全文获取类型
收费全文 | 239124篇 |
免费 | 26334篇 |
国内免费 | 16764篇 |
专业分类
电工技术 | 20898篇 |
技术理论 | 4篇 |
综合类 | 21898篇 |
化学工业 | 31847篇 |
金属工艺 | 15334篇 |
机械仪表 | 16383篇 |
建筑科学 | 19891篇 |
矿业工程 | 8338篇 |
能源动力 | 7184篇 |
轻工业 | 21434篇 |
水利工程 | 7031篇 |
石油天然气 | 10569篇 |
武器工业 | 3051篇 |
无线电 | 27577篇 |
一般工业技术 | 23219篇 |
冶金工业 | 9335篇 |
原子能技术 | 3360篇 |
自动化技术 | 34869篇 |
出版年
2024年 | 1217篇 |
2023年 | 3825篇 |
2022年 | 7899篇 |
2021年 | 10798篇 |
2020年 | 8043篇 |
2019年 | 6056篇 |
2018年 | 6573篇 |
2017年 | 7796篇 |
2016年 | 6952篇 |
2015年 | 10653篇 |
2014年 | 13238篇 |
2013年 | 15788篇 |
2012年 | 18910篇 |
2011年 | 19633篇 |
2010年 | 18609篇 |
2009年 | 17576篇 |
2008年 | 17877篇 |
2007年 | 17267篇 |
2006年 | 15334篇 |
2005年 | 12324篇 |
2004年 | 8778篇 |
2003年 | 7031篇 |
2002年 | 6718篇 |
2001年 | 6019篇 |
2000年 | 4805篇 |
1999年 | 3106篇 |
1998年 | 1778篇 |
1997年 | 1440篇 |
1996年 | 1306篇 |
1995年 | 1124篇 |
1994年 | 912篇 |
1993年 | 612篇 |
1992年 | 477篇 |
1991年 | 351篇 |
1990年 | 268篇 |
1989年 | 233篇 |
1988年 | 172篇 |
1987年 | 121篇 |
1986年 | 113篇 |
1985年 | 53篇 |
1984年 | 47篇 |
1983年 | 38篇 |
1982年 | 39篇 |
1981年 | 49篇 |
1980年 | 55篇 |
1979年 | 37篇 |
1977年 | 11篇 |
1976年 | 12篇 |
1959年 | 20篇 |
1951年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 21 毫秒
71.
Dr. Lina Liang Tong-You Wade Wei Pei-Yu Wu Wouter Herrebout Ming-Daw Tsai Prof. Stéphane P. Vincent 《Chembiochem : a European journal of chemical biology》2020,21(20):2982-2990
d -Glycero-d -manno-heptose-1β,7-bisphosphate (HBP) and d -glycero-d -manno-heptose-1β-phosphate (H1P) are bacterial metabolites that were recently shown to stimulate inflammatory responses in host cells through the activation of the TIFA-dependent NF-κB pathway. To better understand structure-based activity in relation to this process, a family of nonhydrolyzable phosphonate analogues of HBP and H1P was synthesized. The inflammation modulation by which these molecules induce the TIFA-NF-κB signal axis was evaluated in vivo at a low-nanomolar concentration (6 nM) and compared to that of the natural metabolites. Our data showed that three phosphonate analogues had similar stimulatory activity to HBP, whereas two phosphonates antagonized HBP-induced TIFA-NF-κB signaling. These results open new horizons for the design of pro-inflammatory and innate immune modulators that could be used as vaccine adjuvant. 相似文献
72.
73.
Zu Guoqing Lu Yukuan Yan Yi Zhang Xiaoming Zhao Jingwei Du Wei Ran Xu Jiang Zhengyi 《Metals and Materials International》2020,26(2):248-259
Metals and Materials International - The flow behaviour and microstructure characteristics of a ferritic stainless steel were investigated using plain strain compression test on a Gleeble 3500... 相似文献
74.
75.
76.
Covalent triazine frameworks (CTFs) have been recently employed for visible light-driven photocatalysis due to their unique optical and electronic properties. However, the usually highly hydrophobic nature of CTFs, which originates from their overall aromatic backbone, leads to limitations of CTFs for applications in aqueous media. In this study, we aim to extend the range of the application media of CTFs and design hybrid material of a CTF and mesoporous silica (SBA-15) for efficient photocatalysis in aqueous medium. A thiophene-containing CTF was directly synthesized in mesopores of SBA-15. Due to the high surface area and the added hydrophilic properties by silica, the hybrid material demonstrated excellent adsorption of organic molecules in water. This leads not only to high photocatalytic performance of the hybrid material for the degradation of organic dyes in water, but also for efficient photocatalysis in solvent-free and solid state. Furthermore, the reusability, stability and easy recovery of the hybrid material offers promising metal-free heterogeneous photocatalyst for broader applications in different reaction media. 相似文献
77.
