全文获取类型
收费全文 | 21159篇 |
免费 | 3435篇 |
国内免费 | 2413篇 |
专业分类
化学 | 14670篇 |
晶体学 | 208篇 |
力学 | 1533篇 |
综合类 | 199篇 |
数学 | 2353篇 |
物理学 | 8044篇 |
出版年
2024年 | 70篇 |
2023年 | 407篇 |
2022年 | 718篇 |
2021年 | 817篇 |
2020年 | 850篇 |
2019年 | 807篇 |
2018年 | 696篇 |
2017年 | 605篇 |
2016年 | 998篇 |
2015年 | 1032篇 |
2014年 | 1171篇 |
2013年 | 1540篇 |
2012年 | 1802篇 |
2011年 | 1987篇 |
2010年 | 1258篇 |
2009年 | 1197篇 |
2008年 | 1227篇 |
2007年 | 1131篇 |
2006年 | 1117篇 |
2005年 | 929篇 |
2004年 | 832篇 |
2003年 | 613篇 |
2002年 | 571篇 |
2001年 | 505篇 |
2000年 | 459篇 |
1999年 | 432篇 |
1998年 | 382篇 |
1997年 | 326篇 |
1996年 | 340篇 |
1995年 | 319篇 |
1994年 | 301篇 |
1993年 | 233篇 |
1992年 | 248篇 |
1991年 | 206篇 |
1990年 | 181篇 |
1989年 | 152篇 |
1988年 | 91篇 |
1987年 | 89篇 |
1986年 | 76篇 |
1985年 | 76篇 |
1984年 | 42篇 |
1983年 | 44篇 |
1982年 | 38篇 |
1981年 | 22篇 |
1980年 | 15篇 |
1979年 | 8篇 |
1977年 | 5篇 |
1975年 | 6篇 |
1969年 | 4篇 |
1957年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
This Feature Article describes our recent researches on processing poly(3,4-ethylenedioxythiophene /poly(4-styrenesulfonate) (PEDOT/PSS) colloidal dispersion into thin films which exhibit high conductivity and high transparency, and into microfibers which exhibit high conductivity and high mechanical strength. The state-of-the-art thin films and microfibers are expected to utilize to sophisticated touch screens and wearable electronic devices as organic transparent electrodes and woven electric circuits, respectively. 相似文献
992.
Correlation of Cooperatively Localized Rearrangement on the “Fluidized Domain”of Polymers to Their Nonexponentially Viscoelastic Behavior and Lifetime at Double Aging Processes II: Estimation of Long-term Mechanical Behavior and Lifetime of Polymeric Mate 下载免费PDF全文
Three kinds of polymeric materials are taken as example for the verification of linear ex-trapolation method from unified master lines with reduced universal equations on creep and stress relaxation tests. The theoretical values of long-term mechanical behavior and lifetime for a cured epoxide, polypropylene, poly(methyl-methacrylate), and SBR rubber are directly evaluated with the universal equations on reduced creep compliance and reduced stress relax-ation modulus and are compared with their predicted values by the linear extrapolation from the unified master lines of creep and stress relaxation. The results show that the theoretical values of dimensional stability, bearing ability and lifetime are in an excellent agreement with the predicted values, it shows that the linear extrapolation method is more simple and reliable. The dependences of long-term mechanical behaviors and lifetime on the different aging times are discussed. 相似文献
993.
The electronic structures and optical properties of rocksalt indium nitride (InN) under pres-sure were studied using the first-principles calculation by considering the exchange and cor-relation potentials with the generalized gradient approximation. The calculated lattice con-stant shows good agreement with the experimental value. It is interestingly found that the band gap energy Eg at the Γ or X point remarkably increases with increasing pressure, but Eg at the L point does not increase obviously. The pressure coefficient of Eg is calculated to be 44 meV/GPa at the Γ point. Moreover, the optical properties of rocksalt InN were calculated and discussed based on the calculated band structures and electronic density of states. 相似文献
994.
Xiaopei Miao Lu Liu Shukuan Wang Hong Lin Baoyun Sun Jingbo Hu Meixian Li 《Electrochemistry communications》2010,12(1):90-93
A new ferrocenecarboxylic acid–C60 composite (Fc–C60) has been synthesized by controlled potential electrolysis. A composite modified glassy carbon electrode has been prepared based on its good electrochemical activity. The modified electrode in 0.1 M NaClO4 solution shows a reversible oxidation wave at E1/2 = 0.32 V (vs. SCE) attributed to the oxidation of the ferrocene entity and a quasi-reversible reduction wave of C60 entity at E1/2 = ?0.54 V (vs. SCE). Electrocatalytic studies show that Fc–C60 at the modified electrode can mediate the reduction of hydrogen peroxide (H2O2), and a broad linear range from 1.2 μM to 21.9 mM for H2O2 were obtained with a determination limit of 2.5 × 10?7 M by amperometry. 相似文献
995.
996.
