全文获取类型
收费全文 | 8623篇 |
免费 | 878篇 |
国内免费 | 344篇 |
专业分类
电工技术 | 555篇 |
综合类 | 496篇 |
化学工业 | 1465篇 |
金属工艺 | 411篇 |
机械仪表 | 460篇 |
建筑科学 | 534篇 |
矿业工程 | 185篇 |
能源动力 | 335篇 |
轻工业 | 781篇 |
水利工程 | 142篇 |
石油天然气 | 363篇 |
武器工业 | 64篇 |
无线电 | 1067篇 |
一般工业技术 | 1224篇 |
冶金工业 | 608篇 |
原子能技术 | 112篇 |
自动化技术 | 1043篇 |
出版年
2024年 | 14篇 |
2023年 | 101篇 |
2022年 | 216篇 |
2021年 | 319篇 |
2020年 | 254篇 |
2019年 | 249篇 |
2018年 | 242篇 |
2017年 | 267篇 |
2016年 | 295篇 |
2015年 | 307篇 |
2014年 | 491篇 |
2013年 | 545篇 |
2012年 | 572篇 |
2011年 | 664篇 |
2010年 | 595篇 |
2009年 | 509篇 |
2008年 | 503篇 |
2007年 | 465篇 |
2006年 | 392篇 |
2005年 | 407篇 |
2004年 | 270篇 |
2003年 | 272篇 |
2002年 | 287篇 |
2001年 | 273篇 |
2000年 | 191篇 |
1999年 | 169篇 |
1998年 | 232篇 |
1997年 | 149篇 |
1996年 | 115篇 |
1995年 | 97篇 |
1994年 | 83篇 |
1993年 | 61篇 |
1992年 | 43篇 |
1991年 | 30篇 |
1990年 | 27篇 |
1989年 | 24篇 |
1988年 | 18篇 |
1987年 | 9篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 10篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 14篇 |
1980年 | 7篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1973年 | 3篇 |
排序方式: 共有9845条查询结果,搜索用时 15 毫秒
71.
钠离子电池具有安全性高、钠资源丰富、成本低等独特优势,引起了人们的广泛关注.构建具有良好电化学性能的钠离子电池的关键之一就是正极材料的选取,氟化磷酸钒钠[Na3V2(PO4)2F3]因其结构稳定性好、离子输运快、工作电位高等特点被认为是一种很有前途的正极材料.但电导率较低,使其电化学性能较差;制备成本较高,阻碍了其大规模应用的发展.综述了在提升Na3 V2(PO4)2 F3电化学性能方面的措施,主要包括改进制备方法、离子掺杂、表面包覆等.为今后高性能Na3 V2(PO4)2 F3的合理设计提供了很好的参考. 相似文献
72.
73.
Ju Ri Ham Ra-Yeong Choi Yongjin Lee Mi-Kyung Lee 《International journal of molecular sciences》2021,22(7)
Mealworms (Tenebrio molitor larva) are an edible insect and a protein-rich food; however, research on mealworms as a substitute protein is insufficient. In this study, mealworm fermentation extract (TMP) was assessed as a replacement for soy protein (SP) in a control diet (CON) or a high-fat diet (HFD) of mice for 12 weeks. TMP substitution reduced body weight, body weight gain, body fat mass (perirenal and mesenteric), fat size, glucose intolerance, and insulin resistance compared to the HFD-SP group. TMP alleviated hepatic steatosis (lipid contents and lipid droplets) in high-fat-fed mice and down-regulated the PPARγ, CD36, and DGAT2 gene levels. Proteomic analysis showed that a HFD for 12 weeks up-regulated 20 proteins and down-regulated 17 proteins in mice fed SP. On the other hand, TMP reversed the protein profiles. TMP significantly down-regulated KHK, GLO1, ATP5H, SOD, and DDAH1 and up-regulated DLD, Mup1, CPS1, Ces3b, PDI, and HYOU1 compared to the HFD-SP group. These proteins are involved in the glucose, lipid, and amino acid metabolism, as well as in oxidative stress and endoplasmic reticulum stress. Thus, substituting SP for TMP helped improve HFD-induced obesity, steatosis, and insulin resistance in mice. These results suggest that TMP is a potential substitute for commonly used protein sources. 相似文献
74.
