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61.
Taisei Ueda Tsuneyasu Adachi Shin-Ichi Nagai Jinsaku Sakakibara Mitsuo Murata 《Journal of heterocyclic chemistry》1988,25(3):791-794
[1,2,4]Triazino[3,2-f]purines 3a-e and [1,2,4]triazepino[3,2-f]purine 5 were synthesized by the reaction of 7,8-diamino-1,3-dimethylxanthine 1 with diketones such as glyoxal, diacetyl, dibenzoyl, pyruvic aldehyde dimethyl acetal, phenylglyoxal or acetylacetone in acetic acid in the presence of boric acid or polyphosphoric acid. 相似文献
62.
A new type of chiral receptor (R,R)- or (S,S)-1b with C(2) symmetry was synthesized. An induced-fit type of binding behavior of 1b for diamines was revealed by CD spectroscopy. NMR studies demonstrated that 1b can function as a highly sensitive chiral shift reagent for the determination of the enantiomeric purity of chiral diamines, aziridine, and isoxazoline at the microgram level. [structure: see text] 相似文献
63.
A stereoselectivity in an intramolecular cycloaddition of the olefinic -quinodimethanes 13 and 23 generated from the thermolysis of optically active 4β-[2-(4-methoxybenzocyclobutenyl)ethyl] -5α-methoxymethyl-3-phenyl-thio-methylenefuran-2-ones 12 and 22, respectively, is studied and a stereoselective synthesis of (+)--4,5-( 4-methoxybenzo) -1β,7aβ-(2α-methoxymethyl-5-oxofuro)hydrindane 1 is also described. 相似文献
64.
Two series of emission bands were observed for the CS2/Ar(1 : 100–500) system at 15 K with excitation at 257.3 nm. They are assigned to B3Σ?u → χ3Σ?g and B″3Πu → X3Σ?g of S2, which was formed by photodissociation of CS2, CS2 + hv → CS + S, followed by recombination of two S atoms. The B″3Πu state has been found 524 cm-1 lower in energy than B3Σ?u 相似文献
65.
Kyung‐Youl Baek Masami Kamigaito Mitsuo Sawamoto 《Journal of polymer science. Part A, Polymer chemistry》2002,40(12):1937-1944
A series of functionalized 2‐bromoisobutyrates and 2‐chloro‐2‐phenylacetates led to α‐end‐functionalized poly(methyl methacrylate)s in Ru(II)‐catalyzed living radical polymerization; the terminal functions included amine, hydroxyl, and amide. These initiators were effective in the presence of additives such as Al(Oi‐Pr)3 and n‐Bu3N. The chlorophenylacetate initiators especially coupled with the amine additive gave polymers with well‐controlled molecular weights (Mw/Mn = 1.2–1.3) and high end functionality (Fn ~ 1.0). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1937–1944, 2002 相似文献
66.
Isamu Onishi Kyung‐Youl Baek Yuzo Kotani Masami Kamigaito Mitsuo Sawamoto 《Journal of polymer science. Part A, Polymer chemistry》2002,40(12):2033-2043
A half‐metallocene iron iodide complex [Fe(Cp)I(CO)2] induced living radical polymerization of methyl acrylate (MA) in conjunction with an iodide initiator [(CH3)2C(CO2Et)I, 1 ] and Al(Oi‐Pr)3 to give polymers of controlled molecular weights and narrow molecular weight distributions (MWDs) (Mw/Mn < 1.2). With the use of chloride and bromide initiators, the MWDs were broader, whereas the molecular weights were similarly controlled. Other acrylates such as n‐butyl acrylate (nBA) and tert‐butyl acrylate (tBA) can be polymerized with 1 /Fe(Cp)I(CO)2 in the presence of Ti(Oi‐Pr)4 and Al(Oi‐Pr)3, respectively, to give living polymers. The 1 /Fe(Cp)I(CO)2 initiating system is applicable for the synthesis of block and random copolymers of acrylates (MA, nBA, and tBA) and styrene of controlled molecular weights and narrow MWDs (Mw/Mn = 1.2–1.3). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2033–2043, 2002 相似文献
67.
The excitation wavelength dependences of the intensities of the Raman lines of pyrazine have been measured. The intensity enhancement of the non-totally symmetric Raman line at 925 cm?1 provided firm evidence of the vibronic coupling between the lowest 1B3u(n,π*) and second lowest 1B2u(π,π*) states. The excitation wavelength dependences of other non-totally symmetric Raman lines suggest also the various vibronic coupling schemes. 相似文献
68.
