全文获取类型
收费全文 | 757篇 |
免费 | 41篇 |
国内免费 | 28篇 |
专业分类
化学 | 274篇 |
晶体学 | 4篇 |
力学 | 13篇 |
综合类 | 8篇 |
数学 | 59篇 |
物理学 | 135篇 |
综合类 | 333篇 |
出版年
2023年 | 4篇 |
2021年 | 6篇 |
2020年 | 11篇 |
2019年 | 7篇 |
2018年 | 4篇 |
2016年 | 10篇 |
2015年 | 17篇 |
2014年 | 15篇 |
2013年 | 26篇 |
2012年 | 29篇 |
2011年 | 28篇 |
2010年 | 18篇 |
2009年 | 17篇 |
2008年 | 32篇 |
2007年 | 21篇 |
2006年 | 26篇 |
2005年 | 11篇 |
2004年 | 17篇 |
2003年 | 65篇 |
2002年 | 121篇 |
2001年 | 86篇 |
2000年 | 50篇 |
1999年 | 44篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1992年 | 8篇 |
1990年 | 7篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 6篇 |
1973年 | 5篇 |
1971年 | 4篇 |
1970年 | 6篇 |
1941年 | 3篇 |
1933年 | 3篇 |
1928年 | 3篇 |
1914年 | 2篇 |
1912年 | 2篇 |
1904年 | 2篇 |
排序方式: 共有826条查询结果,搜索用时 859 毫秒
71.
Farbwerke vormals Meister Lucius und Brüning 《Fresenius' Journal of Analytical Chemistry》1914,53(6):382-383
Ohne Zusammenfassung 相似文献
72.
73.
74.
为有效辅助工程师将顾客需求转化为产品服务系统方案,针对其技术特征,提出一种离散粒子群优化算法(DPSO)与帕累托(Pareto)结合的配置规则提取方法.该方法包括建立产品服务系统配置规则模型及构造Pareto-DPSO算法模型.Pareto-DPSO算法基于Sobol序列的频率初始化方法及离散化粒子更新方式,将连续粒子映射到十进制离散空间;并利用Pareto进行多目标下粒子优劣性评价,以获取非支配的最优规则集.以汽车产品服务系统方案配置设计为例,经与常规多目标粒子群算法及DPSO算法对比,验证了该方法对于解决多维空间内产品服务配置规则挖掘的可行性及有效性. 相似文献
75.
Désirée L. Röhlen Johanna Pilas Michael J. Schöning Thorsten Selmer 《Applied biochemistry and biotechnology》2017,183(2):566-581
Three amperometric biosensors have been developed for the detection of l-malic acid, fumaric acid, and l -aspartic acid, all based on the combination of a malate-specific dehydrogenase (MDH, EC 1.1.1.37) and diaphorase (DIA, EC 1.8.1.4). The stepwise expansion of the malate platform with the enzymes fumarate hydratase (FH, EC 4.2.1.2) and aspartate ammonia-lyase (ASPA, EC 4.3.1.1) resulted in multi-enzyme reaction cascades and, thus, augmentation of the substrate spectrum of the sensors. Electrochemical measurements were carried out in presence of the cofactor β-nicotinamide adenine dinucleotide (NAD+) and the redox mediator hexacyanoferrate (III) (HCFIII). The amperometric detection is mediated by oxidation of hexacyanoferrate (II) (HCFII) at an applied potential of + 0.3 V vs. Ag/AgCl. For each biosensor, optimum working conditions were defined by adjustment of cofactor concentrations, buffer pH, and immobilization procedure. Under these improved conditions, amperometric responses were linear up to 3.0 mM for l-malate and fumarate, respectively, with a corresponding sensitivity of 0.7 μA mM?1 (l-malate biosensor) and 0.4 μA mM?1 (fumarate biosensor). The l-aspartate detection system displayed a linear range of 1.0–10.0 mM with a sensitivity of 0.09 μA mM?1. The sensor characteristics suggest that the developed platform provides a promising method for the detection and differentiation of the three substrates. 相似文献
76.
J. Brüning S. Yu. Dobrokhotov S. Ya. Sekerzh-Zen’kovich T. Ya. Tudorovskiy 《Russian Journal of Mathematical Physics》2011,18(1):33-53
In the paper, which is the second part of the paper by J. Brüning, S. Dobrokhotov, S. Sekerzh-Zenkovich, T. Tudorovskiy, “Spectral series of the Schrödinger operator in thin waveguides with a periodic structure. 1,” Russ. J. Math. Phys. 13 (4), 401–420 (2006), using the adiabatic approximation, diverse quantum states of the stationary Schrödinger equation for a particle in a thin waveguide in a magnetic field are constructed. The problems of “destruction” of the adiabatic approximation as the value of energy increases and of replacing this approximation by the approximation of V. P. Maslov’s theory of complex germ (the complex WKB method) are studied. 相似文献
77.
针对12支路并联的快前沿直线脉冲变压器单级模块,给出了模块的电路结构和关键器件参数,实验获得了12只多间隙气体开关的自击穿特性和触发特性。同时,还给出了快前沿直线脉冲变压器模块输出电流的初步实验结果,工作电压150 kV时,次级短路放电电流幅值为235 kA,电流前沿88.2 ns(10%~90%)。次级带0.58 负载情况下,输出电流幅值114.5 kA,电流前沿88.9 ns(10%~90%)。利用微分环测量了12只开关的触发时延分散性,结果表明100次实验开关触发时延分散性近似符合正态分布,开关触发时延分散性对输出电流的影响不大,电流幅值和前沿的标准偏差分别小于2.0%,4.0%,电流波形的畸变主要以平顶为主。 相似文献
78.
79.
矿区煤炭开发的灰色规划探讨 总被引:2,自引:0,他引:2
根据福建省矿区煤炭开发的现状和基本条件,应用灰色系统理论和运筹学,建立煤炭开发的灰色预测线性规划数学模型,探讨矿区煤炭开发未来系统的动态规划和优化控制问题。并用VB6.0语言编制了相应的软件。 相似文献
80.
Haiping Qi Manfred Gröning Tyler B. Coplen Bryan Buck Stanley J. Mroczkowski Willi A. Brand Heike Geilmann Matthias Gehre 《Rapid communications in mass spectrometry : RCM》2010,24(13):1821-1827
A new method to seal water in silver tubes for use in a TC/EA (thermal conversion/elemental analyzer) reduction unit using a semi‐automated sealing apparatus can yield reproducibilities (1 standard deviation) of δ2H and δ18O measurements of 1.0‰ and 0.06‰, respectively. These silver tubes containing reference waters may be preferred for the calibration of H‐ and O‐bearing materials analyzed with a TC/EA reduction unit. The new sealing apparatus employs a computer‐controlled stepping motor to produce silver tubes identical in length. The reproducibility of the mass of water sealed in tubes (in a range of 200–400 µg) can be as good as 1%. Approximately 99% of the sealed silver tubes are satisfactory (leak free). Although silver tubes sealed with reference waters are robust and can be shaken or heated to 110°C with no loss of integrity, they should not be frozen because the expansion during the phase transition of water to ice will break the cold seals and all the water will be lost. The tubes should be shipped in insulated containers. This new method eliminates air inclusions and isotopic fractionation of water associated with the loading of water into capsules using a syringe. The method is also more than an order of magnitude faster than preparing water samples in ordinary Ag capsules. Nevertheless, some laboratories may prefer loading water into silver capsules because expensive equipment is not needed, but users of this method are cautioned to apply the necessary corrections for evaporation, back exchange with laboratory atmospheric moisture, and blanks. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献