全文获取类型
收费全文 | 530篇 |
免费 | 17篇 |
国内免费 | 4篇 |
专业分类
化学 | 412篇 |
晶体学 | 1篇 |
力学 | 5篇 |
数学 | 57篇 |
物理学 | 76篇 |
出版年
2021年 | 2篇 |
2020年 | 8篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 3篇 |
2016年 | 10篇 |
2015年 | 11篇 |
2014年 | 14篇 |
2013年 | 25篇 |
2012年 | 28篇 |
2011年 | 34篇 |
2010年 | 19篇 |
2009年 | 14篇 |
2008年 | 42篇 |
2007年 | 29篇 |
2006年 | 24篇 |
2005年 | 36篇 |
2004年 | 36篇 |
2003年 | 19篇 |
2002年 | 23篇 |
2001年 | 3篇 |
2000年 | 8篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 2篇 |
1992年 | 2篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 10篇 |
1983年 | 4篇 |
1982年 | 9篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1968年 | 2篇 |
1966年 | 2篇 |
排序方式: 共有551条查询结果,搜索用时 15 毫秒
1.
Takahiko Nakazi 《Indagationes Mathematicae》2003,14(1):55-61
Let N+ denote the Smirnov class on the open unit disc D. It is easy to see that for any outer function g in N+, there exists a function G in N+ such that |g|; ≤ ReG on δ. We describe such a G. In general, G may not be outer. In this paper, a necessary and sufficient condition on g is given for the existence of an outer function G such that |;g|; < ReG. When g belongs to the Hardy space H1, G is trivially given as the Herglotz integral of |;g|;. 相似文献
2.
3.
In proportion to the environmental pollution problems caused by organotin compounds, the genotoxicities of tin compounds in the environments have become of interest so as to estimate their safety in recent years. In this work, isolated λ-DNA (double-strand DNA) was incubated with inorganic tin(II) and tin(IV) and five organotin compounds [n-butyltin trichloride, di(n-butyltin) dichloride, methyltin trichloride, dimethyltin dichloride and trimethyltin chloride] in reaction systems both with and without hydrogen peroxide (H2O2) content. The tin compounds tested in this study did not induce DNA breakage in the absence of hydrogen peroxide. Divalent inorganic tin (SnCl2) and tetravalent inorganic tin (SnCl4) caused DNA breakage in the presence of hydrogen peroxide (10 mM), and the DNA damage activity of inorganic tin was much more potent in divalent inorganic tin (SnCl2) than in tetravalent inorganic tin (SnCl4). Divalent inorganic tin (SnCl2) induced DNA breakage in a concentration-dependent fashion at concentrations greater than 0.1 mM of SnCl2 in the presence of hydrogen peroxide (10 mM). DNA breakage was not caused by n-butyltin compounds and methyltin compounds either in the presence or in the absence of hydrogen peroxide. 相似文献
4.
The structure of senecicannabine(), a new mcrocyclic pyrrolizidine alkaloid isolated from , has been established by chemical study and X-ray analysis. 相似文献
5.
Treatment of trifluoroacetaldehyde N,O-acetal with diazoacetate in the presence of a Lewis acid furnished CF3-substituted aziridinecarboxylates in good yields. Both cis and trans isomers were obtained stereoselectively by the proper choice of the ester substituents. Use of a chiral diazoacetate derived from (R)-pantolactone led to highly diastereoselective aziridination (94% de). 相似文献
6.
Summary
Vacuum Fusion Determination of Micro-quantities of Bulk Gases in Low Carbon Iron Without an Effect of Surface Gases
Micro-quantities of bulk and surface oxygen and hydrogen in low carbon iron was simultaneously determined by the surface-area-variation method using vacuum fusion analysis. Among the difference of three surface treatments, silicon carbide abrasive, electropolishing and hydrogen reduction methods, bulk oxygen and hydrogen were in agreement within their errors, however, surface oxygen and hydrogen were influenced from the surface treatments. Even in the case of electropolishing, which gave the smallest surface oxygen value, bulk oxygen less than 10g/g is needed to discriminate from the surface oxygen. Bulk hydrogen of 0.03g/g was determined without the effect of surface hydrogen in the hydrogen reduction treatment. 相似文献
7.
