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941.
Huang Hong-Liang Tang Bing Yi Qiao-Yan Wan Dan Yang Lin-Lin Liu Yun-Jun 《Transition Metal Chemistry》2019,44(1):11-24
Transition Metal Chemistry - Five new ruthenium(II) polypyridyl complexes [Ru(N–N)2(BTCP)](ClO4)2 (BTCP?=?2-(bicyclo[2.2.1]hept-5-en-2-yl)-1H-imidazo[4,5-f][1,10]phenanthroline;... 相似文献
942.
A theoretical study has been made on six isomers of H2SO2 using coupled-cluster singles and doubles with noniterative triple excitations (CCSD(T)). The isomers studied are sulfoxylic acid (S(OH)2; C2 and Cs conformers), sulfinic acid (HS(=O)OH; 2 C1 conformers), dihydrogen sulfone (H2SO2; C2v), sulfhydryl hydroperoxide (HSOOH; C1), thiadioxirane (Cs), and dihydrogen persulfoxide (H2SOO; Cs). Molecular geometries, harmonic vibrational frequencies, and infrared intensities of all species were obtained using the CCSD(T) method and the 6-311++G(2d,2p) basis set. All aforementioned species were found to be local minima, with the exception of thiadioxirane, which has one imaginary frequency. A prior possible infrared observation of sulfinic acid was reassessed on the basis of the present data. In agreement with previous MP2 results, the present CCSD(T) data provide support for at most 4 of the 8 observed frequencies. The CCSD(T) frequencies and intensities should be of assistance in future identification of H2SO2 isomers by vibrational spectroscopy. Relative energies were calculated using the CCSD(T) method and several larger basis sets. As found previously, the lowest energy species is C2 S(OH)2, followed by Cs S(OH)2, HS(=O)OH, H2SO2, HSOOH, thiadioxirane, and H2SOO. Expanding the basis set significantly reduces the relative energies of HS(=O)OH and H2SO2. The CCSD(T) method was used with extended basis sets (up to aug-cc-pV(Q+d)Z) and basis set extrapolation in two reaction schemes to calculate the DeltaH degrees t (25 degrees C) of C2 S(OH)2. The two reaction schemes gave -285.8 and -282.7 kJ mol-1, which are quite close to a prior theoretical estimate (-290 kJ mol-1). 相似文献
943.
944.
Huang J Jiang Y Marthala VR Hunger M 《Journal of the American Chemical Society》2008,130(38):12642-12644
The direct experimental evidence shows that ethylbenzene disproportionation is a transition state shape selective reaction on zeolites: a bimolecular reaction mechanism via diphenylethane-mediated pathway on large-pore zeolites X and Y (ca. 0.74 nm) and a monomolecular reaction mechanism on medium-pore zeolites ZSM-5 (ca. 0.56 nm) via the ethoxy-mediated intermolecular ethyl group transfer. The lifetime of bulky diphenylethane species was prolonged by a fine-tune of FAU-zeolites, which makes this transition state detectable by 13C MAS NMR spectroscopy. Due to tunable catalytic properties and pore shapes, zeolites are promising catalysts toward emulating the efficiency and selectivity in desired reactions. 相似文献
945.
946.
947.
人工神经网络及模拟退火算法应用于原子吸收光谱法同时测定钙、磷 总被引:2,自引:0,他引:2
试验发现:原子吸收光谱法(AAS)在442.7 Nm波长处测定钙时受到大于0.10 mg·L-1磷共存的干扰,使钙的测定结果偏低,而且此负偏差降低的幅度随磷浓度的增加而增大.试验还发现:当共存磷的量在0.1~6.0 mg·L-1之间时,钙测量值的负偏差幅度与磷浓度之间存在明显的相关性.应用反向传播人工神经网络(BP-ANN)及模拟退火两种计算法对上述非线性干扰效应进行了研究,并提出了在单一波长检测的条件下,钙、磷两元素的原子吸收光谱法同时测定,此法应用于循环水中钙、磷的同时测定.两元素的检测范围依次为0.08~10.0 mg·L-1及0.10~6.0 mg·L-1,测得其回收率分别为100.5%和98.0%. 相似文献
948.
Huang Y Khartulyari S Morales ME Stanislawska-Sachadyn A Von Feldt JM Whitehead AS Blair IA 《Rapid communications in mass spectrometry : RCM》2008,22(16):2403-2412
Red blood cell (RBC) folate levels are established at the time of erythropoiesis and therefore provide a surrogate biomarker for the average folate status of an individual over the preceding four months. Folates are present as folylpolyglutamates, highly polar molecules that cannot be secreted from the RBCs, and must be converted into their monoglutamate forms prior to analysis. This was accomplished using an individual's plasma pteroylpolyglutamate hydrolase by lysing the RBCs in whole blood at pH 5 in the presence of ascorbic acid. Quantitative conversion of formylated tetrahydrofolate derivatives into the stable 5,10-methenyltetrahydrofolate (5,10-MTHF) form was conducted at pH 1.5 in the presence of [(13)C(5)]-5-formyltetrahydrofolate. The resulting [(13)C(5)]-5,10-MTHF was then used as an internal standard for the formylated forms of tetrahydrofolate that had been converted into 5,10-MTHF as well any 5,10-MTHF that had been present in the original sample. A stable isotope dilution liquid chromatography-multiple reaction monitoring/mass spectrometry method was validated and then used for the accurate and precise quantification of RBC folic acid, 5-methyltetrahydrofolate (5-MTHF), tetrahydrofolate (THF), and 5,10-MTHF. The method was sensitive and robust and was used to assess the relationship between different methylenetetrahydrofolate reductase (MTHFR) 677C>T genotypes and RBC folate phenotypes. Four distinct RBC folate phenotypes could be identified. These were classified according to the relative amounts of individual RBC folates as type I (5-MTHF >95%; THF <5%; 5,10-MTHF <5%), type II (5-MTHF <95%; THF 5% to 20%; 5,10-MTHF <5%), type III (5-MTHF >55%; THF >20%; 5,10-MTHF >5%), and type IV (5-MTHF <55%; THF >20%; 5,10-MTHF >5%). 相似文献
949.
Electrochemical studies of the interaction of clarithromycin with bovine serum albumin 总被引:1,自引:0,他引:1
The interaction of clarithromycin (CAM) with bovine serum albumin (BSA) was investigated in pH 4.5 - 8.0 phosphate buffer solutions in which three irreversible reduction waves P(1), P(2) and P(3) of CAM appeared on linear-sweep voltammetry on a static dropping mercury working electrode. In the acidic media, with the addition of BSA into the CAM solution, a new electrochemically active complex was formed and there was interaction between the carbonyl group C=O in the C-9 position of CAM and BSA. It was found that electrostatic and hydrophobic forces played an important role in the binding reaction. However, new electrochemically non-active complexes were formed at physiological pH condition. The study showed that the formation constant and formation ratio of the interaction between CAM and BSA were 1.51 x 10(12) and 3:1 for P(2) wave, and 4.53 x 10(5) and 1:1 for P(3) wave, respectively. The ion strength enhanced the hydrophobic interaction between CAM and BSA. 相似文献
950.