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231.
Alfred Cerezo Peter H Clifton Sergio Lozano-Perez Peter Panayi Gang Sha George D W Smith 《Microscopy and microanalysis》2007,13(6):408-417
Over the last few years there have been significant developments in the field of three-dimensional atom probe (3DAP) analysis. This article reviews some of the technical compromises that have led to different instrument designs and the recent improvements in performance. An instrument has now been developed, based around a novel reflectron configuration combining both energy compensation and focusing elements, that yields a large field of view and very high mass resolution. The use of laser pulsing in the 3DAP, together with developments in specimen preparation methods using a focused ion-beam instrument, have led to a significant widening in the range of materials science problems that can be addressed with the 3DAP. Recent studies of semiconductor materials and devices are described. 相似文献
232.
PdH2、YH2分子的结构与势能函数 总被引:6,自引:0,他引:6
用密度泛函理论的B3LYP方法,对钯和钇原子采用SDD收缩价基函数,氢原子采用6-311++G**全电子基函数,对PdH2和YH2体系的结构进行优化计算,得到PdH2分子最稳态为C2v构型,电子组态为1A1,平衡核间距RPdH=0.1692 nm,键角∠HPdH=29.4°,离解能De=5.5212 eV,基态简正振动频率:ν1(b2)=1470.1 cm-1、ν2(a1)=1007.9 cm-1、ν3(a1)=2907.0 cm-1.YH2分子最稳态也为C2v构型,电子组态2A1,RYH=0.1962 nm,∠HYH=114.3°,De=5.6691 eV,基态简正振动频率:ν1(b2)=1457.9 cm-1、ν2(a1)=476.0 cm-1、ν3(a1)=1506.3 cm-1.由微观过程的可逆性原理分析了分子的可能离解极限.并用多体项展式理论方法分别导出基态PdH2和YH2分子的势能函数,其等值势能面图准确地再现了PdH2和YH2分子的结构特征和离解能,由此讨论了Pd + H2和Y + H2分子反应的势能面静态特征. 相似文献
233.
M. G. Fan Y. C. Liang Y. F. Ming J. X. Chen T. Ye Q. Y. Zhang B. A. Xu S. Jin 《Research on Chemical Intermediates》1998,24(9):961-971
Photophysical behavior of spiro[1,3,3-trimethylindolino-2,3′-naphtho[2,1-b]-1,4-oxazine] (SP1) and spiro[1,3,3,2′-tetramethylindolino-2,3′-naphtho[2,1-b]-1,4-oxazine] (SP2) were studied. The fluorescent species and their spectra of SP1 and SP2 in polar solvents (acetonitrile and methanol) and non-polar solvent (cyclohexane) were investigated. The fluorescence decay
in polar solvents was studied by picosecond time-correlated single photon counting. In most cases, fluorescence decay obeyed
triexponential decay kinetics. The major fluorescent species is an excited intermediate which has similar conformation as
its precursor (1
SP
*) formed after the bond cleavage between spirocarbon and oxygen in oxazine ring. The effects of molecular structure and solvent
polarity on fluorescence spectra and fluorescence decay lifetime were studied. 相似文献
234.
235.
Xiao Ying Xu Feng Cheng Jian Hua Shen Xiao Min Luo Li Li Chen Li Duo Yue Yi Du Fei Ye Shan Hao Jiang Da Yuan Zhu Hua Liang Jiang Kai Xian Chen 《International journal of quantum chemistry》2003,93(6):405-410
Docking simulation of 18 agonists with the ligand binding pocket (LBP) of PPARγ has been performed. The binding conformations and binding affinities of these agonists were obtained by use of the flexible docking protocol FlexX. Test compound calculations indicated that FlexX can reproduce the binding conformation of the crystal structure (root mean square deviation = 1.43 Å); moreover, the predicted binding affinities correlate well with the activities of these agonists. The interaction model and pharmacophore of PPARγ agonists were derived and the difference in biologic activities of these agonists can be well explained. The PPARγ agonists must have both polar head and the hydrophobic tail, which form hydrogen bonds and hydrophobic contacts with hydrophilic and hydrophobic regions of the LBP of PPARγ, respectively. In addition, a suitable linker is also necessary. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 93: 405–410, 2003 相似文献
236.
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238.
Two novel coordination polymers of Co(II) with dicyanamide (dca) were obtained by the addition of ancillary ligands of pyrazine dioxide (pzdo) and 2-methyl pyrazine dioxide (mpdo) into the Co-dca binary system, respectively. Co[N(CN)(2)](2)(pzdo) (1) crystallizes in the orthorhombic space group of Pnnm (No. 58) with a = 9.4699(5) A, b = 14.9984(3) A, c = 7.4313(7) A, and Z = 4, while Co[N(CN)(2)](2)(mpdo) (2) is in the monoclinic space group C2 (No. 5) with a = 16.5391(4) A, b = 9.6065(2) A, c = 7.5001(2) A, beta = 105.779(1) degrees, and Z = 4. Both complexes contain similar two-dimensional triangular Co-dca layers, which offer rare examples of mixed 1,5-mu- and mu(3)-dca bridging coordination polymers with long-range ferromagnetic ordering below ca. 2.5 K. 相似文献
239.
240.
建立了一种可同时对醛、酮糖进行精确定性和定量分析的方法。以肌醇作为内标,用80%乙醇超声提取,利用醋酸酐和HMDS+TMCS(1:3)进行差异衍生,在EI源下用SIM模式进行GC/MS分析。结果表明:11种标准单糖在1—4mg/L范围内线性良好;仪器检出限:醛糖在8.15—22.4μg/L之间;酮糖为2.32μg/L和3.47μg/L;高、中、低3个量的平均回收率在73.0%-95.7%,相对标准偏差在3.1%-10.0%。对枸杞游离单糖进行测定,各单糖含量分别在0.26—368.6mg/g。该方法弥补了以前单糖分析中的缺陷,对既含有醛糖又含有酮糖的样品可同时进行精确的定性定量分析。 相似文献