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941.
942.
943.
944.
Allenyl methyl ether ( 1 ) and (diphenylmethylene)cyclopropane ( 5 ) were ozonized with an ozone/oxygen mixture. Formation of the observed products cannot be satisfactorily rationalized via the familiar modified Criegee mechanism. However, a single‐electron transfer (SET) mechanism provides a simple rationale. 相似文献
945.
Christian Slugovc Kurt Mereiter Swiatoslaw Trofimenko Ernesto Carmona 《Helvetica chimica acta》2001,84(10):2868-2883
A series of pyrazole‐substituted [hydrotris(1H‐pyrazolato‐κN1)borato(1−)]iridium complexes of the general composition [Ir(Tpx)(olefin)2] (Tpx=TpPh and TpTh) and their capability to activate C−H bonds is presented. As a test reaction, the double C−H activation of cyclic‐ether substrates leading to the corresponding Fischer carbene complexes was chosen. Under the reaction conditions employed, the parent compound [Ir(TpPh)(ethene)2] was not isolable; instead, (OC‐6‐25)‐[Ir(TpPhκCPh,κ3N,N′,N″)(ethyl)(η2‐ethene)] ( 1 ) was formed diastereoselectively. Upon further heating, 1 could be converted exclusively to (OC‐6‐24)‐[Ir(TpPhκ2CPh,CPh,κ3N,N′,N″)(η2‐ethene)] ( 2 ). Complex 1 , but not 2 , reacted with THF to give (OC‐6‐35)‐[Ir(TpPhκ3N,N′,N″)H(dihydrofuran‐2(3H)‐ylidene)] ( 3 ), a cyclic Fischer carbene formed by double C−H activation of THF. Accordingly, complexes of the general formula [Ir(Tpx)(butadiene)] (see 4 – 6 ; butadiene=buta‐1,3‐diene, 2‐methylbuta‐1,3‐diene (isoprene), 2,3‐dimethylbuta‐1,3‐diene) reacted with THF to yield 3 or the related derivative 9 . The reaction rate was strongly dependent on the steric demand of the butadiene ligand and the nature of the substituent at the 3‐position of the pyrazole rings. 相似文献
946.
GuyEmmanuel Raoelison Christian Terreaux EmersonFerreira Queiroz Ferenc Zsila Miklos Simonyi Sandor Antus Adolphe Randriantsoa Kurt Hostettmann 《Helvetica chimica acta》2001,84(11):3470-3476
The stem bark CH2Cl2 extract of Ravensara crassifolia showed antifungal activity against the phytopathogenic fungus Cladosporium cucumerinum in a bioautographic TLC assay. Activity‐guided fractionation afforded two new α‐pyrones : (6S)‐5,6‐dihydro‐6‐[(2R)‐2‐hydroxy‐6‐phenylhexyl]‐2H‐pyran‐2‐one ( 1 ) and (6R)‐6‐[(4R,6R)‐4,6‐dihydroxy‐10‐phenyldec‐1‐enyl]‐5,6‐dihydro‐2H‐pyran‐2‐one ( 2 ). Their structures and absolute configurations were established by NMR spectroscopy, chemical methods, and CD spectroscopy. The antifungal activity against C. cucumerinum was determined for both compounds. 相似文献
947.
Metal Complexes of Functionalized Sulfur‐containing Ligands. XVII Synthesis of S ‐Oxides of 1,2,4‐Trithiolane, 1,2,4,5‐Tetrathiane as well as 1,2,3,5,6‐Pentathiepane, and their Reactions with (Ph3P)2Pt(η2‐C2H4). X‐Ray Structure Analysis of 3,3,5,5‐Tetraphenyl‐1,2,4‐trithiolane 1‐oxide 3,3,5,5‐Tetraphenyl‐1,2,4‐trithiolan ( 1 ) was oxidized using m‐chloroperbenzoic acid to give, selectively, the 3,3,5,5‐tetraphenyl‐1,2,4‐trithiolane 1‐oxide ( 2 ). 2 was characterized structurally. The reaction of octamethyl tetrathiadispiro[3.2.3.2]dodecane‐2,9‐dione ( 3 ) with trifluoroperacetic acid at –50 °C yielded the corresponding 5‐oxide 4 . Oxidation of octamethyl pentathiadispiro[3.3.3.2]tridecane‐2,9‐dione ( 5 ) with m‐chloroperbenzoic acid at 0 °C gave the 12‐oxide 6 . Treatment of 2 with two equivalents of (Ph3P)2Pt(η2‐C2H4) ( 7 ) afforded a mixture (1 : 1) of the complexes (Ph3P)2PtSCPh2S ( 8 ) and (Ph3P)2Pt(η2‐Ph2C=S=O) ( 9 ), respectively. 相似文献
948.
