全文获取类型
收费全文 | 7000篇 |
免费 | 139篇 |
国内免费 | 16篇 |
专业分类
电工技术 | 362篇 |
综合类 | 6篇 |
化学工业 | 1641篇 |
金属工艺 | 204篇 |
机械仪表 | 146篇 |
建筑科学 | 130篇 |
矿业工程 | 2篇 |
能源动力 | 197篇 |
轻工业 | 577篇 |
水利工程 | 23篇 |
石油天然气 | 2篇 |
无线电 | 693篇 |
一般工业技术 | 1193篇 |
冶金工业 | 1331篇 |
原子能技术 | 160篇 |
自动化技术 | 488篇 |
出版年
2022年 | 67篇 |
2021年 | 101篇 |
2020年 | 56篇 |
2019年 | 55篇 |
2018年 | 89篇 |
2017年 | 84篇 |
2016年 | 139篇 |
2015年 | 84篇 |
2014年 | 149篇 |
2013年 | 312篇 |
2012年 | 256篇 |
2011年 | 332篇 |
2010年 | 205篇 |
2009年 | 290篇 |
2008年 | 283篇 |
2007年 | 248篇 |
2006年 | 203篇 |
2005年 | 228篇 |
2004年 | 180篇 |
2003年 | 180篇 |
2002年 | 192篇 |
2001年 | 170篇 |
2000年 | 145篇 |
1999年 | 188篇 |
1998年 | 534篇 |
1997年 | 326篇 |
1996年 | 290篇 |
1995年 | 176篇 |
1994年 | 178篇 |
1993年 | 156篇 |
1992年 | 90篇 |
1991年 | 84篇 |
1990年 | 75篇 |
1989年 | 66篇 |
1988年 | 72篇 |
1987年 | 66篇 |
1986年 | 71篇 |
1985年 | 68篇 |
1984年 | 77篇 |
1983年 | 70篇 |
1982年 | 62篇 |
1981年 | 50篇 |
1980年 | 63篇 |
1979年 | 43篇 |
1978年 | 41篇 |
1977年 | 35篇 |
1976年 | 59篇 |
1975年 | 21篇 |
1974年 | 35篇 |
1973年 | 23篇 |
排序方式: 共有7155条查询结果,搜索用时 15 毫秒
991.
Yasuyuki Yamada Setsuo Kobayashi Kazuo Watanabe Uzo Hayashi Yasuo Yajima Hiroshi Inoue 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1987,38(1):31-39
Calluses were induced from the stem and the root tissues of horse radish plantlets. Cell aggregate selections were carried out on them to obtain a cell line with higher peroxidase activity, and the isozyme patterns of the peroxidases from the cultured cells and their utility values as a clinical diagnostic reagent were investigated. The repetition of the cell aggregate selection resulted in increases in peroxidase activities in each generation of selection; about eleven fold in the 13th generation of selection from the stem tissues and about nine fold in the 13th generation from the root tissues. One of the cell lines (N5K6-S), originally derived from the stem tissues, after selectin showed a tenfold increase in peroxidase activity within two weeks of culture in a liquid medium. The value as a clinical diagnostic reagent of peroxidases extracted from the N5K6-S cells was estimated to be equivalent to those already commercially available for the same purpose. There were significant differences in the isoenzyme patterns of the peroxidases from root tissues and those from cultured cells. From these results, the possibility of commercial production of peroxidase utilizing plant tissue and cell culture techniques was discussed. 相似文献
992.
993.
The solution technique of Mossakovskii And Rybka is used to formulate an approximate solution for axisymmetric problems in fracture mechanics. The procedure is then used to determine the stress intensity factor in a flat toroidal crack subjected to internal pressure. The maximum stress intensity factor exists at the inner edge of flat toroidal crack and therefore the crack will always tend to grow into a penny-shaped crack.
Résumé On utilise la technique proposee par Mossakovskii et Rybba pour formuler une solution approchee aux problemes de mecanique de rupture ou intervient une symetrie axiale. La procedure est ensuite appliquee a la determination du facteur d'intensite des contraintes dans le cas d'une fissure plane et toroldale soumise a pression interne. On constate que le facteur d'intensite des contraintes passe par un maximum au bord interne de la fissure plane et toroidale, ce qui laisse entendre qu'une telle fissure aura toujours tendance a prendre la forme d'une fissure en forme de disque.相似文献
994.
995.
Transmission with a BER less than 10?11 has been achieved using an injection-locking technique with a 445.8 Mbit/s RZ signal over a 170 km single-mode fibre. The injection-locking technique provides a single-longitudinal-mode optical source with a 35 dB main/side-mode power ratio and a 1.5 GHz spectral width. 相似文献
996.
PICP and PINP are considered markers of bone formation, and ICTP is considered to be a marker of bone resorption. We measured these three markers as indicators of bone metastasis of prostatic cancer, and assessed their clinical usefulness. Serum PICP, PINP and ICTP were significant higher in patients with bone metastasis than localized cancer or controlled bone metastasis. Serum PSA increased initially with the LH-RH agonist during the course of bone metastasis. All these markers were subsequently observed to increase. Change in PICP of patients with bone metastasis was slight compared to PINP during endocrine treatment. Serum PICP, PINP and ICTP reflect the extent of metastasis in bone and are useful for monitoring the response of this condition to therapy. 相似文献
997.
Yanabu S. Okubo H. Matsumoto S. Aoyagi H. Kobayashi N. 《Power Delivery, IEEE Transactions on》1987,2(1):101-106
To investigate the behavior of metallic particles in 3-phase gas insulated buses (3-phase GIB), we conducted a test by using a 3-phase 275kV, ac, 60Hz full-scale model. The test results revealed that in a 3-phase electric field, unlike in a single-phase field, metallic particles were trapped on and around the high-voltage conductors and revolved circumferentially. Computer analysis shows that it was closely related to locational and periodic changes in the electric field provided by the 3-phase GIB, and that there were points on the high-voltage conductors in which metallic particles were readily trapped. It also was proved that phenomena peculiar to the 3-phase GIB could be reproduced very well by computer simulation. 相似文献
998.
999.
Kobayashi S. Lampe R. Mittra R. Ray S. 《Antennas and Propagation, IEEE Transactions on》1981,29(5):822-824
Dielectric rod leaky-wave antennas have the property of being frequency scannable. Bounds are derived for the proper range of spacing of perturbations along the rod to avoid an intrusion upon a grating lobe when frequency scanning. In addition some experimental results are reported on sidelobe levels and polarizations in the far field for these antennas made from a material withepsilon_{r}= 2.33 at 81.5 GHz. 相似文献
1000.