全文获取类型
收费全文 | 410211篇 |
免费 | 5083篇 |
国内免费 | 1604篇 |
专业分类
电工技术 | 7904篇 |
综合类 | 665篇 |
化学工业 | 60910篇 |
金属工艺 | 16802篇 |
机械仪表 | 13815篇 |
建筑科学 | 8822篇 |
矿业工程 | 2279篇 |
能源动力 | 11752篇 |
轻工业 | 28857篇 |
水利工程 | 4350篇 |
石油天然气 | 8170篇 |
武器工业 | 54篇 |
无线电 | 50051篇 |
一般工业技术 | 83918篇 |
冶金工业 | 75371篇 |
原子能技术 | 9258篇 |
自动化技术 | 33920篇 |
出版年
2022年 | 2688篇 |
2021年 | 4105篇 |
2020年 | 3122篇 |
2019年 | 3971篇 |
2018年 | 6619篇 |
2017年 | 6646篇 |
2016年 | 7082篇 |
2015年 | 4486篇 |
2014年 | 7384篇 |
2013年 | 20397篇 |
2012年 | 11719篇 |
2011年 | 15653篇 |
2010年 | 12472篇 |
2009年 | 14030篇 |
2008年 | 14391篇 |
2007年 | 14148篇 |
2006年 | 12767篇 |
2005年 | 11424篇 |
2004年 | 10732篇 |
2003年 | 10641篇 |
2002年 | 10009篇 |
2001年 | 9915篇 |
2000年 | 9282篇 |
1999年 | 9719篇 |
1998年 | 24508篇 |
1997年 | 16849篇 |
1996年 | 12933篇 |
1995年 | 9636篇 |
1994年 | 8458篇 |
1993年 | 8492篇 |
1992年 | 6127篇 |
1991年 | 5757篇 |
1990年 | 5732篇 |
1989年 | 5371篇 |
1988年 | 5082篇 |
1987年 | 4441篇 |
1986年 | 4327篇 |
1985年 | 4826篇 |
1984年 | 4429篇 |
1983年 | 4004篇 |
1982年 | 3664篇 |
1981年 | 3738篇 |
1980年 | 3435篇 |
1979年 | 3332篇 |
1978年 | 3339篇 |
1977年 | 3751篇 |
1976年 | 4856篇 |
1975年 | 2856篇 |
1974年 | 2665篇 |
1973年 | 2731篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
931.
G Zanetta S Chiari S Rota G Bratina A Maneo V Torri C Mangioni 《Canadian Metallurgical Quarterly》1997,104(9):1030-1035
OBJECTIVE: To assess the results of a policy of tailored conservative surgical management for young women with stage I ovarian carcinomas. DESIGN: Retrospective study. PARTICIPANTS: Ninety-nine women aged 40 years or younger who underwent either primary surgery in our department or were referred after primary surgery performed elsewhere. METHODS: Of the 99 women in our study, 56 underwent fertility-sparing surgery and 43 more radical surgery. Minimal requirements for conservative management were adequate staging and complete information about the therapeutic options. Factors important in the choice of the treatment were, age, wish to preserve fertility, histologic type and grade, and the stage of the tumour. RESULTS: Conservative treatment was conducted in 84% of nulliparous and in 33% of parous women; 62% of grade 1 tumours, 48% of grade 2, and 50% of grade 3 were treated conservatively. With a median follow up of seven years, we observed five recurrences (9%) of carcinoma in women treated conservatively and five (12%) in those treated more radically. Two women (one in each treatment arm) were saved after recurrence. Two recurrences after conservative surgery involved the residual ovary (3.6%). Two women developed borderline tumour in the contralateral ovary and both were treated by surgery. CONCLUSION: After adequate staging and accurate information is given to the patient, conservative treatment may be safe in some women with early ovarian cancer. The risk of recurrence in the contralateral ovary is low. Conservative surgery may be also considered in some Stage I grade 3 tumours and in some women with stage JC tumours. 相似文献
932.
To model effectively the output waveform and propagation delay of a CMOS gate, knowledge of the time point at which it starts to conduct is essential. An efficient method for calculating analytically this time point taking into account the structure of the gate and the input waveform, is introduced. Such a method can easily be integrated into a timing analysis system 相似文献
933.
