全文获取类型
收费全文 | 1176篇 |
免费 | 23篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 42篇 |
综合类 | 2篇 |
化学工业 | 287篇 |
金属工艺 | 40篇 |
机械仪表 | 46篇 |
建筑科学 | 14篇 |
能源动力 | 33篇 |
轻工业 | 94篇 |
水利工程 | 14篇 |
石油天然气 | 2篇 |
无线电 | 71篇 |
一般工业技术 | 246篇 |
冶金工业 | 172篇 |
原子能技术 | 34篇 |
自动化技术 | 107篇 |
出版年
2023年 | 3篇 |
2022年 | 7篇 |
2021年 | 9篇 |
2020年 | 14篇 |
2019年 | 8篇 |
2018年 | 13篇 |
2017年 | 13篇 |
2016年 | 20篇 |
2015年 | 17篇 |
2014年 | 31篇 |
2013年 | 44篇 |
2012年 | 45篇 |
2011年 | 67篇 |
2010年 | 48篇 |
2009年 | 50篇 |
2008年 | 58篇 |
2007年 | 59篇 |
2006年 | 47篇 |
2005年 | 33篇 |
2004年 | 38篇 |
2003年 | 41篇 |
2002年 | 35篇 |
2001年 | 22篇 |
2000年 | 18篇 |
1999年 | 25篇 |
1998年 | 70篇 |
1997年 | 49篇 |
1996年 | 44篇 |
1995年 | 34篇 |
1994年 | 23篇 |
1993年 | 21篇 |
1992年 | 13篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 19篇 |
1988年 | 15篇 |
1987年 | 9篇 |
1986年 | 16篇 |
1985年 | 14篇 |
1984年 | 18篇 |
1983年 | 13篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 4篇 |
1978年 | 11篇 |
1977年 | 12篇 |
1976年 | 5篇 |
1973年 | 4篇 |
1972年 | 5篇 |
排序方式: 共有1204条查询结果,搜索用时 15 毫秒
41.
A study was made to investigate an optimum condition for ruthenium tetraoxide staining of poly(butylene terephthalate) (PBT) with glass transition temperature as low as ca. 23 degrees C for TEM observation of melt-grown PBT crystals. The morphological study of ultrathin sections prepared based on optimum staining at 25 degrees C for 8 h revealed formation of fringed-micellar crystal nuclei in the early stage and folded-chain fringed-micellar crystals in the later stage of isothermal crystallization at 40 degrees C from melt. The fraction of chain-folded crystals increased with increasing crystallization temperature from the quantitative analysis of crystal thickness in comparison with the reported morphology using the replica method. 相似文献
42.
Fabrication of optics by use of plasma chemical vaporization machining with a pipe electrode 总被引:1,自引:0,他引:1
Takino H Shibata N Itoh H Kobayashi T Yamamura K Sano Y Mori Y 《Applied optics》2002,41(19):3971-3977
We figure optical surfaces by plasma chemical vaporization machining (CVM) with a pipe electrode, in which an rf plasma generated at the electrode tip under approximately atmospheric pressure moves over the surfaces. We propose a shaping method in which the movement of plasma on the surfaces can be determined. Flat and aspheric surfaces are successfully figured with the desired peak-to-valley shape accuracy of 0.1 microm. The root-mean-square roughness of the resultant surfaces is at the subnanometer level. These results confirm that the plasma CVM and the shaping method have the capability to fabricate optics with high accuracy. 相似文献
43.
Steroid hormones, such as progesterone, oestrogen, androgen and meiosis activating sterols, are secreted from cumulus cells that are stimulated by gonadotrophins during maturation of oocytes in vitro. These steroid hormones may be absorbed by mineral oil or paraffin oil; however, in vitro maturation of pig oocytes is commonly performed using medium covered by oil. In this study, high concentrations of progesterone, oestradiol and testosterone were detected in the culture medium after pig cumulus-oocyte complexes (COCs) were cultured with FSH and LH for 44 h in medium without an oil overlay. However, high concentrations of these steroid hormones were not detected in medium when COCs were cultured with the mineral oil overlay. When high concentrations of these steroid hormones were secreted by COCs, germinal vesicle breakdown (GVBD) and the activation of p34(cdc2) kinase and mitogen-activated protein (MAP) kinase in oocytes occurred earlier in comparison with oocytes cultured in medium covered with mineral oil. Moreover, a decrease in p34(cdc2) kinase activity during meiotic progression beyond metaphase I was observed in oocytes cultured in conditions under which high concentrations of steroid hormones were secreted by COCs. In addition, the rate of development to the blastocyst stage after IVF was higher in oocytes matured in medium without an oil overlay. These adverse effects of oil may be explained by absorption by the oil of cumulus-secreted steroids or by the release of toxic compounds into the medium. 相似文献
44.
