全文获取类型
收费全文 | 175篇 |
免费 | 9篇 |
国内免费 | 14篇 |
专业分类
系统科学 | 7篇 |
丛书文集 | 2篇 |
教育与普及 | 2篇 |
现状及发展 | 30篇 |
研究方法 | 8篇 |
综合类 | 149篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 11篇 |
2021年 | 4篇 |
2020年 | 1篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 8篇 |
2016年 | 2篇 |
2015年 | 7篇 |
2014年 | 11篇 |
2013年 | 11篇 |
2012年 | 8篇 |
2011年 | 4篇 |
2010年 | 20篇 |
2009年 | 8篇 |
2008年 | 8篇 |
2007年 | 6篇 |
2006年 | 8篇 |
2005年 | 12篇 |
2004年 | 4篇 |
2003年 | 5篇 |
2002年 | 5篇 |
2001年 | 2篇 |
2000年 | 6篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1983年 | 3篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1976年 | 5篇 |
排序方式: 共有198条查询结果,搜索用时 31 毫秒
21.
Yun-long He Rui-dong Xu Shi-wei He Han-sen Chen Kuo Li Yun Zhu Qing-feng Shen 《矿物冶金与材料学报》2019,26(6):689-700
A new alkaline pressure oxidative leaching process(with NaNO3 as the oxidant and NaOH as the alkaline reagent)is proposed herein to remove arsenic,antimony,and lead from bismuth-rich and arsenic-rich lead anode slime for bismuth,gold,and silver enrichment.The effects of the temperature,liquid-to-solid ratio,leaching time,and reagent concentration on the leaching ratios of arsenic,antimony,and lead were investigated to identify the optimum leaching conditions.The experimental results under optimized conditions indicate that the average leaching ratios of arsenic,antimony and lead are 95.36%,79.98%,63.08%,respectively.X-ray diffraction analysis indicated that the leaching residue is composed of Bi,Bi2O3,Pb2Sb2O7,and trace amounts of NaSb(OH)6.Arsenic,antimony,and lead are thus separated from lead anode slime as Na3AsO4·10H2O and Pb2Sb2O7.Scanning electron microscopy and energy-dispersive spectrometry imaging revealed that the samples undergo appreciable changes in their surface morphology during leaching and that the majority of arsenic,lead,and antimony is removed.X-ray photoelectron spectroscopy was used to demonstrate the variation in the valence states of the arsenic,lead,and antimony.The Pb(IV)and Sb(V)content was found to increase substantially with the addition of NaNO3. 相似文献
22.
COMPARISON OF MAX—MIN APPROACH AND NN METHOD FOR RELIABILITY OPTIMIZATION OF SERIES—PARALLEL SYSTEM 总被引:2,自引:0,他引:2
Two heuristics, the max-min approach and the Nakagawa and Nakashima method, are consideredfor the redundancy allocation problem with series-parallel structure. The max-min approach canformulate the problem as an integer linear programming problem instead of an integer nonlinearproblem. This paper presents a comparison between those methods from the standpoint of solutionquality and computational complexity. The experimental results show that the max-min approach issuperior to the Nakagawa and Nakashima method in terms of solution quality in small-scale problems,but analysis of computational complexity shows that the max-min approach is inferior to other greedyheuristics. 相似文献
23.
W N Kuo J L Williams T Floyd-Jones C F Duggans D L Boone S O Smith R F Copeland 《Experientia》1979,35(8):997-998
Decreased activities of both the inhibitory modulator of adenosine 3':5'-monophosphate (cAMP)-dependent protein kinase (A-PK) as well as the stimulatory modulator of guanosine 3':5'-monophosphate (cGMP)-dependent protein kinase (G-PK) from the mouse cerebellum were noted due to the administration of excessive doses of ethanol, caffeine, and phenobarbital for up to 28 days. The dose-dependent of the inhibition of A-PK or the stimulation of G-PK was observed as a function of the amount of protein kinase modulators in the cerebellum of mice receiving different doses of ethanol. 相似文献
24.
The melanocyte differentiation program predisposes to metastasis after neoplastic transformation 总被引:1,自引:0,他引:1
Gupta PB Kuperwasser C Brunet JP Ramaswamy S Kuo WL Gray JW Naber SP Weinberg RA 《Nature genetics》2005,37(10):1047-1054
The aggressive clinical behavior of melanoma suggests that the developmental origins of melanocytes in the neural crest might be relevant to their metastatic propensity. Here we show that primary human melanocytes, transformed using a specific set of introduced genes, form melanomas that frequently metastasize to multiple secondary sites, whereas human fibroblasts and epithelial cells transformed using an identical set of genes generate primary tumors that rarely do so. Notably, these melanomas have a metastasis spectrum similar to that observed in humans with melanoma. These observations indicate that part of the metastatic proclivity of melanoma is attributable to lineage-specific factors expressed in melanocytes and not in other cell types analyzed. Analysis of microarray data from human nevi shows that the expression pattern of Slug, a master regulator of neural crest cell specification and migration, correlates with those of other genes that are important for neural crest cell migrations during development. Moreover, Slug is required for the metastasis of the transformed melanoma cells. These findings indicate that melanocyte-specific factors present before neoplastic transformation can have a pivotal role in governing melanoma progression. 相似文献
25.
26.
27.
Summary Otobanon obtained fromn-hexane extract ofMyristica simarum A. DC. was elucidated as 1-oxo-otobain by the physical spectra and chemical degradation.Acknowledgment. The authors are indebted to Chemical Research Center for financial support under the project No. CRC-6203, which supported by the National Council on Science Development of China. 相似文献
28.
固态法酿造苦荞白酒工艺初探 总被引:1,自引:1,他引:0
以苦荞麦为原料,采用传统的固态发酵法酿造苦荞白酒,并对苦荞白酒的固态发酵工艺进行了优化研究.实验结果表明:苦荞麦粉100 g,稻壳添加量18%,加酒曲量10%,打量水用量35%,常温培菌糖化48 h,密封发酵20 d,酒醅的酒精含量可达到7.8%,通过蒸馏可得到酒精度为36%(v/v)的原酒50 mL. 相似文献
29.
30.
以流体力学理论、轧制理论及Hill的特性曲线微分方程解法为基础,建立了轧制界面考虑入口板带厚度、轧辊半径发生波动下非稳态油膜厚度分布动力学模型,提出了油膜波动系数来反映界面油膜厚度绝对波动,并进行了相应的仿真分析.结果表明:非稳态条件下轧制界面油膜厚度分布性态会随时间不同而发生变化,不同时刻最小油膜厚度也会发生变化;界面油膜厚度的绝对波动会随着入口板带厚度、轧辊半径非均匀程度加剧而变大,而入口板带厚度、轧辊半径的变化频率对界面油膜厚度的绝对波动影响较小. 相似文献