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71.
Vinod Chhokar Meenakshi Sangwan Vikas Beniwal Kiran Nehra Kaur S. Nehra 《Applied biochemistry and biotechnology》2010,160(8):2256-2264
Tannase from Aspergillus awamori MTCC 9299 was purified using ammonium sulfate precipitation followed by ion-exchange chromatography. A purification fold
of 19.5 with 13.5% yield was obtained. Temperature of 30 °C and pH of 5.5 were found optimum for tannase activity. The effects
of metals and organic solvents on the activity of tannase were also studied. Metal ions Mg+2, Mn+2, Ca+2, Na+, and K
+
stimulated the tannase activity, while Cu+2, Fe+3, and Co+2 acted as inhibitors of the enzyme. The addition of organic solvents like acetic acid, isoamylalcohol, chloroform, isopropyl
alcohol, and ethanol completely inhibited the enzyme activity. However, butanol and benzene increased the enzyme activity. 相似文献
72.
Kiran Kumar Morishetti Betty De Suan Huang Jessica Marney Yates Jianhua Ren 《Journal of the American Society for Mass Spectrometry》2010,21(4):603-614
The sequence and conformational effects on the gas-phase acidities of peptides have been studied by using two pairs of isomeric
cysteine-polyglycine peptides, CysGly3,4NH2 and Gly3,4CysNH2. The extended Cooks kinetic method was employed to determine the gas-phase acidities using a triple quadrupole mass spectrometer
with an electrospray ionization source. The ion activation was achieved via collision-induced dissociation experiments. The
deprotonation enthalpies (Δacid
H) were determined to be 323.9 ± 2.5 kcal/mol (CysGly3NH2), 319.2 ± 2.3 kcal/mol (CysGly4NH2), 333.8 ± 2.1 kcal/mol (Gly3CysNH2), and 321.9 ± 2.8 kcal/mol (Gly4CysNH2), respectively. The corresponding deprotonation entropies (Δacid
S) of the peptides were estimated. The gas-phase acidities (Δacid
G) were derived to be 318.4 ± 2.5 kcal/mol (CysGly3NH2), 314.9 ± 2.3 kcal/mol (CysGly4NH2), 327.5 ± 2.1 kcal/mol (Gly3CysNH2), and 317.4 ± 2.8 kcal/mol (Gly4CysNH2), respectively. Conformations and energetic information of the neutral and anionic peptides were calculated through simulated
annealing (Tripos), geometry optimization (AM1), and single point energy calculations (B3LYP/6-31+G(d)), respectively. Both
neutral and deprotonated peptides adopt many possible conformations of similar energies. All neutral peptides are mainly random
coils. The two C-cysteine anionic peptides, Gly3,4(Cys-H)−NH2, are also random coils. The two N-cysteine anionic peptides, (Cys-H)−Gly3,4NH2, may exist in both random coils and stretched helices. The two N-cysteine peptides, CysGly3NH2 and CysGly4NH2, are significantly more acidic than the corresponding C-terminal cysteine ones, Gly3CysNH2 and Gly4CysNH2. The stronger acidities of the former may come from the greater stability of the thiolate anion resulting from the interaction
with the helix-macrodipole, in addition to the hydrogen bonding interactions. 相似文献
73.
Low-temperature pyrolysis of methionine-enkephalin-Arg-Gly-Leu has been carried out and the non-volatile residues have been analyzed. The fragments were separated and characterized by LC-UV/Vis-MS/MS. Two major types of pyrolysis products were identified by matching the experimental results with a theoretical list that contains the expected fragments. These products were mainly composed of cyclic oligopeptides and linear fragments produced from the peptide backbone. These fragments have preserved the sequence of amino acids in the peptide. In some cases, a complete or partial loss of an amino-acid side group was observed. Tandem mass spectrometry and cyanogen bromide cleavage experiments were used to confirm the nature of the cyclic and linear pyrolysates, in addition to chromatographic and mass spectrometric data of actual standard synthetic cyclic peptides. 相似文献
74.
Kiran F. Shelke Suryakant B. Sapkal Kirti S. Niralwad Bapurao B. Shingate Murlidhar S. Shingare 《Central European Journal of Chemistry》2010,8(1):12-18
A green, mild and efficient method for Knoevenagel condensation of 3-formylchromone/2-chlroquinoline-3-carbaldehyde with active
methylene compounds such as Meldrum’s acid/ethyl cyanoacetate using biosupported cellulose sulphuric acid (CSA) in the solid-state
by grinding under solvent-free condition has been developed. This method provides several advantages including environmental
friendliness, shor t reaction times, high yields and a simple work-up procedure. Moreover, the CSA was successfully reused
for four cycles without significant loss of activity. 相似文献
75.
76.
