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41.
42.
X-ray spectra taken with good quality flat crystals can yield spatial resolution of small plasma sources at the expense of spectral resolution. 40 μm spatial resolution of a laser-produced aluminum plasma was obtained using lines of wavelength ~6 Å. 相似文献
43.
Loveridge-Smith A Allen A Belak J Boehly T Hauer A Holian B Kalantar D Kyrala G Lee RW Lomdahl P Meyers MA Paisley D Pollaine S Remington B Swift DC Weber S Wark JS 《Physical review letters》2001,86(11):2349-2352
We have used x-ray diffraction with subnanosecond temporal resolution to measure the lattice parameters of orthogonal planes in shock compressed single crystals of silicon (Si) and copper (Cu). Despite uniaxial compression along the (400) direction of Si reducing the lattice spacing by nearly 11%, no observable changes occur in planes with normals orthogonal to the shock propagation direction. In contrast, shocked Cu shows prompt hydrostaticlike compression. These results are consistent with simple estimates of plastic strain rates based on dislocation velocity data. 相似文献
44.
45.
Darshan C Kundaliya Reeta Vij AA Tulapurkar U Vaidya R Pinto RG Kulkarni 《Pramana》2002,58(5-6):1041-1044
Electrical resistance (R) measurements of a bulk La0.33Nd0.33Ca0.33MnO3 perovskite in magnetic fields up to 40 kOe have revealed anomalous temperature hysteretic effects both in 0 Oe and 20 kOe
magnetic fields. The sharp peak observed in the R vs. T plot indicates the occurrence of metal-to-insulator (M-I) transition at a temperature of T
MI=110 K and 140 K, for cooling and warming paths, respectively. An applied magnetic field of 20 kOe reduces the resistance
and shifts T
MI to 160 K and 185 K for cooling and warming, respectively. We have observed a much higher resistance in the cooling path than
in the warming path leading to the hysteretic resistance ratio (R
cool/R
warm) of 200 at 110 K and 1.8 at 160 K for 0 Oe and 20 kOe, respectively. Record values of colossal magnetoresistance (CMR) have
been achieved. The CMR value reaches nearly 99% in the temperature ranges of 90 K to 140 K and 90 K to 170 K for 20 kOe and
40 kOe magnetic fields in the cooling mode, respectively. The observed unusual behavior is attributed to the co-existence
of La-rich and Nd-rich domains assumed to be distributed randomly in the compound. 相似文献
46.
We have studied the peak effect (PE) phenomenon in single crystals of weakly pinned superconductors CeRu2 and 2H-NbS2. 2H-NbS2 is iso-structural and iso-electronic to 2H-NbSe2, whose similarity with CeRu2 as regards the PE representing the order-to-disorder transformation of the flux line lattice was claimed some time ago. We
report on the step change in equilibrium magnetization across the peak effect in CeRu2. We also present the vortex phase diagram of 2H-NbS2 obtained from the magnetization data, and compare the PE phenomenon in 2H-NbS2 and 2H-NbSe2. 相似文献
47.
Savolainen J Dijkhuizen N Fanciulli R Liddell PA Gust D Moore TA Moore AL Hauer J Buckup T Motzkus M Herek JL 《The journal of physical chemistry. B》2008,112(9):2678-2685
A caroteno-purpurin dyad molecule was studied by steady-state and pump-probe spectroscopies to resolve the excited-state deactivation dynamics of the different energy levels as well as the connecting energy flow pathways and corresponding rate constants. The data were analyzed with a two-step multi-parameter global fitting procedure that makes use of an evolutionary algorithm. We found that following ultrafast excitation of the donor (carotenoid) chromophore to its S2 state, the energy flows via two channels: energy transfer (70%) and internal conversion (30%) with time constants of 54 and 110 fs, respectively. Additionally, some of the initial excitation is found to populate the hot ground state, revealing another limitation to the functional efficiency. At later times, a back transfer occurs from the purpurin to the carotenoid triplet state in nanosecond timescales. Details of the energy flow within the dyad as well as species associated spectra are disentangled for all excited-state and ground-state species for the first time. We also observe oscillations with the most pronounced peak on the Fourier transform spectrum having a frequency of 530 cm(-1). The dyad mimics the dynamics of the natural light-harvesting complex LH2 from Rhodopseudomonas acidophila and is hence a good model system to be used in studies aimed to further explain previous work in which the branching ratio between the competing pathways of energy loss and energy transfer could be manipulated by adaptive femtosecond pulse shaping. 相似文献
48.
