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101.
102.
G Frank J Qiu M Somsouk Y Weng L Somsouk JP Nolan B Shen 《Canadian Metallurgical Quarterly》1998,273(49):33064-33072
To assess the roles of the active site residues Glu160 and Asp181 of human FEN-1 nuclease in binding and catalysis of the flap DNA substrate and in vivo biological processes of DNA damage and repair, five different amino acids were replaced at each site through site-directed mutagenesis of the FEN-1 gene. The mutants were then expressed in Escherichia coli and purified using a His-tag. Even though the mutants bind to the flap DNA to different degrees, most of the mutants lost flap nuclease activity with the exception of an E160D mutant. This mutant retained wild type-like binding ability, specificity, and partial catalytic activity. Detailed steady state and pre-steady state kinetic analysis revealed that the functional deficiency of this mutant was due to retardation of the endonucleolytic cleavage. When the mutant enzyme E160D was expressed in yeast, it partially complements the biological functions of the homologous yeast gene, RAD27, and reverses the hyper-temperature lethality and hypersensitivity to methyl methanesulfonate, in a manner corresponding to the in vitro activity. 相似文献
103.
该文根据开槽管状药的装药结构特点,建立两相流内弹道理论模型.在定义了开槽管状药的肉厚与槽宽的基础上,推导出形状函数,采用差分方法求解.计算结果表明,开槽管状药透气性好,点传火容易,压力波振幅小,计算结果符合膛内射击过程的变化规律. 相似文献
104.
形成高压纳秒脉冲仿真线的设计 总被引:1,自引:0,他引:1
本文叙述了高低阻抗线和螺旋带传输线的设计原则,并利用这二种仿真线在同轴50Ω负载上获得了快前沿的高压纳秒脉冲。实测结果表明,脉冲的上升时间小于0.4ns,宽度从1.65~10.6ns可变,幅值大于2000V。 相似文献
105.
Jui‐Ming Yeh Chang‐Jian Weng Kuan‐Yeh Huang Hsi‐Ya Huang Yuan‐Hsiang Yu Chung‐Hung Yin 《应用聚合物科学杂志》2004,94(1):400-405
A series of sol‐gel derived organic–inorganic hybrid materials consisting of organic poly(methyl methacrylate) (PMMA) and inorganic titania (TiO2) were successfully synthesized by using 2‐hydroxyethyl methacrylate (HEMA) as coupling agent. In this work, HEMA is first copolymerized with methyl methacrylate monomer at specific feeding ratios by using benzoyl peroxide (BPO) as initiator. Subsequently, the as‐prepared copolymer (i.e., sol‐gel precursor) is then cohydrolyzed with various contents of titanium butoxide to afford chemical bondings to the forming titania networks to give a series of hybrid materials. Transparent organic–inorganic hybrid materials with different contents of titania are always achieved. Effects of the material composition on the thermal stability, optical properties, and morphology of neat copolymer and a series of hybrid materials, in the form of both coating and free‐standing film, are also studied by differential scanning calorimetry, thermogravimetric analysis, UV–Vis transmission spectra, refractometer, and atomic force microscopy, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 400–405, 2004 相似文献
106.
以四甲基氢氧化铵为催化剂,八甲基环四硅氧烷为单体,水为封端剂,一步合成羟基聚硅氧烷。采用凝胶渗透色谱(GPC)测定上述一步合成法的转化率,并建立转化率一时间关系曲线的模型函数(Bolzman函数),获得聚合过程中的重要特征参数:最大转化速率rm,极限转化率x(∞)等。研究表明.温度升高,rm加快,x(∞)降低;催化剂浓度增加,rm加快,x(∞)也增加,而转化速率与催化剂浓度在一定的范围内呈l级动力学关系;水浓度增加,rm降低,同时x(∞)也降低。 相似文献
107.
Mixed ionic/electronic conductor (MIEC) cathodes with graded composition and microstructures have been fabricated using improved spin-coating technique. Two components, Sm0.2Ce0.8O1.9 (SDC) and Sm0.5Sr0.5CoO3 (SSC), were utilized to prepare the graded MIEC cathode. Graded microstructures, i.e., a SSC-rich outer layer with large interconnected pores and a SDC-rich inner layer with small interconnected pores, were observed. The corresponding single cell had an increase of 13.3% in maximum power density at operating temperature of 600 °C. The present work suggests that the graded MIEC cathode has great potential in improving performance of solid oxide fuel cells operated at lower temperature. 相似文献
108.
以四乙基溴化胺为催化剂,1,4-丁二醇为起始剂,邻苯二甲酸酐和环氧氯丙烷为原料合成聚酯树脂,采用傅立叶红外光谱(FT-IR)和核磁共振(1H-NMR)对产物的结构进行表征,并考察了催化剂用量和反应温度对合成聚酯树脂的影响.结果表明,合成聚酯树脂的端基为羟基,且随着温度升高和催化剂用量增加,反应速率增加,合适的反应条件为... 相似文献
109.
Youqun Lai Yanyan Ma Liping Sun Jing Jia Jian Weng Nan Hu Wei Yang Qiqing Zhang 《Electrochimica acta》2011,(9):3153
A highly selective electrochemical biosensor for the detection of Hg2+ in aqueous solution has been developed. This sensor is based on the strong and specific binding of Hg2+ by two DNA thymine bases (T–Hg2+–T). The hemin worked as a redox indicator to generate a readable electrochemical signal. Short oligonucleotide strands containing 5 thymine (T5) were used as probe. Thiolated T5 strands were self-assembled through Au–S bonding on gold electrode. In the presence of Hg2+, the specific coordination between Hg2+ and thymine bases resulted in more stable and porous arrangement of oligonucleotide strands, so hemin could be adsorbed on the surface of gold electrode and produced an electrochemical signal, which was monitored by differential pulse voltammetry (DPV). The DPV showed a linear correlation between the signal and the concentration of Hg2+ over the range 0–2 μM (R2 = 0.9983) with a detection limit of 50 nM. The length of probe DNA had no significant impact on the sensor performance. This electrochemical biosensor could be widely used for selective detection of Hg2+. 相似文献
110.
In this work, the mechanism analysis of Poly(DL ‐lactic acid) (PLA) particles formation is investigated by dissipative particle dynamics (DPD) simulations. The polymer PLA is usually as a carrier at the drug deliver system (DDS), first, the mechanism analysis of PLA particles formation was preceded on the basis of the blank PLA particles. At the same time, the formation of PLA particles for drug delivery systems has been investigated. The results of DPD simulations indicate that the formation of PLA particles with drug or not, consists of three steps: (1) aggregation‐individual PLA chains got aggregated with each other in solution; (2) formation and disruption of PLA particles; (3) solidification of PLA particles. At the same time, the effects of PLA, drug content on the aggregation morphology are investigated, which indicates the PLA particles with drug or not aggregated and formed is spherical particles, drug molecules are amorphously and homogeneously distributed inside the PLA matrix, the size of PLA particles increases with increasing the initial PLA content and drug content in the solution. The content of DMF is gotten when PLA chains and drug molecules begin to aggregate and form the particles. These could be used to guide the experimental preparation of PLA blank particles and DDS with desired properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献