全文获取类型
收费全文 | 256篇 |
免费 | 7篇 |
专业分类
化学 | 182篇 |
晶体学 | 1篇 |
力学 | 3篇 |
数学 | 42篇 |
物理学 | 35篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 12篇 |
2020年 | 4篇 |
2019年 | 7篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 8篇 |
2015年 | 4篇 |
2014年 | 7篇 |
2013年 | 14篇 |
2012年 | 28篇 |
2011年 | 16篇 |
2010年 | 14篇 |
2009年 | 6篇 |
2008年 | 27篇 |
2007年 | 17篇 |
2006年 | 20篇 |
2005年 | 13篇 |
2004年 | 4篇 |
2003年 | 3篇 |
2002年 | 11篇 |
2001年 | 3篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1996年 | 1篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1979年 | 1篇 |
1974年 | 1篇 |
1963年 | 1篇 |
1953年 | 2篇 |
1942年 | 1篇 |
1926年 | 1篇 |
1920年 | 2篇 |
1914年 | 2篇 |
1912年 | 2篇 |
1910年 | 2篇 |
1907年 | 2篇 |
1902年 | 2篇 |
1893年 | 1篇 |
排序方式: 共有263条查询结果,搜索用时 312 毫秒
71.
Farzana Miah Hendrik Koliwer-Brandl Martin Rejzek Robert A. Field Rainer Kalscheuer Stephen Bornemann 《Chemistry & biology》2013,20(4):487-493
Highlights? Flux through trehalose synthase (TreS) in mycobacteria is from trehalose to maltose ? The appropriate α anomer is formed by TreS for maltose kinase of the GlgE pathway ? The specificity of TreS for α-maltose is retained with deoxyfluoro analogs ? TreS supports cytosolic/capsular α-glucan but not trehalose mycolate biosynthesis 相似文献
72.
Dustin Cartwright Mathias H?bich Bernd Sturmfels Annette Werner 《Selecta Mathematica, New Series》2011,17(4):757-793
A Mustafin variety is a degeneration of projective space induced by a point configuration in a Bruhat-Tits building. The special
fiber is reduced and Cohen-Macaulay, and its irreducible components form interesting combinatorial patterns. For configurations
that lie in one apartment, these patterns are regular mixed subdivisions of scaled simplices, and the Mustafin variety is
a twisted Veronese variety built from such a subdivision. This connects our study to tropical and toric geometry. For general
configurations, the irreducible components of the special fiber are rational varieties, and any blow-up of projective space
along a linear subspace arrangement can arise. A detailed study of Mustafin varieties is undertaken for configurations in
the Bruhat-Tits tree of PGL(2) and in the 2-dimensional building of PGL(3). The latter yields the classification of Mustafin triangles into 38 combinatorial types. 相似文献
73.
Folkmar Bornemann 《Mathematische Semesterberichte》2002,48(2):247-260
Zusammenfassung. Wir zeigen, wie sich die schwach*-Konvergenz beschr?nkter Folgen eines Dualraums X' durch Normen charakterisieren l?sst, sofern der Pr?dualraum X separabel ist. Auf diese Weise lassen sich interessante Anwendungen der schwach*-Topologie bereits aus der Theorie normierter R?ume
herleiten – ein Vorteil etwa für einführende Vorlesungen in die lineare Funktionalanalysis, in welcher lokalkonvexe R?ume
nicht thematisiert werden k?nnen. Wir diskutieren die Anwendung des Satzes von Krein-Milman in seiner Fassung für normierte
R?ume und geben elementare Beweise des Lemmas von Schur sowie einer Verallgemeinerung des Riemann-Lebesgue'schen Lemmas.
Eingegangen am 16. Februar 2001 / Angenommen am 15. Mai 2001 相似文献
74.
