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251.
Otani Y Nagae O Naruse Y Inagaki S Ohno M Yamaguchi K Yamamoto G Uchiyama M Ohwada T 《Journal of the American Chemical Society》2003,125(49):15191-15199
Here we show that amides of bicyclic 7-azabicyclo[2.2.1]heptane are intrinsically nitrogen-pyramidal. Single-crystal X-ray diffraction structures of some relevant bicyclic amides, including the prototype N-benzoyl-7-azabicyclo[2.2.1]heptane, exhibited nitrogen-pyramidalization in the solid state. We evaluated the rotational barriers about the amide bonds of various N-benzoyl-7-azabicyclo[2.2.1]heptanes in solution. The observed reduction of the rotational barriers of the bicyclic amides, as compared with those of the monocyclic pyrrolidine amides, is consistent with a nitrogen-pyramidal structure of 7-azabicyclo[2.2.1]heptane amides in solution. A good correlation was found between the magnitudes of the rotational barrier of N-benzoyl-7-azabicyclo[2.2.1]heptanes bearing para-substituents on the benzoyl group and the Hammett's sigma(p)(+) constants, and this is consistent with the similarity of the solution structures. Calculations with the density functional theory reproduced the nitrogen-pyramidal structures of these bicyclic amides as energy minima. The calculated magnitudes of electron delocalization from the nitrogen nonbonding n(N) orbital to the carbonyl pi orbital of the amide group evaluated by application of the bond model theory correlated well with the rotational barriers of a variety of amides, including amides of 7-azabicyclo[2.2.1]heptane. The nonplanarity of the amide nitrogen of 7-azabicyclo[2.2.1]heptanes would be derived from nitrogen-pyramidalization due to the CNC angle strain and twisting of the amide bond due to the allylic strain. 相似文献
252.
Yoshinori Tominaga Yoshihide Shiroshita Tomohiko Kurokawa Yoshiro Matsuda Akira Hosomi 《Journal of heterocyclic chemistry》1988,25(1):185-189
1-Azacycl[3.2.2]azines were synthesized from 2-methylthioimidazo[1,2-a]pyridines, 2a and 2b , by using [2 + 8] cycloaddition reaction with dimethyl acetylenedicarboxylate as the key step. Synthesis of 1-azabenzo-[h]cycl[3.2.2]azine was also described. 相似文献
253.
Catalytic hydrogenolysis of methyl oleate to C18 alcohol is tested with a pulse reaction system under atomspheric pressure at 503 K over a series of hydrogen storage alloys. Mg2Cu alloy shows the highest efficiency and the yield of alcohol is about three times larger than the classical Cu–Cr–O catalyst.
-C18 503 K , . Mg2Cu Cu–Cr–O.相似文献
254.
The A-site ordered manganites show the charge/orbital order (CO) transition far above room temperature. By using this advantage, we have engaged in the realization of colossal magnetoresistance (CMR) at room temperature by introducing some sophisticated disorders to SmBaMn2O6. The inter-site disorder of Sm/Ba results in no significant magnetoresistance (MR) effect. The La-substitution for both Sm- and Ba-sites is effective to realize MR effect. At room temperature and 9 T, we have achieved the record of MR effect about 340% in the sintered Sm0.90La0.24Ba0.86Mn2O6. In a single crystal of the compound, the perfect CO insulator to ferromagnetic metal (FM) transition is observed at 9 T, showing the room temperature CMR over 1000%. TEM study reveals that the formation of microdomains with CO and FM or magnetic glassy states is crucial for CMR. 相似文献
255.
