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   99965篇
  免费   7520篇
  国内免费   4124篇
耳鼻咽喉   630篇
儿科学   3394篇
妇产科学   2416篇
基础医学   13000篇
口腔科学   2640篇
临床医学   7082篇
内科学   12366篇
皮肤病学   1196篇
神经病学   8084篇
特种医学   2261篇
外国民族医学   32篇
外科学   7389篇
综合类   12793篇
现状与发展   17篇
预防医学   6806篇
眼科学   2505篇
药学   15623篇
  25篇
中国医学   5630篇
肿瘤学   7720篇
  2024年   162篇
  2023年   1116篇
  2022年   1905篇
  2021年   3097篇
  2020年   2727篇
  2019年   2721篇
  2018年   2708篇
  2017年   3114篇
  2016年   3075篇
  2015年   3174篇
  2014年   5455篇
  2013年   7551篇
  2012年   5308篇
  2011年   6358篇
  2010年   5008篇
  2009年   5192篇
  2008年   5314篇
  2007年   5484篇
  2006年   4808篇
  2005年   4382篇
  2004年   3716篇
  2003年   3226篇
  2002年   2748篇
  2001年   2450篇
  2000年   2027篇
  1999年   1755篇
  1998年   1622篇
  1997年   1417篇
  1996年   1345篇
  1995年   1184篇
  1994年   1039篇
  1993年   942篇
  1992年   890篇
  1991年   794篇
  1990年   737篇
  1989年   670篇
  1988年   542篇
  1987年   524篇
  1986年   516篇
  1985年   730篇
  1984年   628篇
  1983年   462篇
  1982年   567篇
  1981年   438篇
  1980年   416篇
  1979年   303篇
  1978年   296篇
  1977年   228篇
  1976年   255篇
  1975年   115篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
51.

Objective

Hypertonic saline (HTS) has potent immune and vascular effects. We assessed recipient pretreatment with HTS on allograft function in a porcine model of heart transplantation and hypothesized that HTS infusion would limit endothelial and left ventricular (LV) dysfunction following transplantation.

Methods

Heart transplants were performed after 6 hours of cold ischemic storage. Recipient pigs were randomized to treatment with or without HTS (7.5% NaCl) before cardiopulmonary bypass (CPB). Using a myograft apparatus, coronary artery endothelial-dependent (Edep) and -independent (Eind) relaxation was assessed. LV performance was determined using pressure-volume loop analysis. Pulmonary interleukin (IL)-2, IL-6, and tumor necrosis factor (TNF)-α expression was measured.

Results

Weaning from CPB and LV performance after transplantation were improved in HTS-treated animals. Successful weaning from CPB was greater in the HTS-treated hearts (8 of 8 vs 2 of 8; P < .05). Mean LV functional recovery was improved in the HTS-treated animals, as assessed by preload recruitable stroke work (65 ± 10% vs 27 ± 10%; P < .001) and end-systolic elastance (55 ± 7% vs 37 ± 4%; P < .001). Treatment with HTS resulted in improved Edep (mean maximum elastance [Emax], 56 ± 5% vs 37 ± 7%; P < .001) and Eind (mean Emax%, 77 ± 6% vs 52 ± 4%; P < .001) vasorelaxation compared with control. Pulmonary expression of IL-2, IL-6, and TNF-α increased following transplantation, whereas HTS therapy attenuated IL production (P < .001). Transplantation increased plasma TNF-α levels and LV TNF-α expression, whereas HTS prevented this up-regulation (P < .001).

Conclusions

Recipient HTS pretreatment preserves allograft vasomotor and LV function, and HTS therapy limits CPB-induced injury. HTS may be a novel recipient intervention to prevent graft dysfunction.  相似文献   
52.
Context: We sought to describe our experience with the Hybrid Assistive Limb® (HAL®) for active knee extension and voluntary ambulation with remaining muscle activity in a patient with complete paraplegia after spinal cord injury.

