全文获取类型
收费全文 | 4075篇 |
免费 | 499篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 50篇 |
综合类 | 8篇 |
化学工业 | 1052篇 |
金属工艺 | 185篇 |
机械仪表 | 271篇 |
建筑科学 | 47篇 |
能源动力 | 213篇 |
轻工业 | 352篇 |
水利工程 | 4篇 |
石油天然气 | 3篇 |
无线电 | 781篇 |
一般工业技术 | 1093篇 |
冶金工业 | 124篇 |
原子能技术 | 42篇 |
自动化技术 | 353篇 |
出版年
2024年 | 5篇 |
2023年 | 45篇 |
2022年 | 80篇 |
2021年 | 127篇 |
2020年 | 113篇 |
2019年 | 153篇 |
2018年 | 147篇 |
2017年 | 183篇 |
2016年 | 187篇 |
2015年 | 194篇 |
2014年 | 246篇 |
2013年 | 292篇 |
2012年 | 294篇 |
2011年 | 379篇 |
2010年 | 262篇 |
2009年 | 238篇 |
2008年 | 249篇 |
2007年 | 175篇 |
2006年 | 163篇 |
2005年 | 139篇 |
2004年 | 119篇 |
2003年 | 146篇 |
2002年 | 101篇 |
2001年 | 86篇 |
2000年 | 61篇 |
1999年 | 86篇 |
1998年 | 69篇 |
1997年 | 40篇 |
1996年 | 30篇 |
1995年 | 31篇 |
1994年 | 28篇 |
1993年 | 24篇 |
1992年 | 18篇 |
1991年 | 15篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有4578条查询结果,搜索用时 15 毫秒
1.
2.
3.
Properties and applications of β‐glycosidase from Bacteroides thetaiotaomicron that specifically hydrolyses isoflavone glycosides 下载免费PDF全文
Da‐Hye Byun Hye‐Jeong Choi Hye‐Won Lee Hye‐Yeon Jeon Woo‐Jae Choung Jae‐Hoon Shim 《International Journal of Food Science & Technology》2015,50(6):1405-1412
To modify the glycan part of glycosides, the gene encoding β‐glycosidase was cloned from Bacteroides thetaiotaomicron VPI‐5482. The cloned gene, bt_1780, was expressed in Escherichia coli MC1061 and the expressed enzyme was purified using Ni‐NTA affinity chromatography. The purified enzyme, BTBG, showed optimal activity at 50 °C and pH 5.5. Interestingly, this enzyme did not have any hydrolysing activity on ordinary β‐linkage–containing substrates such as xylobiose, lactose and cello‐oligosaccharide, but specifically hydrolysed isoflavone glycosides such as daidzin, genistin and glycitin. Compared to a commercial beta glucosidase, BTBG selectively hydrolysed isoflavone glycosides in soybean extract mixture solution. These results suggest that BTBG may be a specialized enzyme for the hydrolysis of glycosides and that the substrate specificity of BTBG is applicable for the bioconversion of isoflavone glycosides in the food industry. 相似文献
4.
5.
Jin Tae Kim Keun Byoung Yoon Choon-Gi Choi 《Photonics Technology Letters, IEEE》2004,16(7):1664-1666
A novel fabrication process using a hot embossing technique has been developed for micromechanical passive alignment of polymer planar lightwave circuit (PLC) devices. With only one step of embossing, single-mode waveguide straight channels and micropedestals for passive aligning are simultaneously defined on a polymer thin film with an accuracy of /spl plusmn/0.5 /spl mu/m. This process reduces the steps for fabricating alignment structures. A fabricated polymer PLC chip and fibers are combined on a v-grooved silicon optical bench (SiOB) in a flip-chip manner. The process provides a coupling loss as low as 0.67 dB per coupling face and a cost-effective packaging solution for various polymer PLC devices. 相似文献
6.
