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   9067篇
  免费   499篇
  国内免费   151篇
耳鼻咽喉   128篇
儿科学   179篇
妇产科学   88篇
基础医学   1468篇
口腔科学   159篇
临床医学   766篇
内科学   1936篇
皮肤病学   487篇
神经病学   636篇
特种医学   683篇
外科学   1057篇
综合类   34篇
现状与发展   1篇
一般理论   1篇
预防医学   322篇
眼科学   197篇
药学   887篇
中国医学   143篇
肿瘤学   545篇
  2024年   7篇
  2023年   75篇
  2022年   242篇
  2021年   344篇
  2020年   181篇
  2019年   234篇
  2018年   293篇
  2017年   239篇
  2016年   326篇
  2015年   409篇
  2014年   526篇
  2013年   493篇
  2012年   795篇
  2011年   781篇
  2010年   420篇
  2009年   398篇
  2008年   506篇
  2007年   455篇
  2006年   353篇
  2005年   386篇
  2004年   270篇
  2003年   230篇
  2002年   233篇
  2001年   183篇
  2000年   190篇
  1999年   142篇
  1998年   99篇
  1997年   71篇
  1996年   73篇
  1995年   44篇
  1994年   55篇
  1993年   49篇
  1992年   48篇
  1991年   57篇
  1990年   45篇
  1989年   75篇
  1988年   47篇
  1987年   52篇
  1986年   37篇
  1985年   41篇
  1984年   24篇
  1983年   21篇
  1982年   18篇
  1981年   25篇
  1980年   32篇
  1979年   17篇
  1978年   15篇
  1977年   16篇
  1976年   10篇
  1975年   5篇
排序方式: 共有9717条查询结果,搜索用时 16 毫秒
991.
Objectives:To evaluate quantitatively the relationship between molar intrusion (change [Δ] maxillary first molar [U6]–palatal plane [PP]) and changes in vertical and sagittal cephalometric parameters and to determine the center of mandibular autorotation.Materials and Methods:Twenty-one patients diagnosed with anterior open bite and successfully treated with molar intrusion (overbite [OB] > 0 mm) were retrospectively enrolled. Lateral cephalograms taken before and after molar intrusion were used to measure changes in vertical and sagittal cephalometric parameters. The center of mandibular autorotation was calculated by measuring displacement of gonion (Go) and pogonion (Pog). Paired t-tests were used to compare variables, and linear regression analysis was used to examine the relationship between ΔU6-PP and other variables.Results:The mandible exhibited counterclockwise rotation after maxillary molar intrusion, which led to closure of anterior open bite. Strong linear relationships, in descending order, between ΔU6-PP and ΔOB, Δanterior facial height (AFH), Δvertical reference plane (Pog), and Δsella-nasion to Go-menton (SN-GoMe), were observed. When the maxillary molar was intruded 1 mm, OB increased by 2.6 mm, AFH decreased by 1.7 mm, Pog moved forward by 2.3 mm, and SN-GoMe decreased by 2°. The center of mandibular autorotation was located 7.4 mm behind and 16.9 mm below condylion after molar intrusion.Conclusions:The mandible exhibited counterclockwise rotation after maxillary molar intrusion; the center of mandibular autorotation was located behind and below condylion with individual variations.  相似文献   
992.
993.
UMZUG DER EMA     
  相似文献   
994.
Our aim was to identify the positional changes of the inferior alveolar neurovascular bundle and evaluate the relocation of the displaced mandibular canal after enucleation of a cyst. Seventy patients (72 sites) who had had cysts enucleated were divided into three groups based on the degree of encroachment of the cystic lesion into the mandibular canal and whether a bone graft had been inserted after the cyst had been enucleated. The mean (range) of patients’ ages was 45 (18–75) years, and there were 29 male and 41 female patients. Group A comprised cysts with encroachment on the mandibular canal that were enucleated without a bone graft; Group B consisted of cysts with no encroachment of the mandibular canal, but were enucleated without a bone graft; and Group C comprised cysts with encroachment of the mandibular canal that were enucleated with a bone graft. The displacement of the mandibular canal was identified from analysis of computed tomographic (CT) images. Changes in the position of the mandibular canal were measured on panoramic radiographs. The mandibular canal was repositioned superiorly by a mean (SD) of 2.4 (1.65) mm after enucleation of the cyst, which was significant in Group A (p < 0.001), but not in Groups B and C. These results indicate that the displaced inferior alveolar neurovascular bundles that were not surrounded by bony canal tended to relocate towards a supposedly normal position, and after enucleation of the cyst the mandibular canal was remodelled in this new location. This tendency to relocate was blocked by bone grafting. Bone grafts are therefore recommended in cases where enough bony height is required for future insertion of implants.  相似文献   
995.