Yoshitomo Masuda Norio Nihei Ryo Sakurai Reiji Hattori 《Journal of the Society for Information Display》2006,14(5):443-448
Abstract— A novel reflective display [Quick‐Response Liquid Powder Display (QR‐LPD®)], has been developed. This paper‐like display has the advantages of outstanding image stability, easy viewing, low‐power consumption, and a high‐response time. QR‐LPD® will be promoted, initially, for use as electronic price‐tag displays for merchandise. In addition, QR‐LPD® is suitable for flexible display applications because it does not require TFT arrays or a high‐temperature process while maintaining an excellent paper‐like image as well as glass‐type display compatibility. 相似文献
45.
Peptide transporters mediate the H+-coupled uphill transport of oligopeptides and peptide-like drugs such as beta-lactam antibiotics in the intestinal and renal brush-border membranes. Two H+/peptide cotransporters, PEPT1 and PEPT2, have been cloned and functionally characterized. In this study, we examined the interaction of the dipeptides and beta-lactam antibiotics with the histidine residue of rat PEPT1 and PEPT2 transfected into the renal epithelial cell line LLC-PK1. Diethylpyrocarbonate (DEPC), which is a histidine residue modifier, abolished the glycylsarcosine uptake by both transfectants. The DEPC-induced inhibition of glycylsarcosine uptake via PEPT1 or PEPT2 was attenuated by an excess of dipeptide or aminocephalosporin. In contrast, anionic cephalosporins without an alpha-amino group and bestatin, which is an antineoplastic drug with a beta-amino group, did not attenuate the DEPC-induced inactivation of PEPT1 and PEPT2. The DEPC inactivation of PEPT1 was almost prevented by various charged dipeptides, which suggests that the inability of the drugs without an alpha-amino group to prevent the DEPC inactivation was not due to their ionic charge. These findings suggest that the alpha-amino group of beta-lactam antibiotics interacts with the histidine residue of PEPT1 and PEPT2 and may be involved in the mechanism of substrate recognition by the peptide transporters. 相似文献
46.
47.
H. Terada 《Engineering Fracture Mechanics》1976,8(2):441-444
Stress intensity factor of a crack perpendicular to the welding bead in a wide plate is analyzed as a plane problem of elasticity. The function which .simulates the residual stress distribution qualitatively is assumed. Crack analysis is performed by using the Muskhelishvili's stress function. Results are given in figures and table. 相似文献
48.
49.
Several heterodetic cyclic nonapeptides modeled after the disulfide loops of Bowman-Birk inhibitor which involve either the anti-tryptic or anti-chymotryptic region have been synthesized by the conventional method. The inhibitory properties and the stabilities of these peptides toward trypsin and chymotrypsin, as well as the properties of dimers of the above nonapeptides, were examined. 相似文献
50.
Yamaguchi A Uejo F Yoda T Uchida T Tanamura Y Yamashita T Teramae N 《Nature materials》2004,3(5):337-341
A mesoporous membrane composed of nanochannels with a uniform diameter has a potential use for precise size-exclusive separation of molecules. Here, we report a novel method to form a hybrid membrane composed of silica-surfactant nanocomposite and a porous alumina membrane, by which size-selective transport of molecules across the membrane becomes possible. The nanocomposite formed inside each columnar alumina pore was an assembly of surfactant-templated silica-nanochannels with a channel diameter of 3.4 nm; the channel direction being predominantly oriented along the wall of the columnar alumina pore. Molecules could be transported across the membrane including the silica-surfactant nanocomposite with a capability of nanometre-order size-exclusive separation. Our proposed membrane system has a potential use not only for separation science, but also catalysis and chip technologies. 相似文献