全文获取类型
收费全文 | 2648篇 |
免费 | 45篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 8篇 |
综合类 | 4篇 |
化学工业 | 149篇 |
金属工艺 | 21篇 |
机械仪表 | 22篇 |
建筑科学 | 23篇 |
矿业工程 | 9篇 |
能源动力 | 12篇 |
轻工业 | 55篇 |
水利工程 | 27篇 |
石油天然气 | 2篇 |
无线电 | 44篇 |
一般工业技术 | 111篇 |
冶金工业 | 2110篇 |
原子能技术 | 8篇 |
自动化技术 | 92篇 |
出版年
2022年 | 5篇 |
2021年 | 5篇 |
2020年 | 6篇 |
2019年 | 9篇 |
2018年 | 13篇 |
2017年 | 7篇 |
2016年 | 15篇 |
2015年 | 13篇 |
2014年 | 31篇 |
2013年 | 31篇 |
2012年 | 18篇 |
2011年 | 23篇 |
2010年 | 18篇 |
2009年 | 23篇 |
2008年 | 20篇 |
2007年 | 16篇 |
2006年 | 19篇 |
2005年 | 41篇 |
2004年 | 16篇 |
2003年 | 13篇 |
2002年 | 29篇 |
2001年 | 19篇 |
2000年 | 11篇 |
1999年 | 74篇 |
1998年 | 695篇 |
1997年 | 416篇 |
1996年 | 255篇 |
1995年 | 126篇 |
1994年 | 102篇 |
1993年 | 116篇 |
1992年 | 21篇 |
1991年 | 29篇 |
1990年 | 24篇 |
1989年 | 31篇 |
1988年 | 33篇 |
1987年 | 22篇 |
1986年 | 27篇 |
1985年 | 17篇 |
1984年 | 9篇 |
1983年 | 11篇 |
1982年 | 12篇 |
1981年 | 18篇 |
1980年 | 23篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 49篇 |
1976年 | 114篇 |
1975年 | 9篇 |
1971年 | 6篇 |
1955年 | 4篇 |
排序方式: 共有2697条查询结果,搜索用时 15 毫秒
1.
2.
BACKGROUND: The enterococci have become important nosocomial pathogens. They can cause multiple site infections and enterococcal bacteremia becomes more frequently associated with a high mortality rate. Previous studies of enterococcal bacteremia showed a variety of results. To establish the significance and importance of enterococci as nosocomial pathogens in this hospital, to characterize their clinical pictures and to search for the risk factors for mortality, this retrospective study was performed. METHODS: There were 208 cases of enterococcal bacteremia which occurred from 1988 to 1992. Twenty-seven cases had no medical charts, dismissing possibility of evaluation. Finally, 181 cases of enterococcal bacteremia were analysed. RESULTS: One hundred and eighteen episodes were nosocomial infections. Polymicrobial bacteremia occurred in 68.5% of the patients and the most common co-isolate was Pseudomonas aeruginosa. Those patients (78.5%) with underlying diseases and malignancies were the most common underlying problems. The portal of entry could be found in 69.6 percent of patients, with the gastrointestinal tract the most common sources. Antimicrobial susceptibility testing showed high gentamicin resistance rate (89.5%), and ampicillin still had about 80 percent sensitivity rate. The group who received specific antibiotic therapy for enterococcus showed lower mortality (36.4% versus 47.6%). Only one case had infective endocarditis. Forty-nine patients suffered from septic shock, the cause of 30 deaths. Totally 75 patients died during hospitalization. Besides sepsis, another major cause of death was their underlying diseases itself. CONCLUSIONS: Enterococci have no doubt become important nosocomial pathogens and enterococcal bacteremia were associated with high mortality, especially in elderly patients with underlying diseases such as malignancy or diabetes. When clinically dealing with sepsis from the gastrointestinal or biliary tract, especially when previous cephalosporins therapy showed no response, the possibility of enterococcal bacteremia should always be considered. 相似文献
3.
OL Lopez RP Brenner JT Becker RF Ulrich F Boller ST DeKosky 《Canadian Metallurgical Quarterly》1997,48(6):1521-1525
We examined whether either psychotic features (e.g., delusions and hallucinations) or EEG abnormalities are associated with more rapid progression of Alzheimer's disease (AD). AD patients with psychosis have exhibited more EEG abnormalities than those without psychosis, and both abnormal EEG and psychosis have been noted to be predictors of functional and cognitive decline in AD. Ninety-five probable AD patients participating in a longitudinal study of dementia had an EEG and a semistructured psychiatric interview at baseline. Using EEG spectral analysis, we classified records as normal/abnormal based on the parasagittal mean frequency. Patients with abnormal EEGs were more functionally (e.g., Blessed Rating Scale for activities of daily living) and cognitively (e.g., Mini-Mental State) impaired than patients with normal EEG. AD patients with psychosis were only more functionally impaired than patients without psychosis. A two-factor analysis showed no interaction between abnormal EEG and psychosis. In addition, using a Cox proportional hazard model adjusted for age and education, the presence of an abnormal EEG or psychotic symptom at study entry was associated with higher risk of reaching severe cognitive and functional impairment during follow-up. Neither abnormal EEG nor the presence of psychosis predicted death. These results indicate that both abnormal EEG and psychosis are independent predictors of disease progression but not of physical survival. 相似文献
4.