The state of an arsenic layer electrodeposited at various potentials on platinum electrodes has been examined electrochemically. The relation between the state and the electrocatalytic activity for hydrogen evolution has been investigated. The number of vacant sites have been found to increase with lowering of the deposition potential. The activity has been found to depend not on the amount of deposited arsenic but on the number of vacant sites. The difference in the effects of arsenic and of copper on hydrogen evolution is pointed out. This is attributed to the difference in the affinity of the ad-atoms for hydrogen. 相似文献
8.
K Takada M Oh-hashi Y Furuya H Yoshikawa S Muranishi 《Chemical & pharmaceutical bulletin》1989,37(2):471-474
Solid dispersions composed of three components, ciclosporin A (CiA), surfactant (HCO-60) and a pharmaceutical additive, were prepared. As an additive, cellulose acetate phthalate (CAP), methacrylic acid and methacrylic acid methylester copolymer (Eudragit L-100) and hydroxypropylmethylcellulose phthalate (HP-55), which are generally used as enteric coating materials, were employed. The dissolution behavior of CiA from these enteric solid-dispersion system was studied according to the paddle method of JP XI in comparison with that of Sandimmun, an olive oily CiA solution as a reference. Solid dispersion of CiA preparation did not dissolve in the 1st test fluid (pH 1.2) in 2 h. In the 2nd fluid (pH 6.8), about 80% of CiA was dissolved within 12 min, though the dissolution rate was dependent on both the quality and quantity of the additives. An in vivo systemic and lymphatic availability study was performed with rats whose carotid artery and thoracic lymph duct were cannulated. After intrastomach administration of each CiA preparation to rats at a dose of 7 mg/kg, blood and lymph samples were collected for 6 h. One of the HP-55 preparations gave the highest plasma CiA level, Cmax = 0.99 +/- 0.20 (S.E., n = 4) micrograms/ml, and also showed the highest lymphatic availability, the percentage of dose delivered to the lymphatics in 6 h was 1.98 +/- 0.10% and the maximum lymph CiA level was 76.8 +/- 12.86 micrograms/ml. Lymphatic availability of CiA from Sandimmun was 0.78 +/- 0.11% and the peak plasma CiA level was 0.46 +/- 0.10 microgram/ml.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
9.
Hydrogen evolution on a platinum electrode decays against Xpt with the deposition of Sn ad-atoms and Pb ad-atoms in the same way as it decays with that of Ge ad-atoms, in which all of these ad-atoms occupy two platinum sites. In general the decay depends on the number of sites occupied by an atom of the ad-atom species.The potential ranges for oxygen adsorption by Sn ad-atoms and Pb ad-atoms are 0.45 to 1.24 V and 0.48 to 0.77 V, respectively, but the oxygen adsorbed by the latter ad-atoms is very small in amount. 相似文献
10.
Murakami K Irie K Ohigashi H Hara H Nagao M Shimizu T Shirasawa T 《Journal of the American Chemical Society》2005,127(43):15168-15174
Amyloid fibrils mainly consist of 40-mer and 42-mer peptides (Abeta40, Abeta42). Abeta42 is believed to play a crucial role in the pathogenesis of Alzheimer's disease because its aggregative ability and neurotoxicity are considerably greater than those of Abeta40. The neurotoxicity of Abeta peptides involving the generation of free radicals is closely related to the S-oxidized radical cation of Met-35. However, the cation's origin and mechanism of stabilization remain unclear. Recently, structural models of fibrillar Abeta42 and Abeta40 based on systematic proline replacement have been proposed by our group [Morimoto, A.; et al. J. Biol. Chem. 2004, 279, 52781] and Wetzel's group [Williams, A. D.; et al. J. Mol. Biol. 2004, 335, 833], respectively. A major difference between these models is that our model of Abeta42 has a C-terminal beta-sheet region. Our biophysical study on Abeta42 using electron spin resonance (ESR) suggests that the S-oxidized radical cation of Met-35 could be generated by the reduction of the tyrosyl radical at Tyr-10 through a turn structure at positions 22 and 23, and stabilized by a C-terminal carboxylate anion through an intramolecular beta-sheet at positions 35-37 and 40-42 to form a C-terminal core that would lead to aggregation. A time-course analysis of the generation of radicals using ESR suggests that stabilization of the radicals by aggregation might be a main reason for the long-lasting oxidative stress of Abeta42. In contrast, the S-oxidized radical cation of Abeta40 is too short-lived to induce potent neurotoxicity because no such stabilization of radicals occurs in Abeta40. 相似文献