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   328184篇
  免费   20405篇
  国内免费   11341篇
化学   194450篇
晶体学   4456篇
力学   16135篇
综合类   596篇
数学   37096篇
物理学   107197篇
  2022年   4006篇
  2021年   5145篇
  2020年   5900篇
  2019年   5943篇
  2018年   5939篇
  2017年   5724篇
  2016年   8708篇
  2015年   7159篇
  2014年   9349篇
  2013年   16595篇
  2012年   16958篇
  2011年   19264篇
  2010年   13180篇
  2009年   12776篇
  2008年   15471篇
  2007年   15094篇
  2006年   14088篇
  2005年   12445篇
  2004年   10418篇
  2003年   8860篇
  2002年   8554篇
  2001年   9020篇
  2000年   7078篇
  1999年   5959篇
  1998年   5024篇
  1997年   4882篇
  1996年   5041篇
  1995年   4231篇
  1994年   4294篇
  1993年   3837篇
  1992年   3983篇
  1991年   3960篇
  1990年   3568篇
  1989年   3242篇
  1988年   3079篇
  1987年   2929篇
  1986年   2944篇
  1985年   3665篇
  1984年   3633篇
  1983年   2967篇
  1982年   3196篇
  1981年   2935篇
  1980年   2694篇
  1979年   2840篇
  1978年   3036篇
  1977年   3075篇
  1976年   3112篇
  1975年   2848篇
  1974年   2964篇
  1973年   2997篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Sun  Qinqin  Wang  Xiuye  Yang  Guolai  Chen  Ye-Hwa  Ma  Fai 《Nonlinear dynamics》2022,109(3):1629-1650
Nonlinear Dynamics - This paper proposes an optimal parameter design of control scheme for mechanical systems by adopting the Stackelberg game theory. The goal of the control is to drive the...  相似文献   
32.
Wang  Xigui  Ruan  Jiafu  Wang  Yongmei  Ji  Shue  An  Siyuan 《Meccanica》2021,56(2):303-316
Meccanica - In gear pair actual alternating meshing process, the comprehensive errors of the transmission system and the thermal elastic deformation of the teeth body cause the gears in the meshing...  相似文献   
33.
Annals of the Institute of Statistical Mathematics - In this paper, a model averaging approach is developed for the linear regression models with response missing at random. It is shown that the...  相似文献   
34.
Ukrainian Mathematical Journal - We establish new criteria of compatibility for a linear system of equations (equivalent to the Kronecker–Capelli theorem) or inequalities (equivalent to the...  相似文献   
35.
Chen  R. J.  Chen  W.  Kong  F. L. 《Analysis Mathematica》2022,48(1):19-28

Restricted testing conditions were considered recently. For the maximal operator, Hytönen, Li and Sawyer [8] first obtained parental testing condition. Later, they [9] showed that it suffices to restrict testing to doubling cubes. Chen and Lacey [3] gave a similar restricted testing condition. In our paper, we discuss a version of the latter in the multilinear setting.

  相似文献   
36.
Physics of the Solid State - The external factors which influence the ferromagnetic resonance (FMR) line width in bilayer (ferromagnet/antiferromagnet) exchange-biased systems are studied. The...  相似文献   
37.
Acridone as a new kind of visible light photocatalyst has been developed to catalyze metal free atom transfer radical polymerization (ATRP). The photocatalyst possess low excited state potential as can undergo an oxidative quenching pathway to initiate ATRP of vinyl monomers. Kinetic study and light on/off reaction demonstrate the “living”/controlled nature of the polymerization by light. Block copolymers can be achieved by using PMMA as macroinitiator to reinitiate polymerization of other vinyl monomers, which shows highly preserved Br chain-end functionality in the synthesized polymers. Moreover, the polymerization can be conducted under air atmosphere as most photocatalysts need anaerobic condition, which may give inspiration of further application of this kind of photocatalyst.  相似文献   
38.
A temperature control unit was implemented to vary the temperature of samples studied on a commercial Mobile Universal Surface Explorer nuclear magnetic resonance (MOUSE-NMR) apparatus. The device was miniaturized to fit the maximum MOUSE sampling depth (25 mm). It was constituted by a sample holder sandwiched between two heat exchangers placed below and above the sample. Air was chosen as the fluid to control the temperature at the bottom of the sample, at the interface between the NMR probe and the sample holder, in order to gain space. The upper surface of the sample was regulated by the circulation of water inside a second heat exchanger placed above the sample holder. The feasibility of using such a device was demonstrated first on pure water and then on several samples of bread dough with different water contents. For this, T1 relaxation times were measured at various temperatures and depths and were then compared with those acquired with a conventional compact closed-magnet spectrometer. Discussion of results was based on biochemical transformations in bread dough (starch gelatinization and gluten heat denaturation). It was demonstrated that, within a certain water level range, and because of the low magnetic field strength of the MOUSE, a linear relationship could be established between T1 relaxation times and the local temperature in the dough sample.  相似文献   
39.
Crystallography Reports - The orientation of grains and the special boundaries formed by them in multicrystalline silicon has been studied by electron backscattered diffraction. It is found that...  相似文献   
40.
The chiral phase transition and equation of state are studied within a novel self-consistent mean-field approximation of the two-flavor Nambu-Jona-Lasinio model. In this newly developed model, modifications to the chemical μ and chiral chemical \begin{document}$\mu_5$\end{document} potentials are naturally included by introducing vector and axial-vector channels from Fierz-transformed Lagrangian to the standard Lagrangian. In the proper-time scheme, the chiral phase transition is a crossover in the \begin{document}$T-\mu$\end{document} plane. However, when \begin{document}$\mu_5$\end{document} is incorporated, our study demonstrates that a first order phase transition may emerge. Furthermore, the chiral imbalance will soften the equation of state of quark matter. The mass-radius relationship and tidal deformability of quark stars are calculated. The maximum mass and radius decrease as \begin{document}$\mu_5$\end{document} increases. Our study also indicates that the vector and axial-vector channels exhibit an opposite influence on the equation of state.  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