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891.
An. A. Kist A. G. Kist A. A. Kim A. N. Idrisova V. N. Sidorov Yu. Ya. Kit 《Journal of Radioanalytical and Nuclear Chemistry》1995,195(1):219-225
A general method for tritium labeling of organic compounds by the use of thermal activation of tritium is described. It allows obtaining uniformly tritium-labeled organic compounds with high specific activity (up to 50 Ci/mmol) which permits tracing the majority of the biodegradation products of compounds studied. More than 40 compounds were labeled using this simple, rapid and inexpensive method. Separation of the biodegradation products is performed by thin layer chromatography. Quantification is performed by direct measurement of the radioactivity by liquid scintillation counting after transfer of the layer from TLC plates into scintillation vials, or by densitometry of autoradiographs. The technique is useful for a wide range of organic compounds, including ones with unknown structure, and can be applied to various in vivo and in vitro studies. 相似文献
892.
Abstract—
The relative biological importance of cis-syn cyclobutane dimer and pyrimidine(6–4)pyr-imidone photoadduct ([6–4] photoadduct) appears to be dependent on the biological species, dipyrimidine sites and the local conformational variation induced at the damaged sites. The single-stranded deoxyn-ucleotide 10-mers containing the site-specific (6–4) adduct or cis-syn cyclobutane dimer of thymidylyl (3'-5')-thymidine were generated by direct photolysis of d(CGCATTACGC) with UVC (220–260 nm) irradiation or UVB (260–320 nm) photosensitization. Three-dimensional structures of the duplex cis-syn and (6–4) decamers of d(CGCATTACGC)d(GCGTAATGCG) were determined by NMR spectroscopy and the relaxation matrix refinement method. The NMR data and structural calculations establish that Watson-Crick base pairing is still intact at the cis-syn dimer site while the hydrogen bonding is absent at the 3'-side of the (6–4) lesion where the T → C transition mutation is predominantly targeted. Overall conformation of the duplex cis-syn decamer was B-DNA and produced a 9° bending in the DNA helix, but a distinctive base orientation of the (6–4) lesion provided a structural basis leading to 44° helical bending. The observed local structure and conformational rigidity at the (6–4) adduct of the thymidylyl(3'-5')-thymidine (T-T [6–4]) lesion site suggest the potential absence of hydrogen bonding at the 3' sides of the (6–4) lesion with a substituted nucleotide during replication under SOS conditions. Contrasting structural distortions induced by the T-T (6–4) adduct with respect to the T-T cis-syn cyclobutane pyrimidine photodimer may explain the large differences in mutation spectrum and repair activities between them. 相似文献
The relative biological importance of cis-syn cyclobutane dimer and pyrimidine(6–4)pyr-imidone photoadduct ([6–4] photoadduct) appears to be dependent on the biological species, dipyrimidine sites and the local conformational variation induced at the damaged sites. The single-stranded deoxyn-ucleotide 10-mers containing the site-specific (6–4) adduct or cis-syn cyclobutane dimer of thymidylyl (3'-5')-thymidine were generated by direct photolysis of d(CGCATTACGC) with UVC (220–260 nm) irradiation or UVB (260–320 nm) photosensitization. Three-dimensional structures of the duplex cis-syn and (6–4) decamers of d(CGCATTACGC)d(GCGTAATGCG) were determined by NMR spectroscopy and the relaxation matrix refinement method. The NMR data and structural calculations establish that Watson-Crick base pairing is still intact at the cis-syn dimer site while the hydrogen bonding is absent at the 3'-side of the (6–4) lesion where the T → C transition mutation is predominantly targeted. Overall conformation of the duplex cis-syn decamer was B-DNA and produced a 9° bending in the DNA helix, but a distinctive base orientation of the (6–4) lesion provided a structural basis leading to 44° helical bending. The observed local structure and conformational rigidity at the (6–4) adduct of the thymidylyl(3'-5')-thymidine (T-T [6–4]) lesion site suggest the potential absence of hydrogen bonding at the 3' sides of the (6–4) lesion with a substituted nucleotide during replication under SOS conditions. Contrasting structural distortions induced by the T-T (6–4) adduct with respect to the T-T cis-syn cyclobutane pyrimidine photodimer may explain the large differences in mutation spectrum and repair activities between them. 相似文献
893.
