全文获取类型
收费全文 | 2701篇 |
免费 | 52篇 |
国内免费 | 9篇 |
专业分类
化学 | 2018篇 |
晶体学 | 76篇 |
力学 | 46篇 |
数学 | 81篇 |
物理学 | 541篇 |
出版年
2022年 | 18篇 |
2021年 | 22篇 |
2020年 | 25篇 |
2019年 | 29篇 |
2018年 | 19篇 |
2016年 | 42篇 |
2015年 | 50篇 |
2014年 | 51篇 |
2013年 | 128篇 |
2012年 | 115篇 |
2011年 | 113篇 |
2010年 | 70篇 |
2009年 | 77篇 |
2008年 | 123篇 |
2007年 | 145篇 |
2006年 | 154篇 |
2005年 | 131篇 |
2004年 | 138篇 |
2003年 | 109篇 |
2002年 | 106篇 |
2001年 | 86篇 |
2000年 | 70篇 |
1999年 | 42篇 |
1998年 | 31篇 |
1997年 | 24篇 |
1996年 | 36篇 |
1995年 | 36篇 |
1994年 | 32篇 |
1993年 | 32篇 |
1992年 | 66篇 |
1991年 | 29篇 |
1990年 | 29篇 |
1989年 | 29篇 |
1988年 | 32篇 |
1987年 | 33篇 |
1986年 | 33篇 |
1985年 | 35篇 |
1984年 | 43篇 |
1983年 | 21篇 |
1982年 | 24篇 |
1981年 | 32篇 |
1980年 | 28篇 |
1979年 | 36篇 |
1978年 | 27篇 |
1977年 | 25篇 |
1976年 | 22篇 |
1975年 | 18篇 |
1974年 | 26篇 |
1973年 | 23篇 |
1972年 | 15篇 |
排序方式: 共有2762条查询结果,搜索用时 15 毫秒
991.
S. Yamashita K. Hino Y. Inoue Y. Okada R. Hirahara Y. Nakazawa H. Miyasaka M. Yamashita 《Journal of Thermal Analysis and Calorimetry》2008,92(2):439-442
A magnetic-fields dependence of heat capacity of [Mn5(hmp)4(OH)2{N(CN)2}6]2MeCN·2THF (hmp=hydroxymethylpyridinate) is investigated by the thermal relaxation calorimetry technique. This compound is
a three-dimensional system consisting of Mn4 single-molecule magnet (SMM) units and Mn2+ ions, which are linked by the dicyanamide ligands to form a coordination network structure. A sharp peak of C
p being associated with the formation of three-dimensional long-range order is observed around 1.96 K. The thermodynamic discussion
based on the magnetic entropy suggests that both SMMs and Mn2+ ions are involved in the formation of the anitiferromagnetic spin ordering. However, this long-range ordering is very sensitive
to the external magnetic fields which work to change the magnitude of the Zeeman splitting of the SMM levels. The behavior
under magnetic fields is similar to that of the two-dimensional Mn4-network system studied previously. 相似文献
992.
993.
Mohammad Ghazizadeh Yoshihiro Sasaki Tatsuo Oguro Shigeru Sato Seiko Egawa Kyoko Inoue Akiko Adachi Hajime Shimizu Oichi Kawanami 《Microscopy and microanalysis》2008,14(4):357-361
Observation of the internal ultrastructure of human chromosomes by transmission electron microscopy (TEM) has frequently been attempted in spite of the difficulties in detaching metaphase chromosome spreads from the glass slide for further processing. In this study we have used a method in which metaphase chromosome spreads were prepared on a flexible thermoplastic membrane (ACLAR) film. To assess chromosome identity, a diamidino-phenylindole staining and karyotying was first done using a conventional cytogenetic system. The chromosome spreads were then fixed with 1% osmium tetroxide, stained with freshly prepared 2% tannic acid, dehydrated, and flat-embedded in epoxy resin. The resin sheet was easily detachable and carried whole chromosome spreads. By this method, TEM observation of chromosomes from normal human lymphocytes allowed a thorough examination of the ultrastructure of centromeres, telomeres, fragile sites, and other chromosomal regions. Various ultrastructural patterns including thick electron dense boundaries, less dense internal regions, and extended chromatin loops at the periphery of the chromosomes were discernible. Application of the present method to chromosome research is expected to provide comprehensive information on the internal ultrastructure of different chromosomal regions in relation to function. 相似文献
994.
