全文获取类型
收费全文 | 2602篇 |
免费 | 73篇 |
国内免费 | 7篇 |
专业分类
化学 | 1612篇 |
晶体学 | 29篇 |
力学 | 82篇 |
数学 | 278篇 |
物理学 | 681篇 |
出版年
2021年 | 16篇 |
2020年 | 25篇 |
2019年 | 24篇 |
2018年 | 18篇 |
2016年 | 37篇 |
2015年 | 50篇 |
2014年 | 40篇 |
2013年 | 92篇 |
2012年 | 120篇 |
2011年 | 154篇 |
2010年 | 79篇 |
2009年 | 53篇 |
2008年 | 130篇 |
2007年 | 125篇 |
2006年 | 130篇 |
2005年 | 121篇 |
2004年 | 82篇 |
2003年 | 89篇 |
2002年 | 90篇 |
2001年 | 62篇 |
2000年 | 61篇 |
1999年 | 44篇 |
1998年 | 35篇 |
1997年 | 30篇 |
1996年 | 44篇 |
1995年 | 30篇 |
1994年 | 35篇 |
1993年 | 41篇 |
1992年 | 32篇 |
1991年 | 33篇 |
1990年 | 21篇 |
1989年 | 30篇 |
1988年 | 29篇 |
1987年 | 31篇 |
1986年 | 37篇 |
1985年 | 44篇 |
1984年 | 44篇 |
1983年 | 28篇 |
1982年 | 34篇 |
1981年 | 31篇 |
1980年 | 28篇 |
1979年 | 34篇 |
1978年 | 34篇 |
1977年 | 30篇 |
1976年 | 29篇 |
1975年 | 31篇 |
1974年 | 30篇 |
1973年 | 24篇 |
1971年 | 20篇 |
1967年 | 17篇 |
排序方式: 共有2682条查询结果,搜索用时 15 毫秒
121.
Wood TE Ross AC Dalgleish ND Power ED Thompson A Chen X Okamoto Y 《The Journal of organic chemistry》2005,70(24):9967-9974
[structure: see text] A series of bis(dipyrromethene)s substituted with aromatic amide and aliphatic ester homochiral auxiliaries have been prepared and complexed with zinc(II) ions to form double-helical dinuclear complexes. CD analysis of the crude complexes revealed that the helicates formed in a diastereoselective manner. The helicates have been resolved into their constituent M and P helices by HPLC, indicating that the helical sense of the complexes is stable to racemization. 相似文献
122.
Dorothy V. Bautista Graham Bullock Frederick W. Hartstock Laurence K. Thompson 《Journal of heterocyclic chemistry》1983,20(2):345-347
Two general procedures involving the condensation of phthalonitrile or 1,3-diiminoisoindoline with various aminopicolines, followed by ring expansion with hydrazine to the corresponding phthalazine are described. Syntheses are reported of 1, 4-di(3′-methyl-2′-pyridyl) aminophthalazine, 1,4-di(5′-methyl-2′-pyridyl)aminophthalazine, and 1,4-di(4′, 6′-dimethyl-2′-pyridyl)aminophthalazine. 相似文献
123.
Philip L. Wylie Richard J. Phillips Kenneth J. Klein Michael Q. Thompson Bruce W. Hermann 《Journal of separation science》1991,14(10):649-655
An experimental injection port has been designed for split or splitless sample introduction in capillary gas chromatography; the inlet uses electronic pressure control, in order that the column head pressure may be set from the GC keyboard, and the inlet may be used in the constant flow or constant pressure modes. Alternatively, the column head pressure may be programmed up or down during a GC run in a manner analogous to even temperature programming. Using electronic pressure control, a method was developed which used high column head pressures (high column flow rates) at the time of injection, followed by rapid reduction of the pressure to that required for optimum GC separation. In this way, high flow rates could be used at the time of splitless injection to reduce sample discrimination, while lower flow rates could be used for the separation. Using this method, up to 5 μl of a test sample could be injected in the splitless mode with no discrimination; in another experiment, 2.3 times as much sample was introduced into the column by using electronic pressure programming. Some GC peak broadening was observed in the first experiment. 相似文献
124.
