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81.
Synthetic biosystems have been engineered that enable control of metazoan cell morphology, migration, and death. These systems possess signal specificity, but lack flexibility of input signal. To exploit the potential of Ca2+ signaling, we designed RhoA chimeras for reversible, Ca2+-dependent control over RhoA morphology and migration. First, we inserted a calmodulin-binding peptide into a RhoA loop that activates or deactivates RhoA in response to Ca2+ signals depending on the chosen peptide. Second, we localized the Ca2+-activated RhoA chimera to the plasma membrane, where it responded specifically to local Ca2+ signals. Third, input control of RhoA morphology was rewired by coexpressing the Ca2+-activated RhoA chimera with Ca2+-transport proteins using acetylcholine, store-operated Ca2+ entry, and blue light. Engineering synthetic biological systems with input versatility and tunable spatiotemporal responses motivates further application of Ca2+ signaling in this field. 相似文献
82.
James WH Buchanan EG Guo L Gellman SH Zwier TS 《The journal of physical chemistry. A》2011,115(43):11960-11970
Resonant two-photon ionization (R2PI), IR-UV holeburning (IR-UV), and resonant ion-dip infrared spectroscopy (RIDIRS) have been used to record mass-selected, single-conformation ultraviolet and infrared spectra of three simple diamide derivatives of γ-amino acids as isolated molecules cooled in a supersonic expansion. This work builds on an earlier study of Ac-γ(2)-hPhe-NHMe (James, W. H., III, et al. J. Am. Chem. Soc. 2009, 131, 14243), which showed that this methyl-capped γ-peptide forms amide-stacked conformations that are similar in stability to H-bonded conformations containing a C9 ring and more stable than C7 H-bonded ring structures. Among the γ-peptides discussed here, Ac-γ(2)-hPhe-N(Me)(2) contains an additional methyl group relative to the previously studied Ac-γ(2)-hPhe-NHMe and therefore lacks the amide NH group responsible for C9 ring formation. Three conformations of Ac-γ(2)-hPhe-N(Me)(2) are observed, all of which are amide-stacked structures. In a second new molecule, Ac-γ(2)-hPhe-NH(iPr), the C-terminal NHMe group of Ac-γ(2)-hPhe-NHMe is replaced with an NH(iPr) group. Three conformations of Ac-γ(2)-hPhe-NH(iPr) are observed, all of which are C9 H-bonded structures. The dramatic difference between C-terminal NHMe and NH(iPr) reveals the delicate balance of noncovalent forces within these γ-peptides. The third molecule we examined is a gabapentin-derived diamide (designated 1), which contains a phenylacyl group at the N-terminus and an N(Me)(2) group at the C-terminus; the latter precludes C9 H bonding. Comparison of 1 with Ac-γ(2)-hPhe-N(Me)(2) allows us to examine the impact of the backbone substitution pattern (monosubstitution at carbon-2 vs disubstitution at carbon-3) on the competition between the C7 H-bonded and the amide-stacked conformation. In this case, only C7 rings are observed. The different gas-phase behaviors observed among the molecules analyzed here offer insight on the intrinsic conformational propensities of the γ-peptide backbone, information that provides a foundation for future foldamer design efforts. 相似文献
83.
Chan J Burke BJ Baucom K Hansen K Bio MM DiVirgilio E Faul M Murry J 《The Journal of organic chemistry》2011,76(6):1767-1774
Two new, reliable syntheses of a pyrido[2,3-d]-pyrimidine inhibitor of the CXCR3 receptor are described. A nine-step synthesis of the CXCR3 inhibitor (1) from 2-aminonicotinic acid was demonstrated on a multikilogram scale and incorporates a classic resolution to deliver the enantioenriched active pharmaceutical ingredient (API). A second synthesis of the CXCR3 inhibitor starts from (+)-(D)-Boc alanine and 2-chloronicotinic acid and utilizes a Goldberg coupling. This second synthesis, performed on a gram scale, intersects the former route at a common intermediate thereby completing a formal synthesis of the enantioenriched API in higher overall yield without the need for a resolution. 相似文献
84.
A europium probe for the ratiometric detection of potassium in water is presented. This probe demonstrates high sensitivity, with an affinity for K(+) in the mM range, and high selectivity for K(+) over Na(+), Ca(2+), Mg(2+) and Li(+). The long luminescence lifetime of the probe and its large Stokes shift further enable accurate determination of the concentration of K(+) in complex aqueous media. 相似文献
85.
Evan H. Abramson 《高压研究》2013,33(4):544-548
A rolling-sphere technique has been used to measure shear viscosities of (supercritical) fluid argon in the diamond-anvil cell between the temperatures of 294 and 673 K, up to a maximum pressure of 5 GPa. At these pressures, the viscosities can be fit to a modified free-volume expression. A single correlation between reduced viscosity and reduced residual entropy is shown to give a good account of the current high pressure data, data at lower pressures and those for the sub-critical liquid. 相似文献
86.
G. Evan Roberts Johan P. A. Heuts Thomas P. Davis 《Journal of polymer science. Part A, Polymer chemistry》2003,41(6):752-765
The cobaloxime‐mediated catalytic‐chain‐transfer polymerization of styrene at 60 °C was studied with an emphasis on the effects of monomer purification and polymerization conditions. Commonly used purification methods, such as column chromatography and simple vacuum distillation, were not adequate for obtaining kinetic data to be used in mechanistic modeling. A purification regime involving inhibitor removal with basic alumina, followed by polymerization of the styrene in the presence of the cobaloxime and subsequent vacuum distillation, was found to be essential to this end. It was then possible to quantitatively investigate effects such as the initiator concentration and conversion dependencies of the apparent chain‐transfer constant that resulted from the occurrence of cobalt–carbon bond formation. A value of about 9 × 103 was found for the true chain‐transfer constant to cobaloxime boron fluoride, that is, its value in the absence of cobalt–carbon bond formation. Furthermore, previous predictions were confirmed: the measured chain‐transfer constant decreased with increasing initiator concentration and conversion. Finally, it was confirmed that the presence of light increased the amount of free Co(II) catalyst in agreement with other studies. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 752–765, 2003 相似文献
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90.
Evan P. Kyba Steven P. Rines Philip W. Owens Shang-Shing P. Chou 《Tetrahedron letters》1981,22(20):1875-1878
Synthesis of phosphorylchloroacetylenes, diphosphorylacetylenes and the Diels-Alder reactions of the latter to produce -diphosphorylbenzenes are described. 相似文献