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   944篇
  免费   20篇
化学   352篇
晶体学   5篇
力学   21篇
数学   453篇
物理学   133篇
  2023年   8篇
  2021年   8篇
  2020年   19篇
  2019年   17篇
  2018年   29篇
  2017年   43篇
  2016年   39篇
  2015年   41篇
  2014年   60篇
  2013年   119篇
  2012年   40篇
  2011年   47篇
  2010年   47篇
  2009年   33篇
  2008年   47篇
  2007年   36篇
  2006年   27篇
  2005年   18篇
  2004年   21篇
  2003年   26篇
  2002年   21篇
  2001年   14篇
  2000年   12篇
  1999年   19篇
  1998年   11篇
  1997年   5篇
  1995年   3篇
  1994年   6篇
  1993年   3篇
  1991年   4篇
  1990年   4篇
  1988年   7篇
  1987年   4篇
  1986年   3篇
  1985年   8篇
  1984年   5篇
  1983年   6篇
  1982年   5篇
  1981年   6篇
  1979年   7篇
  1978年   8篇
  1977年   9篇
  1976年   8篇
  1975年   5篇
  1974年   10篇
  1973年   7篇
  1972年   3篇
  1969年   5篇
  1943年   3篇
  1939年   3篇
排序方式: 共有964条查询结果,搜索用时 703 毫秒
161.
162.
Eigenvalue problems involving the p-Laplacian and rapidly growing operators in divergence form are studied in an Orlicz–Sobolev setting. An asymptotic analysis of these problems leads to a full characterization of the spectrum of an exponential type perturbation of the Laplace operator.  相似文献   
163.
The region situated between the mountain area and the lowlands in NE Romania (East-Central Europe) is experiencing increased competition for water resources triggered by a growing population, intensification of agriculture, and industrial development. To better understand hydrological cycling processes in the region, a study was conducted using stable isotopes of water and atmospheric trajectory data to characterize regional precipitation and vapour sources derived from the Atlantic Ocean, Mediterranean and Black Seas, as well as recycled continental moisture, and to assess and partition these contributions to recharge of surface and groundwater. Atmospheric moisture in the lowlands is found to be predominantly delivered along easterly trajectories, while mountainous areas appear to be dominated by North Atlantic Ocean sources, with moisture transported along mid-latitude, westerly storm tracks. Large-scale circulation patterns affect moisture delivery, the North Atlantic Oscillation being particularly influential in winter and the East Atlantic pattern in summer. Winter precipitation is the main contributor to river discharge and aquifer recharge. As winter precipitation amounts are projected to decrease over the next decades, and water abstraction is expected to steadily increase, a general reduction in water availability is projected for the region.  相似文献   
164.
In this Note, we study the existence of low- or high-energy solutions for a class of elliptic problems containing a nonlinear term that oscillates either near the origin or at infinity. We point out the competition effect between the oscillatory nonlinearity, a polynomial growth term, and the values of a real parameter. The proofs combine related variational methods.  相似文献   
165.
166.
The nature of the complexing agents used in the bioscouring process of cotton fabrics aiming to eliminate the non-cellulosic compounds (pectin, waxes, etc.) and to improve the hydrophilic and wetting properties influences the thermal behaviour and the FT-IR spectra of the textile materials. In this paper, we study the influence of the experimental conditions and complexing agent nature (sodium citrate or disodium EDTA salt) on the pectin elimination in bioscouring treatment of cotton fabric by FT-IR and TG/DTG/DTA analysis. The changes from FT-IR spectra of the specific bands (absorbance intensity at 2916, 2852, 1732 and 1640/1642 cm?1) were evaluated. The thermal behaviour of the investigated samples’ fabric by using TG/DTG/DTA analysis was studied at 30–600 °C temperature range, in air atmosphere. All samples showed three mass-loss steps due to the elimination of humidity, decomposition of the non-cellulosic and cellulosic components (main degradation stage of the samples) and thermo-oxidative decomposition of the formed degradation products. The Tonset values corresponding to the main decomposition step, the mass-loss values (%Δm) and the % residual mass (at 600 °C) were influenced by the complexing agent nature as well as the concentration and the action time of the commercial enzyme product. In addition, the calcium content of some samples treated with and without ultrasound was determined using atomic absorption spectroscopy method (AAS) in order to correlate the results with TG/DTG/DTA analysis. The obtained results have shown that the synergistic action of experimental conditions (enzyme concentration, pH, enzyme product action time, ultrasound) and the presence of sodium citrate as a biodegradable complexing agent led to the elimination of a higher amount of pectin from the cotton samples than that eliminated when using EDTA.  相似文献   
167.
Journal of Thermal Analysis and Calorimetry - The food-colouring dye tartrazine is a significant additive and in the same time a biologically active material. Thermal behaviour of trisodium...  相似文献   
168.
The catalytic methanolysis of the chemical warfare nerve agents soman, sarin, and VX was investigated by using Cu or Zn complexes. Although VX withstood decontamination, the decomposition yield being around 96%, the soman and sarin deposited on different surfaces were almost fully destroyed under ambient conditions. The catalytic tests performed on a wide range of contaminated surfaces confirm the activity of the investigated catalytic systems, these complexes being suitable, from an economical point of view, for use in the formulation of a possible decomposition kit with military or civilian applicability.  相似文献   
169.
We extend the ordinary concept of theory morphism in institutions to extra theory morphisms. Extra theory morphisms map theories belonging to different institutions across institution morphisms. We investigate the basic mathematical properties of extra theory morphisms supporting the semantics of logical multi-paradigm languages, especially structuring specifications (module systems) á la OBJ-Clear. They include model reducts, free constructions (liberality), co-limits, model amalgamation (exactness), and inclusion systems.We outline a general logical semantics for languages whose semantics satisfy certain logical principles by extending the institutional semantics developed within the Clear-OBJ tradition. Finally, in the Appendix, we briefly illustrate this with the concrete example of CafeOBJ.  相似文献   
170.
We show that the two-sided two-cosided Hopf modules are in some case generalized Hopf modules in the sense of Doi. Then the equivalence between two-sided two-cosided Hopf modules and Yetter—Drinfeld modules, proved in [8], becomes an equivalence between categories of Doi—Hopf modules. This equivalence induces equivalences between the underlying categories of (co)modules. We study the relation between this equivalence and the one given by the induced functor.  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