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   659篇
  免费   35篇
耳鼻咽喉   2篇
儿科学   38篇
妇产科学   16篇
基础医学   81篇
口腔科学   3篇
临床医学   44篇
内科学   129篇
皮肤病学   5篇
神经病学   55篇
特种医学   16篇
外科学   109篇
综合类   28篇
一般理论   4篇
预防医学   52篇
眼科学   10篇
药学   37篇
中国医学   3篇
肿瘤学   62篇
  2024年   2篇
  2023年   7篇
  2022年   25篇
  2021年   15篇
  2020年   8篇
  2019年   11篇
  2018年   20篇
  2017年   6篇
  2016年   13篇
  2015年   22篇
  2014年   22篇
  2013年   26篇
  2012年   54篇
  2011年   44篇
  2010年   20篇
  2009年   22篇
  2008年   34篇
  2007年   44篇
  2006年   27篇
  2005年   37篇
  2004年   31篇
  2003年   38篇
  2002年   19篇
  2001年   15篇
  2000年   7篇
  1999年   7篇
  1998年   7篇
  1997年   7篇
  1996年   2篇
  1995年   4篇
  1994年   3篇
  1993年   7篇
  1992年   5篇
  1990年   8篇
  1989年   3篇
  1987年   5篇
  1986年   3篇
  1985年   8篇
  1984年   3篇
  1983年   2篇
  1982年   3篇
  1981年   5篇
  1979年   6篇
  1977年   3篇
  1976年   7篇
  1975年   6篇
  1974年   2篇
  1972年   5篇
  1971年   2篇
  1968年   2篇
排序方式: 共有694条查询结果,搜索用时 0 毫秒
681.
A series of quinoline-incorporated substituted thiadiazole were designed and synthesized using appropriate synthetic route keeping in view the structural requirement of pharmacophore and evaluated for anticonvulsant and CNS activities. After intraperitoneal injection to mice, some synthesized derivatives were examined in the maximal electroshock seizure (MES) and subcutaneous pentylenetetrazol (scPTZ)-induced seizure and neurotoxicity screens. Those found potent were also evaluated for behavioural impairment and depression activity. Among the compounds tested, 6d and 6e showed protection from seizures in both the animal models at dose level of 30 mg/kg while 7f showed protection against both models at 100 mg/kg dose level. These compounds exhibited lesser CNS depression and neurotoxicity compared with clinically effective drug.  相似文献   
682.
We have found in vitro that a biofilm of benign Escherichia coli 83972 interferes with urinary catheter colonization by pathogens, and in human studies E. coli 83972-coated urinary catheters are associated with lower rates of catheter-associated urinary tract infections. We hypothesized that modifying surfaces to present mannose ligands for the type 1 fimbriae of E. coli would promote formation of dense E. coli 83972 biofilms, thereby interfering with surface colonization by Enterococcus faecalis, a common uropathogen. We covalently immobilized mannose on silicon substrates by attaching amino-terminated mannose derivative to carboxylic acid-terminated monolayers via amidation. Fluorescence microscopy showed that E. coli 83972 adherence to mannose-modified surfaces increased 4.4-fold compared to unmodified silicon surfaces. Pre-exposing mannose-modified surfaces to E. coli 83972 established a protective biofilm that reduced E. faecalis adherence by 83-fold. Mannose-fimbrial interactions were essential for the improved E. coli 83927 adherence and interference effects. From the Clinical Editor: Recurrent urinary tract infections remain major adverse events associated with catheter use. The authors report that modifying catheter surface to present mannose ligands for the type 1 fimbriae of benign Escherichia coli 83972 promotes formation of dense E. coli biofilms, which 100-fold reduces urinary catheter colonization of uropathogens. Future application of this technology is expected to result in substantial UTI risk reduction in catheter users.  相似文献   
683.
We aimed to determine whether our targeting method for the subthalamic nucleus (STN) in Parkinson's disease informs the initial programming sequence. We evaluated 100 STN-lead pairs from 50 patients who underwent bilateral STN-deep brain stimulation operations. All patients had at least one year of follow-up. In each patient, we measured coordinates of the STN borders and determined the center from special T2-weighted MRI. We then measured the postoperative location of the lead tip by MRI registered to preoperative images. Finally, we determined the mode and active contact(s). Programming was monopolar 71% of the time. A total of 52% of left and 72% of right STN active contacts were located posterolateral to the STN center. In z, only 14% of the active contact(s) were >1mm below the STN center. Contacts 1 or 2 were active 90% of the time. The consistent location of active contacts suggests that initial programming began with contact 1 or 2.  相似文献   
684.