Wei‐Ching Liao Nobuhiko Watari Shengnian Wang Xin Hu Ronald G. Larson Ly James Lee 《Electrophoresis》2010,31(16):2813-2821
The electrophoresis of λ‐DNA is observed in a microscale converging channel where the center‐of‐masses trajectories of DNA molecules are tracked to measure instantaneous electrophoretic (EP) mobilities of DNA molecules of various stretch lengths and conformations. Contrary to the usual assumption that DNA mobility is a constant, independent of field and DNA length in free solution, we find DNA EP mobility varies along the axis in the contracting geometry. We correlate this mobility variation with the local stretch and conformational changes of the DNA, which are induced by the electric field gradient produced by the contraction. A “shish‐kebab” model of a rigid polymer segment is developed, which consists of aligned spheres acting as charge and drag centers. The EP mobility of the shish‐kebab is obtained by determining the electrohydrodynamic interactions of aligned spheres driven by the electric field. Multiple shish‐kebabs are then connected end‐to‐end to form a freely jointed chain model for a flexible DNA chain. DNA EP mobility is finally obtained as an ensemble average over the shish‐kebab orientations that are biased to match the overall stretch of the DNA chain. Using physically reasonable parameters, the model agrees well with experimental results for the dependence of EP mobility on stretch and conformation. We find that the magnitude of the EP mobility increases with DNA stretch, and that this increase is more pronounced for folded conformations. 相似文献
997.
Yue‐Hu Wang Qian‐Yun Sun Fu‐Mei Yang Chun‐Lin Long Fu‐Wei Zhao Gui‐Hua Tang Hong‐Mei Niu Huan Wang Qiao‐Qin Huang Jin‐Jin Xu Li‐Juan Ma 《Helvetica chimica acta》2010,93(12):2467-2477
Ten new phenolic compounds including the six neolignans 1 – 3 and 6 – 8 and four caffeoyl derivatives, i.e., myo‐inositol 1‐caffeate ( 9 ), myo‐inositol 6‐caffeate ( 10 ), myo‐inositol 5‐caffeate ( 11 ), and paucine 3′‐β‐D ‐glucopyranoside ( 12 ) were isolated from the whole plants of Selaginella moellendorffii (caffeic acid=3‐(3,4‐dihydroxyphenyl)prop‐2‐enoic acid). Their structures were established by spectroscopic and chemical methods. 相似文献
998.
Different biomolecular force fields (OPLS‐AA, AMBER03, and GROMOS96) in conjunction with SPC, SPC/E and TIP3P water models are assessed for molecular dynamics simulations in a tetragonal lysozyme crystal. The root mean square deviations for the Ca atoms of lysozymes are about 0.1 to 0.2 nm from OPLS‐AA and AMBER03, smaller than 0.4 nm from GROMOS96. All force fields exhibit similar pattern in B‐factors, whereas OPLS‐AA and AMBER03 accurately reproduce experimental measurements. Despite slight variations, the primary secondary structures are well conserved using different force fields. Water diffusion in the crystal is approximately ten‐fold slower than in bulk phase. The directional and average water diffusivities from OPLS‐AA and AMBER03 along with SPC/E model match fairly well with experimental data. Compared to GROMOS96, OPLS‐AA and AMBER03 predict larger hydrophilic solvent‐accessible surface area of lysozyme, more hydrogen bonds between lysozyme and water, and higher percentage of water in hydration shell. SPC, SPC/E and TIP3P water models have similar performance in most energetic and structural properties, but SPC/E outperforms in water diffusion. While all force fields overestimate the mobility and electrical conductivity of NaCl, a combination of OPLS‐AA for lysozyme and the Kirkwood‐Buff model for ions is superior to others. As attributed to the steric restraints and surface interactions, the mobility and conductivity in the crystal are reduced by one to two orders of magnitude from aqueous solution. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 相似文献
999.
Four three‐dimensional heterometallic coordination polymers, [Ln2Cu4I3(IN)7(H2O)]n ( 1 , 2 ) and [LnCu3.5I3(IN)3.5(H2O)3]n · nH2O ( 3 , 4 ) [HIN = isonicotinic acid, Ln = Nd ( 1 ), Gd ( 2 ), La ( 3 ), Eu ( 4 )] were hydrothermally synthesized by using lanthanide oxides, isonicotinic acid, copper chloride, and potassium iodide. The different molar ratio of raw materials results in two distinct types of three‐dimensional frameworks of compounds 1 – 4 . The structure of compounds 1 and 2 are constructed by the layer modules of [Ln2(IN)7(H2O)]nn– and Cu4I3 clusters, whereas that of compounds 3 and 4 are built by dimeric Ln2(IN)6(H2O)6 and layered polymeric [Cu7I6]nn+ units. 相似文献
1000.
Luo Mei Sun Jie Zhou Shi-Ming Yin Hao Hu Ke-Liang 《Research on Chemical Intermediates》2010,36(9):1049-1054
Two opposite configuration (R/S) of chiral complexes (C8H11N)2·CuCl2 were obtained from the reaction of chiral d(+)/l(−)-α-ethylphenyl amine with copper chloride (II) in dry ethanol. The crystal structures of 1a and 1b were characterized by
IR, elemental analysis and X-ray crystallography. 相似文献