全文获取类型
收费全文 | 99012篇 |
免费 | 5740篇 |
国内免费 | 4647篇 |
专业分类
化学 | 56413篇 |
晶体学 | 1334篇 |
力学 | 5592篇 |
综合类 | 325篇 |
数学 | 11881篇 |
物理学 | 33854篇 |
出版年
2023年 | 753篇 |
2022年 | 1720篇 |
2021年 | 2059篇 |
2020年 | 2325篇 |
2019年 | 2520篇 |
2018年 | 2903篇 |
2017年 | 2834篇 |
2016年 | 3506篇 |
2015年 | 2415篇 |
2014年 | 3499篇 |
2013年 | 4934篇 |
2012年 | 5081篇 |
2011年 | 5372篇 |
2010年 | 4258篇 |
2009年 | 4270篇 |
2008年 | 4465篇 |
2007年 | 4189篇 |
2006年 | 3820篇 |
2005年 | 3392篇 |
2004年 | 3051篇 |
2003年 | 2715篇 |
2002年 | 2831篇 |
2001年 | 2548篇 |
2000年 | 1994篇 |
1999年 | 1610篇 |
1998年 | 1545篇 |
1997年 | 1337篇 |
1996年 | 1299篇 |
1995年 | 1080篇 |
1994年 | 1159篇 |
1993年 | 1098篇 |
1992年 | 1062篇 |
1991年 | 1124篇 |
1990年 | 1119篇 |
1989年 | 1040篇 |
1988年 | 917篇 |
1987年 | 914篇 |
1986年 | 881篇 |
1985年 | 921篇 |
1984年 | 915篇 |
1983年 | 822篇 |
1982年 | 800篇 |
1979年 | 801篇 |
1978年 | 812篇 |
1977年 | 806篇 |
1976年 | 919篇 |
1975年 | 812篇 |
1974年 | 844篇 |
1973年 | 847篇 |
1972年 | 752篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
901.
902.
The fourth-order ordinary differential equation that defines the self-similar solutions of the Kaup—Kupershmidt and Sawada—Kotera
equations is studied. This equation belongs to the class of fourth-order analogues of the Painlevé equations. All the power
and non-power asymptotic forms and expansions near points z = 0, z = ∞ and near an arbitrary point z = z
0 are found by means of power geometry methods. The exponential additions to the solutions of the studied equation are also
determined.
相似文献
903.
904.
905.
R. I. Jalmakhanbetova V. A. Raldugin I. Yu. Bagryanskaya Yu. V. Gatilov M. M. Shakirov G. A. Atazhanova S. M. Adekenov 《Chemistry of Natural Compounds》2007,43(5):552-554
Adducts of dihalocarbenes generated from chloroform and bromoform were prepared by reaction with estafiatin guaianolide. Their
structures were established by XSA.
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 453–455, September–October, 2007. 相似文献
906.
Tumor cells transduced with herpes simplex virus thymidine kinase gene have been intensively applied to the field of positron emission tomography via imaging of its substrate. As a pilot synthesis approach, a facile preparation of 5‐[125I] iodoarabinosyl uridine starting from commercially available uridine is reported herein. 相似文献
907.
I. L. Valuev Yu. A. Talyzenkov I. V. Obydennova L. I. Valuev N. A. Platé 《Polymer Science Series B》2007,49(5-6):148-151
N,N-Diethylacrylamide-N-acryloylphthalimide copolymers have been synthesized. The LCST of the synthesized copolymers decreases with increase in both the molecular mass of the copolymers and the content of more hydrophobic N-acryloylphthalimide units. Through the reaction of the copolymers with the proteinase enzyme inhibitor, ovomucoid, the polymer derivatives of protein have been prepared. It has been shown that the biological activity of ovomucoid and the LCST of polymer derivatives increase with the amount of the immobilized ovomucoid. The effect of biologically active media on the LCST values of polymer derivatives has been studied. 相似文献
908.
909.
910.
Kan‐Yi Pu Yi Chen Xiao‐Ying Qi Chun‐Yang Qin Qing‐Quan Chen Hong‐Yu Wang Yun Deng Qu‐Li Fan Yan‐Qin Huang Shu‐Juan Liu Wei Wei Bo Peng Wei Huang 《Journal of polymer science. Part A, Polymer chemistry》2007,45(16):3776-3787
In this contribution, we demonstrate a new effective methodology for constructing highly efficient and durable poly(p‐phenyleneethynylene) (PPE) containing emissive material with nonaggregating and hole‐facilitating properties through the introduction of hole‐transporting blocks into the PPE system as the grafting coils as well as building the energy donor–acceptor architecture between the grafting coils and the PPE backbone. Poly(2‐(carbazol‐9‐yl)ethyl methacrylate) (PCzEMA), herein, is chosen as the hole‐transporting blocks, and incorporated into the PPE system as the grafting coils via atom transfer radical polymerization. The chemical structure of the resultant copolymer, PPE‐g‐PCzEMA, was characterized by NMR and gel permeation chromatography, showing that the desirable copolymer was obtained with the narrow polydispersity. The increased thermal stability of PPE‐g‐PCzEMA was confirmed by thermogravimetric analysis and differential scanning calorimetry along with its macroinitiator. The optoelectronic properties of this copolymer were studied in detail by ultraviolet‐visible absorption, photoluminescence emission and excitation spectra, and cyclic voltammogram (CV). The results indicate that PPE‐g‐PCzEMA exhibits the solid‐state luminescent property dominated by individual lumophores, and also the energy transfer process from the PCzEMA blocks to the PPE backbone with a relatively higher energy transfer efficiency in the solid‐state compared to that of the solution state. Additionally, the hole‐injection property is greatly facilitated due to the presence of PCzEMA, as confirmed by CV profiles. All these data indicate that PPE‐g‐PCzEMA is a good candidate for use in optoelectronic devices. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3776–3787, 2007 相似文献