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21.
The addition of the dianion of Johnson’s sulfoximine to α,ω-halogenoesters evolves by an intramolecular heterocyclization to provide a direct access to 2-alkylidenetetrahydrofurans bearing a chiral sulfur atom via domino addition-elimination/SN reactions. 相似文献
22.
采用双乳液法研制配糖蛋白B的肠溶微胶囊,考察了微胶囊的形态、粒径及其分布,在摸拟肠液的缓冲液中进行溶解释放试验。配制了两种口服微胶囊混悬制剂,并考察了它的稳定性。 相似文献
23.
Keith R. Roby 《Theoretical chemistry accounts》1974,33(2):105-113
The mathematical basis of LCAO MO theory is studied, both within the Hartree-Fock approximation and in more exact formulations. The basic LCAO expansion for molecular orbitals ¦> in terms of atomic orbitals ¦x> is conveniently written ¦> = ¦x>
S
–1
B where S is the overlap matrix for atomic orbitals and B is the matrix of atomic orbital-molecular orbital overlaps. It is suggested that matrices P and Q, defined by P=B B and Q=BnB where n is the matrix of molecular orbital occupation numbers, are appropriate to the interpretation of molecular calculations in terms of atomic orbital components, electronic populations and the degree of bonding. Implications for Hartree-Fock calculations are investigated. 相似文献
24.
Summary This paper reports a quick, and simple method for quantitative determination of C2 to C6 hydrocarbons in stabilized crude oil without using a back flush system. A mixture of crude oil and internal standard is injected into a GC equipped with a 6 meter length of fused silica capillary as a guard column. The light hydrocarbons are separated individually up to the last peak of the hexane group with the heavier components trapped in the guard column. The total analysis time for each sample is 15 minutes. The base line is table for up to 15 consecutive analyses. The guard column and the injector port are then reconditioned by simply heating them for one hour at 300 °C. 相似文献
25.
Jef Peeters Peter Neeskens Marcus Eli Brewster 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):137-139
Pirodavir, 4-[2-[1-(6-Methyl-3-pyridazinyl)-4-piperidinyl]ethoxy]benzoic acid ethyl ester, is an antiviral compound which
has low aqueous solubility (<0.01 mg/ml). The compound is a weak base (pKa 5.8) with high lipophicity (logP 4.44). Ionization
of the compound increases the solubility in acidic medium to 2.3 mg/ml at pH 2.4. However, a low pH is not acceptable for
nasal application as this would induce irritation.
Extensive solubility studies were performed using different types of substituted cyclodextrins in order to select an appropriate
derivate capable of increasing solubility to an acceptable level for formulations for nasal application. Aqueous solubility
of pirodavir increased in a linear fashion with increasing concentration of most of the substituted cyclodextrins. However,
using 2-hydropropyl-β-cyclodextrin (HPBCD) the solubility increased in a non-linear fashion. Based on these studies HPBCD
was selected as the most appropriate excipient.
To support a clinical study on the treatment of rhinovirus cold by intranasal Pirodavir formulations were developed containing
up to 5 mg/ml of pirodavir and up to 10% of HPBCD. Stability of the formulations was studied and found to be acceptable. 相似文献
26.
A sensitive and convenient high-performance liquid chromatography-tandem mass spectrometry(HPLC-MS/MS) assay is described for the (5-HT(lB/lD)) receptor agonist sumatriptan in human plasma. Sumatriptan was recovered from plasma (81.8 +/- 6.8%) by liquid-liquid extraction. The mobile phase flow rate was 0.3 mL/min and consisted of methanol:water:formic acid (90:10:0.1, v/v/v). The analytical column (4.6 x 100 mm) was packed with Partisil C(8) (5 micro m). The standard curve was linear from 0.7 to 70.4 ng/mL (r(2) > 0.99). The lower limit of quantitation was 0.7 ng/mL. The assay was specific, accurate (percentage deviation from nominal concentrations were <15%), precise and reproducible (within- and between-day coefficients of variation <10.3%). Sumatriptan in plasma was stable over three freeze/thaw cycles and at room temperature for one day. The utility of the assay was demonstrated by following sumatriptan plasma concentrations in two healthy subjects for 8-12 h following a single 20 mg intranasal dose. 相似文献
27.
K. Terada T. Masuda Y. Yoshihashi E. Yonemochi 《Journal of Thermal Analysis and Calorimetry》2006,85(3):675-680
Isothermal
microcalorimetry was used to evaluate excipient compatibility of solid dosage
form. Oxybutynin hydrochloride and cefaclor were used as model drugs for compatibility
test with excipients. The calorimetric data for compatibility test were compared
with those of HPLC data. Evaluation of compatibility between drug and excipient
of solid dosage form might be possible to use isothermal microcalorimetry
instead of conventional method. By using microcalorimetric method, the evaluation
of the compatibility between drug and excipient could be successfully performed
with a simple operation in a short time. The application of the isothermal
microcalorimetry would be useful for the screening test of the drug compatibility
with excipients. 相似文献
28.
Summary A rapid and accurate LC method is described for simultaneous determination of pseudoephedrine hydrochloride (PSE), acetaminophen (AMP), dextromethorphen hydrobromide (DEX), and diphenhydramine hydrochloride (DPH) in a compound formulation. Chromatographic separation of the four drugs was achieved on a Hypersil CN column (150 mm × 4.6 mm, 5 m particle) by use of a mobile phase comprising a mixture of 3 mM ion-pairing solution, 2% aqueous triethylamine solution, and 2 M phosphoric acid, 68:48:88 (v/v), pH 3.0, delivered at 1.0 mL min–1. Compounds were detected at 215 nm and the run time was less than 10 min. The linearity, accuracy, and precision of the method were found to be acceptable over the concentration ranges 6.1–36.4 g mL–1 for PSE, 65.0–390.0 g mL–1 for AMP, 3.1–18.6 g mL–1 for DEX, and 5.0–30.0 g mL–1 for DPH. 相似文献
29.
30.
A finite volume cell‐centered Lagrangian hydrodynamics approach, formulated in Cartesian frame, is presented for solving elasto‐plastic response of solids in general unstructured grids. Because solid materials can sustain significant shear deformation, evolution equations for stress and strain fields are solved in addition to mass, momentum, and energy conservation laws. The total stress is split into deviatoric shear stress and dilatational components. The dilatational response of the material is modeled using the Mie‐Grüneisen equation of state. A predicted trial elastic deviatoric stress state is evolved assuming a pure elastic deformation in accordance with the hypo‐elastic stress‐strain relation. The evolution equations are advanced in time by constructing vertex velocity and corner traction force vectors using multi‐dimensional Riemann solutions erected at mesh vertices. Conservation of momentum and total energy along with the increase in entropy principle are invoked for computing these quantities at the vertices. Final state of deviatoric stress is effected via radial return algorithm based on the J‐2 von Mises yield condition. The scheme presented in this work is second‐order accurate both in space and time. The suitability of the scheme is evinced by solving one‐ and two‐dimensional benchmark problems both in structured grids and in unstructured grids with polygonal cells. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献