全文获取类型
收费全文 | 1795篇 |
免费 | 106篇 |
国内免费 | 5篇 |
专业分类
耳鼻咽喉 | 11篇 |
儿科学 | 83篇 |
妇产科学 | 18篇 |
基础医学 | 197篇 |
口腔科学 | 48篇 |
临床医学 | 153篇 |
内科学 | 481篇 |
皮肤病学 | 49篇 |
神经病学 | 59篇 |
特种医学 | 23篇 |
外科学 | 276篇 |
综合类 | 23篇 |
一般理论 | 5篇 |
预防医学 | 67篇 |
眼科学 | 138篇 |
药学 | 151篇 |
中国医学 | 15篇 |
肿瘤学 | 109篇 |
出版年
2023年 | 25篇 |
2022年 | 65篇 |
2021年 | 120篇 |
2020年 | 57篇 |
2019年 | 68篇 |
2018年 | 93篇 |
2017年 | 79篇 |
2016年 | 66篇 |
2015年 | 95篇 |
2014年 | 118篇 |
2013年 | 111篇 |
2012年 | 170篇 |
2011年 | 185篇 |
2010年 | 86篇 |
2009年 | 65篇 |
2008年 | 91篇 |
2007年 | 98篇 |
2006年 | 81篇 |
2005年 | 66篇 |
2004年 | 51篇 |
2003年 | 47篇 |
2002年 | 42篇 |
2001年 | 5篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1985年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有1906条查询结果,搜索用时 0 毫秒
51.
Subashini Gnanasekar Prashant Sonar Sagar M. Jain Soon Kwan Jeong Andrews Nirmala Grace 《RSC advances》2020,10(67):41177
A vanadium nitride xerogel (VNXG) was synthesised by a simple and effective method of ammonialising a vanadium pentoxide xerogel at a higher temperature. Xerogel-structured materials possess salient features such as high surface area, tunable porosity and pore size that result in enhancing the catalytic activity by a fast electron-transport pathway and increase electrolyte diffusion channels. Metal nitrides are reported as promising alternate low-cost counter electrodes to replace the conventional and expensive platinum (Pt) counter electrode. Though few studies are reported on aerogel-based CEs for DSSCs, the present work is the first attempt to synthesize and evaluate the performance of xerogel-structured metal nitrides as counter electrode materials for dye-sensitized solar cells. The synthesized material was well characterized for its structural and morphological characteristics and chemical constituents by photoelectron spectroscopy. Finally, the VNXG was tested for its electrocatalytic performance as a choice of counter electrodes for dye-sensitized solar cells (DSSCs). The photo-current studies were performed under standard 1 SUN, class AAA-simulated illumination with AM1.5G. The consolidated results revealed that the vanadium nitride xerogel exhibited good photocatalytic activity and low charge transfer resistance. This identified it as a promising low-cost counter electrode (CE) material for dye-sensitized solar cells. The photo-current conversion efficiency of the vanadium nitride xerogel CE-based DSSC reached 5.94% comparable to that of the conventional thermal decomposed Pt CE-based DSSC, 7.38% with the same iodide/triiodide electrolyte system. Moreover, the 28 days stability study of VNXG CE DSSCs provided an appreciably stable performance with 37% decrement in the PCE under the same test condition.A vanadium nitride xerogel (VNXG) was synthesised by a simple and effective method of ammonialising a vanadium pentoxide xerogel at a higher temperature. The electrochemical and photo-current studies were performed towards a counter electrode for DSSC. 相似文献
52.
53.
54.
Corneli HM Zorc JJ Mahajan P Majahan P Shaw KN Holubkov R Reeves SD Ruddy RM Malik B Nelson KA Bregstein JS Brown KM Denenberg MN Lillis KA Cimpello LB Tsung JW Borgialli DA Baskin MN Teshome G Goldstein MA Monroe D Dean JM Kuppermann N;Bronchiolitis Study Group of the Pediatric Emergency Care Applied Research Network 《The New England journal of medicine》2007,357(4):331-339
55.
