全文获取类型
收费全文 | 267篇 |
免费 | 44篇 |
国内免费 | 42篇 |
专业分类
化学 | 214篇 |
晶体学 | 5篇 |
力学 | 8篇 |
数学 | 33篇 |
物理学 | 93篇 |
出版年
2024年 | 2篇 |
2023年 | 5篇 |
2022年 | 9篇 |
2021年 | 19篇 |
2020年 | 10篇 |
2019年 | 15篇 |
2018年 | 7篇 |
2017年 | 14篇 |
2016年 | 14篇 |
2015年 | 12篇 |
2014年 | 11篇 |
2013年 | 25篇 |
2012年 | 32篇 |
2011年 | 17篇 |
2010年 | 6篇 |
2009年 | 18篇 |
2008年 | 14篇 |
2007年 | 17篇 |
2006年 | 15篇 |
2005年 | 5篇 |
2004年 | 13篇 |
2003年 | 10篇 |
2002年 | 8篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 7篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 7篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1979年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有353条查询结果,搜索用时 250 毫秒
111.
Xiangfan Piao Hyun‐Jung Choi Sang Dong Kim Philsu Kim 《Numerical Methods for Partial Differential Equations》2014,30(3):788-812
In this article, a fast singly diagonally implicit Runge–Kutta method is designed to solve unsteady one‐dimensional convection diffusion equations. We use a three point compact finite difference approximation for the spatial discretization and also a three‐stage singly diagonally implicit Runge–Kutta (RK) method for the temporal discretization. In particular, a formulation evaluating the boundary values assigned to the internal stages for the RK method is derived so that a phenomenon of the order of the reduction for the convergence does not occur. The proposed scheme not only has fourth‐order accuracy in both space and time variables but also is computationally efficient, requiring only a linear matrix solver for a tridiagonal matrix system. It is also shown that the proposed scheme is unconditionally stable and suitable for stiff problems. Several numerical examples are solved by the new scheme and the numerical efficiency and superiority of it are compared with the numerical results obtained by other methods in the literature. © 2013 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 30: 788–812, 2014 相似文献
112.
113.
Junfei Duan Yongkang Wang Hongxing Li Donghai Wei Fang Wen Guanhua Zhang Piao Liu Lingjun Li Wei‐bing Zhang Zhaoyong Chen 《化学:亚洲杂志》2020,15(10):1613-1620
Heterostructure engineering of electrode materials, which is expected to accelerate the ion/electron transport rates driven by a built‐in internal electric field at the heterointerface, offers unprecedented promise in improving their cycling stability and rate performance. Herein, carbon nanotubes with Co9S8/ZnS heterostructures embedded in a N‐doped carbon framework (Co9S8/ZnS@NC) have been rationally designed via an in‐situ vapor chemical transformation strategy with the aid of thiophene, which not only acted as carbon source for the growth of carbon nanotubes but also as sulfur source for the sulfurization of metal Zn and Co. Density functional theory (DFT) calculation shows an about 3.24 eV electrostatic potential difference between ZnS and Co9S8, which results in a strong electrostatic field across the interface that makes electrons transfer from Co9S8 to the ZnS side. As expected, a stable cycling performance with reversible capacity of 411.2 mAh g?1 at 1000 mA g?1 after 300 cycles, excellent rate capability (324 mAh g?1 at 2000 A g?1) and a high percentage of pseudocapacitance contribution (87.5% at 2.2 mv/s) for lithium‐ion batteries (LIBs) are achieved. This work provides a possible strategy for designing multicomponent heterostructural materials for application in energy storage and conversion fields. 相似文献
114.
Hu Yi Zhang Zhen Jun Yang Hong Wu Yu Zhi Song Piao Ling Tai Ma Ji Mei Min 《合成通讯》2013,43(23):4113-4126
The syntheses of 2-(4-aminocarbonyl-2-thiazoyl)-1,4-anhydro-D-ribitol 10 and 2-(4-aminocarbonyl-2-thiazoyl)-1,4-anhydro-D-arabitol 11 have been accomplished via the construction of thiazoyl moiety from the cyanohydrins 2 and 3. 相似文献
115.
