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81.
A new direct procedure for the determination of inorganic arsenic species was developed by electrochemical hydride generation atomic absorption spectrometry (EcHG-AAS) with selective electrochemical reduction. The determination of inorganic arsenic species is based on the fact that As(Ⅲ) shows significantly higher absorbance at low electrolytic currents than As(Ⅴ) in 0.3 mol·L^-1 H2SO4. The electrolytic current used for the determination of As(Ⅲ) without considerable interferences of As(Ⅴ) was 0.4 A, whereas the current for the determination of As(Ⅲ) and As(Ⅴ) was 1.2 A. For equal concentrations of As(Ⅲ) and As(Ⅴ) in a sample, the interferences of As(Ⅴ) during the As(Ⅲ) determination were smaller than 5%. The absorbance for As(Ⅴ) could be calculated by subtracting that for As(Ⅲ) measured at 0.4 A from the total absorbance for As(Ⅲ) and As(Ⅴ) measured at 1.2 A, and then the concentration of As(Ⅴ) can be obtained by its calibration curve at 1.2 A. The methodology developed provided the detection limits of 0.3 and 0.6 ng·mL^-1 for As(Ⅲ) and As(Ⅴ), respectively. The relative standard deviations were of 3.5% for 20 ng·mL^-1 As(Ⅲ) and 3.2% for 20 ng·mL^-1 As(Ⅴ). The method was successfully applied to determination of soluble inorganic arsenic species in Chinese medicine. 相似文献
82.
83.
The potential energy surfaces for CH(3)CONH(2) dissociation into CH(3) + CONH(2), CH(3)CO + NH(2), CH(3)CN + H(2)O, and CH(3)NH(2) + CO in the ground and lowest triplet states have been mapped with DFT, MP2, and CASSCF methods with the cc-pVDZ and cc-pVTZ basis sets, while the S(1) potential energy surfaces for these reactions were determined by the CASSCF/cc-pVDZ optimizations followed by CASSCF/MRSDCI single-point calculations. The reaction pathways leading to different photoproducts are characterized on the basis of the computed potential energy surfaces and surface crossing points. A comparison of the reactivity among HCONH(2), CH(3)CONH(2), and CH(3)CONHCH(3) has been made, which provides some new insights into the mechanism of the ultraviolet photodissociation of small amides. 相似文献
84.
IntroductionMononuclear ,dinuclearandpolymerictypesofcrys talstructuresforlanthanidecomplexeswithbenzoicacidanditsderivativeshavebeenobtainedbecauseofthevari ationofbridgingformsforcarboxylategroupandcoordina tionabilityofdiammineligands ,suchas 1,10 phena… 相似文献
85.
Speciation of inorganic arsenic by electrochemical hydride generation atomic absorption spectrometry 总被引:11,自引:0,他引:11
A simple procedure was developed for the speciation of inorganic arsenic by electrochemical hydride generation atomic absorption spectrometry (EcHG–AAS), without pre-reduction of As(V). Glassy carbon was selected as cathode material in the flow cell. An optimum catholyte concentration for simultaneous generation of arsine from As(III) and As(V) was 0.06 mol l−1 H2SO4. Under the optimized conditions, adequate sensitivity and difference in ratio of slopes of the calibration curves for As(III) and As(V) can be achieved at the electrolytic currents of 0.6 and 1 A. The speciation of inorganic arsenic can be performed by controlling the electrolytic currents, and the concentration of As(III) and As(V) in the sample can be calculated according to the equations of absorbance additivity obtained at two selected electrolytic currents. The calibration curves were linear up to 50 ng ml−1 for both As(III) and As(V) at 0.6 and 1 A. The detection limits of the method were 0.2 and 0.5 ng ml−1 for As(III) and As(V) at 0.6 A, respectively. The relative standard deviations were of 2.1% for 20 ng ml−1 As(III) and 2.5% for 20 ng ml−1 As(V). The method was validated by the analysis of human hair certified reference material and successfully applied to speciation of soluble inorganic arsenic in Chinese medicine. 相似文献
86.
合成了一种新的钌(II)配合物[Ru(bpy)2(Hfip)](ClO4)2, 其中bpy代表2,2′-联吡啶, Hfip代表2-(9H-芴-2-基)-1H-咪唑-[4,5-f]-[1,10]-邻菲啰啉. 通过紫外可见光谱、荧光光谱、稳态荧光淬灭、与溴化乙锭的竞争实验、粘度测量和DNA热变性研究了该配合物与小牛胸腺DNA的键合性质. 结果表明, 该配合物能嵌入键合DNA, 键合常数Kb=8.6×105 L·mol-1 (50 mmol·L-1 NaCl). 相似文献
87.
