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   256490篇
  免费   47696篇
  国内免费   36169篇
化学   118279篇
晶体学   2163篇
力学   11982篇
综合类   596篇
数学   22065篇
物理学   87148篇
综合类   98122篇
  2024年   972篇
  2023年   3619篇
  2022年   4774篇
  2021年   5732篇
  2020年   6670篇
  2019年   9055篇
  2018年   8641篇
  2017年   9134篇
  2016年   11466篇
  2015年   11607篇
  2014年   13258篇
  2013年   16025篇
  2012年   17321篇
  2011年   19053篇
  2010年   19245篇
  2009年   18792篇
  2008年   12938篇
  2007年   11903篇
  2006年   10380篇
  2005年   9992篇
  2004年   9540篇
  2003年   7579篇
  2002年   6852篇
  2001年   6624篇
  2000年   5631篇
  1999年   7467篇
  1998年   6657篇
  1997年   6437篇
  1996年   6619篇
  1995年   6340篇
  1994年   6270篇
  1993年   5800篇
  1992年   5046篇
  1991年   4505篇
  1990年   3758篇
  1989年   3519篇
  1988年   3289篇
  1987年   2147篇
  1986年   1941篇
  1985年   1342篇
  1984年   1275篇
  1983年   536篇
  1982年   1032篇
  1981年   845篇
  1980年   848篇
  1979年   574篇
  1978年   568篇
  1977年   668篇
  1976年   1089篇
  1972年   555篇
排序方式: 共有10000条查询结果,搜索用时 890 毫秒
101.
Journal of Thermal Analysis and Calorimetry - The fire behavior of one flame-retardant PVC cable used as building wire is investigated in this work. Bench scale tests were performed using a cone...  相似文献   
102.
近年来,我国农民工群体正处在代际更替的阶段,新生代农民工有其独特的消费观念、消费结构和消费行为。同时,新生代农民工也面临生产生活方式和消费方式的变化,其收入提高与消费行为转变更是实现我国经济转型的重要推动力。基于此,本文选取郑州市作为样本地区,对新生代农民工的收入状况、消费观念和消费行为进行实地调查,运用Logist模型分析其收入状况、消费观念对其消费行为选择的影响。最后,从改善新生代农民工收入状况、人力资本提升和消费观念的引导等方面提出科学、合理的建议。  相似文献   
103.
104.
105.
106.
Transition Metal Chemistry - Two cubane-like complexes, namely [Ni4L4(HOEt)4] (1), [Co4L4(HOEt)4] (2) (H2L?=?(E)-2-((3-hydroxypropylimino)methyl)-6-methoxyphenol), were prepared under...  相似文献   
107.
Guided by the self-penetrating features can improve the stability of metal organic frameworks (MOFs), an unprecedented 3D self-penetrated framework, {[Zn (tptc)0.5(bimb)]·H2O}n ( NUC-6 , here NUC corresponding to North University of China), with 3D (4,4)-c {86} net, was designed. Benefit from the high chemical stability and excellent luminescent property, NUC-6 can be act as an efficient multi-response chemo-sensor in detecting dichloronitroaniline pesticide and nitrofuran antibiotics in water with the detection limits are 116 ppb for DCN pesticide, 16 ppb for NFT antibiotic, and 12 ppb for NTZ antibiotic. Besides, the mechanisms of luminescence quenching were revealed from the viewpoint of internal filter effect (IFE) and photo-induced electron transfer (PET), implied by the optical spectroscopy and quantum chemical calculation. This work provides a promising strategy to design stable MOFs by improving the self-penetrating features and to expand their practical applications in the detection of organic pollutants in aqueous medium.  相似文献   
108.
Because of its unpredictable side effects and efficacy, the anticancer drug docetaxel (DTX) requires improved characterisation of its pharmacokinetic profiles through population pharmacokinetic studies. A sensitive and rugged LC–MS/MS method for the detection of DTX in human plasma was developed and optimised using paclitaxel as an internal standard (IS). The plasma samples underwent rapid extraction using hybrid solid-phase extraction-protein precipitation. The analyte and IS were separated with an isocratic system on a Zorbax Eclipse Plus C18 column using water containing 0.05% acetic acid along with 20 μM of sodium acetate and methanol (30/70, v/v) as the mobile phase. Quantification was performed using a triple quadrupole mass spectrometer through multiple reaction monitoring in positive mode, using the m/z 830.3 → 548.8 and m/z 876.3 → 307.7 transitions for DTX and paclitaxel, respectively. The range of the calibration curve was 1–500 ng/mL for DTX, and the linear correlation coefficient was >0.99. The accuracies ranged from −4.6 to 4.2%, and the precision was no higher than 7.0% for the analytes. No significant matrix effect was observed. Both DTX and the IS showed considerable recovery. This method was finally applied to the establishment of a population pharmacokinetic model to optimise the clinical use of DTX.  相似文献   
109.
We numerically solve the time-dependent Ginzburg–Landau equations for two-gap superconductors using the finite-element technique. The real-time simulation shows that at low magnetic field, the vortices in small-size samples tend to form clusters or other disorder structures. When the sample size is large, stripes appear in the pattern. These results are in good agreement with the previous experimental observations of the intriguing anomalous vortex pattern, providing a reliable theoretical basis for the future applications of multi-gap superconductors.  相似文献   
110.
We propose a system of time-division multiplexing(TDM) and spatial frequency-division multiplexing(SFDM). Extrinsic Fabry–Perot interferometric sensors are applied to detect weak acoustic signals. The broadband source is employed, the light from it is modulated by a pulse signal sequence and is efficiently amplified by semiconductor optical amplifiers. Experimental results show that the equivalent noise pressure spectrum level is-97.2 d B re 1 rad/√Hz below 1250 Hz, and the cross talk between two sensors in one TDM channel is-32.7 d B with a cavity length difference of 60 μm. The number of sensors in this multiplexing system can theoretically reach 160.  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