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991.
Hong Wu Xuecui WangBing Liu Yueling LiuShanshan Li Jusheng LuJiuying Tian Wenfeng ZhaoZonghui Yang 《Spectrochimica Acta Part B: Atomic Spectroscopy》2011,66(1):74-80
A new method was developed for the simultaneous speciation of inorganic arsenic and antimony in water by on-line solid-phase extraction coupled with hydride generation-double channel atomic fluorescence spectrometry (HG-DC-AFS). The speciation scheme involved the on-line formation and retention of the ammonium pyrrolidine dithiocarbamate complexes of As(III) and Sb(III) on a single-walled carbon nanotubes packed micro-column, followed by on-line elution and simultaneous detection of As(III) and Sb(III) by HG-DC-AFS; the total As and total Sb were determined by the same protocol after As(V) and Sb(V) were reduced by thiourea, with As(V) and Sb(V) concentrations obtained by subtraction. Various experimental parameters affecting the on-line solid-phase extraction and determination of the analytes species have been investigated in detail. With 180 s preconcentration time, the enrichment factors were found to be 25.4 for As(III) and 24.6 for Sb(III), with the limits of detection (LODs) of 3.8 ng L− 1 for As(III) and 2.1 ng L− 1 for Sb(III). The precisions (RSD) for five replicate measurements of 0.5 μg L−1 of As(III) and 0.2 μg L−1 of Sb(III) were 4.2 and 4.8%, respectively. The developed method was validated by the analysis of standard reference materials (NIST SRM 1640a), and was applied to the speciation of inorganic As and Sb in natural water samples. 相似文献
992.
采用水热反应合成了有机-无机杂化的Keggin型配合物(C12H9N2)3[PMo12O40],并通过X-射线单晶衍射对其结构进行了分析。该配合物为正交晶系P212121空间群,晶胞参数为a=1.20800(1)nm,b=2.10108(4)nm,c=2.24234(5)nm。配合物包含了孤立的Keggin型[PMo1... 相似文献
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997.
Protein–protein interactions, particularly weak and transient ones, are often mediated by peptide recognition domains. Characterizing
the interaction interface of domain–peptide complexes and analyzing binding specificity for modular domains are critical for
deciphering protein–protein interaction networks. In this article, we report the successful use of an integrated computational
protocol to dissect the energetic profile and structural basis of peptide binding to third PDZ domain (PDZ3) from the PSD-95
protein. This protocol employs rigorous quantum mechanics/molecular mechanics (QM/MM), semi-empirical Poisson–Boltzmann/surface
area (PB/SA), and empirical conformational free energy analysis (CFEA) to quantitatively describe and decompose systematic
energy changes arising from, respectively, noncovalent interaction, desolvation effect, and conformational entropy loss associated
with the formation of 30 affinity-known PDZ3–peptide complexes. We show that the QM/MM-, PB/SA-, and CFEA-derived energy components
can work together fairly well in reproducing experimentally measured affinity after a linearly weighting treatment, albeit
they are not compatible with each other directly. We also demonstrate that: (1) noncovalent interaction and desolvation effect
donate, respectively, stability and specificity to complex architecture, while entropy loss contributes modestly to binding;
(2) P0 and P−2 of peptide ligand are the most important positions for determining both the stability and specificity of the PDZ3–peptide
complex, P−1 and P−3 can confer substantial stability (but not specificity) for the complex, and N-terminal P−4 and P−5 have only a very limited effect on binding. 相似文献
998.
Tian F Cziferszky M Jiao D Wahlström K Geng J Scherman OA 《Langmuir : the ACS journal of surfaces and colloids》2011,27(4):1387-1390
We demonstrate a supramolecular peptide separation approach by the selective immobilization of peptides bearing an N-terminal tryptophan onto a CB[8]-modified gold substrate, followed by electrochemical release. The CB[8]-stabilized heteroternary complexes were characterized by (1)H NMR, ESI-MS, UV/vis, and fluorescence spectroscopy and cyclic voltammetry. Micropatterned CB[8]-modified gold substrates were found to trap only the recognizable N-tryptophan-containing peptides from a peptide mixture that could be visualized as green peptide arrays under fluorescence microscopy. Subsequently, the bound peptides were released from the modified substrates by the controlled single-electron reduction of viologen. The fully reversible trap-and-release process was repeated for 13 cycles, and the cumulative release profile of the dye-peptide conjugate was monitored by fluorescence spectroscopy, indicating that no degradation occurred. 相似文献
999.
Cao D Wu YP Fu ZF Tian Y Li CJ Gao CY Chen ZL Feng XZ 《Colloids and surfaces. B, Biointerfaces》2011,84(1):26-34
Nanostructured biocomposite scaffolds of poly(l-lactide) (PLLA) blended with collagen (coll) or hydroxyapatite (HA), or both for tissue engineering application, were fabricated by electrospinning. The electrospun scaffolds were characterized for the morphology, chemical and tensile properties by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), water contact angle (WCA), Fourier transform infrared (FTIR) measurement, and tensile testing. Electrospun biocomposite scaffolds of PLLA and collagen or (and) HA in the diameter range of 200-700 nm mimic the nanoscale structure of the extracellular matrix (ECM) with a well-interconnection pore network structure. The presence of collagen in the scaffolds increased their hydrophility, and enhanced cell attachment and proliferation, while HA improved the tensile properties of the scaffolds. The biocompatibility of the electrospun scaffolds and the viability of contacting cells were evaluated by 4',6-diamidino-2-phenylindole dihydrochloride (DAPI) nuclear staining and by fluorescein diacetate (FDA) and propidium iodide (PI) double staining methods. The results support the conclusion that 293T cells grew well on composite scaffolds. Compared with pure PLLA scaffolds a greater density of viable cells was seen on the composites, especially the PLLA/HA/collagen scaffolds. 相似文献
1000.
Hao XuHua Tian Liangyu Zheng Qingwen LiuLi Wang Suoqin Zhang 《Tetrahedron letters》2011,52(22):2873-2875
A novel and efficient microwave-assisted one-step reaction was developed to synthesize chiral N-sulfonylaziridines by the reaction of different chiral amino alcohols and sulfonic chlorides. The newly developed microwave synthetic method has the advantage of reducing the reaction time from 24 to 0.5 h with improved yields (84-93%) and minimizing by-products. 相似文献