全文获取类型
收费全文 | 60647篇 |
免费 | 9551篇 |
国内免费 | 7521篇 |
专业分类
化学 | 34070篇 |
晶体学 | 659篇 |
力学 | 2507篇 |
综合类 | 480篇 |
数学 | 4970篇 |
物理学 | 17109篇 |
无线电 | 17924篇 |
出版年
2024年 | 240篇 |
2023年 | 1427篇 |
2022年 | 1866篇 |
2021年 | 2352篇 |
2020年 | 2234篇 |
2019年 | 2215篇 |
2018年 | 1938篇 |
2017年 | 2024篇 |
2016年 | 2636篇 |
2015年 | 2909篇 |
2014年 | 3527篇 |
2013年 | 4370篇 |
2012年 | 5332篇 |
2011年 | 5353篇 |
2010年 | 4056篇 |
2009年 | 3964篇 |
2008年 | 4231篇 |
2007年 | 3892篇 |
2006年 | 3705篇 |
2005年 | 3018篇 |
2004年 | 2182篇 |
2003年 | 1881篇 |
2002年 | 1702篇 |
2001年 | 1434篇 |
2000年 | 1270篇 |
1999年 | 1237篇 |
1998年 | 939篇 |
1997年 | 866篇 |
1996年 | 760篇 |
1995年 | 719篇 |
1994年 | 680篇 |
1993年 | 509篇 |
1992年 | 438篇 |
1991年 | 403篇 |
1990年 | 344篇 |
1989年 | 233篇 |
1988年 | 183篇 |
1987年 | 153篇 |
1986年 | 133篇 |
1985年 | 103篇 |
1984年 | 70篇 |
1983年 | 47篇 |
1982年 | 48篇 |
1981年 | 27篇 |
1980年 | 22篇 |
1979年 | 10篇 |
1978年 | 5篇 |
1971年 | 4篇 |
1957年 | 8篇 |
1936年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Junyu Chen Yuze Li Yuming Jiang Liucheng Mao Mi Lai Lixia Jiang Huihui Liu Zongxiu Nie 《Advanced functional materials》2021,31(52):2106743
Cancer remains an intractable medical problem. Rapid diagnosis and identification of cancer are critical to differentiate it from nonmalignant diseases. High-throughput biofluid metabolic analysis has potential for cancer diagnosis. Nevertheless, the present metabolite analysis method does not meet the demand for high-throughput screening of diseases. Herein, a high-throughput, cost-effective, and noninvasive urine metabolic profiling method based on TiO2/MXene-assisted laser desorption/ionization mass spectrometry (LDI-MS) is presented for the efficient screening of bladder cancer (BC) and nonmalignant urinary disease. Combined with machine learning, TiO2/MXene-assisted LDI-MS enables high diagnostic accuracy (96.8%) for the classification of patient groups (including 47 BC and 46 ureteral calculus (UC) patients) from healthy controls (113 cases). In addition, BC patients can also be identified from noncancerous UC individuals with an accuracy of 88.3% in the independent test cohort. Furthermore, metabolite variations between BC and UC individuals are investigated based on relative quantification, and related pathways are also discussed. These results suggest that this method, based on urine metabolic patterns, provides a potential tool for rapidly distinguishing urinary diseases and it may pave the way for precision medicine. 相似文献
32.
Wang Hay Kan Chenxi Wei Dongchang Chen Tao Bo Bao‐Tian Wang Yan Zhang Yangchao Tian Jun‐Sik Lee Yijin Liu Guoying Chen 《Advanced functional materials》2019,29(17)
Lithium‐rich disordered rock‐salt oxides have attracted great interest owing to their promising performance as Li‐ion battery cathodes. While experimental and theoretical efforts are critical in advancing this class of materials, a fundamental understanding of key property changes upon Li extraction is largely missing. In the present study, single‐crystal synthesis of a new disordered rock‐salt cathode material, Li1.3Ta0.3Mn0.4O2 (LTMO), and its use as a model compound to investigate Li concentration–driven evolution of local cationic ordering, charge compensation, and chemical distribution are reported. Through the combined use of 2D and 3D X‐ray nanotomography, it is shown that Li removal accompanied by oxygen oxidation is correlated with the development of morphological defects such as particle cracking. Chemical heterogeneity, quantified by subparticle level distribution of Mn valence state, is minimal during Mn redox, which drastically increases upon the formation of cracks during oxygen redox. Density functional theory and bond valence sum mismatch calculations reveal the presence of local short‐range ordering in the pristine oxide, which gradually disappears along with the extraction of Li. The study suggests that with cycling the transformation into true cation–disordered state can be expected, which likely impacts the voltage profile and obtainable energy density of the oxide cathodes. 相似文献
34.
社会经济的快速发展促进了科学技术水平的显著提升,社会生产生活各个领域当中对计算机网络的应用程度不断提升,当前,网络已经成为了人们日常生活与工作的重要组成部分。为此,加强对网络安全等因素影响研究就显得格外重要。网络环境关系着用户的使用质量,更加影响人们的工作效率,加强对网络安全技术的研究时解决相关问题的核心内容。本文针对网络安全威胁因素以及常见的网络安全技术进行了简要分析。 相似文献
35.
In this Letter,a novel system for adaptively correcting the phase of a dynamic multimode beam is proposed.While using merely one spatial light modulator,the phase measurement of the first-order diffraction pattern and the correction of the zeroth diffraction order are simultaneously realized.The real-time experimental result is obtained at a control rate of 10 Hz.The power-in-the-bucket value is improved from 38.5%to 61.8%,even with fundamental mode content that is consistently below 30%.To the best of our knowledge,this is the first implementation of real-time adaptive correction of the entire multimode beam. 相似文献
36.
37.
In this paper,we investigate the non-autonomous Hamilton-Jacobi equation ■ where H is 1-periodic with respect to t and M is a compact Riemannian manifold without boundary.We obtain the viscosity solution denoted by T_(t_0)~tφ(x) and show T_(t_0)~tφ(x) converges uniformly to a time-periodic viscosity solution u~*(x,t) of ?_tu+H(t,x,?_xu,u)=0. 相似文献
38.
Dr. Masaru Kondo Dr. Shinobu Takizawa Yuzhao Jiang Prof. Dr. Hiroaki Sasai 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(42):9866-9869
The Mills reaction and cyclization of readily available 2-aminobenzyl alcohols and nitrosobenzenes using thionyl bromide provided 2H-indazoles in up to 88 % yields. In the metal-free process, acetic acid played a crucial role for the both Mills reaction and cyclization. A brominated 2H-indazole could also be obtained through the one-pot sequence. 相似文献
39.
40.