全文获取类型
收费全文 | 56588篇 |
免费 | 16359篇 |
国内免费 | 947篇 |
专业分类
电工技术 | 1678篇 |
技术理论 | 1篇 |
综合类 | 1518篇 |
化学工业 | 19110篇 |
金属工艺 | 1254篇 |
机械仪表 | 1989篇 |
建筑科学 | 3152篇 |
矿业工程 | 531篇 |
能源动力 | 1634篇 |
轻工业 | 8203篇 |
水利工程 | 674篇 |
石油天然气 | 1213篇 |
武器工业 | 190篇 |
无线电 | 9502篇 |
一般工业技术 | 13637篇 |
冶金工业 | 1811篇 |
原子能技术 | 292篇 |
自动化技术 | 7505篇 |
出版年
2024年 | 32篇 |
2023年 | 303篇 |
2022年 | 444篇 |
2021年 | 961篇 |
2020年 | 2026篇 |
2019年 | 3628篇 |
2018年 | 3624篇 |
2017年 | 3963篇 |
2016年 | 4429篇 |
2015年 | 4661篇 |
2014年 | 4839篇 |
2013年 | 6203篇 |
2012年 | 4033篇 |
2011年 | 3799篇 |
2010年 | 3921篇 |
2009年 | 3805篇 |
2008年 | 3294篇 |
2007年 | 3020篇 |
2006年 | 2716篇 |
2005年 | 2311篇 |
2004年 | 2042篇 |
2003年 | 1954篇 |
2002年 | 1687篇 |
2001年 | 1320篇 |
2000年 | 862篇 |
1999年 | 648篇 |
1998年 | 606篇 |
1997年 | 514篇 |
1996年 | 424篇 |
1995年 | 334篇 |
1994年 | 296篇 |
1993年 | 232篇 |
1992年 | 166篇 |
1991年 | 134篇 |
1990年 | 118篇 |
1989年 | 92篇 |
1988年 | 103篇 |
1987年 | 46篇 |
1986年 | 50篇 |
1985年 | 34篇 |
1984年 | 25篇 |
1983年 | 21篇 |
1982年 | 27篇 |
1981年 | 16篇 |
1980年 | 19篇 |
1979年 | 24篇 |
1978年 | 17篇 |
1977年 | 13篇 |
1976年 | 10篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Niu Hao Yang Dan-Lei Pu Yuan Wang Dan Wang Jie-Xin 《Journal of Materials Science》2022,57(10):5788-5804
Journal of Materials Science - Nanocomposites have been used in various industries due to their excellent properties. For some of them, high filler content (over 50 wt%) is beneficial to improving... 相似文献
2.
3.
Keran Su Kim Huey Ee Jingcan Sun Shao Quan Liu Benjamin Lassabliere Ulrich Feiter Yunle Huang Rui Min Vivian Goh Aileen Pua Bin Yu 《International Journal of Food Science & Technology》2022,57(3):1666-1678
The structural diversity of polyphenols and the inherent limitations of current extraction techniques pose a challenge to extract polyphenols using a simple and green method. Hence, in this study, a method was developed to simultaneously fractionate multiple classes of polyphenols by only varying ethanol-water solutions. Honeybush tea, which is rich in polyphenols, was selected as a model for this study. Solvent extraction followed by solid-phase extraction (SPE) was developed to obtain a polyphenol-rich fraction from six honeybush samples. Based on a gradient elution programme (10%, 30%, 50%, 70% and 90% (v/v) ethanol-water solution) of SPE, the Strata X cartridge showed a better recovery of most targeted polyphenols under 0.9 mL of the drying volume and 1 mL min−1 of the dispensing speed. The elution programme for fractionating most polyphenols was as follows: single elution with 50% ethanol, followed by twice elution with 70% ethanol. The antioxidant capacity was used to analyse the differences among the polyphenol-rich fractions from six honeybush samples. Principal component analysis (PCA) revealed that unfermented C. genistoides (GG) has the greatest antioxidant capacity among the honeybush species studied. Additionally, mangiferin, isomangiferin and vicenin-2 were the main contributors to the antioxidant capacity in six honeybush fractions according to the correlation study. 相似文献
4.
Chu Shipeng Zhang Tuqiao Zhou Xinhong Yu Tingchao Shao Yu 《Water Resources Management》2022,36(2):491-505
Water Resources Management - Real-time modeling of a water distribution system (WDS) is a critical step for the control and operation of such systems. The nodal water demand, as the most important... 相似文献
5.
