全文获取类型
收费全文 | 2595篇 |
免费 | 63篇 |
国内免费 | 7篇 |
专业分类
化学 | 1610篇 |
晶体学 | 29篇 |
力学 | 79篇 |
数学 | 276篇 |
物理学 | 671篇 |
出版年
2021年 | 16篇 |
2020年 | 25篇 |
2019年 | 24篇 |
2018年 | 18篇 |
2016年 | 37篇 |
2015年 | 50篇 |
2014年 | 40篇 |
2013年 | 92篇 |
2012年 | 121篇 |
2011年 | 154篇 |
2010年 | 78篇 |
2009年 | 52篇 |
2008年 | 130篇 |
2007年 | 125篇 |
2006年 | 131篇 |
2005年 | 122篇 |
2004年 | 83篇 |
2003年 | 89篇 |
2002年 | 89篇 |
2001年 | 61篇 |
2000年 | 57篇 |
1999年 | 45篇 |
1998年 | 34篇 |
1997年 | 30篇 |
1996年 | 43篇 |
1995年 | 27篇 |
1994年 | 31篇 |
1993年 | 38篇 |
1992年 | 32篇 |
1991年 | 32篇 |
1990年 | 21篇 |
1989年 | 29篇 |
1988年 | 29篇 |
1987年 | 31篇 |
1986年 | 37篇 |
1985年 | 44篇 |
1984年 | 44篇 |
1983年 | 28篇 |
1982年 | 34篇 |
1981年 | 31篇 |
1980年 | 28篇 |
1979年 | 34篇 |
1978年 | 34篇 |
1977年 | 30篇 |
1976年 | 29篇 |
1975年 | 31篇 |
1974年 | 31篇 |
1973年 | 24篇 |
1971年 | 20篇 |
1967年 | 17篇 |
排序方式: 共有2665条查询结果,搜索用时 0 毫秒
81.
Lipid membranes composed of phosphatidyl choline and cholesterol were interfaced to polyacrylamine hydrogen by Langmuir—Blodgett thin-film deposition. The extent of lipid adsorption to the gel surface was critically dependent on the hydration of the polymer as determined by contact angle measurements. Some electrochemical transducers incorporating the deposited membrane/gel structure responded positively to phloretin and valinomycin. Limitations to the construction of this device are discussed. 相似文献
82.
James L. Kelley James B. Thompson Virgil L. Styles Francis E. Soroko Barrett R. Cooper 《Journal of heterocyclic chemistry》1995,32(5):1423-1428
The 3H-imidazo[4,5-c]pyridazine, 1H-imidazo[4,5-d]pyridazine, and 1H-benzimidazole analogues of the potent anticonvulsant purine 9-(2-fluorobenzyl)-6-methylamino-9H-purine (1, 78U79) were synthesized and tested for anticonvulsant activity. The 3H-imidazo[4,5-c]pyridazines 8 and 9 were prepared in five stages from 3,4,5-trichloropyridazine (2) . The 1H-imidazolo[4,5-d]pyridazine 15 was synthesized in four stages from 5-[(benzyloxy)methyl]-1,5-dihydro-4H-imidazo[4,5-d] pyridazin-4-one (10a) . The benz-imidazole analogues 18 and 20 were prepared from 2,6-dinitroaniline in three stages. These compounds were one-tenth or less as active as 1 in protecting rats against maximal electroshock-induced seizures. 相似文献
83.
Stéphanie M. Cornet Andrés E. Goeta Judith A.K. Howard Mark D. Roden Amber L. Thompson 《Journal of organometallic chemistry》2005,690(16):3630-3637
Oxidative addition reactions of Cl2CPR (R = 2,4,6-tris(trifluoromethyl)phenyl (Ar) or 2,6-bis(trifluoromethyl)phenyl (Ar′) with Pt(PPh3)4 yield the cis and trans (at platinum) complexes [PtCl(ClCPAr)(PPh3)2] and [PtCl(ClCPAr′)(PPh3)2]. All starting materials and intermediates have been characterised by NMR spectroscopy. The crystal and molecular structures of the trans-platinum complexes have been determined by single-crystal X-ray diffraction at low temperature. 相似文献
84.
