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排序方式: 共有331条查询结果,搜索用时 156 毫秒
111.
Sengul Uysal Aleksandra Cvetanović Zoran Zeković Mohamad Fawzi Mahomoodally Oskar Bera 《Analytical letters》2019,52(13):2150-2163
The main goals of this research were the chemical and biological characterization of the bitter melon (Momordica charantia) isolate obtained by traditional (maceration) extraction, as well as optimization of this process using response surface methodology (RSM) and artificial neural networks (ANNs). Experiments were performed using Box–Behnken experimental design on three levels and three variables: extraction temperature (20?°C, 40?°C, and 60?°C), solvent concentration (30%, 50%, and 70%) and extraction time (30, 60, and 90?min). The measurements consisted of 15 randomized runs with 3 replicates in a central point. The antioxidant activity of obtained extracts was determined by the 1,1-diphenyl-2-picrylhydrazyl (DPPH), cupric ion reducing antioxidant capacity (CUPRAC) and ferric reducing antioxidant power (FRAP) assays while chemical characterization was done in terms of the total phenolic content (TPC). The methodology shows positive influence of solvent concentration on all four observed outputs, while temperature showed a negative impact. RSM showed that the optimal extraction conditions were 20?°C, 70% methanol, and an extraction time of 52.2?min. Under these conditions, the TPCs were 20.66 milligrams of gallic acid equivalents (mg GAE/g extract), DPPH 30.22 milligrams of trolox equivalents (mg TE/g extract), CUPRAC 67.78 milligrams of trolox equivalents (mg TE/g extract), and FRAP 45.48 milligrams of trolox equivalents (mg TE/g extract). The neural network coupled with genetic algorithms (ANN-GA) was also used to optimize the conditions for each of the outputs separately. It is anticipated that results reported herein will establish baseline data and also demonstrate that that the present model can be applied in the food and pharmaceutical industries. 相似文献
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Sanjeev Singh 《Fiber and Integrated Optics》2019,38(1):43-75
In this article, a comparative performance analysis of three (03) different algorithms operating in the control plane of the three (03) varied architectures such as Physically Distributed, Logically Distributed, and Physically Centralized Architecture has been done. The paper also elucidates the working and implementation of the three proposed architectures with suitable block diagram of system model. Besides, in these architecture models OpenFlow (OF) governed various MATLAB components have been designed such as Application Controller, Optical Transport Network Controller, SDOWN Controller, Ethernet switch-1 and 2, ROADM and Wi-Fi access point with suitable interfaces. Pseudo codes of the algorithms operating in above said MATLAB components are duly explained with flowcharts. Mathematical analysis of three different architecture in respect of latency is carried out, and results and discussions with suitable figures have also been represented. The results obtained show that out of three (03) aforesaid architectures the Physical Centralized Architecture has better performance upto 45 Km in terms of Q-factor, SNR, BER, Jitter and Latency. 相似文献
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采用Schulte-Reisch方法,在氯化亚铜催化下,由1,4-二苯基丁二炔与苯胺反应成功制备了1,2,5-三苯基吡咯(TPP)。通过将溶液反应改进为本体反应,不仅提高了收率,而且降低了反应温度,缩短了反应时间。当水的含量在THF-水混合溶剂中低于60%时,因TPP没有产生聚集,其荧光强度基本没有发生变化;但水含量增加到70%时,因聚集紧密程度较低,π—π堆积作用诱发非辐射能量转移,使荧光强度被猝灭;而当水的含量超过80%以上时,TPP呈现高紧密聚集,使分子内旋转受到限制,降低了非辐射能量转移,使发光得到增强。由于乙腈与TPP之间所形成的较强电荷转移相互作用影响了聚集紧密程度,没有呈现高聚集诱导发光增强性质。 相似文献
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The electronic band structures of periodic models for Si-H compounds are investigated by the density functional theory.Our results show that the Si-H compound changes from indirect-gap semiconductor to direct-gap semiconductor with the increase of H content.The density of states,the partial density of states and the atomic charge population are examined in detail to explore the origin of this phenomenon.It is found that the Si-Si bonds are affected by H atoms,which results in the electronic band transformation from indirect gap to direct gap.This is confirmed by the nearest neighbour semi-empirical tight-binding (TB) theory. 相似文献
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ClMe2SiSiMe2Cl顺序与茚基锂和环戊二烯基锂作用,生成(1-C9H7)Me2SiSiMe2C5H5.后者进一步与五羰基铁反应,得到硅硅桥联茚基环戊二烯基化合物[η5,η5-(1-C9H6)Me2SiSiMe2C5H4]Fe2(CO)4 (2).化合物2在加热条件下发生重排反应,给出硅硅键和铁铁键复分解产物([-)Me2Si(η5-1-C9H6)Fe(CO)2SiMe2(η5-C5H4)Fe(CO)2(]-) (3).利用X射线衍射法,测定了2和3的分子结构. 相似文献
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利用密度泛函理论研究B6和LimB6 (m= 1–2)团簇的结构及其储氢性能. 结果表明, 氢分子在B6团簇的三种可能结构中均发生解离吸附, Li原子在B6团簇表面不发生团聚,每一个Li原子均吸附几个氢分子. 其中以两个Li原子修饰笼形B6团簇吸附完整氢分子数最多,储氢质量分数为20.38%, 氢分子的平均吸附能为1.683 kcal/mol,表明了它在常温常压条件下作为储氢材料的可行性.
关键词:
mB6 (m=1-2)团簇')" href="#">LimB6 (m=1-2)团簇
密度泛函理论(DFT)
吸附能
储氢性能 相似文献
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