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排序方式: 共有323条查询结果,搜索用时 31 毫秒
91.
Eric Sidler Dr. Patrick Zwick Charlotte Kress Ksenia Reznikova Dr. Olaf Fuhr Prof. Dr. Dieter Fenske Prof. Dr. Marcel Mayor 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(53):e202201764
The synthetic access to macrocyclic molecular topologies with interesting photophysical properties has greatly improved thanks to the successful implementation of organic and inorganic corner units. Based on recent reports, we realized that pseudo-meta [2.2]paracyclophanes (PCPs) might serve as optimal corner units for constructing 3D functional materials, owing to their efficient electronic communication, angled substituents and planar chirality. Herein, we report the synthesis, characterization and optical properties of four novel all-carbon enantiopure macrocycles bearing three to six pseudo-meta PCPs linked by 1,3-butadiyne units. The macrocycles were obtained by a single step from enantiopure, literature-known dialkyne pseudo-meta PCP and were unambiguously identified and characterized by state of the art spectroscopic methods and in part even by x-ray crystallography. By comparing the optical properties to relevant reference compounds, it is shown that the pseudo-meta PCP subunit effectively elongates the conjugated system throughout the macrocyclic backbone, such that already the smallest macrocycle consisting of only three subunits reaches a polymer-like conjugation length. Additionally, it is shown that the chiral pseudo-meta PCPs induce a remarkable chiroptical response in the respective macrocycles, reaching unprecedented high molar circular dichroism values for all-carbon macrocycles of up to 1307 L mol−1 cm−1. 相似文献
92.
以8,1 1,14-三氮杂-5,6:16,17-二苯并-1,4-二氧杂环十七烷为原料,合成了含萘磺酰基的N_3O_2大环化合物,其结构经~1H NMR,MS,元素分析等表征.通过紫外光谱法和荧光光谱法研究了N_3O_2大环化合物与小牛胸腺DNA的作用机制.结果表明:N_3O_2大环化合物通过嵌插方式与DNA结合,结合常数为K_(298.2 K)~■=20706.9 dm~3·mol~(-1),K_(308.2 K)~■=12416.9 dm~3·mol~(-1),二者结合为焓驱动反应. 相似文献
93.
94.
Bo-Long Poh Chi-Ming Tan 《Journal of inclusion phenomena and macrocyclic chemistry》2000,38(1-4):69-74
The stability constants K of the 1 : 1host to guest complexes formed betweencyclotetrachromotropylene and the two nucleotides,uridine 2',3'-cyclicmonophosphate, sodium salt andadenosine 2',3'-cyclicmonophosphate, sodium salt, inwater were determined by proton NMR spectroscopy. Theyare 35 and 195 M-1, respectively, at 25 °C.The base component of each nucleotide is included inthe hydrophobic cavity of the host in the twocomplexes. 相似文献
95.
Masahiko Inouye 《Journal of inclusion phenomena and macrocyclic chemistry》1998,32(2-3):223-233
This account describes recent examples of multifunctional artificial receptors, which demonstrates our approach to purposive molecular design. The paper is divided into two parts. The first deals with novel crowned spirobenzopyrans as dual-mode signal transducers. The new crowned spirobenzopyrans complement previous crowned spirobenzopyrans from the viewpoint of molecular devices, and a detailed comparison between them is given. The second part is concerned with polypyridine-macrocyclic structures as ribofuranoside receptors. The design of the ribofuranoside receptors was based on the multipoint hydrogen bond complementarity between the receptors and methyl -(d)-ribofuranoside. The binding affinity of the receptors was very high, so that even native ribose was extracted by them into nonpolar solvents. 相似文献
96.
Hakan Alp Zekeriya Biyiklioğlu Gülsev Dilber ÜmmÜhan Ocak Aysel Marap Halit Kantekin 《Journal of inclusion phenomena and macrocyclic chemistry》2007,58(3-4):283-288
Synthetic procedures for new N2S4- and N2S5-donor macrocycles (2 and 4) were given. The ligands were prepared by the reaction of NaBH4 with the appropriate macrocyclic diamide in the presence of boron trifluoride ethyl etherate in dry tetrahydrofuran (THF).
Solvent extraction method was used to evaluate metal-ion binding properties of the new ligands. The solvent extraction experiments
suggested that the reduced macrocycles have Ag+ and Hg2+ selectivities compared to Pb2+, Co2+, Zn2+, Ni2+, Cu2+, Mn2+ and Cd2+ ions. The extraction constants (log K
ex) and complex compositions were determined for Ag+ and Hg2+ complex of compound (4). 相似文献
97.
