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991.
Takehiro Yamamoto Yousuke Nakamura Atsushi Yamashita Takamasa Hashimoto Noriyasu Mori 《Rheologica Acta》2006,45(3):250-259
Viscous fingering in surfactant solutions in a rectangular Hele–Shaw cell was investigated. Test fluids were aqueous solutions
of cetyltrimethylammonium bromide (CTAB) with sodium salicylate (NaSal) as a counter ion, and the ratio of mole concentration
of CTAB and that of NaSal was 1–7.7. Two fluids that had a mole concentration different from that of CTAB were used. Air was
injected into the cell and the growth of the interface between air and a CTAB/NaSal solution was observed. The fingertip grew
similar to the finger growth in shear-thinning fluids at low pressure gradients. It took a cuspidate shape at the intermediate
pressure gradient, and a sudden protrusion at a critical shear rate occurred. In high shear rate regions, the finger behaved
as in a less shear-thinning fluid. These phenomena relate to rheological properties of the test fluids. Comparison with flow
curves for CTAB/NaSal systems showed that the critical shear rate related to the shear rate at which a bending point appeared
in the flow curve. 相似文献
992.
Tetsuo Suami Tsuguhiro Kato Kazuaki Kanai Shuichi Ohki Hideyo Yamashita 《Journal of carbohydrate chemistry》2013,32(3):417-427
Abstract 2-Chloroethylnitrosourea derivatives of sucrose have been synthesized as potential antineoplastic agents. Two compounds: 6-[[[(2-chloroethyl)nitrosoamino]carbonyl]amino]-6-deoxysucrose and 6′-[[[(2-chloroethyl)nitrosoamino]carbonyl]amino]-6′-deoxysucrose exhibited significant antitumor activity against experimental leukemia L1210 in mice. Their chemical decomposition rates (T0.5) have been determined. 相似文献
993.
Kazuya Ishigai Prof. Dr. Haruhiko Fuwa Keisuke Hashizume Ryo Fukazawa Dr. Yuko Cho Prof. Dr. Mari Yotsu‐Yamashita Prof. Dr. Makoto Sasaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(17):5276-5288
In this study, we report the first total synthesis and complete stereostructure of gambieric acid A, a potent antifungal polycyclic ether metabolite, in detail. The A/B‐ring exocyclic enol ether 32 was prepared through a Suzuki–Miyaura coupling of the B‐ring vinyl iodide 18 and the alkylborate 33 and subsequent closure of the A‐ring by using diastereoselective bromoetherification as the key transformation. Suzuki–Miyaura coupling of 32 with acetate‐derived enol phosphate 49 , followed by ring‐closing metathesis of the derived diene, produced the D‐ring. Subsequent closure of the C‐ring through a mixed thioacetalization completed the synthesis of the A/BCD‐ring fragment 8 . The A/BCD‐ and F′GHIJ‐ring fragments (i.e., 8 and 9 ) were assembled through Suzuki–Miyaura coupling. The C25 stereogenic center was elaborated by exploiting the intrinsic conformational property of the seven‐membered F′‐ring. After the oxidative cleavage of the F′‐ring, the E‐ring was formed as a cyclic mixed thioacetal (i.e., 70 ) and then stereoselectively allylated by using glycosylation chemistry. Ring‐closing metathesis of the diene 3 thus obtained closed the F‐ring and completed the polycyclic ether skeleton. Finally, the J‐ring side chain was introduced by using a Julia–Kocienski olefination in the presence of CeCl3 to complete the total synthesis of gambieric acid A ( 1 ), thereby unambiguously establishing its complete stereostructure. The present total synthesis enabled us to evaluate the antifungal and antiproliferative activities of 1 and several synthetic analogues. 相似文献
994.
Syntheses and Structure of Hexacoordinated Selenium (λ6-Selane) and Tellurium (λ6-Tellane) Compounds
Soichi Sato Takeshi Ueminami Takahiro Yamashita Hiroshi Arakawa Ernst Horn Ohgi Takahashi 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):595-598
The first isolation of bis(2,2′-biphenylylene)dichloro- and difluoro-perchalcogenuranes, [12–Se–6(C4F2)] (λ6-selane); [12–Te–6(C4X2), X = Cl, F] (λ6-tellane) and the corresponding tellurane Te-oxide dimer [12–Te–6(C4O2)]2, and their crystal and molecular structures are described. Furthermore, on the basis of the difference between the 3c-4e bonds of the dodecet species and that of the decet species a new molecular orbital concept has been proposed on the 3c-4e bond of perchalcogenurane species [12–M–6, M = chalcogen atoms]. 相似文献
995.
Satoshi Morita Hiroshi Inoue Natsuki Yamashita Toshihisa Maeshima 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(5):1003-1015
Polymerizabilities of several polar vinyl monomers in the presence of imidazole (Im) have been studied in CDC13 and CD3OD by NMR spectra. Acrylic acid formed a bimolecular adduct with Im as the initial adduct, while methacrylic acid was not obtained, On the other hand, methyl acrylate, methyl methacrylate (MMA), acrylamide (AAm), and acrylonitrile formed the initial adduct between Im and monomer, respectively. In these monomers, AAm and MMA gave each polymer in tetrahydrofuranat room temperature. The number-average molecular weight ([Mbar]n) of AAm polymers was determined to be in the range of 1000 to 1500, and the [Mbar]n of MMA polymers was found to be in the range of 2500 to 4500, The rate of polymerization Rp was expressed by the equations Rp = k[Im][AAm] and Rp = k[Im] [MMA]2, respectively. The activation energy ER was obtained by Arrheniuss's plots as ER(AAm) = 9.6 kcal/mol and ER(MMA) = 3.8 kcal/mol. These polymerization mechanisms are discussed on the basis of these results. 相似文献
996.
