全文获取类型
收费全文 | 1405篇 |
免费 | 214篇 |
国内免费 | 354篇 |
专业分类
化学 | 910篇 |
晶体学 | 34篇 |
力学 | 72篇 |
综合类 | 70篇 |
数学 | 242篇 |
物理学 | 645篇 |
出版年
2024年 | 1篇 |
2023年 | 14篇 |
2022年 | 29篇 |
2021年 | 51篇 |
2020年 | 36篇 |
2019年 | 29篇 |
2018年 | 38篇 |
2017年 | 41篇 |
2016年 | 58篇 |
2015年 | 63篇 |
2014年 | 62篇 |
2013年 | 91篇 |
2012年 | 91篇 |
2011年 | 127篇 |
2010年 | 108篇 |
2009年 | 121篇 |
2008年 | 138篇 |
2007年 | 113篇 |
2006年 | 112篇 |
2005年 | 102篇 |
2004年 | 57篇 |
2003年 | 43篇 |
2002年 | 48篇 |
2001年 | 51篇 |
2000年 | 70篇 |
1999年 | 45篇 |
1998年 | 30篇 |
1997年 | 29篇 |
1996年 | 22篇 |
1995年 | 22篇 |
1994年 | 17篇 |
1993年 | 10篇 |
1992年 | 23篇 |
1991年 | 15篇 |
1990年 | 12篇 |
1989年 | 10篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1971年 | 2篇 |
排序方式: 共有1973条查询结果,搜索用时 15 毫秒
31.
系列单取代烷氧基-2-羟丙基-β-环糊精的合成与表征 总被引:1,自引:0,他引:1
以环氧氯丙烷和脂肪醇为原料, 通过相转移催化法合成了乙基、正丙基、正丁基和正戊基缩水甘油醚(1~4), 并利用所合成的缩水甘油醚和β-环糊精为原料, 分别在弱碱水溶液(1.5%)和强碱水溶液(30%)中制备并用硅胶柱分离出单2位取代的乙氧基、丙氧基、丁氧基和戊氧基-2-羟丙基-β-环糊精(1a~4a)和单6位取代的丙氧基、丁氧基和戊氧基-2-羟丙基-β-环糊精(2b~4b), 利用薄层色谱、红外光谱、差热扫描量热分析、质谱和核磁共振等手段对所合成的产品进行了表征. 相似文献
32.
DL-苹果酸-丙酮-BrO~3^--Mn^2^+-H~2SO~4化学振荡 反应诱导期的新特征 及其动力学研究 总被引:1,自引:0,他引:1
在前文研究工作的基础上,较详细地研究了DL-苹果酸(以下简称DL-MA)、丙酮(以下简称Act)参与下的新型化学振荡反应及各种影响因素,对各主要参与反应物质在诱导期中的作用、起振原因、诱导期的新特征和可能反应机理进行了较为深入的研究,分别获得DL-MA,KBrO~3,MnSO~4的浓度对诱导期影响的拟合方程。以及诱导期的表观活化参数为E~I~N=68.50kJ·mol^-^1。 相似文献
33.
34.
采用物理涂附法将单链DNA固定到金表面得到ssDNA/Au修饰电极。研究表明,该电极在pH 5,0.2 mol/L NaAc-HAc缓冲底液中,可用于测定水中痕量Pb2 。Pb2 以Pb-DNA络合物的形式吸附在电极上,以示差脉冲伏安法测定Pb2 ,在0.15 V(vsSCE)处有灵敏的氧化峰,其峰电流与Pb2 浓度在5.0×10-8~1.0×10-6mol/L范围内呈良好的线性关系,此法的检测限为2.0×10-8mol/L,该修饰电极的稳定性和抗干扰性都较好。用该电极对饮用水中的Pb进行检测,得到了满意的结果。 相似文献
35.
目的探讨了江苏省疾控[2009]97号文件附录A《面制品及海蜇中铝的测定方法》测定面制食品中铝含量。方法样品经干法消化后,在乙二胺-盐酸缓冲溶液中,三价铝在十六烷基三甲基溴化铵阳离子表面活性剂存在下,与铬天青S形成绿色三元体系,其吸光度与铝的含量在一定含量范围内成正比。结果样品消化液在定容30 min时测定结果接近中位值,方法线性系数r=0.999 7,相对标准偏差在3.3%~3.7%之间,样品回收率在88.9%~96.4%。结论该法操作简便,灵敏度高,适用于各实验室开展检测。 相似文献
36.
