全文获取类型
收费全文 | 42152篇 |
免费 | 7011篇 |
国内免费 | 4984篇 |
专业分类
化学 | 28798篇 |
晶体学 | 430篇 |
力学 | 2775篇 |
综合类 | 364篇 |
数学 | 5261篇 |
物理学 | 16519篇 |
出版年
2024年 | 143篇 |
2023年 | 876篇 |
2022年 | 1574篇 |
2021年 | 1620篇 |
2020年 | 1695篇 |
2019年 | 1691篇 |
2018年 | 1480篇 |
2017年 | 1413篇 |
2016年 | 2057篇 |
2015年 | 2041篇 |
2014年 | 2423篇 |
2013年 | 3164篇 |
2012年 | 3732篇 |
2011年 | 3747篇 |
2010年 | 2565篇 |
2009年 | 2547篇 |
2008年 | 2702篇 |
2007年 | 2326篇 |
2006年 | 2139篇 |
2005年 | 1786篇 |
2004年 | 1395篇 |
2003年 | 1120篇 |
2002年 | 1106篇 |
2001年 | 891篇 |
2000年 | 818篇 |
1999年 | 950篇 |
1998年 | 778篇 |
1997年 | 736篇 |
1996年 | 689篇 |
1995年 | 630篇 |
1994年 | 531篇 |
1993年 | 494篇 |
1992年 | 379篇 |
1991年 | 347篇 |
1990年 | 314篇 |
1989年 | 263篇 |
1988年 | 213篇 |
1987年 | 164篇 |
1986年 | 132篇 |
1985年 | 141篇 |
1984年 | 90篇 |
1983年 | 66篇 |
1982年 | 74篇 |
1981年 | 33篇 |
1980年 | 15篇 |
1979年 | 11篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1972年 | 4篇 |
1957年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
In this paper, we study vanishing and splitting results on a complete smooth metric measure space \((M^n,g,\mathrm {e}^{-f}\mathrm {d}v)\) with various negative m-Bakry-Émery Ricci curvature lower bounds in terms of the first eigenvalue \(\lambda _1(\Delta _f)\) of the weighted Laplacian \(\Delta _f\), i.e., \(\mathrm {Ric}_{m,n}\ge -a\lambda _1(\Delta _f)-b\) for \(0<a\le \dfrac{m}{m-1}, b\ge 0\). In particular, we consider three main cases for different a and b with or without conditions on \(\lambda _1(\Delta _f)\). These results are extensions of Dung and Vieira, and weighted generalizations of Li-Wang, Dung-Sung, and Vieira.
相似文献2.
Paired single residue‐transposed Lys‐N and Lys‐C digestions for label‐free identification of N‐terminal and C‐terminal MS/MS peptide product ions: ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry and tandem mass spectrometry for peptide de novo sequencing 下载免费PDF全文
3.
4.
在中国科学技术大学夏季学期的研究型实验课程"化学科研基础训练"中开设"壳聚糖的制备与表征"综合实验,以龙虾壳为原料,通过除蛋白、脱盐、脱色、脱乙酰等一系列反应,制备得到目标产物壳聚糖。运用红外光谱、核磁共振仪、黏度法、滴定等对产品的结构及性能进行表征。 相似文献
5.
Terahertz(THz) wave emission from argon atom in a two-color laser pulses is studied numerically by solving the one-dimensional(1D) time-dependent Schr ¨odinger equation. The THz spectra we obtained include both discontinuous and continuum ones. By using the special basis functions that we previously proposed, our analysis points out that the discontinuous and continuum parts are contributed by bound–bound and continuum–continuum transition of atomic energy levels. Although the atomic wave function is strongly dressed during the interaction with laser fields, our identification for the discontinuous part of the THz wave shows that the transition between highly excited bound states can still be well described by the field-free basis function in the tunneling ionization regime. 相似文献
6.
7.
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
8.
9.
Tuning the Basicity of Cyano‐Containing Ionic Liquids to Improve SO2 Capture through Cyano–Sulfur Interactions 下载免费PDF全文
Dr. Guokai Cui Fengtao Zhang Xiuyuan Zhou Prof. Haoran Li Prof. Jianji Wang Prof. Congmin Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(14):5632-5639
A new approach has been developed to improve SO2 sorption by cyano‐containing ionic liquids (ILs) through tuning the basicity of ILs and cyano–sulfur interaction. Several kinds of cyano‐containing ILs with different basicity were designed, prepared, and used for SO2 capture. The interaction between these cyano‐containing ILs and SO2 was investigated by FTIR and NMR methods. Spectroscopic investigations and quantum chemical calculations showed that dramatic effects on SO2 capacity originate from the basicity of the ILs and enhanced cyano–sulfur interaction. Furthermore, the captured SO2 was easy to release by heating or bubbling N2 through the ILs. This efficient and reversible process, achieved by tuning the basicity of ILs, is an excellent alternative to current technologies for SO2 capture. 相似文献
10.