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101.
En‐Qing Gao Dai‐Zheng Liao Zong‐Hui Jiang Shi‐Ping Yan 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(7):807-809
A hydrogen‐bonded coordination supramolecule, (meso‐5,7,7,12,14,14‐hexamethyl‐1,4,8,11‐tetraazacyclotetradecane‐κ4N)nickel(II) [N,N‐o‐phenylenebis(oxamato)‐κ4O,N,N′,O′]nickelate(II) dihydrate, [Ni(C16H36N4)][Ni(C10H4N2O6)]·2H2O or [Ni(meso‐cth)][Ni(opba)]·2H2O, has been prepared and characterized by X‐ray crystallographic analysis. The two complex ions, i.e. [Ni(meso‐cth)]2+ and [Ni(opba)]2?, are hydrogen bonded to each other, resulting in two‐dimensional neutral supramolecular sheets. The sheets stack along the a direction to produce a three‐dimensional architecture with one‐dimensional channels in which hydrogen‐bonded chains of water molecules are included. 相似文献
102.
Lei Zhang Zhi‐Liang Liu Lin‐Hong Weng Dai‐Zheng Liao Zong‐Hui Jiang Shi‐Ping Yan Pan‐Wen Shen Martin Baumgarten 《Helvetica chimica acta》2001,84(4):834-841
The structure of a novel oxido‐aminoxyl (=`nitronyl nitroxide') biradical, 2,2′‐(1‐oxidopyridine‐2,6‐diyl)bis[4,5‐dihydro‐4,4,5,5‐tetramethyl‐3‐oxido‐1H‐imidazol‐1‐oxyl] hydrate ( 1 ⋅H2O) was established by X‐ray analysis in the solid state: monoclinic, space group P21/c, Z=4 with a=12.621(4), b=15.704(5), and c=13.001(4) Å, and β=115.202(6)°. Variable‐temperature magnetic susceptibilities show a weak antiferromagnetic interaction between the two oxido‐substituted aminoxyl moieties of 1 , indicative of a singlet ground state. AM1 Calculations located minima for the possible structure based on the X‐ray crystal structure. A hybride density‐functional‐theory calculation with the UB3LYP method from the X‐ray crystal structure establishes the same spin sign in the two aminoxyl moieties and shows that a small spin density is localized at the C‐atoms of the pyridine moiety. These theoretic results are in good agreement with the determined weak antiferromagnetic interaction of 1 . 相似文献
103.
The principle of structure correlation is applied to 28 crystal structures which contain 44 different five-coordinate molybdenum fragments. The data derived map the reaction pathway for a bimolecular ligand substitution reaction at tetrahedral molybdenum centers. The dihedral-angle method from Muetterties and Guggenberger is employed in order to describe the interconversion between the trigonal bipyramidal (TBP) and the square pyramidal (SQP) conformations via the Berry pseudorotation mechanism in the system of Mo(L)_5 complexes. This structure correlation method provides a convincing mapping of the Berry pathway in this paper. 相似文献
104.
105.
The metal anions of vanadium (V) and chromium (VI) in aqueous solution can be effectively adsorbed by Zr(IV)-impregnated collagen
fiber (ZrICF). The maximum adsorption capacity of V(V) takes place within the pH range of 5.0 to 8.0, while that of Cr(VI)
is within the pH range of 6.0 to 9.0. When the initial concentration of metal ions was 2.00 mmol L−1 and the temperature was 303 K, the adsorption capacity of V(V) on Zr-ICF was 1.92 mmol g−1 at pH 5.0, and the adsorption capacity of Cr(VI) was 0.53 mmol g−1 at pH 7.0. As temperature increased, the adsorption capacity of V(V) increased, while that of Cr(VI) was almost unchanged.
The adsorption isotherms of the anionic species of V(V) and Cr(VI) can be fit by the Langmuir equation. The adsorption rate
of V(V) follows the pseudo-first-order rate model, while the adsorption rate of Cr(VI) follows the pseudo-second-order rate
model. Furthermore, ZrICF shows high adsorption selectivity to V(V) in the mixture solution of V(V) and Cr(VI). Practical
applications of ZrICF could be expected in consideration of its performance in adsorption of V(V) and Cr(VI). 相似文献
106.
Bifunctional Ligand Enables Efficient Gold‐Catalyzed Hydroalkenylation of Propargylic Alcohol 下载免费PDF全文
Dr. Shengrong Liao Dr. Alessio Porta Xinpeng Cheng Xu Ma Prof. Dr. Giuseppe Zanoni Prof. Dr. Liming Zhang 《Angewandte Chemie (International ed. in English)》2018,57(27):8250-8254
Using the previously designed biphenyl‐2‐ylphosphine ligand, featuring a remote tertiary amino group, the first gold‐catalyzed intermolecular hydroalkenylation of alkynes has been developed. Synthetically valuable conjugated dienyl alcohols are formed in moderate to good yields. A range of alkenyltrifluoroborates are allowed as the alkenyl donor, and no erosion of alkene geometry and/or the propargylic configuration are detected. DFT calculations confirm the critical role of the remote basic group in the ligand as a general‐base catalyst for promoting this novel gold catalysis with good efficiency. 相似文献
107.
