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   13157篇
  免费   2238篇
  国内免费   1804篇
化学   10278篇
晶体学   184篇
力学   762篇
综合类   109篇
数学   1635篇
物理学   4231篇
  2024年   21篇
  2023年   187篇
  2022年   238篇
  2021年   404篇
  2020年   463篇
  2019年   542篇
  2018年   443篇
  2017年   386篇
  2016年   651篇
  2015年   748篇
  2014年   776篇
  2013年   997篇
  2012年   1185篇
  2011年   1161篇
  2010年   901篇
  2009年   871篇
  2008年   944篇
  2007年   768篇
  2006年   682篇
  2005年   644篇
  2004年   551篇
  2003年   505篇
  2002年   616篇
  2001年   481篇
  2000年   310篇
  1999年   265篇
  1998年   226篇
  1997年   158篇
  1996年   140篇
  1995年   134篇
  1994年   113篇
  1993年   82篇
  1992年   74篇
  1991年   75篇
  1990年   50篇
  1989年   38篇
  1988年   26篇
  1987年   28篇
  1986年   16篇
  1985年   19篇
  1984年   19篇
  1983年   16篇
  1981年   15篇
  1980年   30篇
  1978年   23篇
  1977年   47篇
  1976年   19篇
  1975年   20篇
  1974年   16篇
  1943年   10篇
排序方式: 共有10000条查询结果,搜索用时 515 毫秒
1.
Let p ∈ [1, ∞), q ∈ [1, ∞), α∈ R, and s be a non-negative integer. Inspired by the space JNp introduced by John and Nirenberg(1961) and the space B introduced by Bourgain et al.(2015), we introduce a special John-Nirenberg-Campanato space JNcon(p,q,s) over Rn or a given cube of R;with finite side length via congruent subcubes, which are of some amalgam features. The limit space of such spaces as p →∞ is just the Campanato space which coincides with the space BMO(the space of functions with bounded mean oscillations)when α = 0. Moreover, a vanishing subspace of this new space is introduced, and its equivalent characterization is established as well, which is a counterpart of the known characterization for the classical space VMO(the space of functions with vanishing mean oscillations) over Rn or a given cube of Rn with finite side length.Furthermore, some VMO-H1-BMO-type results for this new space are also obtained, which are based on the aforementioned vanishing subspaces and the Hardy-type space defined via congruent cubes in this article. The geometrical properties of both the Euclidean space via its dyadic system and congruent cubes play a key role in the proofs of all these results.  相似文献   
2.
International Journal of Theoretical Physics - A new quantum watermark algorithm is presented by combining maximum pixel difference partitioning with the least significant bit substitution...  相似文献   
3.
4.
We experimentally analyze the heat capacity and thermal expansion of reference solids in a wide temperature range from several Kelvin to melting temperature,and establish a universal double-linear relation between the experimental heat capacity Cp and thermal expansion β,which is different from the previous models.The universal behavior between heat capacity and thermal expansion is important to predict the thermodynamic parameters at constant pressure,and is helpful for understanding the nature of thermal properties in solids.  相似文献   
5.
For an integer s0, a graph G is s-hamiltonian if for any vertex subset S?V(G) with |S|s, G?S is hamiltonian, and G is s-hamiltonian connected if for any vertex subset S?V(G) with |S|s, G?S is hamiltonian connected. Thomassen in 1984 conjectured that every 4-connected line graph is hamiltonian (see Thomassen, 1986), and Ku?zel and Xiong in 2004 conjectured that every 4-connected line graph is hamiltonian connected (see Ryjá?ek and Vrána, 2011). In Broersma and Veldman (1987), Broersma and Veldman raised the characterization problem of s-hamiltonian line graphs. In Lai and Shao (2013), it is conjectured that for s2, a line graph L(G) is s-hamiltonian if and only if L(G) is (s+2)-connected. In this paper we prove the following.(i) For an integer s2, the line graph L(G) of a claw-free graph G is s-hamiltonian if and only if L(G) is (s+2)-connected.(ii) The line graph L(G) of a claw-free graph G is 1-hamiltonian connected if and only if L(G) is 4-connected.  相似文献   
6.
7.
We investigate the cyclic mechanical behavior in uniaxial tension of three different commercial thermoplastic polyurethane elastomers (TPU) often considered as a sustainable replacement for common filled elastomers. All TPU have similar hard segment contents and linear moduli but sensibly different large strain properties as shown by X-ray analysis. Despite these differences, we found a stiffening effect after conditioning in step cyclic loading which greatly differs from the common softening (also referred as Mullins effect) observed in chemically crosslinked filled rubbers. We propose that this self-reinforcement is related to the fragmentation of hard domains, naturally present in TPU, in smaller but more numerous sub-units that may act as new physical crosslinking points. The proposed stiffening mechanism is not dissimilar to the strain-induced crystallization observed in stretched natural rubber, but it presents a persistent nature. In particular, it may cause a local reinforcement where an inhomogeneous strain field is present, as is the case of a crack propagating in cyclic fatigue, providing a potential explanation for the well-known toughness and wear resistance of TPU.  相似文献   
8.
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