全文获取类型
收费全文 | 11548篇 |
免费 | 1465篇 |
国内免费 | 367篇 |
学科分类
工业技术 | 13380篇 |
出版年
2024年 | 83篇 |
2023年 | 216篇 |
2022年 | 307篇 |
2021年 | 369篇 |
2020年 | 419篇 |
2019年 | 334篇 |
2018年 | 359篇 |
2017年 | 468篇 |
2016年 | 521篇 |
2015年 | 543篇 |
2014年 | 686篇 |
2013年 | 710篇 |
2012年 | 1012篇 |
2011年 | 1026篇 |
2010年 | 705篇 |
2009年 | 587篇 |
2008年 | 601篇 |
2007年 | 806篇 |
2006年 | 784篇 |
2005年 | 583篇 |
2004年 | 403篇 |
2003年 | 399篇 |
2002年 | 270篇 |
2001年 | 212篇 |
2000年 | 173篇 |
1999年 | 160篇 |
1998年 | 133篇 |
1997年 | 94篇 |
1996年 | 88篇 |
1995年 | 69篇 |
1994年 | 55篇 |
1993年 | 40篇 |
1992年 | 35篇 |
1991年 | 16篇 |
1990年 | 19篇 |
1989年 | 23篇 |
1988年 | 13篇 |
1987年 | 14篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 10篇 |
1981年 | 4篇 |
1980年 | 9篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
通过密度测定和DSC热分析,观测了超高分子量聚乙烯的辐射效应。实验结果表明:在吸收剂量0—1.13MGy范围内,密度随吸收剂量的增加而增大,熔化热和熔点也有所增加,特别是在低剂量范围内增加十分明显。以上结果都说明,超高分子量聚乙烯在辐照过程中,结晶在完善或有新的结晶形成 相似文献
5.
采用自行开发研制的超音速电弧喷设备,在45钢表面制成了钛铝合金复合涂层。并利用金相显微镜、X射线衍射仪、扫描电镜、电子探针,对涂层的成分、相结构、显微组织及其结合强度、显微硬度进行了研究。结果表明,利用超音速电弧喷涂设备,可以在45钢表面形成 度高、孔隙率低,结合强度较好和硬度高的Ti-Al合金涂层。 相似文献
6.
We have used a resonant ultrasound spectroscopy technique to measure the bulk and shear modulus of fully dense, polycrystalline MgB2 between 4 and 300 K. Both moduli show good agreement with published first principle calculations. The internal friction shows a broad maximum around 40 K. 相似文献
7.
SUSANNA DE CORDT MARC HENDRICKX GEERT MAESMANS PAUL TOBBACK 《International Journal of Food Science & Technology》1992,27(6):661-673
Biphasic and nth-order models were tested as to their usefulness to fit experimental inactivation data of Bacillus licheniformis α-amylase, immobilized on glass beads, and were discussed with respect to their suitability to characterize the considered enzymic system as a time—temperature integrator (TTI) to evaluate heat processes. Both isothermal and non-isothermal inactivation experiments were carried out. Model (kinetic) parameters (rate constant k, activation energy EA and reaction order n) were estimated using a non-linear regression procedure. The results obtained, especially the activation energy of about 293 kJ mole–1 , indicated a potential use of this system as a TTI for heating processes in the temperature range of 96–108°C. 相似文献
8.
9.
In this work, microcrystalline cellulose (MCC) was activated with ultrasonic waves. The influences of ultrasonic treatment on the changes of supramolecular structures and morphology structure were studied by WAXS and SEM. The accessibility of the MCC was characterized by water retention value (WRV) and specific surficial area. The influence of ultrasonic treatment on the reactivity of MCC was investigated through the reaction of MCC being oxidized into 2,3‐diadehyde cellulose (DAC) by periodate sodium. The mechanism of the reactivity change of ultrasonically treated MCC was examined. The results showed that the degree of crystallinity of MCC decreased and the degree of polymerization showed little change after treatment with ultrasonic waves. The morphologial variation of the treated MCC was significant when compared with the untreated MCC, which contribute to the improvement of accessibility. The aldehyde content of DAC prepared from ultrasonically treated MCC was improved from 64.19 to 85.00%, indicating that the regioselective oxidation reactivity of MCC was significantly improved. The aldehyde content was found to first increase with time of ultrasonic treatment to a point, and then decrease as time progressed. In addition, the aldehyde content was found to increase with an increase in ultrasonic power. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
10.