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161.
Mass determination by mass spectrometric methods (electrospray ionization mass spectrometry (ESI-MS), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS)) of sodiumdodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE)-separated proteins is a well known procedure and reliable protocols are available. In our efforts to use the established methods to determine the molecular mass of the disulfide bridged, heterodimeric glycoprotein GP3 and to determine the carbohydrate content of each protein subunit we developed an in-gel chemical deglycosylation method. For this purpose we established experimental conditions that allow maximum extraction of the high molecular mass protein subunits and developed a routine method to apply the HF-pyridine deglycosylation protocol to proteins isolated from polyacrylamide gel pieces. The novel protocol and extraction procedure described can be used to analyze O-glycosylated proteins up to 150 kDa after SDS-PAGE separation. 相似文献
162.
The preconcentration and voltammetric behavior of BiIII on a sodium humate modified carbon paste electrode was studied by means of cyclic voltammetry (CV) and differential pulse stripping voltammetry (DPSV). The proposed measurement involves an initial nonelectrolytic preconcentration step in which BiIII is complexed by the surface modifier in a solution of 0.05 M KNO3-0.0106 M HNO3 (pH 2.0) and a subsequent electrochemical scan step in which the preconcentrated BiIII was reduced and then oxidized promptly in supporting electrolyte of 0.5 M HNO3. The resulting DPSV anodic current was proportional to the concentration of BiIII ion over the range of 4.78 × 10−8–1.44 × 10−5 M. The detection limit was 4.78 × 10−8 M. The proposed method was used to determine bismuth in various samples. Various factors affecting the electrode behavior were also investigated at the same time. 相似文献
163.
5-Hydroxytryptamino-induced calcium sparks in cultured rat stomach fundus smooth muscle cells 总被引:1,自引:0,他引:1
With the imaging fluorescence probe of Ca2+ (fluo-3) and a laser scanning confocal micro-scope, the spontaneous localized calcium release event was first discovered in resting rat cardiac myocytes by Cheng[1] in 1993. A mathematical simulation is developed with computer in order to reveal the effect, which is immediately suggested that these events are likely to reflect the local-ized release of Ca2+ from a small cluster of ryanodine-sensitive Ca2+ release channels in sar-coplasmic reticulum … 相似文献
164.
DFT calculations have been carried out for 2-, 3- and 4-methoxybenzyl alcohol radical cations (1+, 3+ and 4+, respectively) and the α-methyl derivatives 2+ and 5+ using the UB3LYP/6-31G(d) method. The theoretical results have been compared with the experimental rate constants for deprotonation of 1+-5+ under acidic and basic conditions. In acidic solution, the decay of 1+-5+ proceeds by cleavage of the C-H bond, while in the presence of −OH all the radical cations undergo deprotonation from the α-OH group. This pH-dependent change in mechanism has been interpreted qualitatively in terms of simple frontier molecular orbital theory. The −OH induced α-O-H deprotonation is consistent with a charge controlled reaction, whereas the C-H deprotonation, observed when the base is H2O, appears to be affected by frontier orbital interactions. 相似文献
165.
The cationization of poly(ethylene glycol)s, PEG 4000 and PEG 6000, under matrix-assisted laser desorption/ionization conditions was studied by using different concentration ratios of the sodium ion, as the reference ion, and another alkali metal ion (Li(+), K(+), Rb(+), Cs(+)). A linear correlation was found between the intensity ratio of the sodiated PEGs and PEGs cationized with alkali metal ions versus the initial concentration ratio of sodium and alkali metal ions. The slopes of these straight lines are proposed as a novel selectivity ratio for the ionization process. The intensity distribution of the cationized PEGs was also investigated. It was found that the cationized oligomers follow Poisson statistics. The M(n) and M(w) values were also evaluated. An explanation for the observed effects is given. 相似文献
166.
HO. radical is an aggressive reagent to abstract hydrogen from diverse substitutes and lead them to degradation, however, in
reaction of active oxygen species with lignins, complex phenolic polymers, in dispersed lignocellulose such as pulp for environment-benign
delignification, HO. radicals should be eliminated as more as possible to prevent cellulose from unfavorably concomitant degradation. A reaction
system of O3 is constructed under UV laser flash irradiation, and HO. radicals are controlled efficiently by it. A new mechanism is proposed, for the first time, that O. radicals generated from reaction of O3 with UV laser flash irradiation might be the contributor to scavenge HO. radicals. 相似文献
167.
