全文获取类型
收费全文 | 3779篇 |
免费 | 584篇 |
国内免费 | 585篇 |
专业分类
化学 | 2952篇 |
晶体学 | 61篇 |
力学 | 139篇 |
综合类 | 41篇 |
数学 | 488篇 |
物理学 | 1267篇 |
出版年
2023年 | 63篇 |
2022年 | 94篇 |
2021年 | 98篇 |
2020年 | 142篇 |
2019年 | 157篇 |
2018年 | 138篇 |
2017年 | 121篇 |
2016年 | 143篇 |
2015年 | 167篇 |
2014年 | 214篇 |
2013年 | 265篇 |
2012年 | 317篇 |
2011年 | 376篇 |
2010年 | 275篇 |
2009年 | 302篇 |
2008年 | 306篇 |
2007年 | 272篇 |
2006年 | 245篇 |
2005年 | 188篇 |
2004年 | 148篇 |
2003年 | 122篇 |
2002年 | 130篇 |
2001年 | 100篇 |
2000年 | 104篇 |
1999年 | 76篇 |
1998年 | 45篇 |
1997年 | 40篇 |
1996年 | 50篇 |
1995年 | 41篇 |
1994年 | 49篇 |
1993年 | 37篇 |
1992年 | 37篇 |
1991年 | 20篇 |
1990年 | 18篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1966年 | 1篇 |
1957年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有4948条查询结果,搜索用时 15 毫秒
1.
In this paper,we explore two conjectures about Rademacher sequences.Let(εi)be a Rademacher sequence,i.e.,a sequence of independent{-1,1}-valued symmetric random variables.Set Sn=aiε1+…+anεn for a=(a1,…,an)∈Rn.The first con.jecture says that P(|Sn|≤‖a‖)>1/2 for all a∈Rn and n∈N.The second conjecture says that P(|Sn|>‖a‖)≥7/32 for all a∈Rn and n∈N.Regarding the first conjecture,we present several new equivalent formulations.These include a topological view,a combinatorial version and a strengthened version of the conjecture.Regarding the second conjecture,we prove that it holds true when n<7. 相似文献
2.
Anh Ha Lan Nhan Dang Duc Frew Russell Quynh Tran Minh 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(9):3613-3621
Journal of Radioanalytical and Nuclear Chemistry - This research aimed to authenticate the geographical origin of imported fresh apples using isotopic techniques. The results show that the... 相似文献
3.
Bin Ran Chaozhan Chen Bo Liu Minbo Lan Huaying Chen Yonggang Zhu 《Electrophoresis》2022,43(20):2033-2043
The detection of cancer biomarkers is of great significance for the early screening of cancer. Detecting the content of sarcosine in blood or urine has been considered to provide a basis for the diagnosis of prostate cancer. However, it still lacks simple, high-precision and wide-ranging sarcosine detection methods. In this work, a Ti3C2TX/Pt–Pd nanocomposite with high stability and excellent electrochemical performance has been synthesized by a facile one-step alcohol reduction and then used on a glassy carbon electrode (GCE) with sarcosine oxidase (SOx) to form a sarcosine biosensor (GCE/Ti3C2TX/Pt–Pd/SOx). The prominent electrocatalytic activity and biocompatibility of Ti3C2TX/Pt–Pd enable the SOx to be highly active and sensitive to sarcosine. Under the optimized conditions, the prepared biosensor has a wide linear detection range to sarcosine from 1 to 1000 µM with a low limit of detection of 0.16 µM (S/N = 3) and a sensitivity of 84.1 µA/mM cm2. Besides, the reliable response in serum samples shows its potential in the early diagnosis of prostate cancer. More importantly, the successful construction and application of the amperometric biosensor based on Ti3C2TX/Pt–Pd will provide a meaningful reference for detecting other cancer biomarkers. 相似文献
4.
5.
Guo Lan Guan Yali Liu Peng Gao Linghuan Wang Zhifu Huang Shengli Peng Liang Zhao Zhiyu 《Cellulose (London, England)》2022,29(3):1315-1330
Cellulose - Extracellular vesicles are membrane-packed entities that are involved in various physiological and pathological processes. Recently, the role of exosomes and microvesicles in... 相似文献
6.
Crystallography Reports - A di-nuclear uranyl complex with the formula of [(UO2)2(L)4(H2O)2]?4H2O (1) (HL = quinoline-6-carboxylic acid) was synthesized hydrothermally and characterized by... 相似文献
8.
Marcio David Bocelli Deyber Arley Vargas Medina Julie Paulin García Rodriguez Fernando Mauro Lanças Álvaro José Santos-Neto 《Electrophoresis》2022,43(15):1567-1576
Dynamic single-drop microextraction (SDME) was automatized employing an Arduino-based lab-made Cartesian robot and implemented to determine parabens in wastewater samples in combination with liquid chromatography–tandem mass spectrometry. A dedicated Arduino sketch controls the auto-performance of all the stages of the SDME process, including syringe filling, drop exposition, solvent recycling, and extract collection. Univariate and multivariate experiments investigated the main variables affecting the SDME performance, including robot-dependent and additional operational parameters. Under selected conditions, limit of detections were established at 0.3 µg/L for all the analytes, and the method provided linear responses in the range between 0.6 and 10 µg/L, with adequate reproducibility, measured as intraday relative standard deviations (RSDs) between 5.54% and 17.94%, (n = 6), and inter-days RSDs between 8.97% and 16.49% (n = 9). The robot-assisted technique eased the control of dynamic SDME, making the process more feasible, robust, and reliable so that the developed setup demonstrated to be a competitive strategy for the automated extraction of organic pollutants from water samples. 相似文献
9.
A Cu(II) coordination polymer (CP) (that is, [Cu2(OH)(H2O)2(cbca)·2H2O]n (1)) has been obtained with the reaction between Cu(II) salt and 4′-(1-carboxyethoxy)-[1,1′-biphenyl]-3,5-dicarboxylic acid (H3cbca), a semi-rigid tricarboxylic acid ligand under the hydrothermal reaction condition. Prevention activity of the new compound on hypotension after anesthesia surgery was evaluated and the related mechanism was researched at the same time. The noninvasive blood pressure monitor was firstly conducted to measure the blood pressure of the animal after compound treatment. Besides, the real time RT-PCR assay was also used to determine theα receptor relative expression on vascular endothelial cells after compound treatment. 相似文献