全文获取类型
收费全文 | 248篇 |
免费 | 1篇 |
专业分类
化学 | 107篇 |
晶体学 | 2篇 |
力学 | 3篇 |
数学 | 9篇 |
物理学 | 128篇 |
出版年
2019年 | 2篇 |
2017年 | 4篇 |
2016年 | 2篇 |
2013年 | 11篇 |
2012年 | 6篇 |
2011年 | 9篇 |
2010年 | 5篇 |
2009年 | 6篇 |
2008年 | 4篇 |
2007年 | 6篇 |
2006年 | 11篇 |
2005年 | 7篇 |
2004年 | 8篇 |
2003年 | 6篇 |
2002年 | 32篇 |
2001年 | 8篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 2篇 |
1977年 | 4篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1972年 | 2篇 |
1971年 | 3篇 |
1970年 | 3篇 |
1969年 | 6篇 |
1967年 | 2篇 |
1966年 | 2篇 |
1962年 | 2篇 |
1958年 | 1篇 |
1956年 | 1篇 |
1939年 | 1篇 |
1934年 | 1篇 |
1929年 | 1篇 |
1909年 | 1篇 |
1889年 | 2篇 |
排序方式: 共有249条查询结果,搜索用时 15 毫秒
41.
Mamedov I Engelmann J Eschenko O Beyerlein M Logothetis NK 《Chemical communications (Cambridge, England)》2012,48(22):2755-2757
A Gd(3+) based paramagnetic dextran conjugate has been developed, which enables the tracking of neuroanatomical connectivity in the brain by both MR and optical imaging. Cell studies and subsequent in vivo experiments in rodents demonstrate efficient internalisation and transport properties of the new tracer molecule. 相似文献
42.
Eyad Mallah Kamal Sweidan Jörn Engelmann Manfred Steimann Norbert Kuhn Martin E. Maier 《Tetrahedron》2012,68(4):1005-1010
We describe simple, convenient and high-yielding nucleophilic substitution reactions to synthesize new derivatives of 1,3-dimethylbarbituric acid (1a). Based on its active C5 position, condensing 1a with sulfuryl chloride gives the corresponding 5,5-dichloro-1,3-dimethylbarbituric acid (13). The latter was reacted with silver nitrite and potassium cyanide to afford 5-chloro-5-nitro-1,3-dimethylbarbituric acid (14) and 5-cyano-1,3-dimethylbarbiturate (17), respectively. Furthermore, by employing the nucleophilic character of 2,3-dihydro-1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (8) the obtained compounds 13 and 14 have been converted to 2-chloro-1,3-diisopropyl-4,5-dimethyl-1H-imidazol-3-ium-1,3-dimethyl-5-nitro-1,3-dimethylbarbiturate (18) and 1,3-dimethylbarbituric acid trimer (21), respectively. X-ray structures for compounds 13, 14, 17, 18 and 21 were determined. 相似文献
43.
Two cases of bilateral vocal fold immobility (VFI) after identification and preservation of the recurrent laryngeal nerves (RLNs) required tracheotomy until vocal fold recovery. The first patient underwent thyroid surgery without preoperative or postoperative evaluation of the vocal folds, administration of postoperative intravenous steroids, or electrophysiologic monitoring of the RLNs, whereas the second patient underwent a thyroid procedure in which all of the aforementioned were executed. Preoperative and postoperative clinical evaluation of the RLNs is strongly suggested in patients undergoing thyroid surgery, especially revision surgery. Patients potentially undergoing total thyroidectomy should be counseled about the remote chance of airway obstruction and should be properly selected for this operation. Subclinical stretching of the RLNs or ischemia from the endotracheal tube cuff can result in unilateral VFI, and rarely bilateral VFI, requiring reintubation, tracheotomy, or vocal fold lateralization. Electrophysiologic monitoring may not always predict bilateral VFI. 相似文献
44.
F. Mayolet P. Reimers Ch. Engelmann 《Journal of Radioanalytical and Nuclear Chemistry》1972,12(2):115-128
The carbon and nitrogen activation curves were determined for the nuclear reactions12C(α, n)15O and14N(d, n)15O, within the limits of the following maximum energies: 40 MeV for α-particles, and 21 MeV for deuterons. Inferences are made concerning the potential possibilities of these activation methods, from the sensitivity aspects, for the determination of carbon and nitrogen, with reference to the problem of the main interferences which have also been studied experimentally. The chemical separation process used to isolate15O after irradiation is described. Concrete examples of carbon and nitrogen determinations by these methods are given. 相似文献
45.
46.
Ch Engelmann G. Filippi J. Gosset F. Moreau 《Journal of Radioanalytical and Nuclear Chemistry》1977,37(2):559-570
The photonuclear reactions used for this isotopic analysis are as follows:16O(γ, n)15O threshold energy 15.7 MeV;18O(γ, p)17N threshold energy 16.3 MeV.15O is a pure β+ emitter of half-life 2.03 minutes, whereas17N presents a 4.2 second neutron emission. The principle of the method is founded on the simultaneous measurement of the above
characteristic radioactivities, the intensities of which are proportional to the respective quantities of16O and18O present in the irradiated sample. The potentialities of this new oxygen isotope analysis method, based on the use of an
electron accelerator, are described. Detection limit of 0.1 μg18O is easily attainable. The equipment designed and built to industrialise this technique is described. It allows a hundred
samples to be analysed automatically, the accelerator, detection instruments and pneumatic transfer circuits being controlled
by a logic system linked to an electronic chronometer. 相似文献
47.
Stability and convergence of the spectral Lagrange-Galerkin method for mixed periodic/non-periodic convection-dominated diffusion problems 总被引:1,自引:0,他引:1
We present a convergence analysis of the spectral Lagrange-Galerkinmethod for mixed periodic/non-periodic convection-diffusionproblems. The scheme is unconditionally stable, independentof the diffusion coefficient, even in the case when numericalquadrature is used. The theoretical predictions are illustratedby a series of numerical experiments. For the periodic case,our results present a significant improvement on those givenby Süli & Ware (1991) SIAM J. Numer.Anal.28, 423-445). 相似文献
48.
Photonuclear activation with 18 and 35 MeV bremsstrahlung beams and gamma ray spectrometry has been used to determine the
concentrations of 14 elements in human hair. A careful study of interferences made possible a nondestructive analysis with
practical limits of detection between 0.1 and 100 μg·g.
相似文献
49.
Synthesis and Structure of Tetrafluoroaurates(III) MI[AuF4] with MI = Li, Rb Single crystal investigations on Rb[AuF4], light yellow, confirm the tetragonal unit cell (K[BrF4]-type) with a = 618.2(1) and c = 1191(1) pm, Z = 4, space group I 4/mcm-D (No. 140). Li[AuF4], light yellow too, crystallizes monoclinic with a = 485.32(7), b = 634.29(8), c = 1004.43(13) pm, β = 92.759(12), Z = 4; space group P 2/c-C (No. 13). The structure of Li[AuF4] is related to the Rb[AuF4]-type of structure. 相似文献
50.