全文获取类型
收费全文 | 221185篇 |
免费 | 30947篇 |
国内免费 | 21860篇 |
专业分类
化学 | 113260篇 |
晶体学 | 1854篇 |
力学 | 11477篇 |
综合类 | 1091篇 |
数学 | 21041篇 |
物理学 | 64016篇 |
无线电 | 61253篇 |
出版年
2024年 | 806篇 |
2023年 | 4678篇 |
2022年 | 6164篇 |
2021年 | 7859篇 |
2020年 | 7656篇 |
2019年 | 7264篇 |
2018年 | 6395篇 |
2017年 | 6217篇 |
2016年 | 9047篇 |
2015年 | 9536篇 |
2014年 | 11585篇 |
2013年 | 15154篇 |
2012年 | 17794篇 |
2011年 | 18153篇 |
2010年 | 13076篇 |
2009年 | 13036篇 |
2008年 | 13834篇 |
2007年 | 12589篇 |
2006年 | 11905篇 |
2005年 | 10450篇 |
2004年 | 7693篇 |
2003年 | 6476篇 |
2002年 | 6000篇 |
2001年 | 5157篇 |
2000年 | 4738篇 |
1999年 | 5140篇 |
1998年 | 4556篇 |
1997年 | 3923篇 |
1996年 | 4132篇 |
1995年 | 3497篇 |
1994年 | 3228篇 |
1993年 | 2672篇 |
1992年 | 2452篇 |
1991年 | 2119篇 |
1990年 | 1663篇 |
1989年 | 1267篇 |
1988年 | 1017篇 |
1987年 | 811篇 |
1986年 | 744篇 |
1985年 | 669篇 |
1984年 | 493篇 |
1983年 | 396篇 |
1982年 | 326篇 |
1981年 | 251篇 |
1980年 | 186篇 |
1979年 | 127篇 |
1978年 | 108篇 |
1976年 | 107篇 |
1974年 | 115篇 |
1973年 | 108篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
53.
Highly dispersed palladium nanoclusters incorporated in amino‐functionalized silica spheres for the selective hydrogenation of succinic acid to γ‐butyrolactone 下载免费PDF全文
Highly dispersed palladium nanoclusters incorporated on amino‐functionalized silica sphere surfaces (Pd/SiO2‐NH2) were fabricated by a simple one‐pot synthesis utilizing 3‐(2‐aminoethylamino)propyltrimethoxysilane (AAPTS) as coordinating agent. Uniform palladium nanoclusters with an average size of 1.1 nm can be obtained during the co‐condensation of tetraethyl orthosilicate and AAPTS owing to the strong interaction between palladium species and amino groups in AAPTS. The palladium particle size can be controlled by addition of AAPTS and plays a significant role in the catalytic performance. The Pd/SiO2‐NH2 catalyst exhibits high catalytic activity for succinic acid hydrogenation with 100% conversion and 94% selectivity towards γ‐butyrolactone using 1,4‐dioxane as solvent at 240°C and 60 bar for 4 h. Moreover, the Pd/SiO2‐NH2 catalyst is robust and readily reusable without loss of its catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
54.
55.
Dr. Wan‐Ling Liu Ni‐Shin Yang Ya‐Ting Chen Stephen Lirio Cheng‐You Wu Prof. Chia‐Her Lin Prof. Hsi‐Ya Huang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(1):115-119
A green and sustainable strategy synthesizes clinical medicine warfarin anticoagulant by using lipase‐supported metal–organic framework (MOF) bioreactors (see scheme). These findings may be beneficial for future studies in the industrial production of chemical, pharmaceutical, and agrochemical precursors. 相似文献
56.
We propose a system of time-division multiplexing(TDM) and spatial frequency-division multiplexing(SFDM). Extrinsic Fabry–Perot interferometric sensors are applied to detect weak acoustic signals. The broadband source is employed, the light from it is modulated by a pulse signal sequence and is efficiently amplified by semiconductor optical amplifiers. Experimental results show that the equivalent noise pressure spectrum level is-97.2 d B re 1 rad/√Hz below 1250 Hz, and the cross talk between two sensors in one TDM channel is-32.7 d B with a cavity length difference of 60 μm. The number of sensors in this multiplexing system can theoretically reach 160. 相似文献
57.
Dr. Jun Zeng Dr. Zhichao Wang Dr. Xin Huang Dr. Sabine S. Eckstein Prof. Dr. Xiaohui Lin Prof. Dr. Hailong Piao Prof. Dr. Cora Weigert Dr. Peiyuan Yin Prof. Dr. Rainer Lehmann Prof. Dr. Guowang Xu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(21):5427-5432
Mass spectrometry (MS) driven metabolomics is a frequently used tool in various areas of life sciences; however, the analysis of polar metabolites is less commonly included. In general, metabolomic analyses lead to the detection of the total amount of all covered metabolites. This is currently a major limitation with respect to metabolites showing high turnover rates, but no changes in their concentration. Such metabolites and pathways could be crucial metabolic nodes (e.g., potential drug targets in cancer metabolism). A stable-isotope tracing capillary electrophoresis–mass spectrometry (CE-MS) metabolomic approach was developed to cover both polar metabolites and isotopologues in a non-targeted way. An in-house developed software enables high throughput processing of complex multidimensional data. The practicability is demonstrated analyzing [U-13C]-glucose exposed prostate cancer and non-cancer cells. This CE-MS-driven analytical strategy complements polar metabolite profiles through isotopologue labeling patterns, thereby improving not only the metabolomic coverage, but also the understanding of metabolism. 相似文献
58.
In this paper, we propose a sufficient and necessary condition for the boundedness of all the solutions for the equation with the critical situation that on g and p, where , is periodic and is bounded. 相似文献
59.
60.