全文获取类型
收费全文 | 496篇 |
免费 | 18篇 |
国内免费 | 6篇 |
专业分类
化学 | 294篇 |
晶体学 | 3篇 |
力学 | 5篇 |
数学 | 93篇 |
物理学 | 125篇 |
出版年
2023年 | 7篇 |
2022年 | 7篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 8篇 |
2018年 | 7篇 |
2016年 | 13篇 |
2015年 | 7篇 |
2014年 | 11篇 |
2013年 | 24篇 |
2012年 | 21篇 |
2011年 | 29篇 |
2010年 | 18篇 |
2009年 | 12篇 |
2008年 | 29篇 |
2007年 | 31篇 |
2006年 | 34篇 |
2005年 | 34篇 |
2004年 | 22篇 |
2003年 | 24篇 |
2002年 | 14篇 |
2001年 | 3篇 |
2000年 | 16篇 |
1999年 | 7篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 7篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1968年 | 2篇 |
1925年 | 2篇 |
排序方式: 共有520条查询结果,搜索用时 406 毫秒
71.
Neal G. Anderson 《Physics letters. A》2008,372(34):5552-5555
The physical cost of information erasure is considered within a new approach that regards erasure as loss of correlation between the state of an erasable quantum system and that of an enduring “referent” system holding classical information. A physical model of information erasure built on this referential picture is described in detail, and lower bounds on entropic and energetic costs are obtained from quantum dynamics and entropic inequalities alone. 相似文献
72.
73.
Neal P. Mankad 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(17):5822-5829
An emerging area of homogeneous catalysis is the use of catalysts featuring two closely associated metal sites. This approach complements the traditional focus on single‐site catalysts and makes available new parameters with which to optimize catalytic behavior. Single‐site catalysts are optimized through changing 1) the identity of the metal, and 2) the steric and electronic properties of the ligands. Bimetallic catalysts introduce new optimization parameters such as 3) catalyst nuclearity (mononuclear vs. binuclear), and 4) bimetallic pairing (relative compatibility of two metal sites). In order to harness these new optimization parameters in developing systems, it is necessary to first understand the origin of bimetallic selectivity effects that already have been documented. This Concept article highlights bimetallic effects on the chemo‐, regio‐, and stereoselectivity of catalytic transformations, using selected case studies from the recent literature as illustrative examples. 相似文献
74.
75.
Alexandre S. Miranda Paula M. Marcos Jos R. Ascenso M. Paula Robalo Vasco D. B. Bonifcio Mrio N. Berberan-Santos Neal Hickey Silvano Geremia 《Molecules (Basel, Switzerland)》2021,26(6)
Direct O-alkylation of p-tert-butyldihomooxacalix[4]arene (1) with N-(bromopropyl)- or N-(bromoethyl)phthalimides and K2CO3 in acetonitrile was conducted under conventional heating (reflux) and using microwave irradiation and ball milling methodologies. The reactions afforded mono- and mainly distal di-substituted derivatives in the cone conformation, in a total of eight compounds. They were isolated by column chromatography, and their conformations and the substitution patterns were established by NMR spectroscopy (1H, 13C, COSY and NOESY experiments). The X-ray structures of four dihomooxacalix[4]arene phthalimide derivatives (2a, 3a, 3b and 5a) are reported, as well as their photophysical properties. The microwave (MW)-assisted alkylations drastically reduced the reaction times (from days to less than 45 min) and produced higher yields of both 1,3-di-substituted phthalimides (3a and 6a) with higher selectivity. Ball milling did not reveal to be a good method for this kind of reaction. 相似文献
76.
77.
Christopher P. Gordon Neal Dalton Nicholas Vandegraaff John Deadman David I. Rhodes Jonathan A. Coates Stephen G. Pyne Renate Griffith John B. Bremner Paul A. Keller 《Tetrahedron》2018,74(12):1253-1268
As of mid-2017, only one structure of the human immunodeficiency virus (HIV) integrase core domain co-crystallised with an active site inhibitor was reported. In this structure (1QS4), integrase is complexed with a diketo-acid based strand-transfer inhibitor (INSTI). This structure has been a preferred platform for the structure-based design of INSTIs despite concerns relating to structural irregularities arising from crystallographic packing effects. A survey of the current pool of 297 reported integrase catalytic core structures indicated that the anatomy of the active site in the complex structure 1QS4 exhibits subtle variations relative to all other structures examined. Consequently, the 1QS4 structure was employed for docking studies. From the docking of twenty-seven allyltyrosine analogues, a 3-point inhibitor binding motif required for activity was established and successfully utilised in the development of a tripeptide displaying an EC50 value of 10 ± 5 μM in HIV infected human T-cells. Additional docking of “in-house” compound libraries unearthed a methyl ester based nitrile derivative displaying an IC50 value of 0.5 μM in a combined 3′-processing and strand-transfer assay. 相似文献
78.
Yinliang F. Hsieh Neal Gordon Fred Regnier Noubar Afeyan Stephen A. Martin George J. Vella 《Molecular diversity》1997,2(4):189-196
Summary The synthesis of structural analogs and the process of drug discovery have evolved dramatically through recent advances in solid-phase synthesis reagents and automated screening systems. As molecular diversity strategies emerge, the need for automated target-based selection of lead candidates becomes equally important. Multidimensional automated chromatographic techniques coupled to electrospray ionization mass spectrometry facilitate the selection process and provide maximum characterization information in a single screening run. The capture of tightly bound affinity leads by target biomolecules, followed by subsequent release and high-resolution separation with sensitive detection, significantly reduces the time required to identify and characterize lead compounds. This automated multidimensional chromatographic approach coupled with mass spectrometry, Selectronics, was used with several organic and natural libraries to demonstrate an automated target-based screening technique to select for high-affinity binders as potential lead compounds.Abbreviations ESI
electrospray ionization
- HPLC
high-performance liquid chromatography
- HTS
high-throughput screening
- ESI-TOF
electrospray ionization time-of-flight
- SAR
structure-activity relationship 相似文献
79.
Stephen J. Sweetman Charles D. Immanuel Tahir I. Malik Simon Emmett Neal Williams 《大分子反应工程》2008,2(5):382-397
A sensitivity study of particle size distribution (PSD) and molecular weight distribution (MWD) responses to perturbations in initiator, surfactant, monomer and chain transfer agent in a semi‐batch emulsion polymerisation is presented. The objective is to provide a systematic study on the ability to simultaneously control both PSD and MWD, towards inferential control of end‐use product properties. This would lead towards identification of the practical feasible regions of operability. All inputs appeared to have an intrinsic and simultaneous influence on end‐time PSD and MWD. Trends shown in experimental results have been explained in a mechanistic sense and also compared to simulation results from a combined PSD/MWD population balance model. The preliminary comparison between experiment and simulation highlights areas to be focussed on with respect to model improvement.
80.
[Ph2BP(tBu)2]Cu-L complexes react with diazoalkanes to generate structurally unusual eta1-diazoalkane adducts, a terminal carbene, and an eta1-azine adduct. 相似文献