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1.
Shiyang  Tian  Yanjun  Fu  Jiannan  Gui  Baiheng  Ma  Zhanjun  Yan 《Optical Review》2022,29(3):215-224
Optical Review - Fringe projection profilometry is widely used for the 3D measurement of real-world objects; however, quickly obtaining high-precision 3D measurements is an issue that needs to be...  相似文献   
2.
The reaction of N2 with trinuclear niobium and tungsten sulfide clusters Nb3Sn and W3Sn (n=0–3) was systematically studied by density functional theory calculations with TPSS functional and Def2-TZVP basis sets. Dissociations of N−N bonds on these clusters are all thermodynamically allowed but with different reactivity in kinetics. The reactivity of Nb3Sn is generally higher than that of W3Sn. In the favorite reaction pathways, the adsorbed N2 changes the adsorption sites from one metal atom to the bridge site of two metal atoms, then on the hollow site of three metal atoms, and at that place, the N−N bond dissociates. As the number of ligand S atoms increases, the reactivity of Nb3Sn decreases because of the hindering effect of S atoms, while W3S and W3S2 have the highest reactivity among four W3Sn clusters. The Mayer bond order, bond length, vibrational frequency, and electronic charges of the adsorbed N2 are analyzed along the reaction pathways to show the activation process of the N−N bond in reactions. The charge transfer from the clusters to the N2 antibonding orbitals plays an essential role in N−N bond activation, which is more significant in Nb3Sn than in W3Sn, leading to the higher reactivity of Nb3Sn. The reaction mechanisms found in this work may provide important theoretical guidance for the further rational design of related catalytic systems for nitrogen reduction reactions (NRR).  相似文献   
3.
利用微环谐振腔阵列进行光码分多址编解码过程中,微环谐振腔反射谱的自由频谱宽度(FSR)范围制约该系统用户容量的提升.本文提出了一种新型的基于游标效应的串联哑铃型微环谐振腔光编解码器.利用Matlab建立了半径分别为40μm-30μm-40μm的哑铃型微环谐振腔光编解码器模型.详细分析了光反射谱伪模抑制与耦合系数的关系,研究了耦合系数、码片速率对串联哑铃型微环谐振腔光编解码器性能的影响.结果表明,与半径分别为40μm-40μm-40μm的传统串联微环谐振腔编解码器相比,哑铃型微腔编解码器FSR值扩大了4倍.理想情况下,用户容量可呈指数增长.同时,互相关峰值比(P/W)与自相关峰值旁瓣比(P/C)分别提高了约33%和8%.  相似文献   
4.
分子构象的聚类是搜索分子动力学模拟轨迹中代表构象的主要方法。 它是分析复杂构象改变或分子间相互作用机制的关键步骤. 作为一种基于密度的聚类算法,密度峰值搜索算法因其聚类的准确度而被应用于分子聚类过程中. 但随着模拟时长的增长,密度峰值搜索算法较低的计算效率限制了其应用的可能. 本文提出K-means密度峰值搜索算法的聚类算法,它是密度峰值搜索算法在计算效率方面的一个扩展版本,用于解决密度峰值搜索算法中巨大的资源消耗问题. 在K-means密度峰值搜索算法中,首先,通过高效的聚类算法(例如K-means)进行初始聚类,得到的聚类中心被定义为具有权重的典型点. 然后,对加权的典型点通过密度峰值搜索算法实现二次聚类,并细化点为核心点、边界点、加细光晕点. 在与密度峰值搜索算法具有相似的精度的同时,计算复杂度由O(n2)降至O(n). 通过二面角,二级结构,关联图描述的分子构象,将KFDP用于多个模拟轨迹的聚类过程中. 并通过与K-means聚类算法,DBSCAN聚类算法的比较结果,验证了K-means密度峰值搜索算法的优势.  相似文献   
5.
针对线性相控阵列在固体介质中的声场聚焦特性及参数优化问题,该文给出了一个线性阵列的纵波瞬态聚焦声场模型。数值结果表明,当阵元被短时脉冲信号激励时,瞬态聚焦声场中不会形成栅瓣,突破了传统稳态理论模型中对阵元间距的限制;同时由于横纵波在聚焦区域内可完全分离,声束旁瓣的幅值也得到了抑制。其次,增大阵元间距能够显著提高聚焦性能,但会导致聚焦声场能量减弱,综合考虑后,最佳的阵元间距为一个波长左右。并且发现,阵元宽度对于聚焦性能几乎没有影响,但宽阵元能够提高聚焦能量。此外,受到纵波激发特性的影响,使得相控阵只能在低偏转角处获得理想的纵波聚焦性能。最后,采用不同阵元间距的相控阵探头对试块进行成像实验,观察到大阵元间距可以显著改善缺陷成像分辨率,从而验证了理论分析的结果。  相似文献   
6.
