全文获取类型
收费全文 | 216篇 |
免费 | 0篇 |
专业分类
化学 | 185篇 |
晶体学 | 2篇 |
力学 | 3篇 |
数学 | 10篇 |
物理学 | 16篇 |
出版年
2020年 | 1篇 |
2017年 | 3篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2013年 | 5篇 |
2012年 | 11篇 |
2011年 | 8篇 |
2010年 | 4篇 |
2009年 | 7篇 |
2008年 | 9篇 |
2007年 | 7篇 |
2006年 | 5篇 |
2005年 | 12篇 |
2004年 | 7篇 |
2003年 | 7篇 |
2002年 | 10篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 4篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 11篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 6篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1969年 | 2篇 |
1968年 | 1篇 |
1966年 | 1篇 |
1962年 | 1篇 |
1934年 | 1篇 |
1933年 | 2篇 |
排序方式: 共有216条查询结果,搜索用时 0 毫秒
211.
Beu SC Hendrickson CL Marshall AG 《Journal of the American Society for Mass Spectrometry》2011,22(3):591-601
Radiofrequency (rf) multipole ion guides are widely used to transfer ions through the strong magnetic field gradient between
source and analyzer regions of external source Fourier transform ion cyclotron resonance mass spectrometers. Although ion
transfer as determined solely by the electric field in a multipole ion guide has been thoroughly studied, transfer influenced
by immersion in a strong magnetic field gradient has not been as well characterized. Recent work has indicated that the added
magnetic field can have profound effects on ion transfer, ultimately resulting in loss of ions initially contained within
the multipole. Those losses result from radial ejection of ions due to transient cyclotron resonance that occurs when ions
traverse a region in which the magnetic field results in an effective cyclotron frequency equal to the multipole rf drive
frequency divided by the multipole order (multipole order is equal to one-half the number of poles). In this work, we describe
the analytical basis for ion resonance in a rf multipole ion guide with superposed static magnetic field and compare with
results of numerical trajectory simulations. 相似文献
212.
213.
Wilcox BE Hendrickson CL Marshall AG 《Journal of the American Society for Mass Spectrometry》2002,13(11):1304-1312
Externally generated ions are accumulated in a linear octopole ion trap before injection into our 9.4 T Fourier transform ion cyclotron resonance (FT-ICR) mass analyzer. Such instrumental configuration has previously been shown to provide improved sensitivity, scan rate, and duty cycle relative to accumulated trapping in the ICR cell. However, inefficient ion ejection from the octopole currently limits both detection limit and scan rate. SIMION 7.0 analysis predicts that a dc axial electric field inside the linear octopole ion trap expedites and synchronizes the efficient extraction of the octopole-accumulated ions. Further SIMION analysis optimizes the ion ejection properties of each of three electrode configurations designed to produce a near-linear axial potential gradient. More efficient extraction and transfer of accumulated ions spanning a wide m/z range promises to reduce detection limit and increase front-end sampling rate (e.g., to increase front-end resolution for separation techniques coupled with FT-ICR mass analysis). Addition of the axial field improves experimental signal-to-noise ratio by more than an order of magnitude. 相似文献
214.
The reactions of the ligands N-methyldiethanol amine and N-ethyldiethanol amine (abbreviated H(2)mdea and H(2)edea, respectively) with [Mn(12)O(12)(O(2)CCH(3))(16)(H(2)O)(4)] yield novel dodecanuclear wheel-shaped products. The capability of the ligands H(2)mdea and H(2)edea to support wheel structures in metals other than Mn is demonstrated with the crystal structure of a new hexanuclear ferric wheel. 相似文献
215.
Sydora OL Henry TP Wolczanski PT Lobkovsky EB Rumberger E Hendrickson DN 《Inorganic chemistry》2006,45(2):609-626
A convenient synthesis of (t)Bu(3)SiSH and (t)Bu(3)SiSNa(THF)(x)() led to the exploration of "(t)Bu(3)SiSMX" aggregation. The dimer, [((t)Bu(3)SiS)Fe](2)(mu-SSi(t)Bu(3))(2) (1(2)), was formed from [{(Me(3)Si)(2)N}Fe](2)(mu-N(SiMe(3))(2))(2) and the thiol, and its dissolution in THF generated ((t)Bu(3)SiS)(2)Fe(THF)(2) (1-(THF)(2)). Metathetical procedures with the thiolate yielded aggregate precursors [X(2)Fe](mu-SSi(t)Bu(3))(2)[FeX(THF)]Na(THF)(4) (3-X, X = Cl, Br) and cis-[(THF)IFe](2)(mu-SSi(t)Bu(3))(2) (4). Thermal desolvations of 3-Cl, 3-Br and 4 afforded molecular wheels [Fe(mu-X)(mu-SSi(t)Bu(3))](12)(C(6)H(6))(n) (5-FeX, X = Cl, Br) and the ellipse [Fe(mu-I)(mu-SSi(t)Bu(3))](14)(C(6)H(6))(n) (6-FeI). Related metathesis and desolvation sequences led to wheels [Co(mu-Cl)(mu-SSi(t)Bu(3))](12)(C(6)H(6))(n) (5-CoCl) and [Ni(mu-Br)(mu-SSi(t)Bu(3))](12)(C(6)H(6))(n) (5-NiBr). The nickel wheel disproportionated to give, in part, [((t)Bu(3)SiS)Ni](2)(mu-SSi(t)Bu(3))(2) (7), which was also synthesized via salt metathesis. X-ray structural studies of 1(2) revealed a roughly planar Fe(2)S(4) core, while 1-(THF)(2), 3-Br, and 4 possessed simple distorted tetrahedral and edge-shared tetrahedral structures. X-ray structural studies revealed 5-MX (MX = FeCl, FeBr, CoCl, NiBr) to be wheels based on edge-shared tetrahedra, but while the pseudo-D(6)(d) wheels of 5-FeCl, 5-CoCl, and 5-FeBr pack in a body-centered arrangement, those of pseudo-C(6)(v)() 5-NiBr exhibit hexagonal packing and two distinct trans-annular d(Br...Br). Variable-temperature magnetic susceptibility measurements were conducted on 5-FeCl, 5-CoCl, 5-FeBr, and 6-FeI, and the latter three are best construed as weakly antiferromagnetic, while 5-FeCl exhibited modest ferromagnetic coupling. Features suggesting molecular magnetism are most likely affiliated with phase changes at low temperatures. 相似文献
216.