全文获取类型
收费全文 | 345663篇 |
免费 | 5325篇 |
国内免费 | 1243篇 |
专业分类
化学 | 188461篇 |
晶体学 | 4620篇 |
力学 | 13916篇 |
综合类 | 12篇 |
数学 | 41705篇 |
物理学 | 103517篇 |
出版年
2020年 | 2399篇 |
2019年 | 2284篇 |
2018年 | 2389篇 |
2017年 | 2305篇 |
2016年 | 4728篇 |
2015年 | 3859篇 |
2014年 | 5124篇 |
2013年 | 15474篇 |
2012年 | 12091篇 |
2011年 | 14814篇 |
2010年 | 9264篇 |
2009年 | 9142篇 |
2008年 | 13697篇 |
2007年 | 13829篇 |
2006年 | 13444篇 |
2005年 | 12263篇 |
2004年 | 10999篇 |
2003年 | 9639篇 |
2002年 | 9397篇 |
2001年 | 10718篇 |
2000年 | 8272篇 |
1999年 | 6510篇 |
1998年 | 5264篇 |
1997年 | 5096篇 |
1996年 | 5219篇 |
1995年 | 4794篇 |
1994年 | 4577篇 |
1993年 | 4406篇 |
1992年 | 4960篇 |
1991年 | 4639篇 |
1990年 | 4359篇 |
1989年 | 4153篇 |
1988年 | 4411篇 |
1987年 | 4116篇 |
1986年 | 3955篇 |
1985年 | 5736篇 |
1984年 | 5784篇 |
1983年 | 4716篇 |
1982年 | 5099篇 |
1981年 | 5135篇 |
1980年 | 4898篇 |
1979年 | 5007篇 |
1978年 | 4998篇 |
1977年 | 4972篇 |
1976年 | 4888篇 |
1975年 | 4788篇 |
1974年 | 4643篇 |
1973年 | 4761篇 |
1972年 | 2699篇 |
1971年 | 2031篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
Haixing Guan Qianwen Zhang Prof. Dr. Patrick J. Walsh Prof. Dr. Jianyou Mao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(13):5210-5215
A unique nickel/organic photoredox co-catalyzed asymmetric reductive cross-coupling between α-chloro esters and aryl iodides is developed. This cross-electrophile coupling reaction employs an organic reductant (Hantzsch ester), whereas most reductive cross-coupling reactions use stoichiometric metals. A diverse array of valuable α-aryl esters is formed under these conditions with high enantioselectivities (up to 94 %) and good yields (up to 88 %). α-Aryl esters represent an important family of nonsteroidal anti-inflammatory drugs. This novel synergistic strategy expands the scope of Ni-catalyzed reductive asymmetric cross-coupling reactions. 相似文献
13.
Laurens Kooijman Dr. Matthias Schuster Christian Baumann Simon Jurt Dr. Frank Löhr Dr. Boris Fürtig Prof. Dr. Peter Güntert Prof. Dr. Oliver Zerbe 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(47):21151-21158
To achieve efficient proton pumping in the light-driven proton pump bacteriorhodopsin (bR), the protein must be tightly coupled to the retinal to rapidly convert retinal isomerization into protein structural rearrangements. Methyl group dynamics of bR embedded in lipid nanodiscs were determined in the dark-adapted state, and were found to be mostly well ordered at the cytosolic side. Methyl groups in the M145A mutant of bR, which displays only 10 % residual proton pumping activity, are less well ordered, suggesting a link between side-chain dynamics on the cytosolic side of the bR cavity and proton pumping activity. In addition, slow conformational exchange, attributed to low frequency motions of aromatic rings, was indirectly observed for residues on the extracellular side of the bR cavity. This may be related to reorganization of the water network. These observations provide a detailed picture of previously undescribed equilibrium dynamics on different time scales for ground-state bR. 相似文献
14.
The influence of different referencing methods on the accuracy of δ13C value measurement of ethanol fuel by gas chromatography/combustion/isotope ratio mass spectrometry
下载免费PDF全文
![点击此处可从《Rapid communications in mass spectrometry : RCM》网站下载免费的PDF全文](/ch/ext_images/free.gif)
15.
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
16.
17.
We study the full counting statistics of transport electrons through a semiconductor two-level quantum dot with Rashba spin–orbit (SO) coupling, which acts as a nonabelian gauge field and thus induces the electron transition between two levels along with the spin flip. By means of the quantum master equation approach, shot noise and skewness are obtained at finite temperature with two-body Coulomb interaction. We particularly demonstrate the crucial effect of SO coupling on the super-Poissonian fluctuation of transport electrons, in terms of which the SO coupling can be probed by the zero-frequency cumulants. While the charge currents are not sensitive to the SO coupling. 相似文献
18.
19.
20.