全文获取类型
收费全文 | 3302篇 |
免费 | 494篇 |
国内免费 | 240篇 |
专业分类
化学 | 3411篇 |
晶体学 | 33篇 |
力学 | 22篇 |
综合类 | 17篇 |
数学 | 218篇 |
物理学 | 335篇 |
出版年
2024年 | 5篇 |
2023年 | 33篇 |
2022年 | 206篇 |
2021年 | 220篇 |
2020年 | 207篇 |
2019年 | 149篇 |
2018年 | 91篇 |
2017年 | 109篇 |
2016年 | 176篇 |
2015年 | 175篇 |
2014年 | 222篇 |
2013年 | 296篇 |
2012年 | 186篇 |
2011年 | 181篇 |
2010年 | 162篇 |
2009年 | 176篇 |
2008年 | 157篇 |
2007年 | 154篇 |
2006年 | 160篇 |
2005年 | 158篇 |
2004年 | 138篇 |
2003年 | 125篇 |
2002年 | 88篇 |
2001年 | 46篇 |
2000年 | 57篇 |
1999年 | 51篇 |
1998年 | 51篇 |
1997年 | 31篇 |
1996年 | 46篇 |
1995年 | 30篇 |
1994年 | 46篇 |
1993年 | 22篇 |
1992年 | 17篇 |
1991年 | 11篇 |
1990年 | 4篇 |
1989年 | 10篇 |
1988年 | 9篇 |
1987年 | 12篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1978年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有4036条查询结果,搜索用时 15 毫秒
101.
Hereditary Transthyretin-associated amyloidosis (ATTR) is an autosomal dominant protein-folding disorder with adult-onset caused by mutation of transthyretin (TTR). TTR is characterized by extracellular deposition of amyloid, leading to loss of autonomy and finally, death. More than 100 distinct mutations in TTR gene have been reported from variable age of onset, clinical expression and penetrance data. Besides, the cure for the disease remains still obscure. Further, the prioritizing of mutations concerning the characteristic features governing the stability and pathogenicity of TTR mutant proteins remains unanswered, to date and thus, a complex state of study for researchers. Herein, we provide a full report encompassing the effects of every reported mutant model of TTR protein about the stability, functionality and pathogenicity using various computational tools. In addition, the results obtained from our study were used to create TTRMDB (Transthyretin mutant database), which could be easy access to researchers at http://vit.ac.in/ttrmdb. 相似文献
102.
《中国化学快报》2020,31(5):1281-1287
Extensive structure-activity relationships (SARs) study of JND3229 was conducted to yield a series of new reversible 2-oxo-3,4-dihydropyrimido[4,5-d]pyrimidine privileged scaffold as EGFRC797S inhibitors. One of the most potent compound 6i potently suppressed EGFRL858R/T790M/C797S kinase with an IC50 value of 3.1 nmol/L, and inhibited the proliferation of BaF3 cells harboring EGFRL858R/T790M/C797S and EGFR19D/T790M/C797S mutants with IC50 values of 290 nmol/L and 316 nmol/L, respectively. Further, 6i dose-dependently induced suppression of the phosphorylation of EGFRL858R/T790M/C797S and EGFR19D/T790M/C797S in BaF3 cells. Compound 6i may serve as a promising lead compound for further drug discovery overcoming the acquired resistance of non-small cell lung cancer (NSCLC) patients. 相似文献
103.
The effect of the addition of n-butanol (BuOH) and n-hexanol (HexOH) on the micellization of sodium dodecylsulfate (SDS) has been investigated using fluorescence quenching methods.
The binding constants were calculated using an expression which relates the total concentration of alcohols and the micelle
concentration. The values of K were 4.67 and 17.6 M-1 for BuOH/SDS and HexOH/SDS, similar to values obtained by other methods. The cmc of SDS decreases on addition of alcohols
and goes through a minimum for the BuOH/SDS system. Micellar aggregation numbers (N) were determined from linear plots of Ln (I
0/I) against [Quencher] at low alcohol concentrations. For 15 mM SDS, in the presence of BuOH the N values decrease on addition of alcohol up to 0.2 M. For HexOH, N can be assumed to be constant up to 4.8 mM, after which N decreases. The polarity of the micellar core containing alcohol was evaluated from the I
1/I
3 ratio of monomeric pyrene. The effect of addition of the alcohol causes a decrease in the I
1/I
3, which corresponds to a decrease in the polarity of the pyrene solubilization site.
