全文获取类型
收费全文 | 714篇 |
免费 | 23篇 |
国内免费 | 2篇 |
专业分类
化学 | 524篇 |
晶体学 | 9篇 |
力学 | 12篇 |
数学 | 86篇 |
物理学 | 108篇 |
出版年
2023年 | 9篇 |
2022年 | 5篇 |
2021年 | 18篇 |
2020年 | 13篇 |
2019年 | 9篇 |
2018年 | 6篇 |
2017年 | 3篇 |
2016年 | 19篇 |
2015年 | 16篇 |
2014年 | 20篇 |
2013年 | 38篇 |
2012年 | 55篇 |
2011年 | 61篇 |
2010年 | 20篇 |
2009年 | 33篇 |
2008年 | 56篇 |
2007年 | 42篇 |
2006年 | 46篇 |
2005年 | 26篇 |
2004年 | 28篇 |
2003年 | 16篇 |
2002年 | 27篇 |
2001年 | 21篇 |
2000年 | 15篇 |
1999年 | 10篇 |
1998年 | 6篇 |
1997年 | 11篇 |
1996年 | 10篇 |
1995年 | 4篇 |
1994年 | 8篇 |
1993年 | 7篇 |
1992年 | 10篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 8篇 |
1988年 | 3篇 |
1985年 | 11篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1973年 | 5篇 |
1971年 | 3篇 |
1967年 | 1篇 |
排序方式: 共有739条查询结果,搜索用时 15 毫秒
61.
Min Kyong Moon Min Kim Sung Soo Chung Hyun Joo Lee Sung Hee Koh Peter Svovoda Myung Hee Jung Young Min Cho Young Joo Park Sung Hee Choi Hak Chul Jang Kyong Soo Park Hong Kyu Lee 《Experimental & molecular medicine》2010,42(5):345-352
An association between inflammatory processes and the pathogenesis of insulin resistance has been increasingly suggested. The IκB kinase-β (IKK-β)/ nuclear factor-κB (NF-κB) pathway is a molecular mediator of insulin resistance. S-Adenosyl-L-methionine (SAM) has both antioxidative and anti-inflammatory properties. We investigated the effects of SAM on the glucose transport and insulin signaling impaired by the tumor necrosis factor α (TNFα) in 3T3-L1 adipocytes. SAM partially reversed the basal and insulin stimulated glucose transport, which was impaired by TNFα. The TNFα-induced suppression of the tyrosine phosphorylation of the insulin receptor substrate-1 (IRS-1) and Akt in 3T3-L1 adipocytes was also reversed by SAM. In addition, SAM significantly attenuated the TNFα-induced degradation of IκB-α and NF-κB activation. Interestingly, SAM directly inhibited the kinase activity of IKK-β in vitro. These results suggest that SAM can alleviate TNFα mediated-insulin resistance by inhibiting the IKK-β/NF-κB pathway and thus can have a beneficial role in the treatment of type 2 diabetes mellitus. 相似文献
62.
In chromatography-based metabonomic research, retention time (RT) alignment of chromatographic peaks poses a challenge for the accurate profiling of biomarkers. Although a number of RT alignment software has been reported, the performance of these software packages have not been comprehensively evaluated. This study aimed to evaluate the RT alignment accuracy of publicly available and commercial RT alignment software. Two gas chromatography/mass spectrometry (GC/MS) datasets acquired from a mixture of standard metabolites and human bladder cancer urine samples, were used to assess three publicly available software packages, MetAlign, MZmine and TagFinder, and two commercial applications comprising the Calibration feature and Statistical Compare of ChromaTOF software. The overall RT alignment accuracies in aligning standard compounds mixture were 93, 92, 74, 73 and 42% for Calibration feature, MZmine, MetAlign, Statistical Compare and TagFinder, respectively. Additionally, unique trends were observed for the individual software with regards to the different experimental conditions related to extent and direction of RT shifts. Conflicting performance was observed for human urine samples suggesting that RT misalignments still occurred despite the use of RT alignment software. While RT alignment remains an inevitable step in data preprocessing, metabonomic researchers are recommended to perform manual check on the RT alignment of important biomarkers as part of their validation process. 相似文献
63.
Dongmin Gang Yu-tin Huang Eunkyung Koh Sangmin Lee Arthur E. Lipstein 《Journal of High Energy Physics》2011,2011(3):116
We propose a recursion relation for tree-level scattering amplitudes in three-dimensional Chern-Simons-matter theories. The recursion relation involves a complex deformation of momenta which generalizes the BCFW-deformation used in higher dimensions. Using background field methods, we show that all tree-level superamplitudes of the ABJM theory vanish for large deformations, establishing the validity of the recursion formula. Furthermore, we use the recursion relation to compute six-point and eight-point component amplitudes and match them with independent computations based on Feynman diagrams or the Grassmannian integral formula. As an application of the recursion relation, we prove that all tree-level amplitudes of the ABJM theory have dual superconformal symmetry. Using generalized unitarity methods, we extend this symmetry to the cut-constructible parts of the loop amplitudes. 相似文献
64.
