全文获取类型
收费全文 | 403648篇 |
免费 | 4684篇 |
国内免费 | 1364篇 |
专业分类
电工技术 | 7565篇 |
综合类 | 316篇 |
化学工业 | 59809篇 |
金属工艺 | 16424篇 |
机械仪表 | 13488篇 |
建筑科学 | 8348篇 |
矿业工程 | 2154篇 |
能源动力 | 11522篇 |
轻工业 | 28450篇 |
水利工程 | 4266篇 |
石油天然气 | 7913篇 |
武器工业 | 17篇 |
无线电 | 49232篇 |
一般工业技术 | 82963篇 |
冶金工业 | 74954篇 |
原子能技术 | 9181篇 |
自动化技术 | 33094篇 |
出版年
2022年 | 2549篇 |
2021年 | 3883篇 |
2020年 | 2940篇 |
2019年 | 3801篇 |
2018年 | 6479篇 |
2017年 | 6474篇 |
2016年 | 6917篇 |
2015年 | 4316篇 |
2014年 | 7131篇 |
2013年 | 20021篇 |
2012年 | 11405篇 |
2011年 | 15259篇 |
2010年 | 12137篇 |
2009年 | 13707篇 |
2008年 | 14046篇 |
2007年 | 13810篇 |
2006年 | 12414篇 |
2005年 | 11111篇 |
2004年 | 10504篇 |
2003年 | 10416篇 |
2002年 | 9825篇 |
2001年 | 9732篇 |
2000年 | 9133篇 |
1999年 | 9520篇 |
1998年 | 24324篇 |
1997年 | 16707篇 |
1996年 | 12797篇 |
1995年 | 9516篇 |
1994年 | 8362篇 |
1993年 | 8379篇 |
1992年 | 6054篇 |
1991年 | 5694篇 |
1990年 | 5679篇 |
1989年 | 5317篇 |
1988年 | 5043篇 |
1987年 | 4419篇 |
1986年 | 4299篇 |
1985年 | 4812篇 |
1984年 | 4421篇 |
1983年 | 3994篇 |
1982年 | 3654篇 |
1981年 | 3730篇 |
1980年 | 3429篇 |
1979年 | 3326篇 |
1978年 | 3334篇 |
1977年 | 3750篇 |
1976年 | 4847篇 |
1975年 | 2850篇 |
1974年 | 2663篇 |
1973年 | 2730篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
961.
962.
Also with the Department of Agronomy. 相似文献
963.
964.
P Granone G Cardillo E Rumi D D'Ugo C Rumi S Ciletti S Margaritora D Terribile A Picciocchi 《Canadian Metallurgical Quarterly》1993,7(7):351-355
Fresh surgical specimens of tumors from 60 patients with previously untreated non-small cell lung carcinoma (NSCLC) who underwent radical surgery between January 1991 and October 1992 were investigated by means of flow-cytometry. The nuclear DNA measurement was carried out using a Facscan (Becton, Dickinson, USA). Analysis of the DNA content was performed in all 60 patients whilst cell cycle analysis was possible in 41 cases (68.3%). Forty-two of the 60 cases (70%) were aneuploid and 18 (30%) were diploid. The overall mean value of DNA index was 1.5. Diploid NSCLC were compared with aneuploid tumors: no significant differences in age distribution, sex ratio, histology and staging were found between the two groups (P > 0.05). An S-phase proportion of more than 10% was found in 30 out of 41 patients (73.2%). Early cancer deaths were reported in four patients (6.6%): the aneuploidy rate was very close in these patients (75%) and in the remaining surviving patients (69.6%). An S-phase proportion of more than 10% was found in 100% of early cancer deaths and in 70.2% of the remaining cases; such a difference seems of some importance although it was not statistically significant (P = 0.071). In conclusion, flow-cytometry studies seem to be a useful tool in the understanding of the biological behavior of patients with NSCLC. In the present prospective report there were no significant correlations between DNA measurements and clinical outcome, however, these results suggest that a high S-phase proportion should be seen as a possible prognostic indicator.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
965.
S Knecht M Deppe EB Ringelstein M Wirtz H Lohmann B Dr?ger T Huber H Henningsen 《Canadian Metallurgical Quarterly》1998,29(6):1155-1159
BACKGROUND AND PURPOSE: Since functional transcranial Doppler ultrasonography (fTCD) allows convenient and fully automated quantification of language lateralization, it seems ideal for longitudinal studies of perfusion changes during deterioration as well as recovery of language functions. However, during serial examinations, the technical, stochastic, and physiological variabilities of cerebral blood flow velocities (CBFV) have to be considered. Therefore, before fTCD is accepted as a tool for evaluation of changes in lateralization in the diseased state, its reliability in healthy subjects needs to be determined. METHODS: We performed fTCD during a word generation task based on a previously validated technique with automated calculation of the averaged CBFV differences in the middle cerebral arteries providing an index of lateralization (LI). RESULTS: (1) The accuracy of the LI as assessed by the confidence interval was better than 1% of the mean hemispheric difference. (2) On repeated examination, LIs obtained from 10 subjects showed a high test-retest reproducibility (Pearson product moment correlation coefficient r = 0.95, P < 0.0001). (3) On 10 repeated assessments of LI in the same subject, no practice effects were detected. CONCLUSIONS: Functional TCD is a suitable and very robust tool for the longitudinal quantitative measurement of cerebral language lateralization. 相似文献
966.
967.
968.
969.
A Matsumori Y Matoba R Nishio T Shioi K Ono S Sasayama 《Canadian Metallurgical Quarterly》1996,222(3):678-682
We investigated hepatitis C virus (HCV) infection in 35 patients with hypertrophic cardiomyopathy and 40 patients with ischemic heart disease who were consecutively admitted to our hospital. Frequency of positive anti-HCV antibody was significantly higher in patients with hypertrophic cardiomyopathy (6 of 35 patients, 17.1%) than that in patients with ischemic heart disease (1 of 40 patients, 2.5%, p = 0.036). In three of these six patients with hypertrophic cardiomyopathy, HCV RNA was detected in myocardial tissue. In two of these three patients, HCV RNA was detected from biopsy and autopsy specimens of the ventricles, but not in the serum, suggesting that HCV may replicate in myocardial tissue and may be relevant to ventricular hypertrophy. Thus, HCV infection may play a role in the development of hypertrophic cardiomyopathy. 相似文献
970.
JF Delaloye S Leyvraz E Outcha Adjahoto J Bauer P De Grandi 《Canadian Metallurgical Quarterly》1996,19(2):204-206
We report two cases of metastatic non-functioning pancreatic endocrine tumour with very elevated plasma levels of alpha-fetoprotein. In these two cases, serial plasma levels of alpha-fetoprotein, initially normal, correlated well with hepatic tumour progression and were associated with fatal outcome. These results suggest that elevated plasma concentration of alpha-fetoprotein may be caused by metastatic pancreatic endocrine tumour and than alpha-fetoprotein serial measurement may be useful in prognostic evaluation. 相似文献