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971.
Felix Houard Quentin Evrard Guillaume Calvez Yan Suffren Carole Daiguebonne Olivier Guillou Frdric Gendron Boris Le Guennic Thierry Guizouarn Vincent Dorcet Matteo Mannini Kevin Bernot 《Angewandte Chemie (International ed. in English)》2020,59(2):780-784
We report a single‐chain magnet (SCM) made of a terbium(III) building block and a nitronyl‐nitroxide radical (NIT) functionalized with an aliphatic chain. This substitution is targeted to induce a long‐range distortion of the polymeric chain and accordingly it gives rise to chains that are curled with almost 20 nm helical pitch. They self‐organize as a chiral tubular superstructure made of 11 chains wound around each other. The supramolecular tubes have a 4.5 nm internal diameter. Overall, this forms a porous chiral network with almost 44 % porosity. Ab initio calculations highlight that each TbIII ion possesses high magnetic anisotropy. Indeed, notwithstanding the supramolecular arrangement each chain behaves as a SCM. Magnetic relaxation with both finite and infinite‐size regimes is observed and confirms the validity of the Ising approximation. This is associated with quite strong coercive field and magnetic remanence (Hc=2400 Oe MR=2.09 μB at 0.5 K) for this class of compounds. 相似文献
972.
Stphanie Norsikian Cedric Tresse Marc Franois‐Eude Louis Jeanne‐Julien Guillaume Masson Vincent Servajean Grgory Genta‐Jouve Jean‐Marie Beau Emmanuel Roulland 《Angewandte Chemie (International ed. in English)》2020,59(16):6612-6616
A total synthesis of tiacumicin B, a natural macrolide whose remarkable antibiotic properties are used to treat severe intestinal infections, is reported. The strategy is in part based on the prior synthesis of the tiacumicin B aglycone, and on the decisive use of sulfoxides as anomeric leaving groups in hydrogen‐bond‐mediated aglycone delivery (HAD). This new HAD variant permitted highly β‐selective rhamnosylation and noviosylation. To increase convergence, the rhamnosylated C1–C3 fragment thus obtained was anchored to the C4–C19 aglycone fragment by adapting the Suzuki–Miyaura cross‐coupling used for the aglycone synthesis. Ring‐size‐selective macrolactonization provided a compound engaged directly in the noviolysation step with virtually total β selectivity. The final efficient removal of all the protecting groups provided synthetic tiacumicin B. 相似文献
973.
Indrek Kalvet Kristina Deckers Dr. Ignacio Funes-Ardoiz Guillaume Magnin Theresa Sperger Marius Kremer Prof. Dr. Franziska Schoenebeck 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(20):7795-7799
Contrary to the general belief that Pd-catalyzed cross-coupling at sites of severe steric hindrance are disfavored, we herein show that the oxidative addition to C−Br ortho to an adamantyl group is as favored as the corresponding adamantyl-free system due to attractive dispersion forces. This enabled the development of a fully selective arylation and alkylation of C−Br ortho to an adamantyl group, even if challenged with competing non-hindered C−OTf or C−Cl sites. The method makes use of an air-stable PdI dimer and enables straightforward access to diversely substituted therapeutically important adamantylarenes in 5–30 min. 相似文献
974.
Dr. Chen Zhang Dr. Pierre-Yves Fortin Guillaume Barnoin Xue Qin Xing Wang Dr. Alvaro Fernandez Alvarez Dr. Christian Bijani Dr. Marie-Lise Maddelein Dr. Catherine Hemmert Dr. Olivier Cuvillier Prof. Dr. Heinz Gornitzka 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(29):12160-12166
975.
Sebastian Leubner Robert Stäglich Julia Franke Jannick Jacobsen Jonas Gosch Dr. Renée Siegel Dr. Helge Reinsch Prof. Dr. Guillaume Maurin Prof. Dr. Jürgen Senker Dr. Pascal G. Yot Prof. Dr. Norbert Stock 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(17):3877-3883
Herein is reported the utilization of acetonitrile as a new solvent for the synthesis of the three significantly different benchmark metal–organic frameworks (MOFs) CAU-10, Ce-UiO-66, and Al-MIL-53 of idealized composition [Al(OH)(ISO)], [Ce6O4(OH)4(BDC)6], and [Al(OH)(BDC)], respectively (ISO2−: isophthalate, BDC2−: terephthalate). Its use allowed the synthesis of Ce-UiO-66 on a gram scale. While CAU-10 and Ce-UiO-66 exhibit properties similar to those reported elsewhere for these two materials, the obtained Al-MIL-53 shows no structural flexibility upon adsorption of hydrophilic or hydrophobic guest molecules such as water and xenon and is stabilized in its large-pore form over a broad temperature range (130–450 K). The stabilization of the large-pore form of Al-MIL-53 was attributed to a high percentage of noncoordinating −COOH groups as determined by solid-state NMR spectroscopy. The defective material shows an unusually high water uptake of 310 mg g−1 within the range of 0.45 to 0.65 p/p°. In spite of showing no breathing effect upon water adsorption it exhibits distinct mechanical properties. Thus, mercury intrusion porosimetry studies revealed that the solid can be reversibly forced to breathe by applying moderate pressures (≈60 MPa). 相似文献
976.
977.
978.
Stephanie Seel Dr. Guillaume Dagousset Dr. Tobias Thaler Annette Frischmuth Prof. Dr. Konstantin Karaghiosoff Prof. Dr. Hendrik Zipse Prof. Dr. Paul Knochel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(14):4614-4622
We have developed a practical stereoretentive iodine/lithium‐exchange process that allows the stereodefined preparation of cis‐ and trans‐cycloalkyllithium compounds from their corresponding stereodefined iodides. Quenching with electrophiles offers stereospecific access to both cis‐ (up to 96 % cis) and trans‐cycloalkyl derivatives (up to 99 % trans). A detailed study of the thermodynamic stabilities, stereochemical behavior, and reactivities of axially and equatorially substituted cyclohexyllithium reagents is reported. Ab initio calculations demonstrate that the formation of oligomeric cyclohexyllithium structures is pivotal for explaining the observed stereochemical preference. 相似文献
979.
Saad Sene Marc Reinholdt Dr. Guillaume Renaudin Dr. Dorothée Berthomieu Prof. Claudio M. Zicovich‐Wilson Prof. Christel Gervais Dr. Philippe Gaveau Prof. Christian Bonhomme Dr. Yaroslav Filinchuk Prof. Mark E. Smith Prof. Jean‐Marie Nedelec Dr. Sylvie Bégu Dr. P. Hubert Mutin Dr. Danielle Laurencin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(3):797-797
980.
We consider the linear Schrödinger equation on a one dimensional torus and its time-discretization by splitting methods. Assuming a non-resonance condition on the stepsize and a small size of the potential, we show that the numerical dynamics can be reduced over exponentially long time to a collection of two dimensional symplectic systems for asymptotically large modes. For the numerical solution, this implies the long time conservation of the energies associated with the double eigenvalues of the free Schrödinger operator. The method is close to standard techniques used in finite dimensional perturbation theory, but extended here to infinite dimensional operators. 相似文献