Aim
The main aim of this study was to assess the psychological consequences that displacement brings into the lives of India’s tribal populations, specifically, in the form of mental illness.Subject and methods
Literature review.Results
The impact of forced displacement on the mental state of tribal populations is significant and multi-faceted. In spite of sufficient evidence indicating the extent of mental health challenges, the Governmental response in India has been completely missing. Some of the challenges in the path of Indian health providers are poor diagnostic facilities, lack of psychiatric epidemiological data for tribal populations, and culturally inappropriate instruments. Scientists and practitioners can play an important role in bridging the knowledge gap in the field.Conclusion
It is necessary to perceive the mental health status of displaced tribal populations within the larger framework of social justice. A strictly biomedical approach is insufficient when the individuals seeking help are under constant stress. Thus, a mental health program is needed for tribal people that offers a perspective broad enough to address the needs of individuals and the local worlds in which they live.56.
57.
Prashant N. Mohite Bartlomiej Zych Nicholas R. Banner Andre R. Simon 《Artificial organs》2014,38(4):276-281
Chronic heart failure is a progressive and eventually fatal illness. Although the disease cannot be cured and treatment is symptom oriented, most of the patients benefit from optimum medical treatment. Patients with rapid deterioration in chronic advanced heart failure refractory to medical treatment need inotropic support and may need intra‐aortic balloon pump to maintain circulatory support, which of course cannot be prolonged beyond a certain limit. The outcome of heart transplant and long‐term ventricular assist device (VAD) in such patients is poor. The short‐term mechanical circulatory support (MCS) offered to such patients not only provides effective circulatory support and stabilizes them hemodynamically, but also halts the ensuing or reverts the established end‐organ failure. As the name suggests, the short‐term MCS offers support for the short term, usually less than a month. Although some patients with acute heart failure experience recovery of myocardial function with short‐term MCS support, others become dependent. These patients, stabilized and “stuck” with short‐term MCS, can be “rescued” with long‐term VAD or heart transplantation. Both the procedures, when done in this special situation, have their inherent advantages, disadvantages, and complications and hence need the careful consideration about the choice of the procedure. We have tried to elucidate this situation by considering the advantages and disadvantages of both options. 相似文献
58.
59.
Srihari S. Naidu MD FACC FAHA FSCAI J. Dawn Abbott MD FACC FSCAI Jayant Bagai MD FSCAI James Blankenship MD MSc MSCAI Santiago Garcia MD FACC FSCAI Sohah N. Iqbal MD FACC FSCAI Prashant Kaul MD FSCAI Matheen A. Khuddus MD FACC FSCAI Lorrena Kirkwood RN BSN MS Steven V. Manoukian MD FACC FAHA FSCAI Manesh R. Patel MD FAHA Kimberly Skelding MD FACC FAHA FSCAI David Slotwiner MD FACC FHRS Rajesh V. Swaminathan MD FSCAI Frederick G. Welt MD FACC FSCAI Daniel M. Kolansky MD FACC FAHA FSCAI 《Catheterization and cardiovascular interventions》2021,98(2):255-276
The current document commissioned by the Society for Cardiovascular Angiography and Interventions (SCAI) and endorsed by the American College of Cardiology, the American Heart Association, and Heart Rhythm Society represents a comprehensive update to the 2012 and 2016 consensus documents on patient-centered best practices in the cardiac catheterization laboratory. Comprising updates to staffing and credentialing, as well as evidence-based updates to the pre-, intra-, and post-procedural logistics, clinical standards and patient flow, the document also includes an expanded section on CCL governance, administration, and approach to quality metrics. This update also acknowledges the collaboration with various specialties, including discussion of the heart team approach to management, and working with electrophysiology colleagues in particular. It is hoped that this document will be utilized by hospitals, health systems, as well as regulatory bodies involved in assuring and maintaining quality, safety, efficiency, and cost-effectiveness of patient throughput in this high volume area. 相似文献
60.
