全文获取类型
收费全文 | 390篇 |
免费 | 55篇 |
国内免费 | 14篇 |
专业分类
化学 | 54篇 |
晶体学 | 1篇 |
力学 | 123篇 |
综合类 | 7篇 |
数学 | 30篇 |
物理学 | 244篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 10篇 |
2021年 | 12篇 |
2020年 | 15篇 |
2019年 | 11篇 |
2018年 | 13篇 |
2017年 | 12篇 |
2016年 | 19篇 |
2015年 | 9篇 |
2014年 | 13篇 |
2013年 | 22篇 |
2012年 | 14篇 |
2011年 | 27篇 |
2010年 | 22篇 |
2009年 | 13篇 |
2008年 | 28篇 |
2007年 | 21篇 |
2006年 | 16篇 |
2005年 | 14篇 |
2004年 | 21篇 |
2003年 | 27篇 |
2002年 | 17篇 |
2001年 | 7篇 |
2000年 | 11篇 |
1999年 | 8篇 |
1998年 | 9篇 |
1997年 | 7篇 |
1996年 | 10篇 |
1995年 | 6篇 |
1994年 | 2篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 6篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有459条查询结果,搜索用时 15 毫秒
21.
Pankaj S. Joshi 《Pramana》2007,69(1):119-135
We consider here the genericity aspects of spacetime singularities that occur in cosmology and in gravitational collapse.
The singularity theorems (that predict the occurrence of singularities in general relativity) allow the singularities of gravitational
collapse to be either visible to external observers or covered by an event horizon of gravity. It is shown that the visible
singularities that develop as final states of spherical collapse are generic. Some consequences of this fact are discussed.
相似文献
22.
《Comptes Rendus Physique》2013,14(4):352-365
The first generation of ground-based interferometric gravitational wave detectors, LIGO, GEO, and Virgo, have operated and taken data at their design sensitivities over the last few years. The data has been examined for the presence of gravitational wave signals. Presented here is a comprehensive review of the most significant results. The network of detectors is currently being upgraded and extended, providing a large likelihood for observations. These future prospects will also be discussed. 相似文献
23.
Benchuan Zhu Guannan Qian Yuli Xiao Sheng Deng Meng Wang Aiguo Hu 《Journal of polymer science. Part A, Polymer chemistry》2011,49(24):5330-5338
Employing enediynes as crosslinking precursors, a novel yet efficient strategy, namely photo‐triggered Bergman cyclization, was integrated with intramolecular chain collapse to yield polymeric nanoparticles with the size regime below 20 nm. Enediyne motif was designed delicately to possess a high photo‐reactivity, with the double bond locked in a methyl benzoate ring while triple bonds substituted with phenyls. Single electron transfer‐living radical polymerization was conducted to provide linear acrylate copolymers with controlled molecular weights and narrow polydispersities. Poly(butylarylate‐co‐ 5 ) went through UV‐irradiation with a concurrent Bergman cyclization, resulting in well‐defined ultrafine polymeric nanoparticles. Results from NMR, Raman scattering, photoluminescence and UV‐vis spectra corroborated the presence of conjugative structures in the polymeric nanoparticles, indicating the occurrence of photo‐induced Bergman cyclization. A series of other acrylate‐based nanoparticles were investigated to confirm the applicability of such a unique strategy in thermal sensitive but UV‐stable polymeric structures, making photo‐Bergman cyclization a promising tool towards polymeric nanoparticles. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
24.
在对大量的套管全尺寸挤毁试验结果分析的基础上,提出套管外压失稳机理:实际工程中的套管截面不是理想圆,在外压作用下的非圆套管圆周方向上环向应力分布不均匀,有附加弯矩效应;随外压增加,在最大压缩环向应力处达到屈服;当屈服逸到一定程度时,材料由于强度承载力不足而失效,导致套管发生失稳挤毁。基于上述套管强度挤毁准则,分析了理想弹塑性套管在轴向载荷作用下的抗挤强度计算方法,得到较保守的套管挤毁压力计算公式。与试验结果对比表明:导出的计算公式偏差较小,计算精度满足工程要求,失稳强度准则是适用的。 相似文献
25.
The junction conditions for a magnetohydrodynamic fluid sphere undergoing dissipative gravitational collapse in the form of
a radial heat flux with shear are obtained. These conditions extend particular results of earlier treatments. We demonstrate
that the pressure is proportional to the magnitude of the heat flux as is the case in shear-free models. However in our case
the gravitational potentials must be solutions of the Einstein-Maxwell system of equations. The mass function m(v) is increased by a factor related to the charge Q of the radiating star. Physical quantities relating to the local conservation of momentum and surface redshift are obtained. 相似文献
26.
E.B.Manoukian 《理论物理通讯》2013,(12):677-686
The paper represents a rigorous treatment of the underlying quantum theory, not just in words but providing the underlying technical details, as to why matter occupies so large a volume and its intimate connection with the Pauli exclusion principle, as more and more matter is put together, as well as of the contraction or shrinkage of "bosonic matter", upon collapse, for which the Panli exclusion is abolished. From the derived explicit bounds of integrals of powers of the particle number densities, explicit bounds on probabilities of the occurrences of the events just described are extracted. These probabilities lead one to infer the change of the "size" or extension of such matter, upon expansion or contraction, respectively, as their content is increased. 相似文献
27.
《Journal of Polymer Science.Polymer Physics》2018,56(10):778-785
In this work, collapse of poly(N‐isopropyl‐acrylamide) (pNIPAM) grafted on the surface of the optical fiber taper is probed by measuring fluorescence of rhodamine B solution at various temperatures. It is observed that the fluorescence intensity through the taper shows a nonlinear response to temperature. According to the optical model for the special designed taper, it is realized that the nonlinear response results from changing in effective refractive index of interfacial layer between taper and solution. Analysis on relationship between signal change and collapse process reveals a springback process during the collapse of pNIPAM chains. Such a novel phenomenon is further investigated on method for fluorescence measurement and molecular weight of the polymer. These results have not only revealed details of the collapse, but also establish a novel technique for study the collapse of thermal sensitive polymers on the surface. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 778–785 相似文献
28.
29.
Mohamed Dawod Michael C. BreadmoreRosanne M. Guijt Paul R. Haddad 《Journal of chromatography. A》2010,1217(3):386-393
Three strategies were investigated for the simultaneous separation and on-line preconcentration of charged and neutral hypolipidaemic drugs in micellar electrokinetic chromatography (MEKC). A background electrolyte (BGE) consisting of 20 mM ammonium bicarbonate buffer (pH 8.50) and 50 mM sodium dodecyl sulfate (SDS) was used for the separation and on-line preconcentration of the drugs. The efficiencies of sweeping, analyte focusing by micelle collapse (AFMC), and simultaneous field-amplified sample stacking (FASS) and sweeping, were compared for the preconcentration of eight hypolipidaemic drugs in different conductivity sample matrices. When compared with a hydrodynamic injection (5 s at 50 mbar, 0.51% of capillary volume to detection window) of drug mixture prepared in the separation BGE, improvements of detection sensitivity of 60-, 83-, and 80-fold were obtained with sweeping, AFMC and simultaneous FASS and sweeping, respectively, giving limits of detection (LODs) of 50, 36, and 38 μg/L, respectively. The studied techniques showed suitability for focusing different types of analytes having different values of retention factor (k). This is the first report for the separation of different types of hypolipidaemic drugs by capillary electrophoresis (CE). The three methods were validated then applied for the analysis of target analytes in wastewater samples from Hobart city. 相似文献
30.