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961.
Mohammad Yazdanbakhsh Nahid Lotfian Haman Tavakkoli Roland Boese 《Central European Journal of Chemistry》2011,9(4):585-589
A novel oxo-centered trinuclear mixed-metal carboxylate complex with unsaturated bridging ligands [Fe2Cr(μ3-O)(C3H3O2)6(H2O)3]·NO3·4H2O has been synthesized and characterized by means of Elemental analyses, Infrared spectroscopy and Crystal structure analysis.
The compound crystallizes isotypically in the monoclinic space group type P21/c. In the compound, each M(III) cation is coordinated by six O atoms from four unsaturated carboxylate groups as bridging ligands, one water molecule as
the terminal ligand, and a μ3-oxygen atom in the center of an equilateral triangle. The infrared spectra show resolved bands arising from νasym(COO) and νsym(COO) vibration of bridging carboxylate ligands along with those of νasym(M2M′O) vibration in the complex. The difference between symmetrical and asymmetrical (COO) ligands indicate that the acrylate
bridge is present in the structure of complex.
相似文献
962.
Kutscher DJ Fricker MB Hattendorf B Bettmer J Günther D 《Analytical and bioanalytical chemistry》2011,401(9):2691-2698
A method was developed for the precise and accurate determination of ovalbumin labelled with p-hydroxy-mercuribenzoic acid (pHMB) using polyacrylamide gel electrophoresis with ns-laser ablation–inductively coupled plasma
mass spectrometry. Following systematic optimisation of the ablation process in terms of detection sensitivity, two different
quantification strategies were applied: external calibration using standards of the derivatized protein after 13C+ normalization and, as a proof of concept, label-specific isotope dilution analysis (IDA) using pHMB enriched in the isotope
199Hg. Due to the inhomogeneous distribution of the protein within the gel bands, it could be demonstrated that the IDA approach
was superior in terms of precision and accuracy. Furthermore, it permits a reliable quantification, if more complex separation
protocols are applied, as typically occurring analyte loss and degradation can be compensated for as soon as complete mixture
of spike and sample is achieved. The estimated limit of detection was 160 fmol in the case of ovalbumin. In contrast to earlier
studies using metals naturally present in proteins, no loss of mercury was observed during separation under denaturing conditions
and other sample preparation steps. Using label-specific IDA, the measured isotope ratios in the gel corresponded to recoveries
between 95% and 103%. 相似文献
963.
Ehsan Jazaeri Liyuan Zhang Xungai Wang Takuya Tsuzuki 《Cellulose (London, England)》2011,18(6):1481-1485
The possibility of fabricating carbon nanofibers from cellulose nanofibers was investigated. Cellulose nanofiber of ~50 nm
in diameter was produced using ball milling in an eco-friendly manner. The effect of the drying techniques of cellulose nanofibers
on the morphology of carbon residue was studied. After pyrolysis of freeze-dried cellulose nanofibers below 600 °C, amorphous
carbon fibers of ~20 nm in diameter were obtained. The pyrolysis of oven-dried precursors resulted in the loss of original
fibrous structures. The different results arising from the two drying techniques are attributed to the difference in the spatial
distance between cellulose nanofiber precursors. 相似文献
964.
Metin Aktaş 《Journal of mathematical chemistry》2011,49(9):1831-1842
By converting the rectangular basis potential V(x, y) into the form as \({V({r}) + V({r},\varphi)}\) described by the pseudo central plus noncentral potential, particular solutions of the two dimensional Schrödinger equation in plane-polar coordinates have been carried out through the analytic approaching technique of the Nikiforov and Uvarov. Both the exact bound state energy spectra and the corresponding bound state wavefunctions of the complete system are determined explicitly and in closed forms. Our presented results are identical to those of the previous works and they may also be useful for investigation and analysis of structural characteristics in a variety of quantum systems. 相似文献
965.
