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91.
Paul J. Sanders 《代数通讯》2013,41(3):1309-1333
A sharp bound is derived for the nilpotency class of a regular p-group in terms of its coexponent, and is used to show that the number of groups of order pn with a given fixed coexponent, is independent of n, for p and n sufficiently large. Explicit formulae are calculated in the case of coexponent 3. 相似文献
92.
L. Reeve T. Swinden W. W. Stevenson G. E. Speight H. A. Sloman F. Willems N. Gray M. C. Sanders S. N. Schkotowa H. Kempf K. Abresch G. J. Weinberg R. Stumper P. Mettelock F. Wüst J. Duhr P. Klinger W. Koch H. Schottky H. Hiltenkamp H. J. Wiester I. Wada R. Ishii 《Analytical and bioanalytical chemistry》1943,126(10):385-390
93.
94.
Nielen MW Lasaroms JJ Essers ML Oosterink JE Meijer T Sanders MB Zuidema T Stolker AA 《Analytical and bioanalytical chemistry》2008,391(1):199-210
The use of β-agonists as growth promoters in cattle breeding is forbidden in many countries for reasons of fair trade and
consumer protection. In recent years the use of liquid chromatography (LC) tandem mass spectrometry (MS/MS) has been shown
to be the method of choice for the control of β-agonists. In this study an LC-MS/MS multiresidue analysis method is presented
for trace analysis of 22 β-agonists. A truly generic concept has been designed based on mixed-mode solid-phase extraction
and positive electrospray ionisation LC-MS/MS operated in the multiple reaction monitoring mode. This method allows application
to a wide variety of sample matrices such as urine, feed and hair, following minor modifications to the analysis procedure
only. The method features fit-for-purpose sensitivity in urine as shown by CCα and CCβ values of less than 0.2 and less than
0.5 μg/l respectively, for all β-agonists studied (terbutaline and reproterol, less than 0.3 and less than 1.0 respectively).
Similar but semiquantitative application to feed and hair showed CCβ values of less than 10.0 and less than 5.0 μg/kg, respectively.
A further simplification and improvement is demonstrated using Ultra Performance LC (UPLC™) and fast-switching MS/MS. The
successful validation of this method following the latest EU requirements and its application to real samples demonstrate
that a new versatile tool has been achieved for veterinary control of β-agonists. 相似文献
95.
Pérez-Fernández R Pittelkow M Belenguer AM Sanders JK 《Chemical communications (Cambridge, England)》2008,(15):1738-1740
A two-phase approach to dynamic combinatorial chemistry is described using disulfide exchange chemistry; the use of two phases significantly increases the possibilities and the scope of dynamic combinatorial chemistry by facilitating the combination of otherwise incompatible building blocks. 相似文献
96.
Jennifer E. Golden Shanina D. Sanders Kristine M. Muller Roland W. Bürli 《Tetrahedron letters》2008,49(5):794-798
The regioselective, copper-catalyzed coupling of a tautomeric pyrazolone/pyrazole with 2-halopyridines was investigated. Conditions were developed to preferentially form either the N-aryl or O-aryl product. 相似文献
97.
Scott Matteucci Victor A. Kusuma David Sanders Steve Swinnea Benny D. Freeman 《Journal of membrane science》2008
Titanium dioxide (TiO2) nanoparticles were dispersed via solution processing in poly(1-trimethylsilyl-1-propyne) (PTMSP) to form nanocomposite films. Nanoparticle dispersion was investigated using atomic force microscopy and transmission electron microscopy. At low-particle loadings, nanoparticles were dispersed individually and in nanoscale aggregates. At high-particle loadings, some nanoparticles formed micron-sized aggregates. The gas transport and density exhibited a strong dependence on nanoparticle loading. At low-TiO2 loadings, the composite density was similar to or slightly higher than that predicted by a two-phase additive model. However, at particle loadings exceeding approximately 7 nominal vol.%, the density was markedly lower than predicted, suggesting that the particles induced the creation of void space within the nanocomposite. For example, when the TiO2 nominal volume fraction was 0.35, the polymer/particle composite density was 40% lower than expected based on a two-phase additive model for density. At low-nanoparticle loading, light gas permeability was lower than that of the unfilled polymer. At higher nanoparticle loadings, light gas permeability (i.e., CO2, N2, and CH4) increased to more than four times higher than in unfilled PTMSP. At most, selectivity changed only slightly with particle loading. 相似文献
98.
