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991.
Ramadan Ahmed Mekheimer Afaf Mohamed Abd El‐Hameid Kamal U. Sadek 《Journal of heterocyclic chemistry》2008,45(1):97-101
992.
Mohamed. R. Aouad Nadje T. Rezki El Sayed H. El Ahsry 《Journal of heterocyclic chemistry》2008,45(5):1321-1327
993.
Saleh M. Al‐Mousawi Morsy A. El‐Apasery Najat Al‐Kandery Mohamed H. Elnagdi 《Journal of heterocyclic chemistry》2008,45(2):359-364
994.
M. El Masloumi V. Jubera J.P. Chaminade M. Mesnaoui B. Moine 《Journal of solid state chemistry》2008,181(11):3078-3085
Single crystals of NaY(PO3)4 and Ag0.07Na0.93Y(PO3)4 have been synthesized by flux method. These new compounds turned out to be isostructural to NaLn(PO3)4, with Ln=La, Nd, Gd and Er [monoclinic, P21/n, a=7.1615(2) Å, b=13.0077(1) Å, c=9.7032 (3) Å, β=90.55 (1)°, V=903.86(14) Å3 and Z=4]. The structure is based upon long polyphosphate chains running along the shortest unit-cell direction and made up of PO4 tetrahedra sharing two corners, linked to yttrium and sodium polyhedra. Infrared and Raman spectra at room temperature confirms this atomic arrangement. The luminescence of silver ions was reported in metaphosphate of composition Ag0.07Na0.93Y(PO3)4. One luminescent centre was detected and assigned to single Ag+ ions. 相似文献
995.
Somnath Roy Tarak Nath Mandal Anil Kumar Barik Samik Gupta Ray J. Butcher Mohamed Salah El Fallah Javier Tercero Susanta Kumar Kar 《Polyhedron》2008
The synthesis and structure of a pyrazole-based orthogonal ferromagnetically coupled tetracopper(II) 2 × 2 homoleptic grid complex [Cu4(PzOAPyz)4(ClO4)2](ClO4)2 · 6H2O (1), formed by the reaction between the ditopic ligand PzOAPyz and Cu(ClO4)2 · 6H2O, are described. The ligand contains terminal pyrazole and pyrazine residues bound to a central flexible diazine subunit (N–N) as well as one potentially bridging alkoxo group. The two adjacent metal centers are linked by an alkoxo oxygen forming essentially a square Cu4(μ-O4) cluster. In the Cu4(μ-O4) core, out of the four copper centers, two copper centers are penta-coordinated and the remaining two are hexa-coordinated. In each case of hexa-coordination, the sixth position is occupied by one of the oxygen atoms of a coordinated perchlorate ion. Complex 1 has been characterized structurally and magnetically. Although the large Cu–O–Cu bridge angles (137–138°) and short Cu–Cu distances (3.964–3.970 Å) are suitable for the transmission of the expected antiferromagnetic coupling, the square-based Cu4(μ-O4) cluster exhibits an intramolecular ferromagnetic exchange (J = 7.47 cm−1) between the metal centers with an S = 2 magnetic ground state associated with the quasi orthogonal arrangement of the magnetic orbitals (dx2-y2). The exchange pathway parameters have been evaluated from density functional calculations. 相似文献
996.
Dr. Samuel F. Haysom Jonathan Machin Dr. James M. Whitehouse Dr. Jim E. Horne Dr. Katherine Fenn Dr. Yue Ma Dr. Hassane El Mkami Dr. Nils Böhringer Prof. Dr. Till F. Schäberle Prof. Dr. Neil A. Ranson Prof. Dr. Sheena E. Radford Prof. Dr. Christos Pliotas 《Angewandte Chemie (International ed. in English)》2023,62(34):e202218783
The β-barrel assembly machinery (BAM complex) is essential for outer membrane protein (OMP) folding in Gram-negative bacteria, and represents a promising antimicrobial target. Several conformational states of BAM have been reported, but all have been obtained under conditions which lack the unique features and complexity of the outer membrane (OM). Here, we use Pulsed Electron-Electron Double Resonance (PELDOR, or DEER) spectroscopy distance measurements to interrogate the conformational ensemble of the BAM complex in E. coli cells. We show that BAM adopts a broad ensemble of conformations in the OM, while in the presence of the antibiotic darobactin B (DAR-B), BAM′s conformational equilibrium shifts to a restricted ensemble consistent with the lateral closed state. Our in-cell PELDOR findings are supported by new cryoEM structures of BAM in the presence and absence of DAR-B. This work demonstrates the utility of PELDOR to map conformational changes in BAM within its native cellular environment. 相似文献
997.
