全文获取类型
收费全文 | 4622篇 |
免费 | 178篇 |
国内免费 | 56篇 |
专业分类
化学 | 2962篇 |
晶体学 | 41篇 |
力学 | 150篇 |
综合类 | 2篇 |
数学 | 816篇 |
物理学 | 885篇 |
出版年
2023年 | 27篇 |
2022年 | 36篇 |
2021年 | 59篇 |
2020年 | 56篇 |
2019年 | 59篇 |
2018年 | 65篇 |
2017年 | 29篇 |
2016年 | 98篇 |
2015年 | 87篇 |
2014年 | 117篇 |
2013年 | 233篇 |
2012年 | 295篇 |
2011年 | 332篇 |
2010年 | 171篇 |
2009年 | 188篇 |
2008年 | 291篇 |
2007年 | 283篇 |
2006年 | 265篇 |
2005年 | 238篇 |
2004年 | 213篇 |
2003年 | 184篇 |
2002年 | 137篇 |
2001年 | 103篇 |
2000年 | 109篇 |
1999年 | 71篇 |
1998年 | 63篇 |
1997年 | 40篇 |
1996年 | 88篇 |
1995年 | 53篇 |
1994年 | 54篇 |
1993年 | 56篇 |
1992年 | 48篇 |
1991年 | 44篇 |
1990年 | 35篇 |
1989年 | 25篇 |
1988年 | 31篇 |
1987年 | 33篇 |
1986年 | 24篇 |
1985年 | 58篇 |
1984年 | 35篇 |
1983年 | 32篇 |
1982年 | 30篇 |
1981年 | 44篇 |
1980年 | 33篇 |
1979年 | 30篇 |
1978年 | 37篇 |
1977年 | 29篇 |
1975年 | 29篇 |
1974年 | 40篇 |
1973年 | 23篇 |
排序方式: 共有4856条查询结果,搜索用时 343 毫秒
1.
miRNA (miR)-155 is a potential biomarker for breast cancers. We aimed at developing a nanosensor for miR-155 detection by integrating hybridization chain reaction (HCR) and silver nanoclusters (AgNCs). HCR serves as an enzyme-free and isothermal amplification method, whereas AgNCs provide a built-in fluorogenic detection probe that could simplify the downstream analysis. The two components were integrated by adding a nucleation sequence of AgNCs to the hairpin of HCR. The working principle was based on the influence of microenvironment towards the hosted AgNCs, whereby unfolding of hairpin upon HCR has manipulated the distance between the hosted AgNCs and cytosine-rich toehold region of hairpin. As such, the dominant emission of AgNCs changed from red to yellow in the absence and presence of miR-155, enabling a ratiometric measurement of miR with high sensitivity. The limit of detection (LOD) of our HCR-AgNCs nanosensor is 1.13 fM in buffered solution. We have also tested the assay in diluted serum samples, with comparable LOD of 1.58 fM obtained. This shows the great promise of our HCR-AgNCs nanosensor for clinical application. 相似文献
2.
Chi-Kwong Li Ming-Cheng Tsai Ya-Shu Wang Ngai-Ching Wong 《Journal of Mathematical Analysis and Applications》2022,505(2):125522
Let L be an additive map between (real or complex) matrix algebras sending Hermitian idempotent matrices to Hermitian idempotent matrices. We show that there are nonnegative integers with and an unitary matrix U such that We also extend this result to the (complex) von Neumann algebra setting, and provide a supplement to the Dye-Bunce-Wright Theorem asserting that every additive map of Hermitian idempotents extends to a Jordan ?-homomorphism. 相似文献
3.
The coordination chemistry of beryllium with particular emphasis on chelates under physiological or near physiological conditions is surveyed. Hard donors such as oxygen are emphasized; equilibrium data and formation constants are reported as an indication of the strength of the complex. 相似文献
4.
