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131.
Experimental design for optimization of microwave-assisted extraction of benzodiazepines in human plasma 总被引:1,自引:0,他引:1
P. Fernández C. Vázquez R. A. Lorenzo A. M. Carro I. Álvarez P. Cabarcos 《Analytical and bioanalytical chemistry》2010,397(2):677-685
A simple and fast microwave-assisted-extraction (MAE) method has been evaluated as an alternative to solid-phase extraction
(SPE) for the determination of six benzodiazepines widely prescribed in European countries (alprazolam, bromazepam, diazepam,
lorazepam, lormetazepam and tetrazepam) in human plasma. For MAE optimization a Doehlert experimental design was used with
extraction time, temperature and solvent volume as influential parameters. A desirability function was employed in addition
to the simultaneous optimization of the MAE conditions. The analysis of variance showed that the solvent volume had a positive
influence on the extraction of all the analytes tested, achieving a statistically significant effect. Also, the extraction
time had a statistically significant effect on the extraction of four benzodiazepines. The selected MAE conditions—89 °C,
13 min and 8 mL of chloroform/2-propanol (4:1, v/v)—led to recoveries between 89.8 ± 0.3 and 102.1 ± 5.2% for benzodiazepines
using a high performance liquid chromatography method coupled with diode-array detection. The comparison of MAE and SPE shows
better results for MAE, with a lower number of steps in handling the sample and greater efficiency. The applicability of MAE
was successfully tested in 27 plasma samples from benzodiazepine users. 相似文献
132.
María Álvarez de Morales Lidia Fernández Teresa E. Pérez Miguel A. Piñar 《Numerical Algorithms》2007,45(1-4):153-166
In this paper, we consider bivariate orthogonal polynomials associated with a quasi-definite moment functional which satisfies
a Pearson-type partial differential equation. For these polynomials differential properties are obtained. In particular, we
deduce some structure and orthogonality relations for the successive partial derivatives of the polynomials.
相似文献
133.
B. M. Abramov L. Álvarez-Ruso Yu. A. Borodin S. A. Bulychjov I. A. Dukhovskoy A. I. Khanov A. P. Krutenkova V. V. Kulikov M. A. Matsuk I. A. Radkevich A. I. Sutormin E. N. Turdakina M. J. Vicente Vacas 《Physics of Atomic Nuclei》2002,65(2):229-235
The spectra of fast π + mesons from the π ? A → π + X reaction on A=6Li, 7Li, and 16O nuclei at a primary momentum of p 0=0.72 GeV/c (T 0=0.59 GeV) are measured at emission-angle values in the range ?=0°–14°. The results obtained in this way are compared with experimental data taken in other studies at lower energies and with the results of model calculations. The energy dependence of the cross sections and of shadowing effects is analyzed for the reactions in question that occur on lithium isotopes. 相似文献
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137.
Mesoporous Silica Nanoparticles Decorated with Carbosilane Dendrons as New Non‐viral Oligonucleotide Delivery Carriers 下载免费PDF全文
Ángel Martínez Dr. Elena Fuentes‐Paniagua Dr. Alejandro Baeza Dr. Javier Sánchez‐Nieves Dr. Mónica Cicuéndez Dr. Rafael Gómez Dr. F. Javier de la Mata Dr. Blanca González Prof. María Vallet‐Regí 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(44):15651-15666
A novel nanosystem based on mesoporous silica nanoparticles covered with carbosilane dendrons grafted on the external surface of the nanoparticles is reported. This system is able to transport single‐stranded oligonucleotide into cells, avoiding an electrostatic repulsion between the cell membrane and the negatively charged nucleic acids thanks to the cationic charge provided by the dendron coating under physiological conditions. Moreover, the presence of the highly ordered pore network inside the silica matrix would make possible to allocate other therapeutic agents within the mesopores with the aim of achieving a double delivery. First, carbosilane dendrons of second and third generation possessing ammonium or tertiary amine groups as peripheral functional groups were prepared. Hence, different strategies were tested in order to obtain their suitable grafting on the outer surface of the nanoparticles. As nucleic acid model, a single‐stranded DNA oligonucleotide tagged with a fluorescent Cy3 moiety was used to evaluate the DNA adsorption capacity. The hybrid material functionalised with the third generation of a neutral dendron showed excellent DNA binding properties. Finally, the cytotoxicity as well as the capability to deliver DNA into cells, was tested in vitro by using a human osteoblast‐like cell line, achieving good levels of internalisation of the vector DNA/carbosilane dendron‐functionalised material without affecting the cellular viability. 相似文献
138.