Received: 28 October 1996 Accepted: 10 January 1997 相似文献
104.
105.
Francesca CardonaEnrico Faggi Francesca LiguoriMartina Cacciarini Andrea Goti 《Tetrahedron letters》2003,44(11):2315-2318
Practical syntheses of nitrone 8 by two different approaches from sugars are reported. Its use as a versatile intermediate in highly selective 1,3-dipolar cycloaddition reactions constitutes the key step for novel total syntheses of hyacinthacine A2 (3) and 7-deoxycasuarine (20) by simple transformations of a common isoxazolidine adduct. 相似文献
106.
Li Gao 《Tetrahedron》2005,61(15):3805-3811
Trihydroxy-2-thiaquinolizidines, a new class of bicyclic dideoxy-iminohexitol glycosidase inhibitor derivatives with nominally the d-gluco, l-ido, d-manno and l-gulo configurations were synthesized. X-ray analyses indicated that the preferred conformation for d-gluco and d-manno derivatives was a flat trans-fused system. Unlike deoxynojirimycin, the compound with d-gluco configuration was selective for α-glucosidases (yeast and rice) and showed no inhibitory activity towards β-glucosidase (almond), α-galactosidase (green coffee beans), α-galactosidase (E. coli) and α-mannosidase (jack bean), while the l-ido derivative was specific for β-glucosidase (almond). 相似文献
107.
在pH4.3的B-R缓冲体系中,用微相吸附-光谱修正技术[1]研究了茜素红(ARS)与牛血清白蛋白(BSA)、人血清白蛋白(HSA)的结合反应。其吸附结合常数分别为:KBSA-ARS=3.950×104,KHSA-ARS=4.377×104。染料与蛋白的最大结合数分别为NARS∶NBSA=9∶1,NARS∶NHSA=7∶1。经光谱修正技术计算结合产物的实际摩尔吸光系数分别为εBSA-ARS(537nm)=2.517×104L.mol-1.cm-1,εHSA-ARS(519nm)=2.051×104L.mol-1.cm-1,检出限BSA为19mg/L,HSA为23mg/L。经探讨该结合反应机理符合Langmuir吸附聚集反应方程。 相似文献
108.
磺化丁基橡胶离聚体在混合溶剂中的聚集行为 总被引:1,自引:0,他引:1
用顺磁共振(ESR)谱和粘度法考察了磺化丁基橡胶离聚体在二甲苯/正己醇混合溶剂中的聚集行为.ESR谱表明离聚体的离子基团发生聚集,其聚集程度受极性共溶剂(正己醇)的影响.粘度考察表明,在不同的浓度时离子基团有不同的聚集形式,低浓度时以分子内聚集为主,高浓度时以分子间聚集为主.离聚体的聚集度(DA)与浓度(c)的关系可用经验式DA=Aexp(kc2)表示,其中A、k为常数.k值反映聚集度受浓度影响的程度,醇含量增大时k值减小,这是因为醇对离子的溶剂化作用导致离子聚集的倾向减小. 相似文献
109.
Bernadette HugonBruno Pfeiffer Pierre RenardMichelle Prudhomme 《Tetrahedron letters》2003,44(20):3935-3937
A synthesis in a few steps of a new family of granulatimide analogues was performed. In the new compounds, the aromatic framework of granulatimide is modified by replacement of the imidazole unit by a maleimide moiety. The synthesis of a water-soluble analogue is also presented. 相似文献
110.
A series of 4‐[2‐(alicyclic‐[1,2,4]oxadiazol‐3‐yl)phenoxy]‐butyric acids were synthesized from N‐hydroxy‐2‐isopropoxy benzamidine in 4 steps with good yields. These [1,2,4]oxadiazoles are novel platelet aggregation inhibitors preventing human platelet aggregation induced by thromboxane derivative U44,619 and adenosine diphosphate. A structure‐activity‐relationship study revealed that the potency for these 5‐oxadiazoles increases with the increase in the ring size of the alicylic rings. Derivative 8f may be useful as a template for the design of more potent anti‐platelet agents. 相似文献