Stoupin S Rivera H Li Z Segre CU Korzeniewski C Casadonte DJ Inoue H Smotkin ES 《Physical chemistry chemical physics : PCCP》2008,10(42):6430-6437
Sonochemically prepared PtRu (3 : 1) and Johnson Matthey PtRu (1 : 1) were analyzed by X-ray absorption spectroscopy in operating liquid feed direct methanol fuel cells. The total metal loadings were 4 mg cm(-2) unsupported catalysts at the anode and cathode of the membrane electrode assembly. Ex situ XRD lattice parameter analysis indicates partial segregation of the Ru from the PtRu fcc alloy in both catalysts. A comparison of the in situ DMFC EXAFS to that of the as-received catalyst shows that catalyst restructuring during DMFC operation increases the total metal coordination numbers. A combined analysis of XRD determined grain sizes and lattice parameters, ex situ and in situ EXAFS analysis, and XRF of the as-received catalysts enables determination of the catalyst shell composition. The multi-spectrum analysis shows that the core size increases during DMFC operation by reduction of Pt oxides and incorporation of Pt into the core. This increases the mole fraction of Ru in the catalyst shell structure. 相似文献
995.
Inoue K Ohashi K Iino T Sasaki J Judai K Nishi N Sekiya H 《Physical chemistry chemical physics : PCCP》2008,10(21):3052-3062
Infrared (IR) spectra are measured for Ag(+)(NH(3))(n) with n = 3-8 in the NH-stretch region using photodissociation spectroscopy. The spectra of n = 3 and 4 exhibit absorption features only near the frequencies of the isolated NH(3), indicating that every NH(3) molecule is coordinated individually to Ag(+). For n >or= 5, the occupation of the second shell is evidenced by lower-frequency features characteristic of hydrogen bonding between NH(3) molecules. Density functional theory and MP2 calculations are carried out in support of the experiments. A detailed comparison of the experimental and theoretical IR spectra reveals the preference for a tetrahedral coordination in the n = 5 and 6 ions. Likewise, most of the features observed in the spectra of n = 7 and 8 can be assigned to isomers containing a tetrahedrally coordinated inner shell as the basic structural motif. These results signify that the ammonia-solvated Ag(+) ion has a propensity toward a coordination number of four and the resulting tetrahedral Ag(+)(NH(3))(4) complex forms the central core of further solvation process. 相似文献
996.
Doi T Inoue H Tokita M Watanabe J Takahashi T 《Journal of combinatorial chemistry》2008,10(1):135-141
Six-types of palladium-catalyzed coupling, Mizoroki-Heck, Migita-Stille, Sonogashira, carbonylative esterification, carbonylative Stille, and carbonylative Sonogashira reactions, were performed on a polymer support. The above coupling reactions of m- and p-substituted aromatic rings, followed by carbonylative esterification with m- and p-substituted anisol derivatives were carried out in a combinatorial manner. Acid cleavage from the polymer-support provided the conjugated aromatic ring systems 1 and 2, which are the core parts of rodlike liquid crystals. 相似文献
997.
