全文获取类型
收费全文 | 124688篇 |
免费 | 10540篇 |
国内免费 | 16765篇 |
专业分类
化学 | 80696篇 |
晶体学 | 2937篇 |
力学 | 5051篇 |
综合类 | 1094篇 |
数学 | 21563篇 |
物理学 | 40652篇 |
出版年
2024年 | 208篇 |
2023年 | 1506篇 |
2022年 | 3301篇 |
2021年 | 3269篇 |
2020年 | 3575篇 |
2019年 | 3540篇 |
2018年 | 3003篇 |
2017年 | 3674篇 |
2016年 | 3918篇 |
2015年 | 3362篇 |
2014年 | 4919篇 |
2013年 | 9369篇 |
2012年 | 6367篇 |
2011年 | 7671篇 |
2010年 | 6281篇 |
2009年 | 8144篇 |
2008年 | 8410篇 |
2007年 | 8707篇 |
2006年 | 7728篇 |
2005年 | 6594篇 |
2004年 | 5877篇 |
2003年 | 5412篇 |
2002年 | 5402篇 |
2001年 | 4119篇 |
2000年 | 3958篇 |
1999年 | 3284篇 |
1998年 | 2955篇 |
1997年 | 2165篇 |
1996年 | 1958篇 |
1995年 | 1808篇 |
1994年 | 1791篇 |
1993年 | 1409篇 |
1992年 | 1371篇 |
1991年 | 979篇 |
1990年 | 789篇 |
1989年 | 671篇 |
1988年 | 580篇 |
1987年 | 494篇 |
1986年 | 421篇 |
1985年 | 427篇 |
1984年 | 384篇 |
1983年 | 226篇 |
1982年 | 323篇 |
1981年 | 321篇 |
1980年 | 246篇 |
1979年 | 250篇 |
1978年 | 208篇 |
1977年 | 195篇 |
1976年 | 129篇 |
1973年 | 95篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Patrick Imrie Jianyong Jin 《Journal of polymer science. Part A, Polymer chemistry》2022,60(2):149-174
4D printing is an exciting branch of additive manufacturing. It relies on established 3D printing techniques to fabricate objects in much the same way. However, structures which fall into the 4D printed category have the ability to change with time, hence the “extra dimension.” The common perception of 4D printed objects is that of macroscopic single-material structures limited to point-to-point shape change only, in response to either heat or water. However, in the area of polymer 4D printing, recent advancements challenge this understanding. A host of new polymeric materials have been designed which display a variety of wonderful effects brought about by unconventional stimuli, and advanced additive manufacturing techniques have been developed to accommodate them. As a result, the horizons of polymer 4D printing have been broadened beyond what was initially thought possible. In this review, we showcase the many studies which evolve the very definition of polymer 4D printing, and reveal emerging areas of research integral to its advancement. 相似文献
2.
《Mendeleev Communications》2022,32(1):126-128
3-Aryl-5-methylidene-2-thiohydantoins were constructed in one-pot reaction of aryl isothiocyanates and 3-morpholino- alanine in alkaline medium with the subsequent treatment with boiling hydrochloric acid. 相似文献
3.
Joshua Maglione 《Journal of Pure and Applied Algebra》2021,225(3):106528
Like the lower central series of a nilpotent group, filters generalize the connection between nilpotent groups and graded Lie rings. However, unlike the case with the lower central series, the associated graded Lie ring may share few features with the original group: e.g. the associated Lie ring can be trivial or arbitrarily large. We determine properties of filters such that every isomorphism between groups is induced by an isomorphism between graded Lie rings. 相似文献
4.
5.
Prof. Dr. Peter Hess 《Chemphyschem》2022,23(6):e202100880
In the periodic table the position of each atom follows the ‘aufbau’ principle of the individual electron shells. The resulting intrinsic periodicity of atomic properties determines the overall behavior of atoms in two-dimensional (2D) bonding and structure formation. Insight into the type and strength of bonding is the key in the discovery of innovative 2D materials. The primary features of 2D bonding and the ensuing monolayer structures of the main-group II–VI elements result from the number of valence electrons and the change of atom size, which determine the type of hybridization. The results reveal the tight connection between strength of bonding and bond length in 2D networks. The predictive power of the periodic table reveals general rules of bonding, the bonding-structure relationship, and allows an assessment of published data of 2D materials. 相似文献
6.
M. Amar D. Andreucci R. Gianni C. Timofte 《Journal of Mathematical Analysis and Applications》2021,493(2):124533
We prove a well-posedness result for two pseudo-parabolic problems, which can be seen as two models for the same electrical conduction phenomenon in heterogeneous media, neglecting the magnetic field. One of the problems is the concentration limit of the other one, when the thickness of the dielectric inclusions goes to zero. The concentrated problem involves a transmission condition through interfaces, which is mediated by a suitable Laplace-Beltrami type equation. 相似文献
7.
8.
9.
《Mendeleev Communications》2022,32(1):105-108
A mixed-metal 1D coordination polymer [CaCu(HBTC)2(H2O)8]n (where H3BTC – benzene-1,3,5-tric arboxylic acid) was obtained in a solvothermal synthesis of a well-known copper-containing metal–organic framework [Cu3(BTC)2(H2O)3]n (HKUST-1) in autoclaves 3D-printed from commercial polypropylene. This material was a source of calcium ions, apparently, leaking from a colorant (calcium carbonate) promoted by glacial acetic acid as a modulator used to produce large single crystals of HKUST-1. This finding was confirmed by elemental analysis and a model experiment that resulted in a new calcium-based 1D coordination polymer [Ca(H2BTC)2(H2O)5]n under the same solvothermal conditions with no copper or calcium salts put into a 3D-printed autoclave. 相似文献
10.
Bifurcation analysis of visual angle model with anticipated time and stabilizing driving behavior 下载免费PDF全文
Xueyi Guan 《中国物理 B》2022,31(7):70507-070507
In the light of the visual angle model (VAM), an improved car-following model considering driver's visual angle, anticipated time and stabilizing driving behavior is proposed so as to investigate how the driver's behavior factors affect the stability of the traffic flow. Based on the model, linear stability analysis is performed together with bifurcation analysis, whose corresponding stability condition is highly fit to the results of the linear analysis. Furthermore, the time-dependent Ginzburg-Landau (TDGL) equation and the modified Korteweg-de Vries (mKdV) equation are derived by nonlinear analysis, and we obtain the relationship of the two equations through the comparison. Finally, parameter calibration and numerical simulation are conducted to verify the validity of the theoretical analysis, whose results are highly consistent with the theoretical analysis. 相似文献