Dustin Lazarovici 《Communications in Mathematical Physics》2016,345(1):271-304
We consider the discrete Gaussian Free Field in a square box in \({\mathbb{Z}^2}\) of side length N with zero boundary conditions and study the joint law of its properly-centered extreme values (h) and their scaled spatial positions (x) in the limit as \({N \to \infty}\). Restricting attention to extreme local maxima, i.e., the extreme points that are maximal in an rN-neighborhood thereof, we prove that the associated process tends, whenever \({r_N \to \infty}\) and \({r_N/N \to 0}\), to a Poisson point process with intensity measure \({Z{(\rm dx)}{\rm e}^{-\alpha h} {\rm d}h}\), where \({\alpha:= 2/\sqrt{g}}\) with g: = 2/π and where Z(dx) is a random Borel measure on [0, 1]2. In particular, this yields an integral representation of the law of the absolute maximum, similar to that found in the context of Branching Brownian Motion. We give evidence that the random measure Z is a version of the derivative martingale associated with the continuum Gaussian Free Field. 相似文献
75.
Disney MD Labuda LP Paul DJ Poplawski SG Pushechnikov A Tran T Velagapudi SP Wu M Childs-Disney JL 《Journal of the American Chemical Society》2008,130(33):11185-11194
Herein is described the identification of RNA internal loops that bind to derivatives of neomycin B, neamine, tobramycin, and kanamycin A. RNA loop-ligand partners were identified by a two-dimensional combinatorial screening (2DCS) platform that probes RNA and chemical spaces simultaneously. In 2DCS, an aminoglycoside library immobilized onto an agarose microarray was probed for binding to a 3 x 3 nucleotide RNA internal loop library (81,920 interactions probed in duplicate in a single experiment). RNAs that bound aminoglycosides were harvested from the array via gel excision. RNA internal loop preferences for three aminoglycosides were identified from statistical analysis of selected structures. This provides consensus RNA internal loops that bind these structures and include: loops with potential GA pairs for the neomycin derivative, loops with potential GG pairs for the tobramycin derivative, and pyrimidine-rich loops for the kanamycin A derivative. Results with the neamine derivative show that it binds a variety of loops, including loops that contain potential GA pairs that also recognize the neomycin B derivative. All studied selected internal loops are specific for the aminoglycoside that they were selected to bind. Specificity was quantified for 16 selected internal loops by studying their binding to each of the arrayed aminoglycosides. Specificities ranged from 2- to 80-fold with an average specificity of 20-fold. These studies show that 2DCS is a unique platform to probe RNA and chemical space simultaneously to identify specific RNA motif-ligand interactions. 相似文献
76.
Stahla ML Baruah B James DM Johnson MD Levinger NE Crans DC 《Langmuir : the ACS journal of surfaces and colloids》2008,24(12):6027-6035
Simple procedures and characterization of a series of well-defined precursors are described for preparation of a unique microenvironment in nanoreactors, reverse micelles. The Na(+), K(+), Rb(+), Cs(+), and Mg(2+) surfactants were prepared using liquid-liquid ion exchange using chloride and nitrate salts. The surfactants were characterized using (1)H NMR spectroscopy and a variety of other techniques. (1)H NMR spectroscopy was found to be a sensitive probe for characterization of the size of the nanoreactor as well as its water content. (1)H NMR spectra can be used for detailed characterization of reactions in confined environments when counterion effects are likely to be important. (1)H NMR spectroscopy revealed two separate peaks corresponding to water in Mg(AOT)2 samples; one peak arises from water coordinated to the Mg(2+) ion while the other peak arises from bulk water. The two water signals arise directly from the slow exchange of the water coordinated to Mg(2+) in these microemulsions with water in the water pool, and provide an opportunity to study hydration of Mg(2+). This work thus extends the potential use of MAOT microemulsions for applications such as in green chemistry. 相似文献
77.
Tobin A. Driscoll Folkmar Bornemann Lloyd N. Trefethen 《BIT Numerical Mathematics》2008,48(4):701-723
In Matlab, it would be good to be able to solve a linear differential equation by typing u = L\f, where f, u, and L are representations
of the right-hand side, the solution, and the differential operator with boundary conditions. Similarly it would be good to
be able to exponentiate an operator with expm(L) or determine eigenvalues and eigenfunctions with eigs(L). A system is described
in which such calculations are indeed possible, at least in one space dimension, based on the previously developed chebfun
system in object-oriented Matlab. The algorithms involved amount to spectral collocation methods on Chebyshev grids of automatically determined resolution.
