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71.
Hong Tao Gao Dong Mei Dai Tong Hua Li 《中国化学快报》2007,18(4):495-498
Non-negative matrix factorization(NMF)is a technique for dimensionality reduction by placing non-negativity constraints onthe matrix.Based on the PARAFAC model,NMF was extended for three-dimension data decomposition.The three-dimension non-negative matrix factorization(NMF3)algorithm,which was concise and easy to implement,was given in this paper.The NMF3algorithm implementation was based on elements but not on vectors.It could decompose a data array directly without unfolding,which was not similar to that the traditional algorithms do.It has been applied to the simulated data array decomposition andobtained reasonable results.It showed that NMF3 could be introduced for curve resolution in chemometrics. 相似文献
72.
Biosynthesis of polyhydroxyalkanoates (PHAs) consisting of 3-hydroxyalkanoates (3HAs) of 4 to 10 carbon atoms was examined
in metabolically engineered Escherichia coli strains. When the fadA and/or fadB mutant E. coli strains harboring the plasmid containing the Pseudomonas sp. 61-3 phaC2 gene and the Ralstonia eutropha phaAB genes were cultured in Luria-Bertani (LB) medium supplemented with 2 g/L of sodium decanoate, all the recombinant E. coli strains synthesized PHAs consisting of C4, C6, C8, and C10 monomer units. The monomer composition of PHA was dependent on
the E. coli strain used. When the fadA mutant E. coli was employed, PHA containing up to 63 mol% of 3-hydroyhexanoate was produced. In fadB and fadAB mutant E. coli strains, 3-hydroxybutyrate (3HB) was efficiently incorporated into PHA up to 86 mol%. Cultivation of recombinant fadA and/or fadB mutant E. coli strains in LB medium containing 10 g/L of sodium gluconate and 2 g/L of sodium decanoate resulted in the production of PHA
copolymer containing a very high fraction of 3HB up to 95 mol%. Since the material properties of PHA copolymer consisting
of a large fraction of 3HB and a small fraction of medium-chain-length 3HA are similar to those of low-density polyethylene,
recombinant E. coli strains constructed in this study should be useful for the production of PHAs suitable for various commercial applications. 相似文献
73.
A simple method is reported for predicting the retention index (RI) of a chemical compound from the number of carbon and carbon equivalent atoms in the molecule, the RI increment for atom addition and the group retention factors (GRFs) for substituents and functional groups. Atoms other than carbon such as oxygen, nitrogen, sulfur, chlorine, bromine and iodine are assigned carbon atom equivalency of approximately 1, 1, 2, 2, 3 and 4, respectively and are counted for their contribution towards RI prediction. The GRFs of substituents and functional groups are derived from the RIs of reference compounds and series of homologues. Ring structures, ring fusion, ring connection, iso- and neo-carbons, chain branching and unsaturation are also assigned GRFs. The predicted RIs of a number of alicyclic, aliphatic and aromatic hydrocarbons, primary, secondary and tertiary alcohols, phenols, aliphatic amines, aromatic amines, heterocyclics, carboxylic acids, acid esters, aldehydes, ketones, and halogenated compounds, are found to be within +/- 3% of the observed values. The structure-retention index relationship thus developed is extremely useful in the tentative identification of radioactive side products formed in tritium labeling by radiation-induced methods. 相似文献
74.
75.
MingZhuLIU ShengYiZHANG YuHuaSHEN MingLiangZHANG 《中国化学快报》2004,15(10):1249-1252
Selenium nanoparticles were prepared by a reverse microemulsion system. Sodium selenosulfate was used as selenium source. The results showed that hydrochloric acid concentration and reaction temperature had great influence on the morphology of products. The crystalline selenium nanowires and amorphous selenium nanorods were obtained in given condition. 相似文献
76.
PU大分子单体水溶液性质 总被引:2,自引:0,他引:2
双亲聚合物一般由亲水和亲油 2种链段构成 ,有嵌段型[1,2 ] 和接枝型[3 ] 2种 ,其中通过大分子单体法合成双亲接枝聚合物备受关注[4] 。如以亲水性大分子单体和亲油性小分子单体共聚 ,大分子单体构成共聚物主链上支链 ,具有较大活动性 ,亲水效能高。采用对氯甲基苯乙烯[5] 或甲基丙烯酰氯[6] 与聚氧化乙烯大分子的一端相反应 ,可得到亲水性大分子单体 ,但其分子量及结构变化有限。本文采用常规条件 ,合成了嵌段式水溶性聚氨酯大分子单体 ,其分子量较大 ,共聚接枝的支链较长。利用该大分子单体具有非离子高分子表面活性剂的性质 ,采用无皂乳… 相似文献
77.
