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   19513篇
  免费   3398篇
  国内免费   2405篇
化学   14473篇
晶体学   234篇
力学   1061篇
综合类   132篇
数学   1953篇
物理学   7463篇
  2024年   16篇
  2023年   373篇
  2022年   400篇
  2021年   575篇
  2020年   820篇
  2019年   767篇
  2018年   697篇
  2017年   593篇
  2016年   948篇
  2015年   911篇
  2014年   1124篇
  2013年   1497篇
  2012年   1764篇
  2011年   1796篇
  2010年   1259篇
  2009年   1241篇
  2008年   1357篇
  2007年   1254篇
  2006年   1130篇
  2005年   1001篇
  2004年   802篇
  2003年   642篇
  2002年   664篇
  2001年   489篇
  2000年   365篇
  1999年   397篇
  1998年   327篇
  1997年   304篇
  1996年   284篇
  1995年   228篇
  1994年   217篇
  1993年   163篇
  1992年   158篇
  1991年   158篇
  1990年   103篇
  1989年   106篇
  1988年   75篇
  1987年   64篇
  1986年   48篇
  1985年   48篇
  1984年   29篇
  1983年   24篇
  1982年   18篇
  1981年   24篇
  1980年   11篇
  1975年   6篇
  1974年   6篇
  1973年   5篇
  1957年   4篇
  1936年   5篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
In this study, the synthesis of TaN nanosheets and their application in theranostic agents is reported. After coating polyethylene glycol (PEG) on the TaN nanosheets, the as-synthesized PEG-modified TaN nanosheets (TaN-PEG) show good stability and biocompatibility. Because of their high absorbance in the near-IR region, TaN-PEG can be utilized as photoacoustic imaging contrast agents for tumor imaging. Moreover, TaN-PEG has significant photothermal conversion performance, exhibiting effective laser-induced tumor ablation capability. The TaN-PEG possessing excellent photoacoustic contrast effect and photothermal properties thus have great promise in theranostic applications, especially imaging-guided cancer treatment.  相似文献   
2.
International Journal of Theoretical Physics - In this paper, we investigate Einstein-Podolsky-Rosen steering, Bell non-locality, first-order coherence and concurrence in the spin- $\frac {1}{2}$...  相似文献   
3.
Jiang  H.  Lei  Z.  Bai  R.  Liu  J.  Guo  Z.  Dong  H.  Feng  W. 《Experimental Mechanics》2021,61(5):867-883
Experimental Mechanics - Ratcheting is an important mechanical behavior of metals and alloys, which is caused by the repeated accumulations of tensile and compressive strain in circle load....  相似文献   
4.
Song  Zi-Long  Zhu  Yun  Liu  Jing-Rui  Guo  Shu-Ke  Gu  Yu-Cheng  Han  Xinya  Dong  Hong-Qiang  Sun  Qi  Zhang  Wei-Hua  Zhang  Ming-Zhi 《Molecular diversity》2021,25(1):205-221
Molecular Diversity - Based on the strategy of diversity-oriented synthesis and the structures of natural product pimprinine and streptochlorin, two series of novel pimprinine derivatives...  相似文献   
5.
Journal of Mathematical Chemistry - The analytical solutions of an asymmetric double well potential $$V(x)=a\, x^2-b\, x^3+c\, x^4$$ are found to be a triconfluent Heun function $$H_{T}(\alpha ,...  相似文献   
6.
7.
A capillary electrophoresis-acid barrage stacking online enrichment method has been established to detect the four isoflavones which are Daidzein, Genistein, Formononetin, and Biochanin A. The proposed method was optimized using a single factor alternative method, and the optimal conditions obtained from the optimization were: the BGE was 25 mM borax and 2 mM β-cyclodextrin, the applied separation voltage was 20 kV, and the detection wavelength was 260 nm. The time ratio of the injection of sample and the injection of acid was 150 s:20 s, and the acid used was 250 mM acetic acid. The sample solvent used was 60% v/v acetonitrile. The established method had the enrichment factor of these four isoflavones at 24.5, 32.0, 29.2, and 33.7, respectively, LOD and LOQ are as low as nanograms per milliliter. Finally, the CE-acid barrage stacking method was successfully applied to the determination of four isoflavones in rat plasma and red clover extract, verifying the applicability and feasibility of the method.  相似文献   
8.
Pd-based catalysts are the most widely used for CO oxidation because of their outstanding catalytic activity and thermal stability. However, fundamental understanding of the detailed catalytic processes occurring on Pd-based catalysts under realistic conditions is still lacking. In this study, we investigated CO oxidation on metallic Pd clusters supported on Al2O3 and SiO2. High-angle annular dark-field scanning transmission electron microscopy revealed the formation of similar-sized Pd clusters on Al2O3 and SiO2. In contrast, CO chemisorption analysis indicated a gradual change in the dispersion of Pd (from 0.79 to 0.2) on Pd/Al2O3 and a marginal change in the dispersion (from 0.4 to 0.24) on Pd/SiO2 as the Pd loading increased from 0.27 to 5.5 wt %; these changes were attributed to differences in the metal-support interactions. Diffuse reflectance infrared Fourier-transform spectroscopy revealed that fewer a-top CO species were present in Pd supported on Al2O3 than those in Pd supported on SiO2, which is related to the morphological differences in the metallic Pd clusters on these two supports. Despite the different dispersion profiles and surface characteristics of Pd, O2 titration demonstrated that linearly bound CO (with an infrared signal at 2090 cm−1) reacted first with oxygen in the case of CO-saturated Pd on Al2O3 and SiO2, which suggests that a-top CO on the terrace site plays an important role in CO oxidation. The experimental observations were corroborated by periodic density functional calculations, which confirmed that CO oxidation on the (111) terrace sites is most plausible, both kinetically and thermodynamically, compared to that on the edge or corner sites. This study will deepen the fundamental understanding of the effect of Pd clusters on CO oxidation under reaction conditions.  相似文献   
9.

In this paper, we study a category of restricted modules for the Ovsienko-Roger algebra, which is an extension of the Virasoro algebra of its tensor density module of degree one. We construct and characterize simple modules in this category and give natural free field realizations of certain restricted modules using the Weyl vertex algebra.

  相似文献   
10.
Refractory wounds have always been an important issue to healthcare systems, whose healing process is always delayed by multiple factors, including bacterial infections, chronic inflammation, and excessive exudates, etc. Employing multifunctional wound dressings is recognized as an effective strategy to deal with refractory wounds, which has yielded promising outcomes in recent years. Among these advanced wound dressings, fibrous dressings have gained growing attention due to their unique merits. Such wound dressings have demonstrated great potential in delivering theranostic agents, such as antibacterial agents, anti-inflammatory drugs, growth factors, and diagnostic probes, etc., for the purposes of accelerating wound healing. This paper reviews the development of multifunctional fibrous dressings and their applications in treating refractory wounds. The construction approaches of novel fibrous dressing with capabilities of antibacterial, anti-inflammation, exudate management and diagnosis were also introduced. Furthermore, the existing problems and challenges are also discussed briefly.  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