全文获取类型
收费全文 | 141430篇 |
免费 | 10517篇 |
国内免费 | 5399篇 |
专业分类
电工技术 | 7785篇 |
技术理论 | 11篇 |
综合类 | 8450篇 |
化学工业 | 24439篇 |
金属工艺 | 7568篇 |
机械仪表 | 8882篇 |
建筑科学 | 11414篇 |
矿业工程 | 3734篇 |
能源动力 | 4047篇 |
轻工业 | 8493篇 |
水利工程 | 2440篇 |
石油天然气 | 8258篇 |
武器工业 | 998篇 |
无线电 | 16362篇 |
一般工业技术 | 17710篇 |
冶金工业 | 7158篇 |
原子能技术 | 1370篇 |
自动化技术 | 18227篇 |
出版年
2024年 | 567篇 |
2023年 | 2285篇 |
2022年 | 3930篇 |
2021年 | 5347篇 |
2020年 | 4135篇 |
2019年 | 3467篇 |
2018年 | 3846篇 |
2017年 | 4341篇 |
2016年 | 3904篇 |
2015年 | 5063篇 |
2014年 | 6808篇 |
2013年 | 8173篇 |
2012年 | 8641篇 |
2011年 | 9323篇 |
2010年 | 8223篇 |
2009年 | 7814篇 |
2008年 | 7523篇 |
2007年 | 7236篇 |
2006年 | 7557篇 |
2005年 | 6586篇 |
2004年 | 4529篇 |
2003年 | 4041篇 |
2002年 | 3718篇 |
2001年 | 3349篇 |
2000年 | 3519篇 |
1999年 | 4024篇 |
1998年 | 3600篇 |
1997年 | 2950篇 |
1996年 | 2696篇 |
1995年 | 2234篇 |
1994年 | 1854篇 |
1993年 | 1347篇 |
1992年 | 1067篇 |
1991年 | 800篇 |
1990年 | 616篇 |
1989年 | 527篇 |
1988年 | 433篇 |
1987年 | 256篇 |
1986年 | 230篇 |
1985年 | 155篇 |
1984年 | 129篇 |
1983年 | 93篇 |
1982年 | 91篇 |
1981年 | 72篇 |
1980年 | 55篇 |
1979年 | 38篇 |
1978年 | 13篇 |
1977年 | 33篇 |
1976年 | 16篇 |
1975年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
81.
Kuo‐Hsiung Wang Tzong‐Ming Wu Yeng‐Fong Shih Chien‐Ming Huang 《Polymer Engineering and Science》2008,48(9):1833-1839
The water bamboo husk is one of major agricultural wastes in Taiwan. In this study, the powder obtained from the water bamboo husk was added to poly(lactic acid) (PLA) to form novel reinforced biodegradable composites. Morphologies, mechanical properties, and heat resistance of these water bamboo powder reinforced composites were investigated. The results indicate that the char yields were increased as plant powder was incorporated to PLA. In addition, the mechanical properties were also enhanced due to the addition of powders. The increments of storage moduli of PLA were about 50–200%. Moreover, the increments of loss moduli of PLA were about 70–200%. On the other hand, the Tg of PLA was slightly decreased by the addition of powder, and this may improve the brittle characteristics of PLA. Furthermore, this type of reinforced PLA would be more environmental friendly than the artificial additive‐reinforced one. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers 相似文献
82.
Wei Fen Zhang Xi Guang Chen Pi Wu Li Cheng Sheng Liu Qiang Zhi He 《Drying Technology》2008,26(1):108-115
Three kinds of carboxymethyl chitosan/β-cyclodextrin microspheres loaded with theophylline were prepared by spray drying intended for pulmonary delivery. Mucociliotoxicity, permeation rate, and drug release characteristics of the product were investigated. The microspheres obtained by spray drying were found to be spherical with smooth or wrinkled surfaces. The mean particle size was between 3.39 and 6.06 µm. The microspheres demonstrated high product yield (43.7-50.2%), high drug loading (13.7-38.1%), and high encapsulation efficiency (86.9-92.8%). FT-IR indicated that there were interactions of theophylline with carboxymethyl chitosan matrix. Further studies on mucociliotoxicity and permeation confirmed that microspheres had better adaptability and high permeation rate. In vitro drug release from the microspheres was not related to the drug/polymer ratios. 相似文献
83.