Effects of high intensity ultrasound on inorganic solids 总被引:5,自引:0,他引:5
Ultrasonic irradiation dramatically affects the reactivity of a variety of inorganic solids. We have found, for example, large increases in the rates of intercalation of a wide range of compounds into various layered inorganic solids (such as ZrS2, V2O5, TaS2 and MoO3. High intensity ultrasound also enhances the heterogeneous catalysis of alkene hydrogenation by Ni powders. Scanning electron microscopy reveals that ultrasound has multiple effects on the morphology and surface characteristics of inorganic solids, creating substantial surface damage, increasing surface areas significantly and causing increased particle aggregation. 相似文献
125.
Matthew Thompson Carolyn Carkner Adrian Bailey Nicholas J. Mosey Nadia Kapernaum 《Liquid crystals》2013,40(9):1246-1260
Two sterically equivalent series of phenoxy-terminated 5-alkoxy-2-(4-alkoxyphenyl)pyrimidine liquid crystals were synthesised, and their mesogenic properties were characterised by polarised optical microscopy and differential scanning calorimetry (DSC). The phenoxy end-group causes a significant increase in melting point and inhibits – at least partially – the mesomorphism of these materials relative to the parent isomers; in most cases, the broad enantiotropic SmC phase formed by the parent isomers is suppressed by the addition of the phenoxy end-group. However, detailed analyses by small-angle X-ray scattering and monodomain 2D X-ray scattering suggest that these compounds form a SmA phase with a partially intercalated bilayer structure in which the phenoxy end-groups are nanosegregated. Such an intercalated bilayer structure might enable the tuning of smectogenic properties by appropriate substitution of the phenoxy end-groups. 相似文献
126.
M. E. Thompson 《International journal of environmental analytical chemistry》2013,93(3):253-255
Abstract The Orion water-hardness electrode, while being used to measure magnesium ion activity in a series of calcium-free solutions, displayed some unanticipated changes in potential. As the overall potential change observed for one solution was 183 mV (equivalent to more than six orders of magnitude changes in magnesium-ion activity), several precautions are suggested which should be observed when using this electrode for specific purposes. In particular, it is recommended that the exchanger be pre-equilibrated with an appropriate solution if the electrode is to be used in restricted systems of known chemical composition. 相似文献
127.
128.
Young‐gi kim Emilie M. Galand Barry C. Thompson John walker Stephen A. Fossey Tracy D. Mccarley 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(7):665-674
Isoregic conjugated polymers composed of thiophene and dialkoxybenzene units were designed to harvest incident light in the mid‐visible energy range (band gap of 2.1 eV). Poly(1,4‐bis(2‐thienyl)‐2,5‐diheptoxybenzene) (PBTB(OC7H15)2) and poly(1,4‐bis(2‐thienyl)‐2,5‐didodecyloxybenzene) (PBTB(OC12H25)2) have shown significant photovoltaic performance as an electron donor when used in tandem with the electron acceptor [6, 6]‐phenyl C61‐butyric acid methyl ester (PCBM) in bulk hetero‐junction photovoltaic devices. Photovoltaic devices incorporating PBTB(OC7H15)2 and PCBM have shown AM1.5 efficiencies of ~0.6% with a short circuit current density of 2.5 mA/cm2, an open circuit voltage of 0.74 V, and a fill factor of 0.32. Incident Photon‐to‐Current Efficiency (IPCE) of the device was found to be ca. 16% at 410 nm. In order to examine the relationship between the molecular structure of the polymers and their electronic energy levels, and to correlate this with photovoltaic performance, optoelectronic and electrochemical results are discussed in relation to the I‐V characteristics of the devices. Additionally, a computer‐aided simulation is used to gain further insight into the effect of polymer structure on the energetic relationships in the bulk heterojunction devices. 相似文献
129.
Bharat Kumar Ruth L. Viboh Margel C. Bonifacio William B. Thompson Jonathan C. Buttrick Babe C. Westlake Min‐Soo Kim Robert W. Zoellner Sergey A. Varganov Philipp Mrschel Jaroslav Teteruk Martin U. Schmidt Benjamin T. King 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2012,124(51):13071-13071
130.
Andrew J. Thompson Dr. Jerome Dabin Javier Iglesias‐Fernández Dr. Albert Ardèvol Dr. Zoran Dinev Assoc. Prof. Spencer J. Williams Dr. Omprakash Bande Dr. Aloysius Siriwardena Carl Moreland Dr. Ting‐Chou Hu David K. Smith Prof. Harry J. Gilbert Prof. Carme Rovira Prof. Gideon J. Davies 《Angewandte Chemie (International ed. in English)》2012,51(44):11171-11171