AMS subject classification (2000) 65L10, 65M70, 65N35 相似文献
78.
Evans WJ Montalvo E Dixon DJ Ziller JW Dipasquale AG Rheingold AL 《Inorganic chemistry》2008,47(23):11376-11381
Reaction of the lanthanide metallocene allyl complexes, (C(5)Me(5))(2)Ln(eta(3)-CH(2)CHCH(2))(THF) (Ln = Ce, Sm, Y) with 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine, Hhpp, forms a series of metallocene complexes, (C(5)Me(5))(2)Ln(hpp) (Ln = Ce, Sm, Y) in which the (hpp)(1-) anion coordinates as a terminal bidentate ligand. Isomorphous structures were observed by X-ray crystallography regardless of the size of the metal. The acetonitrile adduct, (C(5)Me(5))(2)Sm(hpp)(MeCN), was also crystallographically characterized to provide an unusual pair of eight- and nine-coordinate complexes. The coordination mode of the (hpp)(1-) anion in these complexes is compared with that in other heteroallylic metallocenes like the caprolactamate (C(5)Me(5))(2)Y(ONC(6)H(10)) and the dithiocarbamate (C(5)Me(5))(2)Sm(S(2)CNEt(2)), which was also structurally characterized. 相似文献
79.
The interactions between cholesterol and saturated phospholipids in hybrid bilayer membranes (HBMs) were investigated using the interface-sensitive technique of vibrational sum frequency spectroscopy (VSFS). The unique sensitivity of VSFS to order/disorder transitions of the lipid acyl chains was used to determine the main gel to liquid crystal phase transition temperature, Tm, for HBMs of binary cholesterol/phospholipid mixtures on octadecanethiolate self-assembled monolayers. The phase transition temperature and the breadth of the transition were shown to increase with cholesterol content, and the phase boundaries observed in the cholesterol/phospholipid HBMs were comparable to the published phase diagrams of binary cholesterol/phospholipid vesicles. A thermodynamic assessment of the cooperative units of the HBM phase transitions revealed the presence of <10 nm diameter domains that were independent of the cholesterol composition. 相似文献
80.
DeYonker NJ Ho DS Wilson AK Cundari TR 《The journal of physical chemistry. A》2007,111(42):10776-10780
The correlation consistent composite approach (ccCA) is a model chemistry that has been shown to accurately compute gas-phase enthalpies of formation for alkali and alkaline earth metal oxides and hydroxides (Ho, D. S.; DeYonker, N. J.; Wilson, A. K.; Cundari, T. R. J. Phys. Chem. A 2006, 110, 9767).The ccCA results contrast to more widely used model chemistries where calculated enthalpies of formation for such species can be in error by up to 90 kcal mol-1. In this study, we have applied ccCA to a more general set of 42 s-block molecules and compared the ccCA DeltaHf values to values obtained using the G3 and G3B model chemistries. Included in this training set are water complexes such as Na(H2O)n+ where n = 1 - 4, dimers and trimers of ionic compounds such as (LiCl)2 and (LiCl)3, and the largest ccCA computation to date: Be(acac)2, BeC10H14O4. Problems with the G3 model chemistries seem to be isolated to metal-oxygen bonded systems and Be-containing systems, as G3 and G3B still perform quite well with a 2.7 and 2.6 kcal mol-1 mean absolute deviation (MAD), respectively, for gas-phase enthalpies of formation. The MAD of the ccCA is only 2.2 kcal mol-1 for enthalpies of formation (DeltaHf) for all compounds studied herein. While this MAD is roughly double that found for a ccCA study of >350 main group (i.e., p-block) compounds, it is commensurate with typical experimental uncertainties for s-block complexes. Some molecules where G3/G3B and ccCA computed DeltaHf values deviate significantly from experiment, such as (LiCl)3, NaCN, and MgF, are inviting candidates for new experimental and high-level theoretical studies. 相似文献