M.S.R.N. Kiran M. Ghanashyam Krishna K.A. Padmanabhan 《Solid State Communications》2011,151(7):561-563
Titanium nitride films of a thickness of ∼1.5 μm were deposited on amorphous and crystalline substrates by DC reactive magnetron sputtering at ambient temperature with 100% nitrogen in the sputter gas. The growth of nanostructured, i.e. crystalline nano-grain sized, films at ambient temperature is demonstrated. The microstructure of the films grown on crystalline substrates reveals a larger grain size/crystallite size than that of the films deposited on amorphous substrates. Specular reflectance measurements on films deposited on different substrates indicate that the position of the Ti-N 2s band at 2.33 eV is substrate-dependent, indicating substrate-mediated stoichiometry. This clearly demonstrates that not only structure and microstructure, but also chemical composition of the films is substrate-influenced. The films deposited on amorphous substrates display lower hardness and modulus values than the films deposited on crystalline substrates, with the highest value of hardness being 19 GPa on a lanthanum aluminate substrate. 相似文献
77.
Waheed S. KhanChuanbao Cao Faheem K. ButtZulfiqar Ali M. SafdarLiqing Pan M. Yasir RafiqueQurrat ul Ain Zahid UsmanGhulam Nabi 《Applied Surface Science》2011,257(16):7314-7319
We report here the evolution of zinc based high purity phases with novel morphologies such as Zn3N2 hollow structures, ZnO nanowires and nanopowders, as well as metallic Zn layered hexagonal microparticles at progressively increased reaction temperature of 600 °C, 700 °C, 800 °C under NH3 gas atmosphere using Zn powder precursor and keeping all other experimental parameters unchanged. Growth mechanism for Zn3N2 obtained by nitridation, ZnO by oxidation and Zn microparticles via thermal evaporation & condensation process are discussed briefly. The as-synthesized products were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM). Photoluminescence (PL) studies have revealed very interesting and infrequently observed emission bands at 378 and 661 nm for Zn3N2, 359 and 396 nm for ZnO as well as 389 nm for Zn polyhedral microparticles. 相似文献
78.
The ferroelectric ceramics Ba5RTi3V7O30 (R=Ho, Gd, La) have been synthesized by solid-state reaction technique. Preliminary X-ray structural analysis confirmed a single-phase formation of the compound in orthorhombic structure. Surface morphology of the compounds was studied by scanning electron microscopy (SEM). Detailed studies of electrical properties (i.e., dielectric constant, loss tangent, ac conductivity) as a function of temperature (RT-773 K) and at four different frequencies (1 kHz, 10 kHz, 100 kHz and 1 MHz) show ferroelectric–paraelectric phase transition of the compounds of diffuse-type. The activation energy has been evaluated from ac conductivity following Arrhenius equation. The conductivity pattern shows that it is strongly frequency dependent and obeys Jonscher's power relation. 相似文献
79.
Mauji Ram Salim Khan Prabhakar Jha Mather A. Khan Usha Kiran Saleem Javed Malik Z. Abdin 《Chromatographia》2008,68(1-2):129-133
A simple, rapid, specific and sensitive thin layer chromatographic (TLC) method has been developed for the quantitative estimation of mevalonic acid (MVA) in leaves of medicinal plants; Artemisia annua, Psorelia corylifolia, Vinca rosea, Withania somnifera and Barleria proinites. The assay procedure involved conversion of MVA to its lactone, mevalonolactone (MVAL). Mevalonic acid was extracted from the leaf tissues of plants. Separation of MVAL was carried out on silica gel 60 F254 TLC plates using benzene:acetone (3:2) as the mobile phase. The densitometric determination of MVAL was performed at 600 nm after derivatization with anisaldehyde reagent in absorption–reflectance mode. The method was validated over the linearity range of 100–500 ng spot?1 and correlation coefficient for the calibration curve was >0.99. The average recovery of MVAL, used as internal standard, was higher than 98%. The lower limit of detection was found to be 50 ng spot?1. 相似文献
80.
Jian-Jun Qin Maung Htun Oo Kiran A. Kekre Boris Liberman 《Journal of membrane science》2010,346(1):8-14
The objective of the study was to further develop a novel cleaning technique for reverse osmosis in reclamation of municipal secondary effluent. This technique is a new backwash method via direct osmosis (DO) by intermittent injection of the high salinity (HS) solution without stopping of high pressure pump and it is environment and membrane friendly technique. In the study, DO-HS trials were carried out with a UF-RO pilot system which was operated on site with the secondary treated effluent as the raw feed. Different operating conditions for DO-HS treatment in the actual process were investigated. It was found that the operation for implementation of the DO-HS cleaning technique developed was easy. For the first time, the actual profiles of HS concentration, DO backwash flow rate, brine flow rate and permeate pressure during DO-HS treatment have been demonstrated. It was observed that turbidity of the brine stream during DO-HS treatment at 3 NTU was 5 times higher than that before DO-HS treatment. The results from this study have confirmed the previous hypothesis with DO-HS treatment that there would be a strong driving force for DO backwash to lift and sweep the foulants from the membrane surface which would be carried over to the brine. The optimal plant operating conditions in terms of RO feed flow rate, HS concentration and HS injection time are ready for the DO-HS method to be adopted and validated in a long-term continuous plant operation. 相似文献