全文获取类型
收费全文 | 5602篇 |
免费 | 124篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 53篇 |
综合类 | 2篇 |
化学工业 | 989篇 |
金属工艺 | 100篇 |
机械仪表 | 91篇 |
建筑科学 | 230篇 |
矿业工程 | 26篇 |
能源动力 | 96篇 |
轻工业 | 464篇 |
水利工程 | 32篇 |
石油天然气 | 20篇 |
武器工业 | 1篇 |
无线电 | 436篇 |
一般工业技术 | 869篇 |
冶金工业 | 1509篇 |
原子能技术 | 60篇 |
自动化技术 | 753篇 |
出版年
2021年 | 52篇 |
2020年 | 42篇 |
2019年 | 53篇 |
2018年 | 44篇 |
2017年 | 54篇 |
2016年 | 68篇 |
2015年 | 59篇 |
2014年 | 104篇 |
2013年 | 287篇 |
2012年 | 164篇 |
2011年 | 208篇 |
2010年 | 185篇 |
2009年 | 207篇 |
2008年 | 242篇 |
2007年 | 237篇 |
2006年 | 210篇 |
2005年 | 164篇 |
2004年 | 165篇 |
2003年 | 128篇 |
2002年 | 144篇 |
2001年 | 110篇 |
2000年 | 104篇 |
1999年 | 118篇 |
1998年 | 200篇 |
1997年 | 154篇 |
1996年 | 130篇 |
1995年 | 131篇 |
1994年 | 104篇 |
1993年 | 107篇 |
1992年 | 113篇 |
1991年 | 49篇 |
1990年 | 79篇 |
1989年 | 76篇 |
1988年 | 83篇 |
1987年 | 80篇 |
1986年 | 82篇 |
1985年 | 103篇 |
1984年 | 101篇 |
1983年 | 90篇 |
1982年 | 95篇 |
1981年 | 84篇 |
1980年 | 51篇 |
1979年 | 69篇 |
1978年 | 69篇 |
1977年 | 66篇 |
1976年 | 76篇 |
1975年 | 67篇 |
1974年 | 45篇 |
1973年 | 49篇 |
1972年 | 38篇 |
排序方式: 共有5731条查询结果,搜索用时 15 毫秒
1.
Lihua Lou Weijie Yu Ronald J. Kendall Ernest Smith Seshadri S. Ramkumar 《应用聚合物科学杂志》2020,137(30):49213
A tensile properties testing study was conducted to understand the influence of thickness, cross-head speed (speed of testing), gauge length (GL; specimen test length), and sample shape on important tensile properties of polyvinyl alcohol (PVA) nanofiber webs. The effects of each testing parameter on load at break, extension at break, Young's modulus, and tensile stress–strain curve of PVA nanofiber webs are analyzed. The Welch two sample t-tests show the significant difference among tested data. Using interaction plots, two-way analysis of variance, and margin mean plots, the interaction effects among testing parameters have been analyzed. Of all the factors, cross-head speed, the interaction among GL, and sample thickness (GL: Thickness) and the interaction among GL, testing speed and sample thickness (GL: Speed: Thickness) have significant influence on the tensile properties of PVA nanofiber webs. Moreover, the hypothesized model of mechanism of tensile strain–stress curve of PVA nanofiber webs has been proposed. Based on the model, the tensile strain–stress curve can be split into three stages: linear elastic, partial break up, and complete breakage. This study will provide a better understanding of tensile testing parameters' effects and their interaction effects on the tensile properties of nanowebs. 相似文献
2.
3.
4.
Math1 is essential for genesis of cerebellar granule neurons 总被引:1,自引:0,他引:1
N Ben-Arie HJ Bellen DL Armstrong AE McCall PR Gordadze Q Guo MM Matzuk HY Zoghbi 《Canadian Metallurgical Quarterly》1997,390(6656):169-172
5.
Chris Gibbons Corrine Chaves Ronald B. Wilkes Mark N. Frolick 《Information Systems Management》1994,11(3):51-56
Information-based organizations are structured to function with as small and efficient a staff as possible. To this end, executives at The Promus Companies are using IT to spread decision-making authority and responsibility for customer satisfaction and customer service throughout the organization. 相似文献
6.
JC Posnick MD Wells JM Drake JR Buncic D Armstrong 《Canadian Metallurgical Quarterly》1993,19(5):260-266
Fibrous dysplasia is an abnormal fibroosseous process of bone of unknown cause. The incidence of skull involvement varies, painless enlargement being the most common presenting symptom. Change in vision is a rare but recognized finding. We report a 3-year-old boy with extreme fibrous dysplasia involving the skull base, who presented with blindness. He underwent exposure osteotomies of the frontal bones and orbits to provide access for skull base tumor removal. The orbital roofs were reconstructed with microplate-fixed cranial grafts. One and one half years after tumor excision followed by immediate reconstruction, the boy retains facial symmetry, and his ocular function has not deteriorated. 相似文献
7.
Ahn Jaeshin Stromsmoe Keith A. Lawson Ronald P. W. 《Industrial Electronics, IEEE Transactions on》1985,(4):405-409
A microprocessor-based system with 32 A/D, 24 D/A, and 16 ac load controllers, has been designed and built to monitor and control an ion beam thin-film deposition system. The A/D and D/A channels have electrical isolation of 7.5 kV between channels and between input and output. The microprocessor system keeps the ion beam deposition parameters stable for extended periods of operation and it is proposed as a means to greatly simplify switching from one deposition species to another to grow thin multilayer or alloy films. 相似文献
8.
A new and simple method of finite-element grid improvement is presented. The objective is to improve the accuracy of the analysis. The procedure is based on a minimization of the trace of the stiffness matrix. For a broad class of problems this minimization is seen to be equivalent to minimizing the potential energy. The method is illustrated with the classical tapered bar problem examined earlier by Prager and Masur. Identical results are obtained. 相似文献
9.
Hypothesized, on the basis of findings from several studies, that rejected children are more disruptive, aggressive, and socially inappropriate than are their classmates. Three groups of 39 rejected, 29 neglected, and 39 accepted children were randomly selected from 282 boys and 210 girls who were identified separately on the basis of sociometric scores for 492 children in Grades 3–6. The 3 groups were compared using multiple analysis of variance (MANOVA) on measures from 4 domains: peer behavioral attributions, teacher ratings, analog assertiveness task, and self-evaluation. Rejected Ss were clearly distinguished from their same-sex neglected and accepted classmates and were described by teachers and peers as aggressive, disruptive and inattentive. Neglected Ss were only marginally discriminable from same-sex accepted children. Neither neglected nor rejected Ss were differentiated from accepted Ss with respect to observed assertiveness and self-ratings of shyness, unhappiness, and feeling unaccepted. The results replicate previous findings for rejected children. Currently, there is not sufficient justification to consider the group of socially neglected children as a clinical category. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.