全文获取类型
收费全文 | 14088篇 |
免费 | 2060篇 |
国内免费 | 1444篇 |
专业分类
化学 | 4830篇 |
晶体学 | 111篇 |
力学 | 1047篇 |
综合类 | 284篇 |
数学 | 5301篇 |
物理学 | 6019篇 |
出版年
2024年 | 17篇 |
2023年 | 119篇 |
2022年 | 376篇 |
2021年 | 388篇 |
2020年 | 398篇 |
2019年 | 326篇 |
2018年 | 353篇 |
2017年 | 446篇 |
2016年 | 496篇 |
2015年 | 408篇 |
2014年 | 705篇 |
2013年 | 1058篇 |
2012年 | 774篇 |
2011年 | 862篇 |
2010年 | 729篇 |
2009年 | 885篇 |
2008年 | 963篇 |
2007年 | 975篇 |
2006年 | 823篇 |
2005年 | 777篇 |
2004年 | 644篇 |
2003年 | 622篇 |
2002年 | 600篇 |
2001年 | 454篇 |
2000年 | 425篇 |
1999年 | 388篇 |
1998年 | 392篇 |
1997年 | 296篇 |
1996年 | 258篇 |
1995年 | 210篇 |
1994年 | 220篇 |
1993年 | 139篇 |
1992年 | 136篇 |
1991年 | 117篇 |
1990年 | 79篇 |
1989年 | 90篇 |
1988年 | 78篇 |
1987年 | 73篇 |
1986年 | 52篇 |
1985年 | 82篇 |
1984年 | 57篇 |
1983年 | 36篇 |
1982年 | 53篇 |
1981年 | 25篇 |
1980年 | 27篇 |
1979年 | 31篇 |
1978年 | 35篇 |
1977年 | 23篇 |
1976年 | 20篇 |
1973年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
Thierry Pigot 《Tetrahedron letters》2004,45(21):4047-4050
A new mixed organic-inorganic photosensitizer, based on 4-benzoylbenzoate intercalated into a layered double hydroxide has been prepared, characterized and successfully tested for the photo-oxidation of dialkylsulfides, both in acetonitrile and in the gas phase. 相似文献
43.
44.
Most of the methods used in the ARCH literature for selecting the appropriate model are based on evaluating the ability of the models to describe the data. An alternative model selection approach is examined based on the evaluation of the predictability of the models in terms of standardized prediction errors. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
45.
本文考虑广义C-R组^[1](H)的解f=u iv jw∈C^2的一些性质,提出与之相关的两个边值问题,用积分方程方法和调和函数性质证明了边值问题解的存在唯一性,并写出解的积分表达式. 相似文献
46.
为阐述放射性9C束流应用于治癌的物理基础, 运用一个球形生物组织等效正比计数器测量了9C束流不同贯穿深度上的线能谱, 得到了沿束流贯穿深度上的剂量平均线能分布. 将实验测量得到的线能谱转换成为不同传能线密度在吸收剂量中所占份额的分布, 得到了该9C束流在不同贯穿深度上的剂量平均传能线密度分布. 将生物组织等效正比计数器测量得到的与先前通过平行板正比计数器测量得到的该9C束流的剂量平均传能线密度分布进行比较, 发现: 在束流入射通道上, 两者测量数据符合很好, 而在束流Bragg峰附近9C离子的沉积区域, 由组织等效正比计数器测量得到的剂量平均传能线密度值大于由平行板正比计数器测量得到的值. 相似文献
47.
48.
49.
The UV-blue thermoluminescence (TL) emission of exsolved and twinned potassium feldspars is potentially valid to be employed in the field of dating and retrospective dosimetry. This paper reports about the following results: (i) The dose dependence of the 400 nm TL intensity of a K-rich feldspar exhibits an excellent linearity in the range of 50 mGy–8 Gy. (ii) The stability of the TL signal after 6 months of storage, shows an initial rapid decay (ca. 45%) maintaining the stability from 40 days onwards which indicates that the electron population decreases asymptotically by the X-axis and the involved electrons are located in deeper traps at room temperature. The fading process can be fitted to a first-order decay equation of the sort y=y0+A exp(−x/t). (iii) The tests of thermal stability at different temperatures confirm a continuous trap distribution with progressive changes in the glow curve shape, intensity and temperature position of the maximum peak. According to this behaviour some physical parameters are defined. 相似文献
50.
Anna Finne Ann-Christine Albertsson 《Journal of polymer science. Part A, Polymer chemistry》2004,42(3):444-452
Following our continued interest in the production of bioerodible and biodegradable functional polymers for biomedical applications, we synthesized and characterized new unsaturated polyesters. The presence of functional groups in the polymer backbone provided sites for chemical modification, and through a variation in the structure, the physical properties, such as the hydrophilicity and solubility, could be affected. With 1,1-di-n-butyl-stanna-2,7-dioxacyclo-4-heptene as the initiator in the ring-opening polymerization of polyesters, a new set of functionalized polyesters was created. The polymerization of ϵ-caprolactone resulted in poly(ϵ-caprolactone) with a double bond incorporated into the structure. The polymers were obtained in a controlled manner with low molecular dispersities. The double bond was previously incorporated into L -lactide polymers, and the two reactions were compared in this study. The conversion of ϵ-caprolactone, with a degree of polymerization of 50, was completed within 140 min, whereas for L -lactide, only a 45% conversion took place in the same period of time. The dispersities were somewhat higher with ϵ-caprolactone because of the higher reaction rate and, therefore, lower selectivity. The incorporated CC double bond in the polyesters provided a variety of opportunities for further modifications. In this case, the double bond of the L -lactide macromonomers was oxidized into epoxides. Epoxidation was carried out with m-chloroperoxybenzoic acid as a chemical reagent. The conversion of the double bonds into epoxides was completed, and the obtained yields were good (>95%). As a result of the mild reaction conditions, the epoxidation of the double bond was carried out quantitatively without any side reactions. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 444–452, 2004 相似文献