全文获取类型
收费全文 | 131998篇 |
免费 | 14506篇 |
国内免费 | 6094篇 |
专业分类
化学 | 94076篇 |
晶体学 | 1630篇 |
力学 | 6092篇 |
综合类 | 367篇 |
数学 | 14090篇 |
物理学 | 36343篇 |
出版年
2023年 | 775篇 |
2022年 | 1590篇 |
2021年 | 2197篇 |
2020年 | 3431篇 |
2019年 | 4824篇 |
2018年 | 3817篇 |
2017年 | 3471篇 |
2016年 | 6606篇 |
2015年 | 5647篇 |
2014年 | 6678篇 |
2013年 | 8706篇 |
2012年 | 7840篇 |
2011年 | 7474篇 |
2010年 | 6954篇 |
2009年 | 6948篇 |
2008年 | 6707篇 |
2007年 | 5840篇 |
2006年 | 5192篇 |
2005年 | 4909篇 |
2004年 | 4357篇 |
2003年 | 3947篇 |
2002年 | 4763篇 |
2001年 | 3901篇 |
2000年 | 3231篇 |
1999年 | 1985篇 |
1998年 | 1619篇 |
1997年 | 1388篇 |
1996年 | 1325篇 |
1995年 | 1119篇 |
1994年 | 1204篇 |
1993年 | 1129篇 |
1992年 | 1093篇 |
1991年 | 1164篇 |
1990年 | 1144篇 |
1989年 | 1055篇 |
1988年 | 932篇 |
1987年 | 926篇 |
1986年 | 890篇 |
1985年 | 936篇 |
1984年 | 923篇 |
1983年 | 828篇 |
1982年 | 806篇 |
1979年 | 807篇 |
1978年 | 817篇 |
1977年 | 811篇 |
1976年 | 922篇 |
1975年 | 815篇 |
1974年 | 846篇 |
1973年 | 849篇 |
1972年 | 753篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
Yu. V. Pokonova 《Russian Journal of Applied Chemistry》2007,80(11):1964-1968
Advantage of use residue from thermal cracking and products of its condensation as components of the mixture for manufacturing mechanically rigid (93%) granulated and ground carbon sorbents with extended volume of micropores (up to 0.27 cm3/cm3), showing enhanced sorption activity (E is up to 25.6 kJ mol?1) and high ability of separation various gas mixtures is demonstrated. As a carrier for medicine preparations these adsorbents show higher performance as compared with industrial samples. Solutions of the cracking residue can be used for impregnation of worked out zeolites for petroleum technology and for production of organomineral adsorbents with high adsorption capacity on extraction mercury from sewages. 相似文献
942.
Yu. G. Tselishchev 《Colloid Journal》2007,69(4):537-539
The capillary pressure in a liquid interlayer between two spherical particles is calculated as a function of their sizes and the wetting properties of the liquid. 相似文献
943.
Reaction of diethoxyphosphorylimine of methyl trifluoropyruvate with 1,3-C,N-and-N,N-binucleophiles led to a variety of N-phosphorylated fluorine-containing heterocycles, including the fused ones.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2176–2178, November, 2007. 相似文献
944.
The crystallization behavior of miscible syndiotactic polystyrene (sPS) and atactic polystyrene (aPS) blends with different sPS/aPS weight ratios was investigated in supercritical CO2 by using Fourier‐transform infrared spectroscopy, differential scanning calorimetry, and wide‐angle X‐ray diffraction. Supercritical CO2 and aPS exhibited different effects on the conformational change of sPS and competed with each other. Increasing the content of amorphous aPS in the blends made its effect on the conformational change of sPS gradually surpass that of supercritical CO2. Supercritical CO2 favored the formation of the helical conformation of sPS in lower temperature range and the all trans planar conformation in higher temperature range, instead of forming the latter one only in higher temperature range in ambient atmosphere. However, increasing aPS content in the blends pushed the range for forming the helical conformation to lower temperature and made the all trans planar conformation dominant in aPS/sPS 25/75 blend after treating in supercritical CO2 above 60 °C. The all trans planar zigzag conformation was more favorable than the helical conformation after mixing aPS in sPS in supercritical CO2. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1755–1764, 2007 相似文献
945.
