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991.
采用高温固相法分别合成了不同Ce浓度掺杂的和固定Ce浓度为0.06不同Gd浓度掺杂的Y3Al5O12(YAG)系列荧光粉,通过测量其激发、发射光谱、漫反射光谱、荧光寿命和变温发射光谱,研究了掺杂元素的浓度对荧光粉发光性能的影响以及荧光粉发光的温度猝灭性质。研究结果表明:荧光粉发光强度随着Ce3+掺杂浓度和Gd3+掺杂浓度的提高均呈下降趋势。分析发现,荧光粉发光强度下降并非主要由浓度猝灭所引起,而是由于高浓度掺杂下发生YAG基质与Ce3+对激发光的竞争吸收,导致Ce3+对激发光的吸收量减少,从而影响发光强度。温度实验表明,随着温度的升高,荧光粉发光强度下降。Ce含量的改变对YAG:Ce荧光粉的热猝灭性质影响较小,Gd的掺杂使荧光粉的发射波长向长波方向移动,同时热猝灭现象严重。 相似文献
992.
993.
辣根过氧化物酶在亲水性离子液体中的活性与稳定性研究 总被引:1,自引:2,他引:1
基于辣根过氧化物酶对过氧化氢氧化愈创木酚这个显色反应的催化作用,研究了辣根过氧化物酶在七种亲水性离子液体[C2mim][BF4]、[C4mim][BF4]、[C6mim][BF4]、[C4mim]HSO4、[C4mim]Cl、[C4mim]NO3、[C4mim][CF3CO2]中的活性与稳定性变化.结果表明辣根过氧化物酶在不同离子液体中均有不同程度的失活,辣根过氧化物酶活性随离子液体极性增强而降低.辣根过氧化物酶在含[C4mim]Cl离子液体的介质中,随着温度升高,[C4mim]Cl对辣根过氧化物酶的失活过程起加速作用,离子液体浓度越高,酶的热稳定性越差.紫外-可见光谱研究表明,在含[Cnmim][BF4]、[C4mim]HSO4、[C4mim]Cl、[C4mim]NO3的介质中,辣根过氧化物酶血红素中心最大吸收峰没有发生变化,但吸收值增强,证明离子液体使酶的血红素基团暴露于介质中而增强了吸收;而在含[C4mim][CF3CO2]的介质中,辣根过氧化物酶血红素基团最大吸收峰区发生蓝移,证明有部分血红素基团被离子液体破坏而脱落. 相似文献
994.
超声波对制备Co-Fe/硅藻土选择加氢催化剂的影响 总被引:1,自引:0,他引:1
分别在有无超声条件下,采用分步浸渍法制备了负载型Co-Fe/硅藻土催化剂,以肉桂醛选择加氢为肉桂醇为探针反应,在固定床微分反应器上考察了催化剂的活性.采用热分析、红外、XRD及正电子寿命谱等技术分析了催化剂的催化性能及超声波对活性的影响.结果表明,经超声处理的催化剂对肉桂醛加氧为肉桂醇转化率、选择性和收率明显提高.超声处理没有改变催化剂载体的结构,但使主、助催化剂更好地分散在载体上,使催化剂表面的两类缺陷尺寸变小,同时增加第二类缺陷数量,有更好的催化活性. 相似文献
995.
Stanislav Šabata Jiří Hetflejš Renata Rychtáriková Gabriela Kuncová Kamil Lang Pavel Kubát 《Chemical Papers》2009,63(4):438-444
Three tetracationic porphyrins differing in the position of charged nitrogen atoms on the peripheral substituents — 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrin (TMPyP4), 5,10,15,20-tetrakis(N-methylpyridinium-2-yl)porphyrin (TMPyP2), 5,10,15,20-tetrakis(4-trimethylammoniophenyl) porphyrin (TMAPP), and hydrophobic 5,10,15,20-tetraphenylporphyrin (TPP), were immobilized by adsorption
and encapsulation in poly(hydroxymethylsiloxane) (PHOMS). The so prepared porphyrin-PHOMS composites were characterized by
porosimetry, scanning electron microscopy, fluorescence and diffuse reflectance UV-VIS spectroscopy. It was found that porphyrins
are immobilized in the PHOMS matrix in the free base monomer form Their irradiation produced singlet oxygen O2(1Δg) with the lifetime of 10–30 μs. 相似文献
996.
