全文获取类型
收费全文 | 1191篇 |
免费 | 44篇 |
国内免费 | 3篇 |
专业分类
化学 | 733篇 |
晶体学 | 25篇 |
力学 | 48篇 |
数学 | 210篇 |
物理学 | 222篇 |
出版年
2024年 | 2篇 |
2023年 | 6篇 |
2022年 | 24篇 |
2021年 | 42篇 |
2020年 | 38篇 |
2019年 | 34篇 |
2018年 | 29篇 |
2017年 | 49篇 |
2016年 | 53篇 |
2015年 | 52篇 |
2014年 | 46篇 |
2013年 | 113篇 |
2012年 | 102篇 |
2011年 | 104篇 |
2010年 | 77篇 |
2009年 | 64篇 |
2008年 | 73篇 |
2007年 | 64篇 |
2006年 | 38篇 |
2005年 | 42篇 |
2004年 | 49篇 |
2003年 | 25篇 |
2002年 | 24篇 |
2001年 | 8篇 |
2000年 | 13篇 |
1999年 | 5篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 8篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1972年 | 2篇 |
1907年 | 1篇 |
排序方式: 共有1238条查询结果,搜索用时 0 毫秒
931.
An allele‐specific voltammetric genoassay for the detection of allele‐specific toll‐like receptor‐2 gene arg753gln polymorphism (TLR‐2) from polymerase chain reaction (PCR) amplified real samples was described in this study. Meldola blue (MDB), an intercalator molecule, was used as hybridization label. The wild‐type and mutant type oligonucleotide probes were immobilized onto disposable graphite electrode surfaces by covalent attachment method. The extent of hybridization between probe and target sequences was determined by using differential pulse voltammetry (DPV). As a result of the interaction between MDB and DNA at electrode surface, the MDB signal observed from probe sequence before hybridization and after hybridization with MM sequence is lower than that observed after hybridization with complementary sequence. The differences between the MDB reduction peaks obtained from probe modified, hybrid modified and MM modified electrode were used to detect TLR‐2 from PCR amplified real samples. The discrimination of homozygous and heterozygous alleles was also established by comparing the peak currents of MDB reduction signals. Numerous factors affecting the target hybridization and indicator binding reactions are optimized to maximize the sensitivity. 相似文献
932.
Serkan Sayin Elif Ozyilmaz Mehmet Oguz Rüstem Yusufoglu 《Supramolecular chemistry》2020,32(5):334-344
ABSTRACT In this study, we first used water-soluble iron oxide nanoparticles for Candida rugosa lipase immobilisation. Moreover, two new complexation phenomena of the prepared water-soluble Fe3O4 nanoparticles with an enzyme might address interesting results in terms of enzyme activity and stability in typical enzymatic reactions. The catalytic activity on pH and temperature dependence, and reusability of the immobilised lipases ( p-SCX4-NP-E and p-SCX8-NP-E) were also investigated with the hydrolysis reaction of p-nitrophenyl palmitate (p-NPP). The results show that the highest catalytic affinities for p-SCX4-NP-E and p-SCX8-NP-E were obtained at pH 5.0 and pH 7.0, respectively. 相似文献
933.
Bilgin MD Elçin AE Elçin YM 《Journal of photochemistry and photobiology. B, Biology》2005,80(2):107-114
Photodynamic therapy (PDT) is a new treatment modality that uses porphyrin derivatives and visible light, especially for the treatment of cancer. However, PDT with certain photosensitisers can cause prolonged skin photosensitization. This is particularly true for Photofrin II (Photofrin)-mediated PDT where patients are required to avoid direct exposure to sunlight for a period of 4-6 weeks. This is the only long-term adverse reaction to the drug. Recent studies have shown that topical copper treatment avoids this type of inflammatory reaction. In this study, we have tested the efficiency of the liposomal formulation of copper palmitate on porphyrin-photosensitized rats. Initially, adult male Sprague-Dawley rats were rendered photosensitive either by administration of Photofrin or aminolevulinic acid (ALA), a precursor of protoporphyrin IX (PpIX). Prior to this, their dorsal skin was shaved and treated topically with a cream consisting of either empty or copper palmitate-encapsulated liposomal formulation. After being kept in a dimmed light environment, the rats were exposed to visible light, and inflammatory responses were inspected. Histological studies revealed that no inflammatory cells were present at the skin sites treated with liposomal cream containing copper palmitate in the Photofrin-sensitized group while no reduction in the number of inflammatory cells was observed at the skin samples treated with the empty liposomes. In conclusion, the data demonstrate the significant protective effect of topically-applied liposome-encapsulated copper palmitate against both Photofrin and ALA-induced PpIX photosensitivity. 相似文献
934.
Development of a microfabricated cytometry platform for characterization and sorting of individual leukocytes 总被引:5,自引:0,他引:5
Organizing leukocytes into high-density arrays makes these cells amenable to rapid optical characterization and subsequent sorting, pointing to clinical and basic science applications. The present paper describes development of a cytometry platform for creating high-density leukocyte arrays and demonstrates retrieval of single cells from the array. Poly(ethylene glycol)(PEG) photolithography was employed to fabricate arrays of microwells composed of PEG hydrogel walls and glass attachment pads 20 microm x 20 microm and 15 microm x 15 microm in size. PEG micropatterned glass surfaces were further modified with cell-adhesive ligands, poly-L-lysine, anti-CD5 and anti-CD19 antibodies, in order to engineer specific cell-surface interactions within the individual wells. Localization of the fluorescently-labeled proteins in the glass attachment pads of PEG microwells was visualized by fluorescence microscopy. Glass slides micropatterned with PEG and cell-adhesive ligands were exposed to T-lymphocytes for 30 min. These anchorage-independent cells became selectively captured in the ligand-modified microwells forming high-density cell arrays. Cell occupancy in the microwells was found to be antibody-dependent, reaching 94.6 +/- 2.3% for microwells decorated with T-cell specific anti-CD5 antibodies. Laser capture microdissection (LCM) was investigated as a method for sorting cells from the array and retrieval of single selected cells was demonstrated. 相似文献
935.
