全文获取类型
收费全文 | 1702篇 |
免费 | 40篇 |
国内免费 | 3篇 |
专业分类
化学 | 1175篇 |
晶体学 | 9篇 |
力学 | 23篇 |
综合类 | 1篇 |
数学 | 85篇 |
物理学 | 452篇 |
出版年
2021年 | 13篇 |
2020年 | 14篇 |
2019年 | 23篇 |
2018年 | 16篇 |
2016年 | 26篇 |
2015年 | 22篇 |
2014年 | 17篇 |
2013年 | 84篇 |
2012年 | 69篇 |
2011年 | 72篇 |
2010年 | 44篇 |
2009年 | 61篇 |
2008年 | 88篇 |
2007年 | 88篇 |
2006年 | 72篇 |
2005年 | 66篇 |
2004年 | 68篇 |
2003年 | 68篇 |
2002年 | 49篇 |
2001年 | 49篇 |
2000年 | 30篇 |
1999年 | 39篇 |
1998年 | 21篇 |
1997年 | 26篇 |
1996年 | 35篇 |
1995年 | 23篇 |
1994年 | 20篇 |
1993年 | 34篇 |
1992年 | 30篇 |
1991年 | 27篇 |
1990年 | 27篇 |
1989年 | 21篇 |
1988年 | 31篇 |
1987年 | 23篇 |
1986年 | 17篇 |
1985年 | 23篇 |
1984年 | 32篇 |
1983年 | 19篇 |
1982年 | 20篇 |
1981年 | 19篇 |
1980年 | 16篇 |
1979年 | 25篇 |
1978年 | 21篇 |
1977年 | 22篇 |
1976年 | 15篇 |
1975年 | 12篇 |
1974年 | 15篇 |
1969年 | 11篇 |
1968年 | 9篇 |
1967年 | 9篇 |
排序方式: 共有1745条查询结果,搜索用时 46 毫秒
991.
Naoki Yokoyama Nobuaki Tanaka Natsumi Fujimoto Dr. Rika Tanaka Prof. Dr. Shuichi Suzuki Prof. Daisuke Shiomi Prof. Dr. Kazunobu Sato Prof. Dr. Takeji Takui Prof. Dr. Masatoshi Kozaki Prof. Dr. Keiji Okada 《化学:亚洲杂志》2021,16(1):72-79
A nitronyl nitroxide unit ( NN ) was linked with a triphenylamine-based condensed polycyclic skeleton DOTT to form a radical substituted donor NN - DOTT . X-ray crystal structure analysis demonstrated a flat bowl shape of the DOTT unit. EPR spectra showed the localization of electron spin on the NN unit. Chemical oxidation of the DOTT unit produced radical-substituted radical cation salts NN - DOTT + ⋅ SbF6− and NN - DOTT + ⋅ FeBr4− that are stable under ambient conditions. The magnetic behavior of NN - DOTT + ⋅ SbF6− is characterized by the strong intramolecular ferromagnetic interaction between NN and DOTT +. The X-ray structural analysis of NN - DOTT + ⋅ FeBr4− shows planar structure of DOTT and 1D mixed-stack column of NN-DOTT + and FeBr4−. Magnetic measurements established that NN - DOTT + ⋅ FeBr4− undergoes magnetic phase transition into a weak ferromagnet at 7 K. 相似文献
992.
Chimeric RNA Oligonucleotides with Triazole and Phosphate Linkages: Synthesis and RNA Interference 下载免费PDF全文
Dr. Tomoko Fujino Kanako Kogashi Koudai Okada Dr. Martin Mattarella Takeru Suzuki Dr. Kenichi Yasumoto Prof. Kazuhiro Sogawa Prof. Hiroyuki Isobe 《化学:亚洲杂志》2015,10(12):2683-2688
Chimeric RNA oligonucleotides with an artificial triazole linker were synthesized using solution‐phase click chemistry and solid‐phase automated synthesis. Scalable synthesis methods for jointing units for the chimeric structure have been developed, and after click‐coupling of the jointing units with triazole linkers, a series of chimeric oligonucleotides was prepared by utilizing the well‐established phosphoramidite method for the elongation. The series of chimeric 21‐mer oligonucleotides that possessed the triazole linker at different strands and positions allowed for a screening study of the RNA interference to clarify the preference of the triazole modifications in small‐interfering RNA molecules. 相似文献
993.
Inside Cover: Chimeric RNA Oligonucleotides with Triazole and Phosphate Linkages: Synthesis and RNA Interference (Chem. Asian J. 12/2015) 下载免费PDF全文
994.