Zhang Xi-Tian Zhang We-Ching Piao We-Zhi Li Dian-En Wu Sheng-Li Du Shu-Qin 《Fiber and Integrated Optics》1990,9(3):219-223
High-power diffraction-limited phase-locked gallium-arsenide (GaAs)/ gallium-aluminum-arsenide (GaAlAs) semiconductor laser arrays have been fabricated using the LPE technique, the standard photolithographic technique, wet etching, and proton bombardment. The tailored gain-guided arrays are made by varying the width of the channels of the lasers while keeping the spacing between them constant. The array consists of six lasers. Its optical output power per facet is 300 mW at 2.71th with single-mode continuous wave (CW) operation and single lobe far-field pattern with full width at half maximum (FWHM) of 1.90°. 相似文献
116.
通常情况下,由于计算机在字符显示状态下在内存中存在一个显示代码缓存区,此缓存区存放屏幕上显示内容的ASCⅡ码;因此在LED显示应用上,尤其在需要将控制机显示内容在另一区域的LED屏幕重现时所需要的数据传输方面上,上述代码缓存区具有重要的作用.但是当我们使用象pc-1500这样的机器作LED显示系统的控制机时,由于它无上述的系统有规律的顺序显示代码缓存区,同时鉴于LED与主控机点阵的不同及需传送的数据量等问题,我们在传输屏幕内容上存在一定的困难.本文提出并采用一种布尔变换及解变换方法来解决这个问题. 相似文献
117.
A simple and efficient AlCl(3)-mediated C-C coupling reaction between readily available alpha-hydroxyketene-S,S-acetals and various arenes via direct substitution of the hydroxy group in alcohols has been developed. On the basis of this C-C coupling reaction, a series of bio- and pharmacologically important 3,4-disubstituted dihydrocoumarins, difficult to obtain by other methods, were prepared in high yields by a sequential Friedel-Crafts alkylation and intramolecular annulation reaction of alpha-hydroxyketene acyclic-S,S-acetals with phenols under mild conditions. 相似文献
118.
针对水下低频声源的方位估计问题,基于基元紧密排列的二维矢量阵,建立了一种超指向性波束形成方法.根据矢量基元差分运算构建各阶多极子模型,获得了几乎与频率无关的模态函数,并经加权计算可在低频条件下实现超指向性波束,以解决阵列孔径对波束性能的限制.同时,结合输出信噪比最大准则所得波束,分析了超指向性波束形成算法的稳定性与波导的影响程度,探索模态阶数与阵列参数的选取原则.通过阵列性能的仿真计算与实际阵列的测量数据表明,该算法可在小尺寸阵列孔径下获得良好的阵列波束,兼具了水下线型超指向性阵和环形超指向性阵的优点,可有效实现水下低频声源的水平方位估计;且波束性能可通过调节模态阶数与基元间距以达到最佳,并受水下声波导多途与频散效应影响有限. 相似文献
119.
Yu T Park J Moon J An K Piao Y Hyeon T 《Journal of the American Chemical Society》2007,129(47):14558-14559
Uniform goethite nanotubes were synthesized from the reaction of hydrazine with Fe(III)-oleate complex immobilized in reverse micelles. The nanotubes have interesting parallelogram cross section with uniform edge dimension of as small as 7 nm. The edge dimensions and lengths of the nanotubes were easily controlled by varying the reaction conditions. 相似文献
120.
Mohammed Sharif Swallah Hongliang Fan Sainan Wang Hansong Yu Chunhong Piao 《Molecules (Basel, Switzerland)》2021,26(2)
Okara is a white-yellow fibrous residue consisting of the insoluble fraction of the soybean seeds remaining after extraction of the aqueous fraction during the production of tofu and soymilk, and is generally considered a waste product. It is packed with a significant number of proteins, isoflavones, soluble and insoluble fibers, soyasaponins, and other mineral elements, which are all attributed with health merits. With the increasing production of soy beverages, huge quantities of this by-product are produced annually, which poses significant disposal problems and financial issues for producers. Extensive studies have been done on the biological activities, nutritional values, and chemical composition of okara as well as its potential utilization. Owing to its peculiar rich fiber composition and low cost of production, okara might be potentially useful in the food industry as a functional ingredient or good raw material and could be used as a dietary supplement to prevent varied ailments such as prevention of diabetes, hyperlipidemia, obesity, as well as to stimulate the growth of intestinal microbes and production of microbe-derived metabolites (xenometabolites), since gut dysbiosis (imbalanced microbiota) has been implicated in the progression of several complex diseases. This review seeks to compile scientific research on the bioactive compounds in soybean residue (okara) and discuss the possible prebiotic impact of this fiber-rich residue as a functional diet on eubiosis/dysbiosis condition of the gut, as well as the consequential influence on liver and kidney functions, to facilitate a detailed knowledge base for further exploration, implementation, and development. 相似文献