全文获取类型
收费全文 | 2690篇 |
免费 | 9篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 7篇 |
综合类 | 1篇 |
化学工业 | 53篇 |
金属工艺 | 7篇 |
机械仪表 | 10篇 |
建筑科学 | 10篇 |
矿业工程 | 1篇 |
能源动力 | 8篇 |
轻工业 | 44篇 |
水利工程 | 2篇 |
无线电 | 31篇 |
一般工业技术 | 35篇 |
冶金工业 | 2454篇 |
原子能技术 | 3篇 |
自动化技术 | 35篇 |
出版年
2022年 | 4篇 |
2021年 | 7篇 |
2020年 | 6篇 |
2019年 | 5篇 |
2018年 | 4篇 |
2017年 | 7篇 |
2016年 | 5篇 |
2014年 | 3篇 |
2013年 | 29篇 |
2012年 | 8篇 |
2011年 | 15篇 |
2010年 | 10篇 |
2009年 | 4篇 |
2008年 | 8篇 |
2007年 | 11篇 |
2006年 | 6篇 |
2005年 | 20篇 |
2004年 | 7篇 |
2003年 | 13篇 |
2002年 | 7篇 |
2001年 | 6篇 |
2000年 | 6篇 |
1999年 | 64篇 |
1998年 | 815篇 |
1997年 | 431篇 |
1996年 | 292篇 |
1995年 | 163篇 |
1994年 | 119篇 |
1993年 | 155篇 |
1992年 | 16篇 |
1991年 | 22篇 |
1990年 | 27篇 |
1989年 | 24篇 |
1988年 | 23篇 |
1987年 | 30篇 |
1986年 | 24篇 |
1985年 | 21篇 |
1983年 | 8篇 |
1982年 | 12篇 |
1981年 | 11篇 |
1980年 | 20篇 |
1978年 | 5篇 |
1977年 | 53篇 |
1976年 | 159篇 |
1975年 | 3篇 |
1971年 | 2篇 |
1969年 | 1篇 |
1955年 | 2篇 |
1930年 | 2篇 |
1928年 | 1篇 |
排序方式: 共有2701条查询结果,搜索用时 15 毫秒
91.
92.
93.
Ferroelectric domain configurations in PbTiO3 and Pb(ZrxT1−x)O3 (PZT, x = 0.3 or 0.5) thin films have been studied by transmission electron microscopy. The PbTiOg and PZT thin films have
been deposited by the ionized cluster beam technique and radio frequency sputtering, respectively. The grain size in these
thin films is typically less than 0.5 μm. Lamellar 90°-domain features have been observed in both PbTiO3 and PZT (30/70) samples. The domain walls correspond to the {011} twin boundaries. La-doping and Ca-modification are shown
to affect the microstructure of the PZT films. No clear domain feature occurs in the PZT thin film that has composition near
the morphotropic phase boundary. The effects of grain sizes are briefly discussed. 相似文献
94.
95.
H Ramirez-Gil E Feldberg VM Almeida-Val AL Val 《Canadian Metallurgical Quarterly》1998,31(11):1449-1458
Karyological characteristics, i.e., diploid number, chromosome morphology and nucleolus organizer regions (NORs), biochemical characteristics, i.e., electrophoretic analysis of blood hemoglobin and the tissue enzymes lactate dehydrogenase (LDH), malate dehydrogenase (MDH), alcohol dehydrogenase (ADH), and phosphoglucose isomerase (PGI), and physiological characteristics, i.e., relative concentration of hemoglobin and intraerythrocytic concentrations of organic phosphates were analyzed for the species Callophysus macropterus collected from Marchantaria Island (white water system--Solim?es River) and Anavilhanas Archipelago (black water system--Negro River). Karyological and biochemical data did not reveal significant differences between specimens collected at the two sites. However, the relative distribution of hemoglobin bands I and III (I = 16.33 +/- 1.05 and III = 37.20 +/- 1.32 for Marchantaria specimens and I = 6.33 +/- 1.32 and III = 48.05 +/- 1.55 for Anavilhanas specimens) and levels of intraerythrocytic GTP (1.32 +/- 0.16 and 2.76 +/- 0.18 for Marchantaria and Anavilhanas specimens, respectively), but not ATP or total phosphate, were significantly different, indicating a physiological adaptation to the environmental conditions of these habitats. It is suggested that C. macropterus specimens from the two collecting sites belong to a single population, and that they adjusted some physiological characteristics to adapt to local environmental conditions. 相似文献
96.
J Bj?rheim S Lystad A Lindblom U Kressner S Westring S Wahlberg G Lindmark G Gaudernack P Ekstr?m J R?e WG Thilly AL B?rresen-Dale 《Canadian Metallurgical Quarterly》1998,403(1-2):103-112
Pefloxacin plus metronidazole versus netilmicin plus metronidazole in the prevention of nosocomial infections during contaminated surgery. Surgical prophylaxis is widely used in contaminated surgery, especially colorectal surgery. In this clinical trial the efficacy of pefloxacin 800 mg i.v. slow infusion associated to metronidazole 500 mg i.v. 1-2 hours before surgery and then metronidazole alone after 6 and 12 hours versus netilmicin 200 mg i.m. associated to metronidazole 500 mg i.v. 1-2 hours before surgery and then both after 6 and 12 hours were evaluated in 97 patients suffering by colorectal surgery. Efficacy of prophylaxis in patients was evaluated in terms of appearance of post-surgical infections (abdominal, urinary, respiratory and wound infections). In pefloxacin + metronidazole group (53 patients), two cases of wound infections (3.8%) and three cases of respiratory infections (5.8%) were observed. In netilmicin + metronidazole group (44 patients), two cases of wound infections (4.9%), three cases of urinary infections (7%), three cases of respiratory infections (7.5%) and one case of intra-abdominal infection were observed. Our data confirmed that in colorectal surgery, the association pefloxacin, drug with microbiological and pharmacokinetics characteristics suitable for prophylaxis + metronidazole, active against anaerobes pathogens, prevents post-surgical infections as well as a reference association (netilmicin + metronidazole), with the advantage of a single administration. 相似文献
97.
98.
99.
100.