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961.
John Bentley Dr. Salil Desai Dr. Bishnu Prasad Bastakoti 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(36):9241-9252
Tungsten oxide (WO3) has received ever more attention and has been highly researched over the last decade due to its being a low-cost transition metal semiconductor with tunable, yet widely stable, band gaps. This minireview briefly highlights the challenges in the design and synthesis of porous WO3 including methods, precursors, solvent effects, crystal phases, and surface activities of the porous WO3 base material. These topics are explored while also drawing a connection of how the morphology and crystal phase affect the band gap. The shifts in band gap not only impact the optical properties of tungsten but also allow tuning to operate on different energy levels, which makes WO3 highly desirable in many applications such as supercapacitors, batteries, solar cells, catalysts, sensors, smart windows, and bioapplications. 相似文献
962.
Dr. Sara Sabater Dr. David Schmidt Dr. Heidi Schmidt Dr. Maximilian W. Kuntze-Fechner Dr. Thomas Zell Connie J. Isaac Dr. Nasir A. Rajabi Harry Grieve Dr. William J. M. Blackaby Dr. John P. Lowe Prof. Stuart A. Macgregor Dr. Mary F. Mahon Prof. Dr. Udo Radius Prof. Michael K. Whittlesey 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(52):13221-13234
The addition of PPh2H, PPhMeH, PPhH2, P(para-Tol)H2, PMesH2 and PH3 to the two-coordinate Ni0 N-heterocyclic carbene species [Ni(NHC)2] (NHC=IiPr2, IMe4, IEt2Me2) affords a series of mononuclear, terminal phosphido nickel complexes. Structural characterisation of nine of these compounds shows that they have unusual trans [H−Ni−PR2] or novel trans [R2P−Ni−PR2] geometries. The bis-phosphido complexes are more accessible when smaller NHCs (IMe4>IEt2Me2>IiPr2) and phosphines are employed. P−P activation of the diphosphines R2P−PR2 (R2=Ph2, PhMe) provides an alternative route to some of the [Ni(NHC)2(PR2)2] complexes. DFT calculations capture these trends with P−H bond activation proceeding from unconventional phosphine adducts in which the H substituent bridges the Ni−P bond. P−P bond activation from [Ni(NHC)2(Ph2P−PPh2)] adducts proceeds with computed barriers below 10 kcal mol−1. The ability of the [Ni(NHC)2] moiety to afford isolable terminal phosphido products reflects the stability of the Ni−NHC bond that prevents ligand dissociation and onward reaction. 相似文献
963.
Reversible alkylation of the C-terminal amide-bond of a protected peptide segment with 2-hydroxy-4-methoxybenzyl dramatically suppresses epimerisation during activation and coupling. However, due to the formation of a 4,5-dihydro-8-methoxy-1,4-benzoxazepin-2(3H)-one species upon activation the rate of coupling is low. A safety-catch amide-bond protecting group, 6-hydroxy-5-methyl-1,3-benzoxathiolyl, has been designed to suppress epimerisation and couple with excellent yield. 相似文献
964.
The analysis of thermal insulation materials by optical microscopy has centered on the identification of fibrous constituents and not the bulk insulation. To enhance the identification of insulation, procedures were developed using chemical spot tests and microscopical observations that included dispersion staining to characterize the matrix material. 相似文献
965.
966.
967.
968.
After describing simplified equations exspressing the temparature dependency of the viscosity of carrier gases (helium, nitrogen and hydrogen ) relative to a base value, absolute relationships based on the kinetic theory of gases are discussed. Comparative data obtained using various calculation methods are given and are compared to measured values. Based on the kinetic relationshipsm, of viscosity. Finally, the influence of pressure on the viscosity is also briefly discussed. As a supplement, Viscosity data are tabulated for the three gases in the range of 0°C to 400°C in increments of 2 K, calculated using the kinetic relationships. 相似文献
969.
970.
John Bethke Jürgen Kopf Paul Margaretha Bernard Pignon Léon Dupont Léon E. Christiaens 《Helvetica chimica acta》1997,80(6):1865-1868
Irradiation (λ = 350 nm) of 1H-[2]benzothiopyran-1-one ( 2 ) in the solid state affords selectively and in good yield 6aα, 6bα, 12bα, 12cα -tetrahydrocyclobuta[1, 2-c:4, 3-c′]bis([2]benzothiopyran)-5, 8-dione ( 3 ), the head-to-head (HH) cis-cisoid-cis-cyclodimer of 2 , X-Ray analysis of 2 confirms that this reaction proceeds according to the well-established topochemical principles. The same dimer 3 is obtained in low yields on irradiation of 10−1 M solutions of 2 in either MeOH or MeCN, while no conversion at all is observed in benzene. On irradiation of 2 in MeCN in the presence of tetrachloroethene, the [2 + 2] photocycloadduct 4 is formed in good yield, the conversion 2 → 4 being efficiently quenched by naphthalene. In contrast, no reaction is observed -on irradiation of 2 in the presence of 2, 3-dimethylbut-2-ene, neither in polar nor in apolar solvents. 相似文献