全文获取类型
收费全文 | 99155篇 |
免费 | 8363篇 |
国内免费 | 9225篇 |
专业分类
化学 | 32967篇 |
晶体学 | 419篇 |
力学 | 10439篇 |
综合类 | 1577篇 |
数学 | 44355篇 |
物理学 | 26986篇 |
出版年
2024年 | 184篇 |
2023年 | 918篇 |
2022年 | 1667篇 |
2021年 | 1924篇 |
2020年 | 2295篇 |
2019年 | 2533篇 |
2018年 | 2182篇 |
2017年 | 2501篇 |
2016年 | 2823篇 |
2015年 | 2423篇 |
2014年 | 3729篇 |
2013年 | 7398篇 |
2012年 | 4139篇 |
2011年 | 4774篇 |
2010年 | 4108篇 |
2009年 | 5609篇 |
2008年 | 6039篇 |
2007年 | 6253篇 |
2006年 | 5739篇 |
2005年 | 4895篇 |
2004年 | 4486篇 |
2003年 | 4457篇 |
2002年 | 4169篇 |
2001年 | 3467篇 |
2000年 | 3398篇 |
1999年 | 3094篇 |
1998年 | 2796篇 |
1997年 | 2338篇 |
1996年 | 2032篇 |
1995年 | 1792篇 |
1994年 | 1634篇 |
1993年 | 1361篇 |
1992年 | 1293篇 |
1991年 | 1019篇 |
1990年 | 836篇 |
1989年 | 705篇 |
1988年 | 644篇 |
1987年 | 508篇 |
1986年 | 440篇 |
1985年 | 523篇 |
1984年 | 539篇 |
1983年 | 272篇 |
1982年 | 422篇 |
1981年 | 475篇 |
1980年 | 374篇 |
1979年 | 355篇 |
1978年 | 277篇 |
1977年 | 249篇 |
1976年 | 188篇 |
1974年 | 118篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
32.
33.
Synthesis of diisocyanides with phenolic groups and their polymerization to helically chiral poly(quinoxaline‐2,3‐diyl)s
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)
Johannes Scholz Michael Reggelin 《Journal of polymer science. Part A, Polymer chemistry》2015,53(11):1320-1329
The development of synthetic routes which lead to five new diisocyanide monomers with one or two phenolic groups is described. Their polymerization behavior is studied with Pd‐ and Ni‐based initiators, as well as under microwave irradiation. The polymerizability is mainly dominated by steric effects as is concluded from experiments using different protecting groups. Chiroptical properties of these new polymers are studied by CD‐spectroscopy. After deprotection, helically chiral poly(quinoxalin‐2,3‐diyl)s are obtained which display a Brønsted function attached to a stereolabile biaryl axis whose configuration should be influenced by the chiral polymer backbone. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1320–1329 相似文献
34.
Liming Fan Feng Wang Dongsheng Zhao Yuxin Peng Yuxin Deng Yinwei Luo Xiutang Zhang 《应用有机金属化学》2020,34(12):e5960
Guided by the self-penetrating features can improve the stability of metal organic frameworks (MOFs), an unprecedented 3D self-penetrated framework, {[Zn (tptc)0.5(bimb)]·H2O}n ( NUC-6 , here NUC corresponding to North University of China), with 3D (4,4)-c {86} net, was designed. Benefit from the high chemical stability and excellent luminescent property, NUC-6 can be act as an efficient multi-response chemo-sensor in detecting dichloronitroaniline pesticide and nitrofuran antibiotics in water with the detection limits are 116 ppb for DCN pesticide, 16 ppb for NFT antibiotic, and 12 ppb for NTZ antibiotic. Besides, the mechanisms of luminescence quenching were revealed from the viewpoint of internal filter effect (IFE) and photo-induced electron transfer (PET), implied by the optical spectroscopy and quantum chemical calculation. This work provides a promising strategy to design stable MOFs by improving the self-penetrating features and to expand their practical applications in the detection of organic pollutants in aqueous medium. 相似文献
35.
AbstractRealistic stochastic modeling is increasingly requiring the use of bounded noises. In this work, properties and relationships of commonly employed bounded stochastic processes are investigated within a solid mathematical ground. Four families are object of investigation: the Sine-Wiener (SW), the Doering–Cai–Lin (DCL), the Tsallis–Stariolo–Borland (TSB), and the Kessler–Sørensen (KS) families. We address mathematical questions on existence and uniqueness of the processes defined through Stochastic Differential Equations, which often conceal non-obvious behavior, and we explore the behavior of the solutions near the boundaries of the state space. The expression of the time-dependent probability density of the Sine-Wiener noise is provided in closed form, and a close connection with the Doering–Cai–Lin noise is shown. Further relationships among the different families are explored, pathwise and in distribution. Finally, we illustrate an analogy between the Kessler–Sørensen family and Bessel processes, which allows to relate the respective local times at the boundaries. 相似文献
36.
37.
38.
Alessandro Morando Paola Trebeschi Tao Wang 《Journal of Differential Equations》2019,266(9):5397-5430
We show the short-time existence and nonlinear stability of vortex sheets for the nonisentropic compressible Euler equations in two spatial dimensions, based on the weakly linear stability result of Morando and Trebeschi (2008) [20]. The missing normal derivatives are compensated through the equations of the linearized vorticity and entropy when deriving higher-order energy estimates. The proof of the resolution for this nonlinear problem follows from certain a priori tame estimates on the effective linear problem in the usual Sobolev spaces and a suitable Nash–Moser iteration scheme. 相似文献
39.
In this paper, we propose a sufficient and necessary condition for the boundedness of all the solutions for the equation with the critical situation that on g and p, where , is periodic and is bounded. 相似文献
40.
Inflation of balloons provides a straightforward way of achieving large biaxial deformations. Previous studies have shown that when a balloon bursts, crack propagation occurs at very high speed – much higher than would be expected from the low strain modulus and elastic wave velocity of the rubber. The present paper is concerned with studies of the deformation and fracture of cylindrical balloons. On inflation, the deformations of such a balloon pass through an unstable region but subsequently increase monotonically with pressure. In this relatively high pressure region, the ratio of the longitudinal and circumferential extension ratios is broadly in accord with expectations from high-strain elasticity theory when the ratio of the corresponding stresses is taken into account. On bursting, crack speeds up to around 300 m/s in this region. It is shown that these speeds are in accord with large increase in incremental moduli for the highly-strained rubber. Marked changes in crack tip profile observed at very high crack speeds are consistent with control of the rate of growth by inertia rather than by the viscoelastic properties of the rubber (as is believed to be the case at lower speeds). Consistent with this, various elastomers having different glass transition temperatures show similar crack growth behaviour in the very high speed region. 相似文献