全文获取类型
收费全文 | 4211篇 |
免费 | 25篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 32篇 |
综合类 | 2篇 |
化学工业 | 98篇 |
金属工艺 | 9篇 |
机械仪表 | 14篇 |
建筑科学 | 6篇 |
能源动力 | 28篇 |
轻工业 | 32篇 |
水利工程 | 1篇 |
石油天然气 | 2篇 |
无线电 | 44篇 |
一般工业技术 | 88篇 |
冶金工业 | 3781篇 |
原子能技术 | 4篇 |
自动化技术 | 109篇 |
出版年
2023年 | 18篇 |
2022年 | 22篇 |
2021年 | 27篇 |
2020年 | 21篇 |
2019年 | 17篇 |
2018年 | 31篇 |
2017年 | 16篇 |
2016年 | 18篇 |
2015年 | 9篇 |
2014年 | 19篇 |
2013年 | 53篇 |
2012年 | 27篇 |
2011年 | 24篇 |
2010年 | 21篇 |
2009年 | 14篇 |
2008年 | 12篇 |
2007年 | 16篇 |
2006年 | 7篇 |
2005年 | 10篇 |
2004年 | 5篇 |
2003年 | 16篇 |
2002年 | 5篇 |
2001年 | 4篇 |
2000年 | 10篇 |
1999年 | 103篇 |
1998年 | 1063篇 |
1997年 | 593篇 |
1996年 | 451篇 |
1995年 | 233篇 |
1994年 | 189篇 |
1993年 | 242篇 |
1992年 | 37篇 |
1991年 | 60篇 |
1990年 | 67篇 |
1989年 | 95篇 |
1988年 | 50篇 |
1987年 | 75篇 |
1986年 | 50篇 |
1985年 | 66篇 |
1984年 | 3篇 |
1983年 | 9篇 |
1982年 | 23篇 |
1981年 | 21篇 |
1980年 | 37篇 |
1979年 | 3篇 |
1978年 | 7篇 |
1977年 | 89篇 |
1976年 | 243篇 |
1975年 | 7篇 |
1955年 | 3篇 |
排序方式: 共有4250条查询结果,搜索用时 0 毫秒
981.
JW Warren 《Canadian Metallurgical Quarterly》1996,17(4):212-214
From 1978 to 1983, closed reduction and fixation with frog-leg cast were used to treat congenital hip dislocation in children in our hospital. Sixty-two patients with such hip dislocation were treated by these methods. Among them 38 patients under 3 years of age were followed up for 12 to 16 years (mean 13 years). Encouraging results were obtained and the reduction rate was 97.9%. This treatment revealed that after closed reduction the fixation and the slight movement of the femoral head in the cast under the fixation are a self-remould action that may promote the growth of the acetabulum and the femoral head resulting in normal development of the hip. 相似文献
982.
AM Hutchins JW Lampe MC Martini DR Campbell JL Slavin 《Canadian Metallurgical Quarterly》1995,95(7):769-774
OBJECTIVE: To compare the effect of vegetable, fruit, and legume consumption on urinary isoflavonoid phytoestrogen and lignan excretion. DESIGN: After 4 days of data collection, during which subjects consumed their habitual diets, subjects were randomly placed on four 9-day controlled experimental diets with each subject receiving each diet in a random order. SUBJECTS: Seven men and three women, aged 20 to 35 years, were recruited from the University of Minnesota Twin Cities community. INTERVENTIONS: All subjects consumed four experimental diets in an assigned random order: a controlled basal diet, a legume/allium diet (containing garbanzo beans, garlic, and onions), and diets low or high in vegetables and fruits (containing apples, pears, potatoes, and carrots). MAIN OUTCOME MEASURES: Urine samples that were collected while subjects consumed their habitual diets and during the last 3 days of each feeding period were analyzed for isoflavonoid and lignan content using isotope dilution gas chromatography-mass spectrometry. STATISTICAL ANALYSIS PERFORMED: The effect of vegetable and fruit intake on urinary isoflavonoid and lignan excretion was analyzed using the general linear model procedure. Post hoc comparisons were made using Duncan's multiple range test. RESULTS: Subjects excreted more of the lignan enterodiol on the high vegetable/fruit diet compared with the basal and legume/allium diets (P = .03); more of the isoflavonoids O-desmethylangolensin (O-DMA), genistein, and sum of isoflavonoids on the legume/allium diet compared with the other controlled diets (P < .05); and more of the isoflavan equol on the basal and legume/allium diets compared with the high vegetable/fruit diet (P < .01). Subjects who excreted higher levels of equol on the basal and legume/allium diets also consumed more of the milk-based pudding provided as part of the controlled diets. CONCLUSIONS: Urinary lignan and isoflavonoid excretion changed in response to alterations in vegetable, fruit, and legume intake under controlled dietary conditions. 相似文献
983.
