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1.
2.
用2D NMR技术研究了从朝鲜淫羊藿中分离的一个黄酮醇-3-O-D-木糖-鼠李糖甙的结构,确定其双糖为1→2连接,并明确了判断同类黄酮醇-3-O-木糖基(1→2)-鼠李糖甙的简易标准. 相似文献
3.
Bulk amorphous Pd41Ni10Cu28P21 alloy has been prepared by water quenching method. The system shows excellent glass forming ability (GFA) with a high value of reduced glass transition temperature Trg, 0.714. Structural analyses indicate that the Pd41Ni10Cu28P21 alloy has a dense packing structure closer to "frozen liquid" than that of amorphous Pd40Ni40P20 alloy. Experiments on crystallization reveal that several crystalline phases simultaneously precipitate in the early part of crystallization. Below 710 K, a metastable phase forms, and subsequently disappears at elevated temperatures. In addition, the influence of partial substitute of Cu for Ni on GFA has been discussed with regard to thermodynamics and kinetics. 相似文献
4.
Oxime-based salen-type tetradentate ligands with high stability against imine metathesis reaction 总被引:2,自引:0,他引:2
Akine S Taniguchi T Dong W Masubuchi S Nabeshima T 《The Journal of organic chemistry》2005,70(5):1704-1711
Although salen and its analogues are versatile chelate ligands in inorganic and organometallic chemistry, synthesis of unsymmetrical salen derivatives consisting of two different salicylideneimine moieties is difficult because of the C=N bond recombination. To develop stable analogues of salen-type ligands, we synthesized a series of new ligands salamo (=1,2-bis(salicylideneaminooxy)ethane) on the basis of O-alkyl oxime instead of the imine moiety. Eight salamo ligands 1a-h were prepared in 64-88% yields as colorless crystals from the corresponding salicylaldehydes 2a-h. The crystal structure of 1a-c suggests that the oxime-OH form is more predominant than the keto-NH form. The reaction of 2a-e with excess 1,2-bis(aminooxy)ethane gave monooximes 3a-e in 59-86%, which further reacted with a different salicylaldehyde to afford unsymmetrical salamo ligands 4-8 as stable crystals in 51-70%. No reaction took place when a mixture of salamo derivatives 1a and 1b was treated at 40 degrees C in H2O/MeCN (5:95). However, the metathesis reaction of salen derivatives 9a and 9b completed in 2 h to give a statistical mixture. Monooxime 3b was much more stable than monoimine 11 which is difficult to be isolated. These results indicate the extremely high stability of the salamo derivatives 1 and precursors 3. 相似文献
5.
Xiaoyu Li Cuiqing Zhang Changyuan Hu Linchong Xu Quanhong Hu Shuwang Duo Wenkui Li Yongfang Kang 《Journal of Cluster Science》2017,28(5):2409-2418
A novel Bi2O4@TiO2 heterojunction was constructed by a simple two-step method. The charges migration between Bi2O4 and TiO2 via the heterojunction improves the electron/hole separation efficiency. Furthermore, Bi2O4@TiO2 heterostructures exhibit better adsorption capability for methyl orange molecular due to their higher specific surface area than pure Bi2O4. As a result, Bi2O4@TiO2 hybrids show an improved visible light photocatalytic activity and photostability for the degradation of methyl orange. 相似文献
6.
