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61.
2-Diethylaminoethanethiol hydrochloride is proposed for spectrophotometric determination of palladium(II). The sensitivity of the reaction is 0.0085 smg/cm2 and the yellow colored complex shows absorption maxima at 258 mμ and 303 mμ. Color development is slow in the cold but complete after heating for 10–15 min. The optimum pH range is 3.5 to 5.5 and the system adheres to Beer's law between 0.2 and 16.8 p.p.m. of palladium. The average and maximum relative standard deviations were 0.60% and 1.40% respectively. Interferences due to other platinum metals were studied and a procedure is suggested for the simultaneous determination of rhodium and palladium. 相似文献
62.
Hixson KK Rodriguez N Camp DG Strittmatter EF Lipton MS Smith RD 《Electrophoresis》2002,23(18):3224-3232
A method for the complete peptide mapping of the model integral membrane protein bacteri-orhodopsin is demonstrated. Utilizing more effective enzymatic digestion, procedures with capillary liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) and tandem mass spectrometry (MS/MS), all predicted tryptic digestion products were detected, as well as peptides from all previously reported post-translational modifications of bacteriorhodopsin. A significant contribution of chymotryptic-like digestion products was also observed. A characterization of the behavior of hydrophobic integral membrane peptides in a reversed-phase liquid chromatographic separation is also provided. The method reported here offers improved compatibility of the solubilizing reagents with both the chromatography and mass spectrometry, rendering it suitable for high-throughput proteomic applications. 相似文献
63.
ágnes Zsigmond Ramóna Madácsi Ferenc Notheisz Erzsébet Mernyák and Ferenc Joó 《Reaction Kinetics and Catalysis Letters》2006,87(2):297-304
Summary [RuCl2(PPh3)3], [{RuCl2(TPPMS)2}2] and their heterogenized analogs were applied in the selective hydrogenation of 17-keto- and α,β-unsaturated ketosteroids.
In basic conditions these complexes selectively hydrogenated the C=O bonds, similarly to the results obtained in the case
of α,β-unsaturated aldehydes. A new method was developed for the synthesis of an expensive steroid alcohol, which can be prepared
traditionally in a more complicated way. 相似文献
64.
The purpose of this study is to investigate the influence of nickel, which is an alloying element in commonly used metallic biomaterials, on the biomaterials mineralization process. An electrochemical method was developed to quantify this metal ion in osteoblast-like cell culture medium (OST) by performing adsorptive cathodic stripping voltammetry (CSV) with dimethylglyoxime (DMG) at a mercury film microelectrode (MFM). The optimized analytical conditions and the square-wave CSV parameters for the analysis are: DMG concentration: 5.00 × 10−4 mol L−1; ammonium chloride buffer: 0.10 mol L−1 (pH 9.2); frequency: 50 Hz, amplitude 20 mV; step: 2 mV; adsorption time: 10 s, deposition potential: −0.70 V and reduction potential: −1.20 V. The limit of detection was 7.70 × 10−9 mol L−1 for an adsorption time of 10 s. The results achieved by CSV using the MFM were compared to those obtained by atomic absorption spectrometry (AAS) to ensure the reliability of the electrochemical method. The mineralization process was evaluated by biochemical and histochemical assays. 相似文献
65.
A way of using gravity flow to induce a linear convection within a microfluidic system is presented. It is shown and mathematically supported that tilting a 1 cm long covered microchannel is enough to generate flow rates up to 1000 nL.min(-1), which represents a linear velocity of 2.4 mm.s(-1). This paper also presents a method to monitor the microfluidic events occurring in a covered microchannel when a difference of pressure is applied to force a solution to flow in said covered microchannel, thanks to electrodes inserted in the microfluidic device. Gravity-induced flow monitored electrochemically is applied to the performance of a parallel-microchannel enzyme-linked immunosorbent assay (ELISA) of the thyroid-stimulating hormone (TSH) with electrochemical detection. A simple method for generating and monitoring fluid flows is described, which can, for instance, be used for controlling parallel assays in microsystems. 相似文献
66.
67.
Jo?o L M Santos Arnaud Clausse José L F C Lima M L M F S Saraiva António O S Rangel 《Analytical sciences》2005,21(4):461-464
A new flow methodology exploiting the multi-pumping approach was developed for the spectrophotometric determination of ambroxol hydrochloride in pharmaceutical preparations. The flow manifold was implemented by using, exclusively, multiple solenoid-actuated micro-pumps, which acted simultaneously as sample insertion, solutions propelling and reagents commutation units. Linear calibration plots were obtained over an ambroxol concentration ranging from 10 to 200 mg l(-1) (r.s.d. < 0.5%, n = 15) and a sampling rate of about 60 samples per hour (flow rate = 1.92 ml min(-1), sample volume = 80 microl). 相似文献
68.
