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排序方式: 共有379条查询结果,搜索用时 15 毫秒
111.
Rahul Kar Jong‐Won Song Takeshi Sato Kimihiko Hirao 《Journal of computational chemistry》2013,34(27):2353-2359
Density functional theory, in general, is considered to underestimate the weak van der Waals type of intermolecular interactions. We optimized parameters of the local response dispersion (LRD) method applied to the long‐range corrected exchange‐correlation functionals (LC‐BOP12+LRD and LCgau‐BOP+LRD) on the interaction energy for the complexes in the recently compiled S66 database and found to be comparable with the high‐level wave function‐based methods reported in ?ezá? et al. (J. Chem. Theory Comput. 2011 , 7, 2427). Our calculations with the S66 intermolecular complexes at equilibrium geometries suggests that the LC‐BOP12+LRD and LCgau‐BOP+LRD are well‐balanced and lower cost alternatives to the methods reported in the database. Further, test on the S66X8 database (with eight nonequilibrium points) and the HBC6 and NBC10 database shows LC+LRD method with newly optimized parameters is a promising candidate for dealing such weak interactions. Finally, the new parameterized LC+LRD method was tested on X40 benchmark halogenated complexes.Copyright © 2013 Wiley Periodicals, Inc. 相似文献
112.
Nilay K. Pramanik Ramsankar Haldar Utpal K. Niyogi MD. Sarwar Alam 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(4):296-307
The non-isothermal crystallization kinetics was studied by differential scanning calorimetric analysis on nylon 66 and e-beam irradiated nylon 66 at different cooling rates. The Modified Avrami equation, the Ozawa equation and the Combined Avrami-Ozawa equation were applied to study the kinetics of non-isothermal crystallization of nylon 66. The crystallization behavior of pristine nylon 66 polymer was compared with that of e-beam irradiated nylon 66 and observed that the kinetics of non-isothermal crystallization of nylon66 was affected largely upon e-beam irradiation. E-beam irradiation not only decreased the crystallization temperature of nylon 66, but influenced the mechanism of nucleation and crystal growth and reduced the overall crystallization rate of nylon 66 also. The crystallization activation energy calculated by the Kissinger method for irradiated nylon 66 was lower than that of pristine nylon 66. 相似文献
113.
Jaeheon Lee Dongwon Ka Heesoo Jung Kyeongmin Cho Youngho Jin Minkun Kim 《Molecules (Basel, Switzerland)》2021,26(13)
Composites of metal-organic frameworks and carbon materials have been suggested to be effective materials for the decomposition of chemical warfare agents. In this study, we synthesized UiO-66-NH2/zeolite-templated carbon (ZTC) composites for the adsorption and decomposition of the nerve agents sarin and soman. UiO-66-NH2/ZTC composites with good dispersion were prepared via a solvothermal method. Characterization studies showed that the composites had higher specific surface areas than pristine UiO-66-NH2, with broad pore size distributions centered at 1–2 nm. Owing to their porous nature, the UiO-66-NH2/ZTC composites could adsorb more water at 80% relative humidity. Among the UiO-66-NH2/ZTC composites, U0.8Z0.2 showed the best degradation performance. Characterization and gas adsorption studies revealed that beta-ZTC in U0.8Z0.2 provided additional adsorption and degradation sites for nerve agents. Among the investigated materials, including the pristine materials, U0.8Z0.2 also exhibited the best protection performance against the nerve agents. These results demonstrate that U0.8Z0.2 has the optimal composition for exploiting the degradation performance of pristine UiO-66-NH2 and the adsorption performance of pristine beta-ZTC. 相似文献
114.
