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   28503篇
  免费   2027篇
  国内免费   494篇
耳鼻咽喉   5296篇
儿科学   583篇
妇产科学   632篇
基础医学   4656篇
口腔科学   2059篇
临床医学   1632篇
内科学   2274篇
皮肤病学   680篇
神经病学   3177篇
特种医学   569篇
外科学   2708篇
综合类   1614篇
现状与发展   4篇
一般理论   2篇
预防医学   2283篇
眼科学   530篇
药学   1252篇
  10篇
中国医学   286篇
肿瘤学   777篇
  2024年   45篇
  2023年   486篇
  2022年   729篇
  2021年   1181篇
  2020年   1091篇
  2019年   1129篇
  2018年   1073篇
  2017年   1065篇
  2016年   1090篇
  2015年   1046篇
  2014年   1575篇
  2013年   2513篇
  2012年   1307篇
  2011年   1406篇
  2010年   1125篇
  2009年   1288篇
  2008年   1300篇
  2007年   1219篇
  2006年   1136篇
  2005年   942篇
  2004年   827篇
  2003年   725篇
  2002年   644篇
  2001年   561篇
  2000年   526篇
  1999年   432篇
  1998年   382篇
  1997年   377篇
  1996年   332篇
  1995年   344篇
  1994年   251篇
  1993年   233篇
  1992年   246篇
  1991年   215篇
  1990年   199篇
  1989年   181篇
  1988年   161篇
  1987年   143篇
  1986年   121篇
  1985年   223篇
  1984年   210篇
  1983年   152篇
  1982年   146篇
  1981年   102篇
  1980年   110篇
  1979年   89篇
  1978年   62篇
  1977年   66篇
  1976年   68篇
  1975年   37篇
排序方式: 共有10000条查询结果,搜索用时 687 毫秒
991.
目的:探索氨甲环酸对类风湿关节炎患者全髋关节置换围手术期失血的影响。方法回顾性分析2012年6月至2014年6月行初次全髋关节置换术患者资料,仅纳入因类风湿关节炎(Steinbrocker 3、4级)行初次单侧全髋关节置换术患者数据,最终纳入197例。其中68例术前20 min静脉滴注氨甲环酸15 mg/kg(单次给药组),74例术前20 min静脉滴注氨甲环酸15 mg/kg+术后3 h再次静脉滴注氨甲环酸10 mg/kg(重复给药组),55例未使用氨甲环酸(对照组)。单次给药组女52例、男16例,平均年龄58岁;重复给药组女54例、男20例,平均年龄59岁;对照组女40例、男15例,平均年龄55岁。比较三组患者总失血量、输血率、深静脉血栓及肺栓塞发生率、术后引流量、术后血红蛋白下降值及并发症情况。结果单次给药组、重复给药组和对照组围手术期总失血量分别为(816.80±245.09)ml、(975.15±216.33)ml和(1295.68±263.85)ml,术后引流量为(221.60±70.05)ml、(337.20±113.10)ml和(479.74±120.66)ml,输血率为5.41%、10.29%和25.45%,术后血红蛋白降低值为(2.71±0.74)g/dl、(3.18±0.62)g/dl和(3.83±0.70)g/dl;各指标给药组均较对照组低,重复给药组较单次给药组围手术期总失血量、输血率、术后引流量更低。术后三组患者均未发生深静脉血栓及肺栓塞;单次给药组8例、重复给药组6例、对照组8例出现切口并发症,发生率分别为11.8%(8/68)、8.1%(6/74)、14.5%(8/55),三者比较差异无统计学意义(χ2=1.355,P=0.508)。结论静脉使用氨甲环酸可有效降低类风湿关节炎患者全髋关节置换围手术期总失血量与输血率,且不增加血栓事件的风险,相对于术前单次使用氨甲环酸,更推荐术前及术后3h重复给药。  相似文献   
992.
Poor renal function is associated with increased rates of bone loss and osteoporotic fractures in Caucasian men. The importance of kidney function for skeletal health in African ancestry men, who are a population segment with a high prevalence of chronic kidney disease as well as high peak bone mass, is not well known. We examined the relationship between estimated glomerular filtration rate (eGFR) and rates of bone loss in a large population cohort of otherwise healthy Afro‐Caribbean men aged 40 years and older. Dual X‐ray absorptiometry of the proximal femur and quantitative computed tomography of the proximal radius and tibia were obtained approximately 6 years apart. We calculated eGFR from serum creatinine that was measured in fasting samples in 1451 men. Impaired kidney function (IKF, eGFR<60 ml/min/1.7 m2) was observed in 8.6% of the cohort. The relationship between IKF and baseline BMD and annualized rate of change in BMD was analyzed controlling for potentially important confounders. IKF was not associated with baseline BMD. In contrast, men with IKF experienced a rate of decline in areal BMD at the total hip, femoral neck and trochanter and cortical volumetric BMD compared to those with normal kidney function (p<0.05 for all). Impaired kidney function was not associated with changes in trabecular volumetric BMD. In conclusion, poorer kidney function is associated with accelerated bone loss among otherwise healthy Afro‐Caribbean men even after controlling for age and other important medical and lifestyle related variables. © 2015 American Society for Bone and Mineral Research.  相似文献   
993.
