全文获取类型
收费全文 | 23402篇 |
免费 | 1828篇 |
国内免费 | 85篇 |
专业分类
耳鼻咽喉 | 234篇 |
儿科学 | 971篇 |
妇产科学 | 601篇 |
基础医学 | 3124篇 |
口腔科学 | 695篇 |
临床医学 | 2647篇 |
内科学 | 4648篇 |
皮肤病学 | 339篇 |
神经病学 | 1821篇 |
特种医学 | 1060篇 |
外科学 | 3125篇 |
综合类 | 473篇 |
一般理论 | 43篇 |
预防医学 | 2202篇 |
眼科学 | 351篇 |
药学 | 1456篇 |
1篇 | |
中国医学 | 19篇 |
肿瘤学 | 1505篇 |
出版年
2022年 | 153篇 |
2021年 | 351篇 |
2020年 | 248篇 |
2019年 | 369篇 |
2018年 | 414篇 |
2017年 | 367篇 |
2016年 | 366篇 |
2015年 | 445篇 |
2014年 | 636篇 |
2013年 | 825篇 |
2012年 | 1135篇 |
2011年 | 1225篇 |
2010年 | 705篇 |
2009年 | 609篇 |
2008年 | 1100篇 |
2007年 | 1231篇 |
2006年 | 1120篇 |
2005年 | 1100篇 |
2004年 | 967篇 |
2003年 | 948篇 |
2002年 | 816篇 |
2001年 | 661篇 |
2000年 | 637篇 |
1999年 | 533篇 |
1998年 | 311篇 |
1997年 | 265篇 |
1996年 | 263篇 |
1995年 | 264篇 |
1994年 | 239篇 |
1993年 | 215篇 |
1992年 | 477篇 |
1991年 | 459篇 |
1990年 | 449篇 |
1989年 | 450篇 |
1988年 | 417篇 |
1987年 | 366篇 |
1986年 | 323篇 |
1985年 | 393篇 |
1984年 | 296篇 |
1983年 | 272篇 |
1982年 | 169篇 |
1979年 | 215篇 |
1978年 | 188篇 |
1977年 | 155篇 |
1976年 | 158篇 |
1975年 | 166篇 |
1974年 | 158篇 |
1973年 | 197篇 |
1972年 | 159篇 |
1971年 | 142篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
A retrospective study of 42 adolescent patients diagnosed as being pregnant between June 1987 and February 1990 at the Downtown Health Center (DHC), an inner city pediatric primary care clinic, was conducted to determine whether patients referred to a hospital-based Teen Pregnancy Clinic (TPC) were seen within a reasonable period of time. The frequency of sexually transmitted diseases (STDs) was also determined when these women were initially seen at TPC. Only 5 of the 42 patients seen at DHC had a pelvic exam prior to referral. Of the 40 patients seen at TPC, 20% were not seen until four weeks or more after initial diagnosis. Fifty percent had a STD. Pediatricians should recognize that pregnant teenagers may have a significant delay between diagnosis of pregnancy and entry into obstetrical care. Pelvic exam including cultures for STDs is recommended prior to referral. 相似文献
74.
Between July 1985 and January 1990, pseudomonas scepticaemia occurred in 19 out of 584 patients with AIDS attending the Westminster and St Stephen's AIDS Unit, London, UK. Ten of these 19 were being treated for active cytomegalovirus infection. Fourteen of the 19 patients had a central venous catheter in situ, which was the source of infection in 11. Seven patients died. Mortality was significantly greater in those patients infected with Pseudomonas aeruginosa, in those patients whose source of infection was not the central venous line, and in those patients whose central line was not removed. 相似文献
75.
State smoking prevalence estimates: a comparison of the Behavioral Risk Factor Surveillance System and current population surveys. 总被引:4,自引:3,他引:1 下载免费PDF全文
D R Arday S L Tomar D E Nelson R K Merritt M W Schooley P Mowery 《American journal of public health》1997,87(10):1665-1669
OBJECTIVES: This study examined whether there are systematic differences between the Behavioral Risk Factor Surveillance System (BRFSS) and the Current Population Survey (CPS) for state cigarette smoking prevalence estimates. METHODS: BRFSS telephone survey estimates were compared with estimates from the US Census CPS tobacco-use supplements (the CPS sample frame includes persons in households without telephones). Weighted overall and sex- and race-specific BRFSS and CPS state estimates of adults smoking were analyzed for 1985, 1989, and 1992/1993. RESULTS: Overall estimates of smoking prevalence from the BRFSS were slightly lower than estimates from CPS (median difference: -2.0 percentage points in 1985, -0.7 in 1989, and -1.9 in 1992/1993; P < .05 for all comparisons), but there was variation among states. Differences between BRFSS and CPS estimates were larger among men than among women and larger among Blacks than among Hispanics or Whites; for most states, these differences were not significant. CONCLUSIONS: The BRFSS generally provides state estimates of smoking prevalence similar to those obtained from CPS, and these are appropriate for ongoing state surveillance of smoking prevalence. 相似文献
76.
