全文获取类型
收费全文 | 4711篇 |
免费 | 278篇 |
国内免费 | 29篇 |
专业分类
耳鼻咽喉 | 45篇 |
儿科学 | 133篇 |
妇产科学 | 130篇 |
基础医学 | 811篇 |
口腔科学 | 77篇 |
临床医学 | 481篇 |
内科学 | 888篇 |
皮肤病学 | 158篇 |
神经病学 | 563篇 |
特种医学 | 156篇 |
外科学 | 335篇 |
综合类 | 43篇 |
一般理论 | 3篇 |
预防医学 | 353篇 |
眼科学 | 73篇 |
药学 | 402篇 |
中国医学 | 43篇 |
肿瘤学 | 324篇 |
出版年
2023年 | 44篇 |
2022年 | 120篇 |
2021年 | 209篇 |
2020年 | 109篇 |
2019年 | 168篇 |
2018年 | 147篇 |
2017年 | 106篇 |
2016年 | 151篇 |
2015年 | 149篇 |
2014年 | 215篇 |
2013年 | 253篇 |
2012年 | 433篇 |
2011年 | 458篇 |
2010年 | 254篇 |
2009年 | 175篇 |
2008年 | 348篇 |
2007年 | 318篇 |
2006年 | 272篇 |
2005年 | 245篇 |
2004年 | 205篇 |
2003年 | 175篇 |
2002年 | 160篇 |
2001年 | 40篇 |
2000年 | 23篇 |
1999年 | 40篇 |
1998年 | 33篇 |
1997年 | 18篇 |
1996年 | 11篇 |
1995年 | 12篇 |
1994年 | 14篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1977年 | 3篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 3篇 |
1971年 | 3篇 |
排序方式: 共有5018条查询结果,搜索用时 15 毫秒
61.
62.
Double orifice mitral valve; a coincidental finding. 总被引:1,自引:0,他引:1
Iris C D Westendorp H A C M de Bruin-Bon Jana Hrudova 《European journal of echocardiography》2006,7(6):463-464
A double orifice mitral valve (DOMV) represents a rare congenital malformation characterised by two valve orifices with two separate subvalvular apparatus. This case demonstrates the necessity of careful imaging of the mitral valve apparatus, not only in patients with atrioventricular septal defects, but also in patients with congenital left obstructive heart disease. 相似文献
63.
64.
A Pantetheinase-Resistant Pantothenamide with Potent,On-Target,and Selective Antiplasmodial Activity
Cristiano J. Macuamule Erick T. Tjhin Collins E. Jana Leanne Barnard Lizbé Koekemoer Marianne de Villiers Kevin J. Saliba Erick Strauss 《Antimicrobial agents and chemotherapy》2015,59(6):3666-3668
Pantothenamides inhibit blood-stage Plasmodium falciparum with potencies (50% inhibitory concentration [IC50], ∼20 nM) similar to that of chloroquine. They target processes dependent on pantothenate, a precursor of the essential metabolic cofactor coenzyme A. However, their antiplasmodial activity is reduced due to degradation by serum pantetheinase. Minor modification of the pantothenamide structure led to the identification of α-methyl-N-phenethyl-pantothenamide, a pantothenamide resistant to degradation, with excellent antiplasmodial activity (IC50, 52 ± 6 nM), target specificity, and low toxicity. 相似文献
65.
This contribution discusses the ablation phenomena observed during laser treatment of carbon fiber-reinforced plastics (CFRPs) with pulsed lasers observed employing laser sources with wavelengths of 355 nm, 1064 nm and 10.6 µm and pulse durations from picoseconds (11 ps) to microseconds (14 µs) are analyzed and discussed. In particular, the threshold fluence of the matrix material epoxy (EP) and the damage threshold of CFRP were calculated. Moreover, two general surface pretreatment strategies are investigated, including selective matrix removal and structure generation through indentation (ablation of both, matrix material and fibers) with a cross-like morphology. The surfaces obtained after the laser treatment are characterized by means of optical and scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy is employed for the analysis of composite and constituent materials epoxy and carbon fibers. As a result, different ablation mechanisms, including evaporation and delamination are observed, depending on the employed laser wavelength and pulse duration. For both 355 nm and 1064 nm wavelength, the laser radiation produces only partial ablation of the carbon fibers due to their higher absorption coefficient compared to the epoxy matrix. Although a selective matrix removal without residues is achieved using the pulsed CO2 laser. Differently, both constituent materials are ablated with the nanosecond pulsed UV laser, producing indentations. The sum of the investigations has shown that existing theories of laser technology, such as the ablation threshold according to Liu et al., can be applied to composite materials only to a limited extent. Furthermore, it has been found that the pronounced heterogeneity of CFRP mostly leads to an inhomogeneous ablation result, both when creating grooves and during selective matrix removal, where the carbon fibers influence the ablation result by their thermal conductivity, depending on fiber direction. Finally, despite the material inhomogeneity, a scanning strategy has been developed to compensate the heterogeneous ablation results regarding structure depth, width and heat affected zone. 相似文献
66.