994.
The bipolar radiofrequency device (Habib®) has been recently introduced in order to reduce intraoperative bleeding for a safe hepatic resection as an alternative to the conventional tools. However, indications, perioperative findings, and outcome of the device for hepatic resections remain and deserve to be analyzed. The current study aims to analyze the feasibility of the bipolar radiofrequency device (Habib®) for hepatic resections. Information of the patients that underwent hepatic resection using with the Habib® device between 2007 and 2011 was abstracted. Patient, disease, and operation-related findings and perioperative data were investigated. A total of 71 cases (38 [53.5 %] males, mean age was 56.8 ± 11.9) were analyzed. Metastatic disease (n = 55; 77.5 %) was the leading indication followed by primary liver and biliary malignancies (n = 7; 9.9 %), hemangioma (n = 5; 7 %), hydatid disease (n = 3; 2.8 %), and hepatic gunshot trauma (n = 1; 1.4 %). Metastasectomy was the most commonly performed procedure (n = 31; 56.3 %), but in 24 (77.4 %) cases, it was performed in addition to extended resections. Other procedures in the study patients include segmentectomy in 17, bisegmentectomy in 19, trisegmentectomy in 17, right or left hepatectomy in 8, and extended right/left hepatectomy in 3. The mean (±SD) operation time was 241.7 ± 78.2 min. The median amount of bleeding was 300 cc (range 25–2500), and 23 (32.4 %) cases required perioperative transfusion. The median hospitalization period was 5 days (range 1–47). Lengthened drainage (n = 9, 12.7 %) and intraabdominal abscess (n = 8, 11.23 %) were the most common problems. Hepatic resections using the Habib® device seem to be feasible in cases with primary and metastatic hepatic lesions and benign liver masses and even those with hepatic trauma. It may lessen the amount of intraoperative hemorrhage, although lengthened drainage and intraabdominal abscess were the major postoperative problems in these cases.  相似文献   
995.
This case presents the challenges of the surgical management for a patient with a history of recurrent posterior shoulder instability and subsequently traumatic anterior dislocation. The patient was already on the waiting list for an arthroscopic posterior stabilization with anchors, when a car accident caused an additional anterior shoulder dislocation. This traumatic anterior dislocation created a bone loss with a glenoid fracture and aggravated the preexisting posterior instability. In order to address both problems, we decided to perform an arthroscopically assisted Latarjet procedure for anterior instability and to stabilize with a bone graft for posterior instability. To our best knowledge, this type of surgical procedure has so far never been reported in the literature. The purpose of this report is to present the surgical technique and to outline the decision making process.  相似文献   
996.
目的 :比较股骨颈骨折全髋置换术后放置真空负压引流瓶,不同负压下术后失血量的差异。方法 :选取2013年1月1日至2013年12月30日采用生物型全髋关节置换术治疗的74例股骨颈骨折患者,分成高负压引流组和低负压引流组。高负压引流组34例,男10例,女24例;平均年龄(75.94±9.02)岁;术毕放置60 k Pa负压真空负压引流瓶。低负压引流组40例,男13例,女27例;平均年龄(74.93±8.90)岁;术毕放置30 k Pa负压真空负压引流瓶。对术后伤口引流量、血红蛋白改变值、根据身高体重和手术前后红细胞压积(Hct)计算的所有患者总失血量等进行观察,并做统计学分析进行比较。结果:两组患者术后切口均Ⅰ期愈合,无感染发生。术后第1天,高负压引流组血红蛋白改变值为(41.74±15.69)g/L,总失血量(1 217.73±459.50)ml,术后引流量(312.94±103.44)ml;低负压引流组血红蛋白改变值(34.90±12.90)g/L,总失血量(904.01±381.58)ml,术后引流量(129.25±44.25)ml,高负压引流组的数值均高于低负压引流组。术后3 d,高负压引流组血红蛋白改变值为(46.00±13.29)g/L,总失血量(1 304.72±421.75)ml;低负压引流组血红蛋白改变值为(43.87±11.39)g/L,总失血量(1 196.78±344.20)ml,两组差异无统计学意义。结论:股骨颈骨折生物型全髋关节置换术后放置引流时,根据患者术前血红蛋白、红细胞压积等情况选择负压引流压力大小,老年性股骨颈骨折选择低负压引流更为合适。  相似文献   
997.
The cochlea of our auditory system is an intricate structure deeply embedded in the temporal bone. Compared with other sensory organs such as the eye, the cochlea has remained poorly accessible for investigation, for example, by imaging. This limitation also concerns the further development of technology for restoring hearing in the case of cochlear dysfunction, which requires quantitative information on spatial dimensions and the sensorineural status of the cochlea. Here, we employed X-ray phase-contrast tomography and light-sheet fluorescence microscopy and their combination for multiscale and multimodal imaging of cochlear morphology in species that serve as established animal models for auditory research. We provide a systematic reference for morphological parameters relevant for cochlear implant development for rodent and nonhuman primate models. We simulate the spread of light from the emitters of the optical implants within the reconstructed nonhuman primate cochlea, which indicates a spatially narrow optogenetic excitation of spiral ganglion neurons.

