全文获取类型
收费全文 | 14810篇 |
免费 | 2297篇 |
国内免费 | 1429篇 |
专业分类
化学 | 10752篇 |
晶体学 | 181篇 |
力学 | 875篇 |
综合类 | 80篇 |
数学 | 1842篇 |
物理学 | 4806篇 |
出版年
2024年 | 16篇 |
2023年 | 318篇 |
2022年 | 347篇 |
2021年 | 508篇 |
2020年 | 707篇 |
2019年 | 606篇 |
2018年 | 523篇 |
2017年 | 447篇 |
2016年 | 724篇 |
2015年 | 759篇 |
2014年 | 777篇 |
2013年 | 1132篇 |
2012年 | 1308篇 |
2011年 | 1306篇 |
2010年 | 853篇 |
2009年 | 867篇 |
2008年 | 1012篇 |
2007年 | 852篇 |
2006年 | 776篇 |
2005年 | 736篇 |
2004年 | 532篇 |
2003年 | 430篇 |
2002年 | 377篇 |
2001年 | 327篇 |
2000年 | 275篇 |
1999年 | 297篇 |
1998年 | 200篇 |
1997年 | 148篇 |
1996年 | 192篇 |
1995年 | 175篇 |
1994年 | 142篇 |
1993年 | 129篇 |
1992年 | 107篇 |
1991年 | 88篇 |
1990年 | 91篇 |
1989年 | 71篇 |
1988年 | 65篇 |
1987年 | 48篇 |
1986年 | 45篇 |
1985年 | 43篇 |
1984年 | 41篇 |
1983年 | 17篇 |
1982年 | 16篇 |
1981年 | 19篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1976年 | 10篇 |
1975年 | 11篇 |
1971年 | 7篇 |
1969年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
Wei Ouyang Prof. Jongyoon Han 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(27):11074-11081
Nucleic acid amplification tests (NAATs)integrated on a chip hold great promise for point-of-care diagnostics. Currently, nucleic acid (NA) purification remains time-consuming and labor-intensive, and it takes extensive efforts to optimize the amplification chemistry. Using selective electrokinetic concentration, we report one-step, liquid-phase NA purification that is simpler and faster than conventional solid-phase extraction. By further re-concentrating NAs and performing polymerase chain reaction (PCR) in a microfluidic chamber, our platform suppresses non-specific amplification caused by non-optimal PCR designs. We achieved the detection of 5 copies of M. tuberculosis genomic DNA (equaling 0.3 cell) in real biofluids using both optimized and non-optimal PCR designs, which is 10- and 1000-fold fewer than those of the standard bench-top method, respectively. By simplifying the workflow and shortening the development cycle of NAATs, our platform may find use in point-of-care diagnosis. 相似文献
22.
Huadong Yuan Prof. Jianwei Nai Dr. Yongjin Fang Gongxun Lu Prof. Xinyong Tao Prof. Xiong Wen Lou 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(37):15973-15977
The growth of Li dendrites hinders the practical application of lithium metal anodes (LMAs). In this work, a hollow nanostructure, based on hierarchical MoS2 coated hollow carbon particles preloaded with sulfur (C@MoS2/S), was designed to modify the LMA. The C@MoS2 hollow nanostructures serve as a good scaffold for repeated Li plating/stripping. More importantly, the encapsulated sulfur could gradually release lithium polysulfides during the Li plating/stripping, acting as an effective additive to promote the formation of a mosaic solid electrolyte interphase layer embedded with crystalline hybrid lithium-based components. These two factors together effectively suppress the growth of Li dendrites. The as-modified LMA shows a high Coulombic efficiency of 98 % over 500 cycles at the current density of 1 mA cm−2. When matched with a LiFePO4 cathode, the assembled full cell displays a highly improved cycle life of 300 cycles, implying the feasibility of the proposed LMA. 相似文献
23.
Dr. Si-Yong Qin Yan Jiang Dr. Han Sun Han Liu Prof. Ai-Qing Zhang Prof. Xinxiang Lei 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(39):17245-17251
Residual dipolar coupling (RDC), a robust anisotropic NMR parameter for structural elucidation of organic molecules, is only accessible in an anisotropic environment. Herein, we introduce a novel alignment medium based on the molecular self-assembly of oligopeptide amphiphile (OPA). This medium is compatible with different intermediate and polar solvent systems, such as CD3OD, [D6]DMSO, and D2O. The preparation of the OPA-based medium is simple and rapid, while only very weak background signals were observed from OPAs. Furthermore, we show that the purity of OPA has only a minor influence on the quality of the RDC data. These advantages allow RDC measurements of organic molecules with different polarities and solubilities with high efficiency and accuracy. 相似文献
24.
Qianqian Gao Dr. Yumeng Zhao Kangli Xu Dr. Chao Zhang Dr. Qian Ma Liqing Qi Dandan Chao Tingting Zheng Linlin Yang Dr. Yanyan Miao Prof. Da Han 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(52):23770-23774
A single-step method for isolation of specific cells based on multiple surface markers will have unique advantages because of its scalability, efficacy, and mildness. Herein, we developed multi-aptamer-mediated proximity ligation method on live cell membranes that leverages a multi-receptor co-recognition design for enhanced specificity, as well as a robust in situ signal amplification design for improved sensitivity of cell isolation. We demonstrated the promising efficacy of our method on differentiating tumor cell subtypes in both cell mixtures and clinical samples. Owing to its simple and fast operation with excellent cell isolation sensitivity and accuracy, this approach will have broad applications in biological science, biomedical engineering, and personalized medicine. 相似文献
25.
