全文获取类型
收费全文 | 2968篇 |
免费 | 9篇 |
专业分类
电工技术 | 4篇 |
综合类 | 4篇 |
化学工业 | 107篇 |
金属工艺 | 6篇 |
机械仪表 | 12篇 |
建筑科学 | 24篇 |
能源动力 | 4篇 |
轻工业 | 62篇 |
水利工程 | 9篇 |
石油天然气 | 1篇 |
无线电 | 60篇 |
一般工业技术 | 114篇 |
冶金工业 | 2515篇 |
原子能技术 | 1篇 |
自动化技术 | 54篇 |
出版年
2023年 | 5篇 |
2021年 | 9篇 |
2019年 | 9篇 |
2018年 | 7篇 |
2017年 | 7篇 |
2016年 | 7篇 |
2014年 | 6篇 |
2013年 | 44篇 |
2012年 | 17篇 |
2011年 | 33篇 |
2010年 | 14篇 |
2009年 | 15篇 |
2008年 | 12篇 |
2007年 | 19篇 |
2006年 | 15篇 |
2005年 | 19篇 |
2004年 | 14篇 |
2003年 | 13篇 |
2002年 | 6篇 |
2001年 | 11篇 |
2000年 | 9篇 |
1999年 | 87篇 |
1998年 | 789篇 |
1997年 | 444篇 |
1996年 | 313篇 |
1995年 | 175篇 |
1994年 | 134篇 |
1993年 | 158篇 |
1992年 | 24篇 |
1991年 | 28篇 |
1990年 | 34篇 |
1989年 | 40篇 |
1988年 | 40篇 |
1987年 | 34篇 |
1986年 | 34篇 |
1985年 | 28篇 |
1983年 | 16篇 |
1982年 | 13篇 |
1981年 | 19篇 |
1980年 | 26篇 |
1979年 | 5篇 |
1978年 | 12篇 |
1977年 | 46篇 |
1976年 | 109篇 |
1975年 | 10篇 |
1974年 | 6篇 |
1972年 | 4篇 |
1970年 | 7篇 |
1955年 | 4篇 |
1937年 | 5篇 |
排序方式: 共有2977条查询结果,搜索用时 46 毫秒
21.
22.
MJ Kania SD Keeling SP McGorray TT Wheeler GJ King 《Canadian Metallurgical Quarterly》1996,66(6):423-432
This study examined risk factors associated with incisor injury in 3396 third and fourth grade school children in Alachua County, Florida. One of six orthodontists completed a standardized examination form for each child to assess severity of incisor injury, gender, age, race, skeletal relationships, morphologic malocclusion, incisor exposure, interlabial gap, TMJ sounds, chin trauma, and history of lower facial trauma. One in five (19.2%) exhibited some degree of incisor injury. This was limited to a single tooth in 73.1% of those with injury, while enamel injury predominated (89.4%). The majority of the injuries (75.4%) were localized in the maxillary arch, with central incisors the most frequently traumatized. Chi-square tests of association indicated that gender, race, school, orthodontist, history of lower facial trauma, chin trauma, profile, and maxillary and mandibular horizontal positions were associated with incisor injury (P < 0.05). Wilcoxon rank sum tests identified differences in age, overjet, time of screening, and interlabial gap between those with and without injury (P < 0.05). Results of logistic regression analyses indicated risk of incisor injury was greater for children who had a prognathic maxilla, a history of trauma, were older, were male, and had greater overjet and mandibular anterior spacing. 相似文献
23.
J Randerson L Cawkwell A Jack JA Child F Lewis N Hall P Johnson P Evans S Barrans GJ Morgan 《Canadian Metallurgical Quarterly》1996,93(1):160-162
Fluorescent polymerase chain reaction (PCR) was used to assay 12 microsatellite markers (APC x 2, DCC, P53 x 2, RB1, NM23, WT1, D6S260, D6S262, D6S281 and TNFa) to look for evidence of microsatellite instability in 40 cases of follicle centre cell lymphoma (FCC). Evidence of novel alleles seen in the tumour tissue but not the normal uninvolved tissue was seen in seven cases (17%). In only two of these cases (5%) was more than one locus involved but in these cases multiple affected loci were seen (4/12 and 7/12 respectively). The detection of microsatellite instability indicates a DNA repair defect such as that which would be predicted to occur in cells with mutated mismatch repair genes, a novel finding in FCC lymphoma. 相似文献
24.
25.
1. alpha-toxin of Staphylococcus aureus readily permeabilized rat uterine smooth muscle after incubation for a short time. 2. The permeabilized muscle responded to Ca2+ dose-dependently and repeatedly in the same manner. 3. The threshold concentration of Ca2+ for contraction was 0.1-0.3 microM and the maximal contraction was achieved with 1 or 3 microM Ca2+. 4. GTP gamma S or GTP augmented the contractile response to Ca2+. 5. GDP beta S or GDP suppressed the contraction. 6. The role of GTP-binding protein in sensitization of Ca(2+)-induced contractile response of smooth muscle is discussed. 相似文献
26.
27.
TL Holyoake MG Freshney L McNair AN Parker PJ McKay WP Steward E Fitzsimons GJ Graham IB Pragnell 《Canadian Metallurgical Quarterly》1996,87(11):4589-4595
The characterization of many cytokines involved in the control of hematopoiesis has led to intense investigation into their potential use in ex vivo culture to expand progenitor numbers. We have established the optimum ex vivo culture conditions that allow substantial amplification of transient engrafting murine stem cells and which, simultaneously, augment the ability to sustain serial bone marrow transplantation (BMT). Short-term incubation of unfractionated BM cells in liquid culture with stem cell factor (SCF) and interleukin-11 (IL-11) produced a 50-fold amplification of clonogenic multipotential progenitors (CFU-A). Following such ex vivo expansion, substantially fewer cells were required to rescue lethally irradiated mice. When transplanted in cell doses above threshold for engraftment, BM cells expanded ex vivo resulted in significantly more rapid hematopoietic recovery. In a serial transplantation model, unmanipulated BM was only able to consistently sustain secondary BMT recipients, but BM expanded ex vivo has sustained quaternary BMT recipients that remain alive and well more than 140 days after 4th degree BMT. These results show augmentation of both short-term recovery posttransplant and the ability to serially transplant marrow by preincubation in culture with SCF and IL-11. 相似文献
28.
WJ Schnedl EC Reisinger RW Lipp M Uggowitzer HJ Mischinger P Fickert GJ Krejs 《Canadian Metallurgical Quarterly》1996,23(3):220-223
We reported an operative case of bilateral coronary artery fistulae to pulmonary artery associated with a giant saccular aneurysm, the largest of which measured 30 x 30 mm. The patient was a 75 year old female who had anginal pain due to coronary steal phenomenon. A continuous murmur was detected. After establishing total cardiopulmonary bypass, two distal orifices of the fistula connected to the main pulmonary artery were closed with 5-0 polypropylene plegeted sutures. Aneurysmorrhaphy was then performed for giant saccular aneurysm. Postoperative course was uneventful. 相似文献
29.
30.