全文获取类型
收费全文 | 411篇 |
免费 | 21篇 |
专业分类
化学 | 366篇 |
晶体学 | 3篇 |
力学 | 3篇 |
数学 | 22篇 |
物理学 | 38篇 |
出版年
2023年 | 5篇 |
2022年 | 8篇 |
2021年 | 4篇 |
2020年 | 8篇 |
2019年 | 8篇 |
2018年 | 8篇 |
2017年 | 6篇 |
2016年 | 9篇 |
2015年 | 10篇 |
2014年 | 12篇 |
2013年 | 26篇 |
2012年 | 28篇 |
2011年 | 42篇 |
2010年 | 19篇 |
2009年 | 17篇 |
2008年 | 43篇 |
2007年 | 26篇 |
2006年 | 27篇 |
2005年 | 35篇 |
2004年 | 18篇 |
2003年 | 16篇 |
2002年 | 10篇 |
2001年 | 2篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1974年 | 1篇 |
1965年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有432条查询结果,搜索用时 9 毫秒
11.
Electronically modified PHOX ligands 3a-e were synthesized to probe the mechanism of the enantioselective palladium-catalyzed allylic alkylation and amination reactions. Alkylation with dimethyl sodiomalonate produced only a small variation in the ee (89.3% to 93.4%), but amination with benzylamine gave a much wider variation in the ee (16.4% to 66.6%). Hammett analysis suggests that the substituents interact more significantly with phosphorus and supports a combined electronic and steric basis for enantioselection. [reaction: see text] 相似文献
12.
Maureen M. Tedesco Bereket Ghebremariam Naomi Sakai Stefan Matile 《Angewandte Chemie (International ed. in English)》1999,38(4):540-543
A supramolecular ion channel model mediates transmembrane ion transport (shown schematically) with a selectivity topology similar to that of K+ channels. This supports the biological significance of flexible arene arrays as selective cation binding sites. 相似文献
13.
Naomi C. Delic J. Guy Lyons Nick Di Girolamo Gary M. Halliday 《Photochemistry and photobiology》2017,93(4):920-929
The cornea sits at the anterior aspect of the eye and, like the skin, is highly exposed to ultraviolet radiation (UVR). The cornea blocks a significant proportion of UVB from reaching the posterior structures of the eye. However, UVA can penetrate the full thickness of the cornea, even reaching the anterior portion of the lens. Epidemiological data indicate that UVR is a contributing factor for a multitude of diseases of the cornea including pterygium, photokeratitis, climatic droplet keratopathy and ocular surface squamous neoplasia (OSSN), although the pathogenic mechanisms of each require further elucidation. UVR is a well‐known genotoxic agent, and its effects have been well characterized in organs such as the skin. However, we are only beginning to identify its effects on the cornea, such as the UVR signature C → T and CC → TT transversions identified by sequencing and increased proliferative and shedding rates in response to UVR exposure. Alarmingly, a single low‐dose exposure of UVR to the cornea is sufficient to elicit genetic, molecular and cellular changes, supporting the consideration of using protective measures, such as wearing sunglasses when outdoors. The aim of this review was to describe the adverse effects of UVR on the cornea. 相似文献
14.
Berman Abraham Shaked-Monderer Naomi 《Central European Journal of Operations Research》2022,30(3):1093-1099
Central European Journal of Operations Research - Completely positive matrices are matrices that can be decomposed as $$BB^T$$ , where B is an entrywise nonnegative matrix. These matrices have many... 相似文献
15.
Chromium tricarbonyl complexes of 3-methoxybenzyl alcohol and related compounds were selectively lithiated at the 4-position in contrast to the corresponding metal free arene compounds. The resulting 4-lithio complexes were converted to the 4-substituted arene compounds in moderate to excellent yields through the reactions with proper electrophiles and subsequent demetalation. 相似文献
16.
Benjamin Nabet Naomi E. Leonard Iain D. Couzin Simon A. Levin 《Journal of Nonlinear Science》2009,19(4):399-435
We analyze a continuous-time model of a multi-agent system motivated by simulation studies on dynamics of decision making
in animal groups in motion. Each individual moves at constant speed in the plane and adjusts its heading in response to relative
headings of others in the population. The population includes two subgroups that are “informed” such that individuals in each
subgroup have a preferred direction of motion. The model exhibits fast and slow time scales allowing for a reduction in the
dimension of the problem. The stable solutions for the reduced model correspond to compromise by individuals with conflicting
preferences. We study the global phase space for the proposed reduced model by computing equilibria and exploring stability
and bifurcations.
