全文获取类型
收费全文 | 11778篇 |
免费 | 1621篇 |
国内免费 | 1020篇 |
专业分类
化学 | 3049篇 |
晶体学 | 76篇 |
力学 | 2236篇 |
综合类 | 215篇 |
数学 | 4891篇 |
物理学 | 3952篇 |
出版年
2024年 | 12篇 |
2023年 | 99篇 |
2022年 | 154篇 |
2021年 | 214篇 |
2020年 | 354篇 |
2019年 | 269篇 |
2018年 | 326篇 |
2017年 | 400篇 |
2016年 | 479篇 |
2015年 | 346篇 |
2014年 | 578篇 |
2013年 | 844篇 |
2012年 | 590篇 |
2011年 | 730篇 |
2010年 | 643篇 |
2009年 | 728篇 |
2008年 | 761篇 |
2007年 | 816篇 |
2006年 | 777篇 |
2005年 | 676篇 |
2004年 | 660篇 |
2003年 | 552篇 |
2002年 | 505篇 |
2001年 | 375篇 |
2000年 | 383篇 |
1999年 | 339篇 |
1998年 | 254篇 |
1997年 | 226篇 |
1996年 | 197篇 |
1995年 | 186篇 |
1994年 | 132篇 |
1993年 | 123篇 |
1992年 | 94篇 |
1991年 | 82篇 |
1990年 | 77篇 |
1989年 | 40篇 |
1988年 | 37篇 |
1987年 | 43篇 |
1986年 | 40篇 |
1985年 | 28篇 |
1984年 | 40篇 |
1983年 | 16篇 |
1982年 | 36篇 |
1981年 | 15篇 |
1980年 | 24篇 |
1979年 | 26篇 |
1978年 | 22篇 |
1977年 | 17篇 |
1976年 | 10篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
1.
2.
Liquid-liquid-solid systems are becoming increasingly common in everyday life with many possible applications. Here, we focus on a special case of such liquid-liquid-solid systems, namely, capillary suspensions. These capillary suspensions originate from particles that form a network based on capillary forces and are typically composed of solids in a bulk liquid with an added secondary liquid. The structure of particle networks based on capillary bridges possesses unique properties compared with networks formed via other attractive interactions where these differences are inherently related to the properties of the capillary bridges, such as bridge breaking and coalescence between adjacent bridges. Thus, to tailor the mechanical properties of capillary suspensions to specific requirements, it is important to understand the influences on different length scales ranging from the dynamics of the bridges with varying external stimuli to the often heterogeneous network structure. 相似文献
3.
Baoquan Zhou Daqing Jiang Bingtao Han Tasawar Hayat 《Mathematical Methods in the Applied Sciences》2022,45(1):423-455
Considering the effect of stochasticity including white noise and colored noise, this paper aims to study a hybrid stochastic cholera epidemic model with waning vaccine-induced immunity and nonlinear telegraph perturbations. First, we derive a critical value related to the basic reproduction number of the deterministic model. The key aim of this paper is to generalize the θ-stochastic criterion method proposed by the recent work (Han et al. in Chaos Solit Fract 140:110238, 2020) to eliminate nonlinear telegraph perturbations. Next, via constructing several θ-stochastic Lyapunov functions and using the generalized method, we further prove that the stochastic model have a unique ergodic stationary distribution under . Results show that the prevention and control of cholera epidemic depend on low transmission rate and small telegraph perturbations. Finally, the corresponding numerical simulations are performed to illustrate our analytical results and a practical application on the Somalia cholera outbreak is shown at the end of this paper. 相似文献
4.
5.
Herein, we successfully construct the 3D biocompatible graphene through crosslinking 2D graphene nanosheet onto carbon fiber paper with poly(diallyldimethylammonium chloride) (PDDA) as anode of the alcohol biofuel cell. Compared with the bioanode without 3D graphene, the current density and output power of PDDA-graphene-ADH bioanode is increased by 23 % and 41 % at a high concentration of ethanol at pH 8.9, suggesting the stabilization role of graphene in enzyme loading. The study provides us a deep analysis on structures and performances of the bioanode incl. electrochemistry, X-ray photoelectron spectra, and atomic force microscopy images, which is significant to develop the new methods to construct 3D porous electrodes in energy conversion device. 相似文献
6.
Longbo Li Andy T. Tek Rudy J. Wojtecki Rebecca Braslau 《Journal of polymer science. Part A, Polymer chemistry》2019,57(17):1821-1835
Internal plasticization of polyvinyl chloride (PVC) using thermal azide‐alkyne Huisgen dipolar cycloaddition between azidized PVC and electron‐poor acetylenediamides incorporating a branched glutamic acid linker resulted in incorporation of four plasticizing moieties per attachment point on the polymer chain. A systematic study incorporating either alkyl or polyethylene glycol esters provided materials with varying degrees of plasticization, with depressed Tg values ranging from ?1 °C to 62 °C. Three interesting trends were observed. First, Tg values of PVC bearing various internal plasticizers were shown to decrease with increasing chain length of the plasticizing ester. Second, branched internal plasticizers bearing triethylene glycol chains had lower Tg values compared to those with similar length long‐chain alkyl groups. Finally, thermogravimetric analysis of these internally plasticized PVC samples revealed that these branched internal plasticizers bearing alkyl chains are more thermally stable than similarity branched plasticizers bearing triethylene glycol units. These internal tetra‐plasticizers were synthesized and attached to PVC‐azide in three simple synthetic steps. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 1821–1835 相似文献
7.
YOU Mingqing 《力学与实践》2019,41(4):436
偏心转子惯性力引起的底座运动受到地面摩擦的影响,与光滑情形的理论结果存在定性差异。转子逆时针匀速旋转的惯性力若小于构件总重,则底座随摩擦因子增加而出现连续、一次停顿和两次停顿的振动及完全静止的4种状态。因惯性力对正压力及摩擦力的影响,底座在连续及一次停顿的振动时右向位移较大;而底座跳起时如``蛤蟆夯'则整体向左移动。 相似文献
8.
9.
10.
An electromechanical integrated electrostatic harmonic actuator is promising for the miniaturization of electromechanical devices. As the dimensions of the actuator decrease, the effects of the van der Waals force become obvious. In this study, by considering the nonlinearity of electrostatic and van der Waals forces, nonlinear vibration equations of the flexible ring of an electrostatic harmonic actuator are deduced. Using these equations, the nonlinear free vibration and nonlinear forced response of the actuator are investigated. The effects of the van der Waals force on the nonlinear vibration of the flexible ring are analyzed. Results show that these effects of the van der Waals force are relatively obvious under some conditions and should be considered. 相似文献