BACKGROUND: The commercially available formulation of amlodipine is conjugated with besylate salt to increase water solubility. Recently, a new amlodipine salt formulation has been developed in which the free base of amlodipine is conjugated with a chemically different salt, adipate. OBJECTIVE: The goal of this study was to compare the antihypertensive effect and tolerability of amlodipine adipate with those of amlodipine besylate in patients with mild to moderate hypertension. METHODS: This was a multicenter, randomized, doubleblind, parallel-group study in which patients received 8 weeks of treatment with either amlodipine adipate or amlodipine besylate. The primary efficacy variable was noninferiority of the difference in mean changes from baseline in trough diastolic blood pressure (DBP) after 8 weeks of treatment. Secondary efficacy variables included mean changes in DBP, systolic blood pressure (SBP), and response rate (defined as the proportion of patients whose DBP was <90 mm Hg or whose DBP had decreased from baseline by > or =10 mm Hg). The incidence of adverse events (AEs) was also assessed. RESULTS: Two hundred eleven patients were randomly assigned to receive amlodipine adipate (n = 106) or amlodipine besylate (n = 105). Study patients were primarily female (54.5%), with a mean (SD) age of 52.2 (9.6) years and a mean body weight of 67.1 (10.2) kg; there were no between-group differences in demographic profiles. After 4 weeks of randomized treatment, 58 (27.5%) patients (29 [27.4%] amlodipine adipate, 29 [27.6%] amlodipine besylate) had not achieved a mean DBP <90 mm Hg, and their dose was doubled. Mean DBP changes at 8 weeks were -15.2 (7.3) mm Hg in the amlodipine adipate group and -14.2 (7.4) mm Hg in the amlodipine besylate group (P = NS). Because the 95% CI for the difference in mean DBP changes between groups (-0.53 to 2.55) was within the prespecified lower limit (-4 mm Hg), amlodipine adipate was considered noninferior to amlodipine besylate. Mean SBP changes were -24.9 (12.1) mm Hg in the amlodipine adipate group and -22.0 (14.7) mm Hg in the amlodipine besylate group (P = NS). The response rates were 92.0% for amlodipine adipate and 95.4% for amlodipine besylate (P = NS). The overall incidence of clinical AEs was 20.8% in the amlodipine adipate group and 25.7% in the amlodipine besylate group (P = NS). Drug-related clinical AEs occurred in 5.7% and 12.4% of patients in the respective treatment groups (P = NS). Serum uric acid levels decreased significantly from base-line in both groups (P < 0.001). CONCLUSIONS: Eight weeks of treatment with amlodipine adipate produced significant reductions from baseline in blood pressure in these patients with mild to moderate hypertension. The efficacy of amlodipine adipate was not inferior to that of amlodipine besylate. Tolerability was comparable between the 2 treatment groups.  相似文献   
996.
A self-assembled nanoparticle was prepared using a hydrophobically modified glycol chitosan for gene delivery. A primary amine of glycol chitosan was modified with 5beta-cholanic acid to prepare a hydrophobically modified glycol chitosan (HGC). The modified chitosan spontaneously formed DNA nanoparticles by a hydrophobic interaction between HGC and hydrophobized DNA. As the HGC content increased, the encapsulation efficiencies of DNA increased while the size of HGC nanoparticles decreased. Upon increasing HGC contents, HGC nanoparticle became less cytotoxic. The increased HGC contents also facilitated endocytic uptakes of HGC nanoparticles by COS-1 cells, which were confirmed by a confocal microscopy. The HGC nanoparticles showed increasing in vitro transfection efficiencies in the presence serum. In vivo results also showed that the HGC nanoparticles had superior transfection efficiencies to naked DNA and a commercialized transfection agent. The HGC nanoparticles composed of hydrophobized DNA and hydrophobically modified glycol chitosan played a significant role in enhancing transfection efficiencies in vitro as well as in vivo.  相似文献   
997.