Shinya Hamasaki Chie Sawauchi Masami Kamigaito Mitsuo Sawamoto 《Journal of polymer science. Part A, Polymer chemistry》2002,40(4):617-623
A fast living radical polymerization of methyl methacrylate (MMA) proceeded with the (MMA)2? Cl/Ru(Ind)Cl(PPh3)2 initiating system in the presence of n‐Bu2NH as an additive [where (MMA)2? Cl is dimethyl 2‐chloro‐2,4,4‐trimethyl glutarate]. The polymerization reached 94% conversion in 5 h to give polymers with controlled number‐average molecular weights (Mn's) in direct proportion to the monomer conversion and narrow molecular weight distributions [MWDs; weight‐average molecular weight/number‐average molecular weight (Mw/Mn) ≤ 1.2]. A poly(methyl methacrylate) with a high molecular weight (Mn ~ 105) and narrow MWD (Mw/Mn ≤ 1.2) was obtained with the system within 10 h. A similarly fast but slightly slower living radical polymerization was possible with n‐Bu3N, whereas n‐BuNH2 resulted in a very fast (93% conversion in 2.5 h) and uncontrolled polymerization. These added amines increased the catalytic activity through some interaction such as coordination to the ruthenium center. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 617–623, 2002; DOI 10.1002/pola.10148 相似文献
69.
A tritriacontanucleotide which has the sequence of the 5half molecule of E.coli glycine tRNA2, was synthesized by the phosphotriester method involving p-anisidate protection for the 3phosphate ends. Di- and trinucleotide units were prepared from 5dimethoxytrityl-2O-tetrahydrofuranyl-3?-O-(o-chlorophenyl)phosphoryl derivatives of uridine, N-benzoylcytidine, N-benzolyadenosine and N-iso-butyrylguanosine by condensation with 35unprotected nucleosides followed by phosphorylation to give 3phosphodiester blocks. The 3terminal dimers and trimers were synthesized by using 3(o- chlorophenyl)phosphoro-p-anisidates instead of 3?,5?-unprotected nucleosides. The 3?-phosphodiesters of oligonucleotides with a chain length of larger than 5 were obtained by removal of the 3?-phosphoro-p-anisidate with isoamyl nitrite. The 5dimethoxytrityl group was removed by treatment with zinc bromide under anhydrous conditions. Fragments were designed to use common dimer blocks and to reduce the step for 5deblocking of larger fragments. Finally a 3phosphodiester block with a chain length of 20 was condensed with a 5OH component (tridecanucleotide). The fully protected 33 mer was deblocked and purified by chromatography. The structural integrity of the product was confirmed by mobility shift analysis and complete digestion with RNase T2. 相似文献
70.
Kazuaki Miyashita Masami Kamigaito Mitsuo Sawamoto Toshinobu Higashimura 《Journal of polymer science. Part A, Polymer chemistry》1994,32(13):2531-2542
The end-functionalization of living polymers with bases (methanol, benzylamine, diethyl sodiomalonate, and sodium methoxide) and organosilicon compounds [X ? Si(CH3)3;X ? : CH2?C(CH3)COO? , CH3COO? , CH2?CHCH2? , C6H5? ] was investigated in the living cationic polymerization of styrene initiated with the 1-phenylethyl chloride/SnCl4/nBu4NCl system in CH2Cl2 at ?15°C. The four bases and C6H5SiMe3, independent of their structures, were apparently incapable of reacting with the living end and invariably led to polystyrenes with the ω-end chlorine [~ ~ ~ CH2CH(Ph)Cl] originated from the initiating system. The number-average end-functionality (F?n) of the chloride, determined by 1H-NMR, was close to unity (F?n > 0.9). The presence of chlorine in the polymer was also confirmed by elemental analysis. In contrast, the quenching by the trimethylsilyl compounds with X = methacryloxy, acetoxy, and allyl gave ω-end-functionalized polystyrenes with the corresponding terminal groups (X) for which the F?n values were close to unity (F?n > 0.9). The effects of the structure of silyl compounds on end-capping are also discussed. © 1994 John Wiley & Sons, Inc. 相似文献