全文获取类型
收费全文 | 50819篇 |
免费 | 6820篇 |
国内免费 | 4610篇 |
专业分类
化学 | 11064篇 |
晶体学 | 963篇 |
力学 | 9782篇 |
综合类 | 585篇 |
数学 | 14832篇 |
物理学 | 13606篇 |
无线电 | 11417篇 |
出版年
2024年 | 147篇 |
2023年 | 576篇 |
2022年 | 951篇 |
2021年 | 1130篇 |
2020年 | 1442篇 |
2019年 | 1204篇 |
2018年 | 1202篇 |
2017年 | 1781篇 |
2016年 | 2080篇 |
2015年 | 1775篇 |
2014年 | 2835篇 |
2013年 | 3567篇 |
2012年 | 3403篇 |
2011年 | 3687篇 |
2010年 | 3073篇 |
2009年 | 3269篇 |
2008年 | 3298篇 |
2007年 | 3335篇 |
2006年 | 3010篇 |
2005年 | 2766篇 |
2004年 | 2370篇 |
2003年 | 2098篇 |
2002年 | 1856篇 |
2001年 | 1535篇 |
2000年 | 1395篇 |
1999年 | 1244篇 |
1998年 | 1130篇 |
1997年 | 957篇 |
1996年 | 810篇 |
1995年 | 705篇 |
1994年 | 629篇 |
1993年 | 506篇 |
1992年 | 520篇 |
1991年 | 395篇 |
1990年 | 307篇 |
1989年 | 252篇 |
1988年 | 193篇 |
1987年 | 129篇 |
1986年 | 86篇 |
1985年 | 115篇 |
1984年 | 111篇 |
1983年 | 54篇 |
1982年 | 71篇 |
1981年 | 53篇 |
1980年 | 28篇 |
1979年 | 43篇 |
1978年 | 31篇 |
1977年 | 37篇 |
1976年 | 13篇 |
1957年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
871.
Shang Chen Chenyan Ren Yuan Ji Dongke Liu Xinke Zhang Fengshan Wang 《Molecules (Basel, Switzerland)》2022,27(13)
Thymus immunosuppressive pentapeptide (TIPP) is a novel anti-inflammatory peptide with high efficacy and low toxicity. This study aims to establish a selective LC-MS/MS method for analyzing the analyte TIPP in biological samples, laying the foundation for further PK and PD studies of TIPP. Protein precipitation was conducted in acetonitrile supplemented with 2% formic acid and 25 mg/mL dithiothreitol as a stabilizer, which was followed by backwashing the organic phase using dichloromethane. The chromatographic separation of TIPP was achieved on a C18 column with a gradient elution method. During positive electrospray ionization, TIPP was analyzed via multiple-reaction monitoring. The linear relationships between the concentration of TIPP and peak area in murine plasma cell lysates, supernatants, and the final cell rinse PBS were established within the ranges of 20–5000 ng/mL, 1–200 ng/mL, 10–200 μg/mL, and 0.1–20 ng/mL, respectively (r2 > 0.99). Validated according to U.S. FDA guidelines, the proposed method was proved to be acceptable. Such a method had been successfully applied to investigate the pharmacokinetics of TIPP in mice via subcutaneous injection. The plasma half-life in mice was 5.987 ± 1.824 min, suggesting that TIPP is swiftly eliminated in vivo. The amount of TIPP uptake by RBL-2H3 cells was determined using this method, which was also visually verified by confocal. Furthermore, the effective intracellular concentration of TIPP was deduced by comparing the intracellular concentration of TIPP and degrees of inflammation, enlightening further investigation on the intracellular target and mechanism of TIPP. 相似文献
872.
应用Bayes统计方法进行武器射程的评定,可以有效减少试验的样本量,节省试验弹药,Bayes方法的关键是确定先验分布,均匀分布是比较容易确定的一种先验分布,该文给出了基于均匀先验分布武器射程评定的Bayes方法,对改进射程的评定方法,减少试验用弹量,具有重要作用. 相似文献
873.
874.
Magdalena
widro-Pito Alicja Chromiec Marcin Zawadzki Renata Wietecha-Posuszny 《Molecules (Basel, Switzerland)》2022,27(13)
The present investigation utilised the quick and easy SPME/LC-MS method to determine selected narcotic substances and their metabolites in whole blood. The study included qualitative analysis and validation of the method. Analytes were determined in the linearity range of 25–300 ng/mL. The precision during and between days (in general CV < 13.41%), and the LOD which results in between 0.36 and 11.08 ng/mL, and the LOQ between 1.20 and 36.90 ng/mL were investigated. The validation results obtained, as well as the results of subsequent in-laboratory tests, confirmed the applicability of the method in the analysis of blood samples. An attempt to apply the method to the analysis of bone marrow samples has yielded promising results; however, more detailed studies are needed in this area. 相似文献
875.
针对清梳棉流程中产出棉含杂高、质量差的问题,结合改进高斯混合模型(Gaussian mixed model,GMM)与帧差法,提出一种局部运动棉杂率控制优化方法。首先针对清棉机除杂原理及棉杂特性进行分析;其次通过提取视频关键帧并改进GMM与帧差法对图像序列“与”运算实现目标的精确提取,进而通过设计GMM分类器获得棉杂率并进行分析;最后与传统的检测算法作对比验证。实验表明,改进后的算法在有效性以及实用性方面优于传统算法。同时,通过引入闭环控制能满足工业高精度、实时性的需求。 相似文献
876.
877.
将文献[1]给出的由一维连续型随机变量的概率密度函数构造二维连续型随机变量的概率密度函数的方法,推广为由一维连续型随机变量的概率密度函数构造三维连续型随机变量的概率密度函数的情况,并作出了证明和举例说明.说明利用本文的方法构造多维概率密度函数,其方法简单易行. 相似文献
878.
879.
880.