利用在HI-13串列加速器的在束γ终端上建立的多普勒线移衰减法、反冲距离多普勒线移法和快时间延迟符合法等3种寿命测量方法,开展了原子核手征对称性、磁转动等核结构热点课题的研究工作。实验结果表明,130Cs的伙伴带具有很好的手征特性,而106Ag的候选带并非手征双带。根据测量的能级寿命提取的B(M1)值表明,106Ag的正宇称晕带和107Ag的正、负宇称晕带都具有典型的磁转动特性。此外,寿命测量数据还为解释和理解不同的同位素链中展现出的形状演化、形状共存、形状相变及临界点对称性等物理现象提供了有价值的实验证据。 The significance and principle of lifetime measurements of excited states in nuclei are briefly described. By using the recoil-distance Doppler-shift method, the Doppler-shift attenuation method, and the fast-timing technique established at the in-beam γ terminal of HI-13 tandem accelerator, nuclear structure studies on topical subjects including chiral symmetries and magnetic rotation have been performed. Our experimental results indicate that 130Cs shows better chiral characteristics, however, the two candidate bands of 106Ag could not be a pair of chiral doublet bands. For magnetic rotation, the deduced B(M1) values deduced from the measured level lifetimes clearly demonstrate that the yrast positive-parity band in 106Ag and both the yrast positiveand negative-parity bands in 107Ag are magnetic rotation bands. In addition, our lifetime measurement data also provide valuable experimental evidences for the interpretation and understanding of the shape evolution, the shape coexistence, and the critical-point symmetries of shape phase transition in the different isotope chains. 相似文献
7.
Xiaoyu Li Fei Chen Chengjiang Lian Shizheng Zheng Quanhong Hu Shuwang Duo Wenkui Li Changyuan Hu 《Journal of Cluster Science》2016,27(6):1877-1892
Au/TiO2/graphene composite was synthesized by the combination of electrostatic attraction and photo-reduction method. In the composite, graphene sheets act as an adsorption site for dye molecules to provide a high concentration of dye near to the TiO2 and Au nanoparticles (NPs), and work as an excellent electron transporter to separate photoinduced e ?/h + pairs. Under UV irradiation, photogenerated electrons of TiO2 are transferred effectively to Au NPs and graphene sheets, respectively, retarding the recombination of electron–hole pairs. Under visible light irradiation, the Au NPs are photo-excited due to the surface plasmon resonance effect, and charge separation is accomplished by the interfacial electron injection from the Au NPs to the conduction band of TiO2 and then transfer further to graphene sheets. As a result, compared with pure TiO2, Au/TiO2/graphene composite exhibited much higher photocatalytic activity for degradation of methylene blue under both UV and visible light irradiation, based on the synergistic effect of Au, graphene in contact with TiO2, allowing response to the visible light, effective separation of photoinduced charges, and better adsorption of the dye molecules. 相似文献
8.
9.
钾(Ⅰ)(苯并-15-冠-5)新型配合物的合成及性质 总被引:1,自引:0,他引:1
在非水溶剂中合成并-15-冠-5与碘化钾,硫氰化钾及苦味酸钾形成的三种新型固体配合物,并进行了有关物理,化学性质表征,结果表明,钾(Ⅰ)离子不仅易苯并-15-冠-5天成常见的1:2夹心式配合物,而且还能生成稳定的1:1型固体配合物。 相似文献
10.
Shenghan Zhou Houxiang Liu Bang Chen Wenkui Hou Xinpeng Ji Yue Zhang Wenbing Chang Yiyong Xiao 《Entropy (Basel, Switzerland)》2021,23(6)
The traditional sequential pattern mining method is carried out considering the whole time period and often ignores the sequential patterns that only occur in local time windows, as well as possible periodicity. Therefore, in order to overcome the limitations of traditional methods, this paper proposes status set sequential pattern mining with time windows (SSPMTW). In contrast to traditional methods, the item status is considered, and time windows, minimum confidence, minimum coverage, minimum factor set ratios and other constraints are added to mine more valuable rules in local time windows. The periodicity of these rules is also analyzed. According to the proposed method, this paper improves the Apriori algorithm, proposes the TW-Apriori algorithm, and explains the basic idea of the algorithm. Then, the feasibility, validity and efficiency of the proposed method and algorithm are verified by small-scale and large-scale examples. In a large-scale numerical example solution, the influence of various constraints on the mining results is analyzed. Finally, the solution results of SSPM and SSPMTW are compared and analyzed, and it is suggested that SSPMTW can excavate the laws existing in local time windows and analyze the periodicity of the laws, which solves the problem of SSPM ignoring the laws existing in local time windows and overcomes the limitations of traditional sequential pattern mining algorithms. In addition, the rules mined by SSPMTW reduce the entropy of the system. 相似文献