Park J Lee G Wolff-Fabris F Koh YY Eom MJ Kim YK Farhan MA Jo YJ Kim C Shim JH Kim JS 《Physical review letters》2011,107(12):126402
We report the observation of highly anisotropic Dirac fermions in a Bi square net of SrMnBi(2), based on a first-principles calculation, angle-resolved photoemission spectroscopy, and quantum oscillations for high-quality single crystals. We found that the Dirac dispersion is generally induced in the (SrBi)(+) layer containing a double-sized Bi square net. In contrast to the commonly observed isotropic Dirac cone, the Dirac cone in SrMnBi(2) is highly anisotropic with a large momentum-dependent disparity of Fermi velocities of ~8. These findings demonstrate that a Bi square net, a common building block of various layered pnictides, provides a new platform that hosts highly anisotropic Dirac fermions. 相似文献
65.
Jung Tae ParkJoo Hwan Koh Jin Ah SeoYong Soo Cho Jong Hak Kim 《Applied Surface Science》2011,257(20):8301-8306
We report on the novel ternary hybrid materials consisting of semiconductor (TiO2), metal (Ag) and polymer (poly(oxyethylene methacrylate) (POEM)). First, a hydrophilic polymer, i.e. POEM, was grafted from TiO2 nanoparticles via the surface-initiated atom transfer radical polymerization (ATRP) technique. These TiO2-POEM brush nanoparticles were used to template the formation of Ag nanoparticles by introduction of a AgCF3SO3 precursor and a NaBH4 aqueous solution for reduction process. Successful grafting of polymeric chains from the surface of TiO2 nanoparticles and the in situ formation of Ag nanoparticles within the polymeric chains were confirmed using transmission electron microscopy (TEM), UV-vis spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). FT-IR spectroscopy also revealed the specific interaction of Ag nanoparticles with the CO groups of POEM brushes. This study presents a simple route for the in situ synthesis of both metal and polymer confined within the semiconductor, producing ternary hybrid inorganic-organic nanomaterials. 相似文献
66.
67.
Kim Sang Woong Hong Chang Yong Koh Jong Sung Lee Eun Ju Lee Koo 《Molecular diversity》1997,3(2):133-136
Using solid phase synthesis, a library has been constructed of benzamidine-derived sulfonamides which have strong inhibitory
activity against blood coagulant thrombin. The library compounds were obtained in good yield and high purity.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
68.
A colorimetric sensor has been developed in this work to sensitively detect α-glucosidase activity and screen α-glucosidase inhibitors (AGIs) utilizing unmodified gold nanoparticles (AuNPs). The sensing strategy is based on triple-catalytic reaction triggered by α-glucosidase. In the presence of α-glucosidase, aggregation of AuNPs is prohibited due to the oxidation of cysteine to cystine in the system. However, with addition of AGIs, cysteine induced aggregation of AuNPs occurs. Thus, a new method for α-glucosidase activity detection and AGIs screening is developed by measuring the UV–vis absorption or visually distinguishing. A well linear relation is presented in a range of 0.0025–0.05 U mL−1. The detection limit is found to be 0.001 U mL−1 for α-glucosidase assay, which is one order of magnitude lower than other reports. The IC50 values of four kinds of inhibitors observed with this method are in accordance with other reports. The using of unmodified AuNPs in this work avoids the complicated and time-consuming modification procedure. This simple and efficient colorimetric method can also be extended to other enzymes assays. 相似文献
69.
We herein report a robust and efficient synthetic route to highly functionalized enantiopure 1,2,3,4-tetrahydroisoquinolines (THIQs) from Garner aldehyde. We utilized the inherent chirality of Garner aldehyde through 1,2- and 1,3-/1,4-asymmetric inductions iteratively to obtain 1,2,3,4-tetrasubstitued THIQs using rigid and isolable bridged oxazolidines without any external chiral sources. All possible stereoisomers of bridged oxazoliodines were efficiently synthesized from L- and D-Garner aldehydes and transformed into fully functionalized THIQs via diastereoselective ring opening with various nucleophiles in the presence of Yb(OTf)(3). This methodology furnished four out of eight possible diastereomers of 1,2,3,4-tetrasubstituted THIQs despite the electronic nature of substituents on the aryl rings. Finally, the enantioselective synthesis of 2-azapodophyllotoxin was achieved with an overall yield of 35.4% (eight steps) from D-Garner aldehyde using this synthetic route. 相似文献
70.
Park TH Hickman AJ Koh K Martin S Wong-Foy AG Sanford MS Matzger AJ 《Journal of the American Chemical Society》2011,133(50):20138-20141
High reversibility during crystallization leads to relatively defect-free crystals through repair of nonperiodic inclusions, including those derived from impurities. Microporous coordination polymers (MCPs) can achieve a high level of crystallinity through a related mechanism whereby coordination defects are repaired, leading to single crystals. In this work, we discovered and exploited the fact that this process is far from perfect for MCPs and that a minority ligand that is coordinatively identical to but distinct in shape from the majority linker can be inserted into the framework, resulting in defects. The reaction of Zn(II) with 1,4-benzenedicarboxylic acid (H(2)BDC) in the presence of small amounts of 1,3,5-tris(4-carboxyphenyl)benzene (H(3)BTB) leads to a new crystalline material, MOF-5(O(h)), that is nearly identical to MOF-5 but has an octahedral morphology and a number of defect sites that are uniquely functionalized with dangling carboxylates. The reaction with Pd(OAc)(2) impregnates the metal ions, creating a heterogeneous catalyst with ultrahigh surface area. The Pd(II)-catalyzed phenylation of naphthalene within Pd-impregnated MOF-5(O(h)) demonstrates the potential utility of an MCP framework for modulating the reactivity and selectivity of such transformations. Furthermore, this novel synthetic approach can be applied to different MCPs and will provide scaffolds functionalized with catalytically active metal species. 相似文献