全文获取类型
收费全文 | 32381篇 |
免费 | 2263篇 |
国内免费 | 128篇 |
专业分类
耳鼻咽喉 | 302篇 |
儿科学 | 1010篇 |
妇产科学 | 778篇 |
基础医学 | 3863篇 |
口腔科学 | 470篇 |
临床医学 | 5099篇 |
内科学 | 5789篇 |
皮肤病学 | 361篇 |
神经病学 | 3199篇 |
特种医学 | 731篇 |
外国民族医学 | 1篇 |
外科学 | 3594篇 |
综合类 | 395篇 |
现状与发展 | 1篇 |
一般理论 | 94篇 |
预防医学 | 4111篇 |
眼科学 | 932篇 |
药学 | 1932篇 |
中国医学 | 58篇 |
肿瘤学 | 2052篇 |
出版年
2023年 | 139篇 |
2022年 | 238篇 |
2021年 | 511篇 |
2020年 | 336篇 |
2019年 | 554篇 |
2018年 | 673篇 |
2017年 | 503篇 |
2016年 | 567篇 |
2015年 | 661篇 |
2014年 | 962篇 |
2013年 | 1481篇 |
2012年 | 2120篇 |
2011年 | 2348篇 |
2010年 | 1218篇 |
2009年 | 1104篇 |
2008年 | 1966篇 |
2007年 | 2297篇 |
2006年 | 2115篇 |
2005年 | 2202篇 |
2004年 | 2028篇 |
2003年 | 1906篇 |
2002年 | 1858篇 |
2001年 | 406篇 |
2000年 | 386篇 |
1999年 | 441篇 |
1998年 | 428篇 |
1997年 | 345篇 |
1996年 | 312篇 |
1995年 | 267篇 |
1994年 | 268篇 |
1993年 | 243篇 |
1992年 | 249篇 |
1991年 | 233篇 |
1990年 | 224篇 |
1989年 | 206篇 |
1988年 | 198篇 |
1987年 | 201篇 |
1986年 | 177篇 |
1985年 | 215篇 |
1984年 | 214篇 |
1983年 | 187篇 |
1982年 | 190篇 |
1981年 | 207篇 |
1980年 | 177篇 |
1979年 | 144篇 |
1978年 | 124篇 |
1977年 | 122篇 |
1976年 | 104篇 |
1975年 | 76篇 |
1974年 | 81篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
It is now known that chemicals and drugs may induce selective toxicity which may alter the interactions between immunocompetent cells, especially if the toxicity occurs during proliferation and differentiation. Hence, a flexible panel of sensitive in vivo and in vitro assays has been developed and validated to assess the immunotoxicity or immunopharmacology of suspect agents in rodents. The combined use of such sequential analysis methods with host resistance assays can effectively define immunomodulation following exposure to xenobiotics. Methods development, refinement and validation will be an ongoing requirement because of our rapidly expanding knowledge of the cell biology of the immune system. Classic studies of the comparative preclinical toxicology of several immunosuppressive drugs have substantiated species similarities and have contributed significantly to the development of predictive rodent models for extrapolation to humans. Studies of immunopharmacology and immunotoxicity of cyclosporin A, for example, produced both the desired pharmacology and the undesired toxicity at similar doses in both rodents and humans. When species differences are observed during toxicology studies they are most probably due to differences in absorption, disposition, metabolism, excretion, or delivered dose at the target tissue, rather than major species differences in cellular targets or cell physiology. This assumption is the basis for using rodent species to predict the toxicity of chemicals and drugs under development.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
102.
Is commercial alcohol availability related to adolescent alcohol sources and alcohol use? Findings from a multi-level study. 总被引:1,自引:1,他引:0
Mallie J Paschall Joel W Grube Carol Black Christopher L Ringwalt 《The Journal of adolescent health》2007,41(2):168-174
PURPOSE: To examine whether compliance with underage sales laws by licensed retail establishments is related to underage use of commercial and social alcohol sources, perceived ease of obtaining alcohol, and alcohol use. METHODS: In 2005, alcohol purchase surveys were conducted at 403 off-premise licensed retail establishments in 43 Oregon school districts. A survey also was administered to 3,332 11th graders in the districts. Multi-level logistic regression analyses were used to examine relationships between the school district-level alcohol sales rate and students' use of commercial and social alcohol sources, perceived ease of obtaining alcohol, past-30-day alcohol use, and heavy drinking. RESULTS: The school district-level alcohol sales rate was positively related to students' use of commercial alcohol sources and perceived alcohol availability, but was not directly associated with use of social alcohol sources and drinking behaviors. Additional analyses indicated stronger associations between drinking behaviors and use of social alcohol sources relative to other predictors. These analyses also provided support for an indirect association between the school district-level alcohol sales rate and alcohol use behaviors. CONCLUSIONS: Compliance with underage alcohol sales laws by licensed retail establishments may affect underage alcohol use indirectly, through its effect on underage use of commercial alcohol sources and perceived ease of obtaining alcohol. However, use of social alcohol sources is more strongly related to underage drinking than use of commercial alcohol sources and perceived ease of obtaining alcohol. 相似文献
103.