Yuan Y Bleile DW Wen X Sanders DA Itoh K Liu HW Pinto BM 《Journal of the American Chemical Society》2008,130(10):3157-3168
UDP-galactopyranose mutase (UGM) is the key enzyme involved in the biosynthesis of Galf. UDP-Galp and UDP-Galf are two natural substrates of UGM. A protocol that combines the use of STD-NMR spectroscopy, molecular modeling, and CORCEMA-ST calculations was applied to the investigation of the binding of UDP-Galf and its C3-fluorinated analogue to UGM from Klebsiella pneumoniae. UDP-Galf and UDP-[3-F]Galf were bound to UGM in a manner similar to that of UDP-Galp. The interconversions of UDP-Galf and UDP-[3-F]Galf to their galactopyranose counterparts were catalyzed by the reduced (active) UGM with different catalytic efficiencies, as observed by NMR spectroscopy. The binding affinities of UDP-Galf and UDP-[3-F]Galf were also compared with those of UDP-Galp and UDP by competition STD-NMR experiments. When UGM was in the oxidized (inactive) state, the binding affinities of UDP-Galf, UDP-Galp, and UDP-[3-F]Galf were of similar magnitudes and were lower than that of UDP. However, when UGM was in the reduced state, UDP-Galp had higher binding affinity compared with UDP. Molecular dynamics (MD) simulations indicated that the "open" mobile loop in UGM "closes" upon binding of the substrates. Combined MD simulations and STD-NMR experiments were used to create models of UGM with UDP-Galf and UDP-[3-F]Galf as bound ligands. Calculated values of saturation-transfer effects with CORCEMA-ST (complete relaxation and conformational exchange matrix analysis of saturation transfer) were compared to the experimental STD effects and permitted differentiation between two main conformational families of the bound ligands. Taken together, these results are used to rationalize the different rates of catalytic turnover of UDP-Galf and UDP-[3-F]Galf and shed light on the mechanism of action of UGM. 相似文献
99.
Jones AC Sanders AW Sikorski WH Jansen KL Reich HJ 《Journal of the American Chemical Society》2008,130(19):6060-6061
Low-temperature rapid-injection NMR (RINMR) experiments were performed on tris(trimethylsilyl)methyllithium. In THF/Me2O solutions, the separated ion (1S) reacted faster than can be measured at -130 degrees C with MeI and substituted benzaldehydes (k >/= 2 s -1), whereas the contact ion (1C) dissociated to 1S before reacting. Unexpectedly, the triple ion reacted faster with electron-rich benzaldehydes relative to electron-deficient ones. The addition of HMPA had no effect on the rate of reaction of the triple ion with p-diethylaminobenzaldehyde, and the immediate product of the reaction was the HMPA-solvated separated ion 1S, with the Peterson product forming only slowly. Thus, the aldehyde is catalyzing the dissociation of the triple ion. HMPA greatly decelerated the reaction of 1S (<10 -10), providing an estimate of the Lewis acid activating effect of a THF-solvated lithium cation in an organolithium addition to an aldehyde. 相似文献
100.
Pascu SI Naumann C Kaiser G Bond AD Sanders JK Jarrosson T 《Dalton transactions (Cambridge, England : 2003)》2007,(35):3874-3884
Kinetic stability studies of a series of pseudorotaxanes formed from electron-rich crown ethers (hosts and ) and naphthalene diimide (guest ) in the presence of alkali salt templates MX (where M(+) = Li(+) and Na(+), and X(-) = Cl(-), Br(-), I(-), NO(3)(-) and CF(3)SO(3)(-)) were performed by (1)H NMR. The switching between the (bound) host and its linkage isomer host (free) was monitored in solution in the presence and absence of alkali salts, to establish the relative thermodynamic stabilities in the series. We also report here six new crystal structures, for pseudorotaxanes of type: [.], [M(2)..](2+) and [M(2)..](2+). Their solution-phase structures are in good agreement with the solid-state structures determined by X-ray crystallography. 相似文献