全文获取类型
收费全文 | 20463篇 |
免费 | 156篇 |
国内免费 | 92篇 |
专业分类
化学 | 10446篇 |
晶体学 | 208篇 |
力学 | 603篇 |
综合类 | 7篇 |
数学 | 1754篇 |
物理学 | 7693篇 |
出版年
2017年 | 157篇 |
2016年 | 246篇 |
2015年 | 167篇 |
2014年 | 270篇 |
2013年 | 855篇 |
2012年 | 585篇 |
2011年 | 644篇 |
2010年 | 473篇 |
2009年 | 483篇 |
2008年 | 633篇 |
2007年 | 685篇 |
2006年 | 650篇 |
2005年 | 584篇 |
2004年 | 520篇 |
2003年 | 487篇 |
2002年 | 473篇 |
2001年 | 700篇 |
2000年 | 528篇 |
1999年 | 435篇 |
1998年 | 355篇 |
1997年 | 333篇 |
1996年 | 297篇 |
1995年 | 386篇 |
1994年 | 343篇 |
1993年 | 307篇 |
1992年 | 344篇 |
1991年 | 371篇 |
1990年 | 353篇 |
1989年 | 347篇 |
1988年 | 324篇 |
1987年 | 321篇 |
1986年 | 321篇 |
1985年 | 395篇 |
1984年 | 402篇 |
1983年 | 296篇 |
1982年 | 322篇 |
1981年 | 342篇 |
1980年 | 321篇 |
1979年 | 320篇 |
1978年 | 335篇 |
1977年 | 312篇 |
1976年 | 329篇 |
1975年 | 285篇 |
1974年 | 278篇 |
1973年 | 296篇 |
1972年 | 176篇 |
1969年 | 158篇 |
1968年 | 188篇 |
1967年 | 334篇 |
1966年 | 287篇 |
排序方式: 共有10000条查询结果,搜索用时 375 毫秒
91.
92.
P. Thomsen-Schmidt K. Hasche G. Ulm K. Herrmann M. Krumrey G. Ade J. Stümpel I. Busch S. Schädlich A. Schindler W. Frank D. Hirsch M. Procop U. Beck 《Applied Physics A: Materials Science & Processing》2004,78(5):645-649
High-accuracy film thickness measurements in the range below 100 nm can be made by various complex methods like spectral ellipsometry (SE), scanning force microscopy (SFM), grazing incidence X-ray reflectometry (GIXR), or X-ray fluorescence analysis (XRF). The measurement results achieved with these methods are based on different interactions between the film and the probe. A key question in nanotechnology is how to achieve consistent results on a level of uncertainty below one nanometre with different techniques.Two different types of thickness standards are realised. Metal film standards for X-ray techniques in the thickness range 10 to 50 nm are calibrated by GIXR with monochromatised synchrotron radiation of 8048 eV. The results obtained at four different facilities show excellent agreement. SiO2 on Si standards for SE and SFM in the thickness range 6 to 1000 nm are calibrated by GIXR with monochromatised synchrotron radiation of 1841 eV and with a metrological SFM. Consistent results within the combined uncertainties are obtained with the two methods. Surfaces and interfaces of both types of standards are additionally investigated by transmission electron microscopy (TEM). PACS 61.10.Kw; 68.55.Jk; 06.20.Fn; 06.60.Mr; 07.79.Lh 相似文献
93.
94.
95.
U. M. Dzhemilev A. G. Ibragimov V. A. D’yakonov R. A. Zinnurova 《Russian Journal of Organic Chemistry》2007,43(2):176-180
Treatment of internal acetylenes and allenes with BuMgHlg (Hlg = Cl, Br) in the presence of Cp2ZrCl2 selectively leads to the formation of substituted magnesacyclopenta-2,4-dienes and alkylidenemagnesacyclopentenes. 相似文献
96.
97.
J M Squirrell R D Schramm A M Paprocki D L Wokosin B D Bavister 《Microscopy and microanalysis》2003,9(3):190-201
We employed multiphoton laser scanning microscopy (MPLSM) to image changes in mitochondrial distribution in living rhesus monkey embryos. This method of imaging does not impair development; thus, the same specimen can be visualized multiple times at various developmental stages. Not only does this increase the amount of information that can be gathered on a single specimen but it permits the correlation of early events with subsequent development in the same specimen. Here we demonstrate the utility of MPLSM for determining changes in mitochondrial organization at various developmental stages and show that rhesus zygotes possess a distinct accumulation of mitochondria between the pronuclei prior to syngamy. We present evidence that suggests that this pronuclear accumulation may be positively correlated with development to the blastocyst stage-in the same embryo-thereby illustrating how MPLSM can be used to correlate cellular dynamics of primate oocytes and early embryos with their developmental potential. Understanding the relationship between mitochondrial distribution and the subsequent development of mammalian embryos, particularly primates, will increase our ability to improve embryo culture technologies, including those used for human assisted reproduction. 相似文献
98.
M.C. Ubaldi V. Stasi U. Colombo D. Piccinin M. Martinelli 《Photonics and Nanostructures》2007,5(2-3):145-148
Roughness reduction of a submicron waveguide profile in chemically amplified negative resist is here performed by proper selection of an alkali-based developer, taking into account that its smaller molecules lead to smoother resist surface by altering the developing mechanism of aggregate extraction performed with standard quaternary ammonium hydroxide. Roughness is then analyzed by means of classical Atomic Force Microscope inspection; furthermore, a non-invasive line edge roughness analysis approach based on top-down scanning electron microscope acquisition gives comparable results, in terms of standard deviation and molecular aggregate periodicity. 相似文献
99.
Preparation and mechanical properties of layers made of recombinant spider silk proteins and silk from silk worm 总被引:1,自引:0,他引:1
F. Junghans M. Morawietz U. Conrad T. Scheibel A. Heilmann U. Spohn 《Applied Physics A: Materials Science & Processing》2006,82(2):253-260
Layers of recombinant spider silks and native silks from silk worms were prepared by spin-coating and casting of various solutions.
FT-IR spectra were recorded to investigate the influence of the different mechanical stress occurring during the preparation
of the silk layers. The solubility of the recombinant spider silk proteins SO1-ELP, C16, AQ24NR3, and of the silk fibroin
from Bombyx mori were investigated in hexafluorisopropanol, ionic liquids and concentrated salt solutions. The morphology and thickness of
the layers were determined by Atomic Force Microscopy (AFM) or with a profilometer. The mechanical behaviour was investigated
by acoustic impedance analysis by using a quartz crystal microbalance (QCMB) as well as by microindentation.
The density of silk layers (d<300 nm) was determined based on AFM and QCMB measurements. At silk layers thicker than 300 nm
significant changes of the half-band-half width can be correlated with increasing energy dissipation. Microhardness measurements
demonstrate that recombinant spider silk and sericine-free Bombyx mori silk layers achieve higher elastic penetration modules EEP and Martens hardness values HM than those of polyethylenterephthalate (PET) and polyetherimide (PEI) foils. 相似文献
100.
Kaon production is studied within the Giessen Boltzmann–Uehling–Uhlenbeck (GiBUU) model. Results are compared with experiment and with other models. The influence of the kaon potential on the kaon azimuthal distributions at SIS energies is considered. We also discuss the role of the many-body collisions at high-density phase of reaction. 相似文献