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   135232篇
  免费   23447篇
  国内免费   17556篇
化学   95323篇
晶体学   1659篇
力学   8819篇
综合类   1242篇
数学   16710篇
物理学   52482篇
  2024年   131篇
  2023年   2488篇
  2022年   3000篇
  2021年   4198篇
  2020年   5388篇
  2019年   5277篇
  2018年   4597篇
  2017年   4572篇
  2016年   6367篇
  2015年   6483篇
  2014年   7842篇
  2013年   10184篇
  2012年   12511篇
  2011年   12915篇
  2010年   9085篇
  2009年   8851篇
  2008年   9680篇
  2007年   8532篇
  2006年   7866篇
  2005年   6621篇
  2004年   5049篇
  2003年   4126篇
  2002年   3827篇
  2001年   3218篇
  2000年   2792篇
  1999年   2733篇
  1998年   2223篇
  1997年   2115篇
  1996年   2093篇
  1995年   1768篇
  1994年   1559篇
  1993年   1304篇
  1992年   1121篇
  1991年   970篇
  1990年   834篇
  1989年   646篇
  1988年   529篇
  1987年   442篇
  1986年   428篇
  1985年   357篇
  1984年   238篇
  1983年   193篇
  1982年   144篇
  1981年   122篇
  1980年   118篇
  1979年   76篇
  1978年   63篇
  1977年   82篇
  1976年   64篇
  1973年   64篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Journal of Radioanalytical and Nuclear Chemistry - Prostate-specific membrane antigen (PSMA) is a biomarker for prostate cancer, which is commonly used in the development of diagnostic and...  相似文献   
993.
The allergic reaction (AR) of Chinese herbal injection (CHI) has become one of the most noticeable focuses of public health in China. However, it still remains a considerable controversy as to whether low-molecular-weight components in CHI have potential sensitization. In this study, the relationship between AR and low-molecular-weight component profile of Shenmai injection was explored by an interdisciplinary technology integrating real-world evidence and ultra-performance liquid chromatography–quadrupole time-of-flight mass spectroscopy (UPLC–Q-TOF-MS). The AR information of hospitalized patients was obtained by comprehensively analyzing real-world evidence from January 2015 to June 2019 at two Chinese hospitals. The UPLC–Q-TOF-MS was exploited to systematically investigate the low-molecular-weight component profile with 50–1500 m/z mass range, and 3725 MS1 peaks were detected. The optimized partial least squares discriminant analysis model was established to map the influence of low-molecular-weight components on AR. The results of this study showed that high levels of organic acids administered intravenously might be a potential risk factor for inducing AR. By using this method, Shenmai injection with high AR risk could be recognized precisely with 100% accuracy before clinical use.  相似文献   
994.
Peroxynitrite (ONOO) as a major reactive oxygen species plays important roles in cellular signal transduction and homeostatic regulation. Precise detection of ONOO in biological systems is vital for exploring its physiological and pathological function. Among numerous detection methods, fluorescence imaging technology using fluorescent probes offers some advantages, including simple operation, high sensitivity and selectivity, as well as real-time and nondestructive detection. In particular, ratiometric fluorescent probes, in which the built-in calibration of the two emission bands prevents interference from the biological environment, have been extensively employed to monitor the fluctuation of bioactive species. In this review, we will discuss small-molecule ratiometric fluorescent probes for ONOO in live cells or in vivo, which involves chemical structures, response mechanisms, and biological applications. Moreover, the challenges and future prospects of ONOO-responsive ratiometric fluorescent probe are also proposed.  相似文献   
995.
Journal of Inclusion Phenomena and Macrocyclic Chemistry - Poly(ethylene glycol) diamine 1,1’-disubstituted ferrocene was utilized as a size-com-plementary site to synthesize lower coverage...  相似文献   
996.
The CO2 reduction reaction (CRR) represents a promising route for the clean utilization of renewable resources. But mass-transfer limitations seriously hinder the forward step. Enhancing the surface hydrophobicity by using polymers has been proved to be one of the most efficient strategies. However, as macromolecular organics, polymers on the surface hinder the transfer of charge carriers from catalysts to reactants. Herein, we describe an in-situ surface fluorination strategy to enhance the surface hydrophobicity of TiO2 without a barrier layer of organics, thus facilitating the mass transfer of CO2 to catalysts and charge transfer. With less obstruction to charge transfer, a higher CO2, and lower H+ surface concentration, the photocatalytic CRR generation rate of methanol (CH3OH) is greatly enhanced to up to 247.15 μmol g−1 h−1. Furthermore, we investigated the overall defects; enhancing the surface hydrophobicity of catalysts provides a general and reliable method to improve the competitiveness of CRR.  相似文献   
997.
The utility of 2-diphenylphosphoryloxy-1,3-dienes for the construction of substituted six-membered nitrogen heterocycles is presented. These dienes undergo boron trifluoride-promoted aza-Diels–Alder reactions when reacted with imines or related species formed in situ using aldehydes and amine derivatives. The stability of the dienes allows this three-component reaction to be carried out with no special precautions to eliminate water or air. Thirty-one examples of this process are presented. The usefulness of the enol phosphate functional group is highlighted in further reactions after the cycloaddition step to generate functionalized piperidenes or pyridines.  相似文献   
998.
Naphthalene endoperoxides are known as convenient sources of singlet oxygen (O2, 1Δg), which is the major product of endoperoxide cycloreversion reaction. However, their potential as carriers of ground-state molecular oxygen (O2, 3Σg) similar to artificial oxygen carriers remains largely unexplored. This is due to the extreme reactivity and cytotoxic effects of the released singlet oxygen. We now report that a compound with a bimodular design, which incorporates an endoperoxide and an efficient physical quencher of singlet oxygen, 1,4-diazabicyclo[2.2.2]octane (DABCO), produces exclusively ground-state molecular oxygen. This result, coupled with the fact that oxygen release rates from endoperoxides are highly amenable to fine-tuning in a very broad range, and open to targeting by ligand attachment, raises the potential of these compounds far above any comparable chemical, or even biochemical sources. In cell culture experiments, we showed that the addition of the endoperoxide-quencher conjugate can enhance and sustain cell proliferation.  相似文献   
999.
Yu  Shimo  Zhao  Xinfu  Zhang  Jing  Liu  Sijia  Yuan  Zhipeng  Liu  Xiaochan  Liu  Benxue  Yi  Xibin 《Cellulose (London, England)》2022,29(12):6783-6796
Cellulose - High CO2 concentration in atmosphere causes serious environmental issues, and carbon capture and storage technologies have attracted attention as a means to reduce the atmospheric CO2...  相似文献   
1000.
Xiao  Yuanxiang  Shen  Guokang  Zheng  Weishi  Fu  Jiajia  Fu  Feiya  Hu  Xinyue  Jin  Ziyi  Liu  Xiangdong 《Cellulose (London, England)》2022,29(2):1003-1015
Cellulose - We report here a simple and effective method applying a combination of chitosan (Cs) and Cu(II) ion to fabricate antibacterial cotton fabric with a remarkable durability against...  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