全文获取类型
收费全文 | 47888篇 |
免费 | 6693篇 |
国内免费 | 7493篇 |
专业分类
化学 | 27294篇 |
晶体学 | 550篇 |
力学 | 4782篇 |
综合类 | 134篇 |
数学 | 11162篇 |
物理学 | 18152篇 |
出版年
2024年 | 36篇 |
2023年 | 1165篇 |
2022年 | 1289篇 |
2021年 | 1542篇 |
2020年 | 1873篇 |
2019年 | 1363篇 |
2018年 | 1594篇 |
2017年 | 1846篇 |
2016年 | 1889篇 |
2015年 | 2143篇 |
2014年 | 2915篇 |
2013年 | 3789篇 |
2012年 | 4107篇 |
2011年 | 4405篇 |
2010年 | 3523篇 |
2009年 | 3623篇 |
2008年 | 3418篇 |
2007年 | 3573篇 |
2006年 | 3307篇 |
2005年 | 2149篇 |
2004年 | 1582篇 |
2003年 | 1369篇 |
2002年 | 1161篇 |
2001年 | 1173篇 |
2000年 | 953篇 |
1999年 | 957篇 |
1998年 | 666篇 |
1997年 | 525篇 |
1996年 | 354篇 |
1995年 | 326篇 |
1994年 | 333篇 |
1993年 | 312篇 |
1992年 | 353篇 |
1991年 | 342篇 |
1990年 | 339篇 |
1989年 | 273篇 |
1988年 | 229篇 |
1987年 | 227篇 |
1986年 | 202篇 |
1985年 | 208篇 |
1984年 | 146篇 |
1983年 | 114篇 |
1982年 | 165篇 |
1981年 | 91篇 |
1980年 | 56篇 |
1979年 | 32篇 |
1971年 | 8篇 |
1965年 | 6篇 |
1957年 | 6篇 |
1936年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
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
122.
123.
阐明了引入溶剂渗透因子的必要性,较详细地介绍了两种渗透因子及它们间的关系。 相似文献
124.
Here, we report a new strategy for rapid synthesis of branched peptide by side-chain hydrazide ligation at Asn. The hydrazide was converted to thioester at Asn side chain by NaNO2 and thiol reagent, and sequential ligation with an N-terminus Cys-peptide efficiently afforded the branched peptide. A branched cyclic peptide was successfully synthesized by side-chain ligation with a two-Cys-peptide and formation of a disulfide bond. This approach provides a new way for expeditious synthesis of branched peptides and facilitates the design of neopeptides as functional bio-mimics. 相似文献
125.
126.
In this paper, a bivariate generating function CF(x, y) =f(x)-yf(xy)1-yis investigated, where f(x)= n 0fnxnis a generating function satisfying the functional equation f(x) = 1 + r j=1 m i=j-1aij xif(x)j.In particular, we study lattice paths in which their end points are on the line y = 1. Rooted lattice paths are defined. It is proved that the function CF(x, y) is a generating function defined on some rooted lattice paths with end point on y = 1. So, by a simple and unified method, from the view of lattice paths, we obtain two combinatorial interpretations of this bivariate function and derive two uniform partitions on these rooted lattice paths. 相似文献
127.
128.
Azobenzene‐Functionalized Cage Silsesquioxanes as Inorganic–Organic Hybrid,Photoresponsive, Nanoscale,Building Blocks 下载免费PDF全文
Prof. Hongzhi Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(12):4731-4738
Mono‐ and octa‐azobenzene‐functionalized cage silsesquioxanes were easily synthesized by the reaction of 4‐bromoazobenzene with monovinyl‐substituted octasilsesquioxane and cubic octavinylsilsesquioxane through the Heck coupling reaction. Excited‐state energies obtained from time‐dependent density functional theory (TDDFT) and the CAM‐B3LYP functional correlate very well with experimental trans–cis photoisomerization results from UV/Vis spectroscopy. These azobenzene‐functionalized cages exhibit good thermal stability and are fluorescent with maximum emission at approximately 400 nm, making them potential materials for blue‐light emission. 相似文献
129.
130.
Mengjie Hu Haiquan Chen Mengxia Wang Gang Liu Chunhai Chen Guangtao Qian Youhai Yu 《Journal of polymer science. Part A, Polymer chemistry》2021,59(4):329-339
Polyimides (PI's) with low-dielectric constant and excellent organic solubility have broad application prospects in the electronic field. Herein, this study designed a series of novel, low dielectric, organic soluble PI films by creatively introducing fluorene and pyridine ring into diamine monomers. Because of the noncoplanar structure of fluorenyl and the polarization of pyridine ring, PI films achieved a low-dielectric constant (2.22–3.09 at 10 MHz) and excellent organic solubility. Even in some organic solvents with low-boiling points, these PI films still exhibited outstanding solubility. In addition, all the films possessed high-tensile strength (≈120 MPa) and excellent optical transparency (>70%, 450 nm). It was worth noting that the glass transition temperature of films was all above 280°C and 5% weight loss temperature (T5%) was at 486–553°C. In general, the novel high-performance low-dielectric PI films are expected to be used in the field of microelectronics. 相似文献