全文获取类型
收费全文 | 14290篇 |
免费 | 1302篇 |
国内免费 | 1602篇 |
专业分类
化学 | 4581篇 |
晶体学 | 84篇 |
力学 | 766篇 |
综合类 | 259篇 |
数学 | 7846篇 |
物理学 | 3658篇 |
出版年
2024年 | 25篇 |
2023年 | 134篇 |
2022年 | 277篇 |
2021年 | 337篇 |
2020年 | 383篇 |
2019年 | 438篇 |
2018年 | 412篇 |
2017年 | 432篇 |
2016年 | 385篇 |
2015年 | 347篇 |
2014年 | 553篇 |
2013年 | 1435篇 |
2012年 | 571篇 |
2011年 | 706篇 |
2010年 | 616篇 |
2009年 | 822篇 |
2008年 | 870篇 |
2007年 | 1042篇 |
2006年 | 831篇 |
2005年 | 795篇 |
2004年 | 694篇 |
2003年 | 698篇 |
2002年 | 630篇 |
2001年 | 499篇 |
2000年 | 484篇 |
1999年 | 433篇 |
1998年 | 416篇 |
1997年 | 381篇 |
1996年 | 256篇 |
1995年 | 195篇 |
1994年 | 195篇 |
1993年 | 128篇 |
1992年 | 123篇 |
1991年 | 98篇 |
1990年 | 72篇 |
1989年 | 67篇 |
1988年 | 65篇 |
1987年 | 55篇 |
1986年 | 40篇 |
1985年 | 54篇 |
1984年 | 35篇 |
1983年 | 18篇 |
1982年 | 33篇 |
1981年 | 28篇 |
1980年 | 16篇 |
1979年 | 14篇 |
1978年 | 12篇 |
1977年 | 16篇 |
1976年 | 6篇 |
1959年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Rose Morris-Wright 《Journal of Pure and Applied Algebra》2021,225(1):106468
Parabolic subgroups are the building blocks of Artin groups. This paper extends previous results of Cumplido, Gebhardt, Gonzales-Meneses and Wiest, known only for parabolic subgroups of finite type Artin groups, to parabolic subgroups of FC-type Artin groups. We show that the class of finite type parabolic subgroups is closed under intersection. We also study an analog of the curve complex for mapping class group constructed by Cumplido et al. using parabolic subgroups. We extend the construction of this complex, called the complex of parabolic subgroups, to FC-type Artin groups. We show that this simplicial complex is, in most cases, infinite diameter and conjecture that it is δ-hyperbolic. 相似文献
2.
Dominik Vítek Prof. Aleš Růžička Lise Vermeersch Dr. Libor Dostál Dr. Jan Turek Prof. Roman Jambor 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(70):e202202639
Reactivity studies of the GeII→B complex L(Cl)Ge⋅BH3 ( 1 ; L=2-Et2NCH2-4,6-tBu2-C6H2) were performed to determine the effect on the GeII→B donation. N-coordinated compounds L(OtBu)Ge⋅BH3 ( 2 ) and [LGe⋅BH3]2 ( 3 ) were prepared. The possible tuning of the GeII→B interaction was proved experimentally, yielding compounds 1-PPh2-8-(LGe)-C10H6 ( 4 ) and L(Cl)Ge⋅GaCl3 ( 5 ) without a GeII→B interaction. In 5 , an unprecedented GeII→Ga coordination was revealed. The experimental results were complemented by a theoretical study focusing on the bonding in 1 − 5 . The different strength of the GeII→E (E=B, Ga) donation was evaluated by using energy decomposition analysis. The basicity of different L(X)Ge groups through proton affinity is also assessed. 相似文献
3.
《Discrete Mathematics》2022,345(10):112984
Let G be a generalized dicyclic group with identity 1. An inverse closed subset S of is called minimal if and there exists some such that . In this paper, we characterize distance-regular Cayley graphs of G under the condition that S is minimal. 相似文献
4.
5.
Reza Kordnezhadian Bing-Yu Li Armir Zogu Dr. Joachim Demaerel Prof. Dr. Wim M. De Borggraeve Dr. Ermal Ismalaj 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(60):e202201491
Pentafluorosulfanyl (SF5)-containing compounds and corresponding analogs are a highly valuable class of fluorine-containing building blocks owing to their unique properties. The reason for that is the set of peculiar and tremendously beneficial characteristics they can impart on molecules once introduced onto them. Despite this, their application in distinct scientific fields remains modest, given the extremely harsh reaction conditions needed to access such compounds. The recent synthetic approaches via S−F, and C−SF5 bond formation as well as the use of SF5-containing building blocks embody a “stairway-to-heaven” loophole in the synthesis of otherwise-inaccessible chemical scaffolds only a few years ago. Herein, we report and evaluate the properties of the SF5 group and analogs, by summarizing synthetic methodologies available to access them as well as following applications in material science and medicinal chemistry since 2015. 相似文献
6.
7.
V. V. Sagaradze N. V. Kataeva V. A. Zavalishin K. A. Kozlov V. V. Makarov A. R. Kuznetsov 《哲学杂志》2020,100(14):1868-1879
ABSTRACT The authors present the results of an investigation in Fe–Ni-Cr austenitic alloys of the low-temperature deformation-induced segregations of nickel that form in the micro regions being (i) located close to grain- and subgrain boundaries and (ii) characteristic of the concentration and magnetic inhomogeneities indicated by the appearance of a dark diffraction contrast at the electron diffraction patterns taken from these regions typical (at the same time) of an enhanced value of Curie temperature. The observed effects were connected with the micro distortions caused by the local change of lattice parameter because of an increase in nickel concentration, as well as in the result of a magnetostriction dilatation. Using methods of the X-ray energy dispersive spectroscopy (XEDS) and atomic-probe body-section radiography (tomography – APT) has made it possible to determine the borders of those regions of austenite that were characteristic of an enhanced concentration of nickel in the fields of the localisation of a deformation-induced segregation of nickel in the vicinity of grain (subgrain) boundaries of austenitic alloys of the types Fe–13Cr–30Ni and Fe–37Ni–3Ti. 相似文献
8.
9.
10.
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