Low-energy CAD product-ion spectra of various molecular species of phosphatidylserine (PS) in the forms of [M−H]− and [M−2H+Alk]− in the negative-ion mode, as well as in the forms of [M+H]+, [M+Alk]+, [M−H+2Alk]+, and [M−2H+3Alk]+ (where Alk=Li, Na) in the positive-ion mode contain rich fragment ions that are applicable for structural determination.
Following CAD, the [M−H]− ion of PS undergoes dissociation to eliminate the serine moiety (loss of C3H5NO2) to give a [M−H−87]− ion, which equals to the [M−H]− ion of a phoshatidic acid (PA) and give rise to a MS3-spectrum that is identical to the MS2-spectrum of PA. The major fragmentation process for the [M−2H+Alk]− ion of PS arises from primary loss of 87 to give rise to a [M−2H+Alk−87]− ion, followed by loss of fatty acid substituents as acids (RxCO2H, x=1,2) or as alkali salts (e. g., RxCO2Li, x=1,2). These fragmentations result in a greater abundance of [M−2H+Alk−87−R2CO2H]− than [M−2H+Alk−87−R1CO2H]− and a greater abundance of [M−2H+Alk−87−R2CO2Li]− than [M−2H+Alk−87−R1CO2Li]−; while further dissociation of the [M−2H+Alk−87−R2(or 1)CO2Li]− ions gives a preferential formation of the carboxylate anion at sn-1 (R1CO2−) over that at sn-2 (R2CO2−). Other major fragmentation process arises from differential loss of the fatty acid substituents as ketenes (loss of Rx′CH=CO, x=1,2). This results in a more prominent [M−2H+Alk−R2′CH=CO]− ion than [M−2H+Alk−R1′CH=CO]− ion. Ions informative for structural characterization of PS are of low abundance in the MS2-spectra of both the [M+H]+ and the [M+Alk]+ ions, but are abundant in the MS3-spectra. The MS2-spectrum of the [M+Alk]+ ion contains a unique ion corresponding to internal loss of a phosphate group probably via the fragmentation processes involving
rearrangement steps. The [M−H+2Alk]+ ion of PS yields a major [M−H+2Alk−87]+ ion, which is equivalent to an alkali adduct ion of a monoalkali salt of PA and gives rise to a greater abundance of [M−H+2Alk−87−R1CO2H]+ than [M−H+2Alk−87−R2CO2H]+. Similarly, the [M−2H+3Alk]+ ion of PS also yields a prominent [M−2H+3Alk−87]+ ion, which undergoes consecutive dissociation processes that involve differential losses of the two fatty acyl substituents.
Because all of the above tandem mass spectra contain several sets of ion pairs involving differential losses of the fatty
acid substituents as ketenes or as free fatty acids, the identities of the fatty acyl substituents and their positions on
the glycerol backbone can be easily assigned by the drastic differences in the abundances of the ions in each pair. 相似文献
69.
Streeter I Wain AJ Thompson M Compton RG 《The journal of physical chemistry. B》2005,109(25):12636-12649
An in situ electrochemical electron spin resonance (ESR) study on the electro-oxidation of para-chloroaniline, para-bromoaniline, and para-iodoaniline dissolved in acetonitrile at gold electrodes is reported. ESR spectra obtained using a tubular flow cell reveal the presence of a paramagnetic dimer product derived from para-aminodiphenylamine, during oxidative electrolysis, suggesting the coupling of reactive electrogenerated radical cations with neutral parent haloaniline molecules. The ESR signal intensity behaves in a manner expected for a radical species reacting with second-order kinetics, suggesting the paramagnetic dimer is, itself, unstable. The theory describing the ESR signal intensity flow rate behavior for this reaction mechanism is developed for the tubular arrangement and used to extract mechanistic and kinetic data from the experimental results for the cases of para-chloroaniline and para-bromoaniline. Further mechanistic aspects, including proton and halide ion expulsion during dimerization, are explored voltammetrically and with the aid of digital simulations using Digisim. Comparison of the ESR signal and voltammetric measurements suggests that an additional mechanism operates which does not lead to paramagnetic products. Additionally, the in situ electrolysis of N,N-dimethyl-para-bromoaniline is reported to generate the stable radical cation of N,N,N',N'-tetramethylbenzidine, and a mechanism of electro-oxidation is, thus, proposed. 相似文献
70.
Bond AD García F Jantos K Lawson GT McPartlin M Wright DS 《Chemical communications (Cambridge, England)》2002,(12):1276-1277
The novel, deca-lithium cage [(mtaNHLi)(As2(Nmta)5)-Li(4).2thf]2 (1) (mtaN = 5-methylthiazolyl, C4H4N2S) contains an imido-bridged tetraanion [(mtaN)2As(mu-Nmta)-As(Nmta)2]4-, which represents a new type of multi-functional imido group 15 ligand framework (homologous with group 15 anions of the type [As(NR)3]3-). 相似文献