全文获取类型
收费全文 | 233092篇 |
免费 | 2507篇 |
国内免费 | 659篇 |
专业分类
化学 | 125547篇 |
晶体学 | 3334篇 |
力学 | 11024篇 |
综合类 | 10篇 |
数学 | 27214篇 |
物理学 | 69129篇 |
出版年
2021年 | 2365篇 |
2020年 | 2501篇 |
2019年 | 3034篇 |
2018年 | 4016篇 |
2017年 | 4026篇 |
2016年 | 5612篇 |
2015年 | 3043篇 |
2014年 | 5082篇 |
2013年 | 10255篇 |
2012年 | 8624篇 |
2011年 | 10265篇 |
2010年 | 7547篇 |
2009年 | 7598篇 |
2008年 | 9535篇 |
2007年 | 9512篇 |
2006年 | 8569篇 |
2005年 | 7662篇 |
2004年 | 7123篇 |
2003年 | 6449篇 |
2002年 | 6364篇 |
2001年 | 5978篇 |
2000年 | 4510篇 |
1999年 | 3470篇 |
1998年 | 3017篇 |
1997年 | 3094篇 |
1996年 | 2996篇 |
1995年 | 2541篇 |
1994年 | 2604篇 |
1993年 | 2479篇 |
1992年 | 2779篇 |
1991年 | 2868篇 |
1990年 | 2750篇 |
1989年 | 2819篇 |
1988年 | 2754篇 |
1987年 | 2746篇 |
1986年 | 2588篇 |
1985年 | 3336篇 |
1984年 | 3391篇 |
1983年 | 2803篇 |
1982年 | 2832篇 |
1981年 | 2807篇 |
1980年 | 2589篇 |
1979年 | 2954篇 |
1978年 | 2888篇 |
1977年 | 3068篇 |
1976年 | 3053篇 |
1975年 | 2851篇 |
1974年 | 2787篇 |
1973年 | 2892篇 |
1972年 | 2155篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
61.
Elasasy M. E. A. Elnaggar D. H. Hafez N. A. Abdel Azab M. E. Amr A. E. Omran M. M. Mohamed A. M. 《Russian Journal of General Chemistry》2021,91(5):915-925
Russian Journal of General Chemistry - Some new fluoro-heterocyclic compounds containing thiazole and pyridine moities have been synthesized and studied for their antiproliferative activity.... 相似文献
62.
Henry Dring David Kreutzer Christoph Ritter Andreas Hilgeroth 《Molecules (Basel, Switzerland)》2021,26(1)
Despite the development of targeted therapies in cancer, the problem of multidrug resistance (MDR) is still unsolved. Most patients with metastatic cancer die from MDR. Transmembrane efflux pumps as the main cause of MDR have been addressed by developed inhibitors, but early inhibitors of the most prominent and longest known efflux pump P-glycoprotein (P-gp) were disappointing. Those inhibitors have been used without knowledge about the expression of P-gp by the treated tumor. Therefore the use of inhibitors of transmembrane efflux pumps in clinical settings is reconsidered as a promising strategy in the case of the respective efflux pump expression. We discovered novel symmetric inhibitors of the symmetric efflux pump MRP4 encoded by the ABCC4 gene. MRP4 is involved in many kinds of cancer with resistance to anticancer drugs. All compounds showed better activities than the best known MRP4 inhibitor MK571 in an MRP4-overexpressing cell line assay, and the activities could be related to the various substitution patterns of aromatic residues within the symmetric molecular framework. One of the best compounds was demonstrated to overcome the MRP4-mediated resistance in the cell line model to restore the anticancer drug sensitivity as a proof of concept. 相似文献
63.
Yuwei Wang Jia-Jun Yan Shengnan Hu Prof. David James Young Prof. Hong-Xi Li Prof. Zhi-Gang Ren 《化学:亚洲杂志》2021,16(18):2681-2686
A photoluminescent bimetallic cluster [Ag10Cu6(bdppthi)2(C≡CPh)12(MeOH)2(H2O)](ClO4)4 ( 1 , bdppthi=N,N’-bis(diphenylphosphanylmethyl)-tetrahydroimidazole} was synthesized from the PNNP type ligand bdppthi generated in-situ. Upon excitation at 365 nm, 1 exhibited strong phosphorescent emission at 630 nm, which was selectively quenched by NH3 in air or water. The sensing of NH3 was rapid and recoverable, with detection limits of 53 ppm (v/v) in N2 and 21 μmol/L (0.36 ppm, w/w) for NH3 ⋅ H2O in water. Cluster 1 could potentially serve as a bifunctional chemical sensor for the efficient detection of ammonia in waste-gas and waste-water. 相似文献
64.
65.
66.
Journal of Applied and Industrial Mathematics - We consider the optimization of the short wave phased antenna arrays as a quadratic programming problem. The penalty function method and the gradient... 相似文献
67.
Ahmed Waqar Chowdhury Z. Z. Kazi S. N. Johan MR. Akram Naveed Oon C. S. Abdelrazek Ali H. 《Journal of Thermal Analysis and Calorimetry》2021,144(4):1517-1534
Journal of Thermal Analysis and Calorimetry - In recent decades, the growth of heat transfer using nanomaterials in the conventional base fluid has caught the attention of researchers... 相似文献
68.
69.
Indermeet Kohli Taylor L. Braunberger Amanda F. Nahhas Fatima N. Mirza Mohsen Mokhtari Alexis B. Lyons Nikiforos Kollias Eduardo Ruvolo Henry W. Lim Iltefat H. Hamzavi 《Photochemistry and photobiology》2020,96(1):208-214
Human skin is exposed to visible light (VL; 400–700 nm) and long-wavelength ultraviolet A1 (UVA1) radiation (370–400 nm) after the application of organic broad-spectrum sunscreens. The biologic effects of these wavelengths have been demonstrated; however, a dose–response has not been investigated. Ten subjects with Fitzpatrick skin phototype IV-VI were enrolled. Subjects were irradiated with 2 light sources (80–480 J cm−2): one comprising VL with less than 0.5% UVA1 (VL+UVA1) and the other pure VL. Skin responses were evaluated for 2 weeks using clinical and spectroscopic assessments. 4-mm punch biopsies were obtained from nonirradiated skin and sites irradiated with 480 J cm−2 of VL+UVA1 and pure VL 24 h after irradiation. Clinical and spectroscopic assessments demonstrated a robust response at VL+UVA1 sites compared with pure VL. Histology findings demonstrated a statistically significant increase in the marker of inflammation (P < 0.05) and proliferation (P < 0.05) at the irradiated sites compared with nonirradiated control. Threshold doses of VL+UVA1 resulting in biologic responses were calculated. Results indicate that approximately 2 h of sun exposure, which equates to VL+UVA1 dose (~400 J cm−2), is capable of inducing inflammation, immediate erythema and delayed tanning. These findings reinforce the need of photoprotection beyond the UV range. 相似文献