NF Saba JD Sweeney LC Penn JC Lawton RL Yankee CH Huang MS Schanfield 《Canadian Metallurgical Quarterly》1997,37(3):321-324
PURPOSE: We report a case of postoperative reparalysis in the recovery room, following nebulized epinephrine. The patient was pharmacologically reversed with edrophonium after paralysis with rocuronium. CLINICAL FINDINGS: A 12-yr-old girl developed postoperative reparalysis following the intraoperative administration of rocuronium. A total of 0.92 mg.kg-1 rocuronium was administered. After surgery, pharmacological reversal was achieved with 20 mg edrophonium with 0.15 mg atropine sulfate iv 35 min after the last administration of rocuronium. Muscular relaxation was monitored using an ulnar peripheral nerve stimulator (PNS). After reversal, a full train-of-four and sustained tetanus at 50 Hz were present. In the recovery room, following nebulized epinephrine, the patient became apneic. The patient was paralyzed and an ulnar PNS demonstrated only one faint twitch. The paralysis was reversed with 1.5 mg neostigmine with 0.3 mg glycopyrrolate. CONCLUSION: Postoperative reparalysis following rocuronium may be a cause of postoperative respiratory distress. The definitive diagnosis is made using PNS and observing the response to pharmacological reversal. Nebulized epinephrine may have a previously undescribed role in the development of postoperative reparalysis. 相似文献
5.
6.
7.
8.
Human immunodeficiency virus (HIV) infection of the thymus could have profound effects on development of the immune response, particularly in children. We and others have established that in addition to infecting and depleting CD4-bearing thymocytes, functional HIV proviruses are found in thymocytes lacking surface CD4 expression. Using in vitro thymocyte cultures, we show that neither HIV-mediated down regulation of CD4 nor CD4-independent infection contributes to the localization of HIV in cells lacking the primary virus receptor. Rather, infection of a CD4-positive precursor cell (CD4 positive/CD8 positive) with subsequent differentiation into a mature CD4-negative phenotype results in productively infected CD4-negative cells. This novel mechanism may contribute to pathogenesis by distributing viral sequences into functional subsets of T cells typically refractory to HIV infection and could account for the presence of viral DNA in CD8-positive lymphocytes recently observed in patients. 相似文献
9.
BACKGROUND: Since its foundation in 1960, the International Society of Nephrology (ISN) has pursued the worldwide advancement of education, science and patient care in nephrology. This goal was achieved by means of the Society's journal and the organization of international congresses and symposia. In order to better reach its colleagues and patients in economically less developed countries, the ISN expanded its activities as of 1980 by a large number of specific programs aimed at these regions. METHODS: The first phase of activities included teaching programs, fellowship and visiting scholar programs, and the provision of travel grants to enhance accessibility to the ISN congresses. A second phase consisted of the creation of a library enhancement program, a commission on acute renal failure and--to improve the organization and efficiency--a central commission on global advancement of nephrology (COMGAN). Currently, a third phase has been entered in which all activities have been intensified: (1) under the guidance of COMGAN, supported by a large number of teaching programs and fact finding missions; (2) by establishing a renal sister program; and (3) by initiating commissions on informatics and on clinical trials. RESULTS: As a result, the ISN has reached most parts of the world, previously deprived of contact with renal science and renal patient care. The fellowship program now counts 160 fellows, who spend one or two years in training. The library enhancement program reaches 218 institutions worldwide. ISN membership has soared over the past two years with over 2,500 new members, mostly in the developing countries. They receive Kidney International and other relevant forms of information. Thus far, 135 pairs of renal units in developing and developed countries have been linked for support on a more continuous basis. ISN-sponsored congresses, symposia, and courses are being held in increasing numbers in the developing world. In many of its activities, the ISN closely collaborates with sister organizations, which also contribute financially. In total, the ISN spends annually over $1 million US from its own budget on the programs described above. CONCLUSION: The various programs and initiatives are proving helpful in advancing renal medicine in areas in need. Expansion into supporting similar programs within other medical subspecialties is being explored. 相似文献
10.