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991.
Recently,muchefforthasbeenmadeinthedevelopmentofgenerallyapplicableorganicsynthesisof5hydroxy2(5H)furanone1duetoitsessentialstructureentityinthesynthesisofsomebiologicallyactivenaturalproductsanditsapplicationasausefulintermediateinorganicsynthesis[1—3].Co… 相似文献
992.
Joseph Grobe Elke Maria Reifer Bernt Krebs Mechtild Lge Markus Prill 《无机化学与普通化学杂志》2000,626(2):478-488
Alternative Ligands. XXXV. Syntheses of Bidentate P‐Donor/Sn‐Acceptor Ligands: Coordination Experiments with Cp*Rh(CO)2 and CpRh(C2H4)2 Donor/acceptor ligands Me2Sn(CH2CH2PMe2)2 ( 1 ) and Me2Sn(OCH2PMe2)2 ( 2 ) have been prepared by radical reaction of Me2PVi with Me2SnH2 and by substitution of chlorine in Me2SnCl2 or of ethoxy groups in Me2Sn(OEt)2 by MOCH2PMe2 (M = Li, Na) and HOCH2PMe2, respectively. 2 cannot be isolated in pure form from the product mixture because, due to condensation reactions, the “ladder structure” [Me2Sn(OCH2PMe2)2OSnMe2]2 ( 3 ) is formed. The molecular structure of 3 was determined by X‐ray diffraction studies of single crystals. Attempts to produce the thiophosphoryl derivative of 3 result in the degradation of the ladder structure giving the thermally labile phosphane sulfide Me2Sn(OCH2P(S)Me2)2. Ligands 1 and 2 besides Me2PCH2CH2SnMe3 ( 4 ) have been used for the preparation of rhodium(I) complexes from Cp*Rh(CO)2 ( 5 ) or CpRh(C2H4)2 ( 10 ) as educts. The thermal reaction of 5 with 4 yields Cp*Rh(CO)PMe2CH2CH2SnMe3 ( 6 ), that of 5 with 1 a mixture of the mononuclear derivative Cp*Rh(CO) · PMe2CH2CH2SnMe2CH2CH2PMe2 ( 7 ) and the binuclear complex [Cp*Rh(CO)PMe2CH2CH2]2SnMe2 ( 8 ). The related system [Cp*Rh(CO)PMe2CH2O]2SnMe2 produced by reaction of 5 with 2 can only be detected in solution but, because of some side‐products, was not fully characterized. From 10 and 4 a mixture of mono‐ and disubstituted products, CpRh(C2H4)PMe2CH2CH2SnMe3 ( 11 ) and CpRh(PMe2CH2CH2SnMe3)2 ( 12 ), is obtained. Reaction of 1 with 10 yields a mixture of the complexes CpRh(C2H4)PMe2CH2CH2SnMe2CH2CH2PMe2 ( 13 ) and CpRh(Me2CH2CH2)2SnMe2 ( 14 ). Some of the NMR data (13C, δδSn) of 14 can be interpreted in terms of the expected Rh → Sn interaction. A definite proof by X‐ray diffraction on single crystals, so far, was not possible. 相似文献
993.
Robert E. Dinnebier Matthias Wagner Frank Peters Kenneth Shankland William I. F. David 《无机化学与普通化学杂志》2000,626(6):1400-1405
The crystal structure of [(C5H4BMe2)2Fe]‐4,4′‐bipyridine [ 2 · bipy]n has been determined by the method of simulated annealing from high resolution X‐ray powder diffraction at room temperature. The compound is of interest, because it proves that highly ordered organometallic macromolecules can be formed in the solid state via the self‐assembly of N–B‐donor‐acceptor bonds. [ 2 · bipy]n crystallizes in the triclinic space group, P 1, Z = 2, with unit cell parameters of a = 8.3366(2) Å, b = 11.4378(3) Å, c = 12.6740(5) Å, α = 112.065(2)°, β = 108.979(1)°, γ = 90.551(2)°, and V = 1047.06(6) Å3. For the structure solution of [ 2 · bipy]n 11 degrees of freedom (3 translational, 3 orientational, 5 torsion angles) were determined within several hours, demonstrating that the crystal packing and the molecular conformation of medium sized (< 50 non‐hydrogen atoms) coordination compounds can nowadays be solved routinely from high resolution powder diffraction data. 相似文献
994.
Jin‐jian Liu 《应用有机金属化学》2019,33(1)
Three 1‐methyl‐4,4′‐bipyridinium (MQ+)‐based complexes, {[Cd(MQ)(p‐BDC)Br]?H2O}n ( 1 ), {[Cd(MQ)(m‐BDC)(H2O)Br]?3H2O}n ( 2 ) and Cu(MQ)Br2 ( 3 ) (p‐H2BDC = 1,4‐benzenedicarboxylic acid, m‐H2BDC = 1,3‐benzenedicarboxylic acid), have been synthesized and structurally characterized. Compounds 1 and 2 are one‐dimensional coordination polymers constituted of one coordinated MQ+ cation, one coordinated Br? ion and chains of Cd2+ ions connected by deprotonated BDC2? units, which both have photochromism but different decolorization behaviors. The structures and photoresponsive behaviors controlled by auxiliary ligands have been explored. Compound 3 is constituted of one Cu+ center, one MQ+ ligand and two coordinated Br? ions in a ‘V’ configuration, exhibiting no photochromism. 相似文献
995.