Findings: A 30-year-old man with complete paraplegia used the HAL® for 1 month (10 sessions) using his remaining muscle activity, including hip flexor and upper limb activity. Electromyography was used to evaluate muscle activity of the gluteus maximus, tensor fascia lata, quadriceps femoris, and hamstring muscles in synchronization with the Vicon motion capture system. A HAL® session included a knee extension session with the hip flexor and voluntary gait with upper limb activity. After using the HAL® for one month, the patient’s manual muscle hip flexor scores improved from 1/5 to 2/5 for the right and from 2/5 to 3/5 for the left knee, and from 0/5 to 1/5 for the extension of both knees.

Conclusion/clinical relevance: Knee extension sessions with HAL®, and hip flexor and upper-limb-triggered HAL® ambulation seem a safe and feasible option in a patient with complete paraplegia due to spinal cord injury.  相似文献   

53.
ObjectiveObesity has reached epidemic proportions in the US. Physical activity is an important component of obesity reduction, but little is known about contemporary exercise levels among overweight/obese American adults. In this study, we compared current physical activity levels in overweight and obese US adults to those of normal weight individuals as well as ascertained which sociodemographic factors influence the meeting of physical activity recommendations in these three groups.MethodsWe used national data from 2015 and 2017 Behavioral Risk Factor Surveillance System surveys (n = 726,075). Bivariate analyses were conducted to determine unadjusted physical activity levels in normal weight, overweight, and obese adults. We fit multinomial logistic models to identify associations between sociodemographic factors and meeting physical activity recommendations in our study population.ResultsAround 45% of overweight and 57% of obese adults failed to meet physical activity guidelines compared to 41% of normal weight adults. Age, sex, and race were significantly associated with physical activity levels for both overweight and obese adults. In overweight and obese individuals, associations between sociodemographic factors and physical activity were more similar between the two comparisons of insufficiently active (IA) versus active (A)/highly active (HA) and A versus HA but quite different to those in the inactive (IN) versus IA/A/HA comparison.ConclusionsFuture physical activity interventions should be aimed at increasing the number of overweight and obese US adults who meet physical activity guidelines as well as targeted towards specific sociodemographic groups within the overweight/obese population with low exercise levels.  相似文献   
54.
《Heart rhythm》2020,17(5):842-846
  1. Download : Download high-res image (83KB)
  2. Download : Download full-size image
  相似文献   
55.
Serum eye drops (SED) have shown beneficial effects in patients suffering from dry eye syndrome and are manufactured for an increasing number of patients in Australia every year. Previous studies have examined the stability of serum growth factors during storage in either experimental vessels not used as the final packaging system or in eye drop bottles. To ensure the quality and safety of SED product manufactured in Australia, the stability of growth factors in serum packaged into two different systems during storage at different temperatures was examined. Healthy blood donors provided a whole blood donation, from which serum was prepared, diluted to 20% and dispensed into either a tube or a vial packaging system. The stability of growth factors, fibronectin and total protein in tube segments was comparable to matched vials samples during storage at −30 °C, 4 °C, 22 °C and 37 °C, with the exception of EGF and fibronectin in 20% SED stored in tube segments, which were more sensitive to storage conditions at 4 °C and 22 °C when compared to vials. Additionally, the growth factor, fibronectin and total protein concentration in both tube segments and vials was stable during storage at −30 °C for at least 9 months. This study highlights the impact of different manufacturing procedures on serum growth factor stability during storage.  相似文献   
56.