Shengyue Gu Shouyang Zhang Fei Liu Wei Li 《Journal of the European Ceramic Society》2018,38(15):5082-5091
Y2Hf2O7 possesses low thermal conductivity and high melting point, which make it promising for a new anti-ablation material. For evaluating the thermal stability and the potential applications of Y2Hf2O7 on anti-ablation protection of C/C composites, Y2Hf2O7 ceramic powder was synthesized by solution combustion method and Y2Hf2O7 coating was prepared on the surface of SiC coated C/C composites using SAPS. Results shown that the coating exhibits good ablation resistance under the heat flux of 2.4?MW/m2 with the linear and mass ablation rates are 0.16?μm?s?1 and ?0.028?mg?s?1, respectively, after ablation for 40?s. With the prolonging of the ablation time, the increasing thermal stress causes the increase of cracks. Moreover, the chemical erosion from SiO2 and the physical volatilization of low temperature molten products aggravate failure of the Y2Hf2O7 coating. 相似文献
78.
Tao Li Zehui Du Nobumichi Tamura Mao Ye Saikumar Inguva Wei Lu Xierong Zeng Shanming Ke Haitao Huang 《Journal of the European Ceramic Society》2018,38(4):1488-1497
(1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 ((1-x)PZN-xPT in short) is one of the most important piezoelectric materials. In this work, we extensively investigated (1-x)PZN-xPT (x = 0.07–0.11) ferroelectric single crystals using in-situ synchrotron μXRD, complemented by TEM and PFM, to correlate microstructures with phase transitions. The results reveal that (i) at 25 °C, the equilibrium state of (1-x)PZN-xPT is a metastable orthorhombic phase for x = 0.07 and 0.08, while it shows coexistence of orthorhombic and tetragonal phases for x = 0.09 and x = 0.11, with all ferroelectric phases accompanied by ferroelastic domains; (ii) upon heating, the phase transformation in x = 0.07 is Orthorhombic → Monoclinic → Tetragonal → Cubic. The coexistence of ferroelectric tetragonal and paraelectric cubic phases was in-situ observed in x = 0.08 above Curie temperature (TC), and (iii) phase transition can be explained by the evolution of the ferroelectric and ferroelastic domains. These results disclose that (1-x)PZN-xPT are in an unstable regime, which is possible factor for its anomalous dielectric response and high piezoelectric coefficient. 相似文献
79.
目的: 建立快速灵敏的LC-MS/MS法测定人血浆中阿莫西林浓度,并用于两种阿莫西林胶囊的一致性评价。方法: 采用岛津公司LCMS-8060型LC-MS/MS仪,以MRM模式测定阿莫西林(m/z 366.00/114.00)的浓度,d4-阿莫西林作内标(m/z 370.10/114.05),离子源为ESI源。色谱柱选用Waters ACQUITY BEH C18(2.1×50 mm,1.7 μm),梯度洗脱。血浆样本加入内标,经甲醇沉淀蛋白后取上清液进样检测。结果: 所建方法经验证,其线性、准确度、精密度、最低定量限、提取回收率、特异性、基质效应、稳定性等各项指标均符合CFDA的指导原则及最新核查标准要求,并较文献报道中的方法有处理简单、灵敏度高、色谱峰形好的优点。结论: 所建方法快速、灵敏,适用于人血浆中阿莫西林浓度的检测。用于一致性评价的样本实测,两种制剂生物等效。 相似文献
80.
Baizhan Li Chenqiu Du Hong Liu Wei Yu Jie Zheng Meilan Tan Zhenxing Jin Wenjie Li Jing Wu Lu Chen Runming Yao 《Indoor air》2019,29(2):308-319
The extensive research interests in environmental temperature can be linked to human productivity / performance as well as comfort and health; while the mechanisms of physiological indices responding to temperature variations remain incompletely understood. This study adopted a physiological sensory nerve conduction velocity (SCV) as a temperature‐sensitive biomarker to explore the thermoregulatory mechanisms of human responding to annual temperatures. The measurements of subjects’ SCV (over 600 samples) were conducted in a naturally ventilated environment over all four seasons. The results showed a positive correlation between SCV and annual temperatures and a Boltzmann model was adopted to depict the S‐shaped trend of SCV with operative temperatures from 5°C to 40°C. The SCV increased linearly with operative temperatures from 14.28°C to 20.5°C and responded sensitively for 10.19°C‐24.59°C, while tended to be stable beyond that. The subjects’ thermal sensations were linearly related to SCV, elaborating the relation between human physiological regulations and subjective thermal perception variations. The findings reveal the body SCV regulatory characteristics in different operative temperature intervals, thereby giving a deeper insight into human autonomic thermoregulation and benefiting for built environment designs, meantime minimizing the temperature‐invoked risks to human health and well‐being. 相似文献