Florian S. Tschernuth Lukas Bichlmaier Sebastian Stigler Prof. Dr. Shigeyoshi Inoue 《欧洲无机化学杂志》2023,26(31):e202300388
The emerging field of Lewis acidic silanes demonstrates the versability of molecular silicon compounds for catalytic applications. Nevertheless, when compared to the multifunctional boron Lewis acid B(C6F5)3, silicon derivatives still lack in terms of reactivity. In this regard, we demonstrate the installation of perfluorotolyl groups (TolF) on neutral silicon atoms to obtain the respective tetra- and trisubstituted silanes Si(TolF)4 and HSi(TolF)3. These compounds were fully characterized including SC-XRD analysis but unexpectedly showed no significant Lewis acidity. By using strongly electron-withdrawing perfluorocresolato groups (OTolF) the tetrasubstituted silane Si(OTolF)4 was obtained, bearing an 8 % increased Δδ(31P) shift when applying the Gutmann-Beckett method, compared to literature-known Si(OPhF)4. Ultimately the heteroleptic Si(PhF)2pinF was successfully synthesized and fully characterized including SC-XRD analysis, introducing a highly Lewis acidic silicon atom holding two silicon-carbon bonds. 相似文献
998.
Lise Joost Støckler Rasmus Stubkjær Christensen Magnus Kløve Andreas Dueholm Bertelsen Anders Bæk Borup Prof. Dr. Lennard Krause Seiya Takahashi Dr. Tomoki Fujita Prof. Dr. Hidetaka Kasai Dr. Ichiro Inoue Prof. Dr. Eiji Nishibori Prof. Dr. Dr. Dr. Bo Brummerstedt Iversen 《Chemphyschem》2023,24(23):e202300407
X-ray scattering data measured on femtosecond timescales at the SACLA X-ray Free Electron Laser (XFEL) facility on a suspension of HfO2 nanoparticles in a liquid jet were used for pair distribution function (PDF) analysis. Despite a non-optimal experimental setup resulting in a modest Qmax of ~8 Å−1, a promising PDF was obtained. The main features were reproduced when comparing the XFEL PDF to a PDF obtained from data measured at the PETRA III synchrotron light source. Refining structural parameters such as unit cell dimension and particle size from the XFEL PDF provided reliable values. Although the reachable Qmax limited the obtainable information, the present results indicate that good quality PDFs can be obtained on femtosecond timescales if the experimental conditions are further optimized. The study therefore encourages a new direction in ultrafast structural science where structural features of amorphous and disordered systems can be studied. 相似文献
999.
The preparation and characterization of n-alkane/water emulsions using beta-cyclodextrin (beta-CD) were studied. The prepared n-alkane/water emulsions were of the oil-in-water (O/W) type, and the stability of emulsions was in the order of n-hexadecane > n-dodecane > n-octane. From observations using polarized light microscopy and powder X-ray diffraction measurement, it was suggested that the formation of a dense film at the oil-water interface and the three-dimensional structural network created by precipitated complexes in the continuous phase are associated with the stability of emulsion. Furthermore, it was clarified that O/W-type emulsions were formed because the contact angle (theta ow) which the precipitate makes with the interface was theta ow < 90 degrees in all compounds (oils) used in this study. 相似文献
1000.
Muramatsu H Yamamoto Y Shigeno M Shirakawabe Y Inoue A Kim WS Kim SJ Chang SM Kim JM 《Analytica chimica acta》2008,611(2):233-238
We have fabricated polymer tips for atomic force microscopy in order to elucidate the effects of tip length and shape on cantilever vibration damping in liquids. The vibration damping is investigated by measuring the vibration amplitude of cantilevers as a function of tip-sample distance. The cantilever with a short tip provides a higher damping effect over long tip-sample distances. When the vibration amplitude was rescaled to show the effect of the cantilever width on oscillation damping, the vibration amplitude of cantilevers with various tip lengths was similarly obtained in a long distance range over 50 μm. This similarity is explained by an acoustic damping model in which an acoustic wave is generated by the cantilever. Finally, the results indicate a cantilever with a sufficiently long tip compared to the cantilever width can dramatically reduce the long-range damping effect in a liquid environment. 相似文献