P Sallagoity F Gaillard M Rivoire M Paoli M Haond S McClathie 《Microelectronics Reliability》1998,38(2):700
This paper presents Shallow Trench Isolation (STI) process steps for sub-1/4 μ CMOS technologies. Dummy active areas, vertical trench sidewalls, excellent gap filling, counter mask etch step and CMP end point detection, have been used for a 0.18 μm CMOS technology. Electrical results obtained with a 5.5 nm gate oxide thickness show good isolation down to 0.3 μm spacing. Good transistor performances have been demonstrated. 相似文献
934.
F F?ndrich AM Waaga J Schr?der E Schweizer A Schmid S Jacob HH Wacker P Schroeder 《Canadian Metallurgical Quarterly》1995,27(2):1553-1554
935.
Cortical bone remodeling rates for rib samples from three archaeological populations and a modern autopsy sample were determined using an algorithm developed by Frost (Frost [1987a] Calcif. Tissue Res. 3:211-237). When plotted against the relative antiquities for population samples, histomorphometric variables; i.e., activation frequency (mu rc), net bone formation (netVf,r,t), and mean annual bone formation rate (Vf,r,t), exhibit a concordant trend of increased cortical bone remodeling activity levels over time. Two intensive foraging populations, Windover and Gibson, are similar for all bone remodeling parameters and have the lowest remodeling activity levels among the samples. The more recent Ledders sample, which is reported to practice agricultural subsistence, is consistently intermediate between these and a modern autopsy sample. Although there appear to be differences in bone formation rates among the populations it is concluded that these differences cannot be attributed to differences in bone remodeling rates among the populations, but rather are reflecting different effective ages of adult compacta for their ribs. These findings suggest that the earlier populations, particularly Windsor and Gibson, appear to have reached skeletal maturity at an older age than observed for modern. 相似文献
936.
H Iai S Goto M Yamagata T Tamaki H Moriya K Takahashi M Mimura 《Canadian Metallurgical Quarterly》1994,19(3):272-276
Rheumatoid arthritis frequently contributes to instability of the upper cervical spine. Rotational instability of the upper cervical spine was evaluated in rheumatoid arthritis patients using biplanar x-ray photogrammetry. Three-dimensional cervical motion and the instantaneous axis of rotation of the atlas relative to the axis were evaluated in normal and rheumatoid arthritis patients during axial rotation in the horizontal plane. Anterior atlantoaxial subluxation did not increase during axial head rotation in either the atlantoaxial subluxation or the vertical subluxation groups, while the instantaneous axes of rotation were distributed posteriorly in the dens in the RA-normal group, but were widely scattered in the atlantoaxial subluxation group. 相似文献
937.
PN Hawkins S Richardson DM Vigushin J David CR Kelsey RE Gray MA Hall P Woo JP Lavender MB Pepys 《Canadian Metallurgical Quarterly》1993,36(6):842-851
OBJECTIVE: To evaluate aspects of the natural history of AA amyloidosis complicating juvenile rheumatoid arthritis (JRA), and its response to therapy with chlorambucil. METHODS: Scintigraphy and 7-day turnover studies were performed in JRA patients with histologically proven (n = 35) or clinically suspected (n = 30) AA amyloidosis, following intravenous injection of 123I and 125I-labeled serum amyloid P component (SAP). Prospective monitoring studies were performed over 2-3 years in 20 patients with amyloidosis. All but 2 amyloidosis patients were treated with chlorambucil. RESULTS: Positive scanning results were obtained in all patients in whom imaging was performed within 12 years of positive biopsy findings of amyloid and in 5 patients with clinically suspected amyloidosis. Negative scanning results with normal SAP metabolism, indicating regression of amyloid, were obtained in 4 patients whose amyloidosis had been in full clinical remission for more than 12 years. Prospective monitoring studies in patients whose JRA-associated inflammatory activity was in remission demonstrated regression of amyloid in 8 patients and no substantial changes in 8 others; however, in 4 further patients with active inflammation, there was accumulation of amyloid. There was a very poor correlation between the amount of amyloid present at a particular site and the resultant organ dysfunction. CONCLUSION: Radiolabeled SAP scintigraphy and turnover studies are useful complementary tools in the diagnosis, screening, and quantitative monitoring of type AA amyloidosis in JRA. The amyloid deposits may progress and/or regress at different rates in different anatomic sites over short periods. 相似文献
938.
939.
940.