ZnO has industrial utility as a solid sorbent for the removal of polluting sulfur compounds from petroleum-based fuels. Small ZnO nanoparticles may be more effective in terms of sorption capacity and ease of sulfidation as compared to bulk ZnO. Motivated by this promise, here, we study the sulfidation of ZnO NPs and uncover the solid-state mechanism of the process by crystallographic and optical absorbance characterization. The wurtzite-structure ZnO NPs undergo complete sulfidation to yield ZnS NPs with a drastically different zincblende structure. However, in the early stages, the ZnO NP lattice undergoes only substitutional doping by sulfur, while retaining its wurtzite structure. Above a threshold sulfur-doping level of 30 mol%, separate zincblende ZnS grains nucleate, which grow at the expense of the ZnO NPs, finally yielding ZnS NPs. Thus, the full oxide to sulfide transformation cannot be viewed simply as a topotactic place-exchange of anions. The product ZnS NPs formed by nucleation-growth share neither the crystallographic structure nor the size of the initial ZnO NPs. The reaction mechanism may inform the future design of nanostructured ZnO sorbents.In the sulfidation of small ZnO nanoparticles, the nanoparticles first undergo sulfur doping followed by the nucleation-growth of ZnS domains.Zinc oxide (ZnO) nanoparticles (NPs), due to their cost-effectiveness and biodegradability, have a multitude of applications1–3 including coatings4–8 and pigments,9,10 catalysis,11,12 energy storage,13,14 and environmental remediation.15–22 ZnO NPs have particular appeal as sorbents for scavenging polluting sulfur compounds such as mercaptans and hydrogen sulfide (H2S) from petroleum-based fuels:23–27 ZnO + H2S → ZnS + H2O. Lattice O2− in the ZnO is replaced with S2− scavenged from the pollutant. Bulk powders of ZnO have already been used for adsorptive removal of H2S,28,29 but NPs have specific advantages. With smaller grain sizes, mass transport limitations are lifted.23 Whereas sulfidation is limited to the surface of bulk ZnO, with NPs, the entire mass of ZnO can undergo sulfidation, enabling high sorbent capacity.23 Volume and morphology changes resulting from restructuring of the solid can also be more easily accommodated with NPs,23 allowing regenerable use of the sorbent. Finally, the high specific surface area of NPs allows more enhanced kinetics of the sulfidation reaction, potentially facilitating much lower desulfurization temperatures as compared to the conventional operating temperatures of 650–800 °C.23,29In this context, small few-nm size ZnO NPs can be expected to be particularly promising, but it is important to understand the manner in which these NPs undergo sulfidation. The structural mechanism of the sulfidation process30 may have critical differences compared to bulk ZnO powders or even larger NPs of tens of nm in size24 and may therefore influence sorbent design. In a seminal study, Park et al.30 studied the sulfidation of hexagonal-shaped 14 nm ZnO nanocrystals (NCs) at high temperature (235 °C) using hexamethyldisilathiane. The reaction was found to involve the anion exchange of O2− with S2− in the NC lattice. The overall shape and crystallography of ZnS NCs was templated by the initial ZnO NCs. However, due to the faster outward diffusion of Zn2+ as compared to the inward diffusion of S2−, the exchange reaction was accompanied by a nanoscale Kirkendall phenomenon, as a result of which the ZnS NCs formed were hollow.Here, we track the step-wise sulfidation of smaller (ca. 5 nm) ZnO NPs using optical spectroscopy and X-ray crystallography. Prior to the onset of sulfidation, O2− in wurtzite ZnO NPs undergoes substitutional doping with S2− without any major change in its structure. Upon reaching a critical concentration of sulfur doping, separate zincblende ZnS grains form and grow into ZnS NPs. Thus, the sulfidation of these small ZnO NPs studied here is not simply a topotactic or templated place-exchange of anions; rather the nucleation and growth of a separate ZnS crystallite is involved in the latter stages. 相似文献