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991.
Caskey SR Stewart MH Kivela JE Sootsman JR Johnson MJ Kampf JW 《Journal of the American Chemical Society》2005,127(48):16750-16751
Desulfurization of the thiocarbonyl ligand in square pyramidal [Ru(CS)Cl2(PCy3)2] (1-S) via sulfur atom abstraction using [Mo(H)(eta2-Me2CNAr)(N[i-Pr]Ar)2] forms [Ru(C)Cl2(PCy3)2] (1) cleanly over several hours in benzene; isolated yield is 55%. Complex 1 is also formed in 87% isolated yield upon reaction of [Ru(CHR)(PCy3)2Cl2] (R = p-C6H4Me, 2; Ph, 3) with vinyl acetate in dichloromethane. Complex 1-S is re-formed quantitatively from 1 upon treatment with elemental sulfur in CH2Cl2, but is prepared most conveniently by treatment of crude [Ru(CS)Cl2(PPh3)2(OH2)] with excess PCy3 in toluene. Nearly quantitative conversion of 1 to [Ru(CO)Cl2(PCy3)2] (1-O) occurs upon addition of dimethyldioxirane solution in acetone to 1 dissolved in CH2Cl2 at ca. -90 degrees C. 相似文献
992.
Johan K. Terlouw Wigger Heerma John L. Holmes Peter C. Burgers 《Journal of mass spectrometry : JMS》1980,15(11):582-586
The [C4H6O]+˙ ion of structure [CH2?CHCH?CHOH]+˙ (a) is generated by loss of C4H8 from ionized 6,6-dimethyl-2-cyclohexen-1-ol. The heat of formation ΔHf of [CH2?CHCH?CHOH]+˙ was estimated to be 736 kJ mol?1. The isomeric ion [CH2?C(OH)CH?CH2]+˙ (b) was shown to have ΔHf, ? 761 kJ mol?1, 54 kJ mol?1 less than that of its keto analogue [CH3COCH?CH2]+˙. Ion [CH2?C(OH)CH?CH2]+˙ may be generated by loss of C2H4 from ionized hex-1-en-3-one or by loss of C4H8 from ionized 4,4-dimethyl-2-cyclohexen-1-ol. The [C4H6O]+˙ ion generated by loss of C2H4 from ionized 2-cyclohexen-1-ol was shown to consist of a mixture of the above enol ions by comparing the metastable ion and collisional activation mass spectra of [CH2?CHCH?CHOH]+˙ and [CH2?C(OH)CH?CH2]+˙ ions with that of the above daughter ion. It is further concluded that prior to their major fragmentations by loss of CH3˙ and CO, [CH2?CHCH?CHOH]+˙ and [CH2?C(OH)CH?CH2]+˙ do not rearrange to their keto counterparts. The metastable ion and collisional activation characteristics of the isomeric allenic [C4H6O]+˙ ion [CH2?C?CHCH2OH]+˙ are also reported. 相似文献
993.
A direct plasma injection HPLC method has been developed for the determination of selected phenothiazines (promethazine, promazine, chlorpromazine) using a Hisep column. The method is easy to perform and requires 20 microL of a filtered plasma sample. The chromatographic run time is less than 11 min using a mobile phase of 15:85 v/v acetonitrile-0.18 m ammonium acetate pH 5.0 and UV detection at 254 nm. The method is linear in the concentration range 0.1-25 microg mL(-1) (r > 0.99, n = 6) for each analyte with RSD less than 6%. Interday and intraday variability were found to be < or =14%. The limits of detection and quantitation were 0.1 (S/N > 3) and 0.25 microg mL(-1) (S/N > 10), respectively, for each of the three phenothiazines. We can also apply this method to separate three other phenothiazines (ethopromazine, trifluoroperazine, prochlorperazine), although it lacks the selectivity to determine the concentration of all six drugs concurrently. The separation is feasible using these drugs in certain combinations. 相似文献
994.
Lipopolysaccharides (LPS), otherwise termed 'endotoxins', are an integral part of the outer leaflet of the outer-membrane of Gram-negative bacteria. Lipopolysaccharides play a pivotal role in the pathogenesis of 'Septic Shock', a major cause of mortality in the critically ill patient, worldwide. The sequestration of circulatory endotoxin may be a viable therapeutic strategy for the prophylaxis and treatment of Gram-negative sepsis. We have earlier shown that the pharmacophore necessary for small molecules to bind LPS is simple, comprising of two protonatable cationic functions separated by about 15 A, permitting the simultaneous interaction with the negatively charged phosphates on lipid A, the toxically active center of endotoxin. In this report, we employ high-throughput screening methods, using a novel fluorescent probe displacement method. Searches in three-dimensional structure databases yielded about approximately 4000 commercially available small molecules, each possessing two cationic functions spaced approximately 15 A apart. Approximately 400 such compounds have been screened in an effort to validate the method by which high-affinity endotoxin binders can be identified. We show that the IC50 values that are obtained from the fluorescence-based primary screen are correlated both to the enthalpy of binding, as measured by isothermal titration calorimetry, as well as to biological potency in vitro assays. By performing rapid toxicity screens in tandem with the bioassays, lead compounds of interest can be easily identified for further systematic structural modifications and SAR studies. 相似文献
995.
