首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   466篇
  免费   5篇
  国内免费   1篇
化学   256篇
晶体学   7篇
力学   19篇
数学   78篇
物理学   112篇
  2022年   5篇
  2021年   3篇
  2019年   5篇
  2018年   7篇
  2017年   6篇
  2015年   8篇
  2014年   7篇
  2013年   21篇
  2012年   31篇
  2011年   24篇
  2010年   13篇
  2009年   9篇
  2008年   28篇
  2007年   27篇
  2006年   22篇
  2005年   21篇
  2004年   15篇
  2003年   11篇
  2002年   18篇
  2001年   17篇
  2000年   8篇
  1998年   4篇
  1997年   3篇
  1996年   6篇
  1994年   4篇
  1993年   5篇
  1991年   3篇
  1990年   2篇
  1989年   4篇
  1988年   5篇
  1987年   11篇
  1986年   6篇
  1985年   9篇
  1984年   5篇
  1983年   4篇
  1982年   3篇
  1981年   14篇
  1980年   8篇
  1979年   7篇
  1978年   12篇
  1977年   6篇
  1976年   8篇
  1975年   3篇
  1974年   3篇
  1973年   3篇
  1972年   3篇
  1971年   5篇
  1968年   2篇
  1967年   3篇
  1961年   2篇
排序方式: 共有472条查询结果,搜索用时 15 毫秒
31.
Bailly  J. L.  Caso  C.  Chiba  Y.  Dibon  H.  Epp  B.  Ferrando  A.  Fontanelli  F.  Ganguli  S. N.  Gémesy  T.  Gurtu  A.  Hamatsu  R.  Hidas  P.  Hirose  T.  Hrubec  J.  Ivanyshenkov  Yu.  Kageya  T.  Khalatyan  N.  Kistenev  E.  Kita  I.  Kitamura  S.  Kubik  V.  MacNaughton  J.  Malhotra  P. K.  Matsumoto  S.  Mittra  I. S.  Montanet  L.  Neuhofer  G.  Pinter  G.  Porth  P.  Raghavan  R.  Rodrigo  T.  Singh  J.  Squarcia  S.  Takahashi  K.  Tanaka  R.  Tikhonova  L. A.  Trevisan  U.  Yamagata  T.  Zholobov  G.  Zotkin  S. A. 《Zeitschrift fur Physik C Particles and Fields》1989,43(3):341-348
Zeitschrift für Physik C Particles and Fields - Correlations among identically charged pions were measured for pions produced inp p collisions at 360 GeV/c using the EHS spectrometer. The...  相似文献   
32.
Results are presented on inclusive production of ∑+(1385) and ∑?(1385) inK ? p interactions at 110 GeV/c. The inclusive and topological cross sections have been estimated and compared with published results at lower energies. The inclusive cross section of ∑+(1385) seems to decrease with c.m. energy, while that of the ∑?(1385) is nearly constant. The mean charged multiplicity associate to Σ(1385) increases with c.m. energy. The ∑+(1385) is produced both in the target fragmentation region and in the central region where ∑?(1385) is predominantly produced in the central region. Approximately 16% of the Λ's stem from the decay of ∑±(1385) and the kinematic distributions of these Λ's are not very different from the inclusive Λ's.  相似文献   
33.
34.
Photorelease and photoisomerization of trans-cinnamic acid in aqueous CTAB solutions induces a bulk solution viscosity increase and decrease, respectively, triggered by orthogonal irradiation wavelengths.  相似文献   
35.
