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   11916篇
  免费   2043篇
  国内免费   2252篇
化学   9147篇
晶体学   152篇
力学   730篇
综合类   183篇
数学   1498篇
物理学   4501篇
  2024年   10篇
  2023年   271篇
  2022年   349篇
  2021年   417篇
  2020年   584篇
  2019年   542篇
  2018年   436篇
  2017年   448篇
  2016年   647篇
  2015年   629篇
  2014年   685篇
  2013年   956篇
  2012年   955篇
  2011年   1034篇
  2010年   775篇
  2009年   722篇
  2008年   828篇
  2007年   697篇
  2006年   638篇
  2005年   614篇
  2004年   491篇
  2003年   393篇
  2002年   439篇
  2001年   338篇
  2000年   303篇
  1999年   276篇
  1998年   220篇
  1997年   169篇
  1996年   204篇
  1995年   154篇
  1994年   179篇
  1993年   144篇
  1992年   101篇
  1991年   123篇
  1990年   115篇
  1989年   56篇
  1988年   45篇
  1987年   42篇
  1986年   52篇
  1985年   49篇
  1984年   17篇
  1983年   23篇
  1982年   13篇
  1981年   11篇
  1980年   6篇
  1979年   3篇
  1971年   1篇
  1957年   3篇
  1936年   4篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
1.
基于一款市场较为畅销的注塑机, 设计出一种能精确控制注射速度的模糊神经元PID控制器. 首先, 设计出具有自学能力的神经元PID控制器, 利用模糊算法对其进行优化; 其次, 在原有注射速度线性数学模型的基础上, 构建注塑机注射速度的非线性模型; 最后, 利用MATLAB在所建数学模型的基础上对模糊神经元PID控制器进行仿真实验. 实验结果表明, 所设计控制器具有响应迅速、无超调量、控制精度高、控制稳定等优点.  相似文献   
2.
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   
3.
Near-infrared(NIR) fluorescent materials with high photoluminescent quantum yields(PLQYs) have wide application prospects. Therefore, we design and synthesize a D-A type NIR organic molecule, TPATHCNE, in which triphenylamine and thiophene are utilized as the donors and fumaronitrile is applied as the acceptor. We systematically investigate its molecular structure and photophysical property. TPATHCNE shows high Tgof 110℃ and Td of 385℃ and displays an aggregation-induced emission(AIE) property. A narrow optical bandgap of 1.65 eV is obtained. The non-doped film of TPATHCNE exhibits a high PLQY of 40.3% with an emission peak at 732 nm, which is among the best values of NIR emitters. When TPATHCNE is applied in organic light-emitting diode(OLED), the electroluminescent peak is located at 716 nm with a maximum external quantum efficiency of 0.83%. With the potential in cell imaging, the polystyrene maleic anhydride(PMSA) modified TPATHCNE nanoparticles(NPs) emit strong fluorescence when labeling HeLa cancer cells, suggesting that TPATHCNE can be used as a fluorescent carrier for specific staining or drug delivery for cellular imaging. TPATHCNE NPs fabricated by bovine serum protein(BSA) are cultivated with mononuclear yeast cells, and the intense intracellular red fluorescence indicates that it can be adopted as a specific stain for imaging.  相似文献   
4.
Guo  Jiayun  Ma  Dongge  Sun  Fulin  Zhuang  Guilin  Wang  Qi  Al-Enizi  Abdullah M.  Nafady  Ayman  Ma  Shengqian 《中国科学:化学(英文版)》2022,65(9):1704-1709
Science China Chemistry - The heterojunction constructed of covalent organic frameworks (COFs) with adjustable structure and other photocatalysts has great potential in the field of photocatalysis....  相似文献   
5.
3,4-Difluorobenzyl(1-ethyl-5-(4-((4-hydroxypiperidin-1-yl)-methyl)thiazol-2-yl)-1H-indol-3-yl)carbamate (NAI59), a small molecule with outstanding therapeutic effectiveness to anti-pulmonary fibrosis, was developed as an autotaxin inhibitor candidate compound. To evaluate the pharmacokinetics and plasma protein binding of NAI59, a UPLC–MS/MS method was developed to quantify NAI59 in plasma and phosphate-buffered saline. The calibration curve linearity ranged from 9.95 to 1990.00 ng/mL in plasma. The accuracy was −6.8 to 5.9%, and the intra- and inter-day precision was within 15%. The matrix effect and recovery, as well as dilution integrity, were within the criteria. The chromatographic and mass spectrometric conditions were also feasible to determine phosphate-buffered saline samples, and it has been proved that this method exhibits good precision and accuracy in the range of 9.95–497.50 ng/mL in phosphate-buffered saline. This study is the first to determine the pharmacokinetics, absolute bioavailability, and plasma protein binding of NAI59 in rats using this established method. Therefore, the pharmacokinetic profiles of NAI59 showed a dose-dependent relationship after oral administration, and the absolute bioavailability in rats was 6.3%. In addition, the results of protein binding showed that the combining capacity of NAI59 with plasma protein attained 90% and increased with the increase in drug concentration.  相似文献   
6.
Research on Chemical Intermediates - Owing to the simultaneous utilization of photogenerated electrons and holes, coupling light-driven hydrogen (H2) evolution reaction (HER) and biomass-derived...  相似文献   
7.
8.
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   
9.
Journal of Applied Mechanics and Technical Physics - A self-equilibrated stress field for an incompressible sphere is constructed based on a non-Euclidean continuum model. The...  相似文献   
10.
随着供热计量系统的普及,系统可以根据负荷的变化进行调整,管网的阻力系数随即发生变化。对变动阻力系数进行优化辨识是了解供热管网实时运行状况的有效手段。提出一种基于流量监测数据的供热管网变动阻力系数优化辨识方法,并利用遗传算法进行求解。对洛阳市某小区供暖季管网实际运行数据进行验证,辨识结果的相对误差在5%以内。结果表明:该方法可以在只有流量观测数据时得到精度较高的供热管网变动阻力系数,为供热系统的运行调节提供指导。  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