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91.
Xiaomeng LiShifang Luan Huawei YangHengchong Shi Jie ZhaoJing Jin Jinghua Yin Paola Stagnaro 《Applied Surface Science》2012,258(7):2344-2349
Poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) copolymer biomedical elastomer was covalently grafted with poly(ethylene glycol) methyl ether methacrylate (PEGMA) via a photo-initiated graft polymerization technique. The surface graft polymerization of SEBS with PEGMA was verified by ATR-FTIR and XPS. Effect of graft polymerization parameters, i.e., monomer concentration, UV irradiation time and initiator concentration on the grafting density was investigated. Comparing with the virgin SEBS film, the PEGMA-modified SEBS film presented an enhanced wettability and a larger surface energy. Besides, the surface grafting of PEGMA imparted excellent anti-platelet adhesion and anti-protein adsorption to the SEBS surface. 相似文献
92.
The core-shell structural dielectric particles are applied widely in the electrorheological (ER) fluids. The properties of the dielectric core are critical factors influencing their ER activity. In this paper, we successfully synthesized two kinds of core-shell hydroxyl titanium oxalate (TOC) particles with SiO(2) and TiO(2) as core, respectively. The obtained core-shell structural SiO(2)-TOC and TiO(2)-TOC particles were well-dispersed spherical nanoparticles with ideal morphology and a narrow size distribution. Under DC electric fields, the TiO(2)-TOC ER fluid showed notable ER activity with a yield stress of about 96 kPa (at 4 kV/mm), which is 3 times of that SiO(2)-TOC ER fluid and outclassed the yield stress of the TOC ER fluid. The dielectric spectra indicated that the higher dielectric constant of TiO(2) core induces the stronger interaction between the neighboring particles, which contribute to the enhancement of ER activity. 相似文献
93.
Seth PP Yu J Jazayeri A Pallan PS Allerson CR Østergaard ME Liu F Herdewijn P Egli M Swayze EE 《The Journal of organic chemistry》2012,77(11):5074-5085
We report the design and synthesis of 2'-fluoro cyclohexenyl nucleic acid (F-CeNA) pyrimidine phosphoramidites and the synthesis and biophysical, structural, and biological evaluation of modified oligonucleotides. The synthesis of the nucleoside phosphoramidites was accomplished in multigram quantities starting from commercially available methyl-D-mannose pyranoside. Installation of the fluorine atom was accomplished using nonafluorobutanesulfonyl fluoride, and the cyclohexenyl ring system was assembled by means of a palladium-catalyzed Ferrier rearrangement. Installation of the nucleobase was carried out under Mitsunobu conditions followed by standard protecting group manipulations to provide the desired pyrimidine phosphoramidites. Biophysical evaluation indicated that F-CeNA shows behavior similar to that of a 2'-modified nucleotide, and duplexes with RNA showed slightly lower duplex thermostability as compared to that of the more rigid 3'-fluoro hexitol nucleic acid (FHNA). However, F-CeNA modified oligonucleotides were significantly more stable against digestion by snake venom phosphodiesterases (SVPD) as compared to unmodified DNA, 2'-fluoro RNA (FRNA), 2'-methoxyethyl RNA (MOE), and FHNA modified oligonucleotides. Examination of crystal structures of a modified DNA heptamer duplex d(GCG)-T*-d(GCG):d(CGCACGC) by X-ray crystallography indicated that the cyclohexenyl ring system exhibits both the (3)H(2) and (2)H(3) conformations, similar to the C3'-endo/C2'-endo conformation equilibrium seen in natural furanose nucleosides. In the (2)H(3) conformation, the equatorial fluorine engages in a relatively close contact with C8 (2.94 ?) of the 3'-adjacent dG nucleotide that may represent a pseudo hydrogen bond. In contrast, the cyclohexenyl ring of F-CeNA was found to exist exclusively in the (3)H(2) (C3'-endo like) conformation in the crystal structure of the modified A-form DNA decamer duplex [d(GCGTA)-T*-d(ACGC)](2.) In an animal experiment, a 16-mer F-CeNA gapmer ASO showed similar RNA affinity but significantly improved activity compared to that of a sequence matched MOE ASO, thus establishing F-CeNA as a useful modification for antisense applications. 相似文献
94.
建立离子色谱法检测食品添加剂焦碳酸二甲酯(DMDC)中的杂质氯离子的方法。样品用水溶解超声定容后,采用SH-AC-1阴离子交换柱(250mm×4.6mm,5μm)分离,抑制电导法检测。考察了淋洗液种类、浓度对氯离子与干扰离子分离度的影响。最佳色谱条件:以0.005mol/L的四硼酸钠水溶液为淋洗液,流速1.0mL/min。在此条件下,样品中的氯离子可以和其它干扰离子分离,而且分离度达3.0以上,峰形对称。在氯离子浓度为0.1~5.0mg/L的范围内,可获得良好的线性关系,线性相关系数大于0.999;氯离子检出限(S/N=3)达0.007mg/L,加标回收率为97.5%~98.9%。该方法可以用于食品添加剂DMDC中氯离子的测定。 相似文献
95.