Tomohiko Nakajima Tetsuo Tsuchiya Toshiya Kumagai 《Journal of solid state chemistry》2009,182(9):2560-2565
We have studied pulsed laser-induced oxygen deficiencies at rutile TiO2 surfaces. The crystal surface was successfully reduced by excimer laser irradiation, and an oxygen-deficient TiO2−δ layer with 160 nm thickness was formed by means of ArF laser irradiation at 140 mJ/cm2 for 2000 pulses. The TiO2−δ layer fundamentally maintained a rutile structure, though this structure was distorted by many stacking faults caused by the large oxygen deficiency. The electrical resistivity of the obtained TiO2−δ layer exhibited unconventional metallic behavior with hysteresis. A metal–insulator transition occurred at 42 K, and the electrical resistivity exceeded 104 Ω cm below 42 K. This metal–insulator transition could be caused by bipolaronic ordering derived from Ti–Ti pairings that formed along the stacking faults. The constant magnetization behavior observed below 42 K is consistent with the bipolaronic scenario that has been observed previously for Ti4O7. These peculiar electrical properties are strongly linked to the oxygen-deficient crystal structure, which contains many stacking faults formed by instantaneous heating during excimer laser irradiation. 相似文献
256.
White light emitting phosphor RbVO3 films have been successfully fabricated by means of a vacuum ultraviolet (VUV) irradiation using an excimer lamp after spin coating of metal-organic solution onto substrates. The metal-organic carboxylates coated on substrates decomposed and reacted under the VUV irradiation. The metal-organic bonds were efficiently cleaved by the VUV illumination not only in air but also in vacuum, however, there was not a strong driving force for the reaction process to the formation of RbVO3 in the vacuum atmosphere. On the contrary, the reaction and crystallization simultaneously proceeded under photo-chemically produced active oxygen and/or ozone atmospheres due to the VUV illumination in air. The reaction between the photo-activated Rb-O and V-O species could be strongly enhanced by the oxidation atmospheres at the moment of the metal-organic bond cleavage under the VUV irradiation. 相似文献
257.
Tomohiko Nishiuchi Ryuoh Ito Aya Takada Yuri Yasuda Takaya Nagata Erik Stratmann Takashi Kubo 《化学:亚洲杂志》2019,14(10):1830-1836
Anthracene‐attached tricyclic aromatic hydrocarbon radicals having different central polygons, Ant‐5 , Ant‐6 , and Ant‐7 , were synthesized to evaluate the role of an anthracene substituent group in the stability and reactivity of tricyclic aromatic hydrocarbon radicals. The bulky anthryl group effectively protects a carbon atom with high spin density, resulting in high persistence of the radicals. On the other hand, the combination of the anthryl group and the tricyclic aromatic scaffold makes the molecular structure drastically change from a twisted form to a folded form and an unpaired electron moves into the anthryl moiety, eventually affording a tail‐to‐tail σ‐dimer. 相似文献
258.
Yasushi Yoshida Kazuki Omori Tomohiko Hiroshige Takashi Mino Masami Sakamoto 《化学:亚洲杂志》2019,14(15):2737-2743
Chiral functionalized aminals are important core structures of natural products and pharmaceuticals. Their chemo‐ and regioselective catalytic, asymmetric synthesis has been realized through the umpolung reaction of α‐imino amides using a catalyst we originally developed. Functionalized aminals were prepared with high chemoselectivity by treating a hemiaminal intermediate with pyridine in butanol. Evaluation of substrate scope revealed that this transformation could be achieved with a wide range of α‐imino amides to produce the desired products in high yields with up to 97 % ee. A mechanistic study suggested that aminal formation proceeded through the ring opening/ring closing equilibrium of the hemiaminal skeleton. 相似文献
259.
260.
We have found a form of copper(II) terephthalate that occluded an enormous amount of gases such as N2, Ar, O2, and Xe. Copper(II) terephthalate is the first metal complex found capable of adsorbing gases. This complex has opened a new field of adsorbent chemistry and is recognized as a leader in the construction of microporous metal complexes. In extending the route for the synthesis of microporous complexes, we obtained many new porous materials that are widely recognized as useful materials for applications in areas such as gas storage, molecular sieves, catalysis, inclusion complexes, and surface science. 相似文献