PURPOSE: To examine whether significant alterations in serum sodium, potassium, and glucose levels occurred after nasogastric tube feeding with iso-osmolar formula in acute brain infarction patients. DESIGN AND METHODS: Serum sodium, potassium, and glucose levels were analyzed by a retrospective medical record review of 85 nasogastric tube-fed patients. FINDINGS: The mean values of serum sodium and potassium levels on the day before, and 1st, 2nd, and 3rd days of nasogastric feeding were within the normal range. Alterations in the incidence rates of high, normal, and low level of serum sodium and potassium after tube feeding were not statistically significant. The mean blood glucose levels on the day before, and 1st, 2nd, and 3rd days of tube feeding were above normal, and the increase after tube feading was not statistically significant. CONCLUSIONS: Enteral tube feeding using iso-osmolar formula did not significantly alter serum sodium and potassium balance. However, most participants were hyperglycemic before and after tube feeding, indicating that hyperglycemia can be induced in the acute stages of brain infarction regardless of tube feeding.  相似文献   
998.
In infants with febrile urinary tract infection (UTI), the accurate rapid diagnosis of acute pyelonephritis (APN) would be valuable because early aggressive treatment reduces the risk of renal scarring. The objective of the study was to evaluate whether rapid plasma neutrophil gelatinase-associated lipocalin (NGAL) assay could be used as a diagnostic biomarker of renal parenchymal injury in infants with acute febrile UTI to distinguish APN at the bedside. This prospective observational study included 47 infants, who were admitted with a first episode of acute febrile UTI. Total UTI group was divided into the Cortical defect (UTI-CD, n?=?24) group and Non-cortical defect (UTI-ND, n?=?23) group, according to the result of renal scan. For the Control group, 15 infants who presented a febrile episode without any focus of bacterial infection were included. On admission, the median NGAL level (106.5 [60–476]?ng/mL) in the UTI-CD group was significantly higher than that (60 [60–196]?ng/mL) in the UTI-ND group and that (60 [60–197]?ng/mL) in the Control group and was significantly decreased to 60 [60–306]?ng/mL after an antibiotic treatment. The area under the receiver operating characteristic curves was 0.748 (95 % CI, 0.610–0.887; P?=?0.003) for NGAL levels and 0.724 (95 % CI, 0.579–0.868; P?=?0.009) for CRP levels. The best cutoff of NGAL level for detection of APN was founded to be 61.0 ng/mL (sensitivity, 75.0 %; specificity, 78.3 %). Although not a stand-alone test, the rapid determination of plasma NGAL level provides valuable information quickly, concerning the distinction of APN, for determining the clinical course of acute febrile UTI.  相似文献   
999.
Escolar  G; Leistikow  E; White  JG 《Blood》1989,74(6):1983-1988
We have examined the movement of fibrinogen-gold (fgn-Au) complexes in platelets activated in suspension and by surface contact. Fgn-Au probes did not react with resting cells but were bound to the external membrane of platelets in suspension 5 seconds after addition of 1 U/mL of thrombin. At intervals over a period of 5 to 20 minutes, fgn-Au probes moved from the cell surface to peripheral and then deep channels of the open canalicular system (OCS). When platelets were surface activated by exposure to carbon-stabilized, formvar-coated grids for 5 to 20 minutes and then exposed to fgn-Au complexes for 5 minutes, probes were also observed in the OCS. At 5 minutes, over 40% of the platelets had concentrated fgn-Au in their OCS. Results after 10 minutes revealed 25% with gold-filled channels, 16% after 15 minutes, and 5% after 20 minutes. The decrease in frequency of OCS staining correlated with the increasing frequency of spread platelets, suggesting that tension produced by spreading may cause collapse of the OCS or that the OCS may evaginate onto the platelet during spreading. To evaluate the latter hypothesis, platelets were initially exposed to grids for 5 minutes and then incubated with fgn-Au for intervals of 5 to 20 minutes. The frequency of platelets with fgn-Au concentrated in the OCS was greatest at 5 minutes (44%) and decreased at the same rate as the frequency of spread platelets increased. Only 14.7% of the cells contained fgn-Au in the OCS after 20 minutes. These were primarily dendritic in form, while fully spread platelets rarely contained an OCS filled with the probe. The study indicates that fgn-Au particles are cleared to channels of the OCS independent of the mechanism of platelet activation. Fgn-Au that has been concentrated in the OCS at early stages of surface activation can be externalized during platelet spreading but remain internalized in suspension-activated cells. The OCS represents a membrane reservoir that can be evaginated onto the platelet surface during interaction with surfaces.  相似文献   
1000.

Background  

Few studies have described patients with foregut dysmotility in inflammatory bowel disease. The aim of this case series was to evaluate clinical characteristics of 5 patients with inflammatory bowel disease and symptoms and signs of upper gut dysmotility.  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