The asymmetric total synthesis of (-)-saframycin A, a natural antitumor product of the tetrahydroisoquinoline antitumor antibiotics family, has been accomplished by employing L-tyrosine as the starting chiral building block in 24 steps for the longest linear sequence in an overall yield of 9.7%. The key steps in the synthesis involve stereoselective intermolecular and intramolecular Pictet-Spengler reactions, which induced the correct stereochemistry at C-1 and C-11, respectively. The selective protection-deprotection protocol of an amino group in the two-step transformation from intermediate 10 to 12 and a hydroxyl group in the first two steps resulted in both high selectivity and efficiency of the synthetic route. 相似文献
108.
Ultrasound-assisted dispersive liquid?Cliquid microextraction (USA-DLLME) with low solvent consumption was demonstrated for gas chromatography-mass spectrometry (GC?CMS) determination of 16 typical polycyclic aromatic hydrocarbons (PAHs) in seawater samples. Factors affecting the extraction process, such as extraction and dispersive solvent, phase ratio, temperature, extraction and centrifugation time, were investigated thoroughly and optimized. The linear range was 20?C2,000 ng L?1 except for acenaphthylene (Acy) at 10?C2,000 ng L?1 and phenanthrene (Phe), fluoranthene (Flu) and pyrene (Py) all at 5?C2,000 ng L?1. Enrichment factors (EFs) ranging from 722 to 8,133 were obtained, achieving limits of detection at 1.0?C10.0 ng L?1. The method attained good precision (relative standard deviation, RSD) from 3.4 to 14.2% for spiked 50 ng L?1 individual PAHs standards. Method recoveries were in the range 87?C124% and 70?C127% for spiked samples from simulated seawater and beach seawater, respectively. The proposed USA-DLLME helped to obtain about 1.1?C10 times higher EFs in a minimum amount of solvent and in less time than traditional DLLME. 相似文献
109.
Jing Qian Qing-Lun Wang Wen Gu Jin-Lei Tian Ming-Jin Xie Shi-Ping Yan Dai-Zheng Liao Peng Cheng 《Transition Metal Chemistry》2007,32(7):847-850
Two novel μ-oxo-di-μ-carboxylato-bridged iron(III) complexes of [Fe2(bpea)2(PhCO2)2(μ-O)] (ClO4)2·C2H5OH (1) and [Fe2(bpma)2(ClCH2COO)2(μ-O)](ClO4)2· H2O (2) (bpea = N,N-bis(2-pyridylmethyl)ethylamine, bpma = N,N-bis(2-pyridylmethyl)methylamine), have been synthesized and determined by X-ray diffraction. Complex (1) crystallizes in the Orthorhombic space group P nma with d(Fe···Fe) of 3.094 Å and average d(Fe–Obbridge) of 1.805 Å; Complex (2) crystallizes in the Monoclinic space group C 2/c, with d(Fe···Fe) of 3.109 Å and average d(Fe–Obbridge) of 1.794 Å. The magnetic studies indicate a stronger antiferromagnetic interaction between iron(III) ions through μ-oxo-di-μ-carboxylato-bridge for complex (1), with J = ? 141.6 cm?1. 相似文献
110.
Two- and three-dimensional lanthanide complexes: synthesis, crystal structures, and properties 总被引:1,自引:0,他引:1
Xia J Zhao B Wang HS Shi W Ma Y Song HB Cheng P Liao DZ Yan SP 《Inorganic chemistry》2007,46(9):3450-3458
3,5-pyrazoledicarboxylic acid (H3L) reacts with nitrate salts of lanthanide(III) (Ln=Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er) under hydrothermal conditions to form a series of lanthanide polymers 1-9. These nine polymers have the same crystal system of monoclinic, but they exhibit three different kinds of metal-organic framework structures. The complexes {[Ln2(HL)3(H2O)4].2H2O}n (Ln=Pr (1), Nd (2), and Sm (3)) were isostructural and exhibited porous 3D frameworks with a Cc space group. The complexes {[Ln2(HL)3(H2O)3].3H2O}n (Ln=Eu (4), Gd (5), and Tb (6)) were isostructural and built 2D double-decker (2DD) frameworks with a P21/c space group. The complexes {[Ln(HL)(H2L)(H2O)2]}n ((Ln=Dy (7), Ho (8), and Er (9)) were also isostructural and formed 2D monolayer (2DM) frameworks with a P21/n space group. The structure variation from the 3D porous framework to the 2D double-decker to the 2D monolayer is attributed to the lanthanide contraction effect. Notably, six new coordination modes of 3,5-pyrazoledicarboxylic acid were observed, which proved that 3,5-pyrazoledicarboxylic acid may be used as an effective bridging ligand to assemble lanthanide-based coordination polymers. The photophysical and magnetic properties have also been investigated. 相似文献