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991.
A carbon paste electrode chemically modified with multiwall nanotubes and ethynylferrocene (ETFc) was used as a selective and sensitive electrochemical sensor for the determination of minor amounts of N-acetylcysteine (N-AC) in the presence of a high concentration of tryptophan (Trp). Square wave voltammetry (SWV) of N-AC at the modified electrode exhibited linear dynamic range with a detection limit (3 s) of 0.08 μmol?L?1. The separations of anodic peak potentials of N-AC and Trp reached 400 mV using SWV. With good selectivity and sensitivity, the present method provides a simple method for selective detection of N-AC in real samples such as drug and urine. 相似文献
992.
This paper reports the selective and sensitive voltammetric determination of l-cysteine in the presence of folic acid using ethynylferrocene modified carbon nanotubes paste electrode in 0.1 M phosphate buffer solution (pH 7.0). Using square wave voltammetry, we could measure l-cysteine and folic acid in one mixture independently from each other by a potential difference of about 410 mV for the first time. Square wave voltammetric peak current of l-cysteine and folic acid increased linearly with their concentrations in the ranges of 0.2–250.0 and 1.0–500.0 μmol?L?1, respectively. The detection limits of 0.07 and 0.6 μmol?L?1 were achieved for l-cysteine and folic acid, respectively. The proposed voltammetric sensor was successfully applied to the determination of l-cysteine and folic acid in real samples. 相似文献
993.
Chernov SV Dobrovolsky YA Istomin SY Antipov EV Grins J Svensson G Tarakina NV Abakumov AM Van Tendeloo G Eriksson SG Rahman SM 《Inorganic chemistry》2012,51(2):1094-1103
Three different perovskite-related phases were isolated in the SrGa(1-x)Sc(x)O(2.5) system: Sr(2)GaScO(5), Sr(10)Ga(6)Sc(4)O(25), and SrGa(0.75)Sc(0.25)O(2.5). Sr(2)GaScO(5) (x = 0.5) crystallizes in a brownmillerite-type structure [space group (S.G.) Icmm, a = 5.91048(5) ?, b = 15.1594(1) ?, and c = 5.70926(4) ?] with complete ordering of Sc(3+) and Ga(3+) over octahedral and tetrahedral positions, respectively. The crystal structure of Sr(10)Ga(6)Sc(4)O(25) (x = 0.4) was determined by the Monte Carlo method and refined using a combination of X-ray, neutron, and electron diffraction data [S.G. I4(1)/a, a = 17.517(1) ?, c = 32.830(3) ?]. It represents a novel type of ordering of the B cations and oxygen vacancies in perovskites. The crystal structure of Sr(10)Ga(6)Sc(4)O(25) can be described as a stacking of eight perovskite layers along the c axis ...[-(Sc/Ga)O(1.6)-SrO(0.8)-(Sc/Ga)O(1.8)-SrO(0.8)-](2).... Similar to Sr(2)GaScO(5), this structure features a complete ordering of the Sc(3+) and Ga(3+) cations over octahedral and tetrahedral positions, respectively, within each layer. A specific feature of the crystal structure of Sr(10)Ga(6)Sc(4)O(25) is that one-third of the tetrahedra have one vertex not connected with other Sc/Ga cations. Further partial replacement of Sc(3+) by Ga(3+) leads to the formation of the cubic perovskite phase SrGa(0.75)Sc(0.25)O(2.5) (x = 0.25) with a = 3.9817(4) ?. This compound incorporates water molecules in the structure forming SrGa(0.75)Sc(0.25)O(2.5)·xH(2)O hydrate, which exhibits a proton conductivity of ~2.0 × 10(-6) S/cm at 673 K. 相似文献
994.
A novel, simple and facile layer by layer (LBL) approach is used for modification of glassy carbon (GC) electrode with multilayer of catalase and nanocomposite containing 1-(3-Aminopropyl)-3-methylimidazolium bromide (amine terminated ionic liquid (NH2-IL)) and titanium nitride nanoparticles (TiNnp). First a thin layer of NH2-IL is covalently attached to GC/TiNnp electrode using electro-oxidation method. Then, with alternative self assemble positively charged NH2-IL and negatively charged catalase a sensitive H2O2 biosensor is constructed, whose response is directly correlated to the number of bilayers. The surface coverage of active catalase per bilayer, heterogeneous electron transfer rate constant (ks) and Michaelis–Menten constant (KM) of immobilized catalase were 3.32 × 10−12 mol cm−2, 5.28 s−1 and 1.1 mM, respectively. The biosensor shows good stability, high reproducibility, long life-time, and fast amperometric response with the high sensitivity of 380 μA mM−1 cm−2 and low detection limit of 100 nM at concentration range up to 2.1 mM. 相似文献
995.
Omar M. Ali Wael A. El‐Sayed Heba A. El‐Sayed Adel A.‐H. Abdel‐Rahman 《Journal of heterocyclic chemistry》2012,49(5):1026-1032
New thiazole derivatives were synthesized. The N‐substituted acyclic nucleoside analogs and the substituted glucosides were also prepared. The synthesized compounds were tested for their antimicrobial activity against Candida albicans, Escherichia coli, Staphylococcus aureus, and Bacillus subtilis. The obtained results indicated that most of the tested compounds exhibited low to high moderate activities whereas few compounds were found to exhibit little or no activity against the tested microorganisms. 相似文献
996.