Yu Yamashita Ekaterina V. Vinogradova Xiaoyu Zhang Radu M. Suciu Benjamin F. Cravatt 《Angewandte Chemie (International ed. in English)》2020,59(10):3896-3899
Target engagement assays are crucial for establishing the mechanism‐of‐action of small molecules in living systems. Integral membrane transporters can present a challenging protein class for assessing cellular engagement by small molecules. The chemical proteomic discovery of alpha‐chloroacetamide (αCA) compounds that covalently modify cysteine‐54 (C54) of the MPC2 subunit of the mitochondrial pyruvate carrier (MPC) is presented. This finding is used to create an alkyne‐modified αCA, YY4‐yne, that serves as a cellular engagement probe for MPC2 in click chemistry‐enabled western blotting or global mass spectrometry‐based proteomic experiments. Studies with YY4‐yne revealed that UK‐5099, an alpha‐cyanocinnamate inhibitor of the MPC complex, engages MPC2 with remarkable selectivity in human cells. These findings support a model where UK‐5099 inhibits the MPC complex by binding to C54 of MPC2 in a covalent reversible manner that can be quantified in cells using the YY4‐yne probe. 相似文献
997.
998.
Control of the Single‐Molecule Magnet Behavior of Lanthanide‐Diarylethene Photochromic Assemblies by Irradiation with Light 下载免费PDF全文
Dr. Dawid Pinkowicz Min Ren Prof. Li‐Min Zheng Saki Sato Prof. Miki Hasegawa Dr. Masakazu Morimoto Prof. Masahiro Irie Prof. Brian K. Breedlove Dr. Goulven Cosquer Dr. Keiichi Katoh Prof. Masahiro Yamashita 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(39):12502-12513
Lanthanide‐based extended coordination frameworks showing photocontrolled single‐molecule magnet (SMM) behavior were prepared by combining highly anisotropic DyIII and HoIII ions with the carboxylato‐functionalized photochromic molecule 1,2‐bis(5‐carboxyl‐2‐methyl‐3‐thienyl)perfluorocyclopentene (H2dae), which acts as a bridging ligand. As a result, two new compounds of the general formula [{LnIII2(dae)3(DMSO)3(MeOH)} ? 10 M eOH]n (M=Dy for 1 a and Ho for 2 ) and two additional pseudo‐polymorphs [{DyIII2(dae)3(DMSO)3(H2O)} ? x MeOH]n ( 1 b ) and [{DyIII2(dae)3(DMSO)3(DMSO)} ? x MeOH]n ( 1 c ) were obtained. All four compounds have 2D coordination‐layer topologies, in which carboxylate‐bridged Ln2 units are linked together by dae2? anions into grid‐like frameworks. All four compounds exhibited a strong reversible photochromic response to UV/Vis light. Moreover, both 1 a and 2 show field‐induced SMM behavior. The slow magnetic relaxation of 1 a is influenced by the photoisomerization reaction leading to the observation of the cross‐effect: photocontrolled SMM behavior. 相似文献
999.
Hydrophobic Modification of Pd/SiO2@Single‐Site Mesoporous Silicas by Triethoxyfluorosilane: Enhanced Catalytic Activity and Selectivity for One‐Pot Oxidation 下载免费PDF全文
Kazuki Nakatsuka Prof. Dr. Kohsuke Mori Dr. Shusuke Okada Shohei Ikurumi Prof. Dr. Takashi Kamegawa Prof. Dr. Hiromi Yamashita 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(27):8348-8354
To enhance the catalytic activity in a selective one‐pot oxidation using in‐situ generated H2O2, a hydrophobically modified core–shell catalyst was synthesized by means of a simple silylation reaction using the fluorine‐containing silylation agent triethoxyfluorosilane (TEFS, SiF(OEt)3). The catalyst consisted of a Pd‐supported silica nanosphere and a mesoporous silica shell containing isolated TiIV and F ions bonded with silicon (Si?F bond). Structural analyses using XRD and N2 adsorption–desorption suggested that the mesoporous structure and large surface area of the mesoporous shells were retained even after the modification. During the one‐pot oxidation of sulfide, catalytic activity was enhanced significantly by increasing the amount of fluorine in the shell. A hydrophobic surface enhanced adsorption of the hydrophobic reactant into the mesopore, while the less hydrophobic oxygenated products efficiently diffused into the outside of the shell, which improved the catalytic activity and selectivity. In addition, the present methodology can be used to enhance the catalytic activity and selectivity in the one‐pot oxidation of cyclohexane by using an Fe‐based core–shell catalytic system. 相似文献
1000.
Simple, economical, and environmentally friendly method to synthesize 2-alkylbenzimidazoles was developed by modifying the conventional method between o-phenylenediamine and aldehyde. 相似文献