We report a method for deep brain stimulation (DBS) lead fixation in the event that the primary anchoring device fails to function effectively. The method involves the application of a titanium microplate to secure the lead to the skull, thereby providing a fast and reliable “rescue” mechanism for lead fixation. This method can supplement any burr hole cap and fixation method. Furthermore, this method has several advantages over removal and replacement of the primary anchor, such as a lower possibility of lead migration, faster procedural time, and cost-effectiveness.  相似文献   
685.
686.
Objective: The aim of the study was to analyze treatments and outcome in depressed patients. Method: Patients with recurrent depressive disorder (n = 289), recruited for a prophylaxis study, were followed up in hospital settings for 6 months with diagnostic and depression ratings at baseline and monthly depression ratings. Data on psychotropic drugs were retrieved from hospital case records. Independent associations between baseline, treatment and outcome variables were examined by logistic regression models. Results: Depressive symptoms subsided gradually. After 6 months, 21% had dropped out, 43% were rated as remitted (HAM‐D‐17 <8) and 8% had not responded (HAM‐D‐17 >15). Patients once remitted rarely relapsed (<5%). All patients received antidepressant drugs, half of them more than one (2–4) as well as other psychotropic drugs. Patients responding poorly received more frequently multiple antidepressants, tricyclic antidepressants, hypnosedatives, lithium and/or antipsychotics. Conclusion: The 6‐month outcome was generally poor. Choice of treatment appeared at least partly to be determined by the therapeutic outcome.  相似文献   
687.
Bee's wax produced by honeybees is rich in polyphenols. As the polyphenols are thought to protect cell constituents against oxidative damage through scavenging of free radicals, the present work was undertaken to evaluate the effects of polyphenols extracted from bees wax on the oxidative stress induced by carbon tetrachloride (CCl4) in rats. The polyphenols extracted by 80% methanol from bee wax (PBW) were fed to Wistar rats at 100 mg/kg body weight and 200 mg/kg body weight for 14 days in order to study its antioxidative and antihepatotoxic effects against CCl4 (1.5 ml/kg body weight)-induced stress. On 15th day all the rats were sacrificed, blood was collected for serum and organs/tissues were excised for biochemical analysis. The results showed a significant decrease in hepatic antioxidant enzyme activities viz. catalase, glucose-6-phosphate dehydrogenase (G-6-PDH), glutathione peroxidase (GSH-Px), glutathione reductase, superoxide dismutase (SOD) and a significant increase in glutathione S-transferase (GST) and gamma-glutamyl transpeptidase (GGT) by CCl4, probably due to the peroxidative effects. The prophylactic use of PBW at 200 mg/kg level resulted in a significant increase in CCl4-induced reduction in catalase, G-6-PDH, GSSGR and SOD. The hepatic levels of lipid peroxides viz. malondialdehyde, conjugated dienes and lipid hydroperoxides, enhanced by the administration of CCl4 were brought down by the ingestion of PBW at a level of 200 mg/kg. The hepatotoxicity caused by the administration of CCl4 was reduced significantly. Hence, it is concluded that the polyphenols from bees wax exhibit hepatoprotective and antioxidative properties in  相似文献   
688.
