全文获取类型
收费全文 | 3092篇 |
免费 | 2篇 |
专业分类
电工技术 | 1篇 |
综合类 | 2篇 |
化学工业 | 11篇 |
金属工艺 | 7篇 |
机械仪表 | 6篇 |
建筑科学 | 2篇 |
能源动力 | 9篇 |
轻工业 | 8篇 |
水利工程 | 2篇 |
石油天然气 | 3篇 |
无线电 | 18篇 |
一般工业技术 | 14篇 |
冶金工业 | 3005篇 |
原子能技术 | 1篇 |
自动化技术 | 5篇 |
出版年
2022年 | 3篇 |
2020年 | 3篇 |
2018年 | 1篇 |
2017年 | 4篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 10篇 |
2012年 | 4篇 |
2011年 | 3篇 |
2010年 | 4篇 |
2009年 | 2篇 |
2008年 | 1篇 |
2007年 | 7篇 |
2006年 | 3篇 |
2005年 | 4篇 |
2004年 | 2篇 |
2003年 | 2篇 |
2002年 | 10篇 |
2001年 | 6篇 |
2000年 | 2篇 |
1999年 | 87篇 |
1998年 | 831篇 |
1997年 | 456篇 |
1996年 | 295篇 |
1995年 | 189篇 |
1994年 | 125篇 |
1993年 | 201篇 |
1992年 | 37篇 |
1991年 | 41篇 |
1990年 | 41篇 |
1989年 | 56篇 |
1988年 | 45篇 |
1987年 | 50篇 |
1986年 | 48篇 |
1985年 | 50篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 13篇 |
1981年 | 34篇 |
1980年 | 32篇 |
1979年 | 2篇 |
1978年 | 7篇 |
1977年 | 106篇 |
1976年 | 246篇 |
1975年 | 14篇 |
1963年 | 1篇 |
1955年 | 4篇 |
排序方式: 共有3094条查询结果,搜索用时 31 毫秒
41.
CE Alpers CC Tsai KL Hudkins Y Cui L Kuller RE Benveniste JM Ward WR Morton 《Canadian Metallurgical Quarterly》1997,13(5):413-424
Focal and segmental glomerulosclerosis (FSG) with endothelial tubuloreticular inclusions (TRIs) is the typical lesion of human HIV-associated glomerulopathy. Autopsy studies showed the presence of FSG in 3 of 15 macaques dying 15-120 weeks after experimental infection with a simian immunodeficiency virus (SIVMne). Ultrastructural studies generally revealed numerous endothelial TRIs (also present in normals), mesangial expansion, and evidence of mesangial cell injury. One additional animal had a small-vessel polyarteritis with a proliferative and focally crescentic glomerulonephritis; seven animals had mild, multifocal interstitial nephritis. All animals had documented viremia after infection; 14 of 15 developed antibodies to SIV postinoculation. Additional postmortem findings included severe enterocolitis, encephalitis, and opportunistic infections. In contrast, autopsy studies of macaques infected with a type D simian retrovirus (SAIDS-D/Washington, SRV-2) for similar periods of time (n = 40) showed no evidence of FSG. One SRV-infected animal had a mild proliferative glomerulonephritis. These studies indicate SIV-infected primates may provide a relevant model for study of human HIV-associated nephropathy. They also indicate the variable pathology that can be seen in primate infections of distinct retrovirus types, each of which produces a simian immunodeficiency state that resembles human AIDS. 相似文献
42.
43.
44.
We conducted a retrospective review of 155 spinal operations at our institution to determine the efficacy of intraoperative salvage. Addition of intraoperative salvage had little effect on the success of a preoperative autologous donation program. Only patients with operative blood loss > 2,000 ml (12% of patients) benefited from this expensive source of autologous blood. The technique tended to be most effective in children aged 16-18 years. Use of intraoperative salvage for all pediatric spinal procedures is neither necessary nor cost effective. 相似文献
45.
RB Jones PR Pomrehn RE Mecklenburg EA Lindsay M Manley JK Ockene 《Canadian Metallurgical Quarterly》1993,124(9):92-104; discussion 106-8
The National Cancer Institute's program to help dentists reduce tobacco use among their patients is part of the Community Intervention Trial for Smoking Cessation, a 22-community, randomly controlled trial of an intervention program for smoking cessation. Results of COMMIT baseline surveys of dentists in the 11 intervention communities are presented. 相似文献
46.
47.
Molecular analysis of cellulose biosynthesis in Arabidopsis 总被引:1,自引:0,他引:1
T Arioli L Peng AS Betzner J Burn W Wittke W Herth C Camilleri H H?fte J Plazinski R Birch A Cork J Glover J Redmond RE Williamson 《Canadian Metallurgical Quarterly》1998,279(5351):717-720
Cellulose, an abundant, crystalline polysaccharide, is central to plant morphogenesis and to many industries. Chemical and ultrastructural analyses together with map-based cloning indicate that the RSW1 locus of Arabidopsis encodes the catalytic subunit of cellulose synthase. The cloned gene complements the rsw1 mutant whose temperature-sensitive allele is changed in one amino acid. The mutant allele causes a specific reduction in cellulose synthesis, accumulation of noncrystalline beta-1,4-glucan, disassembly of cellulose synthase, and widespread morphological abnormalities. Microfibril crystallization may require proper assembly of the RSW1 gene product into synthase complexes whereas glucan biosynthesis per se does not. 相似文献
48.
In enteric bacteria, chromosomally encoded permeases specific for lactose, maltose, and melibiose are allosterically regulated by the glucose-specific enzyme IIA of the phosphotransferase system. We here demonstrate that the plasmid-encoded raffinose permease of enteric bacteria is similarly subject to this type of inhibition. 相似文献
49.
The effects of not breastfeeding on mortality due to diarrhea and acute lower respiratory infection (ALRI) in children under 2 years of age were examined using data from a 1988-1991 longitudinal study of 9,942 children in Metro Cebu, The Philippines. Cox regression methods were used to study the magnitude of the risks, possible interactions with birth weight and nutritional status, and the effect of additional confounding factors. Not breastfeeding had a greater effect on diarrheal mortality than on ALRI mortality. In the first 6 months of life, failing to initiate breastfeeding or ceasing to breastfeed resulted in an 8- to 10-fold increase in the rate of diarrheal mortality. The rate of mortality associated with both ALRI and diarrhea was increased nearly six times by not breastfeeding, but the rate of ALRI mortality alone was not increased. The data also suggested that the risk of mortality associated with not breastfeeding was greater for low birth weight infants and infants whose mothers had little formal education. After age 6 months, the protective effects of breastfeeding dropped dramatically. These findings underscore the importance of promoting breastfeeding, especially during the first 6 months of life, and of targeting high risk groups such as low birth weight babies and those of low socioeconomic status. 相似文献
50.
We recently diagnosed subcutaneous fat necrosis in a newborn female infant using fine needle aspiration cytology. The neonate had perinatal asphyxia and her mother a difficult labor, but otherwise the neonate was well developed and healthy and within a few days developed well-defined areas of subcutaneous induration all over. On cytologic examination of the aspirated material, many necrotizing fat cells were found with refractile, needle-shaped crystals arranged in a sheaflike or starburst pattern. Subcutaneous fat necrosis of the newborn is uncommon today, and although the histologic findings from excised tissue are known, this appears to be the first case in which the diagnosis was possible from a sample of fine needle aspirate. 相似文献