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   8807篇
  免费   844篇
  国内免费   477篇
耳鼻咽喉   83篇
儿科学   140篇
妇产科学   116篇
基础医学   1123篇
口腔科学   112篇
临床医学   1156篇
内科学   1557篇
皮肤病学   87篇
神经病学   490篇
特种医学   362篇
外国民族医学   1篇
外科学   783篇
综合类   1005篇
现状与发展   4篇
一般理论   1篇
预防医学   548篇
眼科学   421篇
药学   1036篇
  7篇
中国医学   384篇
肿瘤学   712篇
  2024年   26篇
  2023年   135篇
  2022年   315篇
  2021年   386篇
  2020年   303篇
  2019年   266篇
  2018年   254篇
  2017年   243篇
  2016年   225篇
  2015年   396篇
  2014年   412篇
  2013年   428篇
  2012年   586篇
  2011年   615篇
  2010年   402篇
  2009年   259篇
  2008年   423篇
  2007年   414篇
  2006年   402篇
  2005年   395篇
  2004年   302篇
  2003年   270篇
  2002年   253篇
  2001年   241篇
  2000年   222篇
  1999年   238篇
  1998年   116篇
  1997年   135篇
  1996年   124篇
  1995年   128篇
  1994年   78篇
  1993年   74篇
  1992年   120篇
  1991年   109篇
  1990年   96篇
  1989年   114篇
  1988年   84篇
  1987年   73篇
  1986年   62篇
  1985年   55篇
  1984年   43篇
  1983年   33篇
  1982年   30篇
  1981年   41篇
  1980年   34篇
  1979年   33篇
  1978年   28篇
  1977年   20篇
  1975年   19篇
  1974年   15篇
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
21.
Quality of Life Research - To translate and cross-cultural validate the PROMIS Pediatric-25 Profile 2.0 (PROMIS-25) into traditional Chinese, and to investigate its psychometric properties in...  相似文献   
22.
Microsurgical epididymal sperm aspiration was a great advancein the therapy of patients with non-recon-structable, obstructiveazoospermia, most notably congenital bilateral absence of thevas deferens. Using conventional in-vitro fertilization, pregnancieswere rarely achieved because the rate of oocyte fertilizationwas extremely poor. However, the use of retrieved spermatozoain conjunction with intracytoplasmic sperm injection (ICSI)has dramatically increased the likelihood of embryo formation.Typically, sperm and oocyte harvesting are performed simultaneously.We have investigated whether frozen-thawed spermatozoa workas well as fresh spermatozoa. When we had concluded from ourown population of patients (groups I and II) that they did,we adopted a policy of aspirating spermatozoa, primarily cryopreservingthem and using them for ICSI at a later date. We found the fertilizationrates of this latter cohort of patients (group III) to be excellent(37% per oocyte), and the ongoing pregnancy rate is quite satisfactory(40 % per couple, 29% per cycle). We offer this approach asan alternative to the traditional scheme because it markedlyeases the burden of partner scheduling on both the couple andthe clinicians involved. In addition, assurance of the availabilityof male partner spermatozoa can be attained prior to beginningovulation induction.  相似文献   
23.
24.
The effects of changes in temperature on primary and secondary endings of isolated cat muscle spindles were investigated under ramp-and-hold stretches and different degrees of pre-stretch. Temperature-induced alterations of the discharge frequency were compared over a temperature range of 25–35°C. Both primary and secondary endings responded to warming with increasing discharge frequencies when the spindle was pre-stretched by 5–10% of its in situ length. The following differences between the temperature effects on primary and secondary endings were observed: (1) The temperature coefficients (Q10) obtained from the discharge frequencies during the dynamic and static phase of a stretch were similar for endings of the same type, but they were larger in primary endings (range of Q10: 2.3–3.3; mean: 2.9) than in secondary endings (range of Q10: 1.6–2.2; mean: 2.0); (2) With primary endings, but not with secondary endings, the temperature sensitivity (imp s−1 °C−1) was larger during the dynamic phase than during the static phase of a stretch; (3) In primary endings, the fast and slow adaptive components occurring in the discharge frequency during the static phase of a stretch clearly increased with warming while in secondary endings, the slow decay was less affected, and the fast decay showed no change; (4) In relaxed spindles, the excitatory effect of warming was overlaid by a strong inhibitory effect as soon as the temperature exceeded about 30°C, resulting in an abrupt cessation of the background activity in most secondary endings, but not usually in primary endings. In general, warming induced an enhanced stretch sensitivity in both types of ending, and additionally an inhibitory effect that is obvious only in secondary endings of relaxed spindles. The different effects of temperature on the discharge frequency of primary and secondary afferents are assumed to be caused by different properties of their sensory membranes.  相似文献   
25.
