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   12185篇
  免费   858篇
  国内免费   58篇
耳鼻咽喉   149篇
儿科学   276篇
妇产科学   144篇
基础医学   1774篇
口腔科学   187篇
临床医学   1076篇
内科学   2437篇
皮肤病学   166篇
神经病学   1318篇
特种医学   528篇
外国民族医学   1篇
外科学   1947篇
综合类   110篇
一般理论   4篇
预防医学   846篇
眼科学   278篇
药学   1102篇
中国医学   44篇
肿瘤学   714篇
  2023年   71篇
  2022年   118篇
  2021年   218篇
  2020年   165篇
  2019年   228篇
  2018年   283篇
  2017年   164篇
  2016年   207篇
  2015年   265篇
  2014年   346篇
  2013年   521篇
  2012年   765篇
  2011年   829篇
  2010年   499篇
  2009年   465篇
  2008年   784篇
  2007年   828篇
  2006年   822篇
  2005年   826篇
  2004年   783篇
  2003年   699篇
  2002年   663篇
  2001年   173篇
  2000年   117篇
  1999年   164篇
  1998年   163篇
  1997年   129篇
  1996年   116篇
  1995年   101篇
  1994年   84篇
  1993年   89篇
  1992年   111篇
  1991年   96篇
  1990年   80篇
  1989年   98篇
  1988年   60篇
  1987年   60篇
  1986年   73篇
  1985年   75篇
  1984年   72篇
  1983年   72篇
  1982年   64篇
  1981年   57篇
  1980年   44篇
  1979年   38篇
  1978年   29篇
  1977年   31篇
  1975年   29篇
  1973年   35篇
  1972年   30篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
PURPOSE: To determine the probability curve for regional cerebral infarction as a function of percentage normalized perfused cerebral blood volume (pCBV) in patients with acute ischemic stroke. MATERIALS AND METHODS: The authors retrospectively analyzed whole-brain computed tomographic (CT) perfusion scans from 28 patients with acute stroke (<6 hours) due to major arterial occlusion, without intracranial hemorrhage. Each patient had a positive follow-up CT scan 1-4 days later, without interval thrombolysis. Normalized pCBV, expressed as a percentage of contralateral normal brain pCBV, was determined in the core infarction and in regions just inside and outside the boundary between infarcted and noninfarcted brain. These regions were dichotomized into infarcted (core and inner band) and noninfarcted (outer band) categories. Logistic regression analysis was then used to create a reference curve of probability of infarction as a function of percentage normalized pCBV. RESULTS: Normalized pCBV values in the core, inner band, and outer band were 24.5% +/- 2.3, 36.3% +/- 2.4, and 72.1% +/- 2.4, with corresponding probabilities of infarction of .99, .96, and .11. The normalized pCBV at which the probability of survival reached .5 was 58.0% +/- 0.5. Sensitivity, specificity, and accuracy of the reference probability curve were 90.5% (209 of 231), 89.5% (212 of 237), and 90.0% (421 of 468), respectively. Negative and positive predictive values were 90.6% (212 of 234) and 89.3% (209 of 234), respectively. R2 was 0.73, and differences in perfusion between core and inner and outer bands were highly significant (P <.0001). CONCLUSION: A probability of infarction curve can help predict the likelihood of infarction as a function of percentage normalized pCBV.  相似文献   
102.
BACKGROUND: Ipsilateral salivary gland tumors of different histologic types are rare and make up less than 0.3% of all salivary gland neoplasms. Only nine cases of synchronous benign and malignant ipsilateral parotid gland tumors have been described in the literature. METHODS: Two additional cases of synchronous benign and malignant neoplasms in the parotid gland are reported and discussed with a review of literature. RESULTS: Our first case describes a pleomorphic adenoma and a salivary duct carcinoma, an entity not previously reported in the literature. The second case documents the most common benign and malignant ipsilateral parotid gland neoplasm reported in this case series, a Warthin's tumor and a mucoepidermoid carcinoma. CONCLUSIONS: Synchronous salivary gland tumors exhibiting both benign and malignant components are uncommonly observed, with only nine cases published to date. We describe two additional cases of a synchronous benign and malignant ipsilateral parotid gland tumor.  相似文献   
103.
