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排序方式: 共有380条查询结果,搜索用时 46 毫秒
371.
Feng L Wakahara T Nakahodo T Tsuchiya T Piao Q Maeda Y Lian Y Akasaka T Horn E Yoza K Kato T Mizorogi N Nagase S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(21):5578-5586
The reaction of La@C82 with diethyl bromomalonate in the presence of base (the Bingel reaction) generated five monoadducts which have been fully characterized. It was found that four of them (mono-A, -B, -C, and -D) are ESR-inactive, suggesting singly bonded regioisomers. In contrast, the fifth product (mono-E) is ESR-active, indicating that it possesses a cyclic moiety between the appended malonate group and the fullerene cage, analogous to conventional Bingel adducts. The differences in the molecular structures of mono-A, -B, -C, and -E result in varying thermal stabilities and electrochemical behavior. In particular, the singly bonded monoadducts undergo the retro-Bingel reaction either under thermal treatment or during electron transfer on the cyclic voltammetric timescale. However, mono-E shows remarkable thermal stability and perfect reversibility under the same experimental conditions. 相似文献
372.
HanQing Ge Yan Leng FuMin Zhang JiaRui Piao ChangJiang Zhou Jun Wang 《中国科学B辑(英文版)》2009,52(8):1264-1269
Pyridine(Py)-modified Keggin-type vanadium-substituted heteropoly acids (Py
n
PMo10V2O40, n=1 to 5) were prepared by a precipitation method as organic/inorganic hybrid catalysts for direct hydroxylation of benzene
to phenol in a pressured batch reactor and their structures were detected by FT-IR. Among various catalysts, Py3PMo10V2O40 exhibits the highest catalytic activity (yield of phenol, 11.5%), without observing the formation of catechol, hydroquinone
and benzoquinone in the reaction with 80 vol% aqueous acetic acid, molecular oxygen and ascorbic acid used as the solvent,
oxidant and reducing reagent, respectively. Influences of reaction temperature, reaction time, oxygen pressure, amount of
ascorbic acid and catalyst on yield of phenol were investigated to obtain the optimal reaction conditions for phenol formation.
Pyridine can greatly promote the catalytic activity of the Py-free catalyst (H5PMo10V2O40), mostly because the organic π electrons in the hybrid catalyst may extend their conjugation to the inorganic framework of
heteropoly acid and dramatically modify the redox properties, at the same time, pyridine adsorbed on heteropoly acids can
promote the effect of “pseudo-liquid phase”, thus accounting for the enhancement of phenol yield.
Supported by the National Natural Science Foundation of China (Grant Nos. 20476046 and 20776069) and the “Qinglan” Project
of Jiangsu Province for Young Researchers 相似文献
373.
Enhanced recognition of non-complementary hybridization by single-LNA-modified oligonucleotide probes 总被引:1,自引:0,他引:1
XianYu Piao Ying Yan Jing Yan YiFu Guan 《Analytical and bioanalytical chemistry》2009,394(6):1637-1643
Locked nucleic acid (LNA) is a deoxyribonucleotide analogue with an unusual ‘locked’ furanose conformation. LNA-modified oligonucleotide
probes have demonstrated an enhanced binding affinity towards their complementary strands; however, their potential to discriminate
non-complementary hybridization of mismatches has not been explored. In this study, we investigated the effect of the chemical
nature of LNA nucleobases on the hybridization stability and the capability of LNA-modified oligonucleotides to discriminate
the LNA:DNA mismatched base pairs. It was observed that LNA modification indeed improves the discrimination capability of
oligonucleotides by increasing the melting temperature differences between the complementary duplexes and hybrids containing
mismatches. Particularly, LNA purines offer a greater potential to recognize the mismatches than LNA pyrimidines and DNA purines.
Real-time PCR experiments further confirmed that LNA modifications at the 3′-end are more effective. The results and conclusions
in this study provide useful information for hybridization-based nucleic acid analysis where designing sound oligonucleotide
probes is crucial to the success of the analyses.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
374.
复杂网络控制反映了人类对复杂系统的认识深度和改造能力. 最新研究成果基于线性系统控制理论建立了复杂网络可控性的理论架构, 能够发现任意拓扑结构的线性时不变复杂网络中控制全部节点状态的最小驱动节点集, 但是该模型未考虑免疫节点或失效节点对控制信号传播的阻断.在继承该模型优点的前提下, 重新构建了基于传播免疫的复杂网络控制模型.在采用分属于随机免疫和目标免疫两种策略的 4个方法确定免疫节点的情况下,分析14个真实网络的可控性.结果表明:如果将网络中度数、 介数和紧密度指标较高的节点作为免疫节点,将极大地提高控制复杂网络的难度. 从而在一定程度上丰富了以往模型的结论. 相似文献
375.
