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   4460篇
  免费   153篇
  国内免费   21篇
化学   3296篇
晶体学   31篇
力学   62篇
数学   682篇
物理学   563篇
  2022年   23篇
  2021年   48篇
  2020年   65篇
  2019年   65篇
  2018年   39篇
  2017年   28篇
  2016年   119篇
  2015年   108篇
  2014年   107篇
  2013年   193篇
  2012年   187篇
  2011年   209篇
  2010年   159篇
  2009年   131篇
  2008年   210篇
  2007年   216篇
  2006年   197篇
  2005年   191篇
  2004年   196篇
  2003年   146篇
  2002年   144篇
  2001年   94篇
  2000年   76篇
  1999年   81篇
  1998年   82篇
  1997年   76篇
  1996年   79篇
  1995年   68篇
  1994年   88篇
  1993年   68篇
  1992年   63篇
  1991年   46篇
  1990年   32篇
  1989年   72篇
  1988年   67篇
  1987年   79篇
  1986年   47篇
  1985年   54篇
  1984年   63篇
  1983年   52篇
  1982年   63篇
  1981年   54篇
  1980年   59篇
  1979年   49篇
  1978年   29篇
  1977年   47篇
  1976年   29篇
  1975年   39篇
  1974年   23篇
  1973年   29篇
排序方式: 共有4634条查询结果,搜索用时 15 毫秒
1.
2.
3.
The paper mentioned above is a contribution of the authors to Volume 18 (2002) of this journal, see . Recently, J. Domsta pointed out to us that the proof of Theorem 4.2 in that paper contains an error. The purpose of this addendum is to present a correct argument for it.  相似文献   
4.
5.
Periodic sound-pressure time functions with frequency components below 50 Hz were used to measure within their period (a) the temporal course of masking, called a masking-period pattern (MPP), and (b) the temporal course of suppression of delayed evoked otoacoustic emissions, called a suppression-period pattern (SPP). Three different time functions were used: an alternating Gaussian impulse, its first integral, and its second integral. In each case, the course of the SPP is a mirror image of that of the MPP: Small masking corresponds to small suppression, while strong masking coincides with almost total suppression. Since otoacoustic emissions are assumed to have their origin in the inner ear, it can be argued that simultaneous masking, an effect including central processing, is very strongly based on peripheral processes located in the cochlea. Both MPP and SPP are closely related to the second derivative of the sound-pressure time function.  相似文献   
6.
The development of the poly(3‐hydroxybutyrate) (PHB) morphology in the presence of already existent poly(vinylidene fluoride) (PVDF) spherulites was studied by two‐stage solidification with two separate crystallization temperatures. PVDF formed irregular dendrites at lower temperatures and regular, banded spherulites at elevated temperatures. The transition temperature of the spherulitic morphology from dendrites to regular, banded spherulites increased with increasing PVDF content. A remarkable amount of PHB was included in the PVDF dendrites, whereas PHB was rejected into the remaining melt from the banded spherulites. When PVDF crystallized as banded spherulites, PHB could consequently crystallize only around them, if at all. In contrast, PHB crystallized with a common growth front, starting from a defined site in the interfibrillar regions of volume‐filling PVDF dendrites. It formed by itself dendritic spherulites that included a large number of PVDF spherulites. For blends with a PHB content of more than 80 wt %, for which the PVDF dendrites were not volume‐filling, PHB first formed regular spherulites. Their growth started from outside the PVDF dendrites but could later interpenetrate them, and this made their own morphology dendritic. These PHB spherulites melted stepwise because the lamellae inside the PVDF dendrites melted at a lower temperature than those from outside. This reflected the regularity of the two fractions of the lamellae because that of those inside the dendrites of PVDF was controlled by the intraspherulitic order of PVDF, whereas that from outside was only controlled by the temperature and the melt composition. The described morphologies developed without mutual nucleating efficiency of the components. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 873–882, 2003  相似文献   
7.
For arbitrary parabolically semihyperbolic generalized polynomial-like maps f, we prove that on a certain interval, which contains the interval (0, HD(J(f))), the pressure function t ? P(−t log |f|) is real-analytic. Our results generalize the work of Makarov and Smirnov in [3] and [7].  相似文献   
8.
The influence of irradiation and grafting on the crystallinity of three base polymers has been investigated with differential scanning calorimetry. Grafting has the largest effect on the base polymer crystallinity and results in a reduction of the crystallinity. The thermal degradation of the base polymers and grafted films has been investigated with thermogravimetric analysis. The extent of the fluorination of the base polymer, the irradiation method, and the graft level all influence the thermal degradation and its activation energy. It is proposed that the variation of the chain lengths of the grafted polystyrene chains is actually a primary underlying factor responsible for the influence of these various parameters on the degradation process. The first results of a comparative thermal analysis of some fuel‐cell membranes are also presented, and the promise and shortcomings of this method are discussed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2612–2624, 2004  相似文献   
9.
10.
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