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   2152篇
  免费   86篇
  国内免费   6篇
耳鼻咽喉   19篇
儿科学   177篇
妇产科学   32篇
基础医学   189篇
口腔科学   70篇
临床医学   182篇
内科学   409篇
皮肤病学   18篇
神经病学   103篇
特种医学   35篇
外科学   400篇
综合类   29篇
一般理论   2篇
预防医学   97篇
眼科学   195篇
药学   192篇
中国医学   13篇
肿瘤学   82篇
  2024年   2篇
  2023年   17篇
  2022年   40篇
  2021年   111篇
  2020年   44篇
  2019年   62篇
  2018年   98篇
  2017年   51篇
  2016年   60篇
  2015年   71篇
  2014年   114篇
  2013年   133篇
  2012年   227篇
  2011年   217篇
  2010年   107篇
  2009年   117篇
  2008年   150篇
  2007年   109篇
  2006年   97篇
  2005年   115篇
  2004年   103篇
  2003年   63篇
  2002年   55篇
  2001年   22篇
  2000年   10篇
  1999年   8篇
  1998年   7篇
  1997年   4篇
  1996年   4篇
  1995年   1篇
  1994年   3篇
  1993年   6篇
  1992年   3篇
  1991年   3篇
  1990年   3篇
  1989年   2篇
  1988年   1篇
  1987年   1篇
  1986年   1篇
  1983年   1篇
  1982年   1篇
排序方式: 共有2244条查询结果,搜索用时 15 毫秒
71.
The study consisted of application of anti-ubiquitin antibodies (Abs)-coated iron oxide-nanoparticles (IONPs) for minimisation of oxidative stress to contemporary live spermatozoa from the raw semen. Round-shaped IONPs (12.09 ± 0.91 nm) after two-stage functionalisation (silanisation and pegylation) were conjugated with Abs. Four aliquots from each of the 24 ejaculates (4 buffalo bulls) formed Control (Group I) and treatment (II, III and IV) groups; each containing 150 ± 25 million dead/damaged spermatozoa. IONPs-Abs complex were added at ratio of 1:1 (0.5 µg/ml), 1:2 (1.0 µg/ml) and 1:4 (2.0 µg/ml), respectively, in Groups II, III and IV. The semen quality parameters showed improvement at lag-stage (post-nano-purification before processing for cryopreservation). The mean post-thaw motility (%) in Group IV was found to be greater (p < .05) than Group I. Moreover, the overall DNA integrity (%) at post-thaw stage was improved in the nano-purified semen samples. The value of malondialdehyde was greater (p < .001) in Group I than Groups II, III and IV. The mean total antioxidant capacity and superoxide dismutase (U/mg protein) activity values in Group IV was greater (p < .05) than Group I. The study results show that IONPs conjugated with anti-ubiquitin Abs at 2.0 µg/ml can be an effective dose for depletion of dead/damaged spermatozoa from buffalo ejaculates to minimise oxidative stress.  相似文献   
72.
73.
Influential neurocomputational models emphasize dopamine (DA) as an electrophysiological and neurochemical correlate of reinforcement learning. However, evidence of a specific causal role of DA receptors in learning has been less forthcoming, especially in humans. Here we combine, in a between-subjects design, administration of a high dose of the selective DA D2/3-receptor antagonist sulpiride with genetic analysis of the DA D2 receptor in a behavioral study of reinforcement learning in a sample of 78 healthy male volunteers. In contrast to predictions of prevailing models emphasizing DA''s pivotal role in learning via prediction errors, we found that sulpiride did not disrupt learning, but rather induced profound impairments in choice performance. The disruption was selective for stimuli indicating reward, whereas loss avoidance performance was unaffected. Effects were driven by volunteers with higher serum levels of the drug, and in those with genetically determined lower density of striatal DA D2 receptors. This is the clearest demonstration to date for a causal modulatory role of the DA D2 receptor in choice performance that might be distinct from learning. Our findings challenge current reward prediction error models of reinforcement learning, and suggest that classical animal models emphasizing a role of postsynaptic DA D2 receptors in motivational aspects of reinforcement learning may apply to humans as well.  相似文献   
74.
Mandavdhare  Harshal S.  Praveen Kumar  M.  Jha  Dayakrishna  Kumar  Antriksh  Sharma  Vishal  Desai  Pankaj  Shumkina  Lada  Gupta  Pankaj  Singh  Harjeet  Dutta  Usha 《Esophagus》2021,18(3):436-450

The traditional way to tackle Zenker’s diverticulum (ZD) has been flexible endoscopic septum division (FESD). Recently, the concept of per oral endoscopic myotomy has been found useful for managing diverticular diseases of the esophagus and has been termed DPOEM. We performed a systematic review and meta-analysis to evaluate the efficacy and safety of D-POEM in diverticular disease of the esophagus and to compare it with FESD. We systematically searched PubMed and Embase, for studies reporting clinical success, technical success and adverse events in D-POEM alone or D-POEM comparing with FESD. We computed pooled prevalence for D-POEM alone and risk ratio for D-POEM vs FESD using random effect method with inverse variance approach. Subgroup analysis for ZD, non-ZD and mixed diverticulum was conducted. Totally 19 studies including 341 patients were identified reporting on D-POEM. The pooled clinical, technical success and adverse event rates for D-POEM were 87.07%, 95.19% and 10.22%, respectively. The clinical success was significantly better than FESD while the technical success, adverse event rate, procedure time and length of hospital stay were comparable with FESD. The recurrence rate was negligible for D-POEM compared to FESD. On subgroup analysis by dividing into three groups of ZD, non-ZD and mixed, there was no difference between clinical, technical success and adverse event rate among the three groups. D-POEM is an effective and safe technique among both ZD and non-ZD patients and has better clinical success than FESD.