This study mainly shows that in the Fe66Pd30Rh4 (at%) alloys, the L10 phase plays an important role in magnetostriction due to the interplay of L10 martensitic twins with magnetic domains. The L10 martensitic twin structure exhibits a strong magnetocrystalline anisotropy energy constant (Ku=1.27-2.84×106 (ergs/cm3)) along the tetragonal c axis direction. In addition, the L10 tetragonal martensitic twin structure shows both a perfect shape memory and a reversible shape memory effect; therefore, it is expected to be applicable in magneto-mechanical applications (such as microactuators or springs). However, in this study, we discover that solution treatment (ST) and aging heat treatments of Fe66Pd30Rh4 ferromagnetic shape memory alloys influence the behavior of the martensitic transition, which is associated with the change in magnetic properties. The process of a thermoelastic L10+L1m twin phase decomposition→non-thermoelastic L10+L1m+αbct structure in Fe66Pd30Rh4 alloys during solution treatment and aging at 400-550 °C for various times is studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The relation of phase separation morphology to the magnetic property change is examined with a superconducting quantum interference device (SQUID) magnetometer, and magnetostriction measurement is performed with a strain gage method and magnetostrictive meter setup. The results indicate that the process of martensitic transformation during aging leads to an increase in coercivity and a decrease in magnetostriction, simultaneously. 相似文献
115.
Xiaomeng Shan Tao Pan Yuting Pan Wenchang Wang Xiaohui Chen Xueling Shan Zhidong Chen 《Electroanalysis》2020,32(3):462-469
In this study, a novel electrochemiluminescence (ECL) sensor for highly sensitive and selective detection of Pb(II) was developed based on Ru(bpy)32+ encapsulated UiO66 metal‐organic‐framework (Ru(bpy)32+?UiO66 MOF) and ?NH2 group functionalized silica (NH2?SiO2). The NH2?SiO2 with large surface area provided an excellent platform for the ECL sensor. As numerous exposed carboxyl groups were present on UiO66 backbone, the Ru(bpy)32+?UiO66 could be steadily immobilized to NH2?SiO2 by forming amide bonds. Meanwhile, the introduced UiO66 MOF which used for the encapsulation of Ru(bpy)32+, significantly enhanced the ECL efficiency of the proposed sensor, as it possessed a large specific surface area and porosity for the loading of Ru(bpy)32+. Moreover, a high quenching effect on ECL intensity was obtained in the presence of Pb(II) in the electrolyte. Under the optimal conditions, the quenched ECL intensity showed a good linear relationship within Pb(II) concentration in the range from 1.0×10?6 to 1.0×102 μM, with a detection limit of 1.0×10?7 μM (S/N=3). The proposed sensor for Pb(II) detection was simple in operation, rapid in testing, stable in signal, and showed a good anti‐interference ability to some other metal ions. Besides, its application for detecting Pb(II) in a real sample was also investigated here. This work provides a potential platform for metal ions detection in environmental monitoring field. 相似文献
116.
117.
For the complex Clifford algebra (p, q) of dimension n = p + q we define a Hermitian scalar product. This scalar product depends on the signature (p, q) of Clifford algebra. So, we arrive at unitary spaces on Clifford algebras. With the aid of Hermitian idempotents we suggest
a new construction of, so called, normal matrix representations of Clifford algebra elements. These representations take into
account the structure of unitary space on Clifford algebra.
The work of N.M. is supported in part by the Russian President’s grant NSh-6705.2006.1. 相似文献
118.
G. Stacey Staples 《Advances in Applied Clifford Algebras》2008,18(1):75-92
Generating functions are commonly used in combinatorics to recover sequences from power series expansions. Convergence of
formal power series in Clifford algebras of arbitrary signature is discussed. Given , powers of u are recovered by expanding (1 − tu)−1 as a polynomial in t with Clifford-algebraic coefficients. It is clear that (1 − tu)(1 + tu + t
2
u
2 + ...) = 1, provided the sum (1 + tu + t
2
u
2 + ...) exists, in which case u
m
is the Cliffordalgebraic coefficient of t
m
in the series expansion of (1 − tu)−1. In this paper, conditions on for the existence of (1 − tu)−1 are given, and an explicit formulation of the generating function is obtained. Allowing A to be an m × m matrix with entries in , a “Clifford-Frobenius” norm of A is defined. Norm inequalities are then considered, and conditions for the existence of (I − tA)−1 are determined. As an application, adjacency matrices for graphs are defined with vectors of as entries. For positive odd integer k > 3, k-cycles based at a fixed vertex of a graph are enumerated by considering the appropriate entry of A
k
. Moreover, k-cycles in finite graphs are enumerated and expected numbers of k-cycles in random graphs are obtained from the norm of the degree-2k part of tr(1 − tu)−1. Unlike earlier work using commutative subalgebras of , this approach represents a “true” application of Clifford algebras to graph theory.
