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991.
The effect of counterion types on the structure of Cu(II) complexes of imidazole and poly-4(5)-vinylimidazole in aqueous solution was studied by spectroscopic and electron spin resonance (ESR) techniques. Visible and ESR spectra of both complexes in aqueous solution containing NaClO4, KNO3, KC1, and KBr showed only a slight change from each other in the presence of different counterions. On the other hand, the frequency of the center of absorption band in the visible region (λmax) and ESR parameters of the complex in aqueous solution did not correspond to those reported for its crystalline state, and in addition, those of the polymeric Cu(II) complex were different from those of the low molecular weight Cu(II) complex. It was proposed that in aqueous solution, water molecules are coordinated to the axial position of the complex where counterion molecules are present in the crystalline state, and that the structure of the polymeric Cu(II) complex is different from that of the low molecular weight Cu(II) complex due to steric hindrance of the polymeric ligand. 相似文献
992.
Shuchi Gupta Dr. Stephen V. Kershaw Dr. Andrei S. Susha Tai Lun Wong Prof. Koichi Higashimine Prof. Shinya Maenosono Prof. Andrey L. Rogach 《Chemphyschem》2013,14(12):2853-2858
Whereas CdSe nanorods that are grown in organic solution have a hexagonal wurtzite structure, which is the limiting case for exchange, HgSe is more commonly encountered as a cubic zinc blende system. An exchange process was performed at room temperature and at atmospheric pressure in an aqueous environment after phase transfer of the original CdSe nanorods, which reinforced the tendency for the endpoint of HgSe to be cubic. Consequently, we observed that under ambient conditions, the exchange process terminated with an average composition of only Cd0.9Hg0.1Se. Following the changes during the process by optical spectroscopy and high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM), we observed that the Hg2+ ions diffused into the rods to a point limited by the formation of stacking faults due to the different lattice structures of the two limiting cases of zinc blende and wurtzite. HAADF‐STEM and energy dispersive spectroscopy analyses also confirmed that the Hg substitution did not occur uniformly throughout the individual nanorods, as Hg‐poor and Hg‐rich regions coexist around the stacking faults. The formation of near‐infrared‐emitting alloyed CdxHg1?xSe nanorods in an aqueous medium highlights the subtle dependence of the ion‐exchange process on the differences in the crystal structures of the two endpoint lattices. 相似文献
993.
We recently found that [Eu(pda)2]? (pda: 1,10‐phenanthroline‐2,9‐dicarboxylic acid), which has an achiral structure in crystals, exhibits circularly polarized luminescence (CPL) in aqueous solutions containing chiral amino acids such as arginine and histidine. CPL measurements were performed for agar gel, which includes an aqueous solution of [Eu(pda)2]? and chiral arginine or histidine. The spectral shape, concentration, and pH dependences on CPL intensity in the agar gels were very close to those in aqueous solutions, indicating that the CPL of the EuIII complex in the agar gels was induced by mechanism similar to that in aqueous solutions. We performed spatially resolved CPL measurements using a laboratory‐built microscopic CPL spectroscopic system for agar‐gel samples, where d ‐ and l ‐ amino acids were separately dispersed. We successfully recorded CPL imaging maps showing spatial dispersions of d ‐ and l ‐amino acid in the agar gels. 相似文献
994.
Koichi Mitsudo Ren Matsuo Toki Yonezawa Haruka Inoue Hiroki Mandai Seiji Suga 《Angewandte Chemie (International ed. in English)》2020,59(20):7803-7807
The first electrochemical dehydrogenative C?S bond formation leading to thienoacene derivatives is described. Several thienoacene derivatives were synthesized by dehydrogenative C?H/S?H coupling. The addition of nBu4NBr, which catalytically promoted the reaction as a halogen mediator, was essential. 相似文献
995.
Keiichi Kato Norio Koine Yoshiyuki Imai Koichi Akiyama Takuya Sugahara 《Journal of Dispersion Science and Technology》2013,34(8):1217-1222
The molecular compositions of the commercial nonionic surfactants Span 80 and Span 85 were analyzed by reversed phase high performance liquid chromatography (HPLC). Both surfactants are mixtures of fatty acid esters, containing monoesters, diesters, triesters, and tetraesters. While diesters dominate in the case of Span 80, Span 85 contains mainly tetraesters. Vesicles were prepared from Span 80 (or Span 85) by a two‐step emulsification method that involved homogenization and separation steps in which a portion of the surfactants was removed. The composition of the vesicles was analyzed by HPLC with respect to the different esters present. Although commercial Span 80 and Span 85 differ considerably in their molecular compositions, the ester profiles of the vesicles formed were in both cases rather similar and dominated by diesters. Therefore, the particular vesicle preparation method leads to a molecular selection of mainly those components that are prone to form bilayers. 相似文献
996.