Toe-touch weight bearing and partial weight bearing are commonly prescribed orders. The purpose of this study is to evaluate the validity of toe-touch weight bearing and partial weight bearing regimens. Twenty-five orthopedic surgeons participated in the study. They were asked to answer a questionnaire regarding toe-touch weight bearing and partial weight bearing definitions, and were asked to bear weight partially according to the accepted definitions of each order. Weight bearing on the affected limb was measured by the SmartStep System (Andante Medical Devices, Ltd, Omer, Israel). There was a 40% success rate for toe-touch weight bearing as measured by kilograms and 58% as measured by percentage of body weight. There was a 22% success rate for partial weight bearing as measured by kilograms and 50% success rate as measured by percentage of body weight. For toe-touch weight bearing as measured by kilograms, 52% exerted a mean 15.9 kg more than the maximum. For partial weight bearing as measured by kilograms, 64% exerted too much weight with an average of 14.2 kg more than the maximum. There was a significantly higher success rate for the percentage of body weight order than the kilogram order. The partial weight bearing order with the percent body weight order had a lower mean deviation from desired performance. This study and others demonstrate the need for standardization of weight bearing orders.  相似文献   
104.
There has been a longstanding debate about the roles of surgical bypass graft, percutaneous transluminal angioplasty, subintimal angioplasty, and conservative management for femoro-popliteal occlusive disease. Subintimal angioplasty was first described in 1987 as a method of performing an endovascular arterial bypass. The subintimal space at the start of the occlusion is entered with a catheter and a wire loop is used to cross the occlusion and reenter the vessel lumen distally. In patients with critical limb ischemia, there is high quality evidence demonstrating that the limb salvage rate and amputation-free survival rates for surgery and endovascular treatment are similar, but surgery is more expensive than angioplasty in the short term. In patients with intermittent claudication, surgical bypass using an autologous saphenous vein graft is currently believed to be the gold standard, but this is increasingly questioned in the light of recent advances in endovascular techniques. Surgical bypass with vein graft offers a 2-year patency of 81%, compared with 67% for a polytetrafluoroethylene (PTFE) graft and at best 67% for subintimal angioplasty. The better patency offered by surgery must be balanced against a higher morbidity and mortality. To conclude, subintimal angioplasty is an extremely valuable technique in the management of critical limb ischemia. Based on the evidence to date, this technique is likely to have an increasing role in the management of intermittent claudication over the coming years, particularly if the risk of general anaesthesia is high or there is no suitable vein.  相似文献   
105.
Background Few Western studies have focused on percutaneous techniques using percutaneous transhepatic choledochoscopy (PTHC) and holmium:yttrium–aluminum–garnet (YAG) laser to ablate biliary calculi in patients unable or unwilling to undergo endoscopic or surgical removal of the calculi. The authors report the efficacy of the holmium:YAG laser in clearing complex biliary calculi using percutaneous access techniques. Methods This study retrospectively reviewed 13 non-Asian patients with complex secondary biliary calculi treated percutaneously using holmium:YAG laser. Percutaneous access was accomplished via left, right, or bilateral hepatic ducts and upsized for passage of a 7-Fr video choledochoscope. Lithotripsy was performed under choledochoscopic vision using a holmium:YAG laser with 200- or 365-μm fibers generating 0.6 to 1.0 joules at 8 to 15 Hz. Patients underwent treatment until stone clearance was confirmed by PTHC. Downsizing and subsequent removal of percutaneous catheters completed the treatment course. Results Seven men and six women with an average age of 69 years underwent treatment. All the patients had their biliary tract stones cleared successfully. Of the 13 patients, 3 were treated solely as outpatients. The average length of percutaneous access was 108 days. At this writing, one patient still has a catheter in place. The average number of holmium:YAG laser treatments required for stone clearance was 1.6, with no patients requiring more than 3 treatments. Of the 13 patients, 8 underwent a single holmium:YAG laser treatment to clear their calculi. Prior unsuccessful attempts at endoscopic removal of the calculi had been experienced by 7 of the 13 patients. Five patients underwent percutaneous access and subsequent stone removal as their sole therapy for biliary stones. Five patients were cleared of their calculi after percutaneous laser ablation of large stones and percutaneous basket retrieval of the remaining stone fragments. There was one complication of pain requiring admission, and no deaths. Conclusions The use of PTHC with holmium:YAG laser ablation is safe and efficacious, but requires prolonged biliary access and often multiple procedures to ensure clearance of all calculi.  相似文献   
106.
