全文获取类型
收费全文 | 5353篇 |
免费 | 1267篇 |
国内免费 | 722篇 |
专业分类
化学 | 4158篇 |
晶体学 | 42篇 |
力学 | 228篇 |
综合类 | 22篇 |
数学 | 66篇 |
物理学 | 2826篇 |
出版年
2024年 | 17篇 |
2023年 | 73篇 |
2022年 | 161篇 |
2021年 | 186篇 |
2020年 | 274篇 |
2019年 | 212篇 |
2018年 | 177篇 |
2017年 | 204篇 |
2016年 | 271篇 |
2015年 | 284篇 |
2014年 | 386篇 |
2013年 | 461篇 |
2012年 | 368篇 |
2011年 | 385篇 |
2010年 | 306篇 |
2009年 | 322篇 |
2008年 | 359篇 |
2007年 | 324篇 |
2006年 | 311篇 |
2005年 | 257篇 |
2004年 | 274篇 |
2003年 | 219篇 |
2002年 | 182篇 |
2001年 | 158篇 |
2000年 | 147篇 |
1999年 | 152篇 |
1998年 | 139篇 |
1997年 | 108篇 |
1996年 | 104篇 |
1995年 | 70篇 |
1994年 | 70篇 |
1993年 | 52篇 |
1992年 | 63篇 |
1991年 | 39篇 |
1990年 | 32篇 |
1989年 | 24篇 |
1988年 | 26篇 |
1987年 | 22篇 |
1986年 | 27篇 |
1985年 | 9篇 |
1984年 | 17篇 |
1983年 | 4篇 |
1982年 | 16篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 12篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1974年 | 4篇 |
排序方式: 共有7342条查询结果,搜索用时 15 毫秒
991.
Chokchai Kaiyasuan Pongsakorn Chasing Phattananawee Nalaoh Praweena Wongkaew Dr. Taweesak Sudyoadsuk Dr. Kanokwan Kongpatpanich Prof. Vinich Promarak 《化学:亚洲杂志》2021,16(16):2328-2337
Herein, two deep-blue emissive molecules ( SAF-PI and SAF-DPI ) are designed and synthesized using spiro[acridine-9,9’-fluorene] as a donor (D) substituted with 2-(3-methylphenyl)-1-phenyl-phenanthro[9,10-d]imidazole as an acceptor (A), forming twisted D−A and A−D−A structures, respectively. The photophysical studies and density functional theory (DFT) calculations reveal that both molecules exhibit hybridized local excited and charge transfer (HLCT) characteristics with deep blue emission color. They are effectively applied as non-doped emitters in OLEDs. Particularly, SAF-PI -based device achieves the high-definition television (HDTV) standard blue color emission peaked at 428 nm with CIE coordinate of (0.156, 0.053), a narrow full width at half maximum of 55 nm, a maximum external quantum efficiency (EQEmax) of 4.57% and an exciton utilization efficiency of 65%. 相似文献
992.
Optical trapping forces of polystyrene microspheres are analyzed both theoretically and experimentally, and comparisons are
made between the two. Discrepancies are mainly caused by straight-ray approximation for axial trapping, and by trapping-position
vertical displacement due to gravity for transverse trapping. 相似文献
993.
994.
Amine‐Responsive Adaptable Nanospaces: Fluorescent Porous Coordination Polymer for Molecular Recognition 下载免费PDF全文
Ritesh Haldar Prof. Ryotaro Matsuda Prof. Susumu Kitagawa Prof. Subi J. George Prof. Tapas Kumar Maji 《Angewandte Chemie (International ed. in English)》2014,53(44):11772-11777
Flexible and dynamic porous coordination polymers (PCPs) with well‐defined nanospaces composed of chromophoric organic linkers provide a scaffold for encapsulation of versatile guest molecules through noncovalent interactions. PCPs thus provide a potential platform for molecular recognition. Herein, we report a flexible 3D supramolecular framework {[Zn(ndc)(o‐phen)]?DMF}n (o‐phen=1,10‐phenanthroline, ndc=2,6‐napthalenedicarboxylate) with confined nanospaces that can accommodate different electron‐donating aromatic amine guests with selective turn‐on emission signaling. This system serves as a molecular recognition platform through an emission‐readout process. Such unprecedented tunable emission with different amines is attributed to its emissive charge‐transfer (CT) complexation with o‐phen linkers. In certain cases this CT emission is further amplified by energy transfer from the chromophoric linker unit ndc, as evidenced by single‐crystal X‐ray structural characterization. 相似文献
995.
用斜坡电压法(Voltage Ramp, V-ramp)评价了0.18μm双栅极 CMOS工艺栅极氧化膜击穿电量(Charge to Breakdown, Qbd)和击穿电压(Voltage to Breakdown, Vbd). 研究结果表明,低压器件(1.8V)的栅极氧化膜(薄氧)p型衬底MOS电容和N型衬底电容的击穿电量值相差较小,而高压器件(3.3V)栅极氧化膜(厚氧)p衬底MOS电容和n衬底MOS电容的击穿电量值相差较大,击穿电压测试值也发现与击穿电量
关键词:
薄氧
可靠性
击穿电压
击穿电量 相似文献
996.
