全文获取类型
收费全文 | 4645篇 |
免费 | 176篇 |
国内免费 | 20篇 |
专业分类
耳鼻咽喉 | 120篇 |
儿科学 | 115篇 |
妇产科学 | 219篇 |
基础医学 | 533篇 |
口腔科学 | 31篇 |
临床医学 | 311篇 |
内科学 | 1304篇 |
皮肤病学 | 102篇 |
神经病学 | 295篇 |
特种医学 | 84篇 |
外科学 | 598篇 |
综合类 | 44篇 |
一般理论 | 1篇 |
预防医学 | 249篇 |
眼科学 | 70篇 |
药学 | 377篇 |
中国医学 | 4篇 |
肿瘤学 | 384篇 |
出版年
2023年 | 24篇 |
2022年 | 115篇 |
2021年 | 200篇 |
2020年 | 62篇 |
2019年 | 93篇 |
2018年 | 114篇 |
2017年 | 86篇 |
2016年 | 103篇 |
2015年 | 124篇 |
2014年 | 161篇 |
2013年 | 215篇 |
2012年 | 362篇 |
2011年 | 422篇 |
2010年 | 188篇 |
2009年 | 108篇 |
2008年 | 301篇 |
2007年 | 361篇 |
2006年 | 325篇 |
2005年 | 308篇 |
2004年 | 328篇 |
2003年 | 330篇 |
2002年 | 232篇 |
2001年 | 27篇 |
2000年 | 12篇 |
1999年 | 19篇 |
1998年 | 22篇 |
1997年 | 27篇 |
1996年 | 13篇 |
1995年 | 16篇 |
1994年 | 8篇 |
1993年 | 20篇 |
1992年 | 10篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1974年 | 3篇 |
1970年 | 4篇 |
1967年 | 4篇 |
1966年 | 3篇 |
排序方式: 共有4841条查询结果,搜索用时 16 毫秒
991.
Alicja Tymczewska Bliss Ursula Furtado Jacek Nowaczyk Katarzyna Hrynkiewicz Aleksandra Szydowska-Czerniak 《Materials》2021,14(11)
The use of industrial waste as a material for the development of natural innovative and active packaging is economically and environmentally appealing. The aim of this study was to develop and characterize active gelatin films incorporating rapeseed oil industry waste. Water (RM-WE) and methanolic (RM-MWE) extracts of rapeseed meal (RM) were used as active agents in film formulations. The active films were produced by a casting technique. The physicochemical, mechanical, optical, morphological, radical scavenging, and antibacterial properties of the films were analyzed. The addition of RM-WE and RM-MWE in the concentrations range between 4 and 12% promoted an increase of Young’s modulus (YM) and radical scavenging properties of films investigated by the direct QUick, Easy, New, CHEap and Reproducible procedure using 2,2-diphenyl-1-picrylhydrazyl (QUENCHERDPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (QUENCHERABTS) radicals. The antibacterial properties of films were examined against five bacterial strains: E. coli, S. enterica, M. luteus, L. monocytogenes, and S. aureus. Additionally, color and opacity of the control and fortified films differed significantly. The gelatin films with RM extracts are resistant to the microbial spoilage and could be used to produce active packaging for food that is vulnerable to rancidity effects. 相似文献
992.
This paper presents experimental investigations of reinforced concrete (RC) beams flexurally strengthened with carbon fiber reinforced polymer (CFRP) strips. Seven 3300 mm × 250 mm × 150 mm beams of the same design, with the tension reinforcement ratio of 1.01%, were tested. The beams differed in the way they were strengthened: one of the beams was the reference, two beams were passively strengthened as precracked (series B-I), two beams were passively strengthened as unprecracked (series B-II) and two beams were actively strengthened as unprecracked (series B-III). Moreover, the strengthening parameters differed between the particular series. The parameters were: CFRP strip cross-sectional areas (series B-I, B-II) or prestressing forces (series B-III). The beams were statically loaded, up to the assumed force value, in the three-point bending test and deflections at midspan were registered. After unloading the beams were suspended on flexible ropes (the free-free beam system) and their eigenfrequencies were measured using operational modal analysis (OMA). The static measurements (deflections) and the dynamic measurements (eigenfrequencies) were conducted for the adopted loading steps until failure. Static stiffnesses and dynamic stiffnesses were calculated on the basis of respectively the deflections and the eigenfrequencies. The qualitative and quantitative differences between the parameters are described. 相似文献
993.
994.
Andreas Glenthj Lasse H. Jakobsen Henrik Sengelv Syed A. Ahmad Kristian Qvist Annika Rewes Christian B. Poulsen Ulrik M. Overgaard Ingolf Mlle Marianne T. Severinsen Casper N. Strandholdt Jack Maibom Annette R. Kodahl Jesper Ryg Pernille Ravn Isik S. Johansen Sren N. Hels Sren Jensen‐Fangel Jacek Kisielewicz Lothar Wiese Marie Helleberg Ole Kirk Michael R. Clausen Henrik Frederiksen 《European journal of haematology》2021,106(1):72-81
995.
