全文获取类型
收费全文 | 17825篇 |
免费 | 2128篇 |
国内免费 | 2057篇 |
专业分类
化学 | 4871篇 |
晶体学 | 59篇 |
力学 | 905篇 |
综合类 | 407篇 |
数学 | 13026篇 |
物理学 | 2742篇 |
出版年
2024年 | 14篇 |
2023年 | 189篇 |
2022年 | 212篇 |
2021年 | 316篇 |
2020年 | 473篇 |
2019年 | 507篇 |
2018年 | 467篇 |
2017年 | 484篇 |
2016年 | 678篇 |
2015年 | 569篇 |
2014年 | 873篇 |
2013年 | 1333篇 |
2012年 | 865篇 |
2011年 | 1150篇 |
2010年 | 1016篇 |
2009年 | 1298篇 |
2008年 | 1372篇 |
2007年 | 1343篇 |
2006年 | 1181篇 |
2005年 | 1018篇 |
2004年 | 841篇 |
2003年 | 918篇 |
2002年 | 741篇 |
2001年 | 534篇 |
2000年 | 604篇 |
1999年 | 528篇 |
1998年 | 480篇 |
1997年 | 469篇 |
1996年 | 314篇 |
1995年 | 187篇 |
1994年 | 187篇 |
1993年 | 132篇 |
1992年 | 99篇 |
1991年 | 91篇 |
1990年 | 65篇 |
1989年 | 40篇 |
1988年 | 55篇 |
1987年 | 29篇 |
1986年 | 27篇 |
1985年 | 44篇 |
1984年 | 50篇 |
1983年 | 21篇 |
1982年 | 33篇 |
1981年 | 28篇 |
1980年 | 33篇 |
1979年 | 22篇 |
1978年 | 18篇 |
1977年 | 17篇 |
1976年 | 11篇 |
1936年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
2.
3.
Geetika Wadhwa Kowthavarapu Venkata Krishna Rajeev Taliyan Neeraj Tandon Satyapal Singh Yadav Dipankar Banerjee Avinash Narwaria Chandrakant Katiyar Sunil Kumar Dubey 《Biomedical chromatography : BMC》2022,36(2):e5275
Trigonelline (TR), 4-hydroxyisoleucine (4-HI), and diosgenin (DG) are the main bioactives of the purified standardized extract of the popular plant Trigonella foenum-graecum L. (TFG), and it has been proven effective for the treatment of various diseases. However, to the best of our knowledge, no study has investigated the pharmacokinetic parameters of purified standardized T. foenum-graecum extract in normal and diabetic Wistar rats. The present study has developed and validated a rapid, reliable, and sensitive simultaneous ultra-performance liquid chromatography MS method to estimate these bioactives. The chromatographic separation was achieved using methanol, acetonitrile, and 0.1% formic acid with the ideal gradient flow system on a BEH Shield RP 18 column. A positive electrospray ionization mode was selected to estimate m/z values of TR (138.14 > 94.63), 4-HI (148.19 > 74.08), and DG (415.54 > 271.33). The method was robust and reproducible over the linearity range of 60–5000, 6–5000, and 15–5000 ng/mL for TR, 4-HI, and DG, respectively. Using this novel validated method, we investigated the pharmacokinetic parameters of bioactives using Phoenix WinNonlin version 8.0 (Certera) in normal and diabetic rats. The assay was successfully applied for the estimation of pharmacokinetic parameters using noncompartmental analysis. This investigation shows that the absorption rate increased, whereas distribution and elimination processes slowed down in diabetic rats compared with normal rats. 相似文献
4.
Tingrui Li Yilitabaier Julaiti Xiaopeng Wu Jie Han Dr. Jin Xie 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(71):e202202851
The gold-catalyzed ring-opening rearrangement of cyclopropenes affords an efficient route to either polysubstituted naphthols or aryl-substituted furans. Owing to the unique dichotomy of gold−carbenes, this protocol provides a switchable reaction selectivity between naphthols and furans enabled by the use of TFP−Au(MeCN)SbF6 (tri(2-furyl) phosphine) or PNP(AuNTf2)2 (bis(diphenylphosphino)(isopropyl) amine) as catalysts respectively. It is proposed that the gold−carbene intermediate might be involved in the cyclopropene→naphthol rearrangement while the gold-carbocation is more likely to be involved in the cyclopropene→furan rearrangement. 相似文献
5.
Feng Cheng Shuqi Wu Wenwei Zheng Shengqun Su Takumi Nakanishi Wenhuang Xu Pritam Sadhukhan Hibiki Sejima Shimon Ikenaga Kaoru Yamamoto Kaige Gao Shinji Kanegawa Prof. Osamu Sato 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(59):e202202161
The crystallization of a complex having electron transfer properties in a polar space group can induce the polarization switching of a crystal in a specific direction, which is attractive for the development of sensors, memory devices, and capacitors. Unfortunately, the probability of crystallization in a polar space group is usually low. Noticing that enantiopure compounds crystallize in Sohncke space groups, this paper reports a strategy for the molecular design of non-ferroelectric polarization switching crystals based on the use of intramolecular electron transfer and chirality. In addition, this paper describes the synthesis of a mononuclear valence tautomeric (VT) cobalt complex bearing an enantiopure ligand. The introduction of enantiomer enables the crystallization of the complex in the polar space group (P21). The polarization of the crystals along the b-axis direction is not canceled out and the VT transition is accompanied by a change in the macroscopic polarization of the polar crystal. Polarization switching via electron transfer is realized at around room temperature. 相似文献
6.
7.
8.
9.
探讨了经济增长及金融发展与城乡收入差距之间互动影响,刻画了三者间的逻辑关系,并基于广西1990-2017年的统计数据,运用状态空间模型及卡尔曼滤波算法对三者间动态关系进行了实证分析.结果显示:经济增长对城乡收入差距呈现倒U型曲线形态,而金融发展则显示出具有不断缩小城乡收入差距的趋势. 相似文献
10.