D. V. Khudyakov A. V. Mikhonin I. V. Rubtsov V. A. nadtochenko 《Russian Chemical Bulletin》1997,46(9):1531-1535
The kinetics of the formation and decay of photoexcited radical ion pairs of donoracceptor charge-transfer complexes between
C60 andN,N-diethylaniline (DEA) in chlorobenzene was studied by picosecond laser-induced diffraction gratings. It was established that
the anisotropy of polarization of the diffraction signal decreases as the concentration of DEA increases. The radical ion
states of the photoexcited C60
−...DEA+ complex have zero anisotropy. This effect is likely due to the isotropic intracomplex transfer of an electron from the local
excited state to the radical ion state. The rate constant of quenching of the singlet excited C60 byN,N-diethylaniline (1.4·1010 L mol−1 s−1) and the lifetimes of the solventseparated C60
−...DEA+ and tight [C60
−...DEA+] (95±7 and 31±4 ps, respectively) radical ion pairs were measured.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1605–1610, September, 1997. 相似文献
168.
Radiation formation of polymeric nanogels 总被引:4,自引:0,他引:4
An alternative method of synthesis of polymeric nanogels is proposed, based not on polymerization, but on intramolecular crosslinking of polymer chains, initiated by pulse irradiation in dilute aqueous solutions. Kinetic data show that for many water-soluble polymers irradiation under these conditions result in intramolecular crosslinking. Preliminary product studies on poly(vinyl alcohol) indicate that in fact internally crosslinked macromolecules can be obtained by this technique. 相似文献
169.
The electrocatalytic oxidation of cephalexin and cefazolin has been studied at a carbon paste electrode modified with cobalt salophen (CoSal) by cyclic voltammetry. The selectivity of the carbon paste modified with CoSal in detecting cephalexin and cefazolin was examined. To suggest the electrocatalytic mechanism for electro-oxidation of cefazolin, the electrochemical behavior of ceftriaxone was investigated which has a thiol group out of the beta lactam ring. The electrocatalytic oxidation of these antibiotics is shown to be irreversible at the CoSal modified electrode. Scan rate dependence of cefazolin, which is a sulfur-containing compound, has been examined. The results indicated that the electrocatalytic oxidation of the compounds is diffusion controlled. The responses of the modified electrode were compared with those of unmodified electrode and it has shown that the modified electrode has better sensitivity than unmodified electrode to the detection of cefazolin. The overall number of electrons contributed to the oxidation of cefazolin is obtained 1 by chronoamperometry; the number of electron involved in the rate-determining step was 1. The results of differential pulse voltammetry (DPV) using the modified electrode with high sensitivity were applied for the determination of cefazolin in human synthetic serum samples. The linear range was obtained from 1 × 10−5 to 1 × 10−3 M for DPV determination of cefazolin in buffered solutions (pH 3.0). 相似文献
170.
Proteins with molecular mass (M(r)) <20 kDa are often poorly separated in 2-D sodium dodecyl sulfate polyacrylamide gel electrophoresis. In addition, low-M(r) proteins may not be readily identified using peptide mass fingerprinting (PMF) owing to the small number of peptides generated in tryptic digestion. In this work, we used a 2-D liquid separation method based on chromatofocusing and non-porous silica reversed-phase high-performance liquid chromatography to purify proteins for matrix-assisted laser desorption/ionization time-of-flight mass spectrometric (MALDI-TOFMS) analysis and protein identification. Several proteins were identified using the PMF method where the result was supported using an accurate M(r) value obtained from electrospray ionization TOFMS. However, many proteins were not identified owing to an insufficient number of peptides observed in the MALDI-TOF experiments. The small number of peptides detected in MALDI-TOFMS can result from internal fragmentation, the few arginines in its sequence and incomplete tryptic digestion. MALDI-QTOFMS/MS can be used to identify many of these proteins. The accurate experimental M(r) and pI confirm identification and aid in identifying post-translational modifications such as truncations and acetylations. In some cases, high-quality MS/MS data obtained from the MALDI-QTOF spectrometer overcome preferential cleavages and result in protein identification. 相似文献