LIU Yan-Ping CHEN Zhao-Yang BA Wei-Zhen FAN Yan-Wei DU Yan-Zhao PAN Shi-Lie GUO Qi 《中国物理C(英文版)》2008,32(5)
The optically stimulated luminescent (OSL) radiation dosimeter technically surveys a wide dynamic measurement range and a high sensitivity.Optical fiber dosimeters provide capability for remote monitoring of the radiation in the locations which are difficult-to-acoess and hazardous.In addition.optical fiber dosimeters are immune to electrical and radio-frequency interference.In this paper,a novel remote optical fiber radiation dosimeter is described.The optical fiber dosimeter takes advantage of the charge trapping materials CaS:Ce, Sm that exhibit OSL.The measuring range of the dosimeter is from 0.1 to 100 Gy.The equipment is relatively simple and small in size,and has low power consumption.This device is suitable for measuring the space radiation dose and also can be used in high radiation dose condition and other dangerous radiation occasions. 相似文献
997.
研究了客体模型FTO的闪光照相系统X光输运过程,给出了直穿照射量、散射照射量、直散比、直穿照射量能谱、散射照射量能谱、直穿X光通量能谱和散射X光通量能谱在记录平面的空间分布。结果表明:后锥是照射量散射成分的主要来源,后锥照射量占总散射量97%;后锥也是造成散射的空间分布不均匀的主要器件,这一不均匀性高达58%。照相系统的最小直散比非常小,表明锥造成的散射已经严重地淹没了直穿(轫致辐射)信号。计算中使用高空间分辨率记录法进行分点,合成图像对吸收系数的复原结果与国外报道的结果相符。 相似文献
998.
Quantum dynamics of charge transfer on the one-dimensional lattice:Wave packet spreading and recurrence 下载免费PDF全文
The wave function temporal evolution on the one-dimensional(1D) lattice is considered in the tight-binding approximation. The lattice consists of N equal sites and one impurity site(donor). The donor differs from other lattice sites by the on-site electron energy E and the intersite coupling C. The moving wave packet is formed from the wave function initially localized on the donor. The exact solution for the wave packet velocity and the shape is derived at different values E and C. The velocity has the maximal possible group velocity v = 2. The wave packet width grows with time ~ t1/3and its amplitude decreases ~ t-1/3. The wave packet reflects multiply from the lattice ends. Analytical expressions for the wave packet front propagation and recurrence are in good agreement with numeric simulations. 相似文献
999.
电极过程自由基中间体的ESR研究——取代苯基重氮盐的电解还原 总被引:2,自引:0,他引:2
本文用自由基捕捉剂苯亚甲基叔丁基氮氧化物(PBN)与ESR相结合的方法研究了十种取代苯基重氮盐RC6H4N2+BF4-(R=F,Cl,Br,NO2,OCH3及CH3)在乙腈中电解还原产生的活泼自由基。结果表明:1.RC6H4N2+BF4-电解还原时产生RC6H4自由基,并能被捕捉剂PBN所捕捉,以形成稳定的自由基加合物[RC6H4-PBN]·。2.由[RC6H4-PBN]·ESR谱的超精细裂分常数算出的二面角θβ值大小与处于不同位置的给定取代基R的关系为:θβ(O-R) < θβ(m-R) < θβ(P-R) 相似文献
1000.
《Acta Crystallographica. Section C, Structural Chemistry》2017,73(10):803-809
Specific short contacts are important in crystal engineering. Hydrogen bonds have been particularly successful and together with halogen bonds can be useful for assembling small molecules or ions into crystals. The ionic constituents in the isomorphous 3,5‐dichloropyridinium (3,5‐diClPy) tetrahalometallates 3,5‐dichloropyridinium tetrachloridozincate(II), (C5H4Cl2N)2[ZnCl4] or (3,5‐diClPy)2ZnCl4, 3,5‐dichloropyridinium tetrabromidozincate(II), (C5H4Cl2N)2[ZnBr4] or (3,5‐diClPy)2ZnBr4, and 3,5‐dichloropyridinium tetrabromidocobaltate(II), (C5H4Cl2N)2[CoBr4] or (3,5‐diClPy)2CoBr4, arrange according to favourable electrostatic interactions. Cations are preferably surrounded by anions and vice versa ; rare cation–cation contacts are associated with an antiparallel dipole orientation. N—H…X (X = Cl and Br) hydrogen bonds and X …X halogen bonds compete as closest contacts between neighbouring residues. The former dominate in the title compounds; the four symmetrically independent pyridinium N—H groups in each compound act as donors in charge‐assisted hydrogen bonds, with halogen ligands and the tetrahedral metallate anions as acceptors. The M —X coordinative bonds in the latter are significantly longer if the halide ligand is engaged in a classical X …H—N hydrogen bond. In all three solids, triangular halogen‐bond interactions are observed. They might contribute to the stabilization of the structures, but even the shortest interhalogen contacts are only slightly shorter than the sum of the van der Waals radii. 相似文献