S.?WaheedEmail author S.?Rahman S.?M.?Husnain N.?Siddique 《Journal of Radioanalytical and Nuclear Chemistry》2012,292(3):937-945
Instrumental Neutron Activation Analysis (INAA) and Atomic Absorption Spectroscopy methodology was developed to characterize
the hazardous and other inorganic trace element constituents in new and used domestic plastic food containers. INAA due to
its non destructive, highly sensitive, multielement and low detection limits characteristics was found to be a good technique
for the characterization of polymeric products. Through the variation of irradiation, cooling and counting protocols Al, Ba,
Br, Co, Cr, Eu, Fe, Hg, K, Mn, Na, Nd, Sb, Sc, Th, Ti, V and Zn were determined, while Atomic Absorption Spectroscopy was
used as complementary technique to quantify toxic inorganic elements such as Cd, Pb and Cu. These elements are thought to
originate from the polymer manufacturing processes. It was found that there was gradual increase in the concentration of most
of these elements from new to used plastic samples. Moreover it was also observed that these inorganic elements are present
in higher concentrations in the lower grade containers as compared to the high quality containers. It was also observed that
the good quality containers even with the long usage do not degrade to such an extent as the low quality containers. 相似文献
997.
Roswanira Abdul Wahab Mahiran Basri Raja Noor Zaliha Raja Abdul Rahman Abu Bakar Salleh Mohd Basyaruddin Abdul Rahman Leow Thean Chor 《Applied biochemistry and biotechnology》2012,167(3):612-620
In silico and experimental investigations were conducted to explore the effects of substituting hydrophobic residues, Val, Met, Leu, Ile, Trp, and Phe into Gln 114 of T1 lipase. The in silico investigations accurately predicted the enzymatic characteristics of the mutants in the experimental studies and provided rationalization for some of the experimental observations. Substitution with Leu successfully improved the conformational stability and enzymatic characteristics of T1 lipase. However, replacement of Gln114 with Trp negatively affected T1 lipase and resulted in the largest disruption of protein stability, diminished lipase activity and inferior enzymatic characteristics. These results suggested that the substitution of a larger residue in a densely packed area of the protein core can have considerable effects on the structure and function of an enzyme. This is especially true when the residue is next to the catalytic serine as demonstrated with the Phe and Trp mutation. 相似文献
998.
Pinky Karim Syeda Mohammad Salim Hossain Abu Asad Chowdhury Mohammad Sharifur Rahman Kohji Nishimura Mitsuo Jisaka Tsutomu Nagaya Fumiaki Shono Kazushige Yokota 《Applied biochemistry and biotechnology》2012,167(5):1107-1118
15-deoxy-??12,14-Prostaglandin J2 (15d-PGJ2) is a biologically active molecule serving as a pro-adipogenic factor or an anti-inflammatory regulator. This compound is one of naturally occurring derivatives formed by the non-enzymatic dehydration of PGD2. To determine the endogenous synthesis of 15d-PGJ2, a convenient immunological approach is useful. At first, we established a cloned hybridoma cell line to secrete a monoclonal antibody specific for 15d-PGJ2. For the development of a solid-phase enzyme-linked immunosorbent assay (ELISA), the immobilized antigen using a protein conjugate of 15d-PGJ2 was allowed to react competitively with a monoclonal antibody in the presence of free 15d-PGJ2. Under the optimized conditions, a sensitive calibration curve was generated able to determine the amount of 15d-PGJ2 from 0.5?pg to 9.7?ng with 71?pg of 50% displacement in one assay. Our monoclonal antibody did not recognize other related prostanoids except PGJ2 with cross-reaction of 4%. Our ELISA was demonstrated to be reliable for the quantification of 15d-PGJ2 in the maturation medium of cultured adipocytes by confirming the accuracy and specificity of its determination. The application of our assay revealed that the non-enzymatic formation of 15d-PGJ2 became more evident after several hours of incubation with authentic PGD2 at 37?°C. The results indicate the usefulness of our developed solid-phase ELISA with the monoclonal antibody for further studies on the endogenous synthesis of 15d-PGJ2 and its roles in various cells and tissues. 相似文献
999.
A concise and highly stereoselective total synthesis of manzacidin B and its congeners has been developed following chelation-controlled syn-epoxidation and Lewis acid catalyzed intramolecular regioselective epoxide ring opening to generate the quarternary amine center. Elaboration of the triol moiety to the target molecule was achieved in good overall yield, representing practical total syntheses of manzacidin B and its congeners. From the XRD, NMR, and analytical data, the correct structure of natural manzacidin B, (4R,5R,6R)-6, was confirmed. 相似文献
1000.
Snow crab is a major fishery in the North Atlantic region. During crab processing the proteins are aerosolized and some are
responsible for development of occupational asthma. Tropomyosin and arginine kinase have recently been reported as major snow
crab allergens. A liquid chromatographic tandem mass spectrometric method has been developed for simultaneous analysis of
these two proteins in air samples collected from processing plants. These proteins were initially isolated then characterized
by use of mass spectrometry to determine their primary structure and signature peptides. The signature peptides were chemically
synthesized in light and heavy forms and used as standards for developing the multiple-reaction monitoring transitions to
monitor allergen levels. A validation study was performed; precision and accuracy were 1.8–8% and 91–104%, respectively. Replicate
air samples were collected on air filters from two crab-processing plants in Newfoundland and Labrador (NL) and four located
in Quebec. In NL, measured levels of both tropomyosin and arginine kinase were between 1 and 20 ng m−3. In Quebec plants, however, levels were found to be much higher at 2–2400 ng m−3. Significant differences were also observed among the plants and individual processing workstations. For the first time arginine
kinase has been detected in its aerosolized form in processing plants. In general, levels of the allergens were highest in
the butchering and cooking areas; plant design can, however, have a significant effect on levels of the allergens. 相似文献