全文获取类型
收费全文 | 740篇 |
免费 | 168篇 |
国内免费 | 100篇 |
专业分类
化学 | 396篇 |
晶体学 | 5篇 |
力学 | 5篇 |
综合类 | 28篇 |
数学 | 27篇 |
物理学 | 547篇 |
出版年
2024年 | 2篇 |
2023年 | 2篇 |
2022年 | 23篇 |
2021年 | 23篇 |
2020年 | 29篇 |
2019年 | 21篇 |
2018年 | 21篇 |
2017年 | 13篇 |
2016年 | 27篇 |
2015年 | 31篇 |
2014年 | 25篇 |
2013年 | 71篇 |
2012年 | 44篇 |
2011年 | 44篇 |
2010年 | 38篇 |
2009年 | 44篇 |
2008年 | 56篇 |
2007年 | 39篇 |
2006年 | 68篇 |
2005年 | 45篇 |
2004年 | 28篇 |
2003年 | 40篇 |
2002年 | 21篇 |
2001年 | 24篇 |
2000年 | 42篇 |
1999年 | 28篇 |
1998年 | 31篇 |
1997年 | 20篇 |
1996年 | 21篇 |
1995年 | 12篇 |
1994年 | 9篇 |
1993年 | 8篇 |
1992年 | 9篇 |
1991年 | 8篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1976年 | 3篇 |
1975年 | 7篇 |
1974年 | 8篇 |
排序方式: 共有1008条查询结果,搜索用时 0 毫秒
1.
2.
A complete study of the spectrum of a finite-dimensional Bose operator is carried out in the paper. The cases in which the
spectrum is discrete or continuous are studied.
Translated fromMatematicheskie Zametki, Vol. 61, No. 6, pp. 835–854, June, 1997.
Translated by A. M. Chebotarev 相似文献
3.
G. K. Shenoy 《Hyperfine Interactions》2006,170(1-3):5-13
Stanley L. Ruby (1924–2004) made major contributions to Mössbauer spectroscopy and was the first to suggest the feasibility of observing the Mössbauer effect using synchrotron radiation. In this article we recall his scientific legacy that have inspired his scientific colleagues. 相似文献
4.
Corrosion-related defects of pure iron were investigated by measuring Doppler broadening energy spectra (DBES) of positron annihilation and positron annihilation lifetime (PAL). Defect profiles of the S-parameter from DBES as a function of positron incident energy up to 30 keV (i.e. ∼1 μm depth) were analyzed. The DBES data show that S-parameter increases as a function of positron incident energy (mean depth) after corrosion, and the increase in the S-parameter is larger near the surface than in the bulk due to corrosion. Furthermore, information on defect size from PAL data as a function of positron incident energy up to 10 keV (i.e. ∼0.2 μm depth) was analyzed. In the two-state trapping model, the lifetime τ2 = 500 ps is ascribed to annihilation of positrons in voids with a size of the order of nanometer. τ1, which decreases with depth from the surface to the bulk, is ascribed to the annihilation of positrons in dislocations and three-dimensional vacancy clusters. The corroded samples show a significant increase in τ1 and the intensity I2, and near the surface the corroded iron introduces both voids and large-size three-dimensional vacancy clusters. The size of vacancy clusters decreases with depth. 相似文献
5.
M. D. Zipper G. P. Simon P. Cherry A. J. Hill 《Journal of Polymer Science.Polymer Physics》1994,32(7):1237-1247
Homopolymers and blends of polycarbonate/ThermX have been investigated by differential scanning calorimetry, dynamic mechanical analysis, density measurements, and positron annihilation lifetime spectroscopy. The study focuses on the chain mobility and free volume in the amorphous miscible regions of the blends and how this mobility and free volume are affected by increasing crystallinity. It is proposed that judicious annealing, which results in increasing crystallinity (while avoiding ageing or transesterification), induces a constraint on the amorphous region leading to an increase in Tg and coalescence of free volume sites. © 1994 John Wiley & Sons, Inc. 相似文献
6.