Qingxiang Wang Hongxu Guo Shunxing Li Feng Gao Danfeng Fang 《Journal of solution chemistry》2009,38(8):1085-1095
A polypyridyl nickel complex of [Ni(phen)(H2O)4]SO4?2H2O (phen = 1,10-phenanthroline) was synthesized and characterized by X-ray diffraction and IR spectroscopy. The results indicated that the central nickel ion is in a distorted octahedral geometry coordinated by two nitrogen atoms from 1,10-phenanthroline and four water molecules. The crystal data for this complex are: a=8.8797(18) Å, b=18.468(4) Å, c=22.081(4) Å, α=90°, β=90°, γ=90°, R 1=0.0533, and wR 2=0.2095. Electrochemical experiments showed that the complex could be reoxidized at a gold electrode under the precondition of electrolysis stripping. According to the results of cyclic voltammetry and coulometry, an electrochemical reaction mechanism was proposed. The DNA binding properties of the complex were further investigated by electronic absorption spectrophotometry and electrochemistry. The binding constant and the binding mode between the two species were estimated based on the spectroscopic and electrochemical results. 相似文献
997.
The structure of the new cycloartane glycoside cyclomacroside D, which was isolated from Astragalus macropus Bunge (Leguminosae) and is 24R-cycloartan-1α,3β,7β,24,25-pentaol 3-O-α-L-rhamnopyranoside–24-O-β-D-xylopyranoside, was proved.
Presented at the 7th International Symposium on the Chemistry of Natural Compounds (SCNC, Tashkent, Uzbekistan, October 16–18,
2007).
Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 48–50, January–February, 2009. 相似文献
998.
The reaction of Zn(acac)2 with btaH (1,2,3-benzotriazole) in dmf yielded the pentanuclear complex [Zn5(bta)6(acac)4(dmf)]·dmf (1·dmf). In the presence of pyrazine, the pentanuclear [Zn5(bta)6(acac)4(dmf)]·3.7dmf (2·3.7dmf) and enneanuclear [Zn9(bta)12(acac)6]·6dmf (3·6dmf) complexes were formed, whereas in the presence of 4,4′-bpy the 1D coordination polymer [Zn(acac)2(4,4′-bpy)]n (4) was isolated. The molecular structures of 1·dmf and 2·3.7dmf reveal that the [Zn5] clusters consist of four ZnII ions which span the corners of a tetrahedron and the fifth resides at its centre. The molecular structure of 3·6dmf reveals that the [Zn9] clusters consist of two corner sharing tetrahedra and the structure can be described as the addition of two [Zn5] clusters of 1·dmf and/or 2·3.7dmf followed by the simultaneous abstraction of [Zn(acac)2] and dmf molecules; this alternative was accomplished by recrystallization of 1·dmf from dmf which yielded 3·6dmf. Each of the μ3-κN:κN′:κN′′ benzotriazolate ligands in 1·dmf, 2·3.7dmf and 3·6dmf spans an edge of the tetrahedron. The molecular structure of 4 reveals mononuclear [Zn(acac)2] units bridged via 4,4′-bpy molecules to 1D coordination polymer. Characteristic IR bands of the four complexes are discussed in terms of the coordination modes of the ligands and known structures. 相似文献
999.
Four new Hofmann–3-phenylpropylamine (3PPA) type complexes with chemical formulae M(3PPA)2Ni(CN)4 (M = Ni, Co, Cd, and Pd) have been prepared and their vibrational spectra are reported in the region of 4000–60 cm−1. The vibrational bands arising from 3PPA ligand molecule, the polymeric sheet and metal–ligand bands of the compounds are assigned. The thermal behaviour of these complexes is also provided using the DTA and TGA along with the magnetic susceptibility data. The results indicate that the monodentate 3PPA ligand molecule bonds to the metal atom of |M–Ni(CN)4|∞ polymeric layers and hence the compounds are similar in structure to Hofmann-type complexes. 相似文献
1000.
A method that use kernel independent component analysis (KICA) and support vector regression (SVR) was proposed for estimation of source ultraviolet (UV) spectra profiles and simultaneous determination of polycomponents in mixtures. In KICA-SVR procedure, the UV source spectra profiles were estimated using KICA, then the mixing matrix of the components were calculated using the estimated sources, and the calibration model was build using SVR based on the calculated mixing matrix. A simulated UV dataset of three-component mixtures was used to test the ability of KICA for estimating source spectra profiles from spectra data of mixtures. It was found that KICA has the potential power to estimate pure UV spectra profiles, and correlation coefficient of estimated sources correspond to the real adopted ones are better compared with that by FastICA and Infomax ICA. An UV dataset of polycomponent vitamin B was processed using the proposed KICA-SVR method. The results show that the estimated source spectra profiles are correlative with the real UV spectra of the components and chemically interpretable, and accurate results were obtained. 相似文献