The nucleation efficiency (NE) of stereocomplex crystallites (SCs) formed in asymmetric poly(L-lactide)/poly(D-lactide) (PLLA/PDLA) blends is generally unsatisfactory because the competition between stereocomplexation and chain mixing involved in the melt-mixing process can cause low formation efficiency and even severe aggregation of SCs. Herein, it is attempted to achieve high-efficient formation of finely dispersed SCs particles by designing a unique melt-mixing procedure, where the mixing of PLLA with 0.75 wt% PDLA is first performed at elevated temperatures (far above the melting temperature of SCs) to allow the homogeneous mixing of PLLA/PDLA chains and then at a low temperature (slightly above that of homocrystallites) to permit the full stereocomplexation of the premixed chains. It is found that the SCs formed in the blends exhibit unexpectedly low NEs (e.g., 54.5%), much inferior to that (73.6%) in the counterpart without undergoing premixing. This is because the introduction of premixing leads to a remarkable deterioration in the amount of SCs particles formed, despite decreased particle size, highlighting that the direct mixing at low temperatures of 170–180 °C (about 20–30 °C lower than that used in common melt-processing of PLA) is more effective for the construction of SCs with superior NE. The mechanisms for these striking findings are discussed. 相似文献
75.
Woohyeon Shin Jun Seop Kim Heesung Kim Hui Ju Choi Hee Jung Lee Moon Kwang Um Moon Kee Choi Kyeongwoon Chung 《大分子材料与工程》2021,306(5):2100007
Hydrogels are recognized as one of the most promising materials for e-skin devices because of their unique applicable functionalities such as flexibility, stretchability, biocompatibility, and conductivity. Beyond the excellent sensing functionalities, the e-skin devices further need to secure a target-oriented 3D structure to be applied onto various body parts having complex 3D shapes. However, most e-skin devices are still fabricated in simple 2D film-type devices, and it is an intriguing issue to fabricate complex 3D e-skin devices resembling target body parts via 3D printing. Here, a material design guideline is provided to prepare multifunctional hydrogels and their target-oriented 3D structures based on extrusion-based 3D printing. The material design parameters to realize target-oriented 3D structures via 3D printing are systematically derived from the correlation between material design of hydrogels and their gelation characteristics, rheological properties, and 3D printing processability for extrusion-based 3D printing. Based on the suggested material design window, ion conductive self-healable hydrogels are designed and successfully applied to extrusion-based 3D printing to realize various 3D shapes. 相似文献
76.
77.
78.
79.
将9SiCr钢的粒状原始组织改变为片状,再经830℃淬火后,其马氏体形态为筐篮编结状。而传统工艺所获得的马氏体形态为针状.这种筐篮编结状马氏体是9SiCr钢中一种崭新的组织形态,其精细结构为平行成束的板条。亚结构为高密度缠结位错.它有良好的综合机械性能,强韧性高,耐磨性高。 相似文献
80.
磷酸铁(FePO4)是锂电池正极材料磷酸铁锂(LiFePO4)的核心前驱体,FePO4形貌及硫含量对合成的LiFePO4材料性能有重要影响。为得到类球形低硫FePO4产品,在传统液相沉淀法技术基础上做了改进优化,添加十六烷基三甲基溴化铵(CTAB)作为形貌助剂提高产品球形度,添加氨水作为配体形成磷酸铁铵配合物改善结晶过程,降低产品硫含量。结果表明:所制备的FePO4产品硫质量分数低,达到2.6×10 -5,形貌为均一的微米类球形颗粒,D50=11.4 μm,振实密度达到1.22 g/cm 3,有望成为制备高压实密度LiFePO4材料的核心前驱体。 相似文献