全文获取类型
收费全文 | 217394篇 |
免费 | 4174篇 |
国内免费 | 1908篇 |
专业分类
化学 | 121235篇 |
晶体学 | 3798篇 |
力学 | 8996篇 |
综合类 | 106篇 |
数学 | 21083篇 |
物理学 | 68258篇 |
出版年
2021年 | 1833篇 |
2020年 | 2191篇 |
2019年 | 2346篇 |
2018年 | 2622篇 |
2017年 | 2718篇 |
2016年 | 4096篇 |
2015年 | 2744篇 |
2014年 | 4262篇 |
2013年 | 10052篇 |
2012年 | 7675篇 |
2011年 | 9280篇 |
2010年 | 6483篇 |
2009年 | 6505篇 |
2008年 | 8153篇 |
2007年 | 7994篇 |
2006年 | 7575篇 |
2005年 | 6883篇 |
2004年 | 6190篇 |
2003年 | 5592篇 |
2002年 | 5332篇 |
2001年 | 6487篇 |
2000年 | 4923篇 |
1999年 | 3856篇 |
1998年 | 3080篇 |
1997年 | 2987篇 |
1996年 | 2881篇 |
1995年 | 2678篇 |
1994年 | 2595篇 |
1993年 | 2347篇 |
1992年 | 2997篇 |
1991年 | 2868篇 |
1990年 | 2825篇 |
1989年 | 2786篇 |
1988年 | 2803篇 |
1987年 | 2815篇 |
1986年 | 2683篇 |
1985年 | 3393篇 |
1984年 | 3378篇 |
1983年 | 2646篇 |
1982年 | 2759篇 |
1981年 | 2809篇 |
1980年 | 2565篇 |
1979年 | 2904篇 |
1978年 | 2889篇 |
1977年 | 3005篇 |
1976年 | 2836篇 |
1975年 | 2576篇 |
1974年 | 2526篇 |
1973年 | 2482篇 |
1972年 | 1712篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
101.
102.
103.
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
![点击此处可从《Biomedical chromatography : BMC》网站下载免费的PDF全文](/ch/ext_images/free.gif)
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
104.
105.
106.
Pan Huang Dawen Xu Robert M. Reich Felix Kaiser Boping Liu Fritz E. Kühn 《Tetrahedron letters》2019,60(24):1574-1577
A first example of an Et2Zn mediated silylation of 1-aklynes is reported. A series of functional groups are tolerated in this reaction. Mechanistic studies support Zn alkynilides as intermediates in the reaction. This reaction protocol provides a practical method for the preparation of alkynylsilanes and expands the application of organometallic zinc in organic synthesis. 相似文献
107.
Journal of Global Optimization - In this paper, we propose a novel algorithm that is based on quadratic-piecewise-linear approximations of DC functions to solve nonnegative sparsity-constrained... 相似文献
108.
The possibility of realizing SASE Free Election Laser in x-ray waveband with EM-wave wiggler is studied in this paper. SASE effect including saturation length, saturation power and nonlinear process is explored through a 3-D simulation code. A utilization of seed light from laser plasma x-ray is also analyzed, which demonstrates the feature of shortening the interaction length for saturation. The results show that sizeable output power of x-ray laser would be generated with a middle energy electron beam. 相似文献
109.
W. L. Liang B. K. A. Ngoi L. E. N. Lim K. Venkatakrishnan C. W. Hee 《Optics & Laser Technology》2003,35(4):285-290
In this paper, integration of interference phenomenon into femtosecond laser micromachining was reported as the femtosecond laser pulses were reshaped spatially to perform ablation. The generation of circular interference pattern was demonstrated by overlapping infrared femtosecond laser pulses. The interference pattern was subsequently focused on a copper substrate to ablate microstructures of concentric circular rings. The present technique is expected to open up new applications in the areas of rapid fabrication of micro-Fresnel lenses, hybrid microlenses and lens arrays. 相似文献
110.
A combination of 1,3-dihalo-5,5-dimethylhydantoin (X = Br, Cl) and sodium nitrite in the presence of wet SiO2 was used as an effective nitrosating agent for the nitrosation of N,N-dialkyl amines to their corresponding nitroso derivatives under mild and heterogeneous conditions in good to excellent yields. 相似文献