首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   17757篇
  免费   1326篇
  国内免费   417篇
耳鼻咽喉   458篇
儿科学   71篇
妇产科学   185篇
基础医学   932篇
口腔科学   1311篇
临床医学   1183篇
内科学   1605篇
皮肤病学   1423篇
神经病学   378篇
特种医学   558篇
外国民族医学   1篇
外科学   4014篇
综合类   2086篇
现状与发展   1篇
预防医学   373篇
眼科学   3513篇
药学   786篇
  8篇
中国医学   279篇
肿瘤学   335篇
  2024年   70篇
  2023年   316篇
  2022年   660篇
  2021年   783篇
  2020年   622篇
  2019年   509篇
  2018年   506篇
  2017年   579篇
  2016年   665篇
  2015年   562篇
  2014年   1030篇
  2013年   1136篇
  2012年   870篇
  2011年   997篇
  2010年   856篇
  2009年   868篇
  2008年   837篇
  2007年   818篇
  2006年   756篇
  2005年   671篇
  2004年   619篇
  2003年   525篇
  2002年   437篇
  2001年   453篇
  2000年   367篇
  1999年   281篇
  1998年   304篇
  1997年   293篇
  1996年   254篇
  1995年   206篇
  1994年   214篇
  1993年   191篇
  1992年   165篇
  1991年   155篇
  1990年   127篇
  1989年   113篇
  1988年   103篇
  1987年   107篇
  1986年   87篇
  1985年   106篇
  1984年   92篇
  1983年   60篇
  1982年   47篇
  1981年   38篇
  1980年   26篇
  1979年   7篇
  1978年   9篇
  1977年   1篇
  1976年   1篇
  1974年   1篇
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
101.
用国产WD-L92型染料激光机,对56例,61眼施行激光虹膜透切术。其中40眼行周边虹膜透切术,完全切穿率为92.5%;9例白内障术后瞳孔上移行光学虹膜切除术疗效满意。对其它一些病例也取得一定疗效。认为染料激光具有输出功率大,能量及光斑可调的优点,易一次击穿虹膜,应用于虹膜透切术疗效肯定。  相似文献   
102.
Summary A comparative study was undertaken to investigate the application of a specially adapted microsurgical Neodymium Yag Laser system with a wavelength of 1,319 m and a CO2 laser system for laser assisted microvascular end-to-end anastomosis (LAMA) of the rat femoral artery. Conventionally sutured anastomoses served as controls. Postoperative investigations included patency tests, light microscopy and tensile strength measurements. Both laser systems seem to be equally suitable for LAMA: The patency rates do not differ from those of sutured anstomoses and formation of microscopically small aneurysms occurred predominantly in control animals and only once in laser groups. The clamp time needed for LAMA was half the time that was needed for sutured anastomoses. Wound healing in all groups was similar with less fibrotic reactions and less foreign body granulomas in laser groups. At all intervals tensile strength was significantly higher for sutured anastomoses while differences between the CO2- and the ND: Yag-laser groups were not statistically significant. Potential applications in urology include microvascular anastomoses in erectile dysfunction, pediatric and reconstructive urology.Contains parts of a dissertation  相似文献   
103.
Injury associated with laser-induced tissue ablation may be reduced by using pulsed energy delivery at low repetition rates, as opposed to using continuous wave energy delivery. This study was designed to examine the similarities and differences between these two systems as regards the healing process, and to examine whether one is superior to the other. In order to test this postulate, the healing response of normal and atherosclerotic aorta were examined after exposure in vivo to argon and excimer (XeCl 308 nm) laser radiation in hypercholesterolemic swine. Swine were fed hyperlipidemic diets for eight months following balloon denudation of the descending aorta. Following general anaesthetic, the descending aorta was isolated and laser burns were made on both normal and atherosclerotic intima using a continuous wave argon laser delivered through a 50 diameter quartz fibre, and a XeCl excimer laser carried through a 1 mm diameter fibre. Energy levels of 3 to 5 J were applied with the argon laser. The pulse duration for the excimer laser was 30 ns and craters were produced using 10 to 60 pulses at a repetition rate of 20 Hz and an energy density of 2 J cm–2.Forty-eight hours after laser application, craters created by both lasers were filled with thrombus material. Argon burns were surrounded by thermal and acoustic injury which was not seen with excimer burns. Three weeks after laser application all crater surfaces were reconstituted. Unlike the excimer burns, argon craters demonstrated necrosis well beyond the crater margins and were characterized by multinucleate giant-cell reaction surrounding char debris. By nine weeks both excimer and argon laser burns were covered by fibrous tissue but could be distinguished by the fact that char debris and subjacent tissue injury arose with the argon burns.The results suggest that both lasers can be used to remove focal atherosclerotic plaque from arteries without inducing excessive thrombogenicity. Rapid healing is observed with both; however, damage to surrounding tissue is significantly greater with a continuous energy delivery laser as opposed to pulsed energy delivery.Work supported in part by: Heart and Stroke Foundation of Ontario, Grant-in-Aid No. 5-17  相似文献   
