全文获取类型
收费全文 | 91040篇 |
免费 | 9332篇 |
国内免费 | 5176篇 |
专业分类
电工技术 | 6760篇 |
技术理论 | 1篇 |
综合类 | 7219篇 |
化学工业 | 13375篇 |
金属工艺 | 5744篇 |
机械仪表 | 6444篇 |
建筑科学 | 7518篇 |
矿业工程 | 3118篇 |
能源动力 | 2429篇 |
轻工业 | 6387篇 |
水利工程 | 2155篇 |
石油天然气 | 4666篇 |
武器工业 | 967篇 |
无线电 | 10840篇 |
一般工业技术 | 9650篇 |
冶金工业 | 3718篇 |
原子能技术 | 1093篇 |
自动化技术 | 13464篇 |
出版年
2024年 | 186篇 |
2023年 | 1256篇 |
2022年 | 2558篇 |
2021年 | 3711篇 |
2020年 | 2842篇 |
2019年 | 2245篇 |
2018年 | 2530篇 |
2017年 | 2817篇 |
2016年 | 2594篇 |
2015年 | 4037篇 |
2014年 | 4891篇 |
2013年 | 5845篇 |
2012年 | 6792篇 |
2011年 | 7149篇 |
2010年 | 6623篇 |
2009年 | 6578篇 |
2008年 | 6259篇 |
2007年 | 6171篇 |
2006年 | 5683篇 |
2005年 | 4833篇 |
2004年 | 3254篇 |
2003年 | 2656篇 |
2002年 | 2468篇 |
2001年 | 2154篇 |
2000年 | 1799篇 |
1999年 | 1640篇 |
1998年 | 1069篇 |
1997年 | 953篇 |
1996年 | 830篇 |
1995年 | 691篇 |
1994年 | 569篇 |
1993年 | 415篇 |
1992年 | 316篇 |
1991年 | 254篇 |
1990年 | 207篇 |
1989年 | 180篇 |
1988年 | 137篇 |
1987年 | 83篇 |
1986年 | 71篇 |
1985年 | 32篇 |
1984年 | 29篇 |
1983年 | 14篇 |
1982年 | 22篇 |
1981年 | 15篇 |
1980年 | 23篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1976年 | 7篇 |
1959年 | 7篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
11.
Feng Yingrui Hu Kang Zhang Min Ding Wei Kong Xiangkai Sheng Zhigao Liu Qiangchun 《Journal of Materials Science》2022,57(1):204-216
Journal of Materials Science - Rationally designing microwave absorption materials with highly efficient and tunable bandwidth is in great demand but remains a huge challenge. In this study,... 相似文献
12.
13.
Sha Liu JianHui Xiao YaPing Feng MianLing Zhang Ying Li Jin Tu LiYa Niu 《International Journal of Food Science & Technology》2022,57(3):1791-1803
Konjac glucomannan/sodium alginate composite edible boba (KGM/SA-boba) with good taste is very popular in China, and it is an outstanding carrier for health potential ingredients. In this work, KGM/SA-boba were fortified with 0.25, 0.50, 0.75 and 1.00% purple sweet potato anthocyanin (PSPA), then characterised by the water distribution, texture, microstructure, in vitro release property of PSPA and antioxidant capacity. LF-NMR analysis demonstrated that the free water of KGM/SA-boba could transfer to tightly bound water with the addition of PSPA that made it with better water-binding ability, higher springiness and lower hardness. And the results of SEM and rheology showed that PSPA could stabilise the microstructure of KGM/SA-boba by forming more amorphous regions and hydrogen bonds proved by the results of DSC and FT-IR. Furthermore, 50% of PSPA in PSPA-fortified KGM/SA-boba can be released at the first hour in a simulated gastrointestinal environment. And the scavenging capacity of DPPH and ABTS of the PSPA-fortified KGM/SA-boba after digestion was higher than that of PSPA alone. Generally, PSPA could improve the texture while KGM/SA-boba in turn would make PSPA more stable in the gastrointestinal digestive system. 相似文献
14.
Fangqing Wei Xiaoqi Zhang Jiayun Song Feng Yang 《International Transactions in Operational Research》2023,30(1):369-393
Evaluating the efficiency of healthcare services accurately can help in analyzing the rationality of inputs and outputs in such services. Considering the consistency and equity of assessment criteria, this study conducts the stochastic multicriteria acceptability analysis (SMAA-2) with a directional distance function to evaluate the efficiency of healthcare services in 31 provincial administrative regions of mainland China, as observed in 2018. We use SMAA-DDF to explore all the projection directions to the efficient frontier instead of a certain projection direction. We measure the maximum and average efficiencies for each of the 31 provincial healthcare services. Our empirical findings show that only seven provinces achieve optimal healthcare service efficiency; the eastern area performed the best, followed by the central, western, and northeast areas. Furthermore, the path along the projection directions is provided to help inefficient provinces improve their efficiency and obtain the best possible positions. 相似文献
16.