相转移催化合成对甲氧基肉桂酸-2-乙基己酯的研究 总被引:5,自引:1,他引:5
对甲氧基肉桂酸 2 乙基己酯是一种有效的UVB防晒剂[1 ,2 ] ,一般采用Claisen Schmidt缩合反应制得[3] ,但由于催化剂KOH处于水相 ,对反应物不能充分起到催化作用导致产率较低[4] 。我们利用乙二醇 (PEG)为相转移催化剂合成立体专一的反式对甲氧基肉桂酸 2 乙基己酯 ,产率提高到 72 .5 %。合成路线如下 :1 实验部分1 .1 仪器与试剂BIO RAPFT45 0红外光谱仪 ,用液膜法测试 ;Brurer AM 30 0超导核磁共振仪 (溶剂DC Cl3) ;MAT/44S ,GC MS型色质联用谱仪 ;试剂均为分析纯 ,上海化学试剂… 相似文献
78.
Xuan-Ming Zhang Long-Long Guo Ning-Hui Yang Hua Zhang 《Natural product research》2019,33(17):2549-2553
This study investigated the flavonoid constituents of a traditional Chinese medical plant Ziziphora clinopodioides Lam. by using ultra-performance liquid chromatography coupled with quadruple time-of-flight mass spectrometry and screened the active components in regulating autophagy.Normal rat kidney (NRK) cells transfected with green fluorescent protein- microtubule-associated protein 1 light Chain 3(GFP-LC3) were treated with Z. clinopodioides flavonoids and its chemical compositions. After 4 h of treatment, the auto-phagy spot aggregation in NRK cells was photographed and observed by laser scanning confocal microscopy. The following 10 flavonoid components of Z. clinopodioides were identified: baicalein(1), quercetin(2), hyperoside(3), quercetin3-O-β-d-glucopyranoside(4), apigenin(5), kaempferol(6), chrysin(7), diosimin(8), linarin(9) and rutin(10). Among these flavonoids, chrysin, apigenin and quercetin were identified as the active principles in activating autophagy. This research may provide a reference for further developing and utilizing Z. clinopodioides. 相似文献
79.
Thermolysis of benzannulated enyne-isocyanates 13 and enyne-isocyanates 36 and 37 promoted the cycloaromatization reactions to generate in situ O,4-didehydro-2-hydroxyquinolines and O,4-didehydro-2-hydroxypyridines, respectively, as reactive intermediates. These cycloaromatized intermediates could be captured either as biradicals and/or as zwitterions depending on the nature of the substituent at the alkynyl terminus. The intermediate derived from cycloaromatization of 13a bearing a phenyl substituent could be regarded as biradical 14, which then abstracts hydrogen atoms from gamma-terpinene leading to 2(1H)-quinolinone 15. Alternatively, the same intermediate could also be regarded as zwitterion 14', which then undergoes an initial hydride abstraction from gamma-terpinene followed by protonation to produce 15. The presence of a 2-phenylethyl substituent in 13b and 37a or a 2-methylphenyl substituent in 37b also allowed the resulting intermediates to be captured intramolecularly either as biradicals or as zwitterions, producing 2(1H)-quinolinone 19, 2(1H)-pyridone 39, and benzopyranopyridine 43, respectively. On the other hand, with a 2-methoxyphenyl, a 2-(dimethylamino)phenyl, or a 3-methoxypropyl substituent, the chemical behavior of the cycloaromatized adduct could be best accounted for in terms of a zwitterionic intermediate leading to benzofuro[3,2-c]quinolin-6(5H)-one (20), 5,11-dihydro-11-methyl-6H-indolo[3,2-c]quinolin-6-one (25), benzofuro[3,2-c]pyridin-1(2H)-one 44, 2,5-dihydro-2,5-dimethyl-1H-pyrido[4,3-b]indol-1-one 46, and related compounds. Interestingly, thermolysis of 37f bearing a 2-(methoxymethyl)phenyl substituent at the alkynyl terminus produced the unexpected benzopyranopyridine 56 as the major product in a process involving the cleavage of the bond between the methoxyl oxygen and the adjacent methylene carbon. The efficiency and selectivity of the cycloaromatization reaction could also be enhanced by the introduction of 1.1 to 10 equiv of dimethylphenylsilyl chloride to the reaction mixture to capture the resulting zwitterion. 相似文献
80.
[reaction: see text] Bi(NO(3))(3).5H(2)O was used as an efficient nitrating reagent in the nitration of phenolic compounds to give nitrated phenols in good to high yields. The nitration reaction proceeded smoothly by grinding 1 equiv of phenol, 2-methylphenol, 4-methylphenol, or 4-chlorophenol and Bi(NO(3))(3).5H(2)O, and the nitration of other phenolic compounds could be performed in acetone at ambient temperature (22-30 degrees C). 相似文献