全文获取类型
收费全文 | 3073篇 |
免费 | 543篇 |
国内免费 | 346篇 |
专业分类
化学 | 2108篇 |
晶体学 | 36篇 |
力学 | 231篇 |
综合类 | 23篇 |
数学 | 395篇 |
物理学 | 1169篇 |
出版年
2024年 | 8篇 |
2023年 | 64篇 |
2022年 | 83篇 |
2021年 | 111篇 |
2020年 | 140篇 |
2019年 | 125篇 |
2018年 | 121篇 |
2017年 | 112篇 |
2016年 | 177篇 |
2015年 | 146篇 |
2014年 | 159篇 |
2013年 | 207篇 |
2012年 | 316篇 |
2011年 | 348篇 |
2010年 | 221篇 |
2009年 | 170篇 |
2008年 | 187篇 |
2007年 | 203篇 |
2006年 | 180篇 |
2005年 | 114篇 |
2004年 | 97篇 |
2003年 | 91篇 |
2002年 | 57篇 |
2001年 | 40篇 |
2000年 | 44篇 |
1999年 | 47篇 |
1998年 | 50篇 |
1997年 | 54篇 |
1996年 | 45篇 |
1995年 | 31篇 |
1994年 | 33篇 |
1993年 | 32篇 |
1992年 | 31篇 |
1991年 | 25篇 |
1990年 | 19篇 |
1989年 | 13篇 |
1988年 | 12篇 |
1987年 | 5篇 |
1986年 | 18篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1973年 | 1篇 |
1970年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有3962条查询结果,搜索用时 31 毫秒
1.
Dan Chen Kaixin Du Xiaochen Niu Hongwei Zhang Xue Zhang Yu Tang Jianchun Zhao 《Biomedical chromatography : BMC》2022,36(3):e5288
Amlexanox, an anti-inflammatory and anti-allergic agent, has been widely used clinically for the treatment of canker sores, asthma, and allergic rhinitis. Recently, amlexanox has received considerable attention in curing nonalcoholic fatty liver diseases and hepatitis virus infection. Herein, we first established a sensitive high-performance liquid chromatography-tandem mass spectrum (LC–MS/MS) method for the determination of amlexanox in rat plasma. Propranolol was used as the internal standard (IS). Using a simple protein precipitation method, the amlexanox and IS were separated with Capcell Pak C18 column (2.0 × 50 mm, 5 μm) and eluted with water and acetonitrile each containing 0.1% formic acid using gradient elution condition at a flow rate of 0.4 mL·min−1. Amlexanox and IS were detected by a triple quadrupole mass in multiple reactive monitoring (MRM) under the transitions of m/z 299.2 → 281.2 and m/z 259.9 → 116.1 with positive electrospray ionization, respectively. The calibration curves of amlexanox were established with the range of 50 to 2000 ng·mL−1 (r2 > 0.99). The validation method consisted of selectivity, accuracy, precision, carryover effect, matrix effect, recovery, dilution effect, and stability. The fully validated method was successfully applied to the pharmacokinetic study of amlexanox in Wistar rats. 相似文献
2.
Nonlinear Dynamics - This paper seeks to address the problem of finite-time stabilization for a class of uncertain Hamiltonian systems via sliding mode control approach. A novel sliding function in... 相似文献
3.
4.