Youngwon Lee Charles P. Emerson Myoung Hee Kim 《Applied biochemistry and biotechnology》1995,55(3):231-240
TnINEO fusion gene was constructed by fusing 3.4-kbp of quailTnI genomic DNA sequences spanning the promoter to exon 5 and aneo gene in frame. A myoblast cell line was established after transfection of pTnINEO. Since this cell line was passaged several
times, a high frequency of neomycin (G418) sensitivity conversion was detected. Two drug-resistant variants were analyzed
through genomic Southern blot and S1 nuclease protection assay. One variant has a mutation(s) in the regulatory element that
activated the dormantTnI promoter-enhancer in myoblast, and the other has shown the genomic rearrangement. This result presented the possibility of
isolating factor(s) that activate the muscle-specificTnI promoter simply by screening drug-resistant cells having appropriate mutations. 相似文献
894.
Dong Won Kim Young Shin Jeon Young Kyu Jeong Moo Yul Suh Kih Soo Joe 《Journal of Radioanalytical and Nuclear Chemistry》1995,189(2):219-227
The chromatographic separation of lithium isotopes was investigated by chemical exchange with the recently synthesized polymer-bound dibenzo pyridino diamide azacrown (DBPDA) and reduced dibenzo pyridino diamide azacrown (RDBPDA). Column chromatography was employed for the determination of the effect of solvents and ligand conformation on the separation coefficients. The maximum separation coefficients, , for the DBPDA and RDBPDA at 20.0±0.02°C with acetonitrile as eluent, were found to be 0.034±0.002 and 0.035±0.002, respectively. The isotope separation coefficient and adsorption capability of the lithium ion on the DBPDA and RDBPDA were only slightly dependent on ligand structure, but strongly dependent on the solvent. DBPDA and RDBPDA appeared to have almost the same value for the isotope separation coefficient of lithium. 相似文献
895.
B. H. Kim Y. B. Lee M. A. Prelas T. K. Ghosh 《Journal of Radioanalytical and Nuclear Chemistry》2012,292(3):1075-1083
Two types of ammonium uranyl nitrate (NH4)2UO2(NO3)4·2H2O and NH4UO2(NO3)3, were thermally decomposed and reduced in a TG-DTA unit in nitrogen, air, and hydrogen atmospheres. Various intermediate
phases produced by the thermal decomposition and reduction process were investigated by an X-ray diffraction analysis and
a TG/DTA analysis. Both (NH4)2UO2(NO3)4·2H2O and NH4UO2(NO3)3 decomposed to amorphous UO3 regardless of the atmosphere used. The amorphous UO3 from (NH4)2UO2(NO3)4·2H2O was crystallized to γ-UO3 regardless of the atmosphere used without a change in weight. The amorphous UO3 obtained from decomposition of NH4UO2(NO3)3 was crystallized to α-UO3 under a nitrogen and air atmosphere, and to β-UO3 under a hydrogen atmosphere without a change in weight. Under each atmosphere, the reaction paths of (NH4)2UO2(NO3)4·2H2O and NH4UO2(NO3)3 were as follows: under a nitrogen atmosphere: (NH4)2UO2(NO3)4·2H2O → (NH4)2UO2(NO3)4·H2O → (NH4)2UO2(NO3)4 → NH4UO2(NO3)3 → A-UO3 → γ-UO3 → U3O8, NH4UO2(NO3)3 → A-UO3 → α-UO3 → U3O8; under an air atmosphere: (NH4)2UO2(NO3)4·2H2O → (NH4)2UO2(NO3)4·H2O → (NH4)2UO2(NO3)4 → NH4UO2(NO3)3 → A-UO3 → γ-UO3 → U3O8, NH4UO2(NO3)3 → A-UO3 → α-UO3 → U3O8; and under a hydrogen atmosphere: (NH4)2UO2(NO3)4·2H2O → (NH4)2UO2(NO3)4·H2O → (NH4)2UO2(NO3)4 → NH4UO2(NO3)3 → A-UO3 → γ-UO3 → α-U3O8 → UO2, NH4 UO2(NO3)3 → A-UO3 → β-UO3 → α-U3O8 → UO2. 相似文献
896.
Lee S Kim J In S Choi H Oh SM Jang CG Chung KH 《Analytical and bioanalytical chemistry》2012,403(5):1385-1394
Owing to the tight control of methamphetamine, it is presumed that phentermine, an amphetamine-type anorectic, has recently
been considered a supplement for methamphetamine abusers in Korea. In addition, the abuse of other anorectics obtained by
inappropriate means has become a social issue. Hair is a useful specimen to prove chronic drug use. Therefore, an analytical
method for the simultaneous detection of phentermine, phendimetrazine, amfepramone, fenfluramine, mazindol, methamphetamine,
and 3,4-methylenedioxymethamphetamine (MDMA), as well as their metabolites, which covers the major amphetamines and anorectic
agents in Korea, in hair was established and validated using liquid chromatography–tandem mass spectrometry (LC-MS/MS). The
drugs and their metabolites in hair were extracted using 1 % HCl in methanol and then filtered and analyzed by LC-MS/MS with
electrospray ionization in positive mode. The validation results for selectivity, linearity, matrix effect, recovery, process
efficiency, intra- and interassay precision and accuracy, and processed sample stability were satisfactory. The limits of
detection ranged from 0.025 to 1 ng/10 mg hair and the limits of quantification were 0.25 ng/10 mg hair for every analyte
except mazindol and phentermine, for which they were 10 ng/10 mg hair. The method was successfully applied for the segmental
determination of selected anorectics, methamphetamine, MDMA, and their metabolites in hair from 39 drug suspects. Among the
anorectics, phentermine and/or phendimetrazine were identified with or without methamphetamine in the hair samples. Closer
supervision of the inappropriate use of anorectics is necessary. Also, hair analysis is useful for monitoring the abuse potential
of unnoticed drugs. 相似文献
897.