To determine three‐dimensional fiber orientation states in injection‐molded short‐fiber composites, a confocal laser scanning microscope (CLSM) is used. Since the CLSM optically sections the specimen, more than two images of the cross sections on and below the surface of the composite can be obtained. Three‐dimensional fiber orientation states can be determined by using geometric parameters of fiber images obtained from two parallel cross sections. For experiments, carbon‐fiber‐reinforced polystyrene is examined by the CLSM and geometric parameters of fibers on each cross‐sectional plane are measured by an image analysis. In order to describe fiber orientation states compactly, orientation tensors are determined at different positions of the prepared specimen. Three‐dimensional orientation states are obtained without any difficulty by determining the out‐of‐plane angles utilizing fiber images on two parallel planes acquired by the CLSM. Orientation states are different at different positions and show the shell–core structure along the thickness of the specimen. Fiber orientation tensors are predicted by a numerical analysis and the numerically predicted orientation states show good agreement with measured ones. However, some differences are found at the end of cavity. They may result from the fountain flow effects, which are not considered in the numerical analysis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 500–509, 2003 相似文献
7.
Min Jeong Noh Tae Gyun Kim In Kwon Hong Ki-Pung Yoo 《Korean Journal of Chemical Engineering》1995,12(1):48-55
A new transparent microscale circulation-type high pressure equilibrium cell with on-line sampling was devised. With this
apparatus, experimental solubility of molecularly complex species such as steroids (cholesterol, stigmasterol and ergosterol)
and fatty acids (palmitic acid and stearic acid) in supercritical carbon dioxide(sc-C02) were measured. Also, to find an appropriate substance for enhancing both the polarity and the solubility power of the SC-CO2 solvent, we arbitrarily selected three polar substances such as acetone, methanol and water and the effect of these cosolvents
on the solubility of solutes in SC-CO2 are examined. The supercritical phase equilibrium data of solute-cosolvent-sc-CO2 systems were quantitatively correlated using a new equation of state based on the lattice fluid theory incorporated with
the concept of multibody interaction. We found that the addition of tracer amount of acetone or methanol to SC-CO2 enhances the solubility of all solutes about thirty to sixty times when compared with the case of pure sc-CO2 However, for the case of cosolvent water, no further enhancement of the solubility of solutes was realized. Also, the versatile
fittability of the equation of state proposed in this work was demonstrated with the newly measured ternary supercritical
equilibrium data. 相似文献
8.
Won Tae KimCheolho Bai Young I. Cho 《International Journal of Heat and Mass Transfer》2002,45(3):597-607
The present study introduces a new experimental method to visualize the fouling process of CaCO3. A mini-channel heat exchanger system with a microscopic imaging technique was developed for real-time visualization of the fouling process. The present study discussed how scale started initially, how scale formed thick layers, and how a small crystal grew into a large one, touching the adjacent one. Detail microscopic images of scale crystals and corresponding fouling resistances were obtained over the entire fouling process. The microscopic observation indicated that the fouling process could be divided into three stages: an induction period, a period of uniform generation of nuclei, and a period of uniform growth of scale. Sudden appearance of numerous small nuclei indicated the end of the induction period, a key event before the rapid increase in the fouling resistance. The present experimental method using microscopic images of the wet fouling process provides a valuable insight on the fouling mechanism. 相似文献
9.
In polyolefin processes the melt index (MI) is the most important control variable indicating product quality. Because of
the difficulty in the on-line measurement of MI, a lot of MI estimation and correlation methods have been proposed. In this
work a new dynamic MI estimation scheme is developed based on system identification techniques. The empirical MI estimation
equation proposed in the present study is derived from the 1
st
-order dynamic models. Effectiveness of the present estimation scheme was illustrated by numerical simulations based on plant
operation data including grade change operations in high density polyethylene (HDPE) processes. From the comparisons with
other estimation methods it was found that the proposed estimation scheme showed better performance in MI predictions. The
virtual sensor model developed based on the estimation scheme was combined with the virtual on-line analyzer (VOA) to give
a quality control system to be implemented in the actual HDPE plant. From the application of the present control system, significant
reduction of transition time and the amount of off-spec during grade changes was achieved 相似文献
10.
Fast DCT algorithm with fewer multiplication stages 总被引:1,自引:0,他引:1
Yeonsik Jeong Imgeun Lee Hak Soo Kim Kyu Tae Park 《Electronics letters》1998,34(8):723-724
A novel fast DCT scheme with reduced multiplication stages and fewer additions and multiplications is proposed. The proposed algorithm is structured so that most multiplications tend to be performed at the final stage, which reduces the propagation error that could occur in the fixed-point computation. Minimisation of the multiplication stages can further decrease the error 相似文献