Determination of delta 9-tetrahydrocannabinol in human blood and saliva by high-performance liquid chromatography with amperometric detection 总被引:1,自引:0,他引:1
A rapid, sensitive and selective determination of delta 9-tetrahydrocannabinol (THC) in human plasma, serum and saliva was developed with high-performance liquid chromatography with electrochemical detection. Initially, samples were deproteinized, followed by a one step liquid-liquid extraction. Samples were measured by high-performance liquid chromatography with electrochemical detection with 4-dodecylresorcinol as the internal standard. The minimal detectable limit for THC in biological samples was ca. 1 ng/ml with a signal-to-noise ratio greater than 3, corresponding to an on-column sensitivity for THC of ca. 0.5 ng. The detector was operated at + 0.90 V vs. Ag/AgCl and exhibited linearity over a concentration range of 1-150 ng/ml with correlation coefficients of the standard curves greater than 0.99. 相似文献
85.
Trace amounts of antimony(III) may be determined in 6M hydrobromic acid by measurement of the red fluorescence of its bromide complex at -196 degrees , the optimum wavelengths of excitation and emission (360 and 586 nm respectively) being used. Calibration graphs are linear between 0.01 and 0.25 ppm. The effect of the presence of 50-fold molar amounts of 55 foreign ions has been studied. Of the ions studied, only iron(III) and tellurium(IV) interfere, and these may be tolerated at the 50- and 20-fold levels respectively. A 1000-fold molar amount of arsenic(III) causes no interference. 相似文献
86.
87.
The structural and physical properties of nanoparticles of nitromethane are studied by using molecular dynamics methods with a previously developed force field. [Agrawal et al., J. Chem. Phys. 119, 9617 (2003).] This force field accurately predicts solid- and liquid-state properties as well as melting of bulk nitromethane. Molecular dynamics simulations of nanoparticles with 480, 240, 144, 96, 48, and 32 nitromethane molecules have been carried out at various temperatures. The carbon-carbon radial distribution function, dipole-dipole correlation function, core density, internal enthalpy, and atomic diffusion coefficients of the nanoparticles were calculated at each temperature. These properties were used to characterize the physical phases and thus determine the melting transitions of the nanoparticles. The melting temperatures predicted by the various properties are consistent with one another and show that the melting temperature increases with particle size, approaching the bulk limit for the largest particle. A size dependence of melting points has been observed in experimental and theoretical studies of atomic nanoparticles, and this is a further demonstration of the effect for large nanoparticles of complex molecular materials. 相似文献
88.
Thompson M. Sloane 《Chemical physics letters》1978,54(2):269-272
Products of the reaction of OH with benzene, toluene, and 1,3,5-trimethylbenzene have been identified in crossed molecular beam experiments conducted at 300 K. Ionization potentials of the most intense products were also measured. 相似文献
89.
Wood TE Dalgleish ND Power ED Thompson A Chen X Okamoto Y 《Journal of the American Chemical Society》2005,127(16):5740-5741
Helical zinc(II) complexes of bis(dipyrromethene)s bearing homochiral amide substituents were synthesized. Analysis of the products by chiral HPLC showed two diastereomeric major products and showed that dipyrromethene double-nuclear helicates are stereochemically stable and do not interconvert. Circular dichroism (CD) studies showed that the complexation reactions had proceeded with modest diastereomeric excesses. Analysis of an analogous symmetric zinc(II) bis(dipyrromethene) lacking homochiral substituents that could act as chromophores discounted induced CD by the chiral auxiliaries. 相似文献
90.
James C. Thompson A.P.Gerald Wright William F. Reynolds 《Journal of fluorine chemistry》1981,17(6):509-529
Consideration of 19F-19F and 29Si-19F coupling constants in a series of organosilicon derivatives containing SiF2 and Si2F4 units reveals a number of trends which are useful for structural and stereochemical assignments. For example the vicinal 19F-19F coupling constants in a number of CSiF2SiF2C- derivatives (including straight chain compounds, disilacyclobutanes and disilacyclohexanes) show an apparent linear dependence on dihedral angle, varying in magnitude from near zero for small values of φ up to ca. 19 Hz for φ ~ 180°. This is particularly useful for stereochemical assignments [1,2]. In addition 29Si-19F coupling constants appear to fall in quite distinct ranges (1JSiF > 300 Hz, 29 Hz < 2JSiF < 55 Hz, 3JSiF < 10 Hz). This is quite useful for structural assignments [1,6]. Reaction of SiF2 with 1,3-cyclohexadiene gives two new silicon fluorine compounds: a disilabicyclo[2,2,2]octene and an HSi2F5-substituted cyclohexadiene. 相似文献