全文获取类型
收费全文 | 276479篇 |
免费 | 16781篇 |
国内免费 | 859篇 |
专业分类
化学 | 169508篇 |
晶体学 | 4038篇 |
力学 | 12622篇 |
综合类 | 1篇 |
数学 | 28124篇 |
物理学 | 79826篇 |
出版年
2023年 | 4271篇 |
2021年 | 3930篇 |
2020年 | 6152篇 |
2019年 | 4214篇 |
2018年 | 4868篇 |
2017年 | 3216篇 |
2016年 | 9176篇 |
2015年 | 7603篇 |
2014年 | 8625篇 |
2013年 | 14935篇 |
2012年 | 10581篇 |
2011年 | 10422篇 |
2010年 | 9892篇 |
2009年 | 9812篇 |
2008年 | 9716篇 |
2007年 | 9472篇 |
2006年 | 8406篇 |
2005年 | 7583篇 |
2004年 | 6993篇 |
2003年 | 6170篇 |
2002年 | 6109篇 |
2001年 | 7136篇 |
2000年 | 5403篇 |
1999年 | 4261篇 |
1998年 | 3594篇 |
1997年 | 3549篇 |
1996年 | 3367篇 |
1995年 | 3137篇 |
1994年 | 3030篇 |
1993年 | 3255篇 |
1992年 | 3238篇 |
1991年 | 3400篇 |
1990年 | 3140篇 |
1989年 | 3096篇 |
1988年 | 3174篇 |
1987年 | 3052篇 |
1986年 | 2885篇 |
1985年 | 3912篇 |
1984年 | 4111篇 |
1983年 | 3295篇 |
1982年 | 3539篇 |
1981年 | 3482篇 |
1980年 | 3412篇 |
1979年 | 3505篇 |
1978年 | 3602篇 |
1977年 | 3643篇 |
1976年 | 3790篇 |
1975年 | 3566篇 |
1974年 | 3576篇 |
1973年 | 3465篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Giang Truong Nguyen Prof. Dr. Liviu Ungur 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(30):e202200227
Employing radical bridges between anisotropic metal ions has been a viable route to achieve high-performance single-molecule magnets (SMMs). While the bridges have been mainly considered for their ability to promote exchange interactions, the crystal-field effect arising from them has not been taken into account explicitly. This lack of consideration may distort the understanding and limit the development of the entire family. To shed light on this aspect, herein we report a theoretical investigation of a series of N -radical-bridged diterbium complexes. It is found that while promoting strong exchange coupling between the terbium ions, the N -radical induces a crystal field that interferes destructively with that of the outer ligands, and thus reduces the overall SMM behavior. Based on the theoretical results, we conclude that the SMM behavior in this series could be further maximized if the crystal field of the outer ligands is designed to be collinear with that of the radical bridge. This conclusion can be generalized to all exchange-coupled SMMs. 相似文献
2.
3.
4.
5.
Bridgette Yani Ansie Harding 《International Journal of Mathematical Education in Science & Technology》2019,50(7):1037-1049
ABSTRACTThis paper focuses on the students who are registered in the University of Pretoria’s academic development programme, named the Four-year Programme (FYP). The programme was introduced as a gateway for students who are underprepared but have the potential to succeed and then continue their studies into the mainstream science programmes. Our research focuses on measuring the change in the academic maturity of these students. In the theoretical framework that we developed, academic maturity is subdivided into two components namely non-subject based maturity and subject based maturity (mathematical maturity). This paper focuses on measuring non-subject based academic maturity. The survey used for this purpose is called the Student Academic Readiness Survey (STARS), taken at the beginning of the year and after the first semester respectively. The results of the surveys are compared to measure the change in students’ views. Results show that in all constructs there is a surprising decline in students’ perceptions regarding their own abilities over the first semester at university. We use the Dunning–Kruger effect to explain this unexpected decline, in that students seem to develop a more realistic view of their own maturity, which in itself can be seen as a growth in academic maturity. 相似文献
6.
7.
N. I. Golovina G. N. Nechiporenko G. G. Nemtsev G. P. Dolganova V. P. Roshchupkin D. B. Lempert G. B. Manelis 《Russian Journal of Applied Chemistry》2007,80(1):24-30
Methods for phase stabilization of ammonium nitrate were sought for in order to considerably expand the application area of this oxidizing agent in various-purpose self-combustible formulations, including that in a new generation of gas-generating formulations for automobile air bags. New methods for stabilization of ammonium nitrate were studied and, in particular, a search was made for organic compounds that can stabilize ammonium nitrate even at their low content. The mechanism of phase state stabilization of ammonium nitrate by compounds of this kind was examined. 相似文献
8.
9.
An attempt is made to find out the suitable entrainment and exit boundary conditions in laminar flow situations. Streamfunction vorticity formulation of the Navier–Stokes equations are solved by ADI method. Two‐dimensional laminar plane wall jet flow is used to test different forms of the boundary conditions. Results are compared with the experimental and similarity solution and the proper boundary condition is suggested. The Kind 1 boundary condition is recommended. It consists of zero first derivative condition for velocity variable and for streamfunction equation, mixed derivative at the entrainment and exit boundaries. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
10.
The paper discusses the applicability of quasi-crystalline approximation to describing the thermal motion of water molecules in their normal and supercooled states. The problem is subjected to the critical analysis of experimental data on incoherent scattering of slow neutrons based on theories developed by Singwi-Sjolander [1] and Oskotsky [2] modified to duly take into account the limited applicability range of diffusion approximation. The applicability conditions of quasi-crystalline approximation are shown to be consistently satisfied only when water is in supercooled state and within a narrow temperature range above the melting temperature. 相似文献