高速开关电容阵列(SCA)具有高速采样、低功耗的特点,基于SCA的高速波形数字化是目前高精度时间测量的一个重要研究方向。为此,我们开展SCA芯片的研究,目前已设计完成原型ASIC设计,并正在进行后续版本的改进设计。为便于未来多版本ASIC的测试和评估,需设计具有一定通用性的数字读出模块,本论文工作主要介绍此模块的设计工作以及相应的数据读出软件。数字读出模块基于FPGA实现对待测ASIC的控制、配置及数据读出,采用DDR3片外存储芯片,使用USB3.0等接口进行数据传输;上位机软件基于Python3.7设计,实现了数据采集与波形绘制等功能。目前已使用设计完成的数字读出模块对第2版SCA ASIC进行了初步的测试,测试结果表明,此读出模块工作正常,且SCA芯片输出结果符合预期。 相似文献
26.
假设纤维方向角沿层合板的长度方向线性变化,研究了变角度纤维复合材料层合斜板的颤振.通过坐标变换将斜板变换为正方形板,采用层合板表面连续变化的速度环量来模拟空气对其的作用,速度环量分布利用Cauchy积分公式计算.建立了系统的Lagrange方程并采用Ritz法得到了层合板的自振频率和颤振/不稳定性分离临界速度.通过数值算例验证了本文模型和方法的正确性和收敛性,分析了各个铺层内纤维方向角的变化对自振频率和颤振/不稳定性分离临界速度的影响.研究结果表明,通过纤维的变角度铺设,可有效地提高层合板的基频和颤振/不稳定性分离临界速度.经合理设计的变角度复合材料层合板具有抑制颤振的作用. 相似文献
27.
28.
Nonlinear Dynamics - Conservative chaotic flows, a category of incompressible chaos, are usually generated from dynamical systems without dissipation. The existing results on conservative chaos are... 相似文献
29.
De-en Han Yanmei Shi Ping Tian Hengchao Wei Mingsan Miao Xiu-min Li 《Biomedical chromatography : BMC》2020,34(7):e4838
A rapid and sensitive method was developed and validated for the quantitative determination of xanthopurpurin (XPP) in rat plasma using ultra-performance liquid chromatography-electrospray ionization-Orbitrap mass spectrometry. XPP inhibits IgE production and prevents peanut-induced anaphylaxis. The XPP and emodin (internal standard) were determined in negative ion mode with m/z 239.0350 → 211.0400 and 269.0455 → 241.0507, respectively. The separation process was achieved using an ACQUITY UPLC HSS T3 column with acetonitrile and 0.1% formic acid in water (85:15). The linear range was 0.5–100 ng/mL, and the correlation coefficient (r2) was > 0.993. The inter-day and intra-day precision was within an acceptable range of 15%. The extraction recovery and matrix effect were 78.9–87.2% and 94.3–98.5%, respectively. Under different conditions, the XPP was stable in the range of 5.6–10.6%. This method was successfully applied to study the pharmacokinetics of XPP with an oral dose of 10.0 mg/kg and intravenous dose of 2.0 mg/kg in rats. The absolute oral bioavailability of XPP was 4.6%. 相似文献
30.
Weijie Jiao Zhen Lei Xu Zhao Kun Wang Ailing Ma Lei Du Ruiying Hou Jing Han Meng Chen 《Biomedical chromatography : BMC》2020,34(9):e4869
To investigate the effect of ligustrazine on the pharmacokinetic profile of tanshinol after intravenous administration in rats, a sensitive liquid chromatography tandem mass spectrometry method was developed and validated for quantitative determination of tanshinol and ligustrazine in rat plasma. After prepared by protein precipitation, the analytes were separated on a Waters Acquity HSS T3 column (100 × 2.1 mm, 1.8μm) and eluted by 0.1% formic acid in water and acetonitrile at a flow rate of 0.4 ml/min. The precursor–product ion transitions were m/z 197.0 → 135.0 for tanshinol, m/z 417.1 → 255.1 for liquiritin (internal standard) in negative ion mode and m/z 137.1 → 55.0 for ligustrazine in positive ion mode. To avoid the interference of tanshinol metabolite transformation, the stability of analytes in samples collected after administration was assessed. The validated method was successfully applied to a pharmacokinetic study after intravenous administration of single tanshinol and Danshen Chuanxiongqin Injection. After Danshen Chuanxiongqin injection administration, the values of elimination half-time, area under the concentration–time curve and Co were 0.36 ± 0.13 h, 1.29 ± 0.37 μg/ml h and 10.51 ± 2.58 μg/ml for male rats, respectively. In the single tanshinol group, the corresponding values were 0.56 ± 0.24 h, 1.85 ± 0.44 μg/ml h and 14.11 ± 2.26 μg/ml for male rats—30–40% higher than those for the Danshen Chuanxiongqin Injection group. There was a significant different between male and female rats. This study provided information on the influence of ligustrazine on the pharmacokinetic characteristics of tanshinol after intravenous administration of Danshen Chuanxiongqin Injection in rats, which will be helpful for its clinical application. 相似文献