Z Li JW Knowles D Goyeau S Prabhakar DB Short AG Perkins MF Goy 《Canadian Metallurgical Quarterly》1996,111(6):1714-1721
BACKGROUND & AIMS: Guanylin, an endogenous gastrointestinal peptide, causes the translocation of NaCl from interstitial fluid to the intestinal lumen. The aim of this study was to examine whether changes in dietary salt intake lead to compensatory changes in expression of the guanylin signaling pathway. METHODS: Rats received low-, normal-, or high-sodium diets for 1 week. Colonic guanylin expression was evaluated by Western and Northern blotting, rates of guanylin secretion by measuring biologically active guanylin released into the medium from colon explants, and expression of the guanylin receptor (C-type guanylate cyclase) by Northern blotting and bioassay. RESULTS: By every criterion, the low-salt diet reduced expression of guanylin to 30%-40% of the level found in control animals. Guanylin receptor expression was also decreased, although less dramatically and with a lower statistical significance. For both guanylin and guanylin receptor, the high-salt diet had no significant effect on expression. CONCLUSIONS: The data support the hypothesis that the guanylin pathway is down-regulated as an adaptive response to salt restriction. 相似文献
984.
985.
Lymph node and spleen cells from mice immunized with sea nettle (Chrysaora quinquecirrha) venom exhibited a proliferative response after exposure to the homologous antigen or that of a related jellyfish, Physalia (Portuguese man-o'-war). Native venom was a more effective stimulant than heated, non-lethal venom. Ultraviolet light treatments administered to the skin either before or after venom sensitization suppressed the proliferative response of these internal immune cells. 相似文献
986.
987.
AS Dajani KA Taubert W Wilson AF Bolger A Bayer P Ferrieri MH Gewitz ST Shulman S Nouri JW Newburger C Hutto TJ Pallasch TW Gage ME Levison G Peter G Zuccaro 《Canadian Metallurgical Quarterly》1997,128(8):1142-1151
OBJECTIVE: To update recommendations issued by the American Heart Association last published in 1990 for the prevention of bacterial endocarditis in individuals at risk for this disease. PARTICIPANTS: An ad hoc writing group appointed by the American Heart Association for their expertise in endocarditis and treatment with liaison members representing the American Dental Association, the infectious Diseases Society of America, the American Academy of Pediatrics and the American Society for Gastrointestinal Endoscopy. EVIDENCE: The recommendations in this article reflect analyses of relevant literature regarding procedure-related endocarditis, in vitro susceptibility data of pathogens causing endocarditis, results of prophylactic studies in animal models of endocarditis and retrospective analyses of human endocarditis cases in terms of antibiotic prophylaxis usage patterns and apparent prophylaxis failures. MEDLINE database searches from 1936 through 1996 were done using root words endocarditis, bacteremia and antibiotic prophylaxis. Recommendations in this document fall into evidence level III of the U.S. Preventive Services Task Force categories of evidence. CONSENSUS PROCESS: The recommendations were formulated by the writing group after specific therapeutic regimens were discussed. The consensus statement was subsequently reviewed by outside experts not affiliated with the writing group and by the Science Advisory and Coordinating Committee of the American Heart Association. These guidelines are meant to aid practitioners but are not intended as the standard of care or as a substitute for clinical judgment. CONCLUSIONS: Major changes in the updated recommendations include the following: (1) emphasis that most cases of endocarditis are not attributable to an invasive procedure; (2) cardiac conditions are stratified into high-, moderate- and negligible-risk categories based on potential outcome if endocarditis develops; (3) procedures that may cause bacteremia and for which prophylaxis is recommended are more clearly specified; (4) an algorithm was developed to more clearly define when prophylaxis is recommended for patients with mitral valve prolapse; (5) for oral or dental procedures the initial amoxicillin dose is reduced to 2 g, a follow-up antibiotic dose is no longer recommended, erythromycin is no longer recommended for penicillin-allergic individuals, but clindamycin and other alternatives are offered. 相似文献
988.
Recent in situ three-dimensional structural studies have provided a new model for the 30 nm chromatin fiber. In addition, research during the past year has revealed some of the molecular complexity of non-histone chromosomal proteins. Still to come is the unification of molecular insights with chromosomal architecture. 相似文献
989.
990.