全文获取类型
收费全文 | 5245篇 |
免费 | 1103篇 |
国内免费 | 390篇 |
专业分类
化学 | 1578篇 |
晶体学 | 29篇 |
力学 | 491篇 |
综合类 | 87篇 |
数学 | 725篇 |
物理学 | 3828篇 |
出版年
2024年 | 7篇 |
2023年 | 53篇 |
2022年 | 132篇 |
2021年 | 99篇 |
2020年 | 107篇 |
2019年 | 106篇 |
2018年 | 141篇 |
2017年 | 229篇 |
2016年 | 248篇 |
2015年 | 215篇 |
2014年 | 436篇 |
2013年 | 367篇 |
2012年 | 367篇 |
2011年 | 467篇 |
2010年 | 353篇 |
2009年 | 343篇 |
2008年 | 370篇 |
2007年 | 388篇 |
2006年 | 320篇 |
2005年 | 317篇 |
2004年 | 235篇 |
2003年 | 223篇 |
2002年 | 164篇 |
2001年 | 146篇 |
2000年 | 139篇 |
1999年 | 115篇 |
1998年 | 96篇 |
1997年 | 88篇 |
1996年 | 69篇 |
1995年 | 83篇 |
1994年 | 59篇 |
1993年 | 36篇 |
1992年 | 43篇 |
1991年 | 39篇 |
1990年 | 29篇 |
1989年 | 21篇 |
1988年 | 20篇 |
1987年 | 17篇 |
1986年 | 12篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1978年 | 3篇 |
1974年 | 2篇 |
1968年 | 1篇 |
1966年 | 2篇 |
1959年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有6738条查询结果,搜索用时 15 毫秒
61.
62.
63.
R. Rehm M. Walther J. Schmitz J. Fleißner F. Fuchs J. Ziegler W. Cabanski 《Opto-Electronics Review》2006,14(1):19-24
The first fully operational mid-IR (3–5 μm) 256×256 IR-FPA camera system based on a type-II InAs/GaSb short-period superlattice
showing an excellent noise equivalent temperature difference below 10 mK and a very uniform performance has been realized.
We report on the development and fabrication of the detecor chip, i.e., epitaxy, processing technology and electro-optical
characterization of fully integrated InAs/GaSb superlattice focal plane arrays. While the superlattice design employed for
the first demonstrator camera yielded a quantum efficiency around 30%, a superlattice structure grown with a thicker active
layer and an optimized V/III BEP ratio during growth of the InAs layers exhibits a significant increase in quantum efficiency.
Quantitative responsivity measurements reveal a quantum efficiency of about 60% for InAs/GaSb superlattice focal plane arrays
after implementing this design improvement.
The paper presented there appears in Infrared Photoelectronics, edited by Antoni Rogalski, Eustace L. Dereniak, Fiodor F. Sizov, Proc. SPIE Vol. 5957, 595707 (2005). 相似文献
64.
提出了一种非刚性点匹配的算法并把其运用于医学图像配准.该算法采用信号滤波的方法来获得点集间的匹配信息,并运用松弛标记法将各点邻域关系对模糊的匹配信息进行迭代获得明确的匹配关系.在此基础上,利用高斯径向基函数来描述点模式间的弹性形变,在基本的迭代框架下实现问题的求解.实验结果显示在形变程度为5%、出格点比率50%和噪声标准差为5%的情况下该算法的匹配误差能控制在0.13以下,表明了该算法的鲁棒性和有效性,较好地解决了医学非刚性形变的点匹配问题. 相似文献
65.
Fumie Takei Daisuke Kodama Sugiko Nakamura Kiyotaka Onitsuka Shigetoshi Takahashi 《Journal of polymer science. Part A, Polymer chemistry》2006,44(1):585-595
Aryl isocyanides bearing free‐base and metallo‐porphyrins were prepared and polymerized with a Pd–Pt μ‐ethynediyl complex as the initiator to give polymers with narrow polydispersity indices. The molecular weights of the resulting polymers were precisely controlled by the initial feed ratio of the porphyrin monomer to the initiator. The UV–VIS spectra suggested that the porphyrin pendants are regularly arranged to form stacked columns. Metallo‐porphyrin polymers were also prepared by reacting free‐base porphyrin polymers with metal salts. The successive reactions of free‐base and zinc‐porphyrin monomers resulted in the formation of diblock polymers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 585–595, 2006 相似文献
66.
Ryosuke Sakai Issei Otsuka Toshifumi Satoh Ryohei Kakuchi Harumi Kaga Toyoji Kakuchi 《Journal of polymer science. Part A, Polymer chemistry》2006,44(1):325-334
The asymmetric polymerization of 4′‐isocyanatobenzo‐18‐crown‐6 with the lithium amide of (S)‐(2‐methoxymethyl)pyrrolidine successfully proceeded to afford end‐functionalized poly(4′‐isocyanatobenzo‐18‐crown‐6) with (S)‐(2‐methoxymethyl)pyrrolidine (polymer 2 ). In the circular dichroism (CD) spectrum of 2 , a clear positive Cotton effect was observed in the range of 240–350 nm corresponding to the absorption of the polymer backbone, indicating that 2 partially formed a one‐handed helical structure, which was preserved by the chirality of (S)‐(2‐methoxymethyl)pyrrolidine bonding to the terminal end in 2 . In the titration experiments for the CD intensity of 2 in the presence of D ‐ and L ‐Phe·HClO4 (where Phe is phenylalanine), a small but remarkable difference was observed in the amount of the chiral guest needed for saturation of the CD intensity and in the saturated CD intensity, indicating that the extremely stable, one‐handed helical part should exist in the main chain of 2 , which was not inverted even when the unfavorable chiral guest for the predominant helical sense, L ‐Phe·HClO4, was added. In addition, helical polymer 2 exhibited a chiral discrimination ability toward racemic guests; that is, the guests were extracted from the aqueous phase into the organic phase with enantiomeric excess. The driving force of the chiral discrimination ability of 2 should certainly be attributed to the one‐handed helical structure in 2 . © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 325–334, 2006 相似文献
67.
68.
我们用X射线荧光光谱滤纸片法分析了古今13铜矿石样品中的铜含量,测量结果与化学法一致。此法不需要铜矿石的标样,而且手续简单,方便,检出限低,灵敏度高,测量结果正确可靠,是分析矿石中单一或几个元素的含量较好的方法之一。 相似文献
70.