全文获取类型
收费全文 | 4750篇 |
免费 | 149篇 |
国内免费 | 33篇 |
专业分类
化学 | 3303篇 |
晶体学 | 38篇 |
力学 | 79篇 |
数学 | 654篇 |
物理学 | 858篇 |
出版年
2023年 | 27篇 |
2022年 | 87篇 |
2021年 | 108篇 |
2020年 | 108篇 |
2019年 | 99篇 |
2018年 | 94篇 |
2017年 | 59篇 |
2016年 | 160篇 |
2015年 | 130篇 |
2014年 | 153篇 |
2013年 | 254篇 |
2012年 | 318篇 |
2011年 | 400篇 |
2010年 | 190篇 |
2009年 | 164篇 |
2008年 | 282篇 |
2007年 | 262篇 |
2006年 | 264篇 |
2005年 | 231篇 |
2004年 | 182篇 |
2003年 | 166篇 |
2002年 | 147篇 |
2001年 | 57篇 |
2000年 | 67篇 |
1999年 | 41篇 |
1998年 | 30篇 |
1997年 | 43篇 |
1996年 | 67篇 |
1995年 | 52篇 |
1994年 | 25篇 |
1993年 | 38篇 |
1992年 | 38篇 |
1991年 | 35篇 |
1990年 | 24篇 |
1989年 | 22篇 |
1988年 | 27篇 |
1987年 | 19篇 |
1986年 | 21篇 |
1985年 | 32篇 |
1984年 | 24篇 |
1983年 | 21篇 |
1982年 | 35篇 |
1981年 | 29篇 |
1980年 | 31篇 |
1979年 | 25篇 |
1978年 | 27篇 |
1977年 | 15篇 |
1975年 | 17篇 |
1974年 | 13篇 |
1973年 | 19篇 |
排序方式: 共有4932条查询结果,搜索用时 15 毫秒
1.
Adam Kiersnowski Jochen S. Gutmann Jacek Pigłowski 《Journal of Polymer Science.Polymer Physics》2007,45(17):2350-2367
ε‐caprolactone was polymerized in the presence of neat montmorillonite or organomontmorillonites to obtain a variety of poly(ε‐caprolactone) (PCL)‐based systems loaded with 10 wt % of the silicates. The materials were thoroughly investigated by different X‐ray scattering techniques to determine factors affecting structure of the systems. For one of the nanocomposites it was found that varying the temperature in the range corresponding to crystallization of PCL causes reversible changes in the interlayer distance of the organoclay. Extensive experimental and literature studies on this phenomenon provided clues indicating that this effect might be a result of two‐dimensional ordering of PCL chains inside the galleries of the silicate. Small angle X‐ray scattering and wide angle X‐ray scattering investigation of filaments oriented above melting point of PCL revealed that polymer lamellae were oriented perpendicularly to particles of unmodified silicate, while in PCL/organoclay systems they were found parallel to clay tactoids. Calorimetric and microscopic studies shown that clay particles are effective nucleating agents. In the nanocomposites, PCL crystallized 20‐fold faster than in the neat polymer. The crystallization rate in nanocomposites was also significantly higher than in microcomposite. Further research provided an insight how the presence of the filler affects crystalline fraction and spherulitic structure of the polymer matrix in the investigated systems. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2350–2367, 2007 相似文献
2.
In this paper a further refinement of Dade's projective conjecture, due to Boltje, is presented. This new statement includes ideas first published by Isaacs and Navarro as well as the recent contractibility version of Alperin's conjecture introduced by Boltje. Leaning heavily on the work of Robinson, weaker forms of the conjecture are proved in the case of p-solvable groups. 相似文献
3.
4.
Upper rim substituted tetraiodo calix[4]arenes are coupled to a variety of acrylamides using the palladium catalysed Heck reaction. Tetra-acrylamido upper rim substituted calix[4]arenes are obtained in good yields with exceptionally high stereoselectivity, to produce the all-trans isomers. Tetra-acrylamido calix[4]arenes derived from secondary acrylamides are shown to dimerise via eight hydrogen bonds to form dimeric capsules, which are able to include small organic molecules. 相似文献
5.
The method described is based on the extraction of uranium with a chloroform solution of phenylacetic acid from slightly acidic solution containing nitrilotriacetic acid, which masks all interfering metals. After stripping into very dilute hydrochloric acid, uranium is reduced with ascorbic acid and determined complexometrically. The method permits reliable determination of uranium in the presence of all quadri-, ter- and bivalent metals investigated, molybdenum(VI), tungsten(VI), and vanadium(V). 相似文献
6.
7.
G. Adam 《Colloid and polymer science》1960,172(2):132-141
Zusammenfassung Mit Hilfe freier Torsionsschwingungen wurde der Schubmodul von vernetztem und gequollenem Polystyrol bei 1 Hz in Abh?ngigkeit
von der Temperatur gemessen. Die Temperatur wurde zwischen −120° C und 200° C variiert.
Aus Ergebnissen verschiedener physikalischer Untersuchungsverfahren werden Vorstellungen über die zwischenmolekulare Struktur
des glasigen Polystyrols hergeleitet. Sie gestatten eine qualitative molekulare Interpretation der mechanisch-thermischen
Messungen sowie des Einflusses von chemischer Variation und Weichmachung auf den Einfriervorgang. 相似文献
8.
The Ramanujan Journal - For two varieties of dimension 5 constructed as double covers of $$\mathbb {P}^5$$ branched along the union of 12 hyperplanes, we prove that the number of points... 相似文献
9.
P. Abreu W. Adam E. Agasi I. Ajinenko R. Aleksan G. D. Alekseev P. P. Allport S. Almehed F. M. L. Almeida S. J. Alvsvaag et al. 《Zeitschrift fur Physik C Particles and Fields》1995,66(3):341-354
The forward-backward asymmetries for the processes
and
at theZ resonance are measured using identifiedD
*± mesons. In 905,000 selected hadronic events, taken in 1991 and 1992 with the DEL-PHI detector at LEP, 4757D
*+D
0+ decays are reconstructed. Thec andb quark forward-backward asymmetries are determined to be:
相似文献
10.
P. Abreu W. Adam T. Adye E. Agasi I. Ajinenko R. Aleksan G. D. Alekseev P. P. Allport S. Almehed S. J. Alvsvaag et al. 《Zeitschrift fur Physik C Particles and Fields》1995,68(3):353-362
The decayB
*B
has been observed with the DELPHI detector at LEP, where theB
* meson is produced inZ boson decays. The combination of inclusively reconstructedB mesons with well-measured converted photons yields a measurement of the flavour-averagedB
*-B mass difference of 45.5±0.3 (stat.) ±0.8 (syst.) MeV/c2. 95% confidence level upper limits at 6 MeV/c2 are placed on both the isospin (i.e.B
+-B
0) and theB
s
-B
ud
splitting of the mass difference. The production ratio ofB
* toB mesons inZ decays is measured to be 0.72±0.03 (stat.) ±0.06 (syst.). Limits on the production cross-section of other hypothetical excitedB hadron states decaying radiatively are established. The differentialB
* cross section has been measured to be in good agreement with the averageb fragmentation, yielding an average fractionalB
* energy of x
E
=0.695±0.009 (stat.) ±0.013 (syst.). From the decay angular distribution the relative contribution of longitudinalB
* polarisation states is measured to be L/(L + T) = 0.32 ± 0.04 (stat.) ±0.03 (syst.).CICYT_AEN93-0832 相似文献
|