B. Nabet’s and N.E. Leonard’s work is supported in part by AFOSR grant FA9550-07-1-0-0528 and ONR grants N00014-02-1-0826
and N00014-04-1-0534.
I.D. Couzin’s work was supported by the Royal Society, Balliol College and EPSRC grants GR/S04765/01 and GR/T11234/01, a Searle
Scholar Award and DARPA grant HR001-05-1-0057.
S.A. Levin’s work was supported in part by DARPA grant HR0011-05-1-0057 and NSF grant EF-0434319. 相似文献
17.
The purpose of this paper is to prove that a primitive Hilbert cusp form \(\mathbf{g}\) is uniquely determined by the central values of the Rankin–Selberg L-functions \(L(\mathbf{f}\otimes \mathbf{g}, \frac{1}{2})\), where \(\mathbf{f}\) runs through all primitive Hilbert cusp forms of weight \(k\) for infinitely many weight vectors \(k\). This result is a generalization of the work of Ganguly et al. (Math Ann 345:843–857, 2009) to the setting of totally real number fields, and it is a weight aspect analogue of our previous work (Hamieh and Tanabe in Trans Am Math Soc, arXiv:1609.07209, 2016). 相似文献
18.
Advances in scattering-based optical imaging technologies offer a new approach to noninvasive point-of-care detection, diagnosis, and monitoring of cancer. Emerging photonics technologies provide a cost-effective means to image tissue in vivo with high resolution in real time. Advancing the clinical potential of these imaging strategies requires the development of optical contrast agents targeted to specific molecular signatures of disease. We describe the use of a novel class of contrast agents based on nanoshell bioconjugates for molecular imaging in living cells. Nanoshells offer significant advantages over conventional imaging probes including continuous and broad wavelength tunability, far greater scattering and absorption coefficients, increased chemical stability, and improved biocompatibility. We show that nanoshell bioconjugates can be used to effectively target and image human epidermal growth factor receptor 2 (HER2), a clinically relevant biomarker, in live human breast carcinoma cells. 相似文献
19.
Jesús Chaboy María ángeles Laguna‐Marco Cristina Piquer Roberto Boada Neculai Plugaru Hiroshi Maruyama Naomi Kawamura 《Journal of synchrotron radiation》2009,16(3):405-412
An X‐ray magnetic circular dichroism (XMCD) study performed at the rare‐earth L2,3‐edges in the RxR1?x′Al2 compounds is presented. It is shown that both R and R′ atoms contribute to the XMCD recorded at the L‐edges of the selected rare‐earth, either R or R′. The amplitude of the XMCD signal is not directly correlated to the magnetization or to the value of the individual (R, R′) magnetic moments, but it is related to the molecular field acting on the rare‐earth tuned in the photoabsorption process. This result closes a longstanding study of the origin of the XMCD at the L‐edge of the rare‐earths in multi‐component systems, allowing a full understanding of the exact nature of these signals. 相似文献
20.
Kurihara H Lu X Iiduka Y Mizorogi N Slanina Z Tsuchiya T Akasaka T Nagase S 《Journal of the American Chemical Society》2011,133(8):2382-2385
Unambiguous X-ray crystallographic results of the carbene adduct of Sc(2)C(82) reveal a new carbide cluster metallofullerene with the unexpected C(2v)(5)-C(80) cage, that is, Sc(2)C(2)@C(2v)(5)-C(80). More interestingly, DFT calculations and NMR results disclose that the dynamic motion of the internal Sc(2)C(2) cluster depends strongly on temperature. At 293 K, the cluster is fixed inside the cage with two nonequivalent Sc atoms on the mirror plane, thereby leading to C(s) symmetry of the whole molecule. However, when the temperature increases to 413 K, the (13)C and (45)Sc NMR spectra show that the cluster rotates rapidly inside the C(2v)(5)-C(80) cage, featuring two equivalent Sc atoms and weaker metal-cage interactions. 相似文献