大学化学实验课程是培养材料、化学、化工等专业人才应用基本操作和理论解决实际问题的综合性实践训练环节。文章探讨了当前大学化学实验发展由于受到仪器设备大型化、专业化、成本大、更新快等因素限制出现瓶颈,设计了线上线下混合实验教学模式,进行相应的软硬件建设,并开展线上线下混合式实验教学模式的改革与探索。该教学模式具有良好的教学效果,并且可复制可推广,为创新人才的培养和实验教学的创新提供了有益的借鉴。  相似文献   
7.
Saxifraga atrata is an important traditional Tibetan medicine used to treat cough and pneumonia, and has tremendous medicinal potential. In this study, we devised a technique to separate 1,1-diphenyl-2-picrylhydrazyl inhibitors from a methanol extract of S. atrata. The material was first processed using MCI GEL CHP20P medium-pressure liquid chromatography, yielding 1.1 g of the target fraction Fr2. Subsequently, online hydrophilic interaction liquid chromatography-1,1-diphenyl-2-picrylhydrazyl assay was used to identify prospective 1,1-diphenyl-2-picrylhydrazyl inhibitors, and two 1,1-diphenyl-2-picrylhydrazyl inhibitor fractions (Fr24 and Fr25) were identified from Fr2. Then, medium-pressure preparation was continued using an XIon column to separate two 1,1-diphenyl-2-picrylhydrazyl inhibitor fractions (Fr24 and Fr25). The target compound was concentrated in fractions Fr24 and Fr25 using reverse-phase liquid chromatography during further separation procedures. Finally, the purity, structure, and 1,1-diphenyl-2-picrylhydrazyl inhibitory activity of the isolated 1,1-diphenyl-2-picrylhydrazyl inhibitors were determined. Two 1,1-diphenyl-2-picrylhydrazyl inhibitors (adenosine with the half maximal inhibitory concentration of 66.87 ± 14.33 μM and (-)-4-O-(E)-caffeoyl-l -threonic acid with the half maximal inhibitory concentration of 59.06 ± 5.02 μM) were isolated with purities exceeding 95%. The results showed that this technology is effective in the targeted separation of antioxidants from natural products.  相似文献   
8.
Science China Mathematics - This paper studies exact synchronization and asymptotic synchronization problems for a controlled linear system of ordinary differential equations. In this paper, we...  相似文献   
9.
DNA methyltransferase (DNA MTase) can act as biomarker for many diseases and it is important to develop some new methods for sensitive detection of DNA MTase. In this work, a highly efficient electrochemiluminescence (ECL) sensor had been designed for detection of DNA MTase based on Ru(phen)32+ loaded double strand DNA (dsDNA- Ru(phen)32+) as signal tags. Ru(phen)32+ had been efficiently embed in the dsDNA produced through a simple hybridization chain reaction. First, a hairpin probe was designed, which can be specifically recognized by Dam MTase and modified with -SH at one end. It was modified on the surface of gold electrode by -SH as an immobilization probe (IP). This IP will be methylated in the present of Dam MTase and digested by DpnI following. Results in the release of capture probe (CP) which remains on the surface of gold electrode. The CP can hybridize with the single stand part of the dsDNA- Ru(phen)32+ and make the immobilization of ECL tags on the electrode surface, which results in a strong ECL signals detected. However, without the effect of Dam MTase, the hairpin structure of IP remains stable and cannot capture signal tags, and can only detecte weak ECL signals. The biosensor can detect the activity of Dam MTase in the concentration range of 0.01 U/mL to 20 U/mL with the ECL intensity and the logarithm of the concentration have a linear relationship, and the detection limit is calculated to be 7.6 mU/mL. The developed sensor has the ability to specifically detect Dam MTase, which can be differentiated from other types of DNA MTase. In addition, the designed method has good applicability to detect Dam MTase activity in serum samples and been applied to detect its inhibitor with high efficiency.  相似文献   
10.
Qin  Kaiwei  Guo  Lei  Ming  Shujun  Zhang  Shoute  Guo  Yanbin  Pang  Lei  Li  Tao 《Catalysis Surveys from Asia》2022,26(2):115-128
Catalysis Surveys from Asia - The catalytic performances and mechanism differences of model catalysts Cu–SSZ-13 and Fe–SSZ-13 with similar metal content and Si/Al ratio were compared....  相似文献   
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