全文获取类型
收费全文 | 31583篇 |
免费 | 1914篇 |
国内免费 | 860篇 |
专业分类
电工技术 | 1327篇 |
技术理论 | 1篇 |
综合类 | 1379篇 |
化学工业 | 4531篇 |
金属工艺 | 1319篇 |
机械仪表 | 1319篇 |
建筑科学 | 1861篇 |
矿业工程 | 578篇 |
能源动力 | 885篇 |
轻工业 | 1640篇 |
水利工程 | 339篇 |
石油天然气 | 1345篇 |
武器工业 | 118篇 |
无线电 | 3111篇 |
一般工业技术 | 3247篇 |
冶金工业 | 7758篇 |
原子能技术 | 314篇 |
自动化技术 | 3285篇 |
出版年
2024年 | 84篇 |
2023年 | 407篇 |
2022年 | 700篇 |
2021年 | 1030篇 |
2020年 | 719篇 |
2019年 | 675篇 |
2018年 | 694篇 |
2017年 | 809篇 |
2016年 | 758篇 |
2015年 | 923篇 |
2014年 | 1239篇 |
2013年 | 1583篇 |
2012年 | 1574篇 |
2011年 | 1724篇 |
2010年 | 1399篇 |
2009年 | 1443篇 |
2008年 | 1342篇 |
2007年 | 1241篇 |
2006年 | 1350篇 |
2005年 | 1167篇 |
2004年 | 848篇 |
2003年 | 761篇 |
2002年 | 760篇 |
2001年 | 541篇 |
2000年 | 522篇 |
1999年 | 780篇 |
1998年 | 2587篇 |
1997年 | 1591篇 |
1996年 | 1170篇 |
1995年 | 715篇 |
1994年 | 607篇 |
1993年 | 575篇 |
1992年 | 215篇 |
1991年 | 210篇 |
1990年 | 160篇 |
1989年 | 149篇 |
1988年 | 164篇 |
1987年 | 131篇 |
1986年 | 114篇 |
1985年 | 94篇 |
1984年 | 36篇 |
1983年 | 31篇 |
1982年 | 61篇 |
1981年 | 56篇 |
1980年 | 48篇 |
1979年 | 17篇 |
1978年 | 21篇 |
1977年 | 162篇 |
1976年 | 326篇 |
1975年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
D Crenesse B Fossat F Craffa P Chaland J Porthe-Nibelle JC Poiree J Gugenheim 《Canadian Metallurgical Quarterly》1994,31(6):540-548
Isolated hepatocytes from the rat were used to assess the maintenance of liver cell function in relation to the composition of the preservation medium. After separation by collagenase, they were incubated in Krebs-Ringer-Bicarbonate medium (KRB), Euro-Collins (EC), or University of Wisconsin (UW) solutions. Potassium influx, cell volume, and transaminase release were measured in cells freshly separated from control livers or from livers preserved in vitro up to 12 h in these media or having undergone orthotopic liver transplantation (OLT). While ion exchange levels were retained in all media, cells shrank significantly in UW but were able to restore their volume after 3 h of liver preservation. With regard to in vivo conditions, UW appears to be the best medium to prevent edema and to maintain more stable potassium exchange and enzyme production. These results are of value for liver transplantation in humans. 相似文献
82.
Apoptosis in the failing human heart 总被引:1,自引:0,他引:1
G Olivetti R Abbi F Quaini J Kajstura W Cheng JA Nitahara E Quaini C Di Loreto CA Beltrami S Krajewski JC Reed P Anversa 《Canadian Metallurgical Quarterly》1997,336(16):1131-1141
BACKGROUND: Loss of myocytes is an important mechanism in the development of cardiac failure of either ischemic or nonischemic origin. However, whether programmed cell death (apoptosis) is implicated in the terminal stages of heart failure is not known. We therefore studied the magnitude of myocyte apoptosis in patients with intractable congestive heart failure. METHODS: Myocardial samples were obtained from the hearts of 36 patients who underwent cardiac transplantation and from the hearts of 3 patients who died soon after myocardial infarction. Samples from 11 normal hearts were used as controls. Apoptosis was evaluated histochemically, biochemically, and by a combination of histochemical analysis and confocal microscopy. The expression of two proto-oncogenes that influence apoptosis, BCL2 and BAX, was also determined. RESULTS: Heart failure was characterized morphologically by a 232-fold increase in myocyte apoptosis and biochemically by DNA laddering (an indicator of apoptosis). The histochemical demonstration of DNA-strand breaks in myocyte nuclei was coupled with the documentation of chromatin condensation and fragmentation by confocal microscopy. All these findings reflect apoptosis of myocytes. The percentage of myocytes labeled with BCL2 (which protects cells against apoptosis) was 1.8 times as high in the hearts of patients with cardiac failure as in the normal hearts, whereas labeling with BAX (which promotes apoptosis) remained constant. The near doubling of the expression of BCL2 in the cardiac tissue of patients with heart failure was confirmed by Western blotting. CONCLUSIONS: Programmed death of myocytes occurs in the decompensated human heart in spite of the enhanced expression of BCL2; this phenomenon may contribute to the progression of cardiac dysfunction. 相似文献
83.
