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排序方式: 共有186条查询结果,搜索用时 31 毫秒
101.
X Fang KW Ledingham P Graham DJ Smith T McCanny RP Singhal AJ Langley PF Taday 《Rapid communications in mass spectrometry : RCM》1999,13(14):1390-1397
The potential of femtosecond laser time-of-flight mass spectrometry (FLMS) for uniform quantitative analysis of molecules has been investigated. Various samples of molecular gases and vapours have been studied, using ultra-fast ( approximately 50 fs) laser pulses with very high intensity (up to 1.6 x 10(16) Wcm(-2)) for non-resonant multiphoton ionisation/tunnel ionisation. Some of these molecules have high ionisation potentials, requiring up to ten photons for non-resonant ionisation. The relative sensitivity factors (RSF) have been determined as a function of the laser intensity and it has been demonstrated that for molecules with very different masses and ionisation potentials, uniform ionisation has been achieved at the highest laser intensities. Quantitative laser mass spectrometry of molecules is therefore a distinct possibility. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
102.
Gwendolyn Cramer Robert Lewis Ashley Gymarty Sarah Hagan Michela Mickler Sydney Evans Salman R. Punekar Lee Shuman Charles B. Simone II Stephen M. Hahn Theresa M. Busch Douglass Fraker Keith A. Cengel 《Photochemistry and photobiology》2020,96(3):684-691
Peritoneal carcinomatosis (PC) can occur as an advanced consequence of multiple primary malignancies. Surgical resection, radiation or systemic interventions alone have proven inadequate for this aggressive cancer presentation, since PC still has a poor survival profile. Photodynamic therapy (PDT), in which photosensitive drugs are exposed to light to generate cytotoxic reactive oxygen species, may be an ideal treatment for PC because of its ability to deliver treatment to a depth appropriate for peritoneal surface tumors. Additionally, epidermal growth factor receptor (EGFR) signaling plays a variety of roles in cancer progression and survival as well as PDT-mediated cytotoxicity, so EGFR inhibitors may be valuable in enhancing the therapeutic index of intraperitoneal PDT. This study examines escalating doses of benzoporphyrin derivative (BPD)-mediated intraperitoneal PDT combined with the EGFR-inhibitor cetuximab in a canine model. In the presence or absence of small bowel resection (SBR) and cetuximab, we observed a tolerable safety and toxicity profile related to the light dose received. Additionally, our findings that BPD levels are higher in the small bowel compared with other anatomical regions, and that the risk of anastomotic failure decreases at lower light doses will help to inform the design of similar PC treatments in humans. 相似文献
103.
Dr. Sylvain David Hao-Jung Chang Dr. Cesar Lopes Carl Brännlund Dr. Boris Le Guennic Dr. Gérard Berginc Prof. Eric Van Stryland Dr. Mykailo V. Bondar Prof. David Hagan Prof. Denis Jacquemin Dr. Chantal Andraud Dr. Olivier Maury 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(10):3517-3525
Aza-boron dipyrromethenes (aza-BODIPYs) presenting a benzothiadiazole substitution on upper positions are described. The strong electron-withdrawing effect of the benzothiadiazole moiety permits enhancement of the accepting strength and improves the delocalization of the aza-BODIPY core to attain a significant degree of electronic communication between the lower donating groups and the upper accepting groups. The nature of the intramolecular charge transfer is studied both experimentally and theoretically. Linear spectroscopy highlighted the strongly redshifted absorption and emission of the synthesized molecules with recorded fluorescence spectra over 1000 nm. Nonlinear optical properties were also investigated. Strong enhancement of the two-photon absorption of the substituted dyes compared with the unsubstituted one (up to 4520 GM at 1300 nm) results in an approximately 15–20 % improvement of the optical power limiting performances. These dyes are therefore a good starting point for further improvement of optical power limiting in the short-wave IR range. 相似文献
104.
Peceli D Webster S Fishman DA Cirloganu CM Hu H Przhonska OV Kurdyukov VV Slominsky YL Tolmachev AI Kachkovski AD Dasari RR Barlow S Marder SR Hagan DJ Van Stryland EW 《The journal of physical chemistry. A》2012,116(20):4833-4841
The double pump-probe technique (DPP), first introduced by Swatton et al. [Appl. Phys. Lett. 1997, 71, 10], is a variant of the standard pump-probe method but uses two pumps instead of one to create two sets of initial conditions for solving the rate equations, allowing a unique determination of singlet- and triplet-state absorption parameters and transition rates. We investigate the advantages and limitations of the DPP theoretically and experimentally and determine the influence of several experimental parameters on its accuracy. The accuracy with which the DPP determines the triplet-state parameters improves when the fraction of the population in the triplet state relative to the ground state is increased. To simplify the analysis of the DPP, an analytical model is presented, which is applicable to both the reverse saturable and the saturable absorption regimes. We show that the DPP is optimized by working in the saturable absorption regime. Although increased accuracy is in principle achievable by increasing the pump fluence in the reverse saturable absorption range, this can cause photoinduced decomposition in photochemically unstable molecules. Alternatively, we can tune the excitation wavelength to the spectral region of larger ground-state absorption, to achieve similar accuracy. This results in an accurate separation of triplet yield and excited-state absorption cross section. If the cross section at another wavelength is then desired, a second pump-probe experiment at that wavelength can be utilized given the previously measured triplet yield under the usually valid assumption that the triplet yield is independent of excitation wavelength. 相似文献
105.
Protein detection by nanopores equipped with aptamers 总被引:1,自引:0,他引:1
Rotem D Jayasinghe L Salichou M Bayley H 《Journal of the American Chemical Society》2012,134(5):2781-2787
Protein nanopores have been used as stochastic sensors for the detection of analytes that range from small molecules to proteins. In this approach, individual analyte molecules modulate the ionic current flowing through a single nanopore. Here, a new type of stochastic sensor based on an αHL pore modified with an aptamer is described. The aptamer is bound to the pore by hybridization to an oligonucleotide that is attached covalently through a disulfide bond to a single cysteine residue near a mouth of the pore. We show that the binding of thrombin to a 15-mer DNA aptamer, which forms a cation-stabilized quadruplex, alters the ionic current through the pore. The approach allows the quantification of nanomolar concentrations of thrombin, and provides association and dissociation rate constants and equilibrium dissociation constants for thrombin·aptamer interactions. Aptamer-based nanopores have the potential to be integrated into arrays for the parallel detection of multiple analytes. 相似文献
106.
A stochastic sensing method: Discrimination between enantiomeric amino acids is achieved when the amino acids bind to a Cu(II) complex within a protein nanopore sensor, which provides a chiral environment. The potential of the method is demonstrated by real-time observation of the increase in enantiomeric excess during an enzymatic kinetic resolution. 相似文献
107.
SNO patrol: S-Nitrosothiols (RSNO) are important molecules involved in cell signaling, which control physiological processes such as vasodilation and bronchodilation. By using the protein pore α-hemolysin as a nanoreactor, the biological chemistry of RSNO has been investigated at the single-molecule level. 相似文献
108.
109.
110.
In self-assembly processes, kinetic trapping effects often hinder the formation of thermodynamically stable ordered states. In a model of viral capsid assembly and in the phase transformation of a lattice gas, we show how simulations in a self-assembling steady state can be used to identify two distinct mechanisms of kinetic trapping. We argue that one of these mechanisms can be adequately captured by kinetic rate equations, while the other involves a breakdown of theories that rely on cluster size as a reaction coordinate. We discuss how these observations might be useful in designing and optimising self-assembly reactions. 相似文献