全文获取类型
收费全文 | 11536篇 |
免费 | 1049篇 |
国内免费 | 15篇 |
专业分类
耳鼻咽喉 | 91篇 |
儿科学 | 223篇 |
妇产科学 | 238篇 |
基础医学 | 1490篇 |
口腔科学 | 169篇 |
临床医学 | 1595篇 |
内科学 | 2154篇 |
皮肤病学 | 148篇 |
神经病学 | 975篇 |
特种医学 | 492篇 |
外科学 | 1792篇 |
综合类 | 279篇 |
一般理论 | 19篇 |
预防医学 | 1362篇 |
眼科学 | 169篇 |
药学 | 887篇 |
1篇 | |
中国医学 | 13篇 |
肿瘤学 | 503篇 |
出版年
2023年 | 66篇 |
2022年 | 93篇 |
2021年 | 186篇 |
2020年 | 118篇 |
2019年 | 179篇 |
2018年 | 205篇 |
2017年 | 157篇 |
2016年 | 186篇 |
2015年 | 191篇 |
2014年 | 258篇 |
2013年 | 368篇 |
2012年 | 553篇 |
2011年 | 612篇 |
2010年 | 350篇 |
2009年 | 333篇 |
2008年 | 525篇 |
2007年 | 536篇 |
2006年 | 496篇 |
2005年 | 551篇 |
2004年 | 545篇 |
2003年 | 441篇 |
2002年 | 405篇 |
2001年 | 404篇 |
2000年 | 395篇 |
1999年 | 409篇 |
1998年 | 163篇 |
1997年 | 109篇 |
1996年 | 122篇 |
1995年 | 111篇 |
1994年 | 101篇 |
1993年 | 82篇 |
1992年 | 297篇 |
1991年 | 267篇 |
1990年 | 227篇 |
1989年 | 243篇 |
1988年 | 224篇 |
1987年 | 200篇 |
1986年 | 186篇 |
1985年 | 178篇 |
1984年 | 124篇 |
1983年 | 142篇 |
1982年 | 77篇 |
1981年 | 72篇 |
1979年 | 122篇 |
1977年 | 83篇 |
1975年 | 62篇 |
1974年 | 91篇 |
1973年 | 83篇 |
1972年 | 78篇 |
1971年 | 83篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Penny A Cook Jennifer Downing Philip C Wheater Mark A Bellis Karen Tocque Qutub Syed Penelope A Phillips-Howard 《BMC public health》2009,9(1):78
Background
Patient choice and access to health care is compromised by many barriers including travel distance. Individuals with the human immunodeficiency virus (HIV) can seek free specialist care in Britain, without a referral, providing flexible access to care services. Willingness to travel beyond local services for preferred care has funding and service implications. Data from an enhanced HIV surveillance system were used to explore geodemographic and clinical factors associated with accessing treatment services. 相似文献992.
993.
A F Eidson A Taya G L Finch M D Hoover C Cook 《Journal of toxicology and environmental health》1991,34(4):433-448
This study was designed to determine the dosimetry within macrophages of beryllium compounds administered at sublethal doses. Information on the dosimetry of beryllium within macrophages is required to guide further efforts to isolate and characterize beryllium-containing haptens. Inhalation of beryllium aerosols can cause chronic berylliosis, a progressive, granulomatous fibrosis of the lung. Studies in laboratory animals indicate that alveolar macrophages take up beryllium compounds and participate in a hypersensitivity immune response to beryllium-containing antigen. Beagle dog macrophage cultures were incubated with 7BeSO4 in solution or with suspensions of 7BeO particles that had been calcined at 500 or 1000 degrees C. Beryllium-7 was measured in fractions collected from cultures after successive centrifugation and filtration steps at 2, 6, 20, and 48 h after addition. An insignificant percentage of BeSO4 was taken up by the cells and did not cause cytotoxicity. Maximum BeO uptake occurred within 6 h, was 60 +/- 6% of added BeO, and was independent of BeO calcination temperature or specific surface area. Approximately 22% of 500 degrees C BeO dissolved within 48 h after addition to cell culture, concurrent with 39% cell killing. Dissolved beryllium remained associated with cells until a cytotoxic concentration was reached (2.2 x 10(-5) M, 15 nmol Be/10(6) cells), when the beryllium was released into the medium. There was no significant dissolution of the 1000 degrees C BeO within 48 h, and no significant cell killing. The results indicate that beryllium dissolved from phagocytized BeO was more cytotoxic than soluble beryllium added extracellularly. The data support an interactive mechanism in which phagocytized BeO particles were dissolved, and dissolved beryllium remained associated with the macrophage until a cytotoxic concentration accumulated, whereupon the beryllium was released to the medium and not appreciably taken up by viable cells. 相似文献
994.
995.
996.
