全文获取类型
收费全文 | 4075篇 |
免费 | 135篇 |
国内免费 | 34篇 |
专业分类
化学 | 2677篇 |
晶体学 | 18篇 |
力学 | 91篇 |
数学 | 531篇 |
物理学 | 927篇 |
出版年
2024年 | 6篇 |
2023年 | 27篇 |
2022年 | 110篇 |
2021年 | 146篇 |
2020年 | 106篇 |
2019年 | 158篇 |
2018年 | 132篇 |
2017年 | 121篇 |
2016年 | 178篇 |
2015年 | 131篇 |
2014年 | 163篇 |
2013年 | 229篇 |
2012年 | 319篇 |
2011年 | 334篇 |
2010年 | 188篇 |
2009年 | 184篇 |
2008年 | 288篇 |
2007年 | 254篇 |
2006年 | 229篇 |
2005年 | 202篇 |
2004年 | 174篇 |
2003年 | 109篇 |
2002年 | 111篇 |
2001年 | 47篇 |
2000年 | 36篇 |
1999年 | 34篇 |
1998年 | 31篇 |
1997年 | 33篇 |
1996年 | 24篇 |
1995年 | 14篇 |
1994年 | 12篇 |
1993年 | 8篇 |
1992年 | 12篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 7篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1975年 | 3篇 |
1972年 | 3篇 |
1971年 | 3篇 |
1967年 | 6篇 |
1966年 | 3篇 |
1964年 | 3篇 |
1962年 | 4篇 |
排序方式: 共有4244条查询结果,搜索用时 0 毫秒
991.
992.
993.
994.
995.
996.
Prof. Dr. Sergey N. Britvin Andrey M. Rumyantsev Dr. Anastasia E. Zobnina Prof. Dr. Marina V. Padkina 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(40):14227-14235
Herein, we report unusual four‐center interactions in the novel cage‐like phosphane, 1,4,7‐triaza‐9‐phosphatricyclo[5.3.2.14,9]tridecane (CAP). This water‐soluble ligand, the first example of a tris(homoadamantane) ring system, can be considered a macrocyclic homologue of the well‐known PTA (1,3,5‐triaza‐7‐phosphaadamantane). However, 31P NMR spectroscopic anomalies of CAP follow those typical for the bi‐/tricyclic atrane systems. Another atrane‐like feature of CAP is the ability of one nitrogen atom to undergo out–in pyramidal inversion. The latter is associated with a substantial decrease in the intracage N?N and P?N distances. Analysis of electron density distribution [molecular electrostatic potential (MESP) and atoms‐in‐molecules (AIM) approaches] suggests that the P and N atoms in the pyramidally inverted CAP derivatives are involved in interactions resulting in accumulation of electron density at the center of the phosphane cage. The latter can reliably explain the stereoelectronic and NMR anomalies of the new ligand. The semi‐flexible CAP cage populates the structural niche between the rigid adamantine skeleton of PTA and flexible atrane systems and can be regarded as an alternative to PTA in aqueous coordination chemistry. 相似文献
997.
Sergey A. Shyshkanov Dr. Nikolai V. Orlov 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(43):15458-15467
Selenium‐based enantiopure chiral chemical probes have been designed in a modular way starting from available amino alcohols. The probes developed were found to be efficient in chemoselective interaction with carboxylic functions of chiral substrates leading to diastereomeric amide formation and in sensing α‐, β‐, and remote (up to seven bonds away from the carboxylic group) chiral centers by using 77Se NMR spectroscopy. As a result, it was possible to determine the enantiomeric ratio of structurally diverse individual chiral acids including polyfunctional compounds and drugs with high accuracy. An approach to analyzing the crude reaction mixtures has been successfully developed by using bifunctional selenium‐ and fluorine‐containing chiral probes. More importantly, it was revealed that, based on the 77Se NMR data obtained, it is possible to obtain primary information about the location and nature of the substituents at the chiral center (chemo‐ and enantiosensing), which can simplify the structural elucidation of complex compounds. The derivatization procedure takes as little as 5 min and can be performed directly in an NMR tube followed by NMR measurements without any isolation and purification steps. 相似文献
998.
Anupama Yadav Cameron Glasscock Leonid Chernyak Igor Lubomirsky Sergey Khodorov 《辐射效应与固体损伤》2016,171(3-4):223-230
The impact of 60Co gamma-irradiation on n-channel AlGaN/GaN high-electron-mobility transistors was studied by means of temperature-dependent electron beam-induced current (EBIC) and cathodoluminescence (CL) techniques. For the doses up to ~250?Gy, an enhancement of minority carrier transport was observed as evident from the EBIC measurements. This enhancement is associated with internal electron irradiation induced by the primary gamma photons. For the doses above ~250?Gy, deterioration in minority carrier transport was explained by carrier scattering on radiation-induced defects. It is shown that calculated activation energy from the EBIC and CL measurements follows exactly the same trend, which implies that the same underlying phenomenon is responsible for observed findings. 相似文献
999.
1000.