In the case of profound sensorineural hearing impairment, cochlear implants (CIs) partially restore hearing by providing auditory information to the brain via electrical stimulation of the spiral ganglion neurons (SGNs). CIs enable speech understanding in the majority of the ∼700,000 users worldwide. However, current clinical CIs are limited by their wide current spread (1) resulting in poor coding of spectral information (2). Recently, cochlear optogenetics was proposed for stimulating the auditory nerve by light (310). As light can be better confined in space, the spread of excitation in the cochlea is lower (3, 911) and, hence, future optical CIs (oCIs) promise improved speech comprehension—especially in noisy background—as well as greater music appreciation.For the technical development of oCIs toward a future medical device, major efforts are currently being undertaken to devise multichannel optical stimulators for the cochlea (10, 1217). As is the case for the electrodes of current CIs, future oCIs will place multiple stimulation channels, here microscale emitters, along the tonotopic axis of the cochlea. Further development of the oCIs requires precise estimates of parameters such as scala tympani size, optimal probe stiffness, and bending radius. Moreover, cochlear optogenetics employs gene transfer to the SGNs for which adeno-associated viruses (AAVs) seem promising candidate vectors (35, 8). AAV delivery has used injection of virus suspension via the round window (4, 8) or directly into Rosenthal’s canal (5, 9, 10). Therefore, the volumes of Rosenthal’s canal and the scalae tympani, vestibuli and media needed to be evaluated in order to estimate the required virus load for injection. Finally, the sensorineural status of the cochlea is highly relevant for future gene therapy and CI stimulation, and hence, quantitative imaging of sensory cells and neurons is an important objective.Here, we employed multiscale X-ray phase-contrast tomography (XPCT) and light-sheet fluorescence microscopy (LSFM) and provide an analysis of cochlear morphology for mice, rats, gerbils, guinea pigs, and marmosets. Each of these animal models offers unique advantages for auditory research. The mouse is readily available for genetic manipulation (e.g., ref. 18). Channelrhodopsin-expressing transgenic lines are available also for rats (19, 20) that offer a larger cochlea and can carry heavier implants than mice (2124). Similarly, gerbils and guinea pigs are established rodent models for auditory research with larger-sized cochleae. Moreover, gerbils, which have low-frequency hearing more similar to humans, have already been employed for cochlear optogenetics (5, 9, 10, 24). Finally, we analyzed the cochlea of the common marmoset, as an established nonhuman primate model for auditory research (e.g., refs. 25, 26). Marmosets possess a rich vocalization repertoire and share a pitch perception mechanism with humans (27). Therefore, we compared cochlear insertion of newly designed oCIs with electrical cochlear implants (eCI) and modeled the optical spread of excitation in the marmoset cochlea.  相似文献   
998.
Background & Aims: Inactivation of the CDKN2/p16INK4A tumor-suppressor gene is one of the most frequent genetic alterations in human malignancies. In esophageal adenocarcinomas, mutations of the p16 gene or homozygous deletions of the gene locus 9p21 are rare. This study investigated whether p16 promoter hypermethylation is an alternative mechanism for p16 gene inactivation during neoplastic progression in Barrett's esophagus. Methods: A methylation-specific polymerase chain reaction protocol was applied. A total of 95 specimens from 14 patients with Barrett's esophagus were analyzed longitudinally. The p16 promoter status was compared with histomorphological findings. Results: p16 promoter hypermethylation was detected in 9 of the 10 patients who had displayed dysplasia at some time during surveillance, whereas none of the patients who had not displayed dysplasia during surveillance had p16 promoter hypermethylation. p16 promoter hypermethylation was detected in 3% (2 of 67) of the samples without dysplasia, 60% (3 of 5) of the samples with lesions indefinite for dysplasia, 55.6% (10 of 18) of the specimens with low-grade dysplasia, and 75% (3 of 4) of the specimens with high-grade dysplasia. Conclusions: These data suggest that p16 promoter hypermethylation is a common mechanism of p16 gene inactivation during neoplastic progression in Barrett's esophagus.GASTROENTEROLOGY 1998;115:1381-1386  相似文献   
999.
A 15‐year‐old girl presented with acute bilateral loss of central visual acuity due to hypertensive retinopathy level IV. She was found to have unrecognized malignant arterial hypertension associated with end‐stage renal failure. At the time of diagnosis she also had severe left ventricular hypertrophy (LVH). Hypertension was successfully treated with combined anti‐hypertensive therapy, but renal function did not recover. The patient underwent successful kidney transplant 4 months later and over a period of 20 months hypertensive retinopathy and LVH gradually resolved. This report emphasizes the importance of routine measurement of blood pressure and describes the possible consequences of unrecognized arterial hypertension in children. Early diagnosis and appropriate treatment are necessary to avoid development and progression of target organ damage and promote better long‐term cardiovascular prognosis.  相似文献   
1000.
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