A new speckle shearing interferometer with simple setup is proposed. The interferometer can be converted easily from a speckle referenced speckle pattern interferometer into a speckle shearing interferometer and vice versa. A beamsplitter and a mirror are used to generate the shear. The amount of shear can be adjusted by simply rotating the mirror. The costs involved are low and it is particularly useful for fast inspection in non-destructive testing of structural integrity. Both the theoretical studies of the method of measurement and the experimental results are presented. 相似文献
5.
V. Bena Jothy T. Vijayakumar D. Sajan V. S. Jayakumar I. Hubert Joe 《Laser Physics》2006,16(8):1242-1252
Single crystals of sarcosinium oxalate monohydrate (SOM) are grown by the slow-evaporation technique at ambient temperature, and vibrational spectroscopic analysis is carried out using NIR-FT Raman, FT-IR, and SERS spectra. The normal mode frequencies and corresponding vibrational analysis of SOM are examined theoretically using the Gaussian’98 set of quantum chemical codes. The two bands present in the SOM ν C=O region, clearly observed in the Raman spectrum, are assigned to “free” and “bonded” carbonyl groups with the hydrogen atom. Vibrational analysis indicates the presence of C-H—O hydrogen bonding interaction producing a blueshift of the C-H stretching frequency. 相似文献
6.
The orientation-selective growth of LaNiO3 films on Si(100) by pulsed laser deposition using a MgO buffer 总被引:4,自引:0,他引:4
X.Y. Chen K.H. Wong C.L. Mak J.M. Liu X.B. Yin M. Wang Z.G. Liu 《Applied Physics A: Materials Science & Processing》2002,75(4):545-549
Highly (100)-oriented, (110)-oriented and polycrystalline LaNiO3 (LNO) films were successfully prepared on Si(100) using an oriented MgO film as a buffer. It was somewhat surprising to find
that that the orientation relation between the LNO film and the corresponding MgO buffer was: LNO(100)\MgO(110), LNO(110)\MgO(111)
and LNO(polycrystalline)\MgO(100). The crystalline quality of the LNO films was shown to be sensitive to the preparation conditions
of the MgO buffer. The film surface was very smooth, without micrometer-sized droplets being observed. All LNO films were
of metallic conductivity, with a room-temperature resistivities of approximately 250, 280 and 420 μΩ cm for the (110)-oriented,
(100)-oriented and polycrystalline LNO, respectively.
Received: 2 April 2001 / Accepted: 23 October 2001 / Published online: 3 June 2002 相似文献
7.
Equilibrium Problems with Applications to Eigenvalue Problems 总被引:5,自引:0,他引:5
In this paper, we consider equilibrium problems and introduce the concept of (S)+ condition for bifunctions. Existence results for equilibrium problems with the (S)+ condition are derived. As special cases, we obtain several existence results for the generalized nonlinear variational inequality studied by Ding and Tarafdar (Ref. 1) and the generalized variational inequality studied by Cubiotti and Yao (Ref. 2). Finally, applications to a class of eigenvalue problems are given. 相似文献
8.
Ionel Rosenthal Joe Z. Sostaric Peter Riesz 《Research on Chemical Intermediates》2004,30(7-8):685-701
Sonochemistry and photochemistry are initiated by high-energy transient species, which may be prone to mutual interaction. Electronic excitation of solutes by energy transfer from high energy species generated in collapsing bubbles is already supported by experimental evidence. The rates of photochemical reactions can be affected by ultrasound-induced mixing of liquids caused by microstreaming near pulsating cavitation bubbles and shockwaves due to bubble collapse. This may not only improve light absorption but also modify the pathway of reaction by increasing the contact between reagents. Finally, one may speculate about a potentially new chemistry of photoexcited solutes under the extreme conditions inside cavitation microreactors. This work reviews research on the excitation of solutes by sonoluminescence, the combined effects of ultrasound and light on liquid systems and the effect of ultrasound on photocatalytic reactions. 相似文献
9.
10.