In the present study, a rapid and sensitive LC-ESI-MS/MS method for quantification of (S)-fluoxetine as a native marker in mass spectrometry (MS) binding assays addressing the human serotonin transporter (hSERT)
was developed and validated. The concept of MS binding assays based on mass spectrometric quantification of a nonlabeled marker
recently introduced by us represents a promising alternative to conventional radioligand binding without the drawbacks inherently
connected with radioisotope labeling. For high-performance liquid chromatography (HPLC), a 20 × 2-mm RP-18 column with a mobile
phase composed of acetonitrile and ammonium bicarbonate buffer (5 mmol L−1, pH 9.5) at a ratio of 80:20 (v/v) and a flow rate of 800 μL min−1 in an isocratic mode were used, resulting in a chromatographic cycle time of 60 s. Employing [2H5]fluoxetine as internal standard enabled ESI-MS/MS quantification of (S)-fluoxetine between 3 nmol L−1 and 50 pmol L−1 (LLOQ) in matrix obtained from binding experiments without the need of any sample preparation. Validation of the method showed
that linearity, intra-, and inter-batch accuracy as well as precision meet the requirements of the FDA guidance for bioanalytical
method validation. Considering sensitivity and speed, the established method is clearly superior to those published for biological
matrices so far. Furthermore, the method was transferred to other RP-18 columns of different lengths and respective validation
experiments demonstrated its versatility and chromatographic robustness. Finally, the newly developed method was successfully
applied to MS binding assays for hSERT. The affinity determined for (S)-fluoxetine in saturation experiments was in good agreement with literature data obtained in respective radioligand binding
assays. 相似文献
966.
A glassy carbon electrode was modified with electropolymerized film of diphenylamine sulfonic acid (DPASA). Electropolymerization was performed by cyclic voltammetry in 0.1 M KCl solution. The modified electrode showed an excellent
electrocatalytic effect towards oxidation of dopamine (DA) and ascorbic acid (AA). Electrostatic interaction between the negatively charged poly(DPASA) film and either cationic DA species or anionic AA
species favorably contributed to the redox response of DA and AA. Anodic peaks of DA and AA in their mixture were well separated
by ca 168 and −11.8 mV. The proposed modified electrode was utilized for selective determination of dopamine in the concentration
range of 5.0 × 10t7–2.0 × 10−5 M in the presence of high concentration of ascorbic acid. Detection limit was 6.5 × 10−9 M. 相似文献
967.
A new analytical detector based on a liquid drop resistor–capacitor (RC) filter is described, in which transformed gain vs. frequency curves are used to analyze compounds. This detector can be used to detect either charged or neutral species (that are dielectrically
different) which are dissolved in a liquid (e.g., water, alcohol, solvent mixtures, etc.). This device was fabricated by modifying
an electrowetting on dielectric (EWOD)-based experimental setup. When a liquid drop is placed on a dielectric surface, the
system acts as a RC filter. At a given frequency, gain is a function of conductivity, surface tension, dielectric constant, double-layer thickness of the solid–liquid drop interface,
as well as the applied voltage. Since different liquids and solutions have different physical properties, each liquid/solution
has a unique curve (peak) in gain vs. frequency plot. This is the basic principle behind the detector. Different amounts of
zinc chloride dissolved in water, benzalkonium chloride in water, 1-methylimidazole in water, cetyltrimethyl-ammonium chloride
(CTAC) in water, and CTAC dissolved in ethylene glycol solutions were tested with the detector as proof of principle. The
device can be used as a stand-alone detector or can easily be coupled with droplet based microfluidic lab-on-a-chip systems
such as EWOD-based microfluidic chips. 相似文献
968.