Xiao Hua Jing-Si Bai Yi-Fu Kong Guo-Chao Chu Jing Shi Yi-Ming Li 《Tetrahedron letters》2019,60(41):151123
Atypical ubiquitin (Ub) chains are generally involved in intracellular physiological processes, while the molecular mechanisms underlying their regulation remain unclear. In this work, we report an acid-sensitive auxiliary group based bifunctional handle that can prepare Lys27-, Lys29- and Lys33-diUb analogs by thiol-ene coupling (TEC) in combination with native chemical ligation (NCL). A prominent advantage of this method is the rapid and effective removal of acid-sensitive auxiliary groups after the formation of the isopeptide bond mimic. Collectively, this work illustrates the utility of the new strategy in the simple and efficient production of homogeneous atypical diUb analogs for biochemical and biophysical studies. 相似文献
996.
Georgii Bogdanov John P. Tillotson Victor N. Khrustalev Sergei Rigin Tatiana V. Timofeeva 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(8):1175-1181
The synthesis, crystal structure studies and solvatochromic behavior of 2‐{(2E,4E)‐5‐[4‐(dimethylamino)phenyl]penta‐2,4‐dien‐1‐ylidene}malononitrile, C16H15N3 (DCV[3]), and 2‐{(2E,4E,6E)‐7‐[4‐(dimethylamino)phenyl]hepta‐2,4,6‐trien‐1‐ylidene}malononitrile, C18H17N3 (DCV[4]), are reported and discussed in comparison with their homologs having a shorter length of the π‐conjugated bridge. The compounds of this series have potential use as nonlinear materials with second‐order effects due to their donor–acceptor structures. However, DCV[3] and DCV[4] crystallized in the centrosymmetric space group P21/c which excludes their application as nonlinear optical materials in the crystalline state. They both crystallize with two independent molecules having the same molecular conformation in the asymmetric unit. The series DCV[1]–DCV[4] demonstrated reversed solvatochromic behavior in toluene, chloroform, and acetonitrile. 相似文献
997.
O. A. Raevsky 《SAR and QSAR in environmental research》2013,24(4):367-381
Abstract QSARs based on molecular polarizability (α) and H-bond acceptor factors (∑Ca) as independent variables provided good predictability of octanol/water partition coefficients (P) for chemicals and drugs. However, for some molecules containing few functional groups, the calculated values deviated significantly from those observed. This approach gave good results when applied to a set of 138 chemicals and drugs previously studied by Mannhold and Dross who compared other methods to calculate log P values. At the same time, three variations on a molecular similarity approach were pursued. In this study, a large training set with experimentally determined octanol/water partition coefficients (P) was searched for structures closely related to the compound-of-interest. The most successful of these variations took the mean log P value of few most closely related compounds after each was adjusted for differences between their and the compound-of-interest's polarizabilities (α) and H-bond acceptor capacities (∑Ca). 相似文献
998.
Łukasz Kielesiński Prof. Daniel T. Gryko Prof. Andrzej L. Sobolewski Dr. Olaf Morawski 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(67):15305-15314
Coumarins are classic, strongly polarized fluorophores with multiple applications, and significant efforts have been put into modifying their emission characteristics and elucidating their photophysics. Expecting that π-expansion of these donor–acceptor chromophores could modify their ground- and excited-state characteristics, the authors performed combined, detailed photophysical and computational studies of linearly π-expanded coumarins, that is, 8-dialkylamino-3-carboxyalkyl-benzo[g]coumarins. The investigation led to the conclusion that emission is only possible thanks to the stabilizing effect of the solvent and that breaking of the lactone ring leads to the conical intersection with the ground state and induces the radiationless decay of the electronic excitation. Aiming at the fine-tuning the excited state properties through the construction of covalently linked dye assemblies, the authors designed and synthesized a new bis(benzo[g]coumarin), built from two similar moieties that exhibit different degrees of polarization due to the electron donor at position 8: one possesses a dialkylamino, and the other a weaker amide donor. Comprehensive studies have shown that the observed weak fluorescence of the system is the result of the interplay between the solvation-induced separation of the benzo[g]coumarin moieties, which stabilizes the emitting locally excited singlet state and the π-stacking interactions, favoring their sandwiched orientation and leading to the non-emissive charge-transfer state. 相似文献
999.
1000.
Kizhmuri P. Divya Sivaramapanicker Sreejith Dr. Cherumuttathu H. Suresh Divya S. Philips Dr. Ayyappanpillai Ajayaghosh 《化学:亚洲杂志》2013,8(7):1579-1586
An unprecedented, positional effect of the isomeric repeat unit on chain folding in donor–acceptor‐linked oligomers, which contain alternating bipyridine and carbazole moieties that are connected through an acetylinic linkage, is reported. 4,4′‐Linked oligomer 1 adopts an intrachain helical conformation (CD‐active) in CHCl3/MeCN (20:80 v/v), whereas oligomer 2 , which contains an isomeric 6,6′‐linkage, forms interchain randomly coiled aggregates (CD‐inactive). The substitution position plays a significant role in controlling the variations in electronic effects and dipole moments around the bipyridyl moiety, which are responsible for this observed phenomenon. Two model compounds of oligomers 1 and 2 ( 3 and 4 , respectively) were prepared and their properties were compared. A systematic investigation of the photophysical and CD properties of these structures, as well as theoretical studies, support our conclusions. 相似文献