A Monolithic Hybrid Cellulose‐2.5‐Acetate/Polymer Bioreactor for Biocatalysis under Continuous Liquid–Liquid Conditions Using a Supported Ionic Liquid Phase 下载免费PDF全文
Bernhard Sandig Lukas Michalek Sandra Vlahovic Mihaela Antonovici Prof. Bernhard Hauer Prof. Michael R. Buchmeiser 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(44):15835-15842
Mesoporous monolithic hybrid cellulose‐2.5‐acetate (CA)/polymer supports were prepared under solvent‐induced phase separation conditions using cellulose‐2.5‐acetate microbeads 8–14 μm in diameter, 1,1,1‐tris(hydroxymethyl)propane and 4,4′‐methylenebis(phenylisocyanate) as monomers as well as THF and n‐heptane as porogenic solvents. 4‐(Dimethylamino)pyridine and dibutyltin dilaurate (DBTDL), respectively, were used as catalysts. Monolithic hybrid supports were used in transesterification reactions of vinyl butyrate with 1‐butanol under continuous, supported ionic liquid–liquid conditions with Candida antarctica lipase B (CALB) and octylmethylimidazolium tetrafluoroborate ([OMIM+][BF4?]) immobilized within the CA beads inside the polymeric monolithic framework and methyl tert‐butyl ether (MTBE) as the continuous phase. The new hybrid bioreactors were successfully used in dimensions up to 2×30 cm (V=94 mL). Under continuous biphasic liquid–liquid conditions a constant conversion up to 96 % was achieved over a period of 18 days, resulting in a productivity of 58 μmol mg?1(CALB) min?1. This translates into an unprecedented turnover number (TON) of 3.9×107 within two weeks, which is much higher than the one obtained under standard biphasic conditions using [OMIM+][BF4?]/MTBE (TON=2.7×106). The continuous liquid–liquid setup based on a hybrid reactor presented here is strongly believed to be applicable to many other enzyme‐catalyzed reactions. 相似文献
49.
T. Mančal O. Bixner N. Christensson J. Hauer F. Milota A. Nemeth J. Sperling H.F. Kauffmann 《Procedia Chemistry》2011,3(1):105-117
Electronic and nuclear molecular wavepackets are a clear manifestation of the wavelike properties of matter at the very heart of quantum mechanics. In this work we demonstrate how electronic two-dimensional spectroscopy (2D) serves as a highly evolved tool for the simultaneous investigation of both phenomena. In further analysis and theoretical treatments, 2D spectra form an ideal basis for the discussion of electronic decoherence, vibrational relaxation and electron-phonon coupling. 相似文献
50.
In this article, we prove that the following weighted Hardy inequality $$\begin{array}{ll}\big(\frac{|{d-p}|}{p}\big)^{p}\, \int\limits_{\Omega}\, \frac{|{u}|^{p}}{|{x}|^{p}}\;d\mu \\ \quad \quad \le \int\limits_{\Omega}\,|{\nabla u}|^{p}\;d\mu+ \big(\frac{|{d-p}|}{p}\big)^{p-1}\,\textrm{sgn}(d-p)\,\int\limits_{\Omega}|{u}|^{p}\,\frac{(x^{t}Ax)^{p/2}}{|{x}|^{p}}\; d\mu \quad \quad \quad (1) \end{array}$$ holds with optimal Hardy constant ${\big(\frac{|d-p|}{p}\big)^{p}}$ for all ${u \in W^{1,p}_{\mu,0}(\Omega)}$ if the dimension d ≥ 2, 1 < p < d, and for all ${u \in W^{1,p}_{\mu,0}(\Omega{\setminus}\{0\})}$ if p > d ≥ 1. Here we assume that Ω is an open subset of ${\mathbb{R}^{d}}$ with ${0 \in \Omega}$ , A is a real d × d-symmetric positive definite matrix, c > 0, and $$ d \mu: = \rho(x) \,dx \qquad \textrm{with} \quad \rho(x) = c \cdot \exp(-\frac{1}{p}(x^{t}Ax)^{p/2}), \quad x \in\Omega.\quad \quad (2) $$ If p > d ≥ 1, then we can deduce from (1) a weighted Poincaré inequality on ${W^{1,p}_{\mu,0}(\Omega \setminus\{0\})}$ . Due to the optimality of the Hardy constant in (1), we can establish the nonexistence (locally in time) of positive weak solutions of a p-Kolmogorov parabolic equation perturbed by a singular potential in dimension d = 1, for 1 < p < + ∞, and when Ω = ]0, + ∞[. 相似文献