全文获取类型
收费全文 | 1604篇 |
免费 | 16篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 6篇 |
综合类 | 9篇 |
化学工业 | 33篇 |
金属工艺 | 9篇 |
机械仪表 | 5篇 |
建筑科学 | 4篇 |
矿业工程 | 2篇 |
能源动力 | 2篇 |
轻工业 | 26篇 |
水利工程 | 1篇 |
石油天然气 | 4篇 |
武器工业 | 1篇 |
无线电 | 11篇 |
一般工业技术 | 7篇 |
冶金工业 | 1456篇 |
自动化技术 | 52篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2019年 | 2篇 |
2017年 | 3篇 |
2016年 | 1篇 |
2015年 | 9篇 |
2014年 | 13篇 |
2013年 | 8篇 |
2012年 | 7篇 |
2011年 | 8篇 |
2010年 | 8篇 |
2009年 | 10篇 |
2008年 | 4篇 |
2007年 | 10篇 |
2006年 | 4篇 |
2005年 | 41篇 |
2004年 | 4篇 |
2003年 | 8篇 |
2002年 | 6篇 |
2001年 | 6篇 |
2000年 | 1篇 |
1999年 | 41篇 |
1998年 | 416篇 |
1997年 | 257篇 |
1996年 | 162篇 |
1995年 | 87篇 |
1994年 | 81篇 |
1993年 | 82篇 |
1992年 | 10篇 |
1991年 | 19篇 |
1990年 | 13篇 |
1989年 | 22篇 |
1988年 | 25篇 |
1987年 | 23篇 |
1986年 | 17篇 |
1985年 | 26篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 7篇 |
1981年 | 10篇 |
1980年 | 18篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 37篇 |
1976年 | 99篇 |
1975年 | 7篇 |
1974年 | 1篇 |
1966年 | 2篇 |
1965年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有1628条查询结果,搜索用时 15 毫秒
51.
AP Nimmagadda BJ Burri T Neidlinger WA O'Brien MB Goetz 《Canadian Metallurgical Quarterly》1998,27(5):1311-1313
We conducted a pilot, open-label study to assess the effect of short-term beta-carotene administration (180 mg/d with meals for 4 weeks) on the plasma human immunodeficiency virus (HIV) RNA levels and CD4+ lymphocyte counts in 21 HIV-infected patients. We found that plasma HIV RNA levels and CD4+ lymphocyte counts did not change following this short course of beta-carotene supplementation. Patients with lower serum concentrations of beta-carotene before supplementation were no more likely to have an increase in their CD4+ lymphocyte count or plasma HIV RNA copy number than were those with higher concentrations. No correlation was found between pre- or postsupplementation beta-carotene or vitamin A concentrations and pre- or postsupplementation CD4+ lymphocyte counts or plasma HIV RNA titers. This study provides no support for beta-carotene supplementation for HIV-infected subjects with normal baseline serum levels of beta-carotene and vitamin A. 相似文献
52.
为了阐明磨石研磨加工层对高碳铬轴承钢JIS SUJ2超长寿命疲劳行为的影响,分别使用经砂纸研磨和电解研磨的砂漏形试样,在室温空气环境下进行旋转弯曲疲劳试验.砂纸研磨试样被除去部分磨石研磨层,电解研磨试样被除去了全部的磨石研磨层.结果表明,两种试样的S-N曲线由位于短寿命区的表面破坏模式和位于长寿命区的内部破坏模式的两条组成,表面破坏模式的S-N曲线受表面粗糙度和表面压缩残余应力的影响.内部破坏模式的S-N曲线不受表面条件的影响,是材料固有的特性.砂纸研磨试样表面破坏模式的疲劳极限最高,是电解研磨试样1.11倍和磨石研磨的1.20倍.表面压缩残余应力对表面破坏模式疲劳极限的影响可以用修正Goodman图表示.还讨论裂纹的萌生和扩展条件,推定超长寿命的疲劳极限. 相似文献
53.
DM Tomkins SV Otton N Joharchi T Berns D Wu WA Corrigall EM Sellers 《Canadian Metallurgical Quarterly》1997,8(2-3):223-235
In rats, amphetamine (AMP) conversion to 4-OH-AMP is metabolized by CYP2D1, the rat equivalent of the human enzyme CYP2D6. To determine the impact of impaired AMP metabolism on its behavioural effects, AMP-induced hyperactivity, AMP discrimination and AMP self-administration were examined in male Wistar rats with or without pretreatment with the CYP2D1 inhibitors quinine and budipine. In vivo, quinine (20 mg/kg) and budipine (10 mg/kg) increased the plasma area under the curve of AMP 4-fold and 3.6-fold respectively, and decreased the plasma levels of 4-OH-AMP, 3-fold and 8.6-fold, confirming that the doses used suppressed CYP2D1 activity. Both inhibitors prolonged AMP-induced hyperactivity (0.3 mg/kg) and prolonged the duration of AMP-appropriate responding for periods of up to 90 min post-AMP administration in a drug discrimination procedure. In rats given a preload dose of AMP (0.8 mg/kg) 3 h prior to the self-administration test session, CYP2D1 inhibition resulted in fewer AMP infusions being taken compared with rats receiving the AMP preload dose alone. These studies indicate that AMP is responsible for the behavioural effects seen in rats and that a rat phenocopy model of the human CYP2D6 deficiency state can be produced by CYP2D1 inhibitors. 相似文献
54.