[Fc2B2(Br)(μ‐NPEt3)2]+Br– – a Ferrocenyl‐substituted Phosphoraneiminato Complex of Boron [Fc2B2(Br)(μ‐NPEt3)2]+Br– has been prepared from ferrocenylboron dibromide, [Fe(η5‐C5H5)(η5‐C5H4BBr2)], and the silylated phosphoraneimine Me3SiNPEt3 in dichloromethane solution to give orange‐red single crystals which were characterized by IR, NMR and 57Fe Mössbauer spectra, as well as by a crystal structure determination. [Fc2B2(Br)(μ‐NPEt3)2]+Br– · 3 CH2Cl2 ( 1 · 3 CH2Cl2): Space group P21/n, Z = 4, lattice dimensions at –50 °C: a = 1370.6(3), b = 2320.9(5), c = 1454.4(2), β = 95.38(1)°, R1 = 0.061. In the cation of 1 the ferrocenyl‐substituted boron atoms are connected by the nitrogen atoms of the [NPEt3]– groups to form a planar B2N2 four‐membered ring. One of the boron atoms having planar, the other tetrahedral coordination. 相似文献
949.
The compound [K([2.2.2]crypt)]Cs7[Sn9]2(en)3 ( 1 ) was synthesized from an alloy of formal composition KCs2Sn9 by dissolving in ethylenediamine (en) followed by the addition of [2.2.2]crypt and toluene. 1 crystallizes in the orthorhombic space group Pcca with a = 45.38(2), b = 9.092(4), c = 18.459(8) Å, and Z = 4. The structure consists of Cs7[Sn9]2 layers which contain [Sn9]4– anions and Cs+ cations. The layers are separated by [K([2.2.2]crypt)]+ units. In the intermetallic slab (Cs7[Sn9]2)– compares the arrangement of pairs of symmetry‐related [Sn9]4– anions with the dimer ([Ge9]–[Ge9])6– in [K([2.2.2]crypt)]2Cs4([Ge9]–[Ge9]), in which the clusters are linked by a cluster‐exo bond. The shortest distance between atoms of such two clusters in 1 is 4.762 Å, e. g. there are no exo Sn‐Sn bonds. The [Sn9]4– anion has almost perfect C4v‐symmetry. 相似文献
950.
Nagatoshi Nishiwaki Kristian Rahbek Knudsen Kurt V. Gothelf Karl Anker Jrgensen 《Angewandte Chemie (International ed. in English)》2001,40(16):2935-2935
The cover picture shows two new catalytic asymmetric reactions in front of an enantiomeric pair of lurs—one of the national symbols of Denmark. Chiral bisoxazoline copper complexes catalyze the reactions. The reaction on the left is the direct enantioselective Mannich reaction of carbonyl compounds with imines to give highly functionalized 4‐oxo‐glutamic esters, while the reaction on the right is the enantioselective nitro‐Mannich reaction of nitro alkanes with imines to give optically active β‐nitro‐α‐amino esters. Why the lur in relation to the present chemistry? Lurs exist as pairs of enantiomers and they probably belong to some of the first man‐made pair of enantiomers, as they are from the Bronze Age (1000–500 BC). The lurs are the oldest musical instruments that can still be played, and are used as enantiomers. Side by side stood two lur‐players, symmetric in every detail, the soft curves of the instruments swaying upwards and outwards at each side. The sonorous notes emphasized the solemn nature of the rituals. It is conceivable that the sound of the lur also accompanied the crackle of the funeral pyre when one of the tribe was cremated and laid to rest in the burial mound of his forefathers. The lurs are made of bronze (copper) and were discovered in lakes; less than 50 are known. The most famous pair of lurs was found in Brudevælte and is the pair shown on the cover. Further information about lurs can be obtained from kaj@chem.au.dk. The picture of the lurs and the accompanying music (click here to listen to the music: www.angewandte.com) are used with permission from The National Museum. For more details about the two new catalytic asymmetric reactions, see Jørgensen et al. on p. 2992 ff. and p. 2995 ff. 相似文献