Micelle‐Triggered β‐Hairpin to α‐Helix Transition in a 14‐Residue Peptide from a Choline‐Binding Repeat of the Pneumococcal Autolysin LytA 下载免费PDF全文
Héctor Zamora‐Carreras Dr. Beatriz Maestro Dr. Erik Strandberg Prof. Anne S. Ulrich Dr. Jesús M. Sanz Dr. M. Ángeles Jiménez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(22):8076-8089
Choline‐binding modules (CBMs) have a ββ‐solenoid structure composed of choline‐binding repeats (CBR), which consist of a β‐hairpin followed by a short linker. To find minimal peptides that are able to maintain the CBR native structure and to evaluate their remaining choline‐binding ability, we have analysed the third β‐hairpin of the CBM from the pneumococcal LytA autolysin. Circular dichroism and NMR data reveal that this peptide forms a highly stable native‐like β‐hairpin both in aqueous solution and in the presence of trifluoroethanol, but, strikingly, the peptide structure is a stable amphipathic α‐helix in both zwitterionic (dodecylphosphocholine) and anionic (sodium dodecylsulfate) detergent micelles, as well as in small unilamellar vesicles. This β‐hairpin to α‐helix conversion is reversible. Given that the β‐hairpin and α‐helix differ greatly in the distribution of hydrophobic and hydrophilic side chains, we propose that the amphipathicity is a requirement for a peptide structure to interact and to be stable in micelles or lipid vesicles. To our knowledge, this “chameleonic” behaviour is the only described case of a micelle‐induced structural transition between two ordered peptide structures. 相似文献
139.
Adding a Structural Context to the Deprotometalation and Trans‐Metal Trapping Chemistry of Phenyl‐Substituted Benzotriazole 下载免费PDF全文
Dr. M. Ángeles Fuentes Dr. Alan R. Kennedy Prof. Robert E. Mulvey Dr. John A. Parkinson Dr. Toni Rantanen Dr. Stuart D. Robertson Prof. Victor Snieckus 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(42):14812-14822
Organometallic bases are becoming increasingly complex, because mixing components can lead to bases superior to single‐component bases. To better understand this superiority, it is useful to study metalated intermediate structures prior to quenching. This study is on 1‐phenyl‐1H‐benzotriazole, which was previously deprotonated by an in situ ZnCl2 ? TMEDA/LiTMP (TMEDA=N,N,N′,N′‐tetramethylethylenediamine; TMP=2,2,6,6‐tetramethylpiperidide) mixture and then iodinated. Herein, reaction with LiTMP exposes the deficiency of the single‐component base as the crystalline product obtained was [{4‐R‐1‐(2‐lithiophenyl)‐1H‐benzotriazole ? 3THF}2], [R=2‐C6H4(Ph)NLi], in which ring opening of benzotriazole and N2 extrusion had occurred. Supporting lithiation by adding iBu2Al(TMP) induces trans‐metal trapping, in which C?Li bonds transform into C?Al bonds to stabilise the metalated intermediate. X‐ray diffraction studies revealed homodimeric [(4‐R′‐1‐phenyl‐1H‐benzotriazole)2], [R′=(iBu)2Al(μ‐TMP)Li], and its heterodimeric isomer [(4‐R′‐1‐phenyl‐1H‐benzotriazole){2‐R′‐1‐phenyl‐1H‐benzotriazole}], whose structure and slow conformational dynamics were probed by solution NMR spectroscopy. 相似文献
140.