全文获取类型
收费全文 | 976篇 |
免费 | 2篇 |
专业分类
化学工业 | 1篇 |
机械仪表 | 1篇 |
无线电 | 3篇 |
一般工业技术 | 3篇 |
冶金工业 | 967篇 |
原子能技术 | 1篇 |
自动化技术 | 2篇 |
出版年
2022年 | 1篇 |
2016年 | 1篇 |
2014年 | 2篇 |
2013年 | 1篇 |
2011年 | 1篇 |
2008年 | 3篇 |
2007年 | 1篇 |
2006年 | 1篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2002年 | 1篇 |
1999年 | 22篇 |
1998年 | 286篇 |
1997年 | 169篇 |
1996年 | 106篇 |
1995年 | 51篇 |
1994年 | 62篇 |
1993年 | 57篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 14篇 |
1989年 | 10篇 |
1988年 | 10篇 |
1987年 | 7篇 |
1986年 | 1篇 |
1985年 | 6篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1978年 | 5篇 |
1977年 | 35篇 |
1976年 | 81篇 |
1975年 | 2篇 |
1955年 | 2篇 |
排序方式: 共有978条查询结果,搜索用时 0 毫秒
31.
Picrotoxin (50 microM) elicited rhythmic synchronized bursting in CA3 pyramidal cells in guinea pig hippocampal slices. Addition of the selective group I metabotropic glutamate receptor (mGluR) agonist (S)-3,5-dihydroxyphenylglycine (25 microM) elicited an increase in burst frequency. This was soon followed by a slowly progressive increase in burst duration (BD), converting the brief 250-520 ms picrotoxin-induced synchronized bursts into prolonged discharges of 1-5 s in duration. BD was significantly increased within 60 min and reached a maximum after 2-2.5 h of agonist exposure. The protein synthesis inhibitors anisomycin (15 microM) or cycloheximide (25 microM) significantly impeded the mGluR-mediated development of the prolonged bursts; 90-120 min of agonist application failed to elicit the expected burst prolongation. By contrast, the mGluR-mediated enhancement of burst frequency progressed unimpeded. Furthermore, protein synthesis inhibitors had no significant effect on the frequency or duration of fully developed mGluR-induced prolonged discharges. These results suggest that the group I mGluR-mediated prolongation of synchronized bursts has a protein synthesis-dependent mechanism. 相似文献
32.
LR Schover 《Canadian Metallurgical Quarterly》1998,65(6):331-332
33.
34.
LR Pisharodi 《Canadian Metallurgical Quarterly》1995,103(5):603-608
Basal cell adenocarcinoma of salivary gland is a relatively recently described neoplasm. Histopathologic features of these tumors have been published in the literature mainly in the form of case reports. This paper elaborates and describes the diagnostic fine-needle aspiration cytomorphology of two cases of basal cell adenocarcinoma of parotid gland, which, to the author's knowledge, has not been previously reported in the English literature. Fine-needle aspiration specimens in both cases contained cohesive, focally papillary, and filiform groups of neoplastic cells, which were highly reminiscent of basal cell adenoma on low power examination. Higher power, however, revealed significant cytologic atypia and mitotic activity. Differential diagnoses included basal cell adenoma, epithelial rich pleomorphic adenoma, myoepithelial lesions, small cell undifferentiated carcinoma, and metastatic carcinoma among others. 相似文献
35.
36.
37.
38.
OBJECTIVE: To describe the presentation and incidence of Kaposi's sarcoma (KS) in a cohort of women infected with HIV and to compare their clinical characteristics with men at the same institution. DESIGN: Retrospective chart and database review. SETTING: Adult clinical AIDS program outpatient clinics at a municipal teaching hospital. RESULTS: One hundred and seven people with KS were found of whom twelve (11.2%) were women. The prevalence of KS in women was 3.6% compared with 9.9% among men (P < 0.001). Women born outside the United States were at increased risk of developing KS (P < 0.05). At initial KS presentation, no difference in HIV stage or CD4 count was found between men and women. Women presented with more advanced KS than men, with increased incidence of non-cutaneous disease (P < 0.001), lymphedema (P < 0.0001), lymph-node disease (P < 0.0001) and visceral disease (P = 0.03). Women had decreased survival after KS diagnosis compared to men, although the difference was not significant (P = 0.41). CONCLUSIONS: KS is not a rare diagnosis in HIV-infected women followed at our institution. Although the increased risk of KS in men is most likely to be related to differences in exposure, the sex-related differences in presentation and course may be due in part to delay in diagnosis. KS should be considered in the spectrum of HIV-related complications in women as well as in men. 相似文献
39.
40.
KL Geris SP Kotanen LR Berghman ER Kühn VM Darras 《Canadian Metallurgical Quarterly》1996,104(2):139-146
New tools to prevent malaria morbidity and mortality are needed to improve child survival in sub-Saharan Africa. Insecticide treated bednets (ITBN) have been shown, in one setting (The Gambia, West Africa), to reduce childhood mortality. To assess the impact of ITBN on child survival under different epidemiological and cultural conditions we conducted a community randomized, controlled trial of permethrin treated bednets (0.5 g/m2) among a rural population on the Kenyan Coast. Between 1991 and 1993 continuous community-based demographic surveillance linked to hospital-based in-patient surveillance identified all mortality and severe malaria morbidity events during a 2-year period among a population of over 11000 children under 5 years of age. In July 1993, 28 randomly selected communities were issued ITBN, instructed in their use and the nets re-impregnated every 6 months. The remaining 28 communities served as contemporaneous controls for the following 2 years, during which continuous demographic and hospital surveillance was maintained until the end of July 1995. The introduction of ITBN led to significant reductions in childhood mortality (PE 33%, CI 7-51%) and severe, life-threatening malaria among children aged 1-59 months (PE 44%, CI 19-62). These findings confirm the value of ITBN in improving child survival and provide the first evidence of their specific role in reducing severe morbidity from malaria. 相似文献