  相似文献   
75.
Background and aimsEver since COVID-19 was declared a pandemic by WHO in late March 2020, more and more people began to share their opinions online about the anxiety, stress, and trauma they suffered because of the pandemic. However, very few studies were conducted to analyze the general public’s perception of what causes stress, anxiety, and trauma during COVID-19. This study focuses particularly on understanding Indian citizens.MethodsBy using Machine learning techniques, particularly Natural language processing, this study focuses on understanding the attitude of Indian citizens while discussing the anxiety, stress, and trauma created because of COVID-19 and the major reasons that cause it. We used Tweets as data for this study. We have used 840,000 tweets for this study.ResultsOur sentiment analysis study revealed the interesting fact that, even while discussing about the stress, anxiety, and trauma caused by COVID-19, most of the tweets were in neutral sentiments. Death and Lockdown caused by the COVID-19 were the two most important aspects that cause stress, anxiety, and Trauma among Indian citizens.ConclusionIt is important for policymakers and health professionals to understand common citizen’s perspectives of what causes them stress, anxiety, and trauma to formulate policies and treat the patients. Our study shows that Indian citizens use social media to share their opinions about COVID-19 and as a coping mechanism in unprecedented time.  相似文献   
76.
77.

The present study evaluated phenolics and antioxidant activities in fully ripened fruits of 20 different apple cultivars e.g., Royal Delicious, Fanny, Gale Gala, Esopus Spitzenburg, King David, Winter Banana, Buckinghum, Super Chief, Breven, Red Fuji, Organ Spur, Tompking County, Red Gold, Golden Spur, Vance Delicious, Red Delicious, Macintosh, Rymer, Bhura Delicious, and Richa Red growing at different locations/elevations of Uttarakhand, West Himalaya, India. Total phenolics and tannins varied significantly among cultivars and the maximum content was recorded in Bhura Delicious (phenolics—3.77 mg GAE/g fw; tannins—16.47 mg TAE/g fw) as compared to others. Antioxidant activity using different in vitro assays showed highest activity in Bhura Delicious and lowest in Esopus Spitzenburg. A significant (p < 0.001) positive relationship was found between total phenolics and ABTS (r = 0.816), FRAP (r = 0.797) and DPPH (r = 0.862) assays. Phenolics and antioxidant activity exhibited significantly (p < 0.05) higher content in the peel as compared to whole fruit and flesh portion. Based on the results, it is concluded that Bhura Delicious is one of the promising sources of phenolics and antioxidant activity and, therefore, recommended for large scale plantation to harness its potential.

  相似文献   
78.
Endobronchial ultrasound   总被引:11,自引:0,他引:11  
Sheski FD  Mathur PN 《Chest》2008,133(1):264-270
During flexible fiberoptic bronchoscopy (FB), a solitary pulmonary nodule (SPN) is sampled by means of transbronchial needle aspiration (TBNA), brush, or transbronchial lung biopsy under fluoroscopy; and mediastinal lymph nodes are sampled using "blind" TBNA. Endobronchial ultrasound (EBUS) was developed to help visualize the lesion at the time of biopsy in order to improve the diagnostic yield. METHODS: There are two types of EBUS techniques: using a radial probe (RP) with a rotating transducer at the distal tip, which produces a 360 degrees image to the long axis of the bronchoscope; and using an EBUS bronchoscope with a linear transducer at its distal tip, producing a 50 degrees image parallel to its long axis. RESULTS: In biopsies of SPNs < 2 cm using an RP, EBUS demonstrates a higher diagnostic yield than conventional FB techniques. With mediastinal and hilar nodal stations, except for the subcarina, EBUS shows a higher yield over blind TBNA. The current procedural terminology code for EBUS is 31620, a "ZZZ" code submitted in addition to other performed procedures (31622-31638). In 2007, an estimate of physician Medicare reimbursement for EBUS is $70.49. Reimbursement is locality dependent and based on economic-exchange conversion factors. Incorporating an ultrasound image into the report substantiates the use of this technique. Limitations: The physician must learn ultrasound image interpretation and the EBUS technique, and be skilled in TBNA. Maintaining competency requires frequent performance of EBUS. CONCLUSION: EBUS-directed biopsy improves the yield over conventional FB for SPNs < 2 cm and for most mediastinal or hilar nodal stations. This reduces the need to conduct additional diagnostic procedures.  相似文献   
79.
The Asian Pacific Association for the Study of the Liver (APASL) Working Party on Portal Hypertension has developed consensus guidelines on the disease profile, diagnosis, and management of noncirrhotic portal fibrosis and idiopathic portal hypertension. The consensus statements, prepared and deliberated at length by the experts in this field, were presented at the annual meeting of the APASL at Kyoto in March 2007. This article includes the statements approved by the APASL along with brief backgrounds of various aspects of the disease.  相似文献   
80.
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