全文获取类型
收费全文 | 19432篇 |
免费 | 1848篇 |
国内免费 | 52篇 |
专业分类
耳鼻咽喉 | 258篇 |
儿科学 | 685篇 |
妇产科学 | 517篇 |
基础医学 | 2933篇 |
口腔科学 | 361篇 |
临床医学 | 2261篇 |
内科学 | 3775篇 |
皮肤病学 | 208篇 |
神经病学 | 1510篇 |
特种医学 | 768篇 |
外国民族医学 | 3篇 |
外科学 | 2458篇 |
综合类 | 512篇 |
一般理论 | 25篇 |
预防医学 | 2062篇 |
眼科学 | 261篇 |
药学 | 1584篇 |
1篇 | |
中国医学 | 6篇 |
肿瘤学 | 1144篇 |
出版年
2021年 | 277篇 |
2020年 | 155篇 |
2019年 | 273篇 |
2018年 | 289篇 |
2017年 | 208篇 |
2016年 | 241篇 |
2015年 | 290篇 |
2014年 | 426篇 |
2013年 | 615篇 |
2012年 | 832篇 |
2011年 | 915篇 |
2010年 | 487篇 |
2009年 | 413篇 |
2008年 | 761篇 |
2007年 | 806篇 |
2006年 | 793篇 |
2005年 | 804篇 |
2004年 | 728篇 |
2003年 | 670篇 |
2002年 | 673篇 |
2001年 | 605篇 |
2000年 | 643篇 |
1999年 | 526篇 |
1998年 | 249篇 |
1997年 | 205篇 |
1996年 | 227篇 |
1995年 | 221篇 |
1994年 | 191篇 |
1993年 | 180篇 |
1992年 | 495篇 |
1991年 | 488篇 |
1990年 | 461篇 |
1989年 | 413篇 |
1988年 | 402篇 |
1987年 | 409篇 |
1986年 | 412篇 |
1985年 | 415篇 |
1984年 | 311篇 |
1983年 | 266篇 |
1982年 | 207篇 |
1981年 | 164篇 |
1979年 | 305篇 |
1978年 | 224篇 |
1977年 | 201篇 |
1976年 | 165篇 |
1975年 | 176篇 |
1974年 | 181篇 |
1973年 | 189篇 |
1972年 | 167篇 |
1971年 | 163篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Total global biodiversity is estimated at between 3 and 500 × 106 species of prokaryote and eukaryote organisms spread across 70 or more phyla. The marine macrofauna alone are estimated between 0.5 and 30 × 106 species and represents a broader range of taxonomic diversity than that found in the terrestrial environment, which has been the traditional source of natural products. With a typical eukaryote possessing 50,000 genes, the global marine macrofauna are the source of 2.5 × 1010 to 1.5 × 1012 primary products and an associated extensive range of secondary products. However, only a few thousand novel compounds from marine organisms have been described. These compounds have proven unique in chemical and pharmacological terms but, as yet, no therapeutic agents have resulted. Given a broader drug discovery strategy, and facilitated by technological advances, it is predicted that the characterisation of marine chemical diversity will be accelerated. Strategies for drug discovery from the virtually untapped chemical diversity of marine organisms are discussed. © 1994 Wiley-Less, Inc. 相似文献
22.
Radical prostatectomy and prostate cancer screening: the need for national audit and research. 总被引:1,自引:1,他引:0 下载免费PDF全文
R. R. Hall 《Annals of the Royal College of Surgeons of England》1994,76(6):367-372
Public awareness of prostate cancer is increasing. Growing numbers of middle-aged men are seeking screening tests for prostate cancer and advice about its surgical treatment. Contrary to the hopes of many, the benefit of early diagnosis and by radical prostatectomy remains in doubt. Recent analyses suggest that ''watchful waiting'', with no immediate treatment, may be an equally effective option. If this is true, why screen? Why operate? These questions should be a cause of concern to more than 1 million British men who are unaware that they have prostate cancer and to the providers of health care who have failed to address this dilemma. A national audit and randomised clinical trial are indicated. 相似文献
23.
J. O’Byrne S. Eustace M. M. Stephens M. N. M. R. Farahat G. Yanni R. Posten G. S. Panayi S. Sant R. Costello M. Barry J. Hassan C. Feighery B. Bresnihan A. Whelan F. Coakley A. M. de Paor R. B. Reilly E. B. Casey V. J. Tormey G. Kearns K. Gaffney P. J. Freyne M. Callaghan O. FitzGerald D. Veale E. O’Nuallain D. Reen D. Veale M. Farrell O. FitzGerald S. Rogers L. Barnes R. J. Coughlan C. McCarthy M. McDermott D. Hourihane C. O'Morain S. O'Reilly P. Hartley E. Casey L. Clancy F. Mulcahy N. Hall A. Murphy C. Breen D. Kelleher M. Abuzakouk C. O'Farrelly 《Irish journal of medical science》1992,161(6):438-442
24.
