全文获取类型
收费全文 | 323篇 |
免费 | 18篇 |
国内免费 | 7篇 |
专业分类
化学 | 223篇 |
力学 | 12篇 |
数学 | 47篇 |
物理学 | 66篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 15篇 |
2020年 | 7篇 |
2019年 | 12篇 |
2018年 | 19篇 |
2017年 | 11篇 |
2016年 | 29篇 |
2015年 | 8篇 |
2014年 | 26篇 |
2013年 | 55篇 |
2012年 | 32篇 |
2011年 | 18篇 |
2010年 | 16篇 |
2009年 | 13篇 |
2008年 | 18篇 |
2007年 | 8篇 |
2006年 | 5篇 |
2005年 | 9篇 |
2004年 | 3篇 |
2003年 | 3篇 |
2002年 | 5篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有348条查询结果,搜索用时 281 毫秒
341.
342.
Dr. Ceri Hammond Dr. Robert L. Jenkins Dr. Nikolaos Dimitratos Dr. Jose Antonio Lopez‐Sanchez Dr. Mohd Hasbi ab Rahim Dr. Michael M. Forde Adam Thetford Dr. Damien M. Murphy Dr. Henk Hagen Dr. Eric E. Stangland Prof. Jacob M. Moulijn Dr. Stuart H. Taylor Dr. David J. Willock Prof. Graham J. Hutchings 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(49):15557-15557
343.
A sensitive hydrogen peroxide (H2O2) biosensor was developed based on a reduced graphene oxide|carbon ceramic electrode (RGO|CCE) modified with cadmium sulfide‐hemoglobin (CdS‐Hb). The electron transfer kinetics of Hb were promoted due to the synergetic function of RGO and CdS nanoparticles. The transfer coefficient (α) and the heterogeneous electron transfer rate constant (ks) were calculated to be 0.54 and 2.6 s?1, respectively, indicating a great facilitation achieved in the electron transfer between Hb and the electrode surface. The biosensor showed a good linear response to the reduction of H2O2 over the concentration range of 2–240 µM with a detection limit of 0.24 µM (S/N=3) and a sensitivity of 1.056 µA µM?1 cm?2. The high surface coverage of the CdS‐Hb modified RGO|CCE (1.04×10?8 mol cm?2) and a smaller value of the apparent Michaelis? Menten constant (0.24 mM) confirmed excellent loading of Hb and high affinity of the biosensor for hydrogen peroxide. 相似文献
344.
345.
Rahim GhadariFatemeh Hajishaabanha Mojtaba MahyariAhmad Shaabani Hamid Reza Khavasi 《Tetrahedron letters》2012,53(31):4018-4021
A facile and straightforward procedure for the synthesis of spiro-benzo[b]acridine-6,2′-furan derivatives via the reaction between benzo[b]acridine-6,11-dione, electron-deficient acetylenic compounds, and an isocyanide is described. The benzo[b]acridine-6,11-dione is obtained from the reaction between 2-(aminomethyl)aniline and 2-hydroxynaphthalene-1,4-dione via an unexpected reaction pathway. The products are synthesized in medium to high yields and no complicated purification is required. 相似文献
346.
This paper proposes a global cost Malmquist productivity index, new cost Malmquist productivity index, that is circular and that gives a single measure of productivity change. The index is inspired by the global Malmquist productivity index as extended to productivity measurement. Decomposition of the proposed cost Malmquist productivity index is presented. Numerical results are presented for an example taken from the literature to illustrate the proposed algorithm. 相似文献
347.
M. Fill F. Felder M. Rahim A. Khiar H. Zogg 《Applied physics. B, Lasers and optics》2012,109(3):403-406
We present continuously tunable Vertical External Cavity Surface Emitting Lasers (VECSEL) in the mid-infrared. The structure based on IV?CVI semiconductors is epitaxially grown on a Si-substrates. The VECSEL emit one single mode, which is mode hop-free tunable over 50?C100?nm around the center wavelength. In this work, two different devices are presented, emitting at 3.4???m and 3.9???m, respectively. The lasers operate near room temperature with thermoelectric stabilization. They are optically pumped, yielding an output power >10?mWp. The axial symmetric emission beam has a half divergence angle of <3.3°. 相似文献
348.
Hong-Bing Liu Jack R. Davison Rahim Rajwani Gengxiang Zhao Shannon I. Ohlemacher Robert D. OConnor Carole A. Bewley 《Molecules (Basel, Switzerland)》2021,26(23)
Pyrazines (1,4-diazirines) are an important group of natural products that have tremendous monetary value in the food and fragrance industries and can exhibit a wide range of biological effects including antineoplastic, antidiabetic and antibiotic activities. As part of a project investigating the secondary metabolites present in understudied and chemically rich Actinomycetes, we isolated a series of six pyrazines from a soil-derived Lentzea sp. GA3-008, four of which are new. Here we describe the structures of lentzeacins A-E (1, 3, 5 and 6) along with two known analogues (2 and 4) and the porphyrin zincphyrin. The structures were determined by NMR spectroscopy and HR-ESI-MS. The suite of compounds present in Lentzea sp. includes 2,5-disubstituted pyrazines (compounds 2, 4, and 6) together with the new 2,6-disubstituted isomers (compounds 1, 3 and 5), a chemical class that is uncommon. We used long-read Nanopore sequencing to assemble a draft genome sequence of Lentzea sp. which revealed the presence of 40 biosynthetic gene clusters. Analysis of classical di-modular and single module non-ribosomal peptide synthase genes, and cyclic dipeptide synthases narrows down the possibilities for the biosynthesis of the pyrazines present in this strain. 相似文献