996.
997.
To explore the ultrastructure of elastic fibers in juvenile elastoma, three patients (two without osteopoikilosis and one under examination of bones and joints) were studied by routine electron microscopy. In addition to normal elastic fibers, all the patients also exhibited alterations in elastic fibers. The altered ultrastructures showed lucent, homogenous matrix without peripheral microfibrils. The homogenous matrix were seen in various extensions from the small protrusions of the normal elastic fibers to the complete replacement of the entire fibers. Collagen fibrils occasionally showed twisted figures. Normal shapes of dermal glycosaminoglycans were increased in number. It seems likely that the lucent, homogenous matrix without peripheral microfibrils are the characteristic changes of elastic fibers in juvenile elastoma. The alteration could be nevoid in nature. 相似文献
998.
Jacek Zaremba Hanna Mierzewska Zofia Lysiak Patricia Kramer Laurie J Ozelius Allison Brashear 《Movement disorders》2004,19(12):1506-1510
Rapid-onset dystonia-parkinsonism (RDP, DYT12, MIM 128235) is a rare autosomal dominant movement disorder characterized by abrupt onset of slow, dystonic movements and prominent bulbar features. Three families and 1 isolated case have been described in the literature, and linkage to markers on chromosome 19q13 have been reported. Here, we describe the clinical features in a fourth family (the second in Europe) with 4 affected members, suggesting that RDP may be misdiagnosed for years and/or may mimic other dystonic/parkinsonian syndromes. By using haplotype analysis, we show that the family is consistent with linkage to markers on chromosome 19q13. 相似文献
999.
The ability of bifurcating processing units and their networks to rapidly switch between different dynamic modes has been used in recent research efforts to model new computational properties of neural systems. In this spirit, we devise a bifurcating neuron based on control of chaos collapsing to a period-3 orbit in the dynamics of a quadratic logistic map (QLM). Proposed QLM3 neuron is constructed with the third iterate of QLM and uses an external input, which governs its dynamics. The input shifts the neuron's dynamics from chaos to one of the stable fixed points. This way the inputs from certain ranges (clusters) are mapped to stable fixed points, while the rest of the inputs is mapped to chaotic or periodic output dynamics. It has been shown that QLM3 neuron is able to learn a specific mapping by adaptively adjusting its bifurcation parameter, the idea of which is based on the principles of parametric control of logistic maps [Proceedings of the International Symposium on Nonlinear Theory and its Applications (NOLTA'97), Honolulu, HI, 1997; Proceedings of SPIE, 2000]. Learning algorithm for the bifurcation parameter is proposed, which employs the error gradient descent method. 相似文献
1000.
Jacek Kiljański Micha? Ambroziak Janusz Pachucki Krystian Jazdzewski Wieslaw Wiechno Elzbieta Stachlewska Barbara Górnicka Magdalena Bogdańska Janusz Nauman Zbigniew Bartoszewicz 《Thyroid》2005,15(7):645-652
Sialylation of cell components is an important immunomodulating mechanism affecting cell response to hormones and adhesion molecules. To study alterations in sialic acid metabolism in Graves' disease (GD) we measured the following parameters in various human thyroid tissues: lipid-bound sialic acid (LBSA) content, ganglioside profile, total sialyltransferase activity, and the two major sialyltransferase mRNAs for sialyltransferase-1 (ST6Gal I) and for sialyltransferase-4A (ST3Gal I). Fragments of toxic thyroid nodules (TN), nontoxic thyroid nodules (NN) and nontumorous tissue from patients with nodular goiter or thyroid cancer were used as a control (C). The LBSA content and sialyltransferase activity were the highest in the GD group (164 +/- 4.44 versus 120 +/- 2.00 nmoL/g, p = 0.005 and 1625 +/- 283.5 versus 324 +/- 54.2 cpm/mg of protein, p < 0.005 compared to control group C). Ganglioside profile in the GD group was similar to that in control tissues. Sialyltransferase- 1 mRNA and sialyltransferase-4A mRNA levels were significantly higher in the GD group than in the control group (12.52 +/- 6.90 versus 2.54 +/- 1.24 arbitrary units, p < 0.005 and 2,49 +/- 1.16 versus 1.23 +/- 0.46 arbitrary units, p < 0.05, respectively). There was a positive correlation between the increased sialyltransferase-1 mRNA level and the TSH-receptor antibody titer determined by the TRAK test. These results indicate that sialyltransferases expression and activity are increased in GD. Exact mechanism of this upregulation remains unknown, though one of possible explanations is the activation of the thyrotropin (TSH) receptor. 相似文献