Dörr FA Kovačevi B Maksi ZB Pinto E Volmer DA 《Journal of the American Society for Mass Spectrometry》2011,22(11):2011-2020
The aim of this study was to investigate the unusual gas-phase dissociation behavior of two epimer pairs of protonated gonyautoxins
(GTX) following electrospray ionization in comparison to their deprotonated counterparts. The chemical structures of the investigated
GTX1-4 variants vary in their substitution pattern at N-1 and the stereochemical orientation of the hydroxysulfate group at C-11
(11α for GTX1/2 versus 11β for GTX3/4). The direct comparison of mass spectra in positive and negative ion modes illustrated two distinct features: first, an intriguing
difference between protonated 11α and 11β species, where 11α conformations exhibited almost complete dissociation of [M +
H]+ ions via facile SO3 elimination, while 11β species remained mostly intact as [M + H]+; and second, the lack of such differences for the deprotonated counterparts. In this study, we propose an acid-catalyzed
elimination mechanism from density functional theory calculations, initiated by a proton transfer of a guanidinium proton
to the hydroxysulfate group with simultaneous SO3 release, which is only possible for the 11α conformation based on intramolecular distances. The same mechanism explains the
lack of a comparable SO3 loss in the negative ion mode. CID experiments supported this proposed mechanism for GTX1 and GTX2. Computational modeling of product ions seen in the CID spectra of GTX3 and GTX4 established that the lowest energy dissociation pathway for the 11β epimers is elimination of water with the possibility
for further SO3 release from the intermediate product. Experimental data for structurally analogous decarbamoyl gonyautoxins confirmed the
evidence for the GTX compounds as well as the proposed elimination mechanisms. 相似文献
969.
Armin Ferse 《Journal of Solid State Electrochemistry》2011,15(10):2173-2175
The arguments of Malatesta (J Solution Chem 29:771–779, 2000; Fluid Phase Equil 295:244–248, 2010) exclude the experimental determination of individual ion activity coefficients. I agree that a measurement of single-ion
activity coefficients is impossible. But the comment of Malatesta (J Solid State Electrochem (in press), 2011) in the connection with the purely mathematical procedure developed by Ferse and Müller (J Solid State Electrochem (in press),
2011) is senseless because there is no new aspect which is not also given in the paper of Ferse and Müller (J Solid State Electrochem
(in press), 2011). All of the mentioned problems are already discussed and clarified in the publication by Ferse and Müller (J Solid State
Electrochem (in press), 2011). The purely mathematical method is a possibility to obtain the concentration functions for the individual activity coefficients
of the complementary ion species by factorizing a product function of the experimentally accessible concentration dependence
of the mean activity coefficients to the required power. 相似文献
970.
Clarke DJ Murray E Hupp T Mackay CL Langridge-Smith PR 《Journal of the American Society for Mass Spectrometry》2011,22(8):1432-1440
Noncovalent protein–ligand and protein–protein complexes are readily detected using electrospray ionization mass spectrometry
(ESI MS). Furthermore, recent reports have demonstrated that careful use of electron capture dissociation (ECD) fragmentation
allows covalent backbone bonds of protein complexes to be dissociated without disruption of noncovalent protein–ligand interactions.
In this way the site of protein–ligand interfaces can be identified. To date, protein–ligand complexes, which have proven
tractable to this technique, have been mediated by ionic electrostatic interactions, i.e., ion pair interactions or salt bridging.
Here we extend this methodology by applying ECD to study a protein–peptide complex that contains no electrostatics interactions.
We analyzed the complex between the 21 kDa p53-inhibitor protein anterior gradient-2 and its hexapeptide binding ligand (PTTIYY).
ECD fragmentation of the 1:1 complex occurs with retention of protein–peptide binding and analysis of the resulting fragments
allows the binding interface to be localized to a C-terminal region between residues 109 and 175. These finding are supported
by a solution-phase competition assay, which implicates the region between residues 108 and 122 within AGR2 as the PTTIYY
binding interface. Our study expands previous findings by demonstrating that top-down ECD mass spectrometry can be used to
determine directly the sites of peptide–protein interfaces. This highlights the growing potential of using ECD and related
top-down fragmentation techniques for interrogation of protein–protein interfaces. 相似文献