104.
Laser-induced fluorescence (LIF) spectroscopy can only be used for laser angioplasty guidance if high-power laser ablation does not significantly alter the pattern of tissue fluorescence. Although the spectra of normal and atherosclerotic arteries differ, the change in fluorescence spectra following laser angioplasty has not been well studied. Therefore, the purpose of this study was to assess whether laser-induced fluorescence spectroscopy could guide selective laser ablation of atherosclerotic plaque and, if so, to develop a quantitative LIF score that could be used to control a "smart" laser angioplasty system. Baseline LIF spectroscopy of 50 normal and 50 atherosclerotic human aortic specimens was performed using an optical fiber coupled to a He-Cd laser and optical multichannel analyzer. LIF was then serially recorded during erbium:YAG laser ablation of 27 atherosclerotic specimens. Laser ablation was terminated when the arterial LIF spectrum visually appeared normal. Histologic analysis revealed a mean initial plaque thickness of 1,228 +/- 54 microns and mean residual plaque thickness of 198 +/- 27 microns. Ablation of the media occurred in only three specimens. A discriminant function was derived to discriminate atherosclerotic from normal tissue for computer guidance of laser angioplasty. The LIF score, derived from stepwise multivariate linear regression analysis of the LIF spectra, correctly classified 93% of aortic specimens. The spectra obtained from the atherosclerotic specimens subjected to fluorescence-guided laser revealed a change in score from "atherosclerotic" to "normal" following plaque ablation. Seven atherosclerotic specimens were subjected to laser angioplasty with on-line computer control using the LIF score. Mean initial plaque thickness was 1,014 +/- 86 microns, and mean residual plaque thickness was 78 +/- 29 microns. There was no evidence of ablation of the media. Therefore, LIF guidance of laser ablation resulted in minimal residual plaque without arterial perforation. These findings support the feasibility of an LIF-guided laser angioplasty system for selective atherosclerotic plaque ablation.  相似文献   
105.
Visual acuity, color vision, pattern-visual-evoked-potentials (P-VEPs) and pattern-electroretinograms (P-ERGs) were measured in 13 diabetic subjects before, and 24 hours and 5 weeks after blue-green argon laser treatment. As control, the same examinations were performed in 7 normal subjects and 7 diabetic patients before and after slit lamp examination with the Goldman three mirror contact lens.Visual acuity and P-ERG amplitudes were significantly reduced one day after the laser treatment, while 5 weeks after the laser coagulation, visual acuity and P-ERG amplitudes recovered to pretreatment values. The control group showed no significant changes after slit lamp examination. Since fluorescein angiography revealed no macular changes after laser treatment, the possibility of a reversible functional light damage after blue-green argon laser coagulation (ALC) is discussed.This study was supported by the Medizinisch - Wissenschaftlicher Fonds des Bürgermeisters der Bundeshauptstadt Wien.  相似文献   
106.
5-羟色胺(5-HT)参与舌和面口部精细运动的调节。5-HT对舌下神经运动神经元功能的调控表现为兴奋性作用。本文首先采用免疫组化方法,在光镜下观察了大鼠舌下神经核内5-HT免疫阳性纤维的形态和分布特征。又进一步采用荧光逆行追踪结合固定脑片细胞内LuciferYellow染色和荧光免疫组织化学染色,通过共聚焦激光扫描显微镜观察了伸舌肌(颏舌肌、颏舌骨肌)和缩舌肌(茎突舌肌)运动神经元与5-HT免疫阳性纤维及其终末的解剖学关系。结果证明:舌下神经核有较丰富的5-HT阳性纤维,以尾侧段的背侧部和吻侧段的腹侧部较为密集;根据纤维及其膨体的形态特征,本文将此阳性纤维分为三种类型。5-HT免疫阳性膨体样纤维及其终末与舌下运动神经元的胞体、树突分枝和轴丘及轴突起始段形成紧密接触;这些接触多呈不均匀的簇状(由2~7个紧密接触点组成)分布。定量分析发现:在额舌肌神经元和茎突舌肌神经元,除少量分布在胞体(密度为3.4~6.7/1000μm2)外,主要分布在近段和中段树突分权处附近;但是在颏舌骨肌神经元则集中分布在跑体(密度为10.8~17.6/1000μm2)和近侧树突上。以上所见提示:5-HT对舌下神经核整体行为的调节在不同功能的亚核可能有所选择;5-HT调制舌下运动神经元兴奋性的方式可  相似文献   
107.
目的比较研究He-Ne激光、微波、红外线和TDP灯照射对高血粘的影响,探索能否利用He-Ne激光、微波、红外线和TDP灯照射降低血液粘度,改善血循环.方法每份血样等分5份,1份作对照,对另外4份分别作He-Ne激光、微波、红外线和TDP灯照射处理.结果高血粘血样经He-Ne激光、微波、红外线和TDP灯照射作用后,全血表观粘度η降低(P<0.01)、红细胞电泳率EPM加快(P<0.01),血沉速度ESR提高(P<0.01),一氧化氮、全血黏度、全血还原黏度降低(P<0.01).红细胞变形指数降低(P<0.01),红细胞聚集时间增加(P<0.01),红细胞压积降低(P<0.01),纤维蛋白降低(P<0.01).结论He-Ne激光、微波、红外线和TDP灯照射能改善高血粘血样的流变特性.而且激光效果最好,依次是TDP灯、微波和红外线.进一步了解物理与临床治疗的密切关系.  相似文献   
108.