Zhi-Guo LiChang-Ge Piao Xing PanYong-Kai Wei Yan Cheng Guang-Fu Ji 《Physica B: Condensed Matter》2012,407(3):361-367
The elastic, phonon and thermodynamic properties of the divalent alkaline-earth hexaboride SrB6 are investigated by using plane-wave pseudopotential density functional theory method. The calculated structure parameters and bulk modulus are well consistent with the available experiment and theoretical data. The pressure dependences of elastic constants Cij, bulk modulus B0, shear modulus G, Young's modulus E and Poisson's ratio σ are also presented. With these elastic parameters, we investigate the mechanical stability and compressibility of SrB6. For the thermodynamic properties, both phonon and quasi-harmonic Debye model methods are adopted. Through the comparison with experimental and other theoretical results, we found the method of quasi-harmonic Debye model is a little better. Moreover, the phonon dispersion relations are also obtained. It is found that there are two LO/TO splitting around 5 THz and 26 THz, respectively. 相似文献
376.
通过对标准样品和仪器条件的选择,元素条件及组条件的编辑、回归分析、工作曲线的制作、准确度和精密度的试验,建立了X射线荧光光谱法测定中低合金钢中Si、Mn、Cr、Ni、Mo、V、W、Ti、Cu和P元素质量分数的分析方法。方法的精密度和准确度满足国家标准要求。 相似文献
377.
Herath Mudiyanselage Udari Lakmini Herath Mei Jing Piao Kyoung Ah Kang Ao Xuan Zhen Pincha Devage Sameera Madushan Fernando Hee Kyoung Kang Joo Mi Yi Jin Won Hyun 《Molecules (Basel, Switzerland)》2022,27(15)
Particulate matter 2.5 (PM2.5) exposure can trigger adverse health outcomes in the human skin, such as skin aging, wrinkles, pigment spots, and atopic dermatitis. PM2.5 is associated with mitochondrial damage and the generation of reactive oxygen species (ROS). Hesperidin is a bioflavonoid that exhibits antioxidant and anti-inflammatory properties. This study aimed to determine the mechanism underlying the protective effect of hesperidin on human HaCaT keratinocytes against PM2.5-induced mitochondrial damage, cell cycle arrest, and cellular senescence. Human HaCaT keratinocytes were pre-treated with hesperidin and then treated with PM2.5. Hesperidin attenuated PM2.5-induced mitochondrial and DNA damage, G0/G1 cell cycle arrest, and SA-βGal activity, the protein levels of cell cycle regulators, and matrix metalloproteinases (MMPs). Moreover, treatment with a specific c-Jun N-terminal kinase (JNK) inhibitor, SP600125, along with hesperidin markedly restored PM2.5-induced cell cycle arrest and cellular senescence. In addition, hesperidin significantly reduced the activation of MMPs, including MMP-1, MMP-2, and MMP-9, by inhibiting the activation of activator protein 1. In conclusion, hesperidin ameliorates PM2.5-induced mitochondrial damage, cell cycle arrest, and cellular senescence in human HaCaT keratinocytes via the ROS/JNK pathway. 相似文献
378.
379.
Rui Sun Yifan Zhang Xiaowei Lin Ying Piao Tao Xie Yi He Jiajia Xiang Shiqun Shao Quan Zhou Zhuxian Zhou Jianbin Tang Youqing Shen 《Angewandte Chemie (International ed. in English)》2023,62(9):e202217408
Tumor enzyme-responsive charge-reversal carriers can induce efficient transcytosis and lead to efficient tumor infiltration and potent anticancer efficacy. However, the correlations of molecular structure with charge-reversal property, tumor penetration, and drug delivery efficiency are unknown. Herein, aminopeptidase N (APN)-responsive conjugates were synthesized to investigate these correlations. We found that the monomeric unit structure and the polymer chain structure determined the enzymatic hydrolysis and charge-reversal rates, and accordingly, the transcytosis and tumor accumulation and penetration of the APN-responsive conjugates. The conjugate with moderate APN responsiveness balanced the in vitro transcytosis and in vivo overall drug delivery process and achieved the best tumor delivery efficiency, giving potent antitumor efficacy. This work provides new insight into the design of tumor enzyme-responsive charge-reversal nanomedicines for efficient cancer drug delivery. 相似文献
380.