Knowledge and Information Systems - Many data mining algorithms cannot handle incomplete datasets where some data samples are missing attribute values. To solve this problem, missing value... 相似文献
6.
Meiling Shi Leqi Yao Junfeng Xu Chao Liang Yan Dong Qiyue Shao 《Journal of the American Ceramic Society》2021,104(7):3279-3288
Phosphors-converted LEDs (pc-LEDs) are excellent artificial light sources for indoor plant cultivation, in which the far-red-emitting component (700−780 nm) plays an important role in regulating the photomorphogenesis of plants. Accordingly, highly efficient and thermally stable far-red-emitting phosphors are indispensable for developing high-performance plant cultivation pc-LEDs. Herein, far-red-emitting YAl3(BO3)4:Cr3+ (YAB:Cr3+) phosphors were synthesized by solid-state reaction, and their photoluminescence characteristics, thermal quenching, quantum yield (QY), and application in pc-LEDs were systematically investigated. The YAB:Cr3+ phosphor has an intense broadband absorption to the blue light, simultaneously exhibiting the sharp-line 2E emission and the broadband 4 T2 emission of Cr3+ with a QY of ~86.7%. The far-red broadband emissions of YAB:Cr3+ centered at ~735 nm show a high resemblance to the active-state (PFR) absorption of plant phytochrome. Moreover, the YAB:Cr3+ phosphor shows the thermally enhanced luminescence at temperatures of 303−393 K and the near-zero thermal quenching up to 423 K. The anomalous thermal enhancement is attributed to the temperature-dependent repopulation between 2E and 4 T2 states. Finally, a pc-LED device was fabricated with the YAB:Cr3+ phosphor and blue chip, exhibiting the light out power of ~50.6 mW and energy conversion efficiency of ~17.4% at 100 mA drive current, respectively. The exceptional PL features including suitable excitation/emission wavelengths, suppressed thermal quenching and high QY make YAB:Cr3+ phosphors very promising for applications in plant growth pc-LEDs. 相似文献
7.
Karolina Storesund Francine Amon Anne Steen‐Hansen Shayesteh Haghighatpanah Ida Larsson 《火与材料》2021,45(1):181-190
The aim of this exploratory study has been to investigate the fire properties and environmental aspects of different upholstery material combinations, mainly for domestic applications. An analysis of the sustainability and circularity of selected textiles, along with lifecycle assessment, is used to qualitatively evaluate materials from an environmental perspective. The cone calorimeter was the primary tool used to screen 20 different material combinations from a fire performance perspective. It was found that textile covers of conventional fibres such as wool, cotton and polyester, can be improved by blending them with fire resistant speciality fibres. A new three‐dimensional web structure has been examined as an alternative padding material, showing preliminary promising fire properties with regard to ignition time, heat release rates and smoke production. 相似文献
8.
Xiaoyu Ji Hongfei Gao Shuai Zhang Yan Jia Ming-Sheng Ji Xingui Zhou Changwei Shao 《Journal of the European Ceramic Society》2021,41(10):5016-5025
Given the superior thermal stability and electromagnetic features, continuous Si–B–(C)–N ceramic fibers have displayed great potential to fulfill the increasing demand for the high-temperature structural and functional materials. Manufacture of such ceramic fibers depends heavily upon the design of processable polymer precursors. Herein, a class of polyborosilazanes (PBSZs) with high spinnability were created through a facile one-pot synthesis. The trade-off between spinnability and ceramic yield of PBSZs was overcome by using heptamethyldisilazane and hexamethyldisilazane as the co-condensing agents to polymerize silicon and boron chloride monomers. The optimal PBSZs can fabricate continuous Si–B–C–N fibers with homogeneous diameter of 7.9 ± 0.5 μm and high ceramic yield of 80 wt%. Experimental characterization and quantum chemical computation revealed the mechanistic pictures of the impact of pendant groups on the polycondensation, melt spinning, and pyrolyzing process. These insights improve our understanding of spinnable pre-ceramic polymers for exploiting high-performance nitride ceramic fibers. 相似文献
9.
10.
Qi Shuang Xiang WenXin Cai LiXun Liu XiaoKun Shao ChunBing Ning FangMao Shi JinHua Yu WeiWei 《中国科学:技术科学(英文版)》2021,64(12):2577-2585
Science China Technological Sciences - Mixed-mode I-II crack-based fatigue crack propagation (FCPI-II) usually occurs in engineering structures; however, no theoretical formula or effective... 相似文献