Ryoji Sugimura Shuichi Suzuki Masatoshi Kozaki Kazutoshi Keyaki Koichi Nozaki Hironori Matsushita Noriaki Ikeda Keiji Okada 《Research on Chemical Intermediates》2013,39(1):185-204
Two triads (i.e., 3PTZ–Pt–MNDI and 10PTZ–Pt–MNDI) consisting of 3-phenothiazine (3PTZ) or 10-phenothiazine (10PTZ), bipyridine–diacetylide platinum complex (Pt), and naphthalene diimide (MNDI) chromophores linked by highly twisted biphenylene spacers have been prepared. The formation and decay of the charge-separated (CS) states in toluene were studied by use of picosecond and nanosecond laser photolysis via selective excitation of the Pt moiety. The time required for formation of the CS state, PTZ+–Pt–MNDI?, from PTZ–3Pt*–MNDI was determined to be τ CS = 280 ps for 3PTZ+–Pt–MNDI? and τ CS = 230 ps for 10PTZ+–Pt–MNDI?. The lifetimes of the CS states were determined to be τ CR1 = 75 ns (95 %) and τ CR2 = 285 ns (5 %) for 3PTZ+–Pt–MNDI? and τ CR = 830 ns for 10PTZ+–Pt–MNDI?. Formation and decay of the CS states are discussed in terms the Marcus theory and the spin-correlated radical pair mechanism. 相似文献
997.
998.
Shoji M Akiyama N Tsubone K Lash LL Sanders JM Swanson GT Sakai R Shimamoto K Oikawa M Sasaki M 《The Journal of organic chemistry》2006,71(14):5208-5220
Dysiherbaine (1) and its congener neodysiherbaine A (2) are naturally occurring excitatory amino acids with selective and potent agonistic activity for ionotropic glutamate receptors. We describe herein the total synthesis of 2 and its structural analogues 3-8. Advanced key intermediate 16 was employed as a branching point to assemble a series of these analogues 3-8 with respect to the C8 and C9 functionalities, which would not have been accessible through manipulations of the natural product itself. The synthesis of key intermediate 16 features (i) stereocontrolled C-glycosylation to set the C6 stereocenter, (ii) concise synthesis of the bicyclic ether skeleton through chemo- and stereoselective dihydroxylation of the exo-olefin and stereoselective epoxidation of the endo-olefin, followed by epoxide ring opening/5-exo ring closure, and (iii) catalytic asymmetric hydrogenation of enamide ester to construct the amino acid appendage. A preliminary biological evaluation of analogues for their in vivo toxicity against mice and binding affinity for glutamate receptors showed that both the type and stereochemistry of the C8 and C9 functional groups affected the subtype selectivity of dysiherbaine analogues for members of the kainic acid receptor family. 相似文献
999.
Gold-catalyzed intermolecular reaction leading to dihydronaphthalene derivatives in one pot from two equivalents of ynones with respect to styrene is uncovered. The [4+2] Diels–Alder cycloaddition of ynones and styrenes is catalyzed by a mono-gold(I) complex and the conjugated acid to provide an unstable 3,8a-dihydronaphthalene to subsequently undergo an intermolecular ene-type reaction with the π-activated ynone to afford multi-component coupling dihydronaphthalene products. Linear relationships between chiral ligand-gold complexes and chiral dihydronaphthalene products proves mono-gold catalysis that triggers an asymmetric tandem Diels–Alder and ene reaction sequence. 相似文献
1000.
Determination of estazolam in plasma by high-performance liquid chromatography with solid-phase extraction. 总被引:1,自引:0,他引:1
Masatomo Miura Tadashi Ohkubo Kazunobu Sugawara Naoyuki Okuyama Koichi Otani 《Analytical sciences》2002,18(5):525-528
A high-performance liquid chromatography (HPLC) assay was developed for the determination of estazolam in human plasma. Estazolam and alprazolam as an internal standard were detected by ultraviolet absorbance at 240 nm. Estazolam in plasma was extracted by a rapid and simple procedure based on cyanopropyl bonded-phase extraction. Chromatographic separation was achieved with a reversed-phase C8-5 column using a mobile phase of 0.5% potassium dihydrogenphosphate(pH 4.5)-acetonitrile (70:30, v/v). The determination of estazolam was possible in the concentration range of 1.0 - 200.0 ng/mL. The mean recovery of estazolam added to plasma was 96.1 +/- 1.5% with coefficients of variation of less than 5.5%. This method is applicable for accurately monitoring the plasma level of estazolam in healthy subjects participating in scientific research. 相似文献