用ab initio方法, 在MP2/6-31G**水平下讨论了α-乙酰氧基-亚硝基吡咯烷(α-Acetoxy-NPYR)在各种条件下的解离反应机理, 并对形成终致癌物B, C, D的代谢机理进行研究. 发现在OH-和H2O作用下的解离都遵循羟基进攻羰基机理, OH-作用下是一个经四面体中间体阴离子的无位垒过程, H2O作用下有相对高的活化能(165.36 kJ/mol). H3O+作用下是先形成阳离子产物的SN1过程, 并没有发现遵循两种综合的解离情形. 同时, 羟基化产物异构化为终致癌物B, C, D是一个相对容易进行的过程. 相似文献
88.
研究发现, [Ru(phen)2dppz]2+表现出非常强的自聚合倾向, 并显著影响DNA的键合性质, 有关方面的研究应引起科研工作者的足够重视. 相似文献
89.
Synthesis of 99mTc(CO)3-NOET via [99mTc(OH2)3(CO)3]+ precursor and comparative biological studies with 99mTcN-noet 总被引:1,自引:0,他引:1
Summary The organometallic precursor fac-[99mTc(CO)3(H2O)3]+ was reacted with N-ethoxy, N-ethyl dithiocarbamate (NOET) in phosphate buffered saline (pH 7.4) at room temperature for 30
minutes to produce the 99mTc(CO)3-NOET complex. The radiochemical purity (RCP) of the product was over 90% as measured by thin layer chromatography (TLC).
No decomposition of the complex at room temperature (RT) was observed over a period of 6 hours. Its partition coefficient
indicated that it was a lipophilic complex. The biodistribution comparison in mice of the 99mTc(CO)3-NOET complex and the 99mTcN-NOET complex showed that the former had a lower heart and brain uptake as compared to that of the latter, suggesting the
incorporation of the [99mTc(CO)3]+ core into the NOET ligand does not improve the biological features as a myocardial imaging agent. 相似文献
90.
High-dimensional architectures from the self-assembly of lanthanide ions with benzenedicarboxylates and 1,10-phenanthroline 总被引:1,自引:0,他引:1
Six new coordination polymers, [Eu(1,2-BDC)(1,2-HBDC)(phen)(H(2)O)](n) (1), [Eu(2)(1,3-BDC)(3)(phen)(2)(H(2)O)(2)](n).4nH(2)O (2), [Eu(1,4-BDC)(3/2)(phen)(H(2)O)](n) (3), [Yb(2)(1,2-BDC)(3)(phen)(H(2)O)(2)](n).3.5nH(2)O (4), [Yb(2)(1,3-BDC)(3)(phen)(1/2)](n) (5), and [Yb(2)(1,4-BDC)(3)(phen)(2)(H(2)O)](n) (6), were synthesized by hydrothermal reactions of lanthanide chlorides with three isomers of benzenedicarboxylic acid (H(2)BDC) and 1,10-phenanthroline (phen), and characterized by single-crystal X-ray diffraction. 1 has a 2-D herringbone architecture with a Z-shaped cavity. 2 and 5 have different 3-D networks, but both are formed by 1,3-BDC anions bridging metal centers (Eu or Yb) via carboxylate groups. 3 and 6 possess similar layer structures which are further constructed to form 3-D networks by hydrogen bonds and/or pi-pi aromatic interactions. 4 comprises 1-D chains that are further interlinked via hydrogen bonds, resulting in a 3-D network. In the three europium complexes, all the europium ions are eight-coordinated, while the coordination numbers of the ytterbium ions in other three-coordination polymers range from six to eight. Crystal data: for 1, monoclinic, space group P2(1)/c, with a = 12.565(6) A, b = 16.005(8) A, c = 12.891(6) A, beta = 102.173(8) degrees, and Z = 4; for 2, monoclinic, space group P2(1)/c, with a = 20.979(4) A, b = 11.5989(19) A, c = 20.810(3) A, beta = 110.391(3) degrees, and Z = 4; for 3, triclinic, space group P1, with a = 10.331(5) A, b = 10.887(5) A, c = 11.404(5) A, alpha = 107.660(7) degrees, beta = 91.787(7) degrees, gamma = 112.946(6) degrees, and Z = 2; for 4, triclinic, space group P1, with a = 11.517(5) A, b = 13.339(5) A, c = 13.595(6) A, alpha = 87.888(7) degrees, beta = 67.759(6) degrees, gamma = 68.070(6) degrees, and Z = 2; for 5, orthorhombic, space group C222(1), with a = 8.174(2) A, b = 24.497(7) A, c = 29.161(8) A, and Z = 8; for 6, triclinic, space group P1, with a = 10.349(3) A, b = 11.052(3) A, c = 19.431(6) A, alpha = 105.464(4) degrees, beta = 91.300(5) degrees, gamma = 93.655(5) degrees, and Z = 2. The magnetic properties of 1 and 4 were investigated. The photophysical properties of 1 were also studied. 相似文献