全文获取类型
收费全文 | 282篇 |
免费 | 9篇 |
专业分类
化学 | 193篇 |
晶体学 | 5篇 |
力学 | 2篇 |
数学 | 5篇 |
物理学 | 86篇 |
出版年
2022年 | 1篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 3篇 |
2015年 | 1篇 |
2014年 | 7篇 |
2013年 | 11篇 |
2012年 | 24篇 |
2011年 | 16篇 |
2010年 | 9篇 |
2009年 | 6篇 |
2008年 | 22篇 |
2007年 | 15篇 |
2006年 | 13篇 |
2005年 | 18篇 |
2004年 | 18篇 |
2003年 | 7篇 |
2002年 | 10篇 |
2001年 | 13篇 |
2000年 | 9篇 |
1999年 | 5篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 9篇 |
1994年 | 5篇 |
1993年 | 14篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1970年 | 1篇 |
1967年 | 1篇 |
1966年 | 2篇 |
排序方式: 共有291条查询结果,搜索用时 15 毫秒
91.
We report on a study of the proton induced hyperon production reactions. We discuss the theoretical efforts made towards understanding
the existing data and the uncertainties involved in the calculations. Our recent calculations of the missing mass spectra
for the pp → K
+ Λp reaction which involve a proper coupled channel treatment of the final state Λp interaction are presented. Significant differences in the results using different models of the hyperon-nucleon interaction
are found. 相似文献
92.
93.
Templated Phospholipid Bilayers: Mosaic Interdigitated Structure in Nanoparticle‐Templated Phospholipid Bilayer Supports Partial Lipidation of Apolipoprotein A‐I (Part. Part. Syst. Charact. 6/2016)
下载免费PDF全文
![点击此处可从《Particle & Particle Systems Characterization》网站下载免费的PDF全文](/ch/ext_images/free.gif)
94.
Vogelhuber KM Wren SW Shaffer CJ McMahon RJ McCoy AB Lineberger WC 《The Journal of chemical physics》2011,135(20):204307
We report the 364-nm photoelectron spectrum of HC(4)N(-). We observe electron photodetachment from the bent X(2)A" state of HC(4)N(-) to both the near-linear X(3)A" and the bent ? (1)A' states of neutral HC(4)N. We observe an extended, unresolved vibrational progression corresponding to X(3)A" ← X(2)A" photodetachment, and we measure the electron affinity (EA) of the X(3)A" state of HC(4)N to be 2.05(8) eV. Photodetachment to the bent ? (1)A' state results in a single intense origin peak at a binding energy of 2.809(4) eV, from which we determine the singlet-triplet splitting (ΔE(ST)) of HC(4)N: 0.76(8) eV. For comparison and to aid in the interpretation of the HC(4)N(-) spectrum, we also report the 364-nm photoelectron spectra of HCCN(-) and DCCN(-). Improved signal-to-noise over the previous HCCN(-) and DCCN(-) photoelectron spectra allows for a more precise determination of the EAs and ΔE(ST)s of HCCN and DCCN. The EAs of HCCN and DCCN are measured to be 2.001(15) eV and 1.998(15) eV, respectively; ΔE(ST)(HCCN) is 0.510(15) eV and ΔE(ST)(DCCN) is 0.508(15) eV. These results are discussed in the context of other organic carbene chains. 相似文献
95.
Cludio M. Nunes Luís P. Viegas Samuel A. Wood Jos P. L. Roque Robert J. McMahon Rui Fausto 《Angewandte Chemie (International ed. in English)》2020,59(40):17622-17627
Not long ago, the occurrence of quantum mechanical tunneling (QMT) chemistry involving atoms heavier than hydrogen was considered unreasonable. Contributing to the shift of this paradigm, we present here the discovery of a new and distinct heavy‐atom QMT reaction. Triplet syn‐2‐formyl‐3‐fluorophenylnitrene, generated in argon matrices by UV‐irradiation of an azide precursor, was found to spontaneously cyclize to singlet 4‐fluoro‐2,1‐benzisoxazole. Monitoring the transformation by IR spectroscopy, temperature‐independent rate constants (k≈1.4×10?3 s?1; half‐life of ≈8 min) were measured from 10 to 20 K. Computational estimated rate constants are in fair agreement with experimental values, providing evidence for a mechanism involving heavy‐atom QMT through crossing triplet to singlet potential energy surfaces. Moreover, the heavy‐atom QMT takes place with considerable displacement of the oxygen atom, which establishes a new limit for the heavier atom involved in a QMT reaction in cryogenic matrices. 相似文献
96.
Tuning Phenols with Intra‐Molecular Bond Shifted HYdrogens (IM‐SHY) as diaCEST MRI Contrast Agents
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Xing Yang Nirbhay N. Yadav Xiaolei Song Prof. Sangeeta Ray Banerjee Hannah Edelman Il Minn Prof. Peter C. M. van Zijl Prof. Martin G. Pomper Prof. Michael T. McMahon 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(48):15824-15832
The optimal exchange properties for chemical exchange saturation transfer (CEST) contrast agents on 3 T clinical scanners were characterized using continuous wave saturation transfer, and it was demonstrated that the exchangeable protons in phenols can be tuned to reach these criteria through proper ring substitution. Systematic modification allows the chemical shift of the exchangeable protons to be positioned between 4.8 to 12 ppm from water and enables adjustment of the proton exchange rate to maximize CEST contrast at these shifts. In particular, 44 hydrogen‐bonded phenols are investigated for their potential as CEST MRI contrast agents and the stereoelectronic effects on their CEST properties are summarized. Furthermore, a pair of compounds, 2,5‐dihydroxyterephthalic acid and 4,6‐dihydroxyisophthalic acid, were identified which produce the highest sensitivity through incorporating two exchangeable protons per ring. 相似文献
97.
98.
Elizabeth W. McMahon 《Journal of Graph Theory》1993,17(3):433-442
We examine some properties of the 2-variable greedoid polynomial f(G·,t,z) when G is the branching greedoid associated to a rooted graph or a rooted directed graph. For rooted digraphs, we show a factoring property of f(G·,t,z) determines whether or not the rooted digraph has a directed cycle. © 1993 John Wiley & Sons, Inc. 相似文献
99.
The oscillation of electrons—as driven by AC polarization—can be used to extract a high-sensitivity signal from a conventional electron capture detector. For example, hexachloroethane was detected at a hypercoulometric ratio of 2.0 F/mol, down to ca. 60 fg/s (S/N=3) and with a linear range in excess of two orders of magnitude. The change in carrier gas from nitrogen to argon-methane produced the expected order-of-magnitude increase in optimum oscillation frequency. Anab initio simulation of potentials and ion populations in a heterogeneous electron capture system under a high-frequency AC regime provided further insight into the detector's mechanism: Hypercoulometric response is mainly caused by increased cation-electron recombination in the plasma region, owing to a decreased field gradient and an increased cation concentration.Material taken from doctoral thesis (Dalhousie University, 1987) 相似文献
100.
Pimelyldihydroxamic acid forms strong complexes with iron(III) in aqueous solution at pH 2–9. Plots of n? and proton liberation against pH show plateaux regions at values of 1.5 and 3.0, respectively, over the pH range 4.0–8.0 supporting a formulation of Fe2L3 (logβ = 41.06). The orage-red complex exhibits maximum absorbance at 420 nm, and a well-defined peak at 0.6 V vs. SCE in differential pulse polarography. 相似文献