Carol J. Ludowese Kate J. Thompson Gurbax S. Sekhon Richard M. Pauli 《Clinical genetics》1991,40(3):194-201
We describe ten individuals with an insertional duplication 15q12----q13. Phenotypic analysis of these individuals and 15 previously reported cases of proximal 15q duplications fails to show any consistent clinical manifestations. It appears that a duplication of this region is phenotypically silent. 相似文献
104.
L Naval A Garcia Sanchez R Duran F Rodriguez F Alamillos A Dean J Fernandez 《Revue de stomatologie et de chirurgie maxillo-faciale》1991,92(1):48-50
We present a new case of Pilomatrix Carcinoma after having review the 22 cases previously published. The tumor arisen in a 74 years old male, in the left preauricular region. The lesion was excised with wide margins. A year after there is not any evidence of recurrence or metastases. 相似文献
105.
106.
Kent Burnett Gail Ironson Charles Benight Christina Wynings Debra Greenwood Charles S. Carver Dean Cruess Andrew Baum Neil Schneiderman 《Journal of traumatic stress》1997,10(4):673-681
The purpose of this study was to develop and evaluate a measure of perceived disruption during rebuilding following a disaster. Two eight-item scales, which measured intensity of disruption during the entire repair phase (Intensity-RP) and intensity of disruption during the past month (Intensity-PM) were developed and administered to 135 survivors of Hurricane Andrew. At 9 to 12 months postdisaster, Intensity-RP and Intensity-PM were both significantly associated with scores on the Global Severity Index of the SCL-90-R, and with scores on the Impact of Event-Intrusion Scale; Intensity-PM alone was significantly associated with PTSD scores. Regression analyses indicated that each scale contributed significant unique variance in predicting mental health symptoms, even after controlling for relevant demographic and initial disaster exposure variables. 相似文献
107.
108.
Vagus Nerve Stimulation Induces a Sustained Anticonvulsant Effect 总被引:17,自引:11,他引:6
Summary: Purpose: Stimulation of the vagus nerve can effectively abort several types of experimentally induced seizures in animals when administered near the time of seizure onset. Indirect evidence from human trials and animal studies suggests that the anticonvulsant effects of vagus nerve stimulation (VNS) extend beyond the duration of stimulation. We used the pentylenetetrazol model to determine whether VNS exerts a persistent anticonvulsant effect.
Methods: VNS (1 mA, 30 Hz, 500 μs pulse width) was administered continuously for 0, 1, or 60 min, or intermittently (30 s on, 5 min off) for 60 min, to awake and freely moving animals. After the end of stimulation, pentylenetetrazol (50 mg/kg i.p.) was administered to induce seizures. Time-course studies were also performed, consisting of 60 min of VNS followed by pentylenetetrazol injection after 0, 3-, 5-, and 10-min intervals.
Results: The greatest anticonvulsant effect occurred after 60 min of continuous VNS, which prevented convulsions in four of 12 rats and reduced significantly seizure duration, the total number of seizures, and number of tonic seizures. Intermittent VNS was less effective than continuous stimulation for 60 min, but more effective than that for 1 min. The anticonvulsant effect declined in a time-dependent fashion after discontinuation of VNS, with return to nonstimulated control values by 10 min.
Conclusions: The results of this study verify a persistent VNS-induced anticonvulsant effect and indicate that its efficacy is dependent on the cumulative stimulus duration. 相似文献
Methods: VNS (1 mA, 30 Hz, 500 μs pulse width) was administered continuously for 0, 1, or 60 min, or intermittently (30 s on, 5 min off) for 60 min, to awake and freely moving animals. After the end of stimulation, pentylenetetrazol (50 mg/kg i.p.) was administered to induce seizures. Time-course studies were also performed, consisting of 60 min of VNS followed by pentylenetetrazol injection after 0, 3-, 5-, and 10-min intervals.
Results: The greatest anticonvulsant effect occurred after 60 min of continuous VNS, which prevented convulsions in four of 12 rats and reduced significantly seizure duration, the total number of seizures, and number of tonic seizures. Intermittent VNS was less effective than continuous stimulation for 60 min, but more effective than that for 1 min. The anticonvulsant effect declined in a time-dependent fashion after discontinuation of VNS, with return to nonstimulated control values by 10 min.
Conclusions: The results of this study verify a persistent VNS-induced anticonvulsant effect and indicate that its efficacy is dependent on the cumulative stimulus duration. 相似文献
109.
110.