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   3574篇
  免费   111篇
  国内免费   19篇
化学   2294篇
晶体学   33篇
力学   42篇
数学   549篇
物理学   786篇
  2023年   21篇
  2022年   43篇
  2021年   57篇
  2020年   69篇
  2019年   84篇
  2018年   64篇
  2017年   62篇
  2016年   153篇
  2015年   122篇
  2014年   153篇
  2013年   289篇
  2012年   200篇
  2011年   231篇
  2010年   152篇
  2009年   139篇
  2008年   192篇
  2007年   163篇
  2006年   168篇
  2005年   100篇
  2004年   103篇
  2003年   74篇
  2002年   89篇
  2001年   48篇
  2000年   41篇
  1999年   39篇
  1998年   49篇
  1997年   36篇
  1996年   40篇
  1995年   34篇
  1994年   23篇
  1993年   35篇
  1992年   37篇
  1991年   28篇
  1990年   24篇
  1989年   20篇
  1988年   19篇
  1987年   30篇
  1986年   22篇
  1985年   26篇
  1984年   24篇
  1982年   18篇
  1981年   24篇
  1980年   24篇
  1979年   21篇
  1978年   21篇
  1977年   18篇
  1976年   21篇
  1975年   27篇
  1974年   23篇
  1969年   22篇
排序方式: 共有3704条查询结果,搜索用时 15 毫秒
51.
We predict ultraslow collapse of “tubular image states” (TIS) on material surfaces. TIS are bound Rydberg-like electronic states formed at large distances (∼30 nm) from the surfaces of suspended circularly-symmetric nanowires, such as metallic C nanotubes. The states are formed in potential wells, resulting from a combination of the TIS-electron attraction to image charges in the nanotube and its centrifugal repulsion, caused by spinning around the tube. We demonstrate that TIS can collapse on the tube surface by passing their angular momentum l to circularly polarized flexural phonons excited in the tube. Our analysis shows that for highly detached TIS with l ? 6 the relaxation lifetimes are of the order of 10 ns-1 μs, while for l < 6 these lifetimes are reduced by several orders of magnitude.  相似文献   
52.
Autler-Townes splitting (ATS) and electromagnetically induced transparency (EIT) both yield transparency in an absorption profile, but only EIT yields strong transparency for a weak pump field due to Fano interference. Empirically discriminating EIT from ATS is important but so far has been subjective. We introduce an objective method, based on Akaike's information criterion, to test ATS vs EIT from experimental data for three-level atomic systems and determine which pertains. We apply our method to a recently reported induced-transparency experiment in superconducting-circuit quantum electrodynamics.  相似文献   
53.
The 16 O+ 15 N reaction products have been studied by the γ-ray detection method in the CM energy range 15.5 to 36.1 MeV and by the kinematical coincidence method at energies ranging from E CM =20.6 to 33.5MeV. The γ-ray yield excitation function of the 16O 3? inelastic channel shows the existence of resonant structures. Two structures with ~ 1.6 MeV width are observed in the large angle elastic scattering excitation function, they are correlated with the resonances seen in the inelastic channel. Angular momentum assignments were made from the elastic backward angular distributions.  相似文献   
54.
The results of NMR/ON measurements on56'57'60Co isotopes in iron are presented. To avoid the uncertainties caused by local demagnetizing field inhomogenities the measurements on two cobalt isotopes in one sample have been carried out. The values of nuclear-factor ratios 57/ 60 = 1.805 (20), 60/ 56 = 0.761 (20), 56/ 57 = 0.726 (20) and hyperfine anomalies5660 = -0.036 (10),60 57 = 0.017 (10) and5756 = 0.018 (10) have been calculated from the experimental results.  相似文献   
55.
56.
Journal of Radioanalytical and Nuclear Chemistry - The extraction of trivalent europium and americium in the system water—HNO3—3-nitro-α,α,α-trifluorotoluene...  相似文献   
57.
The structural-phase state of the contact zone and the factors that influence on the strength of diamond retention in the diamond carbide composites were determined. Composites were obtained by the new hybrid technology that eliminates the reheating of the metalized coating. The elaborated technology combines the thermal diffusion metallization of a diamond and the sintering by the scheme of self-dosed impregnation in a one-stage technological cycle. By the methods of electron microscopy, X-ray diffraction analysis, and Raman spectroscopy the structural and phase characteristics of the interphase boundary were investigated. The improvement of chemical and mechanical adhesion between the diamond and carbide matrix was obtained. It was shown that the specific productivity of the samples with a metalized diamond component is 39% higher than those without metallization.  相似文献   
58.
The 1,4-palladium shift strategy allows the functionalization of remote C−H bonds that are difficult to reach directly. Reported here is a domino reaction proceeding by C(sp3)−H activation, 1,4-palladium shift, and amino- or alkoxycarbonylation, which generates a variety of amides and esters bearing a quaternary β-carbon atom. Mechanistic studies showed that the aminocarbonylation of the σ-alkylpalladium intermediate arising from the palladium shift is fast using PPh3 as the ligand, and leads to the amide rather than the previously reported indanone product.  相似文献   
59.
Carbon monoxide (CO) is an endogenous signaling molecule that controls a number of physiological processes. To circumvent the inherent toxicity of CO, light-activated CO-releasing molecules (photoCORMs) have emerged as an alternative for its administration. However, their wider application requires photoactivation using biologically benign visible and near-infrared (NIR) light. In this work, a strategy to access such photoCORMs by fusing two CO-releasing flavonol moieties with a NIR-absorbing cyanine dye is presented. These hybrids liberate two molecules of CO in high chemical yields upon activation with NIR light up to 820 nm and exhibit excellent uncaging cross-sections, which surpass the state-of-the-art by two orders of magnitude. Furthermore, the biocompatibility and applicability of the system in vitro and in vivo are demonstrated, and a mechanism of CO release is proposed. It is hoped that this strategy will stimulate the discovery of new classes of photoCORMs and accelerate the translation of CO-based phototherapy into practice.  相似文献   
60.
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