全文获取类型
收费全文 | 6097篇 |
免费 | 553篇 |
国内免费 | 418篇 |
专业分类
化学 | 1100篇 |
晶体学 | 61篇 |
力学 | 3546篇 |
综合类 | 80篇 |
数学 | 885篇 |
物理学 | 1396篇 |
出版年
2024年 | 6篇 |
2023年 | 35篇 |
2022年 | 126篇 |
2021年 | 243篇 |
2020年 | 169篇 |
2019年 | 121篇 |
2018年 | 129篇 |
2017年 | 171篇 |
2016年 | 230篇 |
2015年 | 183篇 |
2014年 | 233篇 |
2013年 | 391篇 |
2012年 | 226篇 |
2011年 | 296篇 |
2010年 | 238篇 |
2009年 | 290篇 |
2008年 | 306篇 |
2007年 | 363篇 |
2006年 | 358篇 |
2005年 | 302篇 |
2004年 | 311篇 |
2003年 | 260篇 |
2002年 | 203篇 |
2001年 | 221篇 |
2000年 | 227篇 |
1999年 | 186篇 |
1998年 | 156篇 |
1997年 | 148篇 |
1996年 | 137篇 |
1995年 | 119篇 |
1994年 | 94篇 |
1993年 | 92篇 |
1992年 | 89篇 |
1991年 | 77篇 |
1990年 | 55篇 |
1989年 | 42篇 |
1988年 | 46篇 |
1987年 | 43篇 |
1986年 | 31篇 |
1985年 | 24篇 |
1984年 | 19篇 |
1983年 | 11篇 |
1982年 | 22篇 |
1981年 | 20篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1977年 | 2篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1957年 | 3篇 |
排序方式: 共有7068条查询结果,搜索用时 281 毫秒
21.
侯旻 《新疆大学学报(理工版)》1991,(1)
本文比较了循环图类{c_p(n_1,…,n_p)}和{c-p(n_1…,n_p,p/α)}的直径下界。对于p和α满足一定条件的循环图类{c_p(n_1,n_2,p/α)},本文给出了达到或几乎达到此图类直径下界的一类几乎最优循环图{c_p(m,m+1,p/α)}。 相似文献
22.
23.
We discuss determination of jumps for functions with generalized bounded variation. The questions are motivated by A. Gelb
and E. Tadmor [1], F. Móricz [5] and [6] and Q. L. Shi and X. L. Shi [7]. Corollary 1 improves the results proved in B. I.
Golubov [2] and G. Kvernadze [3].
Supported by NSFC 10671062. 相似文献
24.
提出了一种基于微悬臂梁传感技术研究大分子折叠/构象转变的新方法.通过分子自组装的方法将热敏性的聚N-异丙基丙烯酰胺(PNIPAM)分子链修饰到微悬臂梁的单侧表面,用光杠杆技术检测温度在20—40℃之间变化时由于微悬臂梁上的PNIPAM分子在水中的构象转变所引起的微悬臂梁变形.实验结果显示:在升温过程中,微悬臂梁的表面应力发生了变化并且导致微悬臂梁产生了弯曲变形,这个过程对应着微悬臂梁上的PNIPAM分子从无规线团构象到塌缩小球构象的构象转变.在降温过程中,微悬臂梁发生了反方向的弯曲变形,这对应着PNIPA
关键词:
构象转变
聚N-异丙基丙烯酰胺分子链
表面应力
微悬臂梁 相似文献
25.
26.
The stress tensor of a massless scalar field satisfying a mixed boundary condition in a (1 + 1)-dimensional Reissner- Nordstrom black hole background is calculated by using Wald's axiom. We find that Dirichlet stress tensor and Neumann stress tensor can be deduced by changing the coefficients of the stress tensor calculated under a mixed boundary condition. The stress tensors satisfying Dirichlet and Neumann boundary conditions are discussed. In addition, we also find that the stress tensor in conformal flat spacetime background differs from that in flat spacetime only by a constant. 相似文献
27.
28.
标的股价服从混合过程的期权定价公式及有限元算法 总被引:2,自引:0,他引:2
本文将马尔科夫跳跃过程叠加于 Ito过程 ,形成混合过程 ,并用该过程来刻画股价走势情况。而后在标的股价服从混合过程的基础上 ,推导出了欧式看涨期权的定价公式 ,并对美式看跌期权定价给出了有限元算法。 相似文献
29.
For the methylsilsesquioxane film whose optical birefringence is almost zero, it was recently reported that its vertical thermal expansion coefficient (CTE) was approximately one order of magnitude larger than the lateral CTE. Though the birefringence is not an absolute predictor of anisotropic behavior, the discrepancy in both the CTEs was so remarkable that it was essential to investigate whether the anisotropy was intrinsic property or not. If the effect of Poisson's ratio is considered in the calculation of the vertical CTE and when elastic modulus measured by surface acoustic wave spectroscopy is used in the assessment of the lateral CTE, both the CTEs are coincident with each other. Therefore, it can be concluded that the discrepancy in the CTEs can be attributed to a higher in‐plane polymer chain orientation but it can also arise from the misleadingly assumed modulus and Poisson's ratio. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3109–3120, 2006 相似文献
30.
It is thought that the extensive industrial use of arsenic, gallium and indium, which have applications as the materials for III–V semiconductors, will increase human exposure to these compounds in the near future. We have undertaken the development of new biological indicators for assessing exposure to these elements. Element-specific alterations in protein synthesis patterns were expected to occur following exposure to arsenic compounds. We examined alterations in protein synthesis in primary cultures of rat kidney proximal tubule epithelial cells by sodium arsenite, gallium chloride and indium chloride, utilizing two-dimensional gel electrophoresis. After incubation with the chemicals for 20 h, newly synthesized proteins were labeled with [35S]methionine. A protein with a molecular weight (Mr) of 30 000 was markedly induced on exposure to 10 μM arsenite or 300 μM gallium chloride, and synthesis of proteins with Mr values of 85 000, 71 000, 65 000, 51 000, 38 000 and 28 000 were also increased by exposure to arsenite and gallium chloride. No significant changes were observed upon exposure to indium. Some of these increased proteins could be heat-shock proteins. 相似文献