相似文献
119.
Jiazhen Cao Dr. Zhenmin Xu Yao Chen Shuangjun Li Yue Jiang Lele Bai Prof. Han Yu Prof. Hexing Li Prof. Zhenfeng Bian 《Angewandte Chemie (International ed. in English)》2023,62(18):e202302202
Designing adsorption materials with high adsorption capacities and selectivities is highly desirable for precious metal recovery. Desorption performance is also particularly crucial for subsequent precious metal recovery and adsorbent regeneration. Herein, a metal–organic framework (MOF) material (NH2-UiO-66) with an asymmetric electronic structure of the central zirconium oxygen cluster has an exceptional gold extraction capacity of 2.04 g g−1 under light irradiation. The selectivity of NH2-UiO-66 for gold ions is up to 98.8 % in the presence of interfering ions. Interestingly, the gold ions adsorbed on the surface of NH2-UiO-66 spontaneously reduce in situ, undergo nucleation and growth and finally achieve the phase separation of high-purity gold particles from NH2-UiO-66. The desorption and separation efficiency of gold particles from the adsorbent surface reaches 89 %. Theoretical calculations indicate that -NH2 functions as a dual donor of electrons and protons, and the asymmetric structure of NH2-UiO-66 leads to energetically advantageous multinuclear gold capture and desorption. This adsorption material can greatly facilitate the recovery of gold from wastewater and can easily realize the recycling of the adsorbent. 相似文献
120.
Shou-Jun Jian Qian-Qian Han Huai-Xia Yang Xiang-Ru Meng 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(7):530-535
Metal–organic frameworks (MOFs) based on multidentate N‐heterocyclic ligands involving imidazole, triazole, tetrazole, benzimidazole, benzotriazole or pyridine present intriguing molecular topologies and have potential applications in ion exchange, magnetism, gas sorption and storage, catalysis, optics and biomedicine. The 2‐[(1H‐1,2,4‐triazol‐1‐yl)methyl]‐1H‐benzimidazole (tmb) ligand has four potential N‐atom donors and can act in monodentate, chelating, bridging and tridentate coordination modes in the construction of complexes, and can also act as both a hydrogen‐bond donor and acceptor. In addition, the tmb ligand can adopt different coordination conformations, resulting in complexes with helical structures due to the presence of the flexible methylene spacer. A new three‐dimensional coordination polymer, poly[[bis(μ2‐benzene‐1,4‐dicarboxylato)‐κ4O1,O1′:O4,O4′;κ2O1:O4‐bis{μ2‐2‐[(1H‐1,2,4‐triazol‐1‐yl)methyl‐κN4]‐1H‐benzimidazole‐κN3}dizinc(II)] trihydrate], {[Zn(C8H4O4)(C10H9N5)]·1.5H2O}n, has been synthesized by the reaction of ZnCl2 with tmb and benzene‐1,4‐dicarboxylic acid (H2bdic) under solvothermal conditions. There are two crystallographically distinct bdic2− ligands [bdic2−(A) and bdic2−(B)] in the structure which adopt different coordination modes. The ZnII ions are bridged by tmb ligands, leading to one‐dimensional helical chains with different handedness, and adjacent helices are linked by bdic2−(A) ligands, forming a two‐dimensional network structure. The two‐dimensional layers are further connected by bdic2−(B) ligands, resulting in a three‐dimensional framework with the topological notation 66. The IR spectra and thermogravimetric curves are consistent with the results of the X‐ray crystal structure analysis and the title polymer exhibits good fluorescence in the solid state at room temperature. 相似文献