全文获取类型
收费全文 | 287828篇 |
免费 | 3531篇 |
国内免费 | 811篇 |
专业分类
电工技术 | 5034篇 |
综合类 | 163篇 |
化学工业 | 45448篇 |
金属工艺 | 11903篇 |
机械仪表 | 8625篇 |
建筑科学 | 6879篇 |
矿业工程 | 1833篇 |
能源动力 | 6746篇 |
轻工业 | 25945篇 |
水利工程 | 3191篇 |
石油天然气 | 7086篇 |
武器工业 | 16篇 |
无线电 | 31509篇 |
一般工业技术 | 57023篇 |
冶金工业 | 51708篇 |
原子能技术 | 7537篇 |
自动化技术 | 21524篇 |
出版年
2021年 | 2099篇 |
2018年 | 3676篇 |
2017年 | 3628篇 |
2016年 | 3910篇 |
2015年 | 2468篇 |
2014年 | 4235篇 |
2013年 | 12045篇 |
2012年 | 6839篇 |
2011年 | 9230篇 |
2010年 | 7583篇 |
2009年 | 8663篇 |
2008年 | 8957篇 |
2007年 | 8852篇 |
2006年 | 7863篇 |
2005年 | 7347篇 |
2004年 | 6828篇 |
2003年 | 6573篇 |
2002年 | 6647篇 |
2001年 | 6512篇 |
2000年 | 6201篇 |
1999年 | 6246篇 |
1998年 | 14827篇 |
1997年 | 11092篇 |
1996年 | 8612篇 |
1995年 | 6545篇 |
1994年 | 5933篇 |
1993年 | 5802篇 |
1992年 | 4492篇 |
1991年 | 4442篇 |
1990年 | 4298篇 |
1989年 | 4310篇 |
1988年 | 4269篇 |
1987年 | 3607篇 |
1986年 | 3603篇 |
1985年 | 4174篇 |
1984年 | 3981篇 |
1983年 | 3641篇 |
1982年 | 3434篇 |
1981年 | 3584篇 |
1980年 | 3445篇 |
1979年 | 3383篇 |
1978年 | 3452篇 |
1977年 | 3929篇 |
1976年 | 5052篇 |
1975年 | 3169篇 |
1974年 | 3011篇 |
1973年 | 3036篇 |
1972年 | 2654篇 |
1971年 | 2480篇 |
1970年 | 2106篇 |
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
991.
992.
L Bini B Magi B Marzocchi F Arcuri S Tripodi M Cintorino JC Sanchez S Frutiger G Hughes V Pallini DF Hochstrasser P Tosi 《Canadian Metallurgical Quarterly》1997,18(15):2832-2841
Reference two-dimensional (2-D) gels are presented for human breast ductal carcinoma and histologically normal tissue. Whole biopsy fragments were analyzed, including epithelial and nonepithelial components. Thirty-five spots have been assigned by gel matching to the human liver SWISS-2DPAGE reference map and/or to the human primary keratinocyte IPG map from the Danish Center for Human Genome. N-terminal microsequencing was applied to confirm randomly chosen matching assignments and to identify six new spots. Protein expression profiles in ductal carcinoma and in normal breast tissue appeared to be similar, except for a pattern consisting of 32 spots, which were highly expressed in all carcinoma specimens, and less intense and occasionally undetectable in normal tissue. This difference was statistically significant. Assignment has been obtained for several spots, namely GRP94, GRP78, GRP75, mitochondrial HSP60, calreticulin, protein disulfide isomerase, peptidyl-prolyl cis-trans isomerase, collagen-binding protein 2, fructose bisphosphate aldolase, glyceraldehyde-3-phosphate dehydrogenase, thioredoxin, cytochrome c oxidase VA subunit, tubulin beta isoform and macrophage migration inhibitory factor (MIF). The cancer- and tissue-specificity of the described pattern was assessed by matching to the Swiss-2DPAGE human liver, hepatoma, lymphoma, erythroleukemia reference maps. The pattern of 32 spots was found to be indicative of epithelial neoplasia. 相似文献
993.