ObjectiveProvide an update of the management options for early onset scoliosis patients, including general assessment, conservative and surgical options.MethodsWe included the updated information about the assessment and management options of Early Onset Scoliosis, taking into consideration the non-fusion methods, including the burden on the patient and their family.ResultsWith the heterogeneity of this population, it is difficult to get a consensus about a unified protocol for management. Accordingly, the surgeon dealing with these cases needs to be aware of the broad range of surgical and non-surgical methods when treating these patients.ConclusionThe main aim of early onset scoliosis treatment is to gain a flexible spine associated with normal lung development and thoracic growth. Management needs to be individualized between the surgeon and patient in relation to the etiology and patient conditions.  相似文献   
57.
ObjectiveMethamphetamine is used extensively around the world as a psychostimulant. The complications related to methamphetamine include methamphetamine-induced neurotoxicity, mainly involving intraneuronal processes, such as oxidative stress and excitotoxicity. Curcumin is effective against neuronal injury due to its antioxidant, anti-inflammatory effects. In this study, we examined the protective effects of curcumin against methamphetamine neurotoxicity.MethodsSixty male Wistar rats were divided into the following groups: control (n = 12), DMSO (n = 12), methamphetamine (n = 12), and methamphetamine + curcumin (100 and 200 mg/kg, respectively, intraperitoneal [IP]; n = 12). Neurotoxicity was induced by 40 mg/kg of methamphetamine administrated through 4 injections (4 × 10 mg/kg, q2h, IP). Curcumin (100 and 200 mg/kg) was administered at 7 days after the last methamphetamine injection. By using a Morris water maze task, the hippocampus-dependent memory and spatial learning were evaluated 1 day after the last curcumin injection. Then, the animal brains were isolated for biochemical measurements, as well as glial fibrillary acidic protein (GFAP), ionized calcium-binding adaptor protein-1(Iba-1) and caspase-3 immunohistochemical staining.ResultsThe current study demonstrated that administration of curcumin significantly attenuates spatial memory impairment (P < 0.01) following methamphetamine neurotoxicity. Curcumin caused a significant increase in the levels of superoxide dismutase and glutathione peroxidase (P < 0.05). However, it decreased tumor necrosis factor (TNF-α) (P < 0.05) and malondialdehyde (P < 0.01) levels as compared to the methamphetamine group. Also, curcumin significantly reduced Iba-1 (P < 0. 01), GFAP and caspase-3 positive cells in the hippocampus (P < 0.001).ConclusionCurcumin exerted neuroprotective effects on methamphetamine neurotoxicity because of its antioxidant and anti-inflammatory effect.  相似文献   
58.
Human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS) is one of the leading causes of morbidity and mortality in West Africa. Prevalence among the most productive age group in West and Central Africa stood at 1.5%, 3.4.0%, 2.5%, and 2.1% in 1990, 2000, 2010, and 2015 respectively. This study examined the effect of HIV/AIDS on economic growth in West Africa with focus on 11 countries. The augmented Solow model, rooted in the neoclassical growth theory, was used, which was operationalized using dynamic panel data modeling approach. Incidence, prevalence, number of people living with HIV/AIDS (PLWHA), and AIDS‐related deaths were used to measure HIV/AIDS. Estimations using system GMM returned statistically significant results while those of first difference and difference GMM were not. From the outcome of system GMM analysis, a percentage increase in incidence, prevalence, PLWHA, and AIDS deaths correspondingly reduced growth significantly through their effects on life expectancy by 0.15%, 0.02%, 0.004%, and 0.03%. Acquired immune deficiency syndrome deaths and PLWHA lowered economic growth through enrolment but not significantly. The import of the findings is that HIV/AIDS threatens growth through life expectancy in West Africa. Therefore, its spread in the subregion should be effectively contained while proper treatment should be provided for all infected persons.  相似文献   
59.
60.
《中国现代医生》2020,58(31):37-39+封三
目的 探讨脂蛋白相关磷脂酶A2(Lp-PLA2)、胰岛素样生长因子-1(IGF-1)与老年血管性痴呆(VD)患者认知功能的关系及预测价值。方法 选择2019 年3~6 月在我院接受治疗的VD 患者60 例为研究对象,同时选取同期在我院接受检查的健康者60 例为对照组,比较两组患者的Lp-PLA2、IGF-1、简易智力状态检查量表评分(MMSE)水平;采用Pearson 相关性分析法对Lp-PLA2、IGF-1 与MMSE 评分的相关性进行分析;采用受试者工作曲线(ROC)下面积(AUC)比较Lp-PLA2、IGF-1 对VD 的预测价值。结果 观察组患者的Lp-PLA2 水平明显高于对照组(P<0.05),观察组患者的IGF-1、MMSE 评分明显低于对照组(P<0.05);Lp-PLA2 与MMSE 评分呈负相关性,IGF-1 与MMSE 评分呈正相关性;Lp-PLA2 与IGF-1 诊断VD 的AUC 值分别为0.940、0.954。结论Lp-PLA2 水平越低,IGF-1 水平越高,患者的认知功能越好,且Lp-PLA2、IGF-1 对老年VD 患者均具有较高的预测价值。  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