R Wicker A Bounacer A Gascon O Brison A Sarasin HG Suárez 《Canadian Metallurgical Quarterly》1995,1264(3):254-256
A rearranged tpr-met oncogene was identified in a MNNG-transformed human Xeroderma pigmentosum (XP) cell line (ASKMN). A 2016 bp cDNA was cloned and sequenced, disclosing an ORF with a coding capacity for a 523 aa protein. The sequence of this tpr-met cDNA was very similar to that previously reported in another human MNNG-transformed cell line (MNNG-HOS). 相似文献
84.
85.
86.
熔喷生产最终产品质量的控制,对于过程优化具有重要的意义。产品质量的在线检测是过程监测与质量控制必不可少的。本文首次在熔喷系统中引入人工智能的研究方法,对熔喷非织造布的厚度与纤维直径进行在线预测。实测数据与人工神经网络的预测结果吻合较好,从而证实了人工神经网络用于模拟熔喷过程的可行性。网络的输入包括:挤出机温度、喷头温度、熔融体挤出速率、空气流率及接收距离。神经元计算的输出是纤维直径与熔喷非织布的厚度。文中进一步提出了将神经网络与专家系统相结合的研究路线,以实现熔喷过程的优化控制。 相似文献
87.
88.
本文主要根据电子整机的发展要求,从集成化、高性能和高可靠等三方面分析国外模似IC的发展,进而说明模拟IC总的发展趋势及其表现。最后指出,模拟IC正面临一个新的变革时期。 相似文献
89.
BA Stankiewicz JC Hutchins R Thomson DE Briggs RP Evershed 《Canadian Metallurgical Quarterly》1997,11(17):1884-1890
Flash pyrolysis-gas chromatography/mass spectrometry (py-GC/MS) was used to assess the quality and mechanism of protein preservation in the tissue of Iron Age bog bodies from Lindow, UK, and south-eastern Drenthe, The Netherlands. Abundant pyrolysis products of the fresh skin tissue, including 2,5-diketopiperazines of Pro-Gly, Pro-Ala, Pro-Val, Pro-Pro and Hyp, were readily assigned to specific amino acid or dipeptide moieties. Comparison of the pyrolysates of the bog-body tissues with that of modern samples revealed qualitative similarities suggesting good preservation of the collagen and non-collagenous proteins in the ancient tissues. Examination of the pyrolysates of samples of fresh calf skin, which had been treated with various vegetable tanning agents, clearly revealed markers of non-hydrolysable tannins including 1,2-benzenediol, 1,3-benzenediol and 1,2,3-benzenetriol, although chromatographic quality inevitably diminished with increasing functionalization of the compounds. Such markers were not detected in the pyrolysates of the bog-body tissues. Instead 4-isopropenylphenol, a characteristic pyrolysis product of Sphagnum moss, was detected in both solvent-extracted and base-treated samples of tissue. The presence of 4-isopropenylphenol in the pyrolysates of the bog-body tissues provides evidence that their preservation involves reactions of amino acids with sphagnum acid, and possibly other agents derived from the peat. The study constitutes the first chemical characterization of the pyrolysis products of modern and ancient collagen. 相似文献
90.
本文从智能网的基本概念入手,论述了利用 ZXJ10程控交换系统为发展智能网业务提供支持功能的技术策略以及分阶段实现的过程,并对各个阶段能够实现的业务作了简要介绍。 相似文献