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991.
992.
The pig liver esterase (PLE)-catalyzed kinetic resolution of half-esters derived from prochiral diesters is described. Generally, the PLE-catalyzed enantioselective hydrolysis of prochiral diesters affords the corresponding half-esters in high yield, because further hydrolysis of the half-esters does not typically occur. However, we found that some half-esters undergo PLE-catalyzed hydrolysis when they are gradually added to a PLE suspension in a potassium phosphate buffer at pH 8.0 via a syringe pump, leading to the kinetic resolution of the half-esters. 相似文献
993.
Kenichiro Todoroki Yasuhiro Ishii Koji Toyoda Takashi Ikawa Jun Zhe Min Koichi Inoue Shuji Akai Toshimasa Toyo’oka 《Analytical and bioanalytical chemistry》2013,405(25):8121-8129
In this paper, we report a new type of chiral high-performance liquid chromatography (HPLC) column—a so-called dress-up chiral column—featuring a chiral stationary phase adsorbed reversibly in a commercial fluorous HPLC column through fluorous interactions. We synthesized perfluroalkylated proline derivatives as chiral stationary phase compounds and then adsorbed them reversibly in the fluorous HPLC column through the pumping of their solutions. By using this dress-up chiral column and fluorophobic elution of an aqueous copper(II) sulfate/MeOH mixture, we could enantioseparate seven racemic amino acids within 40 min. When we washed the dress-up chiral column with fluorophilic tetrahydrofuran or MeOH, the adsorbed chiral stationary phase compounds desorbed from the column, completely destroying its enantioseparation ability. The relative standard deviation of the retention times, the number of theoretical plates, and the resolution for each of four preparations of the dress-up columns were all less than or equal to 9.53 % in 20-times repeated analysis, and were all less than or equal to 18.7 % in four different preparations, respectively. 相似文献
994.
Abstract The influence of dopants on the threshold electric field for switching anti-ferroelectric liquid crystals was determined from the optical response curve obtained by using a triangular wave. The effect of dopant concentration on the transition temperatures of the mixtures with a host material was also investigated. The threshold electric field was diminished depending on (i) the chemical structure of the additive and (ii) increasing amounts of the additive. The upper limits of the temperature region of the S*C A phases also decreased with increasing amount of additive, and these phases disappeared at 40 mol% of additive in all cases. Compound (C) is the most effective with respect to the threshold electric field. It is a two ring compound and has a chiral part similar to that of the host antiferroelectric liquid crystal compound. 相似文献
995.
An enhanced host–guest electro‐optical polymer system using poly(norbornene‐dicarboximides) via ROMP
Feng Yu Andrew M. Spring Lu Li Feng Qiu Kazuhiro Yamamoto Daisuke Maeda Masaaki Ozawa Keisuke Odoi Shiyoshi Yokoyama 《Journal of polymer science. Part A, Polymer chemistry》2013,51(6):1278-1284
High glass transition temperature poly(N‐cyclohexyl‐5‐norbornene‐2,3‐dicarboximide)s (NDI)s prepared by ring opening metathesis polymerization yielded polymers with a narrow polydispersity and well‐controlled molecular weight materials when using the Grubbs first generation initiator. Polymers produced using the Grubbs second generation initiator could not be controlled easily. By initiator selection it was also possible to synthesize polymers with either 98 or 52% trans microstructures. These materials were employed as electro‐optic (EO) polymer hosts for high molecular hyperpolarizability (β) phenyl vinylene thiophene vinylene bridge chromophores. This chromophore was modified by the incorporation of a tert‐butyldiphenylsilane group. The addition was able to further increase its EO coefficient (r33) to reach 93 pm/V in a trans rich poly(NDI) produced by the Grubbs first generation initiator, compared to a benchmark chromophore / polymer combination. We investigated in detail the relationship between polymer microstructure and their absolute molecular weight on forming the best host–guest with the high β chromophore. Our results indicate that by utilizing a very simple host–guest system a high r33 can be realized. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
996.
997.
998.
Tetsuo Tsuda Kazuhiro Kunisada Norio Nagahama Shohei Morikawa Takeo Saegusa 《合成通讯》2013,43(9-10):1575-1581
Ni(O)-phosphine(L) complexes (L=tri-n-alkylphosphines and bis(diphenylphosphino)butane) catalyzed the cycloaddition of ethoxyethyne and carbon dioxide to afford 4,5-diethoxy-α-pyrone regioselectively. 相似文献
999.
Intermolecular anionic rearrangement of the trimethylgermyl group in trimethylgermylacetonitrile, bis(trimethylgermyl)acetonitrile, and tris(trimethylgermyl)acetonitrile is described. 相似文献
1000.
Yohei Ishikawa Tomokatsu Hayakawa Koji Inoue Masayuki Nogami 《Journal of Sol-Gel Science and Technology》2013,65(3):324-328
Transparent, luminescent films of Pr3+-doped (Ca0.6Sr0.4)TiO3 (CSTO) have been prepared for cathodo-excitation of pure red luminescence by a sol–gel method from a stabilized sol with Ca2+, Sr2+, Pr3+ ions and titanium-isopropoxide in acetic acid. The structure and surface morphology of the obtained films are characterized by X-ray diffraction and Atomic Force Microscopy, respectively. The photoluminescence and cathodoluminescence (CL) properties of the films are evaluated. The films exhibit a strong single line of 1D2 → 3H4 red photoluminescence of Pr3+ ions doped, which increases almost linearly with the number of the dip-coated layers. It is also found that strong single red photoemission is observed and the CL intensity increases with increasing acceleration voltage. The results demonstrate that it is potential for application in field-emission display devices. 相似文献