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61.
Johannes P. F. G. Helsper Ruud J. B. Peters Lambertus Brouwer Stefan Weigel 《Analytical and bioanalytical chemistry》2013,405(4):1181-1189
This paper describes the characterisation of liposome-type nanoparticles (NPs) dispersed in a beverage matrix. Characterisation is based on a two-step procedure: first, liposomes are separated on the basis of size in the nanometre range by use of hydrodynamic chromatography (HDC); second, chemical characterisation is performed by use of MALDI–TOF mass spectrometry (MS). Characterisation of three types of Coatsome liposome, a commercially available type of empty liposome, was investigated. All three liposome types, Coatsome A?=?anionic, N?=?neutral, and C?=?cationic, gave single peaks in HDC, reflecting diameters of 153, 187, and 205 nm, respectively. Subsequent MALDI–TOF MS in positive mode furnished major signals at m/z?=?734.5 ([M?+?H]+ adduct) and m/z?=?756.6 ([M?+?Na]+ adduct) of l-(α)-dipalmitoylphosphatidylcholine (DPPC) monomer and dimeric adducts at m/z?=?1468.1 and m/z?=?1490.1, respectively. MALDI–TOF MS in negative mode gave a signal at m/z?=?721.3 ([M???H]? adduct) of l-(α)-dipalmitoylphosphatidylglycerol (DPPG), except for Coatsome C which lacks this phospholipid. After HDC separation of Coatsome A NPs the major DPPC and DPPG signals can be detected in the expected fractions by use of MALDI–TOF MS in positive and negative modes, respectively. Validation of the analytical strategy revealed linearity (R 2?>?0.99), repeatability (relative standard deviation <10 %), and reproducibility (relative standard deviation between days <10 %) were good, recovery was 61?±?5 %, and the limit of quantification was 1 mg?mL?1 in this matrix. With 4 mg Coatsome A mL?1 20 out of 20 samples furnished the 734.5 and 756.6 signals typical of DPPC in MALDI–TOF MS characterisation. 相似文献
62.
63.
Elisabeth Siebert Marius Horch Yvonne Rippers Johannes Fritsch Stefan Frielingsdorf Oliver Lenz Francisco VelazquezEscobar Friedrich Siebert Lars Paasche Uwe Kuhlmann Friedhelm Lendzian Maria‐Andrea Mroginski Ingo Zebger Peter Hildebrandt 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2013,125(19):5267-5270
64.
Georg Steinhauser Stefan Merz Johannes H. Sterba 《Journal of Radioanalytical and Nuclear Chemistry》2013,296(1):165-168
We present and discuss a modification of instrumental neutron activation analysis (INAA) that is sensitive for nuclides that do not yield (suitable) activation products but have high cross sections for neutron absorption. Their presence in a sample may thwart INAA by neutron flux suppression inside the sample, but they remain undetected and thus unnoticed by the analyst. In particular, this refers to Li, B, Cd and Gd. The proposed method—instrumental neutron absorption activation analysis (INAAA)—takes advantage of the flux depression inside the sample caused by the neutron absorbers. It is made visible by addition of an activatable nuclide (indicator). The concentration of the neutron absorber (analyte) causes a decrease in activity of the indicator. The activity difference between a mixed sample (sample plus indicator) and the pure indicator carries the analytical information. The calibration curve hence follows a reciprocal exponential function. In a proof-of-principle experiment, the applicability for the quantification of boron was exemplified. In presence of only one neutron absorber (whose nature is known), INAAA can be applied easily for quantification of the analyte in powdered or liquid samples. Although INAAA is no trace sensitive method, it has the potential to increase the reliability of INAA analyses by fast and straightforward quality control (even in presence of two or more neutron absorbing nuclides). It is especially suited for research reactors that do not operate a prompt gamma neutron activation analysis (PGNAA) station. 相似文献
65.
Artem V. Matyskin Danas Ridikas V. S. Skuridin Johannes Sterba Georg Steinhauser 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(1):413-418
The subject of this paper is to explore the possibility to obtain 99mTc from activation of 98Mo, using the TRIGA Mark II low flux research reactor (Vienna, Austria). Irradiation of both natural and enriched in 98Mo molybdenum oxides was compared. Aims of this work included the determination of neutron fluxes and 98Mo(n, γ)99Mo reaction effective cross section in the TRIGA Mark II reactor irradiation channels, calculation of 99Mo specific activities, determination of optimal irradiation conditions for the subsequent 99mTc separation from MoO3 targets using concentrating technologies. 相似文献
66.
A series of guanidinium salts 1(C n ) m –4(C n ) m ?X bearing phenyl alkoxybenzoate cores have been synthesised and their mesomorphic properties have been investigated by polarising optical microscopy (POM), differential scanning calorimetry (DSC) and powder X-ray diffraction experiments (small-angle X-ray scattering and wide-angle X-ray scattering). While compounds 1(C12)1?X and 3(C12)1?X with one alkoxy chain showed smectic A (SmA) phases irrespective of the counter ion, compounds 1(C12)2?OTf and 3(C12)2?OTf with two alkoxy chains displayed SmA phases and the corresponding chlorides 1(C12)2?Cl and 3(C12)2?Cl displayed Colh. Guanidinium salts 1(C n )3–4(C n )3?X with three alkoxy chains showed Colh phases. Whereas the use of cyclic guanidinium head groups rather than acyclic ones had only a minor influence on the mesophase properties, melting points were significantly decreased by bent core units instead of linear core units. Replacement of chloride counterions by triflate lead to a further depression of the clearing points and shifted the mesophase towards room temperature. 相似文献
67.
