全文获取类型
收费全文 | 16112篇 |
免费 | 1854篇 |
国内免费 | 877篇 |
专业分类
电工技术 | 106篇 |
技术理论 | 1篇 |
综合类 | 798篇 |
化学工业 | 8254篇 |
金属工艺 | 418篇 |
机械仪表 | 388篇 |
建筑科学 | 154篇 |
矿业工程 | 155篇 |
能源动力 | 184篇 |
轻工业 | 2043篇 |
水利工程 | 22篇 |
石油天然气 | 1451篇 |
武器工业 | 148篇 |
无线电 | 1229篇 |
一般工业技术 | 2564篇 |
冶金工业 | 152篇 |
原子能技术 | 175篇 |
自动化技术 | 601篇 |
出版年
2024年 | 108篇 |
2023年 | 476篇 |
2022年 | 793篇 |
2021年 | 1091篇 |
2020年 | 710篇 |
2019年 | 678篇 |
2018年 | 553篇 |
2017年 | 550篇 |
2016年 | 646篇 |
2015年 | 631篇 |
2014年 | 893篇 |
2013年 | 1058篇 |
2012年 | 1076篇 |
2011年 | 1034篇 |
2010年 | 727篇 |
2009年 | 781篇 |
2008年 | 637篇 |
2007年 | 825篇 |
2006年 | 784篇 |
2005年 | 695篇 |
2004年 | 584篇 |
2003年 | 488篇 |
2002年 | 396篇 |
2001年 | 408篇 |
2000年 | 352篇 |
1999年 | 300篇 |
1998年 | 265篇 |
1997年 | 201篇 |
1996年 | 202篇 |
1995年 | 160篇 |
1994年 | 122篇 |
1993年 | 109篇 |
1992年 | 94篇 |
1991年 | 84篇 |
1990年 | 62篇 |
1989年 | 34篇 |
1988年 | 29篇 |
1987年 | 26篇 |
1986年 | 21篇 |
1985年 | 36篇 |
1984年 | 33篇 |
1983年 | 25篇 |
1982年 | 34篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1976年 | 4篇 |
1959年 | 1篇 |
1951年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
分子结构对增塑聚氯乙烯性能的影响 总被引:2,自引:0,他引:2
研究了聚合度、分子量分布和支化结构对增塑聚氯乙烯加工流变性能和物理力学性能的影响。结果表明,增塑PVC的加工流变性能随聚合度的增加而恶化;拓宽分子量分布和引入支化结构均有利于加工流变性能的提高;增塑PVC的拉伸强度随聚合度的增加而提高,而压缩永久变形却随之减小;分子量分布对物理力学性能的影响不大;支化PVC的拉伸强度略有下降。 相似文献
82.
We have performed selective area epitaxy (SAE) of CdTe layers grown by molecular beam epitaxy using a shadow mask technique.
This technique was chosen over other SAE techniques due to its simplicity and its compatibility with multiple SAE patterning
steps. Features as small as 50 microns × 50 microns were obtained with sharp, abrupt side walls and flat mesa tops. Separations
between mesas as small as 20 microns were also obtained. Shadowing effects due to the finite thickness of the mask were reduced
by placing the CdTe source in a near normal incidence position. Intimate contact between the mask and the substrate was essential
in order to achieve good pattern definition. 相似文献
83.
84.
Tempest Philip R.; White Patricia; Williamson E.Diane; Titball Richard W.; Kelly David C.; Kemp Graham J.L.; Gray Peter M.D.; Forster Simon J.; Carr Frank J.; Harris William J. 《Protein engineering, design & selection : PEDS》1994,7(12):1501-1507
We have used the technique of antibody reshaping to producea humanized antibody specific for the a toxin of Clostridiumperfringens. The starting antibody was from a mouse hybridomafrom which variable (V) region nucleo-tide sequences were determined.The complementarity-determining regions (CDRs) from these Vregions were then inserted into human heavy and light chainV region genes with human constant region gene fragments subsequentlyadded. The insertion of CDRs alone into human frameworks didnot produce a functional reshaped antibody and modificationsto the V region framework were required. With minor frameworkmodifications, the affinity of the original murine mAb was restoredand even exceeded. Where affinity was increased, an alteredbinding profile to overlapping peptides was observed. Computermodelling of the reshaped heavy chain V regions suggested thatamino acids adjacent to CDRs can either contribute to, or distort,CDR loop conformation and must be adjusted to achieve high bindingaffinity. 相似文献
85.
The development of biaxial segmental orientation and stress in a flexible-chain polymer fluid subjected to steady biaxial extensional flow is analyzed. Closed-formula model based on the Padè approximation of the inverse Langevin function in the non-Gaussian distribution of the chain end-to-end vectors is considered. The approach is free from the limitations related to finite chain extensibility and slow convergence of the series expansion formulations at higher chain deformations.Segmental orientation is characterized by the average orientation tensor, related axial orientation factors and global orientation anisotropy. Orientational behavior and corresponding stresses in the biaxial elongational potential flow are discussed in a wide range of elongation rates. Orientation characteristics calculated for the biaxial flow deformation are much higher than those predicted for the affine biaxial stretch deformation in polymer solids. 相似文献
86.
Bob Eisenberg 《Journal of Computational Electronics》2002,1(3):331-333
Ion channels are proteins with a hole down their middle important in a wide range of biological functions yet simple enough to be analyzed as devices in the engineering tradition. 相似文献
87.
88.
Polyurethanes were prepared from pure 4,4′-diphenylmethane diisocyanate (MDI), 1,4-butane diol (BDO) or 1,2-ethane diol (EDO) and α,ω-hydroxyl poly(propylene oxide) (PPO) by reaction injection moulding (RIM). Hard segment (MDI + BDO or EDO) level was 45–50 wt%. The PPO had about 20% ethylene oxide copolymerized in at the chain ends to provide 80% primary OH end groups. Mn was varied from 2000 to 4000. Dibutyl tin dilaurate catalyst and mould temperature were varied. Dynamic mechanical, wide-angle X-ray, differential scanning calorimeter, molecular weight and tensile elongation measurements were made on the RIM polyurethanes. At low reaction rates (low catalyst or temperature) highly crystalline, well phase separated but low molecular weight polymers were produced. At high catalyst or temperature levels more poorly phase separated but high molecular weight, tough polymers resulted. Higher Mn PPO gave better phase separation and EDO gave higher melting temperatures. Preventing hard segment crystallinity by substituting asymmetric MDI or glycols resulted in phase compatibility. 相似文献
89.
超高分子量聚乙烯衬板在煤仓中的应用 总被引:2,自引:0,他引:2
介绍了井底煤仓溜煤斜面采用超高分子量聚乙烯衬板安装及应用情况 ,对井底煤仓棚煤原因及解决办法进行了探讨 相似文献
90.