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81.
A simple, rapid, sensitive, and selective method for the spectrophotometric microdetermination of silver(I) using ammonium(2′,3′-dihydroxy pyridyl-4′-azo)benzene-4-arsonate (DHP-4A), a water soluble pyridinol azo dye is proposed. The red colored 1:1 (metal to ligand) complex formed has molar extinction coefficient (ε) 2.95 × 104 1 mol−1 cm−1 and absorbs maximum at 535 nm, in highly alkaline medium. Beer's law is obeyed up to 3.36 ppm and Sandell's sensitivity (for an absorbance 0.001) is 0.0037 μg of Ag(I)/cm2. The silver(I)-(DHP-4A) complex has also been used in the microdetermination of iodide ions using ligand exchange reaction. The optimum concentration range of iodide ions which can reproducibly be determined is 1.27–37.9 μg/10 ml. 相似文献
82.
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84.
Meccanica - Designing protective armors is important for varied civil and defense applications. Ceramic-polymer composite armors are particularly interesting for their high strength and light... 相似文献
85.
Vivek Polshettiwar Dr. Rajender S. Varma Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(7):1582-1586
Magnetic attraction not filtration : A magnetic nanoparticle‐supported ruthenium hydroxide catalyst (see figure) was readily prepared from inexpensive starting materials and shown to catalyze the hydration of nitriles with excellent yield in a benign aqueous medium. Catalyst recovery using an external magnetic field, superior activity, and the inherent stability of the catalyst system are additional sustainable attributes of this protocol.
86.
Dipak Kumar Roy Dr. Shubhankar Kumar Bose K. Geetharani Kiran Kumar Varma Chakrahari Dr. Shaikh M. Mobin Dr. Sundargopal Ghosh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(32):9983-9991
The reaction of [CpnMCl4?x] (M=V: n=2, x=2; M=Nb: n=1, x=0; Cp=η5‐C5H5) with LiBH4 ? THF followed by thermolysis in the presence of dichalcogenide ligands E2R2 (E=S, Te; R=2,6‐(tBu)2‐C6H2OH, Ph) and 2‐mercaptobenzothiazole (C7H5NS2) yielded dimetallaheteroboranes [{CpV(μ‐TePh)}2(μ3‐Te)BH ? thf] ( 1 ), [(CpV)2(BH3S)2] ( 2 ), [(CpNb)2B4H10S] ( 3 ), [(CpNb)2B4H11S(tBu)2C6H2OH] ( 4 ), and [(CpNb)2B4H11TePh] ( 5 ). In cluster 1 , the V2BTe atoms define a tetrahedral framework in which the boron atom is linked to a THF molecule. Compound 2 can be described as a dimetallathiaborane that is built from two edge‐fused V2BS tetrahedron clusters. Cluster 3 can be considered as an edge‐fused cluster in which a trigonal‐bipyramidal unit (Nb2B2S) has been fused with a tetrahedral core (Nb2B2) by means of a common Nb2 edge. In addition, thermolysis of an in‐situ‐generated intermediate that was produced from the reaction of [Cp2VCl2] and LiBH4 ? THF with excess BH3 ? THF yielded oxavanadaborane [(CpV)2B3H8(μ3‐OEt)] ( 6 ) and divanadaborane cluster [(CpV)2B5H11] ( 7 ). Cluster 7 exhibits a nido geometry with C2v symmetry and it is isostructural with [(Cp*M)2B5H9+n] (M=Cr, Mo, and W, n=0; M=Ta, n=2; Cp*=η5‐C5Me5). All of these new compounds have been characterized by 1H NMR, 11B NMR, and 13C NMR spectroscopy and elemental analysis and the structural types were established unequivocally by crystallographic analysis of compounds 1 – 4 , 6 , and 7 . 相似文献
87.
Structure, magnetic and transport properties of polycrystalline Bi0.6−xPrxCa0.4MnO3 (x=0.0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6) have been studied. Systematic substitution of Pr at Bi site induces an interesting interplay between the charge ordering and antiferromagnetism. The charge ordering temperature (TCO) decreases with increasing x. The antiferromagnetic (AFM) ordering temperature (TN) increases sharply at both the extremes but remains nearly constant from x=0.2 to 0.4. At temperatures lower than TN a transition to the glassy state is observed. The nature of this glass like state appears to be controlled by the Pr content, and at lower values of x this is akin to a spin glass, while at higher x it has a characteristic of cluster glass. The Pr doping also leads to enhancement in the magnetic moment. In the present work it has been proposed that the local lattice distortion induced due to size mismatch between the A-site cations and 6s2 character of Bi3+ lone pair electron is responsible for the observed magnetic and electrical properties. 相似文献
88.
Kand D Kalle AM Varma SJ Talukdar P 《Chemical communications (Cambridge, England)》2012,48(21):2722-2724
A new chromenoquinoline-based fluorescent off-on thiol probe 2 is reported. In aqueous buffer solutions at physiological pH, the probe exhibited 223-fold enhancement in fluorescence intensity by a Michael addition of cysteine to the maleimide appended to a chromenoquinoline. Cell permeability and live cell imaging of thiols are also demonstrated. 相似文献
89.
One-pot synthesis of ruthenium hydroxide nanoparticles on magnetic silica is described which involves the in situ generation of magnetic silica (Fe(3)O(4)@SiO(2)) and ruthenium hydroxide immobilization; the hydration of nitriles occurs in high yield and excellent selectivity using this catalyst which proceeds exclusively in aqueous medium under neutral conditions. 相似文献
90.
Ashok K. Varma Ashwini Nangia Gautam R. Desiraju Venkatachalam S. Giri Parasuraman Jaisankar 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(1):97-99
3-Acetyl-1,6,7,12b-tetrahydroindolo[2,3-a]quinolizin-2(12H)-one, C17H16N2O2, consists of two symmetry-independent molecules and each forms a layered structure stabilized by N—H⃛O and C—H⃛O hydrogen bonds. In 3-acetyl-6,7-dihydroindolo[2,3-a]quinolizin-4(12H)-one monohydrate, C17H14N2O2·H2O, the structure is stabilized by O—H⃛O, N—H⃛O and C—H⃛O hydrogen bonds, with the ordered water molecule playing a crucial role in the self-assembly. Contribution from the weak interactions to the strong hydrogen-bonded network is a common feature in both structures. 相似文献