全文获取类型
收费全文 | 3555篇 |
免费 | 282篇 |
国内免费 | 10篇 |
专业分类
耳鼻咽喉 | 34篇 |
儿科学 | 236篇 |
妇产科学 | 66篇 |
基础医学 | 406篇 |
口腔科学 | 49篇 |
临床医学 | 257篇 |
内科学 | 798篇 |
皮肤病学 | 38篇 |
神经病学 | 278篇 |
特种医学 | 143篇 |
外科学 | 515篇 |
综合类 | 39篇 |
一般理论 | 2篇 |
预防医学 | 196篇 |
眼科学 | 121篇 |
药学 | 312篇 |
中国医学 | 8篇 |
肿瘤学 | 349篇 |
出版年
2023年 | 28篇 |
2022年 | 52篇 |
2021年 | 154篇 |
2020年 | 97篇 |
2019年 | 145篇 |
2018年 | 154篇 |
2017年 | 98篇 |
2016年 | 103篇 |
2015年 | 123篇 |
2014年 | 176篇 |
2013年 | 226篇 |
2012年 | 312篇 |
2011年 | 289篇 |
2010年 | 169篇 |
2009年 | 124篇 |
2008年 | 163篇 |
2007年 | 186篇 |
2006年 | 191篇 |
2005年 | 123篇 |
2004年 | 113篇 |
2003年 | 93篇 |
2002年 | 95篇 |
2001年 | 64篇 |
2000年 | 72篇 |
1999年 | 37篇 |
1998年 | 34篇 |
1997年 | 13篇 |
1996年 | 17篇 |
1995年 | 9篇 |
1994年 | 9篇 |
1993年 | 11篇 |
1992年 | 25篇 |
1991年 | 39篇 |
1990年 | 33篇 |
1989年 | 27篇 |
1988年 | 23篇 |
1987年 | 20篇 |
1986年 | 18篇 |
1985年 | 18篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 11篇 |
1977年 | 9篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1973年 | 11篇 |
1972年 | 9篇 |
排序方式: 共有3847条查询结果,搜索用时 15 毫秒
61.
62.
Maharaj DS Anoopkumar-Dukie S Glass BD Antunes EM Lack B Walker RB Daya S 《Journal of pineal research》2002,32(4):257-261
Ultraviolet (UV) light is known to induce the generation of free radicals in biological tissues such as skin. Of these free radicals, the O2-. and particularly the.OH radical can induce cellular damage including lipid peroxidation. Thus, the use of antioxidants to prevent such damage induced by UV irradiation has received much attention recently. One such antioxidant, which has the potential to be incorporated into sunscreens, is the pineal secretory product melatonin. One of the concerns of using melatonin in sunscreens is its photostability. In the present study, we investigated the photostability of melatonin subjected to UV irradiation. In addition, we used liquid chromatography mass spectrometry (LC-MS) to identify the degradants and we also assessed the ability of the degradants to inhibit O2-. generation as well as lipid peroxidation in rat brain homogenate. The results show that UV irradiation of melatonin (0.1 mg/mL) using a 400-W lamp for 2 hr caused a significant decline of melatonin to 18% of its original concentration after 20 min, with the decline continuing until the melatonin concentration reaches zero at 120 min. The LC-MS results show that the degradants of melatonin are 6-hydroxymelatonin and N1-acetyl-N2-formyl-5-methoxykynurenamine (AFMK). These degradants were able to provide equipotent activity against potassium cyanide (KCN)-induced superoxide generation compared to non-irradiated melatonin. Thus, the study shows that although melatonin is rapidly degraded by UV irradiation, the degradants retain antioxidant activity, making melatonin a likely candidate for inclusion in sunscreens. 相似文献
63.
Rafic Zaitoun Gerald Dorros Sriram S. Iyer Ruben F. Lewin 《Catheterization and cardiovascular interventions》1990,20(4):254-256
This case report describes the feasibility and potential benefit of the use of a high-speed rotational atherectomy device (the Rotablator?) in the treatment of renovascular hypertension in a patient with a recorded restenosis of an ostial renal artery lesion following standard balloon angioplasty. 相似文献
64.
65.
66.
67.
68.
69.
Rajamani D Thiel S Vajda S Camacho CJ 《Proceedings of the National Academy of Sciences of the United States of America》2004,101(31):11287-11292
We show that the mechanism for molecular recognition requires one of the interacting proteins, usually the smaller of the two, to anchor a specific side chain in a structurally constrained binding groove of the other protein, providing a steric constraint that helps to stabilize a native-like bound intermediate. We identify the anchor residues in 39 protein-protein complexes and verify that, even in the absence of their interacting partners, the anchor side chains are found in conformations similar to those observed in the bound complex. These ready-made recognition motifs correspond to surface side chains that bury the largest solvent-accessible surface area after forming the complex (> or =100 A2). The existence of such anchors implies that binding pathways can avoid kinetically costly structural rearrangements at the core of the binding interface, allowing for a relatively smooth recognition process. Once anchors are docked, an induced fit process further contributes to forming the final high-affinity complex. This later stage involves flexible (solvent-exposed) side chains that latch to the encounter complex in the periphery of the binding pocket. Our results suggest that the evolutionary conservation of anchor side chains applies to the actual structure that these residues assume before the encounter complex and not just to their loci. Implications for protein docking are also discussed. 相似文献
70.
T. D. Clemons M. Bradshaw P. Toshniwal N. Chaudhari A. W. Stevenson J. Lynch M.
W. Fear F. M. Wood K. Swaminathan Iyer 《RSC advances》2018,8(18):9661
An important histological difference between normal, uninjured dermis and scar tissue such as that found in keloid scars is the pattern (morphological architecture) in which the collagen is deposited and arranged. In the uninjured dermis, collagen bundle architecture appears randomly organized (or in a basket weave formation), whereas in pathological conditions such as keloid scar tissue, collagen bundles are often found in whorls or in a hypotrophic scar collagen is more densely packed in a parallel configuration. In the case of skin, a scar disables the dermis, leaving it weaker, stiff and with a loss of optimal functionality. The absence of objective and quantifiable assessments of collagen orientation is a major bottleneck in monitoring progression of scar therapeutics. In this article, a novel quantitative approach for analyzing collagen orientation is reported. The methodology is demonstrated using collagen produced by cells in a model scar environment and examines collagen remodeling post-TGFβ stimulation in vitro. The method is shown to be reliable and effective in identifying significant coherency differences in the collagen deposited by human keloid scar cells. The technique is also compared for analysing collagen architecture in rat sections of normal, scarred skin and tendon tissue. Results demonstrate that the proposed computational method provides a fast and robust way of analyzing collagen orientation in a manner surpassing existing methods. This study establishes this methodology as a preliminary means of monitoring in vitro and in tissue treatment modalities which are expected to alter collagen morphology.A novel technique for the fast and robust quantification of collagen architecture following scarring. 相似文献