The new research reactor FRM-II near Munich has a strong positron source, which delivers an intense, nearly monoenergetic positron beam. Our positron systems, the pulsed low energy positron source (PLEPS) and the scanning positron microscope (SPM) will be operated at this beam. Some aspects of matching these systems to the new positron source will be discussed.Considerable improvements are expected, e.g. more than 105 s−1 recorded events at PLEPS and sub-micrometre resolution at SPM. They will enable investigations in so far inaccessible problems like the evaluation of annihilation characteristics and trapping constants of individual defects or studies of fast dynamical processes. In applied materials science complex defect structures will be studied which demand a resolution into many differing lifetimes, e.g. fractured specimens, wear, corrosion, etc. Also large series of measurements at small systematic modifications are planned. There is also the opportunity to analyse in addition the chemical microstructure of the specimens by means of a hydrogen microprobe and other ion beam techniques available close to FRM-II at the Technical University of Munich. 相似文献
7.
A. M. Chebotarev 《Mathematical Notes》1996,60(5):544-561
We prove that the Hudson-Parthasarathy equation corresponds, up to unitary equivalence, to the strong resolvent limit of Schrödinger Hamiltonians in Fock space and that the symmetric form of this equation corresponds to the weak limit of the Schrödinger Hamiltonians.Translated fromMatematicheskie Zametki, Vol. 60, No. 5, pp. 726–750, November, 1996. 相似文献
8.
Jakub Čížek Ivan Procházka Radomír Kužel Rinat K. Islamgaliev 《Monatshefte für Chemie / Chemical Monthly》2002,133(6):873-887
Summary. Ultra-fine grained (UFG) Cu (grain size 80 nm) containing 0.5 wt.% Al2O3 nanoparticles (size 20 nm) was prepared by high pressure torsion (HPT). Positron lifetime spectroscopy was employed to characterize
the microstructure of this material, especially with respect to types and concentration of lattice defects. The evolution
of microstructure with increasing temperature was studied by positron lifetime spectroscopy and X-ray diffraction measurements.
The thermal stability of the Cu + 0.5 wt.% Al2O3 nanocomposite was compared with that of pure UFG Cu prepared by the same technique. The processes taking place during thermal
recovery of the initial nanoscale structure in both studied materials are described.
Received October 5, 2001. Accepted (revised) December 20, 2001 相似文献
9.
Chaninart Sakulpisuti Putthiporn Charoenphun Wichana Chamroonrat 《Molecules (Basel, Switzerland)》2022,27(15)
Differentiated thyroid cancer (DTC), arising from thyroid follicular epithelial cells, is the most common type of thyroid cancer. Despite the well-known utilization of radioiodine treatment in DTC, i.e., iodine-131, radioiodine imaging in DTC is typically performed with iodine-123 and iodine-131, with the current hybrid scanner performing single photon emission tomography/computed tomography (SPECT/CT). Positron emission tomography/computed tomography (PET/CT) provides superior visualization and quantification of functions at the molecular level; thus, lesion assessment can be improved compared to that of SPECT/CT. Various types of cancer, including radioiodine-refractory DTC, can be detected by 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG), the most well-known and widely used PET radiopharmaceutical. Several other PET radiopharmaceuticals have been developed, although some are limited in availability despite their potential clinical utilizations. This article aims to summarize PET radiopharmaceuticals in DTC, focusing on molecular pathways and applications. 相似文献
10.
Inês C. F. Fonseca Miguel Castelo-Branco Cludia Cavadas Antero J. Abrunhosa 《Molecules (Basel, Switzerland)》2022,27(12)
Neuropeptide Y (NPY) is a vastly studied biological peptide with numerous physiological functions that activate the NPY receptor family (Y1, Y2, Y4 and Y5). Moreover, these receptors are correlated with the pathophysiology of several diseases such as feeding disorders, anxiety, metabolic diseases, neurodegenerative diseases, some types of cancers and others. In order to deepen the knowledge of NPY receptors’ functions and molecular mechanisms, neuroimaging techniques such as positron emission tomography (PET) have been used. The development of new radiotracers for the different NPY receptors and their subsequent PET studies have led to significant insights into molecular mechanisms involving NPY receptors. This article provides a systematic review of the imaging biomarkers that have been developed as PET tracers in order to study the NPY receptor family. 相似文献