Michael Sperling Xiu-ping Yan Bernhard Welz 《Spectrochimica Acta Part B: Atomic Spectroscopy》1996,51(14):1875-1889
A fully automated procedure for the determination of ng l−1 amounts of lead has been developed using flow injection (FI) online column preconcentration coupled with electrothermal atomic absorption spectrometry (ETAAS). The proposed FI manifold and its operation make possible the introduction of the total eluate volume into the graphite atomizer, avoiding the necessity for optimization of subsampling the eluate. The interference of other heavy metal ions due to competition for active sites of the sorbent is overcome using a highly selective macrocycle immobilized on silica gel (Pb-02). Lead is adsorbed on a microcolumn (50 μl) packed with Pb-02, and after washing the column with dilute nitric acid, air is introduced to remove all solution from the column and connecting tubing. The sorbed analyte is then eluted quantitatively into the graphite tube atomizer, preheated to 100°C, with 36 μl of ETDA solution (0.035 mol l−1, pH 10.5), propelled by air in order to minimize dispersion. The collection efficiency was 77% and with a sample loading flow rate of 3 ml min−1 and a 60 s preconcentration time, the enhancement factor was 77 and the throughput was 17 samples per hour. The relative standard deviation (n = 10) at the 300 ng l−1 level was 2.7%, and the detection limit (3σ) was 0.4 ng l−1. No interference from heavy metals was observed, but ions of Ba2+, Sr2+ and K+ were found to interfere when the concentration ratios of interferent to lead exceeded values of 2000, 20 000 and 200 000, respectively. Quantitative recovery of lead was achieved from sodium, magnesium, aluminum, lanthanum and heavy metal salt solutions. The high selectivity and sensitivity, combined with extremely low blank values, make the proposed technique particularly attractive for the analysis of high-purity reagents, semiconductors and other high-purity materials. Results are presented for the determination of lead in some high-purity reagents. 相似文献
98.
溶液中N-乙酸基取代氮氧杂大环及其配合物稳定性研究 总被引:1,自引:0,他引:1
用pH电位滴定法在25℃,0.5mol·L-1KNO3水溶液中测定了三种大环化合物:H2L1(1,12-二氮杂-3,4:9,10-二苯并-5,8-二氧杂环十五烷-N,N'-二乙酸);H3L2(1,12,15-三氮杂-3,4:9,10-二苯并-5,8-二氧杂环十七烷-N,N',N″-三乙酸)和H2L3(1,15-二氮杂-3,4:12,13-二苯并-5,8,11-三氧杂环十八烷-N,N′-二乙酸)的逐级质子化常数.又测定了它们与Cu2+、Ni2+、Pb2+配合物的稳定常数,以及H2L3与镧系金属La3+、Pr3+、Nd3+、Eu3+、Sm3+、Gd3+、Dy3+、Yb3+配合物的稳定常数.讨论了三种大环化合物质子化的一般顺序及其与各种离子配位时稳定性选择规律.说明了影响配位稳定性的有关因素. 相似文献
99.
The four-coordinate tin(II) complex [η4-Me8taa]Sn undergoes oxidative addition of I2 to give six-coordinate [η4-Me8taa]SnI2, in which the iodide ligands exhibit a trans arrangment. Abstraction of I− from [η4-Me8taa]SnI2 is facile, as indicated by the rapid formation of the triiodide derivative *[η4-Me8taa]SnI(THF)**I3* upon treatment with I2 in the presence of THF. The molecular structures of [η4-Me8taa]SnI2 and *[η4-Me8taa]SnI(THF)**I3* have been determined by X-ray diffraction. 相似文献
100.
The competition between intramolecular and bimolecular reactions of alkoxyl radicals formed from artemisinin was theoretically
analyzed. The enthalpies of these reactions were calculated. The activation energies and rate constants of reactions of intramolecular
hydrogen atom transfer, decyclization, and decomposition of alkoxyl radicals of artemisinin and several its derivatives, as
well as the activation energies and rate constants of reactions of these radicals with the C-H, S-H, and O-H bonds in biological
substrates and their analogs were calculated by the intersecting parabolas method The fastest reactions of artemisinin alkoxyl
radicals were identified. The full kinetic scheme of transformation of these radicals was proposed. Artemisinin radicals with
the free valence on the carbon atom are predominantly formed due to the transformation of the artemisininoxyl radicals.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1502–1510, September, 2006. 相似文献