全文获取类型
收费全文 | 84990篇 |
免费 | 502篇 |
国内免费 | 395篇 |
专业分类
化学 | 29156篇 |
晶体学 | 799篇 |
力学 | 6793篇 |
数学 | 33133篇 |
物理学 | 16006篇 |
出版年
2020年 | 65篇 |
2018年 | 10454篇 |
2017年 | 10287篇 |
2016年 | 6183篇 |
2015年 | 953篇 |
2014年 | 399篇 |
2013年 | 517篇 |
2012年 | 3972篇 |
2011年 | 10722篇 |
2010年 | 5772篇 |
2009年 | 6201篇 |
2008年 | 6796篇 |
2007年 | 8965篇 |
2006年 | 464篇 |
2005年 | 1501篇 |
2004年 | 1737篇 |
2003年 | 2121篇 |
2002年 | 1208篇 |
2001年 | 356篇 |
2000年 | 423篇 |
1999年 | 265篇 |
1998年 | 305篇 |
1997年 | 232篇 |
1996年 | 268篇 |
1995年 | 218篇 |
1994年 | 181篇 |
1993年 | 204篇 |
1992年 | 156篇 |
1991年 | 164篇 |
1990年 | 150篇 |
1989年 | 193篇 |
1988年 | 159篇 |
1987年 | 163篇 |
1986年 | 160篇 |
1985年 | 191篇 |
1984年 | 154篇 |
1983年 | 137篇 |
1982年 | 146篇 |
1981年 | 131篇 |
1980年 | 155篇 |
1979年 | 157篇 |
1978年 | 153篇 |
1977年 | 154篇 |
1976年 | 116篇 |
1975年 | 93篇 |
1974年 | 82篇 |
1973年 | 97篇 |
1972年 | 68篇 |
1971年 | 68篇 |
1967年 | 122篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
S. V. Panin I. V. Vlasov V. P. Sergeev B. B. Ovechkin P. O. Marushchak Sunder Ramasubbu P. S. Lyubutin V. V. Titkov 《Physical Mesomechanics》2015,18(3):261-272
The structure and properties of 12Cr1MoV steel irradiated with a zirconium ion beam were studied by optical microscopy, scanning electron microscopy, and micro- and nanoindentation. It is shown that the modification covers the entire cross-section of the irradiated specimens to a depth of 1 mm. The data on irradiation-induced structural changes are used to interpret the changes in mechanical properties of the irradiated specimens under static and cyclic loading. Particular attention is given to analysis of strain estimation by the digital image correlation method. 相似文献
12.
He Haidong Yang Haifeng Zhou Longpeng Chen Tianchi 《Journal of Russian Laser Research》2015,36(3):292-299
Ni–Co alloys have a wide range of applications in various fields owning to their excellent physical, chemical, and mechanical properties. In this paper, we prepare Ni–Co alloy coatings on 316L stain steel surfaces by electroplating. We present a novel approach utilizing a nanosecond laser to induce microtextures on Ni–Co alloy coatings. We study experimentally the effects of laser power and scanning rate on the surface morphologies of Ni–Co alloy coatings. The results indicate that the shape and size of induced microtextures can be controlled by the laser power and scanning rate. The size of grains increases with increase in the work current of the laser (WCL) at a certain scanning rate. With the WCL constant, the size of grains decreases with increase in scanning rate while their average height increases. It is a simple and easily-controlled method for the fabrication of microstructures on Ni–Co alloy coatings, which has promising applications in investigations of the properties of microtextured surfaces, such as friction, adhesion, and wetting. 相似文献
13.
14.
15.
16.
Zenon Moszner 《Aequationes Mathematicae》2018,92(4):617-625
We give the form of the output function in Ginsburg’s machine in which the input and output dictionaries are abelian groups and the transition function is of a special form. 相似文献
17.
18.
Robin F. Weitkamp Beate Neumann Hans‐Georg Stammler Berthold Hoge 《Angewandte Chemie (International ed. in English)》2020,59(14):5494-5499
We report on the first examples of isolated silanol–silanolate anions, obtained by utilizing weakly coordinating phosphazenium counterions. The silanolate anions were synthesized from the recently published phosphazenium hydroxide hydrate salt with siloxanes. The silanol–silanolate anions are postulated intermediates in the hydroxide‐mediated polymerization of aryl and alkyl siloxanes. The silanolate anions are strong nucleophiles because of the weakly coordinating character of the phosphazenium cation, which is perceptible in their activity in polysiloxane depolymerization. 相似文献
19.
20.
Daniel Heinz Annette Meister Hazrat Hussain Karsten Busse Jörg Kressler 《Journal of polymer science. Part A, Polymer chemistry》2020,58(23):3322-3335
Adding perfluoroalkyl (PF) segments to amphiphilic copolymers yields triphilic copolymers with new application profiles. Usually, PF segments are attached as terminal blocks via Cu(I) catalyzed azide-alkyne cycloaddition (CuAAC). The purpose of the current study is to design new triphilic architectures with a PF segment in central position. The PF segment bearing bifunctional atom transfer radical polymerization (ATRP) initiator is employed for the fabrication of triphilic poly(propylene oxide)-b-poly(glycerol monomethacrylate)-b-PF-b-poly(glycerol monomethacrylate)-b-poly(propylene oxide) PPO-b-PGMA-b-PF-b-PGMA-b-PPO pentablock copolymers by a combined ATRP and CuAAC reaction approach. Differential scanning calorimetry indicates the PF-initiator to undergo a solid–solid phase transition at 63°C before the final crystal melting at 95°C. This is further corroborated by polarized optical microscopy and X-ray diffraction studies. The PF-initiator could successfully polymerize solketal methacrylate (SMA) under typical ATRP conditions producing well-defined Br-PSMA-b-PF-b-PSMA-Br triblock copolymers that are then converted into PPO-b-PSMA-b-PF-b-PSMA-b-PPO pentablock copolymer via CuAAC reaction. Subsequently, acid hydrolysis of the PSMA blocks afforded water soluble well-defined triphilic pentablock copolymers PPO-b-PGMA-b-PF-b-PGMA-b-PPO with fluorophilic central segment, hydrophilic middle blocks, and lipophilic outer blocks. The triphilic block copolymers could self-assemble, depending upon the preparatory protocol, into spherical and filament-like phase-separated nanostructures as revealed by transmission electron microscopy. 相似文献