James R. Durig Ahmed M. El Defrawy Rachel M. Ward Gamil A. Guirgis Todor K. Gounev 《Structural chemistry》2008,19(4):579-594
Variable temperature (?55 to ?105 °C) studies of the infrared spectra (4000–400 cm?1) of chlorocyclohexane (c-C6H11Cl) dissolved in liquefied xenon have been carried out. The infrared spectra of the gas and solid have also been recorded from 4000–100 cm?1. By analyzing six conformer pairs in the xenon solution, a standard enthalpy difference of 132 ± 13 cm?1 (1.58 ± 0.16 kJ/mol) was obtained with the equatorial conformer the more stable form. At ambient temperature, the abundance of the axial conformer is 34 ± 1%. The potential surface describing the conformational interchange has been determined and the Fourier coefficients were obtained. From MP2 ab initio calculations utilizing various basis sets with and without diffuse functions, the equatorial conformer is predicted to be more stable by 161 ± 18 cm?1 from the four largest basis set calculations, which is consistent with the experimental results. However, the average from the corresponding B3LYP density functional theory calculations is 274 ± 15 cm?1 which is certainly too large. By utilizing the previously reported microwave rotational constants for two isotopomers (35Cl, 37Cl) combined with the structural parameters predicted from the MP2(full)/6-311+G(d,p) calculations, adjusted r 0 structural parameters have been obtained. The determined heavy atom distances for the most stable chair-equatorial conformer in Å are: r 0(C1–C7,8) = 1.532(3); r 0(C7,8–C13,14) = 1.536(3); r 0(C4–C13,14) = 1.524(3); and r 0(C4–Cl6) = 1.802(5) and the angles in degrees: ∠C1C7,8C13,14 = 111.3(5)º; ∠Cl6C4C13,14 = 109.7(5)º with the two dihedral angles ∠C8C1C7C13 = 56.3(10)º and ∠C14C4C13C7 = 56.7(10)º. These parameters are in good agreement with those reported earlier from microwave and electron diffraction studies where the CC and CH distances were all assumed to be equal. A few of the previously reported vibrational assignments have been corrected. The results of these spectroscopic and theoretical studies are discussed and compared to the corresponding results for some similar molecules. 相似文献
998.
Thillaye du Boullay O Bonduelle C Martin-Vaca B Bourissou D 《Chemical communications (Cambridge, England)》2008,(15):1786-1788
Well-controlled poly(alpha-hydroxyacids) featuring pendant carboxylic acid groups were prepared under mild conditions via DMAP-catalyzed ROP of the O-carboxyanhydrides derived from glutamic and lactic acids. 相似文献
999.
Abdellah El Kinani Amine Mohammed Nejjari Mohamed Oudadess 《Mediterranean Journal of Mathematics》2008,5(1):33-42
We use positive elements of Hermitian algebras to give results on automatic continuity of algebra morphisms. Consequences
and applications are also given.
相似文献
1000.
Dr. Jamal El Bakali Dr. Michal Blaszczyk Dr. Joanna C. Evans Dr. Jennifer A. Boland Dr. William J. McCarthy Imam Fathoni Dr. Marcio V. B. Dias Dr. Eachan O. Johnson Dr. Anthony G. Coyne Prof. Valerie Mizrahi Prof. Tom L. Blundell Prof. Chris Abell Dr. Christina Spry 《Angewandte Chemie (International ed. in English)》2023,62(17):e202300221
The coenzyme A (CoA) biosynthesis pathway has attracted attention as a potential target for much-needed novel antimicrobial drugs, including for the treatment of tuberculosis (TB), the lethal disease caused by Mycobacterium tuberculosis (Mtb). Seeking to identify inhibitors of Mtb phosphopantetheine adenylyltransferase (MtbPPAT), the enzyme that catalyses the penultimate step in CoA biosynthesis, we performed a fragment screen. In doing so, we discovered three series of fragments that occupy distinct regions of the MtbPPAT active site, presenting a unique opportunity for fragment linking. Here we show how, guided by X-ray crystal structures, we could link weakly-binding fragments to produce an active site binder with a KD <20 μM and on-target anti-Mtb activity, as demonstrated using CRISPR interference. This study represents a big step toward validating MtbPPAT as a potential drug target and designing a MtbPPAT-targeting anti-TB drug. 相似文献