107.
Introduction We report an isolated pedigree in which a consanguineous couple had twin sons with Dandy–Walker malformation (DWM). The mother is similarly affected with the disorder.Discussion DWM is an abnormality of the central nervous system, which leads to hydrocephalus and is associated with other abnormalities.Conclusion Inheritance of the disorder remains controversial, with the majority perceived to be sporadic cases. This report suggests an autosomal inheritance.  相似文献   
108.
This study addresses the question of how stress is linked to sexual problems among women and men in close relationships. Psychological symptoms, relationship quality, internal daily stress (i.e., originating within the couple such as conflicts, worry for the partner), external daily stress (i.e., stress arising outside the couple such as job stress, stressful relatives, and so forth), and critical life events were examined with regard to their association with different sexual problems. The results support the hypotheses that (1) there is an incremental effect of stress on sexual problems after controlling for psychological symptoms and relationship quality, and that (2) it is primarily internal daily stress and in some cases critical life events rather than external daily stress that are related to sexual problems, particularly hypoactive sexual desire in women and men, sexual aversion in women, vaginismus in women, and premature ejaculation in men. Our findings indicate that the treatment of these sexual problems should address relationship issues and include a focus on helping individuals improve their stress management skills within their couple relationship.  相似文献   
109.
BACKGROUND: The ABCB1 3435C-->T single-nucleotide polymorphism (SNP) or a three-SNP haplotype containing 3435C-->T has been implicated in multidrug resistance in epilepsy in three retrospective case-control studies, but a further three have failed to replicate the association. We aimed to determine the effect of the ABCB1 gene on epilepsy drug response, using a unique large cohort of epilepsy patients with prospectively measured seizure and drug response outcomes. METHODS: The ABCB1 3435C-->T polymorphism and three-SNP haplotype, plus a comprehensive set of tag SNPs across ABCB1 and adjacent ABCB4, were genotyped in a cohort of 503 epilepsy patients with prospectively measured seizure and drug response outcomes. Clinical, demographic, and genetic data were analysed. Treatment outcome was measured in terms of time to 12-month remission, time to first seizure, and time to drug withdrawal due to inadequate seizure control or side-effects. Randomly selected genome-wide HapMap SNPs (n=129) were genotyped in all patients for genomic control. FINDINGS: Number of seizures before treatment was the dominant feature predicting seizure outcome after starting antiepileptic drug therapy, measured by both time to first seizure (hazard ratio 1.34, 95% CI 1.21-1.49, p<0.0001) and time to 12-month remission (0.83, 0.73-0.94, p=0.003). There was no association of the ABCB1 3435C-->T polymorphism, the three-SNP haplotype, or any gene-wide tag SNP with time to first seizure after starting drug therapy, time to 12-month remission, or time to drug withdrawal due to unacceptable side-effects or to lack of seizure control. INTERPRETATION: We found no evidence that ABCB1 common variation influences either seizure or drug withdrawal outcomes after initiation of antiepileptic drug therapy.  相似文献   
110.
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