Conventional cancer therapies, the second leading cause of death worldwide, result in serious side effects and, at best, merely extend the patient''s lifespan by a few years. Searching for effective prevention is of high priority in both basic and clinical sciences. In recent decades natural products have been considered to be an important source of cancer chemopreventive agents. Red wine polyphenols, which consisted of various powerful antioxidants such as flavonoids and stilbenes, have been implicated in cancer prevention and that promote human health without recognizable side effects. Since resveratrol, a major component of red wine polyphenols, has been studied and reviewed extensively for its chemopreventive activity to interfere with the multi-stage carcinogenesis, this review focuses on recent progress in studies on cancer chemopreventive activities of red wine polyphenol extracts and fractions as well as other red wine polyphenols, like procyanidin B5 analogues and myricetin. 相似文献
84.
分析了湿法成形薄型陶瓷砖干燥的特点.具体讨论了微波干燥和少空气干燥方式在湿法薄形陶瓷砖干燥上中应用及干燥过程中坯体传动方式的选择。 相似文献
85.
86.
管内覆丝网强化对流换热及阻力特性的实验研究 总被引:1,自引:1,他引:0
通过实验对管内覆丝网管进行了强迫对流换热和阻力特性研究。结果表明:管内覆丝网使换热明显增强,阻力也相应增长。菱形丝网对角线距离与平行边距离之比对换热效果有决定作用,丝网厚度对换热的影响比较小,而丝网网格的大小对换热几乎没有影响,在相同的泵功率和几何条件下,换热系数最大增加21%。 相似文献
87.
The two gene-duplicated cAMP binding domains in the regulatory subunits of cAMP dependent protein kinase are each comprised of an A helix, an eight-stranded beta-barrel, and a B and C helix (1). The A domain is required for high affinity binding to C, while the B domain regulates access to the A domain. Using a combination of a yeast two-hybrid screen coupled with deletion analysis, cAMP binding domain A of RI was dissected into two structurally and functionally distinct subsites, one that binds cAMP and another that binds the C subunit. The minimum stable subdomain required for binding to C in the 1-3 micromolar range is composed of residues 94-169, while residues 236-244, mapped to the C helix of cAMP binding domain A, were defined as a second surface necessary for high affinity (5-10 nanomolar) binding to C. This portion of the C helix, due to its position directly between the two subsites, serves as a molecular switch for either a cAMP-bound conformation or a C-bound conformation and can thus modulate interactions of cAMP binding domain A with cAMP, with C, and with cAMP binding domain B. 相似文献
88.
89.
本文主要完成了液态金属钠高温沸腾实验回路的应力分析与计算,确定了回路高温区连接管系的布置型式和支吊架系统,是该回路总体设计的重要组成部分。 相似文献
90.
W Guo RS Lovell YH Zhang BL Huang TP Burris WJ Craigen ER McCabe 《Canadian Metallurgical Quarterly》1996,178(1-2):31-34
We cloned the murine full-length cDNA encoding Ahch, the mouse homologue of DAX1 (DSS-AHC Region on Human X Chromosome, Gene1) which is the gene responsible for human X-linked adrenal hypoplasia congenita (AHC) and hypogonadotropic hypogonadism (HH). Sequence analysis revealed that the murine and human cDNAs have 65% aa identity and 75% aa similarity overall. The cysteine residues in the putative DNA binding domain, which may interact with Zn2+ ions to form zinc fingers, are 100% conserved between the two species, indicating that the novel zinc-finger structures in DAX1 may be functional. In addition, mouse interspecific backcrosses show that the Ahch gene is closely linked to the glycerol kinase locus, GyK, on the mouse X chromosome, indicating that the order of the loci is conserved in this syntenic region between mouse and human. 相似文献