Baohua Yuan Lili Wei Lixia Yang Liangjiu Bai Huawei Yang Donglei Wei Feng Wang Wenxiang Wang Hou Chen 《Journal of the American Ceramic Society》2022,105(2):801-805
Solar steam generation has attracted considerable interest due to its easy accessibility and sustainability. However, dye molecules were gradually concentrated on bulk water or the surface of solar absorbers during the disposal of dye wastewater. Herein, LaB6/g-C3N4 composites were immobilized on porous cotton cloth, served as a solar absorber resistant to dye clogging. The optimal solar absorber possessed solar harvesting of 92.3% and showed great application potential in the field of the treatment of dye wastewater. This study presented a new approach for the treatment of dye wastewater. 相似文献
17.
Fenqi Du Dongmei Yang Yue Sun Yang Jiao Feng Teng Haibo Fan 《Ceramics International》2021,47(4):4963-4971
Ultrawide band gap semiconductor materials have attracted considerable attention in recent years owing to their great potential in the photocatalytic field. In this study, Zn-doped Ga2O3 nanofibers with various concentrations were synthesized via electrospinning; they exhibited a superior photocatalytic degradation performance of rhodamine B dye compared to that of undoped Ga2O3 nanofibers. The Zn dopant replaced Ga sites via replacement doping, which could increase the concentration of oxygen vacancies and lead to enhanced photocatalytic properties. When the Zn concentration increased, a Ga2O3/ZnGa2O4 hybrid structure formed, which could further enhance the photocatalytic performance. The separation of photogenerated carriers due to Zn doping and heterojunctions were the primary causes of the enhanced photocatalytic performance. This study provides experimental data for the fabrication of high-performance photocatalysts based on Ga2O3 nanomaterials. 相似文献
18.
19.
Tao TIAN Chao-lan ZHANG Feng ZHU Shan-xin YUAN Ying GUO Sheng-guo XUE 《中国有色金属学会会刊》2021,31(5):1484-1495
A column experiment was conducted to investigate the effect of phosphogypsum (PG) on the saline- alkalinity, and aggregate stability of bauxite residue. Results showed that: with increasing leaching time, the concentrations of saline-alkali ions decreased while the concentration increased in bauxite residue leachate; compared with CK (control group) treatment, pH, electric conductivity (EC), exchangeable sodium percentage (ESP), sodium absorption ratio (SAR), and exchangeable Na+ content of bauxite residue were reduced following PG treatment; average particle sizes in aggregates following CK and PG treatments were determined to be 155 and 193 nm, respectively. SR-μCT test results also confirmed that bauxite residue following PG treatment acquired larger aggregates and larger pore diameter. These results indicate that the PG treatment could significantly modulate the saline-alkalinity, and simultaneously enhance aggregate stability of bauxite residue, which provides a facile approach to reclaim bauxite residue disposal areas. 相似文献
20.
Lun Feng William G. Fahrenholtz Gregory E. Hilmas Frédéric Monteverde 《Journal of the European Ceramic Society》2021,41(1):92-100
Dense high-entropy (Hf,Zr,Ti,Ta,Nb)B2 ceramics with Nb contents ranging from 0 to 20 at% were produced by a two-step spark plasma sintering process. X-ray diffraction indicated that a single-phase with hexagonal structure was detected in the composition without Nb. In contrast, two phases with the same hexagonal structure, but slightly different lattice parameters were present in compositions containing Nb. The addition of Nb resulted in the presence of a Nb-rich second phase and the amount of the second phase increased as the Nb content increased. The relative densities were all >99.5 %, but decreased from ~100 % to ~99.5 % as the Nb content increased from 0 to 20 at%. The average grain size decreased from 13.9 ± 5.5 μm for the composition without Nb additions to 5.2 ± 2.0 μm for the composition containing 20 at% Nb. The reduction of grain size with increasing Nb content was due to the suppression of grain growth by the Nb-rich second phase. The addition of Nb increased Young’s modulus and Vickers hardness, but decreased shear modulus. While some Nb dissolved into the main phase, a Nb-rich second phase was formed in all Nb-containing compositions. 相似文献