Several solvent-free processing methods to disperse multiwalled carbon nanotubes (MWCNTs) in bisphenol F-based epoxy resin were investigated, including the use of a microfluidizer (MF), planetary shear mixer (PSM), ultrasonication (US) and combinations. The processed mixture was cured with diethyl toluene diamine. Three complimentary techniques were used to characterize the dispersion of the MWCNTs in cured composite samples: optical microscopy, micro Raman spectroscopy, and scanning electron microscopy (SEM). For sample MF + PSM, optical micrographs and Raman images showed reduced agglomeration and a homogeneous distribution of MWCNTs in the epoxy matrix. SEM analysis of fractured specimen after tensile testing revealed breakage of nanotubes along the fracture surface of the composite. A comparison of the MWCNT dispersion in the epoxy samples processed using different methods showed that a combination of MF and PSM processing yields a more homogeneous sample than the PSM or US + PSM processed samples. Mechanical testing of the composites showed about 15% improvement in the tensile strength of samples processed by the MF + PSM method over other methods. Thermogravimetric analysis (TGA) results showed a small decrease in the onset degradation temperature for poorly dispersed samples produced by PSM compared with the well-mixed samples (MF + PSM). These results strongly suggest that the MF + PSM processing method yield better-dispersed and stronger MWCNT/epoxy composites. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013  相似文献   
36.
In this paper we study the rate at which a rumor spreads through an undirected graph. This study has two important applications in distributed computation: in simple, robust and efficient broadcast protocols, and in the maintenance of replicated databases.  相似文献   
37.
We consider a setting where there is a manufacturer who wants to procure multiple items from a set of suppliers each of whom can supply one or more of these items (bundles). We design an ascending price auction for such a setting which implements the Vickrey–Clarke–Groves outcome and truthful bidding is an ex post Nash equilibrium. Our auction maintains non-linear and non-anonymous prices throughout the auction. This auction has a simple price adjustment step and is easy to implement in practice. As offshoots of this auction, we also suggest other simple auctions (in which truthful bidding is not an equilibrium by suppliers) which may be suitable where incentives to suppliers are not a big concern. Computer simulations of our auction show that it is scalable for the multi-unit case, and has better information revelation properties than its descending auction counterpart.  相似文献   
38.
Field measurements were made of soil density and moisture patterns under different vehicle tire paths with varying external pressures and number of passes. In addition, laboratory index tests were performed to determine the compaction behaviour of the same soil. Using these results, a prediction equation of dry density in terms of applied pressure and moisture content was obtained for the clay soil. A previously developed equation for sandy soil was modified for the complete range of moisture contents encountered. Estimation of shear strength for the clay soil was made using plastic and liquid limits.  相似文献   
39.
A 52 plot experiment was performed during the growing season of 1977 in a Ste. Rosalie clay soil, using a randomized complete-block design with 13 treatments of machinery traffic within each of four blocks. Three vehicle contact pressures, four numbers of tractor passes, and a control of zero traffic were used to relate the growth and yield variables to wheel traffic and the resulting soil compaction. The number of days required for (a) plant emergence, (b) tasselling, and (c) silking were minimum in moderately compacted plots. The plant growth rate monitored at 41, 54, 68, and 105 days from the seeding time was different from plot to plot. Growth models at different times of the season were derived in terms of the wheel traffic variables, and plant and ear moisture content variation with traffic treatment was investigated. Yield and ear yield increased with increases in machine contact pressure and passes reaching a peak around 500 kPa and dropped off for further increases. The reduction in yield was over 35% in some cases, suggesting that careful traffic planning is essential to obtain better production in agricultural fields. Prediction models were obtained for all the plant growth characteristics in terms of traffic variables. A relation for yield in terms of soil bulk density was established for a dry season.  相似文献   
40.
Acylation of anisole is a commercially important reaction in the production of various fine chemicals, agrochemicals, pharmaceuticals and fragrances. Conventionally, it is carried out using the catalysts like AlCl3, FeCl3, ZnCl3, HF, which suffer from major drawbacks such as larger consumption, corrosion and safety issues, waste disposal and the material handling. Hence the conventional catalysts are being replaced with solid acid catalysts like H-Beta, H-ZSM5 to overcome the above drawbacks. In this work, liquid phase acylation of anisole has been carried out employing H Beta, H ZSM-5 and HY catalysts and the process standardization at a macrolevel has been done with reference to parameters like temperature, reaction time, molar ratio of reactants, catalyst nature, Si/Al ratio of catalyst and the catalyst quantity. In addition, catalyst stability was investigated.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号