全文获取类型
收费全文 | 98082篇 |
免费 | 7866篇 |
国内免费 | 3831篇 |
专业分类
电工技术 | 5020篇 |
技术理论 | 6篇 |
综合类 | 5631篇 |
化学工业 | 16645篇 |
金属工艺 | 5218篇 |
机械仪表 | 5700篇 |
建筑科学 | 6328篇 |
矿业工程 | 2886篇 |
能源动力 | 2870篇 |
轻工业 | 6175篇 |
水利工程 | 1515篇 |
石油天然气 | 4886篇 |
武器工业 | 665篇 |
无线电 | 12992篇 |
一般工业技术 | 12693篇 |
冶金工业 | 5766篇 |
原子能技术 | 1020篇 |
自动化技术 | 13763篇 |
出版年
2024年 | 453篇 |
2023年 | 1557篇 |
2022年 | 2669篇 |
2021年 | 3736篇 |
2020年 | 2860篇 |
2019年 | 2529篇 |
2018年 | 2784篇 |
2017年 | 3038篇 |
2016年 | 2754篇 |
2015年 | 3512篇 |
2014年 | 4399篇 |
2013年 | 5691篇 |
2012年 | 5998篇 |
2011年 | 6707篇 |
2010年 | 5470篇 |
2009年 | 5360篇 |
2008年 | 5286篇 |
2007年 | 5007篇 |
2006年 | 5203篇 |
2005年 | 4268篇 |
2004年 | 3215篇 |
2003年 | 2976篇 |
2002年 | 2971篇 |
2001年 | 2606篇 |
2000年 | 2361篇 |
1999年 | 2400篇 |
1998年 | 2472篇 |
1997年 | 1943篇 |
1996年 | 1718篇 |
1995年 | 1423篇 |
1994年 | 1217篇 |
1993年 | 899篇 |
1992年 | 668篇 |
1991年 | 585篇 |
1990年 | 481篇 |
1989年 | 410篇 |
1988年 | 352篇 |
1987年 | 268篇 |
1986年 | 225篇 |
1985年 | 185篇 |
1984年 | 140篇 |
1983年 | 95篇 |
1982年 | 98篇 |
1981年 | 73篇 |
1980年 | 101篇 |
1979年 | 58篇 |
1978年 | 66篇 |
1977年 | 63篇 |
1976年 | 90篇 |
1975年 | 52篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
A new image coding algorithm using variable-rate side-matchfinite-state vector quantization 总被引:1,自引:0,他引:1
Tung-Shou Chen Chin-Chen Chang 《IEEE transactions on image processing》1997,6(8):1185-1187
A new side-match vector quantizer, NewSMVQ, is presented in this paper. Three techniques are incorporated to improve the image quality, encoding speed, and bit rate for compressing images. The experimental result shows: i) the encoding time of NewSMVQ is almost 7 times faster than that of SMVQ (ordinary fixed-rate side-match vector quantizer) and CSMVQ (variable-rate SMVQ) and ii) NewSMVQ outperforms SMVQ and CSMVQ in terms of bit rate versus image quality tradeoffs. 相似文献
22.
BS Kendrick BS Chang T Arakawa B Peterson TW Randolph MC Manning JF Carpenter 《Canadian Metallurgical Quarterly》1997,94(22):11917-11922
Understanding the mechanism for sucrose-induced protein stabilization is important in many diverse fields, ranging from biochemistry and environmental physiology to pharmaceutical science. Timasheff and Lee [Lee, J. C. & Timasheff, S. N. (1981) J. Biol. Chem. 256, 7193-7201] have established that thermodynamic stabilization of proteins by sucrose is due to preferential exclusion of the sugar from the protein's surface, which increases protein chemical potential. The current study measures the preferential exclusion of 1 M sucrose from a protein drug, recombinant interleukin 1 receptor antagonist (rhIL-1ra). It is proposed that the degree of preferential exclusion and increase in chemical potential are directly proportional to the protein surface area and that, hence, the system will favor the protein state with the smallest surface area. This mechanism explains the observed sucrose-induced restriction of rhIL-1ra conformational fluctuations, which were studied by hydrogen-deuterium exchange and cysteine reactivity measurements. Furthermore, infrared spectroscopy of rhlL-1ra suggested that a more ordered native conformation is induced by sucrose. Electron paramagnetic resonance spectroscopy demonstrated that in the presence of sucrose, spin-labeled cysteine 116 becomes more buried in the protein's interior and that the hydrodynamic diameter of the protein is reduced. The preferential exclusion of sucrose from the protein and the resulting shift in the equilibrium between protein states toward the most compact conformation account for sucrose-induced effects on rhIL-1ra. 相似文献
23.