High-dose gadoteridol in MR imaging of intracranial neoplasms. 总被引:6,自引:0,他引:6
V M Runge J E Kirsch V J Burke A C Price K L Nelson G S Thomas B L Dean C Lee 《Journal of magnetic resonance imaging : JMRI》1992,2(1):9-18
Twelve patients with a high suspicion of brain metastases by previous clinical or radiologic examinations were studied in a phase III investigation with magnetic resonance (MR) imaging at 1.5 T after a bolus intravenous injection of 0.1 mmol/kg gadoteridol followed at 30 minutes by a second bolus injection of 0.2 mmol/kg gadoteridol. All lesions were best demonstrated (showed greatest enhancement) at the 0.3-mmol/kg (cumulative) dose, with image analysis confirming signal intensity enhancement in the majority of cases after the second gadoteridol injection. More lesions were detected with the 0.3-mmol/kg dose than with the 0.1-mmol/kg dose, and more lesions were detected with the 0.1-mmol/kg dose than on precontrast images. In this limited clinical trial, high-dose gadoteridol injection (0.3-mmol/kg cumulative dose) provided improved lesion detection on MR images specifically in intracranial metastatic disease. 相似文献
77.
Nelson T Yamagata Bruce L Miller Duncan McBride Linda Chang Francis Chiang Diana Nikas Diane Osborne Steven D Buchthal 《Journal of neuroimaging》1994,4(1):23-28
The chemical characteristics of 10 neoplastic and 11 infectious brain masses were studied by in vivo 1H magnetic resonance spectroscopy. In tumors, peak height ratios of n-acetyl-L-aspartate to choline were decreased compared to those in normal brain tissue and infectious masses (p < 0.02), but the ratios in normal brains and those with infections did not differ. N-acetyl-L-aspartate—to-creatine/phosphocreatine ratios were significantly lower in infectious masses and tumors compared to normal brain tissue (p = 0.003). However, in progressive multifocal leukoencephalopathy, N-acetyl-L-aspartate appeared relatively unchanged. Lactate was greater than choline in 9 of 11 brains with infection, 0 of 14 control brains, and 1 of 10 tumors. Lactate-to-choline ratios were significantly elevated in infectious masses compared with tumors (p < 0.01). 1H magnetic resonance spectroscopy is promising for the noninvasive diagnosis of focal brain masses. 相似文献
78.
79.
During a prospective evaluation of intravenous therapy with peripheral Teflon catheters in children, we found 30 episodes of phlebitis (10.4%). This rate is less than that reported in adults. Catheter colonization was not related to phlebitic episodes, and catheter-related infections did not occur. No patient's hospital course was prolonged because of phlebitis. Thirty percent of the episodes developed after the catheter was removed, and premonitory symptoms were not helpful in predicting the onset of phlebitis. Factors associated with an increased phlebitic risk were parenteral nutrition, administration of nafcillin sodium or aminoglycosides, and patient age. Parenteral nutrition prolonged the course of phlebitis. No factors hastened the onset of phlebitis. The duration of cannulation was not significantly related to phlebitis, suggesting that in some children the catheters can remain in place longer than 72 hours. 相似文献
80.
F R Nelson D Holloway A K Mohamed 《Journal of the American Mosquito Control Association》1986,2(3):296-299
In a laboratory study, the insect growth regulator, cyromazine, exerted a high level of biological activity on Aedes aegypti and Culex quinquefasciatus treated in the 4th larval instar. At 1.5 and 1.0 ppm this IGR produced 97 and 99% inhibition of emergence in adult Ae. aegypti, respectively. In Cx. quinquefasciatus, there was 99% inhibition at 1 ppm and complete inhibition at 1.5 ppm. The overall pupal mortality was higher than larval or adult stages of both species. This material induced different types of morphogenetic abnormalities in pupae and adults of the 2 species similar to those induced by other IGRs. However, most abnormalities were observed in the pupal stage. Adverse effects were not detected on the 4 mosquito predator species during the acute or posttreatment tests. 相似文献