J Gérain D Liénard S Pampallona M Baumgartner C Rüegg WA Buurman A Eggermont F Lejeune 《Canadian Metallurgical Quarterly》1997,9(12):1034-1042
Isolated limb perfusion (ILP) with high dose tumour necrosis factor (TNF), interferon gamma and melphalan (TIM) is an efficient treatment for patients with regionally advanced melanoma and sarcoma. In 44 patients, we determined the kinetics of soluble TNF receptors (sTNF-RI and RII) plasma concentrations, and correlated them with systemic TNF and interleukin 6 (IL-6) levels and shock. Seven patients treated conventionally by ILP without cytokine served as controls. Elevated levels of both sTNF-Rs were observed within 30 min after beginning of the TIM-ILP. A first peak of sTNF-Rs levels was observed 3 h after ILP and was followed by a rapid decrease reaching a nadir at 12-14 h post ILP. This first peak was followed by a second, long-lasting elevation of both sTNF-Rs levels persisting for 4 to 5 days after TIM-ILP. Patients treated by ILP without TNF/interferon gamma (IFN-gamma) had no detectable increase in either sTNF-Rs or in circulating TNF, demonstrating that the release of TNF-Rs was dependent upon the administration of TNF/IFN-gamma. High plasma levels of TNF and IL-6 were observed in patients that had more than 5% leakage during the TIM-ILP, but no significant correlation between TNF levels and the peak values of both sTNF-Rs was observed. The levels of TNF and IL-6 were, however, significantly related to each other. TNF systemic levels, but not sTNF-Rs concentrations, correlated significantly with the severity of the shock observed after TIM-ILP. Patients in which sTNF-RII concentration was in excess over circulating TNF, had no shock or grade I shock only, suggesting that sTNF-RII may play a protective, although limited, role in inhibiting activity of circulating TNF. 相似文献
55.
56.
57.
58.
The role of the blood-brain barrier transporter PTS-1 in regulating concentrations of methionine enkephalin in blood and brain 总被引:1,自引:0,他引:1
The entrainment of the circadian rhythm of locomotor activity was studied in the field mouse Mus booduga in order to examine the relationship between the free-running period (tau) and minimum tolerable light pulse interval of the skeleton photoperiods. The animals were entrained under three different light/dark (LD) schedules, each out of phase with the other. They were then subjected to various skeleton photoperiods created by two repeated light pulses (LPs) interrupting darkness. Animals that selected the shorter interval between the LPs as their "subjective night" had significantly shorter tau (23.13 +/- 0.38 h) as compared to those that selected the longer dark interval as subjective night (tau = 23.87 +/- 0.18 h). When the longer dark interval was 12 h, animals selecting that interval as their subjective night included both long-tau and short-tau individuals. When both intervals of darkness were of equal duration, no difference in the selection of subjective night was seen between short and long-tau animals. When the "dusk" LP for the animals that selected the longer dark interval as subjective night was advanced by 2 h to create a new skeleton photoperiod, the number of transient cycles appearing before steady-state entrainment was found to depend on the duration of the photoperiods. When the night defined by the two LPs was reduced below 6h, a dramatic "phase jump" in the activity rhythm was observed, and the initial phase relationship was restored after a relaxation in the night duration. We observed considerable interindividual variation in the "minimum tolerable light pulse interval of skeleton photoperiods," which we suggest may be due to the observed variation in tau among individuals. 相似文献
59.
假定股票价格过程服从分数跳-扩散过程,利率满足分数Vasicek利率模型,利用分数跳-扩散过程理论以及保险精算方法,讨论了创新重置期权的定价问题,获得了创新重置看涨期权定价公式,推广了关于创新重置期权定价的相关结果. 相似文献
60.
首先通过体外模拟唾液-胃液-肠液应激实验研究乳杆菌的耐消化应激能力,然后研究其对肠道黏蛋白和Caco-2细胞的黏附及抑制肠道病原菌黏附的能力,最后探讨消化应激对乳杆菌黏附能力的影响。结果表明,副干酪乳杆菌W125、m111和发酵乳杆菌146在依次经过模拟唾液-胃液-肠液应激后存活率分别为2.70%、3.53%及11.15%,活菌数分别为7.46、7.24(lg(CFU/mL))及8.35(lg(CFU/mL)),且对黏蛋白和Caco-2细胞的黏附率显著高于其他菌株(P<0.05),分别为15.67%、8.75%、8.38%和11.47%、21.34%、10.44%;3株菌株均可通过排除、竞争和替代的方式抑制大肠杆菌CICC10899和沙门菌WX29对肠道的黏附,黏附抑制率均大于13.51%;消化应激显著降低了副干酪乳杆菌W125和发酵乳杆菌146对肠道的黏附能力(P<0.05),但显著增加了副干酪乳杆菌m111的黏附能力(P<0.05),黏附率由17.60%增加到30.45%,且主要黏附素由消化应激前的表层蛋白变为应激后的蛋白和多糖;消化应激前后副干酪乳杆菌m111均... 相似文献