Development of an LC‐MS/MS method for determining the pharmacokinetics of clonidine following oral administration of Zhenju antihypertensive compound 下载免费PDF全文
Jing Qin Limin Wang Lihong Wu Jun Chen Teng Shen Yongji Li Limei Han Jianxin Wang 《Biomedical chromatography : BMC》2015,29(7):1068-1075
Zhenju antihypertensive compound (ZJAHC) is a combined Chinese–Western medicine formula including clonidine (CLO), hydrochlorothiazide (HCT), rutin, Chrysanthemum indicum extract and pearl powder. Compared with CLO preparations, ZJAHC shows improved activities and decreased adverse effects. It is believed that the side effects of CLO are caused by its high peak plasma concentration. Hence, study of the influence of ZJAHC on the pharmacokinetic behaviors of clonidine seems essential. In present study, the plasma concentrations of CLO were determined with a liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method. The MS/MS transitions monitored for clonidine and internal standard were 230.2 → 213.1 and 152.2 → 110.2, respectively. The analyte was quantified in a single run within 3 min. The pharmacokinetic study showed that the area under the plasma concentration–time curve of CLO in ZJAHC (60 µg/kg CLO) was similar to that of CLO‐HCT‐high (120 µg/kg CLO) but the peak concentration was much lower than that in CLO‐HCT‐high. ZJAHC could enhance the bioavailability without greatly increasing peak concentration of clonidine. This comprehensive effect of enhancing the bioavailability and avoiding the high peak plasma concentration for CLO might mainly result from the co‐contribution of Western medicine and traditional Chinese medicine (TCM), while the effect of TCM was stronger than that of Western medicine. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
5.
Studies on metabolism of total glucosides of paeony from Paeoniae Radix Alba in rats by UPLC‐Q‐TOF‐MS/MS 下载免费PDF全文
Wenli Cao Xinguo Wang Haojie Li Xuliang Shi Wencheng Fan Shaohua Zhao Minyan Liu Liying Niu 《Biomedical chromatography : BMC》2015,29(11):1769-1779
Total glucosides of paeony are the active constituents of Paeoniae Radix Alba. In this study, a novel strategy was proposed to find more metabolites and the differences between paeoniflorin, albiflorin and total glucosides of paeony (TGP). This strategy was characterized as follows: firstly, the animals were divided into three groups (paeoniflorin, albiflorin and TGP) to identify the source of TGP metabolites from paeoniflorin or albiflorin; secondly, a generic information‐dependent acquisition scan for the low‐level metabolites was triggered by the multiple mass defect filter and dynamic background subtraction; thirdly, the metabolites were identified with a combination of data‐processing methods including mass defect filtering, neutral loss filtering and product ion filtering; finally, a comparative study was used in the metabolism of paeoniflorin, albiflorin and TGP. Based on the strategy, 18 metabolites of TGP, 10 metabolites of paeoniflorin and 13 metabolites of albiflorin were identified respectively. The results indicated that the hydrolysis, conjugation reaction and oxidization were the major metabolic pathways, and the metabolic sites were the glycosidic linkage, the ester bond and the benzene ring. This study is first to explore the metabolism of TGP, and these findings enhance our understanding of the metabolism and the interactions of paeoniflrin and albiflorin in TGP. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
6.
Nonlinear Dynamics - Nonlinear vibration isolation provides with an effective way for vibration reduction with broad band and high efficiency. This investigation focuses on the dynamic effects of a... 相似文献
7.
本文证明了Heisenberg群上Laplace算子的Dirichlet特征值的存在性,给出了特征值的估计 相似文献
8.
Zi‐Niu Wu 《国际流体数值方法杂志》2005,48(5):541-564
The widely used locally adaptive Cartesian grid methods involve a series of abruptly refined interfaces. In this paper we consider the influence of the refined interfaces on the steady state errors for second‐order three‐point difference approximations of flow equations. Since the various characteristic components of the Euler equations should behave similarly on such grids with regard to refinement‐induced errors, it is sufficient enough to conduct the analysis on a scalar model problem. The error we consider is a global error, different to local truncation error, and reflects the interaction between multiple interfaces. The steady state error will be compared to the errors on smooth refinement grids and on uniform grids. The conclusion seems to support the numerical findings of Yamaleev and Carpenter (J. Comput. Phys. 2002; 181: 280–316) that refinement does not necessarily reduce the numerical error. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
9.
Lihong Wang 《Annals of the Institute of Statistical Mathematics》2004,56(2):251-264
The purpose of this paper is to investigate the asymptotic properties of the least squares estimates (L
2-estimates) and the least absolute deviation estimates (L
1-estimates) of the parameters of a nonlinear regression model subject to a set of equality and inequality restrictions, which
has a long-range dependent stationary process as its stochastic errors. Then we will compare the asymptotic relative efficiencies
of the above estimators. 相似文献
10.