DK Bhuyan X Huang G Kuriakose WH Garner KC Bhuyan 《Canadian Metallurgical Quarterly》1997,16(6):519-526
This article takes issue with procedural reductionism, which is the inclination to reduce all matters of judgement and responsibility to the following of some procedure or rule. Two scenarios provide content for a discussion of professional discretion in the context of accountability. The author shows that in professional life there will always be situations that stand beyond the rules of procedures and require the unique judgement of the professional at the time. While this judgement may be determined by the facts available in a situation of uncertainty, it cannot be reduced to the facts (including facts about rules and procedures). The moral judgement will still have an essential indeterminancy about it. 相似文献
994.
995.
In the last decades, the classification of schemes of haematological malignancies have undergone considerable changes both in terms of modifications of previous concepts and of methodological approaches, in parallel with the acquisition of new information on the physiopathological and functional pattern of haemic cells and of their precursors both at the lymph node and bone marrow level. The cyto-morphological aspects of haemic were better defined and integrated by the application of cyto- and histochemical methods, which were subsequently supplemented by bioenzymatic and cytogenetic techniques, then by immunophenotypical studies and finally by biomolecular investigations. Through the use of monoclonal antibodies and the introduction both in research and routine diagnostic practice of multiparameter analysis techniques, it is now possible to correlate several cellular parameters, to identify clonality of malignant cells as well as their lineage assignment and maturation stage. Flow cytometry has become an important, rapid and objective method for the diagnosis of haematological neoplasias. In the present survey we have illustrated the different expression of surface, cytoplasmic and nuclear antigens in haematological malignancies, their correlation with the clinical course of the disease and their diagnostic and prognostic significance. 相似文献
996.
Candelier P. Mondon F. Guillaumot B. Reimbold G. Martin F. 《Electron Device Letters, IEEE》1997,18(7):306-308
A simplified flash EEPROM process was developed using high-temperature LPCVD oxide both as flash cells interpoly dielectrics and as peripheral transistors gate oxide (decoding logic). An O2 anneal at 850°C lowers charge trapping and interface trap density induced by Fowler-Nordheim injection. However, electron trapping remains slightly higher than with dry thermal oxide. Similar memory charge loss and write-erase endurance are obtained as for ONO-insulated cells. HTO thus proves to have the required quality and reliability to be used in flash EEPROMs 相似文献
997.
Fracture mechanics of oilseed rape pods 总被引:2,自引:0,他引:2
The basic theory of linear elastic fracture mechanics was applied to the fracture of pods from six genetic lines of oilseed
rape (Brassica napus). An experiment was designed to allow the energetics of the fracture process to be accurately determined.
The work of fracture, toughness and fracture toughness of five experimental varieties and one common commercial variety (Apex)
were measured. The values for the toughness (0.006–0.271 kJ m-2) and fracture toughness (0.026–0.233 MN m-3/2) obtained from
each line were distinct from each other but broadly similar to those of other brittle materials. The toughness and fracture
toughness of Apex were approximately midway between the lowest and highest values measured. This result indicates that there
is scope for improving the fracture resistance of oilseed rape crops so as to reduce seed loss before and during harvest.
The approach described would be useful in selecting fracture-resistant genetic lines to help to develop such crops.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
998.
999.
1000.
Few studies have prospectively examined the characteristics associated with worksite adoption of tobacco-control initiatives. Data were collected as part of the Community Intervention Trial (COMMIT) for Smoking Cessation, which conducted interventions in 11 communities. This smoking cessation intervention was based on community organization principles and delivered through multiple community channels, including worksites, health care providers, the media, and cessation resources. This article reports results from telephone interviews of intervention community worksites having 50 or more employees, conducted at baseline and the end of the intervention period. Among worksites that responded to both baseline and final surveys, 83% had not adopted a smoke-free policy at baseline, and 61% did not offer any cessation aid or quitting resources at baseline. By the final survey, 34% of those with no smoking ban at baseline had become smoke-free, and 36% of those offering no cessation assistance at baseline were offering cessation resources at the follow-up. The prevalence of policy adoption was higher among worksites employing more female employees and offering other health-promotion activities; manufacturing businesses were significantly less likely than businesses other than service and wholesale/retail businesses to adopt policies. Adoption of cessation programs was significantly more likely among worksites employing 100 to 249 workers, compared with those employing 50 to 99 workers; those predominantly employing men; those offering other types of health-promotion activities; and those with a higher rate of turnover. These results provide important information about the characteristics of worksites likely to engage in tobacco-control efforts. Health educators and others may choose to target those worksites most ready for adoption of tobacco control policies and programs, as indicated by these findings. 相似文献