半导体激光器纵向泵浦准连续Cr:LiSAF激光器的实验研究 总被引:1,自引:0,他引:1
用波长为653.2nm的半导体激光器实现了纵向泵浦Cr:LiSAF激光器的准连续运转,晶体平均吸收功率为140mW时获得激光输出,在LD最大输出功率范围内,晶体平均吸收功率为680mW时,可获得最大平均输出功率32mW,斜效率5.6%. 相似文献
96.
Zhenyu Sheng Qinhua Song Fan Gao Xiaoguo Zhou Jiang Li Jinghua Dai Haihong Sun Quanxin Li Shuqin Yu Xingxiao Ma 《Research on Chemical Intermediates》2000,26(7-8):715-725
The pH effects on the photochemical reaction of amino acids and related dipeptides with 4-nitroquinoline 1-oxide (4NQO) as a photosensitizer have been investigated by laser flash photolysis. The obtained kinetic parameters show that the electron transfer from Tryptophan (Trp), Tyrosine (Tyr) as well as dipeptides containing Trp and/or Tyr residue to triplet 4NQO (T4NQO) are efficient, but inefficient from methionine (Met) and dipeptides containing neither Trp nor Tyr. The result was supported by the calculated values of the free energy change from measured oxidation potentials for the electron transfer. It was demonstrated that Trp and Tyr residues are initial reaction sites with T4NQO, while Tyr/O? radical may be final species for Trp-Tyr dipeptide. In acidic aqueous solutions, the self-quenching rate constants of T4NQO and the rate constants of electron transfer from amino acids to T4NQO decrease with decreasing pH. In alkaline solutions, amino acids are easily oxidized by 4NQO under irradiation of laser pulse, and no transient absorption signal was observed. 相似文献
97.
Banach空间中具有数列的渐近拟非扩张型映象的不动点及其具有误差的Ishikawa迭代逼近 总被引:1,自引:0,他引:1
孟京华 《高等学校计算数学学报》2008,30(3)
1引言及相关定义 引文[1~5]讨论了渐近非扩张映象和渐近非扩张型映象不动点的迭代逼近问题.文[6]改进了文[1]中条件,将T由渐近非扩张型映象推广到T是渐近拟非扩张型映象. 相似文献
98.
Madhusudhan Reddy Gadi Congcong Chen Shumin Bao Shuaishuai Wang Yuxi Guo Jinghua Han Weidong Xiao Lei Li 《Chemical science》2023,14(7):1837
All O-GalNAc glycans are derived from 8 cores with 2 or 3 monosaccharides linked via α- or β-glycosidic bonds. While chemical and chemoenzymatic syntheses of β-linked cores 1–4 and 6 and derived glycans have been well developed, the preparation of α-linked rare cores 5, 7, and 8 is challenging due to the presence of this 1,2-cis linkage. Meanwhile, the biosynthesis and functional roles of these structures are poorly understood. Herein, we synthesize 3 α-linked rare cores with exclusive α-configuration from a versatile precursor through multifaceted chemical modulations. Efficient regioselective α2-6sialylion of the rare cores was then achieved by Photobacterium damselae α2-6sialyltransferase-catalyzed reactions. These structures, together with β-linked cores 1–4 and 6, and their sialylated forms, were fabricated into a comprehensive O-GalNAc core microarray to profile the binding of clinically important GalNAc-specific lectins. It is found that only Tn, (sialyl-)core 5, and core 7 are the binders of WFL, VVL, and SBA, while DBA only recognized (sialyl-)core 5, and Jacalin is the only lectin that binds core 8. In addition, activity assays of human α-N-acetylgalactosaminide α2-6sialyltransferases (ST6GalNAcTs) towards the cores suggested that ST6GalNAc1 may be involved in the biosynthesis of previously identified sialyl-core 5 and sialyl-core 8 glycans. In conclusion, we provide efficient routes to access α-linked O-GalNAc rare cores and derived structures, which are valuable tools for functional glycomics studies of mucin O-glycans.Mucin rare cores 5, 7, and 8 with 1,2-cis glycosidic bonds were prepared with exclusive stereo-selectivity from a versatile precursor. Enzyme-catalyzed regio-selective sialylation was then achieved, yielding natural sialylated rare cores. 相似文献
99.
100.
本文提出了一个从随机到确定性的变测度算法,通过对不同的箱子采用不同的测度,将Monte-Carlo随机投点与确定性数论方法相结合的策略,使水平值充分地下降.最后,给出了实现算法收敛性并通过数值实验验证了其有效性. 相似文献