A Thalamic Contribution to Arousal-induced, Non-photic Entrainment of the Circadian Clock of the Syrian Hamster 总被引:3,自引:0,他引:3
Elizabeth S. Maywood Emma Smith Stephanie J. Hall Michael H. Hastings 《The European journal of neuroscience》1997,9(8):1739-1747
It is well established that the circadian clock of the suprachiasmatic nuclei (SCN) is entrained by light. More recently, the potent effects of arousing, non-photic cues on the clock have been recognized. The neural mediators of non-photic entrainment are yet to be identified. To examine the contribution of the thalamic intergeniculate leaflet (IGL) and its NPY-immunopositive projection, the geniculo-hypothalamic tract to non-photic entrainment by arousal, male Syrian hamsters received lesions of the IGL (IGLX) which ablated NPY-immunoreactivity in the SCN. Their circadian responses to both photic and non-photic cues were then tested. Lesions resulted in a delay in the timing of activity onset following lights out, but had no effect on the behavioural or cellular circadian responses to phase-advancing light pulses presented at circadian time (CT) CT19 (where CT12 represents the time of activity onset). Injection with a benzodiazepine (chlordiazepoxide, 100 mg/kg) at CT6 suppressed wheel-running, increased general locomotion of intact controls and induced large phase advances of the circadian rhythm of wheel-running. Chlordiazepoxide also inhibited wheel-running in lesioned animals, but there was no significant increase in general locomotion and the lesioned animals did not phase advance. Serial arousal by injection of saline at intervals of 23.5 h for 6 days entrained the circadian rhythm of wheel-running of intact hamsters and was associated with an increase in general locomotor activity. Entrainment by serial arousal was abolished by IGLX. However, the lesioned animals did show a clear behavioural response to every presentation of the non-photic cue. These results show that the IGL is a necessary component of the neural pathways mediating both arousal- and benzodiazepine-induced non-photic entrainment. 相似文献
25.
News for the Practitioner 相似文献
26.
Follow up study of children born elsewhere but attending schools in Seascale, West Cumbria (schools cohort) 总被引:4,自引:0,他引:4
M J Gardner A J Hall S Downes J D Terrell 《British medical journal (Clinical research ed.)》1987,295(6602):819-822
Records on 1546 children who were identified as having attended schools in Seascale up to November 1984 and were born since 1950 but not in the civil parish were studied. These children lived in or near Seascale for a period of time while they were attending one or more of three local schools and are an additional group to the 1068 children who were identified as born to mothers resident in Seascale in an accompanying study. Even though some of the schoolchildren apparently remained in the village for a short period only all but 7% were followed up through the National Health Service Central Register. Mortality among these children to 30 June 1986 is comparable to that expected at national rates. From all causes there were 10 observed deaths compared with 12.69 expected--a ratio of 0.79 (95% confidence interval 0.38 to 1.45)--and from cancer one observed death compared with 2.04 expected--a ratio of 0.49 (95% CI 0.01 to 2.73). No deaths from leukaemia or lymphoma were reported, but only 0.83 was expected. Since 1971 (the year when cases of cancer were first notified to the NHS Central Register) three non-fatal cases of cancer were reported, including two lymphomas, compared with 2.04 expected and two cases of carcinoma in situ of the cervix compared with 1.79 expected. In addition, there was a case of leukaemia among the schoolchildren which was known previously and had been diagnosed in 1968. There is an interesting difference between the results of this study and the results of the study of children born to mothers who were resident in Seascale. In the latter study there was an excess of leukaemia and of other cancers, but a similar finding is not apparent among children who spent some time at schools in Seascale but were born elsewhere. This raises the question of whether one or more aetiological factors in childhood cancer were acting on a locality specific basis before birth or early in life. This cannot be answered from these cohort studies, but it is hoped that the case-control study that is under way in West Cumbria will provide relevant information. 相似文献
27.
28.
A survey of endoscopy units in the West Midlands, UK, was undertaken to ascertain the management of colonic perforation during colonoscopy. Fifteen perforations were reported from a total of 17,500 colonoscopies performed in 14 units (a rate of 0.09 per cent). In seven patients the diagnosis was suspected or diagnosed immediately and in the remaining eight 2-72 h later. Four patients with associated pathology (carcinoma, Crohn's disease, ulcerative colitis and a polyp) had resection and primary anastomosis. Seven patients had a simple oversew, four of these having had a delayed diagnosis. In four cases the site of perforation was not identified, but only one patient had conservative treatment. Three patients had drainage and a defunctioning colostomy. There was no significant morbidity following treatment. It is recommended that patients who have had a good bowel preparation should be treated conservatively unless there is a large perforation or an underlying carcinoma. 相似文献
29.
BACKGROUND: We reviewed the publication record of all protocols submitted to the Capital District Health Authority Research Ethics Board (REB) in Halifax, Nova Scotia, for the period 1995-1996. Because of a heightened awareness of the issue, we hypothesized that there would be less publication bias (a failure to report negative results) and a higher publication rate from completed studies, than previously reported. METHODS: Closed studies were identified from the REB database. Publications were identified by the investigators, requests from sponsors, and a literature review. For each publication, we identified authors, title, journal, number of subjects enrolled, and whether or not the publication was a report of a randomized clinical trial. Comparisons were done using a Student's t test, the Chi-square statistic, or Fisher's exact test as appropriate. RESULTS: From the database of closed studies, 106 remained unpublished, while completed investigations resulted in 84 publications (44% publication rate). The median time to publication was 32.5 months. Publication of statistically significant results occurred in 71/84 trials. Publication of protocols submitted by departments ranged from 91% (anesthesia; 10/11) to 25% [nursing; 2/8 (P<0.05)]. Trials investigating new drugs in Phase 3 or 4 studies were more likely to be published than trials investigating agents in Phase 1 or 2 (P<0.05), and were less likely to be published if sponsored by a pharmaceutical company (P<0.05). CONCLUSIONS: Publication bias continues to be a problem, particularly for early phase investigative studies. Our results suggest that a different approach is required to reduce publication bias. The role that REBs and peer-reviewed journals might play requires further exploration. 相似文献