudong Sun 《Journal of the European Ceramic Society》2021,41(4):2898-2907
Refining ceramic microstructures to the nanometric range to minimize light scattering provides an interesting methodology for developing novel optical ceramic materials. In this work, we reported the fabrication and properties of a new nanocomposite optical ceramic of Gd2O3-MgO. The citric acid sol-gel combustion method was adopted to fabricate Gd2O3-MgO nanocomposites with fine-grain sizes, dense microstructures and homogeneous phase domains. Nanopowders with low agglomeration and improved sinterability can be obtained by elaborating Φ values. Further refining of the microstructure of the nanocomposites was achieved by elaborating the hot-pressing conditions. The sample sintered at 65 MPa and 1300 °C showed a quite high hardness value of 14.3 ± 0.2 GPa, a high transmittance of 80.3 %–84.7 % over the 3?6 μm wavelength range, due mainly to its extremely fine-grain size of Gd2O3 and MgO (93 and 78 nm, respectively) and high density. 相似文献
37.
Catalysis Letters - A new zirconium based carbonaceous solid acid catalyst Zr@CC-PA with both Lewis and Bronsted acidic sites was prepared by simultaneous carbonization and phosphonation of glucose... 相似文献
38.
Material encapsulation is a relatively new technique for coating a micro/nanosize particle or droplet with polymeric or inorganic shell. Encapsulation technology has many applications in various fields including drug delivery, cosmetic, agriculture, thermal energy storage, textile, and self-healing polymers. Poly(methyl methacrylate) (PMMA) is widely used as shell material in encapsulation due to its high chemical stability, biocompatibility, nontoxicity, and good mechanical properties. The main approach for micro/nanoencapsulation of materials using PMMA as shell comprises emulsion-based techniques such as emulsion polymerization and solvent evaporation from oil-in-water emulsion. In the present review, we first focus on the encapsulation techniques of liquid materials with PMMA shell by analyzing the effective processing parameters influencing the preparation of PMMA micro/nanocapsules. We then describe the morphology of PMMA capsules in emulsion systems according to thermodynamic relations. The techniques to investigation of mechanical properties of capsule shell and the release mechanisms of core material from PMMA capsules were also investigated. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48039. 相似文献
39.
Shanshan Li Bing Zhang Xuxiang Feng Yewei Wu 《International journal of remote sensing》2019,40(14):5635-5650
Feature-based methods have been developed in the past decades for the registration of optical satellite images. However, it is still a challenging problem to handle well the registration between medium and high spatial resolution images due to the large difference of the spatial structural features and local details for the same objects. In this study, an automated co-registration technique is proposed that integrates an improved SIFT (I-SIFT) and a novel matching strategy called spatial consistency constraints (SCC) to cope with the large difference in spatial resolutions between the image pair. Three constraints on angle, distance, and ratio are introduced to re the initial matching features obtained by I-SIFT. Three groups of experiments were conducted to validate the effectiveness of the proposed method. The experiments used high resolution multispectral and panoramic SPOT 5/6 images and Landsat 5/8 orthorectification images. Experimental results show that the registration error lies in about 1 pixel of high-resolution images and demonstrate that the proposed I-SIFT-SCC approach is suitable for fine registration of optical satellite images from medium spatial resolution to high spatial resolution with resolution ratio up to 6. 相似文献
40.
Fluorescence‐Activated Cell Sorters: Standing Surface Acoustic Wave (SSAW)‐Based Fluorescence‐Activated Cell Sorter (Small 40/2018)
下载免费PDF全文
![点击此处可从《Small (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)