Hanna GohMin Joung Kim Preeti SalujaNarinder Singh Doo Ok Jang 《Tetrahedron letters》2012,53(30):3900-3902
A dipodal receptor was synthesized by condensation of isophthalaldehyde and p-toluenesulfonylhydrazide. The receptor was found to be selective for Cu2+ recognition in CH3CN. The resultant Cu2+ receptor complex selectively recognized iodide through cation displacement assay in a CH3CN/H2O (8:2, v/v) solvent system. 相似文献
898.
Arvind H. JadhavHern Kim 《Tetrahedron letters》2012,53(39):5338-5342
Selective deprotection of alkyl TBDMS ether in the presence of phenolic TBDMS ether using dicationic ionic liquid [tetraEG(mim)2][OMs]2 as a homogeneous catalyst showed significant catalytic activity in methanol at ambient temperature to produce respective alcohol in excellent yield. The present environmentally benign catalytic system is found to be very convenient, fast, high yielding, and clean method for selective desilylation of alkyl silyl ethers even in the existence of other sensitive organic functional groups such as aldehyde, methoxy, and acetate were also achieved. 相似文献
899.
Jinseob Shin Kyomin Shin Hanna Lee Kyung-Do Suh Hyojung Kim Jin Woong Kim 《Colloid and polymer science》2012,290(6):553-559
This paper describes a useful means of noninvasively enhancing transdermal delivery efficiency. For this, chitosan nanocapsules with positive surface charges were fabricated by using the in situ precipitation method. These nanocapsules cannot only have an ability to encapsulate the drug molecule (this study used riboflavin 5′-monophosphate), but also electrotatically interact with the stratum corneum layer. To demonstrate this, fluorescence-labeled polymer nanoparticles with different particle sizes as well as surface charges were topically applied onto the skin and their distribution was directly imaged. This demonstration experiment allowed us to figure out that once the nanocapsules were provided with positive surface charges, they readily deposited into the stratum corneum layer due to the electrostatic interaction. Further quantitative characterization of the penetrating amount of riboflavin 5′-monophosphate by using the Frantz diffusion cell method showed that our chitosan nanocapsule system effectively improved transdermal delivery efficiency. 相似文献
900.
Soojin Lee Borim Kim Kyungmoon Park Youngsoon Um Jinwon Lee 《Applied biochemistry and biotechnology》2012,166(7):1801-1813
meso-2,3-Butanediol (meso-2,3-BDO) is essential for the synthesis of various economically valuable biosynthetic products; however, the production of
meso-2,3-BDO from expensive carbon sources is an obstacle for industrial applications. In this study, genes involved in the synthesis
of 2,3-BDO in Klebsiella pneumoniae were identified and used to genetically modify Escherichia coli for meso-2,3-BDO production. Two 2,3-BDO biosynthesis genes—budA, encoding acetolactate, and meso-budC, encoding meso-SADH—from K. pneumoniae were cloned into the pUC18 plasmid and introduced into E. coli. In 2 l batch culture, the SGSB03 E. coli strain yielded meso-2,3-BDO at 0.31 g/gglucose (with a maximum of 15.7 g/lculture after 48 h) and 0.21 g/gcrude glycerol (with a maximum of 6.9 g/lculture after 48 h). Batch cultures were grown under optimized conditions (aerobic, 6% carbon source, 37 °C, and initial pH 7). To
find the optimal culture conditions for meso-2,3-BDO production, we evaluated the enzyme activity of meso-SADH and the whole cell conversion yield (meso-2,3-BDO/acetoin) of the E. coli SGSB02, which contains pSB02. meso-SADH showed high enzyme activity at 30–37 °C and pH 7 (30.5–41.5 U/mg of protein), and the conversion yield of SGSB02 E. coli was highest at 37–42 °C and a pH of 7 (0.25–0.28 g
meso-2,3-BDO/gacetoin). 相似文献