Johannes W. R. Martini Martin Schlather G. Matthias Ullmann 《Journal of mathematical chemistry》2013,51(2):672-695
The decoupled sites representation (DSR) for one type of ligand allows to regard complex overall titration curves as sum of classical Henderson-Hasselbalch (HH) titration curves. In this work we transfer this theoretical approach to molecules with different types of interacting ligands (e.g. protons and electrons), prove the existence of decoupled systems for n 1 and one binding sites for two different ligands, and point out some difficulties and limits of this transfer. A major difference to the DSR for one type of ligand is the loss of uniqueness of the decoupled system. However, all decoupled systems share a unique set of microstate probabilities and each decoupled system corresponds to a certain permutation of these microstate probabilities. Moreover, we show that the titration curve of a certain binding site in the original system can be regarded as linear combination of the titration curves of the individual sites of the decoupled system if the weights of the linear combination are substituted by functions in the activity of the second ligand. In the underlying model with only pairwise interaction, an important observation of our theoretical investigation is the following: Even though the binding sites of ligand L 1 may not interact directly, they can show secondary interaction due to the interaction with the second type of ligand. This means, if the activity of the second ligand is fixed and we regard the 1-dimensional titration curve of an individual binding site for ligand L 1 depending on its activity, we may observe a strong deviation from the classical HH shape in spite of non-interacting sites for ligand L 1. 相似文献
68.
Valentina Ljubomirova Rumyana Djingova Johannes T. van Elteren Marjan Veber Tomasz Kowalkowski Boguslaw Buszewski 《International journal of environmental analytical chemistry》2013,93(7):499-512
A sequential extraction procedure (three-step), proposed by the Standards, Measurements and Testing Programme (formerly BCR) of the European Union, was applied to street dust and spiked soil samples for the determination of PGEs. Analyses were carried out using inductively coupled plasma-mass spectrometry (ICP-MS). The results indicate that up to 5% from Pt, 70% from Pd and 14% from Rh are in mobile forms in street dust. The results for the soil samples spiked with crushed catalytic converter are significantly lower indicating that PGEs are oxidised more efficiently in natural conditions. Additionally Pt and Pd bound to humic acids were investigated. 相似文献
69.
Dr. Chinmoy Mukherjee Kaarina Mäkinen Prof. Dr. Johannes Savolainen Prof. Dr. Reko Leino 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(24):7961-7974
A series of oligovalent carbohydrate assemblies (ranging from mono‐ to pentavalent), derived from three structurally different β‐linked or β‐(1→2)‐linked mannosides, has been chemically synthesized, and the respective compounds have been biologically evaluated in order to investigate their immunostimulatory properties. The Crich methodology for β‐mannosylation was successfully utilized to introduce the β‐linkages, and a click chemistry protocol was utilized to generate the oligovalent derivatives. A convenient protecting group strategy involving the simultaneous use of both p‐methoxybenzyl and benzylidene groups was employed, which allowed a simple and cost‐effective global deprotection step. The immunomodulatory properties of the synthesized multivalent mannosides were evaluated by assessing cytokine production in human white blood cell cultures. The Th2‐type cytokines interleukin‐4 and interleukin‐5 (IL‐4 and IL‐5), the Th1 cytokine interferon‐γ (IFN‐γ), the Treg cytokine IL‐10, and the pro‐inflammatory cytokine tumor necrosis factor (TNF) were included in the screening. A single trivalent acetylated mannobiose derivative was identified as a potent inducer of Treg and Th1 immune response, resulting in strong IL‐10 and moderate IFN‐γ productions dose‐dependently, while inducing no Th2 cytokine response. The immunomodulatory properties of this trivalent mannoside were further studied in vitro in allergen (Bet v)‐stimulated human peripheral blood mononuclear cell cultures of birch pollen allergic subjects. Stimulation with birch pollen induced strong IL‐4 and IL‐5 responses, which could be suppressed by the trivalent acetylated mannobiose derivative. The IL‐10 response was also suppressed, whereas the production of IFN‐γ was strongly enhanced. The results suggest that the identified lead compound has suppressive effects on the Th2‐type allergic inflammatory response and shows potential as a possible lead adjuvant for the specific immunotherapy of allergies. 相似文献
70.
Prof. Dr. Lutz F. Tietze Dr. Ling Ma Johannes R. Reiner Stefan Jackenkroll Sven Heidemann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(26):8610-8614
Blennolide A can be synthesized through an enantioselective domino‐Wacker/carbonylation/methoxylation reaction of 7 a with 96 % ee and an enantioselective Wacker oxidation of 7 b with 89 % ee. Further transformations led to the α,β‐unsaturated ester (E)‐ 17 , which was subjected to a highly selective Michael addition, introducing a methyl group to give 18 a . After a threefold oxidation and an intramolecular acylation, the tetrahydroxanthenone 4 was obtained, which could be transformed into (?)‐blennolide A (ent‐ 1 ) in a few steps. 相似文献