全文获取类型
收费全文 | 4778篇 |
免费 | 315篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 44篇 |
综合类 | 1篇 |
化学工业 | 1036篇 |
金属工艺 | 106篇 |
机械仪表 | 119篇 |
建筑科学 | 88篇 |
矿业工程 | 7篇 |
能源动力 | 120篇 |
轻工业 | 866篇 |
水利工程 | 56篇 |
石油天然气 | 19篇 |
无线电 | 221篇 |
一般工业技术 | 656篇 |
冶金工业 | 1223篇 |
原子能技术 | 26篇 |
自动化技术 | 519篇 |
出版年
2024年 | 19篇 |
2023年 | 41篇 |
2022年 | 118篇 |
2021年 | 234篇 |
2020年 | 146篇 |
2019年 | 194篇 |
2018年 | 198篇 |
2017年 | 207篇 |
2016年 | 175篇 |
2015年 | 133篇 |
2014年 | 173篇 |
2013年 | 265篇 |
2012年 | 262篇 |
2011年 | 271篇 |
2010年 | 183篇 |
2009年 | 215篇 |
2008年 | 172篇 |
2007年 | 148篇 |
2006年 | 119篇 |
2005年 | 102篇 |
2004年 | 71篇 |
2003年 | 73篇 |
2002年 | 60篇 |
2001年 | 53篇 |
2000年 | 53篇 |
1999年 | 74篇 |
1998年 | 389篇 |
1997年 | 232篇 |
1996年 | 165篇 |
1995年 | 82篇 |
1994年 | 88篇 |
1993年 | 84篇 |
1992年 | 25篇 |
1991年 | 18篇 |
1990年 | 10篇 |
1989年 | 27篇 |
1988年 | 17篇 |
1987年 | 13篇 |
1986年 | 18篇 |
1985年 | 18篇 |
1984年 | 10篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 16篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 30篇 |
1976年 | 75篇 |
1974年 | 3篇 |
1972年 | 2篇 |
排序方式: 共有5107条查询结果,搜索用时 552 毫秒
31.
WS McDougal 《Canadian Metallurgical Quarterly》1997,157(4):1335-1336
32.
33.
Highly transparent and conducting fluorine (F) doped cadmium oxide (CdO) thin films were deposited on glass slides by the sol-gel method. The films were doped by the addition of ammonium fluoride to the precursor solution whose optimum concentration was determined. The films were fired in an open atmosphere at 350 °C and after that, exposed to annealing treatments in different atmospheres (N2, N2/H2 mixture and Ar) at the same temperature. The films were characterized by ultraviolet-visible spectroscopy, X‐ray diffraction and scanning electron microscopy. The resistivity was determined by the four probes method and current-voltage measurements in accordance with the standard Van der Pauw configuration. The CdO:F thin films obtained, showed high polycrystalline quality and high transmission in the visible region (≥ 90%), shifting towards the blue region of the absorption edge as the fluorine concentration in the precursor solution was increased from 0 to 30 at.%. The lowest resistivity values were reached for the samples with F content higher or equal to 5% and annealed in either N2 or a 96/4 N2/H2 gas mixture. Our resistivity value reached in the CdO:F layers was 4.5 × 10− 4 Ω cm (20 Ω/square). 相似文献
34.
35.
WS Ahn J Yoo SW Huh CK Kim JM Lee SE Namkoong SM Bae IP Lee 《Canadian Metallurgical Quarterly》2003,12(5):383-390
We investigated clinical efficacy of green tea extracts (polyphenon E; poly E and (-)-epigallocatechin-3-gallate [EGCG]) delivered in a form of ointment or capsule in patients with human papilloma virus (HPV) infected cervical lesions. Fifty-one patients with cervical lesions (chronic cervicitis, mild dysplasia, moderate dysplasia and severe dysplasia) were divided into four groups, as compared with 39 untreated patients as a control. Poly E ointment was applied locally to 27 patients twice a week. For oral delivery, a 200 mg of poly E or EGCG capsule was taken orally every day for eight to 12 weeks. In the study, 20 out of 27 patients (74%) under poly E ointment therapy showed a response. Six out of eight patients under poly E ointment plus poly E capsule therapy (75%) showed a response, and three out of six patients (50%) under poly E capsule therapy showed a response. Six out of 10 patients (60%) under EGCG capsule therapy showed a response. Overall, a 69% response rate (35/51) was noted for treatment with green tea extracts, as compared with a 10% response rate (4/39) in untreated controls (P<0.05). Thus, the data collected here demonstrated that green tea extracts in a form of ointment and capsule are effective for treating cervical lesions, suggesting that green tea extracts can be a potential therapy regimen for patients with HPV infected cervical lesions. 相似文献
36.
37.
Glutathione content and glutathione-dependent enzymes were measured in the liver of two fish species, gudgeon (Gobio gobio) and roach (Rutilus arcasii), from the river Bernesga (Spain) caught downstream and upstream of the waste site of several chemical industries. Animals from contaminated sites display a reduced glutathione concentration and a tendency to the decrease of glutathione S-transferase activity. Glutathione peroxidase activity was significantly elevated only in the liver of Gobio gobio and glutathione reductase activity in that of Rutilus arcasii. Our data indicate that the glutathione system constitutes a sensitive biochemical indicator of chemical pollution. Relative changes of glutathione and glutathione-dependent enzymes in both fish species suggest a different susceptibility to toxins. 相似文献
38.
BM Sandmaier R Storb KL Bennett FR Appelbaum EB Santos 《Canadian Metallurgical Quarterly》1998,91(9):3494-3502
Primary graft rejection after marrow transplantation occurs more frequently in patients receiving HLA-haploidentical compared with HLA-identical sibling transplants. Both human and experimental animal data suggest that the cells responsible for this phenomenon are either host natural killer (NK) cells, T cells, or both. To investigate the mechanisms of graft rejection, we have developed a canine model of marrow transplantation, which uses DLA-nonidentical unrelated donors in the absence of postgrafting immunosuppression. In this model most animals rejected their marrow grafts after a preparative regimen of 9.2 Gy total body irradiation (TBI). However, engraftment of DLA-nonidentical marrow can be facilitated when the recipients are pretreated with monoclonal antibody (MoAb) S5, which recognizes CD44. In this report, we extended these observations by first cloning the canine CD44 and, next, mapping the epitope recognized by S5, which was located in a region conserved among human and canine CD44 and was distinct from the hyaluronan binding domain. However, in vitro binding of S5 caused a conformational change in CD44, which allowed increased hyaluronan binding. Then, we reexamined the in vivo model of marrow transplantation and compared results with MoAb S5 to those with two other anti-CD44 MoAbs, IM7 and S3. Only MoAb S5 significantly increased the engraftment rate of DLA-nonidentical unrelated marrow, whereas the two other anti-CD44 MoAbs were ineffective. The enhanced in vivo effect was not related to differences in the MoAbs' avidities, since both S5 and IM7 had equivalent binding to CD44, but most likely related to the specific epitope that S5 recognizes. Thus, this study shows that the effect of the anti-CD44 MoAb S5 in facilitating engraftment is epitope specific and if one is to use an anti-CD44 to facilitate engraftment of marrow in humans, one cannot assume that any anti-CD44 would work. 相似文献
39.
1. Occupational health nurses need a general knowledge of psychiatric medications to work effectively with clients and their off site health providers. 2. Acquiring an understanding of the major classes of medications--anti-psychotic, anti-anxiety, anti-depressant, and antimanic--is important. 3. It is helpful to understand under what conditions and with which conditions psychotropic medications are helpful. 相似文献
40.