In this work we report the use of benzophenone (BP) for the synthesis of a palladium (Pd) embedded on reduced graphene oxide (rGO) nanocomposite (Pd/rGO) using a simple aqueous solution and UV irradiation. The simple and facile evolution of thermodynamically unstable branched Pd(0) nanodendrites was achieved by BP photoactivation, circumventing the growth of more stable nanomorphologies. The synthesis of Pd(0)-embedded rGO nanosheets (PRGO-nd) was made possible by the simultaneous reduction of both the GO scaffold and PdCl2 by introducing BP into the photoactivation reaction. The nanocomposites obtained in the absence of BP were common triangular and twinned Pd(0) structures which were also implanted on the rGO scaffold (PRGO-nt). The disparity in morphologies presumably occurs due to the difference in the kinetics of the reduction of Pd2+ to Pd0 in the presence and absence of the BP photoinitiator. It was observed that the PRGO-nd was composed of dense arrays of multiple Pd branches around nucleation site which exhibited (111) facet, whereas PRGO-nt showed a mixture of (100) and (111) facets. On comparing the catalytic efficiencies of the as-synthesized nanocatalysts, we observed a superiority in efficiency of the thermodynamically unstable PRGO-nd nanocomposite. This is due to the evolved active facets of the dendritic Pd(0) morphology with its higher surface area, as testified by Brunauer–Emmett–Teller (BET) analysis. Since both PRGO-nd and PRGO-nt contain particles of similar size, the dents and grooves in the structure are the cause of the increase in the effective surface area in the case of nanodendrites. The unique dendritic morphology of the PRGO-nd nanostructures makes them a promising material for superior catalysis, due to their high surface area, and the high density of surface atoms at their edges, corners, and stepped regions. We investigated the efficiency of the as-prepared PRGO-nd catalyst in the Suzuki–Miyaura coupling reaction and showed its proficiency in a 2 h reaction at 60 °C using 2 mol% catalyst containing 0.06 mol% active Pd. Moreover, the electrochemical efficiency for the catalytic hydrogen evolution reaction (HER) was demonstrated, in which PRGO-nd provided a decreased overpotential of 68 mV for a current density of 10 mA cm−2, a small Tafel slope of 57 mV dec−1 and commendable stability during chronoamperometric testing for 5 h.Benzophenone photoinitiator aided synthesis of Pd-nanodendrite embedded rGO nanocatalyst possessing superior potential in C–C coupling reaction and fuel cell application. 相似文献
67.
Renata Mojzikova Pavla Koralkova Dusan Holub Zuzana Zidova Dagmar Pospisilova Jaroslav Cermak Zuzana Striezencova Laluhova Karel Indrak Martina Sukova Martina Partschova Jana Kucerova Monika Horvathova Vladimir Divoky 《British journal of haematology》2014,165(4):556-563
Pyruvate kinase (PK) deficiency is an iron‐loading anaemia characterized by chronic haemolysis, ineffective erythropoiesis and a requirement for blood transfusion in most cases. We studied 11 patients from 10 unrelated families and found nine different disease‐causing PKLR mutations. Two of these mutations ‐ the point mutation c.878A>T (p.Asp293Val) and the frameshift deletion c.1553delG (p.(Arg518Leufs*12)) ‐ have not been previously described in the literature. This frameshift deletion was associated with an unusually severe phenotype involving neonatal hyperferritinaemia that is not typical of PK deficiency. No disease‐causing mutations in genes associated with haemochromatosis could be found. Inappropriately low levels of hepcidin with respect to iron loading were detected in all PK‐deficient patients with increased ferritin, confirming the predominant effect of accelerated erythropoiesis on hepcidin production. Although the levels of a putative hepcidin suppressor, growth differentiation factor‐15, were increased in PK‐deficient patients, no negative correlation with hepcidin was found. This result indicates the existence of another as‐yet unidentified erythroid regulator of hepcidin synthesis in PK deficiency. 相似文献
68.
69.
70.