要提高曲线轮廓汉字的还原质量, 需要在字形还原时采用网格适配技术本文介绍了网格适配的基本原理, 并在分析汉字字形还原失真现象的基础上, 给出了我们自己设计并实现的适合于曲线轮廓汉字特点的二种网格适配方法, 即动态的补象素算法和曲线轮廓汉字的技术 相似文献
24.
大系统分散鲁棒容错控制的进展及主要成果 总被引:1,自引:0,他引:1
综述了近20年来关联大系统分散鲁棒容错控制的研究动态及取得的主要成果。说明了统一地研究分散鲁棒容错控制的必要性。在分散控制、鲁棒控制和容错控制研究领域内,分析了各种设计方法的主导思想及实质;指出了这些研究成果的意义与存在的问题。文中着重论述了分散、鲁棒、容错控制研究方法的发展途径。 相似文献
25.
SF Zakharov SH Kwok H Sokoloff HT Chang SP Radko A Chrambach 《Canadian Metallurgical Quarterly》1998,19(10):1625-1630
An automated gel electrophoresis apparatus, recently available commercially, allows one to follow the band during electrophoresis in real time, and lends itself therefore to an evaluation of bandwidth as a function of migration time (the dispersion coefficient), resolution and band shape. These determinations assume the constancy of band area with migration time and at various gel concentrations. The purpose of the present study was to verify these assumptions. Representative proteins and sodium dodecyl sulfate (SDS)-proteins, either natively fluorescent or fluorescein carboxylate labeled, were found to exhibit band areas which approach constancy as a function of migration time in both agarose and polyacrylamide gel electrophoresis, provided that (i) the protein concentration under the band was low enough to obviate self-quenching of fluorescence; (ii) the separation of the protein of interest from contaminants had progressed sufficiently during the time at which band areas were measured; (iii) the baseline under the peak was sufficiently well defined. However, band areas decrease with increasing gel concentration. Protein peaks exhibited leading and trailing tails. The ratio of the combined tail area to total area appeared to be near-constant at varying migration times. However, that ratio increases with increasing gel concentration. The tail area does not appear to be an artifact of fluorometric detection since it is reproduced upon fluorimetric analysis of the protein eluted from gel slices after electrophoresis. However, it may be due to photochemical destruction under the conditions of repetitive fluorometric peak detection. 相似文献
26.
Early patterning of prelimbic cortical axons to the striatal patch compartment in the neonatal mouse
LK Nisenbaum SM Webster SL Chang KD McQueeney JJ LoTurco 《Canadian Metallurgical Quarterly》1998,20(2-3):113-124
The striatum receives excitatory input from virtually the entire cerebral cortex. In the adult, this input is segregated into two functionally distinct compartments of the striatum, the patch (striosome) and matrix regions. This study determined whether the patterning of corticostriatal afferents from the prelimbic cortex to the striatal patch compartment develops during the early period of collateral formation or instead at the time of peak synaptogenesis. Initial formation of corticostriatal axon collaterals was observed by embryonic day (E) 19. Quantification of corticostriatal collaterals revealed a significant increase in the number and complexity of collateral branches at postnatal day 6 as compared to E19. Concomitant with the increase in collateral branching, a heterogeneous pattern of collateralization consisting of parallel rows of corticostriatal collaterals was observed in the medial striatum. In addition to the rows, clusters of corticostriatal axons occurred more laterally. These clusters colocalized with patches of dense tyrosine hydroxylase-positive fibers, a marker for the striatal patch compartment in the neonatal mouse. Together, these data indicate that corticostriatal patterning occurs during the period of early axon collateralization resulting in a segregation of corticostriatal axon collaterals from the prelimbic cortex to the striatal patch compartment. 相似文献
27.
28.
本文通过大量的单因素和多因素试验,确定了新型耐嚼糖果的制造工艺参数,研制出一种咀嚼时间长,口感类似胶姆糖,有较好的粘弹性和硬度,可被人体完全消化代谢的新型糖果。 相似文献
29.
通过以企业营销控制的四种方式 :年度计划控制 ;盈利率控制 ;效率控制 ;战略控制的介绍分析 ,阐述在中国涂料企业进行营销控制的必要性。 相似文献
30.
石油测井仪器可靠性指标探讨 总被引:5,自引:1,他引:4
在分析常用可靠性指标及其应用现状的基础上,根据可靠性理论及石油测井仪器的特点。提出了石油测井仪器的可靠性模型。在探讨常用可靠性指标对石油测井仪器适用性的同时,提出将平衡稳定工作时间NWTURE和免维修测井井次NOLWNM作为石油测井仪器可靠性指标的思想;探讨了获取可靠性指标的途径。给出了推荐使用的石油测井仪器可靠性指标。 相似文献