全文获取类型
收费全文 | 10780篇 |
免费 | 1798篇 |
国内免费 | 1409篇 |
专业分类
化学 | 6913篇 |
晶体学 | 228篇 |
力学 | 563篇 |
综合类 | 102篇 |
数学 | 694篇 |
物理学 | 5487篇 |
出版年
2024年 | 28篇 |
2023年 | 93篇 |
2022年 | 229篇 |
2021年 | 279篇 |
2020年 | 337篇 |
2019年 | 339篇 |
2018年 | 322篇 |
2017年 | 347篇 |
2016年 | 461篇 |
2015年 | 394篇 |
2014年 | 456篇 |
2013年 | 1302篇 |
2012年 | 616篇 |
2011年 | 699篇 |
2010年 | 537篇 |
2009年 | 679篇 |
2008年 | 646篇 |
2007年 | 615篇 |
2006年 | 642篇 |
2005年 | 582篇 |
2004年 | 527篇 |
2003年 | 513篇 |
2002年 | 444篇 |
2001年 | 312篇 |
2000年 | 384篇 |
1999年 | 306篇 |
1998年 | 222篇 |
1997年 | 214篇 |
1996年 | 218篇 |
1995年 | 150篇 |
1994年 | 176篇 |
1993年 | 140篇 |
1992年 | 117篇 |
1991年 | 105篇 |
1990年 | 78篇 |
1989年 | 69篇 |
1988年 | 58篇 |
1987年 | 44篇 |
1986年 | 50篇 |
1985年 | 44篇 |
1984年 | 49篇 |
1983年 | 11篇 |
1982年 | 24篇 |
1981年 | 22篇 |
1980年 | 15篇 |
1979年 | 17篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1976年 | 7篇 |
1973年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Hierarchical structure in polymer‐based drug delivery systems as probed by calorimetric measurements
Pascale Valot Nathalie Sintes‐Zydowicz Jean‐Marie Nedelec Mohamed Baba 《Journal of Polymer Science.Polymer Physics》2010,48(18):1939-1945
Thermoporosimetry (TPM), a differential scanning calorimetry technique that relies on the shift of transition temperatures caused by the confinement of liquids, was applied to elucidate the complex morphology of drug‐loaded polymeric microcapsules prepared by the emulsion solvent evaporation method. For the very first time, TPM has been applied simultaneously with two liquids as structural probes. It was found that Miglyol, which dissolves the selected drug (Ibuprofen), is confined inside vesicles having a mean radius of 26.3 nm, whereas water, which is the continuous phase, is trapped inside a swollen polymeric network of Eudragit with an average mesh radius of 1.7 nm. A proposed hierarchical structure is given, which predicts that Eudragit microcapsules are formed from a collection of inert oil vesicles partitioned by polymeric Eudragit membranes swollen by water. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1939–1945, 2010 相似文献
992.
993.
Toshiaki Shirakawa Hajime Ichimura Isao Ikemoto 《Molecular Crystals and Liquid Crystals》2013,570(1-4):101-107
Pressure-volume isotherms for 4-(trans-4-butylcylohexyl)benzonitrile were measured by means of piston-cylinder method. This substance has a monotropic nematic phase at atmospheric pressure. But over a pressure, the nature of isotropic to nematic phase transition changed from monotropic to enantiotropic phase transition. It is the first observation in P-V-T experiments that the monotropic isotropic-nematic transition changes enantiotropic under pressure. 相似文献
994.
995.
Wolfgang Scherer Prof. Dr. Christoph Hauf Dipl.‐Phys. Manuel Presnitz Dipl.‐Phys. Ernst‐Wilhelm Scheidt Dr. Georg Eickerling Dr. Volker Eyert Dr. Rolf‐Dieter Hoffmann Dr. Ute C. Rodewald Dipl.‐Ing. Adrienne Hammerschmidt Dr. Christian Vogt Dr. Rainer Pöttgen Prof. Dr. 《Angewandte Chemie (International ed. in English)》2010,49(9):1578-1582
996.
Separation-induced boundary layer transition: Modeling with a non-linear eddy-viscosity model coupled with the laminar kinetic energy equation 总被引:1,自引:0,他引:1
Z. Vlahostergios K. Yakinthos A. Goulas 《International Journal of Heat and Fluid Flow》2009,30(4):617-636
We present an effort to model the separation-induced transition on a flat plate with a semi-circular leading edge, using a cubic non-linear eddy-viscosity model combined with the laminar kinetic energy. A non-linear model, compared to a linear one, has the advantage to resolve the anisotropic behavior of the Reynolds-stresses in the near-wall region and it provides a more accurate expression for the generation of turbulence in the transport equation of the turbulence kinetic energy. Although in its original formulation the model is not able to accurately predict the separation-induced transition, the inclusion of the laminar kinetic energy increases its accuracy. The adoption of the laminar kinetic energy by the non-linear model is presented in detail, together with some additional modifications required for the adaption of the laminar kinetic energy into the basic concepts of the non-linear eddy-viscosity model. The computational results using the proposed combined model are shown together with the ones obtained using an isotropic linear eddy-viscosity model, which adopts also the laminar kinetic energy concept and in comparison with the existing experimental data. 相似文献
997.
Nylon I I is a high-performance semicrystalline polymer which was used widely in manyfields. In recent years, the curious ferroelectric and piezoelectric propel'ties of nylon I Iwere foundl'2. It is well known that piezoelectricity is related to the crystal form ofNylon I 1.The sample was mounteds in a capillary (diameter was Zmm) within a small ovenwith mica windows. The scattered intensity was recorded from Q = 0.2 to 6.5 A-] (Q =ursine/~) using steps of AQ=o.o5A-'. The values of the p… 相似文献
998.
Studies of temperature dependences of ac magnetization were carried out for a superconducting lead-porous glass nanocomposite. Double peaks were found on the imaginary part of ac magnetization which were accompanied with double steps on the real part. The lower-temperature anomalies in ac magnetization differed noticeably when they were obtained upon cooling and warming. The double peaks were treated as two phase transitions in the vortex system: the liquid-solid transition which occurs close to the onset of superconductivity and solid-solid one which is triggered by superconductivity in confined lead islands. 相似文献
999.
1000.
In this paper, we study Web cache hit rates by introducing a birth–death model. A system consisting of a single Web server with a single cache stores Web pages that are classified as hot pages (popular pages) and cold pages (less popular pages). Given requested probabilities for each class, the stochastic model provides the mean hit rate for a random replacement algorithm and the upper and low bounds for other algorithms. Numerical results from the analysis are validated using the output of simulation programs that utilize the LRU algorithm. 相似文献