全文获取类型
收费全文 | 111236篇 |
免费 | 2833篇 |
国内免费 | 2429篇 |
专业分类
化学 | 48168篇 |
晶体学 | 1270篇 |
力学 | 7785篇 |
综合类 | 152篇 |
数学 | 35090篇 |
物理学 | 24033篇 |
出版年
2023年 | 277篇 |
2022年 | 627篇 |
2021年 | 924篇 |
2020年 | 832篇 |
2019年 | 881篇 |
2018年 | 10971篇 |
2017年 | 10838篇 |
2016年 | 7140篇 |
2015年 | 1976篇 |
2014年 | 1817篇 |
2013年 | 2574篇 |
2012年 | 6412篇 |
2011年 | 13197篇 |
2010年 | 7563篇 |
2009年 | 7792篇 |
2008年 | 9008篇 |
2007年 | 10787篇 |
2006年 | 2386篇 |
2005年 | 3101篇 |
2004年 | 3094篇 |
2003年 | 3252篇 |
2002年 | 2315篇 |
2001年 | 1107篇 |
2000年 | 1003篇 |
1999年 | 669篇 |
1998年 | 547篇 |
1997年 | 447篇 |
1996年 | 562篇 |
1995年 | 371篇 |
1994年 | 336篇 |
1993年 | 358篇 |
1992年 | 252篇 |
1991年 | 248篇 |
1990年 | 208篇 |
1989年 | 196篇 |
1988年 | 144篇 |
1987年 | 154篇 |
1986年 | 126篇 |
1985年 | 143篇 |
1984年 | 107篇 |
1983年 | 87篇 |
1982年 | 110篇 |
1981年 | 107篇 |
1980年 | 83篇 |
1979年 | 94篇 |
1978年 | 84篇 |
1977年 | 56篇 |
1976年 | 62篇 |
1975年 | 55篇 |
1973年 | 60篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
11.
12.
13.
Star copolymers have attracted significant interest due to their different characteristics compared with diblock copolymers, including higher critical micelle concentration, lower viscosity, unique spatial shape, or morphologies. Development of synthetic skills such as anionic polymerization and controlled radical polymerization have made it possible to make diverse architectures of polymers. Depending on the molecular architecture of the copolymer, numerous morphologies are possible, for instance, Archimedean tiling patterns and cylindrical microdomains at symmetric volume fraction for miktoarm star copolymers as well as asymmetric lamellar microdomains for star‐shaped copolymers, which have not been reported for linear block copolymers. In this review, we focus on morphologies and microphase separations of miktoarm (AmBn and ABC miktoarm) star copolymers and star‐shaped [(A‐b‐B)n] copolymers with nonlinear architecture. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1–21 相似文献
14.
15.
16.
Nonlinear Dynamics - In this paper, the current-controlled DC–DC buck converter from a new perspective are studied through the switching theory of flow, and the analytical conditions of the... 相似文献
17.
Young Joo Kim Pil Ho Huh Byung Kyu Kim 《Journal of Polymer Science.Polymer Physics》2015,53(7):468-474
Supramolecular polyurethane ureas are expected to have superior mechanical properties primarily due to the reversible, noncovalent interactions such as hydrogen bonding interactions. We synthesized polyurethane prepolymers from small molecular weight of poly(tetramethylene ether)glycol and isophorone diisocyanates, which were end capped with propylamine to synthesize polyurethane ureas with high contents of urea and urethane groups for hydrogen‐bonding formations to facilitate self‐healing. The effects of polyurethane urea molecular weight (3000 ≤ Mn ≤ 9000), crosslinking, and cutting direction were studied in terms of thermal, mechanical, and morphological properties with an emphasis on the self‐healing efficiency. It was found that the thermal self‐healability was more pronounced as the molecular weight of polyurethane urea decreased, showing a maximum of more than 96% with 3000 Mn when the sample was cut along the stretch direction. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 468–474 相似文献
18.
在管式反应器中采用苯甲酸、聚乙二醇、固体古马隆树脂(S)、液体古马隆树脂(L)为添加剂来降低煤沥青中有害物质苯并芘的含量,以期使得煤沥青可绿色化应用。采用紫外-可见分光光度计分析煤沥青中苯并芘含量。考察了反应温度、反应时间、添加剂添加量、催化剂等工艺条件对添加剂脱除煤沥青中苯并芘的影响。结果表明,不同工艺条件能降低煤沥青中苯并芘的含量。在优化条件下,不同添加剂对苯并芘脱除率由高到低依次为:液体古马隆树脂、聚乙二醇、苯甲酸和固体古马隆树脂。分析其反应机理,这与催化剂的酸性相关,发生亲电取代反应。结果表明,液体古马隆树脂(L)在催化剂存在下对煤沥青中苯并芘脱除率可达73.0%,显示了良好的应用前景。 相似文献
19.
20.
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