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71.
72.
Ignacio Alfonso Covadonga Astorga Vicente Gotor 《Journal of inclusion phenomena and macrocyclic chemistry》2005,53(1-2):131-137
Electrospray ionization mass espectrometry (ESI-MS) has been used for the study of a cyclam derivative noncovalent interactions.
At acidic pH, diprotonated macrocycle bound to different anionic species were observed. The selectivity shown by competitive
experiments is rationalized with the help of semiempirical theoretical calculations. At basic pH, the base peak corresponded
to the macrocycle-alkaline metal complexes, and again competition experiments showed different binding strength. Finally,
experiments carried out in the presence of transition metal salts allowed the detection of the complexes present in the mixture
and revealed their different kinetic behavior. 相似文献
73.
对基于(C—H)+…X-氢键类型的阴离子识别以及识别过程所引起的光化学传感和电化学传感的研究进展进行了评述. 相似文献
74.
The possible structures and isomerizations of H2C=C(OH)Li are studied theoretically by the gradient analytical method at RHF/6-31+G level. According to these results, reactions
of H2C=C(OH)Li with CH3
+ and CH
3
-
are investigated thoroughly. When H2C=C(OH)Li reacts with CH
3
+
, HzC=C(OH)Li firstly changes from structure1 to structure4, and then combines with CH3
+. In this reaction, the configuration of central carbon is retained. When H2C=C(OH)Li reacts with CH
3
-
, structure1 firstly breaks its C-O bond to give contact ion-pair. Then through transition state16 which is similar to structure2, the attack of CH
3
-
from the opposite side of-OH replaces-OH group and inverts the configuration of carbenoid carbon atom. All the results show that the ambident reactivity of carbenoid
has close relationship with the stability of special structures.
Project supported by the National Natural Science Foundation of China (Grant No. 29773025). 相似文献
75.
Ayhan S. Demir Ömer Reis Ilker Esiringü Barbaros Reis Sehriban Baris 《Tetrahedron》2007,63(1):160-165
Acylphosphonates, which are easily available from carboxylic acids, are potent acyl anion precursors and undergo cyanide ion promoted phosphonate-phosphate rearrangement to provide the corresponding acyl anion equivalents as reactive intermediates. The protonation of these acyl anion equivalents furnished cyanohydrin O-phosphates in good yields. For the high yield formation of cyanohydrin O-phosphates from arylphosphonates THF should be used and from alkylphosphonates DME was used. 相似文献
76.
氟阴离子在有机合成中的应用:Ⅱ.无水氟化钾催化乙酐与苯甲醛的Perkin反应 总被引:4,自引:0,他引:4
用无水醋酸盐催化苯甲醛与乙酐的Perkin反应,一般反应时间较长,产率最高为55—60%.用三乙胺、吡啶和无水碳酸钾等作催化剂,产率也无明显提高.近年来氟阴离子在有机合成中的应用迅速发展,我们曾用无水氟化钾催化成功地实施了丙二酸二乙酯与苯甲醛的Knoevenagel缩合,并研讨了该反应的微环境效应.本工作首次用无水氟 相似文献
77.
The electronic absorption spectrum for the dibiphenylene-ethene radical anion (
), generated electrochemically in dimethylsulfoxide solutions, is reported. Based on calculations by the LCAO-MO method in theHückel approximation and on the analysis of the band positions it is suggested that in the
molecule two planar fluorenylidene fragments are twisted (60°) about the central C=C bond.
Das Elektronenabsorptionsspektrum des Dibiphenylen-Radikalanions (Kurze Mitteilung)
Zusammenfassung Das Dibiphenylenethen-Radikalanion ( ) wurde elektrochemisch hergestellt und das Elektronenabsorptionsspektrum aufgenommen. Auf Grund von LCAO-MO Berechnungen in derHückel-Annäherung und der Analyse der Bandenlagen wird nahegelegt, daß im -Molekül zwei planare Fluorenyliden-Fragmente ca. 60° um die zentrale C=C-Bindung verdrillt angeordnet sind.相似文献
78.
The reaction of spirobisilafluorene (1) with lithium in dimethoxyethane produces lithium 1-methyl-spirobisilafluorenide (2), a stable pentacoordinate silicon compound with five carbon ligands, and lithium 2-methoxyethoxide, which was identified by trapping with Ph3SiCl to give Ph3Si-OCH2CH2OCH3 (4). The X-ray crystal structure of 2 shows that the geometry at silicon is an idealized trigonal bipyramid, slightly distorted toward a square pyramid. Methanolysis of 2 cleaves a Si-aryl bond producing a methyl biphenylsilafluorene, 3. Crystal structures are reported for 3 and 4. 相似文献
79.
T. L. Luke H. Mohan V. M. Manoj P. Manoj J. P. Mittal C. T. Aravindakumar 《Research on Chemical Intermediates》2003,29(4):379-391
Reactions of sulphate radical anion (SO·4
-) with 4,6-dihydroxy-2-methyl pyrimidine (DHMP), 2,4-dimethyl-6-hydroxy pyrimidine (DMHP), 6-methyl uracil (MU) and 5,6-dimethyl uracil (DMU) have been studied by pulse radiolysis at pH 3 and at pH 10. The transient intermediate spectra were compared with those from the reaction of hydroxyl radical (·OH). It is proposed that SO·4
- produces radical cations of these pyrimidines in the initial stage. These radical cations are short-lived except in the case of DMHP where a relatively longer lived radical cation is proposed to be formed. When there is a hydrogen atom attached to the N(1) or N(3) position, a deprotonation from these sites is highly favored. When there is no hydrogen attached to these sites, deprotonation from a substituted methyl group is favored. At acidic pH, deprotonation from nitrogen is observed for DHMP, MU and DMU. At basic pH, the radical cation reacts with OH- leading to the formation of OH adducts. 相似文献
80.
聚合物硼氢阴离子还原剂的制备及其对酯的还原研究 总被引:3,自引:0,他引:3
氯型季我安盐型强碱性阴离子交换树脂711^#与硼氢化钾反应制得聚合物硼氢阴离子还原剂,树脂容量3.2mmol BH4/g。用于不同酯化合物的还原,操作简便,树脂可再生重复使用。 相似文献