全文获取类型
收费全文 | 13595篇 |
免费 | 2150篇 |
国内免费 | 1813篇 |
专业分类
化学 | 10454篇 |
晶体学 | 196篇 |
力学 | 786篇 |
综合类 | 109篇 |
数学 | 1640篇 |
物理学 | 4373篇 |
出版年
2024年 | 28篇 |
2023年 | 203篇 |
2022年 | 377篇 |
2021年 | 458篇 |
2020年 | 470篇 |
2019年 | 554篇 |
2018年 | 451篇 |
2017年 | 390篇 |
2016年 | 664篇 |
2015年 | 764篇 |
2014年 | 802篇 |
2013年 | 1017篇 |
2012年 | 1194篇 |
2011年 | 1162篇 |
2010年 | 902篇 |
2009年 | 871篇 |
2008年 | 944篇 |
2007年 | 768篇 |
2006年 | 682篇 |
2005年 | 644篇 |
2004年 | 551篇 |
2003年 | 505篇 |
2002年 | 616篇 |
2001年 | 482篇 |
2000年 | 310篇 |
1999年 | 265篇 |
1998年 | 226篇 |
1997年 | 158篇 |
1996年 | 144篇 |
1995年 | 135篇 |
1994年 | 113篇 |
1993年 | 82篇 |
1992年 | 74篇 |
1991年 | 77篇 |
1990年 | 52篇 |
1989年 | 38篇 |
1988年 | 26篇 |
1987年 | 28篇 |
1986年 | 17篇 |
1985年 | 19篇 |
1984年 | 22篇 |
1983年 | 16篇 |
1981年 | 16篇 |
1980年 | 31篇 |
1979年 | 11篇 |
1978年 | 27篇 |
1977年 | 49篇 |
1976年 | 21篇 |
1975年 | 20篇 |
1974年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
For one‐dimensional simple symmetric random walk, the Hausdorff and packing dimensions of sets of sample paths with prescribed rate of returns to the origin are determined. This gives a multifractal decomposition of the underlying sample space. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
22.
对数似然比与整值随机变量序列的一类强律 总被引:2,自引:0,他引:2
本文引进对数似然比作为整值随机变量序列相对于服从几何分布的独立随机变量序列的偏差的一种度量,并通过限制对数似然比给出了样本空间的一个子集.在此子集上得到了一类用不等式表示的强律,其中包含整值随机变量序列与相对熵密度及几何分布的熵函数有关的若干极限性质. 相似文献
23.
Rhizopus arrhizus lipase (EC 3.1.1.3; triacylglycerol hydrolase) was used in this study to investigate the hydrolysis of palm kernel olein in AOT-isooctane-water reversed micelle system at Wo = 13, pH = 7, and T = 30?C. The hydrolytic reaction obeys Michaelis-Menten kinetics for substrate concentrations in the range (0.175 and 0.877M). The apparentK m and Vmax for the substrate were 0.397M (equivalent to 9.06% w/v) and 5523 U/mg protein, respectively. Product inhibition with a dissociation constant of the enzyme-product complex,K I = 9.74 mM, was confirmed. Experimental results from the change of product concentrations with respect to time correlated sufficiently with those predicted theoretically from the rate equation for a reaction time up to 100 min. However, the discrepancy between the observed results and the predicted ones would increase with reaction time. Possible reasons for this deviation were discussed. 相似文献
24.
本文描述了用膜吸收法测量激光等离子体辐射温度空间分布的原理和方法给出了柱形缝靶轴向辐射温度随空间位置变化的特征,对测量结果进行了分析讨论。 相似文献
25.
Ju Yeon Woo Eun Hee Kim Byung Kyu Kim 《Journal of polymer science. Part A, Polymer chemistry》2007,45(23):5590-5596
Doping of conductive fullerene particles to the formulation of conventional holographic polymer dispersed liquid crystal‐induced dual effects of reducing both droplet coalescence and operating voltage. Fullerene induced an induction period which otherwise does not exist, followed by a gradual increase of diffraction efficiency to a saturation value being increased with increasing fullerene content. The increased diffraction efficiency was caused by the decreased droplet coalescence which was due to the hindered migration of LC by the fullerene particles. On the other hand, doped fullerene particles augmented the conductivity of polymer phase and hence the local electrical field imposed on LC droplet, which overcome the threshold for driving and reduced operating voltage and response times. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5590–5596, 2007 相似文献
26.
Let ? be a primitive substitution on a two-letter alphabet {a,b} having two fixed points ξa and ξb. We show that the substitution ? is invertible if and only if one has ξa=abξ and ξb=baξ. To cite this article: Z.-X. Wen et al., C. R. Acad. Sci. Paris, Ser. I 334 (2002) 727–731. 相似文献
27.
Jun Hua YU Xue Song WANG Bao Wen ZHANG* Yi CAO Technical Institute of Physics Chemistry Chinese Academy of Sciences Beijing 《中国化学快报》2002,13(10)
Porphyrin derivatives attract much more interest in photodynamic therapy (PDT). Their importance as therapeutic drugs and targeting agents has been widely recognized1, and many of the efforts have been put towards crafting new porphyrin-based molecular entities to achieve enhanced tumor localization, better tissue penetration and increased singlet oxygen quantum yield2. The states of porphyrins in tissue models such as micelles, lipid bilayers are extensively investigated focusing more or l… 相似文献
28.
We consider the classical problem of searching for a heavier coin in a set of n coins, n-1 of which have the same weight. The weighing device is b-balance which is the generalization of two-arms balance. The minimum numbers of weighings are determined exactly for worst-case sequential algorithm, average-case sequential algorithm, worst-case predetermined algorithm, average-case predetermined algorithm.We also investigate the above search model with additional constraint: each weighing is only allowed to use the coins that are still in doubt. We present a worst-case optimal sequential algorithm and an average-case optimal sequential algorithm requiring the minimum numbers of weighings. 相似文献
29.
WANG Jiang-yun GU Wen WANG Wen-zhen LIU Xin LIAO Dai-zheng 《高等学校化学研究》2006,22(3):283-286
Introduction Itiswell knownthatcyanogroupsincyanometa latessuchas[Ag(CN)2]-unitscanbeusedasbridg ingligandsandapolymericstructurecanbeformed throughsilver silver(argentophilic)interactions.This propertyhasbeenexploredintheconstructionofmany oligomericandp… 相似文献
30.
In this paper, the nonfragile control problem for synchronization of a class of chaotic dynamical systems with controller gain variations is studied. Using the Lyapunov method and LMI (linear matrix inequality) technique, a criterion for the existence of the nonfragile controller for synchronization is derived in terms of LMI. To show the effectiveness of the proposed method, the control problem is applied to Genesio chaotic system. 相似文献