Novel fluorine-substituted deaza analogues of 5-azacytidine (AZC) and 5-aza-2'-deoxycytidine (dAZC) (3-deazacytosines) have been synthesized and tested for antitumor activity. Thus, 4-amino-3,5-difluoro-1-beta-D-ribofuranosyl-2(1H)-pyridinone (16), 4-amino-3-fluoro-1-beta-D-ribofuranosyl-2(1H)-pyridinone (17), 4-amino-5-fluoro-1-beta-D-ribofuranosyl-2(1H)-pyridinone (18), 4-amino-1-(2-deoxy-beta-D-erythro-pentofuranosyl)-3,5-difluoro-2 (1H)-pyridinone (25), 4-amino-1-(2-deoxy-beta-D-erythro-pentofuranosyl)-3-fluoro-2(1H)-pyridin one (26) 4-amino-1-(2-deoxy-alpha-D-erythro-pentofuranosyl)-3,5-difluoro-2(1H)-++ +pyridinon e (27), and 4-amino-1-(2-deoxy-alpha-D-erythro-pentofuranosyl)-3-fluoro-2 (1H)-pyridinone (28) were prepared by standard glycosylation procedures. Requisite heterocycle 4-amino-3,5-difluoro-2(1H)-pyridinone (6) was prepared in five steps from pentafluoropyridine (1). Other requisite fluoro heterocycles, 4-amino-3-fluoro-2(1H)-pyridinone (7) and 4-amino-5-fluoro-2(1H)-pyridinone (8), were obtained from a bis-defluorination of 4-amino-3,5,6-trifluoro-2(1H)-pyridinone (3) with hydrazine. Acetylation of 17 provided 4-amino-3-fluoro-1-(2,3,5-tri-O-acetyl-beta-D-ribofuranosyl)-2(1H)-pyrid inone (29). Structure proof of target nucleosides and heterocyclic compounds was provided by X-ray diffraction, 19F and 1H NMR, and UV. The ID50 values of fluorine-substituted 3-deazacytosines and 3-deazacytidines were greater than 1 X 10(-5) M in L1210 lymphoid leukemia cells in culture. Nucleoside 17 and its tri- and tetraacetates were the most active compounds with ID50 values of 1.07 X 10(-5), 1.23 X 10(-5), and 1.25 X 10(-5) M, respectively. The target nucleosides and intermediate heterocycles were inactive against P388 and L1210 lymphocytic leukemia in mice, except nucleoside 17 (NSC-378066) and its triacetate 29 (NSC-382021). Nucleoside 17 exhibited confirmed DN2 activity (% T/C 169-230) at five dose levels (25-300 mg/kg). Prodrug 29 exhibited similarly confirmed L1210 in vivo activity. 相似文献
997.
998.
Correlates of headache in a population-based cohort of elderly 总被引:3,自引:0,他引:3
N R Cook D A Evans H H Funkenstein P A Scherr A M Ostfeld J O Taylor C H Hennekens 《Archives of neurology》1989,46(12):1338-1344
Data from a community-based study of 3811 persons aged 65 years and older were used to describe the characteristics of headache in the elderly. Subjects were asked whether they experienced headache in the past year, the frequency and severity of their headaches, and whether they experienced three symptoms of migraine: unilaterality, nausea or vomiting, an aura preceding the headache. Prevalence of headache in those aged more than 65 years declined with age in both men and women; women had a higher prevalence in each age group. The same was true for frequent, severe, and migrainous headache. We examined age- and sex-adjusted correlations of headache with several medical and social factors. Prevalence of any headache was strongly associated with joint pain, depression, bereavement, waking during the night, use of eyeglasses, symptoms of temporomandibular joint dysfunction, and self-assessment of health. Similar variables were associated with frequency, severity, and migrainous symptoms, and thus could not be distinguished among these various types. 相似文献
999.
Controlled discontinuation of benzodiazepine treatment for patients with panic disorder 总被引:1,自引:0,他引:1
OBJECTIVE: The purpose of this study was to compare the effects of discontinuing treatment with intermediate- and long-acting benzodiazepines. METHOD: Fifty patients with panic disorder who had taken part in a double-blind treatment study and had responded to alprazolam, diazepam, or placebo for 8 months were asked to stop taking these medications gradually. RESULTS: After a relatively rapid dose reduction, the majority of patients relapsed. Rebound anxiety and withdrawal symptoms were identified in a substantial minority of patients. Those who were taking alprazolam showed earlier and more intense rebound anxiety and withdrawal symptoms than did the patients who received diazepam. Both the level of pretreatment anxiety and the drug the patient was taking predicted the level of anxiety when drug treatment was discontinued. CONCLUSIONS: The findings indicate that withdrawal phenomena commonly occur after patients stop taking benzodiazepines and that they are more frequent after discontinuation of treatment with shorter-acting drugs. 相似文献
1000.