Our efforts toward the development of the synthesis of a novel type of receptor ligand and its tetrasubstituted phthalocyanines, 2,9,16,23-tetrakis(6-hydroxyhexylsulfanyl) phthalocyanine, M[Pc(S–C6H13OH)4] (M = Zn(II), Cu(II), Co(II)), bearing sulfur and oxygen donor atoms on the periphery together with hexyl moieties, have been carried out together with spectroscopic and electrochemical characterization. The newly synthesized functional phthalocyanines were soluble in MeOH, EtOH, THF, DMF, CNP (α-chloronapthalene), DMSO and quinoline, and less soluble in i-PrOH and CH3CN. Cation binding abilities of the functional phthalocyanines with Ag+, Pd2+, Hg2+ and Cd2+, resulting in the formation of polynuclear phthalocyanine complexes, were evaluated by UV–Vis spectroscopic techniques. The spectroscopic properties of the complexes were affected strongly by the electron-donating sulfanyl units on the periphery. The cyclic voltammetry of the complexes were examined on a platinum electrode in DMSO. The new synthesized compounds have been characterized by elemental analysis, FTIR, 1H and 13C NMR, MS (ESI and MALDI-TOF) and UV–Vis spectral data. 相似文献
936.
Esref?TasEmail author Mehmet?Aslanoglu Ahmet?Kilic Zeliha?Kara 《Transition Metal Chemistry》2005,30(6):758-764
Three novel vic-dioximes: cyclohexylamine-p-tolylglyoxime (L1H2), t-butylamine-p-tolylglyoxime (L2H2) and sec-butylamine-p-tolylglyoxime (L3H2) were prepared by the reaction of anti-p-tolylchloroglyoxime with cyclohexylamine, t-butylamine and sec-butylamine in absolute THF. The detection of H-bonding in all of the Ni(II) complexes by i.r. revealed the square-planar MN4 coordination of mononuclear complexes. MN4 coordination of the [(L1H)2Ni] complex was also determined by 1H and 13C-n.m.r spectroscopy. Mononuclear complexes with a 1:2 metal-ligand ratio were prepared using Ni(II) salts. All Ni(II) complexes are insoluble in common solvents. The ligands and complexes were characterized by elemental analyses, FT-i.r., u.v.–vis., 1H and 13C-n.m.r. spectra, magnetic susceptibility measurements, thermogravimetric analyses (t.g.a.) and cyclic voltammetry. 相似文献
937.
İhsan Çalış Ayşegül Güvenç Metin Armağan Mehmet Koyuncu Charlotte H. Gotfredsen Søren R. Jensen 《Helvetica chimica acta》2007,90(8):1461-1466
From the aerial parts of Eremostachys moluccelloides Bunge , a new iridoid glucoside, lamalbidic acid ( 7 ), was isolated as its choline salt 7a together with six known iridoid glucosides, 5‐deoxysesamoside ( 1 ), 6β‐hydroxy‐7‐epiloganin ( 2 ), lamalbide ( 3 ), shanzhiside methyl ester ( 4 ), sesamoside ( 5 ), and 5‐deoxypulchelloside I ( 6 ). The structures of 7a and 7 (obtained from 7a ) were elucidated by spectroscopic (UV, IR, 1D‐ and 2D‐NMR, and ESI‐MS) methods. 相似文献
938.
939.
Elucidating the Reactivity of Vicinal Dicarbenoids: From Lewis Adduct Formation to B−C Bond Activation 下载免费PDF全文
Hauke Kelch Stephanie Kachel Dr. Mehmet Ali Celik Dr. Marius Schäfer Dr. Benedikt Wennemann Dr. Krzysztof Radacki Dr. Alex R. Petrov Prof. Dr. Matthias Tamm Prof. Dr. Holger Braunschweig 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(39):13815-13818
The reactivity of the diaminoacetylene Pip‐C≡C‐Pip (Pip=piperidyl=NC5H10) towards phenyldichloro‐ and triphenylborane is presented. In the case of the less Lewis acidic PhBCl2, the first example of a double Lewis adduct of a vicinal dicarbenoid is reported. For the more Lewis acidic triphenylborane, coordination to the bifunctional carbene leads to a mild B?C bond activation, resulting in a syn‐1,2‐carboboration. Ensuing cis/trans isomerization yields a novel ethylene‐bridged frustrated Lewis pair (FLP). The compounds were characterized using multinuclear NMR spectroscopy, structural analysis, and mass spectrometry. Reactivity studies of both isomers with the N‐heterocyclic carbene 1,3‐dimethylimidazol‐2‐ylidene (IMe) aided in elucidating the proposed isomerization pathway. DFT calculations were carried out to elucidate the reaction mechanism. The rather low free energy of activation is consistent with the observation that the reaction proceeds smoothly at room temperature. 相似文献
940.
This study aimed to review recent chromatographic methods for quantifying and identifying components released from dental composites. Resin-based dental restorative materials are extensively used in dentistry today. Although composite materials are known to be highly stable structures, they are susceptible to degradation because of the incomplete polymerization. Several components may be released from resin composite restorations into the oral environment. The elution of components from composite resins may affect the biocompatibility of the restorations. Therefore, it is essential to understand the nature and quantity of substances that are segregated into the oral cavity. 相似文献