Hongxia Guo Yuechun Qiao Guohua Liu Jingqing Gao 《Russian Journal of Electrochemistry》2013,49(4):396-399
Single-phased nanosized LiFePO4 with thinner thickness along [010] crystallographic direction were successfully fabricated under solvothermal condition by using glycerol as co-solvent. The as-obtained product with thinner thickness is beneficial for fast migration of Li ions in the olivine-structured LiFePO4, hence exhibiting excellent electrochemical performance. 相似文献
37.
Chao Zuo Qian Chen Guohua Gu Xiubao Sui Jianle Ren 《Infrared Physics & Technology》2012,55(4):263-269
In this paper, an improved interframe registration based nonuniformity correction algorithm for focal plane arrays is proposed. The method simultaneously estimates detector parameters and carries out the nonuniformity correction by minimizing the mean square error between the two properly registered image frames. A new masked phase correlation algorithm is introduced to obtain reliable shift estimates in the presence of fixed pattern noise. The use of an outliers exclusion scheme, together with a variable step size strategy, could not only promote the correction precision considerably, but also eliminate ghosting artifacts effectively. The performance of the proposed algorithm is evaluated with clean infrared image sequences with simulated nonuniformity and real pattern noise. We also apply the method to a real-time imaging system to show how effective it is in reducing noise and the ghosting artifacts. 相似文献
38.
In this paper, compressive imaging based on spatial correlation (CISC), which uses second-order correlation with the measurement matrix, is introduced to improve the signal-to-noise ratio performance of compressive imaging (CI). Numerical simulations and experiments are performed as well. Referred to the results, it can be seen that CISC performs much better than CI in three common noise environments. This provides the great opportunity to pave the way for real applications. 相似文献
39.
Dual‐responsive supramolecular self‐assembly of inclusion complex of an azobenzene‐ended poly(ε‐caprolactone) with a water‐soluble pillar[6]arene and its application in controlled drug release
下载免费PDF全文
![点击此处可从《Journal of polymer science. Part A, Polymer chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Zaizai Tong Junyi Zhou Runsheng Huang Jie Zhou Runke Zhang Wangqian Zhuo Guohua Jiang 《Journal of polymer science. Part A, Polymer chemistry》2017,55(15):2477-2482
Dual photo‐ and pH‐responsive polymeric vesicles are constructed from a host–guest complex between a water‐soluble pillar[6]arene and an azobenzene ended functionalized poly(ε‐caprolactone). Reversible morphological transitions between vesicles and solid aggregates are achieved upon repeated UV stimulus and pH stimulus. Moreover, the polymeric vesicles present excellent cytocompatibility toward HepG2 cells and can be further applied for controlled release of a hydrophilic model drug, DOX?HCl. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 2477–2482 相似文献
40.
Dr. Lihui Chen Haifeng Hu Yuzhou Chen Yuan Li Prof. Jing Gao Prof. Guohua Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(3):1057-1065
For plasmonic copper-deficient Cu2−xS nanoparticles (NPs), accurate control of the crystal phase and morphology is highly desirable as both of which are known to determine the localized surface plasmon resonance (LSPR) wavelength and amplitude. Here, how the sulfur precursor reactivity in the synthesis of Cu2−xS NPs affects the resulting crystal phase and morphology is examined. Djurleite Cu1.94S, roxbyite Cu1.8S, digenite Cu1.8S as well as covellite CuS nanodisks were synthesized by using 1-dodecanethiol, N,N-dibutylthiourea, and crystal sulfur 1-octadecene/oleylamine solutions and their crystal phase dependent LSPR properties were exhaustively discussed. In addition, crystal phase interconversion between covellite CuS and djurleite/roxbyite Cu2−xS was realized in the presence of the above sulfur precursors. On the other hand, djurleite Cu1.94S nanorods rather than nanodisks were prepared by replacing 1-dodecanethiol with more reactive tert-dodecanethiol. The structural and morphological Cu2−xS NPs here holds great promise in the application of photothermal therapy, photocatalysis, surface-enhanced Raman scattering (SERS), and many others. 相似文献