Background

Group B Streptococcus (GBS) is an important invasive pathogen in neonates, pregnant women and the elderly. Serotype VI GBS, which has been rarely reported globally, has emerged as a significant pathogen in Asia. However, traditional serologic latex agglutination (LA) methods may fail to type isolates that lack of or low expression of CPS.

Methods

A total of 104 GBS strains were analyzed by MALDI-TOF MS. Multiplex PCR and multilocus sequence typing (MLST) were also performed to confirm their strains. The protein markers were purified with gel electrophoresis and LC-column, followed by identification with nanoLC–MS/MS analysis.

Results

Protein peak of 6251-Da was appeared in most (20/24, 92%) serotypes VI (94% ST-1 or single locus variant of ST-1), and protein peak of 6891-Da was appeared in most serotypes III (15/18, 83%) and Ib (19/23, 83%) strains. The protein peak of 6251-Da and 6891-Da were identified as CsbD family protein and UPF0337 protein gbs0600, respectively.

Conclusions

The protein peak of 6251 Da may play a role of emergence of ST-1 clone, serotype VI GBS in central Taiwan and could be useful in rapid identifying invasive serotype VI from III isolates, which is hardly achieved by LA.  相似文献   
109.
Summary: Homopolymers of a bis‐trifluorocarbinol substituted norbornene ( 1 ) (α,α‐bis(trifluoromethyl)bicyclo[2.2.1]hept‐5‐ene‐2‐ethanol or HFANB) and copolymers of 1 with t‐butyl ester of 5‐carboxylic acid ( 2 , t‐BuEsNB) were produced using palladium catalysts and olefinic chain transfer agents such as 1‐hexene and ethylene to control molecular weight. However, these low‐molecular‐weight polymers exhibited relatively low optical transparencies at 193 nm. In fact, the opacity (measured as optical densities in absorbance units per micron) of thin films of these homo‐ and co‐polymers was inversely proportional to their molecular weight. This relationship is consistent with an end group contribution to the film opacity. Spectroscopic analysis of these polymers by 1H NMR and MALDI‐TOF MS confirmed that 1‐hexene and ethylene chain transfer agents generated olefin‐terminated vinyl addition polymers. The olefinic end group contribution to optical density can be eliminated by appropriate chemical modification. Both epoxidation and hydrogenation of the polymer olefinic end groups generated very low optical density materials, independent of molecular weight, that are suitable as 193‐nm photoresist binder resins.

End group modification of vinyl and hexenyl‐terminated homopolymers of 1 by epoxidation or hydrogenation.  相似文献   

110.
The action of local laser injury to the microvessels on the frequency of lodgment of tumor cells and on the ability of the cells to migrate from the lumen of the vessel was studied. A television microscope with video tape recorder and UV-laser were used. Cells of a Zajdela's ascites hepatoma were injected into the blood stream of a rat. Lodgment of tumor cells in the mesenteric vessels was observed infrequently (11%). The lodged cells adhered to the vessel wall and migrated from its lumen. Injury to the vessel wall by the laser beam led to the formation of microthrombi and to an increase in the frequency of lodging of the tumor cells in the vessels: 82% instead of 11%. The frequency of migration of cells from the lumen of the vessel under these circumstances, however, was reduced. The results confirm the role of microthrombus formation in metastasization; however, the role of microthrombus formation mav be exerted in different directions for although the frequency of adhesion of the tumor cells is increased, their mobility is reduced for a few a few hours after lodging in the microvessels.Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 82, No. 7, pp. 859–861, July, 1976.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号