Stewart W. Schneller Jiann-Kuan Luo Ramachandra S. Hosmane Rainer H. DÚrrfeld 《Journal of heterocyclic chemistry》1984,21(4):1153-1155
The synthesis of 1-methyl- ( 1a ) and 1-benzyl-6-amino-1H-pyrrolo[3,2-c]pyridin-4(5H)-one ( 1b ) from the appropriate N-alkylaminoacetaldehyde is described. These provide examples of a synthetic procedure that can be used to prepare 1-substituted 6-amino-1H-pyrrolo[3,2-c]pyridin-4(5H)-ones wherein the N-1 substituent is regiospecifically placed. 相似文献
996.
Peter C. Burgers Johan K. Terlouw John L. Holmes 《Journal of mass spectrometry : JMS》1982,17(8):369-372
The charge stripping mass spectra of [C2H5O]+ ions permit the clear identification of four distinct species: \documentclass{article}\pagestyle{empty}\begin{document}${\rm CH}_{\rm 3} - {\rm O - }\mathop {\rm C}\limits^{\rm + } {\rm H}_{\rm 2}$\end{document}, \documentclass{article}\pagestyle{empty}\begin{document}${\rm CH}_{\rm 3} - \mathop {\rm C}\limits^{\rm + } {\rm H - OH}$\end{document}, and \documentclass{article}\pagestyle{empty}\begin{document}${\rm CH}_{\rm 2} = {\rm CH - }\mathop {\rm O}\limits^{\rm + } {\rm H}_{\rm 2}$\end{document}. The latter, the vinyloxonium ion, has not been identified before. It is generated from ionized n-butanol and 1,3-propanediol. Its heat of formation is estimated to be 623±12 kJ mol?1. The charge stripping method is more sensitive to these ion structures than conventional collisional activation, which focuses attention on singly charged fragment ions. 相似文献
997.
Kenneth P. J. Williams Stewart F. Parker Patrick J. Hendra Andrew J. Turner 《Mikrochimica acta》1988,95(1-6):231-234
The use of a bench top FTIR spectrometer for near infrared Fourier transform Raman spectroscopy is demonstrated. The use of near infrared excitation results in fluorescence free Raman spectra allowing previously difficult samples to be measured. 相似文献
998.
Background
Hammerhead ribozymes are RNA-based molecules which bind and cleave other RNAs specifically. As such they have potential as laboratory reagents, diagnostics and therapeutics. Despite having been extensively studied for 15 years or so, their wide application is hampered by their instability in biological media, and by the poor translation of cleavage studies on short substrates to long RNA molecules. This work describes a systematic study aimed at addressing these two issues. 相似文献999.
Supercritical fluid chromatography (SFC) was investigated for the separation of non-steroidal anti-inflammatory agents (NSAIs). Three different stationary phases (SB-methyl-100, SB-biphenyl-30, and SB-cyanopropyl-50) were compared for the separation of the compounds. Baseline separation of a flufenamic acid, mefenamic acid, fenbufen and indomethacin mixture was achieved on the SB-biphenyl-30 column using a pressure gradient. A mixture containing flufenamic acid, mefenamic acid, acetylsalicylic acid, ketoprofen and fenbufen and another mixture containing ibuprofen, fenoprofen, naproxen, ketoprofen and tolmetin were well separated on the SB-cyanopropyl-50 column using pressure gradients. Typical analysis time for a mixture of NSAIs on the biphenyl or cyanopropyl column was approximately 20-25 min. Application of the method using the biphenyl column to the determination of NSAIs present in selected commercial dosage forms was demonstrated. 相似文献
1000.
The neutral counterparts of the C2H7O+ isomers CH3O+ (H)CH3, CH3CH2OH2+ and $ {\rm C}_2 \,{\rm H}_4 \,\, \cdot \cdot \cdot \mathop {\rm H}\limits^ + \, \cdot \cdot \cdot {\rm OH}_2 $ were studied by neutralization-reionization mass spectrometry. Protonated dimethyl ether and its —O(D)+ analogue were produced by protonation (deuteration) of dimethyl ether and also generated as a fragment ion from (labeled) ionized CH3OCH2CH(OH)CH3 by loss of CH3CO?. It was observed that the dissociation characteristics of the ions and the stability of their neutral counterpart depended on the internal energy of the protonated ether ions. Stable neutral CH3?(H)CH3 was only produced from energy-rich ions. The classical protonated ethanol ion CH3CH2OH2+ (a) was produced at threshold by the loss of CH3CO?. from ionized butane-2,3-diol. Mixtures of a with the non-classical ion $ {\rm C}_2 \,{\rm H}_4 \,\, \cdot \cdot \cdot \mathop {\rm H}\limits^ + \, \cdot \cdot \cdot {\rm OH}_2 $ (b) were produced by reaction of C2H5+ ions with H2O. As for the protonated ether, only high-energy a and/or b ions yielded stable hypervalent radicals. It is suggested that the stable C2H7?O radicals are Rydberg states. 相似文献