Copper‐Modified Covalent Triazine Frameworks as Non‐Noble‐Metal Electrocatalysts for Oxygen Reduction 下载免费PDF全文
Kazuyuki Iwase Tatsuro Yoshioka Prof. Dr. Shuji Nakanishi Prof. Dr. Kazuhito Hashimoto Dr. Kazuhide Kamiya 《Angewandte Chemie (International ed. in English)》2015,54(38):11068-11072
The electrochemical oxygen reduction reaction (ORR) is an important cathode reaction of various types of fuel cells. The development of electrocatalysts composed only of abundant elements is a key goal because currently only platinum is a suitable catalyst for ORR. Herein, we synthesized copper‐modified covalent triazine frameworks (CTF) hybridized with carbon nanoparticles (Cu‐CTF/CPs) as efficient electrocatalysts for the ORR in neutral solutions. The ORR onset potential of the synthesized Cu‐CTF/CP was 810 mV versus the reversible hydrogen electrode (RHE; pH 7), the highest reported value at neutral pH for synthetic Cu‐based electrocatalysts. Cu‐CTF/CP also displayed higher stability than a Cu‐based molecular complex at neutral pH during the ORR, a property that was likely as a result of the covalently cross‐linked structure of CTF. This work may provide a new platform for the synthesis of durable non‐noble‐metal electrocatalysts for various target reactions. 相似文献
995.
Field-reversed configurations (FRCs) driven by rotating magnetic fields (RMFs) with spatial high harmonics have been studied in the metal flux conserver of the FRC injection experiment. The experimental results show that the fundamental RMF component is observed to penetrate the plasma column, while the high harmonics are screened at the plasma edge due to their slower or reversed rotation. This selective penetration of the RMF provides good compatibility of radial and azimuthal force balances; significant radial inward force mostly from the high-harmonic components, and sufficient azimuthal torque solely provided by the fundamental component. 相似文献
996.
Okada K Yoshizaki H Kameshima Y Nakajima A Madhusoodana CD 《Journal of colloid and interface science》2007,314(1):176-183
Mesoporous silicas were synthesized by hydrothermal treatment of selectively acid-treated saponite (an ideal structural formula: Na(1/3)Mg(3)(Si(11/3)Al(1/3))O(10)(OH)(2)), having a 2:1 type layered structure as the silica source and its porous properties were examined and compared with that from kaolinite (an ideal structural formula: Al(2)Si(2)O(5)(OH)(4)), having a 1:1 type layered structure. Synthetic saponite was selectively leached in H(2)SO(4) solutions with various concentrations (0.05-1 M) at 70 degrees C for 0.5 h. The resulting products (precursors) were mixed with cetyltrimethylammonium bromide (CTABr), NaOH and H(2)O, hydrothermally treated at 110 degrees C and removed the CTABr by calcining at 560 degrees C. A hexagonal mesoporous phase was obtained with higher Si/(Al(+Mg)) ratios of the resulting precursors. The XRD patterns of these products show the peaks assigned by a hexagonal lattice with a(0)=4.0-4.6 nm and the crystallinity becomes higher with higher Si/(Al(+Mg)) ratios of the precursors. The specific surface area (S(BET)) values of the present mesoporous silicas range from 800 to 1100 m(2)/g at CTABr/precursor=0.1 and although they are not as high as those from precursors prepared from calcining and acid-treatment of kaolinite (1420 m(2)/g), they are increased to 1400-1500 m(2)/g by increasing the ratio CTABr/precursor 0.2. The reason for the difference in the optimum preparation conditions between saponite and kaolinite may be attributed to the difference in the linkage of the SiO(4) tetrahedra in these precursors (i.e. layered or framework structures), which result in great differences in the selective leaching rates and structures of the resulting silica-rich products. 相似文献
997.
Mitsuhiro Okada 《Journal of organometallic chemistry》2007,692(23):5183-5189
A series of anilinonaphthoquinone-based nickel complexes, Ni(C10H5O2NAr)(Ph)(PPh3) (Ar = C6H3-2,6-Me (1c); Ar = C6H2-2,4,6-Me (2c); Ar = C6H3-2,6-Et (3c)), were synthesized and the structures of 1c-3c were confirmed by single crystal X-ray analyses. The anilinonaphthoquinone-ligated nickel complexes activated with B(C6F5)3 showed high activities for ethylene polymerization at 40 °C under atmospheric pressure of ethylene and gave polyethylene with long chain branches and short chain branches. The activity of these systems was decreased by lowering polymerization temperature accompanied by increase in molecular weight. The number of the chain branches was also decreased with lowering polymerization temperature and increasing the bulkiness of the ligand. 相似文献
998.
Recent progress in high-resolution structural study of rhodopsin has been enabled by a novel selective extraction procedure with rod photoreceptor cells. In this study, we applied the method for rapid and efficient preparation of a purified analogue pigment using bovine rod outer segment membranes with 9-cis-retinal. After complete bleaching of the membranes and subsequent regeneration with the exogenous retinal, 9-cis-rhodopsin is selectively extracted from the membranes using combination of zinc and heptylthioglucoside. The solubilized sample, even with a small amount of contaminating retinal oximes, is shown to be pure enough for three-dimensional crystallization. The X-ray diffraction from 9-cis-rhodopsin crystals was examined and the electron density map at 2.9 angstroms resolution in the chromophore region can be fitted well with the model of 9-cis-retinal Schiff base. 相似文献
999.
1000.