Aim: To investigate risk factors of adverse outcome in a cohort of very preterm children treated mainly with nasal continuous positive airway pressure (CPAP) during the neonatal course. Methods: In Denmark, preterm children are treated with nasal CPAP as a first approach to respiratory support. A national prospective study of all infants with a birthweight below 1000 g or a gestational age below 28 wk born in 1994-1995 was initiated to evaluate this approach. Of the 269 surviving children 164 (61%) were not treated with mechanical ventilation in the neonatal period. A follow-up of the children at 5 y of age was conducted. Data from the neonatal period and the 5-y follow-up were analysed. Results: In multivariate analyses including 250 children, a severely abnormal neonatal brain ultrasound scan was predictive of cerebral palsy (OR = 19.9, CI 95%: 6.1-64.8) and intellectual disability (OR = 6.2, CI 95%: 2.3-16.5). A high Clinical Risk Index for Babies (CRIB) score (OR = 2.4, CI 95%: 1.1-5.5) and chronic lung disease (OR = 2.8, CI 95%: 1.2-6.9) were predictive of intellectual disability. In univariate analyses mechanical ventilation was associated with cerebral palsy (OR = 4.3, CI 95%: 1.7-10.8) and intellectual disability (OR = 2.2, CI 95%: 1.2-4.2), but the associations became insignificant in multivariate analyses including chronic lung disease and a severely abnormal ultrasound scan.

Conclusion: The associations between neonatal risk factors and adverse outcome in our cohort were very similar to those found in other cohorts with another initial treatment of respiratory insufficiency. We found no significant adverse effects of mechanical ventilation beyond what could be explained by associations with chronic lung disease and IVH 3-4/PVL.  相似文献   
689.
Transcranial magnetic stimulation (TMS) of the motor cortex excites limb muscles of the contralateral side of the body. Reports of poorly defined, or a complete lack of systematic excitatory responses of soleus motoneurons compared with those of tibialis anterior (TA) motoneurons has led to the proposal that while all ankle flexor motoneurons receive strong corticomotoneuronal connections, very few soleus motoneurons do. In addition, the connections to these few motoneurons are weak. The nature of corticomotoneuronal connections onto these two motoneuron pools was re-evaluated in the following experiments. The leg area of the left motor cortex was stimulated with a large double-cone coil using Magstim 200, while surface electromyographic (EMG) and single motor unit (SMU) responses were recorded from soleus and TA muscles of healthy adult subjects. Under resting conditions, the onset (25-30 ms) and duration of concomitantly recorded short latency motor evoked potentials (MEPs) in surface EMG from both muscles were similar. The input-output relationships of the simultaneously recorded soleus and TA EMG responses showed much greater increases in TA MEPs compared with soleus MEPs with identical increases in stimulus intensity. Under resting and nonisometric conditions, a later peak with onset latency of approximately 100 ms was observed in soleus. During isometric conditions or with vibration of the TA tendon, the second soleus peak was abolished indicating reflex origin of this peak. Recordings from 42 soleus and 39 TA motor units showed clear response peaks in the peristimulus time histograms (PSTHs) of every unit. Two statistical tests were done to determine the onset and duration of response peaks in the PSTHs. With chi(2) test, the duration was 6.9 +/- 4.2 ms (mean +/- SD) for soleus and 5.1 +/- 2.1 ms for TA. Using the criterion of discerning a peak by bin counts being three SDs above background, the duration was 10.0 +/- 4.4 ms for soleus and 7.8 +/- 2.6 ms for TA. Results of these experiments do not suggest a lack of systematic corticomotoneuronal connections on soleus motoneurons when compared with those on TA, though some differences in the strengths of corticomotoneuronal connections onto the two pools do exist.  相似文献   
690.
BACKGROUND: We have previously observed that an increasing time to pregnancy (TTP) is associated with a reduced frequency of twin deliveries in couples not receiving infertility treatment. By using updated information, we assessed the frequencies of dizygotic (DZ) and monozygotic (MZ) twin deliveries as a function of infertility (TTP > 12 months), as well as infertility treatment. METHODS: From the Danish National Birth Cohort (1997-2003), we identified 51 730 fertile couples with TTP 12 months and 5163 infertile couples who conceived after treatment. Information on zygosity, available for part of the cohort (1997-2000), was based on standardized questions on the similarities between the twins at the age of 3-5 years. RESULTS: Compared with fertile couples, the frequency of DZ twin deliveries was lower for infertile couples conceiving naturally (odds ratio 0.4, 95% confidence interval 0.2-0.7) and was much higher for infertile couples conceiving after treatment (17.3, 14.4-20.7). The frequency of DZ twin deliveries decreased with TTP in untreated couples, whereas the frequency of MZ twin deliveries remained constant. CONCLUSIONS: The frequency of DZ twin deliveries decreased with TTP and substantially increased with infertility treatment, whereas MZ twin deliveries remained substantially unchanged.  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