全文获取类型
收费全文 | 19076篇 |
免费 | 3469篇 |
国内免费 | 2985篇 |
专业分类
化学 | 15300篇 |
晶体学 | 269篇 |
力学 | 1028篇 |
综合类 | 249篇 |
数学 | 2146篇 |
物理学 | 6538篇 |
出版年
2024年 | 45篇 |
2023年 | 354篇 |
2022年 | 548篇 |
2021年 | 638篇 |
2020年 | 857篇 |
2019年 | 946篇 |
2018年 | 704篇 |
2017年 | 601篇 |
2016年 | 991篇 |
2015年 | 1008篇 |
2014年 | 1165篇 |
2013年 | 1423篇 |
2012年 | 1698篇 |
2011年 | 1698篇 |
2010年 | 1253篇 |
2009年 | 1199篇 |
2008年 | 1316篇 |
2007年 | 1210篇 |
2006年 | 1045篇 |
2005年 | 952篇 |
2004年 | 825篇 |
2003年 | 734篇 |
2002年 | 881篇 |
2001年 | 784篇 |
2000年 | 492篇 |
1999年 | 463篇 |
1998年 | 287篇 |
1997年 | 251篇 |
1996年 | 213篇 |
1995年 | 181篇 |
1994年 | 131篇 |
1993年 | 108篇 |
1992年 | 107篇 |
1991年 | 103篇 |
1990年 | 94篇 |
1989年 | 47篇 |
1988年 | 41篇 |
1987年 | 28篇 |
1986年 | 29篇 |
1985年 | 24篇 |
1984年 | 23篇 |
1983年 | 13篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1975年 | 1篇 |
1959年 | 2篇 |
1936年 | 3篇 |
1909年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
2.
Zhang Bing Yang Jie-qin Liu Ying Hu Bin Yang Yang Zhao Li Lu Qiang 《Cellulose (London, England)》2022,29(12):6565-6578
Cellulose - Heating is essential in various biomass pre-treatments and thermal conversion processes. It is of practical significance to study the characteristics of cellulose-lignin and... 相似文献
3.
Hua Saixiang Zhu Huichao Wang Xiao Wu Mingyuan Wu Qingyun Liu Jiuyi Yang Jianjun Zhang Jianan 《Cellulose (London, England)》2022,29(13):7465-7475
Cellulose - Ultraviolet (UV) protective cotton fabric is a convenient and reliable way to protect human body from sunlight. Herein, a polymerizable UV-absorber,... 相似文献
4.
Ruirui Xu Kun Wang Haoying Liu Prof. Dr. Weijun Tang Dr. Huaming Sun Prof. Dr. Dong Xue Prof. Dr. Jianliang Xiao Prof. Dr. Chao Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(49):22143-22148
A ruthenium-catalyzed formal anti-Markovnikov hydroamination of allylic alcohols for the synthesis of chiral γ-amino alcohols is presented. Proceeding via an asymmetric hydrogen-borrowing process, the catalysis allows racemic secondary allylic alcohols to react with various amines, affording enantiomerically enriched chiral γ-amino alcohols with broad substrate scope and excellent enantioselectivities (68 examples, up to >99 % ee). 相似文献
5.
Cavitation erosion is caused in solids exposed to strong pressure waves developing in an adjacent fluid field. The knowledge of the transient distribution of stresses in the solid is important to understand the cause of damaging by comparisons with breaking points of the material. The modeling of this problem requires the coupling of the models for the fluid and the solid. For this purpose, we use a strategy based on the solution of coupled Riemann problems that has been originally developed for the coupling of 2 fluids. This concept is exemplified for the coupling of a linear elastic structure with an ideal gas. The coupling procedure relies on the solution of a nonlinear equation. Existence and uniqueness of the solution is proven. The coupling conditions are validated by means of quasi‐1D problems for which an explicit solution can be determined. For a more realistic scenario, a 2D application is considered where in a compressible single fluid, a hot gas bubble at low pressure collapses in a cold gas at high pressure near an adjacent structure. 相似文献
6.
7.
The Effect of the Spacer of Bis(biurea) Ligands on the Structure of A2L3‐type (A=anion) Phosphate Complexes 下载免费PDF全文
Prof. Biao Wu Dr. Shaoguang Li Prof. Yibo Lei Prof. Huaiming Hu Dr. Nader de Sousa Amadeu Prof. Dr. Christoph Janiak Dr. Jennifer S. Mathieson Dr. De‐Liang Long Prof. Leroy Cronin Prof. Xiao‐Juan Yang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2588-2593
By tuning the length and rigidity of the spacer of bis(biurea) ligands L, three structural motifs of the A2L3 complexes (A represents anion, here orthophosphate PO43?), namely helicate, mesocate, and mono‐bridged motif, have been assembled by coordination of the ligand to phosphate anion. Crystal structure analysis indicated that in the three complexes, each of the phosphate ions is coordinated by twelve hydrogen bonds from six surrounding urea groups. The anion coordination properties in solution have also been studied. The results further demonstrate the coordination behavior of phosphate ion, which shows strong tendency for coordination saturation and geometrical preference, thus allowing for the assembly of novel anion coordination‐based structures as in transition‐metal complexes. 相似文献
8.
We investigate terahertz radiation(T-rays) from a pentacene organic diode at room temperature. The quantum chemistry calculation for frequency-related Huang–Rhys factor of pentacene is also carried out. The results demonstrate that the T-rays can come from a bending vibration of pentacene skeleton after the energy of pentacene exciton transferring to the vibrational excited state via electron–phonon coupling. Frequency and natural bond orbital analytics of pentacene and its derivatives are performed in order to explain the result and develop new materials to get higher emission. This work provides a new way to produce T-rays with a simple device at room temperature. 相似文献
9.
10.
This study is concerned with a new,explicit approach by means of which forms of the large strain elastic potential for multiaxial rubberlike elasticity may be obtained based on data for a single deformation mode.As a departure from usual studies,here for the first time errors may be estimated and rendered minimal for all possible deformation modes and,furthermore,failure behavior may be incorporated.Numerical examples presented are in accurate agreement with Treloar's well-known data. 相似文献