Air-ambulance services are extremely expensive to operate and maintain. The value of their existence has been questioned in this era of rationalization and downsizing. We examined the cost, safety, flight crew composition, types of trauma, and effectiveness of our air-ambulance program at the Children's Hospital of Eastern Ontario (CHEO) over a 3-year period, 1994-1997. During this time, 392 children were aeroevacuated to CHEO, 113 surgical (29%), 136 medical (35%), and 143 neonates (36%). Of the surgical cases, 43% were transferred for orthopaedic trauma, the commonest being fractured femur, 23% for general surgical cases, most common being thoracoabdominal trauma, and 22% for neurosurgical reasons, most commonly basilar skull fractures. The average response time (time from which the call was received to the time when the helicopter reached the patient site) for all of the cases was 46 min. The average travel time (time from departure of patient site to arrival at CHEO) for these same cases was 25.59 min. The air-ambulance program for children in the Ottawa-Carleton Eastern Ontario areas, was found to be safe, effective, and allowed earlier specialized medical care to be provided.  相似文献   
26.
27.
庞玉珍  闫亦农  郝继龙 《眼科》1999,8(3):148-151
目的:评价放射状角膜切开术(RK)中微穿孔对术后1年内角膜内皮的影响。方法:应用角膜内皮镜及角膜内皮分析仪研究48例RK术中微穿孔和未穿孔眼的角膜内皮形态学变化,分别在术前及术后1、3、6、12个月行角膜内皮检查及分析。结果:比较手术前后角膜内皮的数量、平均面积、最大面积和最小面积,穿孔眼及未穿孔眼差异无显著性,但内皮细胞面积两组都有扩大的趋势。结论:RK术后一年内无论微穿孔还是未穿孔眼的角膜内皮  相似文献   
28.
Nonsurgical management of extradural hematomas in children   总被引:5,自引:0,他引:5  
With the advent of computerized tomography (CT), an increasing number of patients with only minimal neurological symptoms and no signs of brain herniation are found to harbor subacute or chronic extradural hematomas (EH's). The authors present the cases of 11 symptomatic but neurologically normal children with medium to large EH's managed by close observation. These EH's were discovered 4 hours to 6 days after injury; three were in the posterior fossa, seven over the frontoparietal convexity, and one in the temporal fossa. These clots were followed by serial CT scans. Nine children recovered without surgery from 4 to 18 days after injury, and all had evidence on CT of spontaneous clot resorption. Of these nine EH's, five clots displayed volume expansion from 5 to 16 days after injury before final resorption occurred. Expansion correlated with persistence or increase in symptoms, whereas resorption correlated with improvement. Two patients showed gradual uncal herniation on Days 6 and 8, respectively, presumably during the "expansile phase" of their clots. Both had emergency craniotomy and recovered without morbidity. It is hypothesized that the resorption dynamics of the subacute or chronic EH are similar to that of the chronic subdural hematoma, with predictable volume changes, and the outcome of each lesion depends on the interplay between the patient's intracranial pressure buffering capacity and the rate of volume change. If subtle signs of brain dysfunction are adopted to signal the failure of conservative treatment and the need for craniotomy, these patients may be safely, and many successfully, managed without surgery. Factors that influence outcome of medical treatment include the size, location, configuration, and the rapidity of accumulation of the clot, the presence of associated intradural lesions, the extracranial decompression of blood through skull diastases, and the age of the patient. These factors, the criteria for patient selection, and the indications for immediate operative intervention are discussed.  相似文献   
29.
Theoretical analysis of two models of hepatic drug clearance revealed that one powerful discriminator between them is the effect of changes of hepatic blood flow on either the emergent drug concentration or the availability of a highly extracted compound when operating under linear conditions. Lidocaine (extraction ratio 0.997) was employed in the discriminatory studies. The behavior of this drug under linear conditions (input lidocaine concentrations < 5 mg/ liter) to changes in hepatic blood flow rate (10–16 ml/min per liver) was examined in the perfused rat liver in situpreparation. The steady-state output lidocaine concentration in the blood leaving the liver was predicted better by a well-stirred model than by a parallel tube model. As anticipated, the clearance of a poorly extracted compound, antipyrine (extraction ratio 0.08),was unaltered by changes in hepatic blood flow. These experimental findings, and the data from the literature, point to the acceptance of the well-stirred model, which describes the liver as a well-stirred compartment with the drug in the hepatic venous blood being in equilibrium with that in the liver.Supported in part by National Institutes of Health Grant GM 16496 and the Patent Fund, Graduate Division, University of California, San Francisco.Abstracted in part from a dissertation submitted by K. Sandy Pang to the Graduate Division, University of California, San Francisco, California, in partial fulfillment of the Doctor of Philosophy degree requirements.  相似文献   
30.
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