Fengping Yu Junpo He Xiaojun Wang Guangzheng Gao Yuliang Yang 《Journal of polymer science. Part A, Polymer chemistry》2007,45(17):4013-4025
A combination of nitroxide‐mediated radical polymerization and living anionic polymerization was used to synthesize a series of well‐defined graft (co)polymers with “V‐shaped” and “Y‐shaped” branches. The polymer main chain is a copolymer of styrene and p‐chloromethylstyrene (PS‐co‐PCMS) prepared via nitroxide‐mediated radical polymerization. The V‐shaped branches were prepared through coupling reaction of polystyrene macromonomer, carrying 1,1‐diphenylethylene terminus, with polystyryllithium or polyisoprenyllithium. The Y‐shaped branches were prepared throughfurther polymerization initiated by the V‐shaped anions. The obtained branches, carrying a living anion at the middle (V‐shaped) or at the end of the third segment (Y‐shaped), were coupled in situ with pendent benzyl chloride of PS‐co‐PCMS to form the target graft (co)polymers. The purified graft (co)polymers were analyzed by size exclusion chromatography equipped with a multiangle light scattering detector and a viscometer. The result shows that the viscosities and radii of gyration of the branched polymers are remarkably smaller than those of linear polystyrene. In addition, V‐shaped product adopts a more compact conformation in dilute solution than the Y‐shaped analogy. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4013–4025, 2007 相似文献
946.
Kuan‐Wei Lee Hong‐Cheu Lin 《Journal of polymer science. Part A, Polymer chemistry》2007,45(20):4564-4572
A series of new liquid crystalline homopolymers, copolymers, and block copolymers were polymerized from styrene‐macroinitiator ( SMi ) and methacrylates with pendent 4,4′‐bis(biphenyl)fluorene ( M1 ) and biphenyl‐4‐ylfluorene ( M2 ) groups through atom transfer radical polymerization (ATRP). The number‐average molecular weights (Mn) of polymers P1 ‐ P4 were 10,007, 14,852, 6,275, and 10,463 g mol?1 with polydispersity indices values of 1.21, 1.15, 1.31, and 1.22, respectively. All polymers exhibit the nematic phase. The thermal, mesogenic, and photoluminescent properties of all polymers were investigated. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4564–4572, 2007 相似文献
947.
948.
Nathalie Charton Achim Feldermann Alexander Theis Martina H. Stenzel Thomas P. Davis Christopher Barner‐Kowollik 《Journal of polymer science. Part A, Polymer chemistry》2004,42(21):5559-5559
The original article to which this Erratum refers was published in J Polym Sci Part A: Polym Chem (2004) 42(20) 5170–5179. No abstract. 相似文献
949.
Violetta Patroniak Wanda Radecka‐Paryzek Maciej Kubicki 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(9):o511-o513
The structure of a trifluoromethanesulfonate salt of a nontypical triply protonated linear tetramine, C7H23N43+·3CF3SO3−, with a layered crystal structure is presented. One N atom remains unprotonated. The conformation of the cation is enforced by intra‐ and intermolecular hydrogen bonds. The crystal structure is built of ca 10 Å deep layers, within which cations and anions are hydrogen bonded. Each layer is only weakly bound to its neighbours. This study shows a rare example of an unsymmetrically protonated polyamine and the relation between the lack of protonation, intramolecular hydrogen bonding and the conformation of the cation. 相似文献
950.
V. I. Burkov E. P. Peredereĭ E. V. Fedotov B. V. Mill’ Yu. V. Pisarevskiĭ 《Crystallography Reports》2008,53(5):843-846
The absorption and circular dichroism spectra of langasite family crystals are studied. Wide bands in the range of 285–500 nm that are related to the structure lattice defects are found. For all the crystals, these bands are in approximately the same spectral region, have identical structures, and can be attributed to one type of defects formed by cation vacancies and excess oxygen atoms in the optically active positions. 相似文献