全文获取类型
收费全文 | 1518篇 |
免费 | 37篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 12篇 |
综合类 | 3篇 |
化学工业 | 123篇 |
金属工艺 | 16篇 |
机械仪表 | 11篇 |
建筑科学 | 31篇 |
矿业工程 | 1篇 |
能源动力 | 19篇 |
轻工业 | 48篇 |
石油天然气 | 3篇 |
无线电 | 160篇 |
一般工业技术 | 181篇 |
冶金工业 | 796篇 |
原子能技术 | 2篇 |
自动化技术 | 153篇 |
出版年
2023年 | 4篇 |
2022年 | 9篇 |
2021年 | 6篇 |
2020年 | 11篇 |
2019年 | 13篇 |
2018年 | 16篇 |
2017年 | 10篇 |
2016年 | 9篇 |
2015年 | 7篇 |
2014年 | 19篇 |
2013年 | 45篇 |
2012年 | 22篇 |
2011年 | 31篇 |
2010年 | 17篇 |
2009年 | 45篇 |
2008年 | 44篇 |
2007年 | 46篇 |
2006年 | 38篇 |
2005年 | 37篇 |
2004年 | 38篇 |
2003年 | 40篇 |
2002年 | 35篇 |
2001年 | 30篇 |
2000年 | 30篇 |
1999年 | 49篇 |
1998年 | 272篇 |
1997年 | 144篇 |
1996年 | 110篇 |
1995年 | 57篇 |
1994年 | 44篇 |
1993年 | 67篇 |
1992年 | 20篇 |
1991年 | 19篇 |
1990年 | 15篇 |
1989年 | 18篇 |
1988年 | 13篇 |
1987年 | 20篇 |
1986年 | 16篇 |
1985年 | 18篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 11篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1977年 | 16篇 |
1976年 | 20篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有1559条查询结果,搜索用时 375 毫秒
1.
Evaluation and optimization of package processing and design through solder joint profile prediction 总被引:1,自引:0,他引:1
Solder joints are generated using a variety of methods to provide both mechanical and electrical connection for applications such as flip-chip, wafer level packaging, fine pitch, ball-grid array, and chip scale packages. Solder joint shape prediction has been incorporated as a key tool to aid in process development, wafer level and package level design and development, assembly, and reliability enhancement. This work demonstrates the application of an analytical model and the Surface Evolver software in analyzing a variety of solder processing methods and package types. Bump and joint shape prediction was conducted for the design of wafer level bumping, flip-chip assembly, and wafer level packaging. The results from the prediction methodologies are validated with experimentally measured geometries at each level of design. 相似文献
2.
P. K. Yeung S. C. Kot 《International journal for numerical methods in engineering》1985,21(5):929-939
A body-fitted curvilinear co-ordinate system is used to solve the equations of two-dimensional incompressible laminar flow over bluff obstructions by finite differences. Arbitrary conditions at the corner are removed by this method. Results for a backward-facing step are in reasonable agreement with those obtained with conventional mesh systems, and the differences are explained. A treatment of a channel expansion, in comparison with empirical data, is also included. The capability of the present method to handle arbitrary two-dimensional geometries is stressed and demonstrated, using a triangle and a semi-circle as examples. 相似文献
3.
Four experiments investigated the effect of recent selective practice on the cost of switching between 2 tasks afforded by letter-digit pairs: alphabet arithmetic and shape comparison. Experiments 1 and 2 found a greater cost associated with switching to the more recently practiced task: evidence that task-set inertia contributes to switching costs. Experiment 3 found this effect to be limited to trials on which a recently trained stimulus followed another such stimulus: a result problematic for all current theories of task-set priming. Experiment 4 showed that the effect of recent practice was eliminated by active preparation for a task switch: It appears that endogenous task-set preparation reduces the effects of task-set inertia. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
4.
The ability of oral lactobacilli to coaggregate with streptococci and actinomycetes was investigated. Of the 7 species of lactobacilli studied, only two were capable of coaggregation and the coaggregation was restricted to streptococci. Lactobacillus salivarius strains (2/4) coaggregated with Streptococcus salivarius, Streptococcus gordonii, Streptococcus crista and tufted Streptococcus sanguis II strains. Lactobacillus fermentum (2/3) coaggregated with S. gordonii and S. sanguis. The coaggregation between L. salivarius and S. salivarius, S. gordonii or tufted S. sanguis II strains was mediated by a protein on the surface of the lactobacilli and was not inhibited by lactose. The coaggregation between L. fermentum and the streptococci was mediated by protein on the surface of the streptococci and was inhibited by lactose. 相似文献
5.
A novel monoclonal antibody to 6 beta-hydroxycortisol (6 beta-OHC) was generated and incorporated into an antigen-coated indirect enzyme-linked immunosorbent assay (ELISA) using 6 beta-OHC-protein conjugate as the steroid-coating antigen. The monoclonal antibody is specific to 6 beta-OHC and 6 beta-OHC-3-carboxymethyloxime. Cross-reactivity with other structurally related steroids such as cortisol, cortisone, and 6 beta-hydroxycortisone was less than 10%. Two different clones (clone 5C1 and 19F) of the monoclonal anti-6 beta-OHC antibody have been developed, each with slightly different sensitivity and specificity. The sensitivity of the MAb clones was not significantly improved when compared to the rabbit polyclonal antibodies in this study, but still within the accepted detection limit for 6 beta-OHC in both human and laboratory animals. The assay had a detection limit of 200 ng/ml, an intraassay variation of 6.4% and an interassay variation of 7.3%. The application of the anti-6 beta-OHC-MAb-based-ELISA was tested by measuring the urinary output of 6 beta-OHC in human before and after enzyme induction by rifampicin treatment. The mean 24-h urine output of 6 beta-OHC in human subjects was 485 +/- 100 micrograms and 1478 +/- 281 micrograms before and after rifampicin administration, respectively. In conclusion, the monoclonal anti-6 beta-OHC antibody developed in this study has the required specificity and sensitivity as an alternative method for measuring urinary 6 beta-OHC in the detection of enzyme induction or enzyme inhibition of CYP3A in humans and laboratory animals. 相似文献
6.
7.
8.
LG Westergaard PE Rasmussen S Maigaard HJ Ingerslev AN Andersen JF Larsen J Starup PJ Hornnes CY Andersen 《Canadian Metallurgical Quarterly》1993,155(33):2511-2514
Medical indications for in vitro fertilization and embryo transfer (IVF-ET) internationally and in Denmark are reviewed. Reports from large international centres document that tubal infertility, unexplained infertility, endometriosis and male infertility are equally good indications for IVF. Traditionally, tubal infertility has been the only medical indication qualifying for IVF treatment within the National Health Service in Denmark. Thus, in this country, couples with unexplained and male infertility and with endometriosis have to pay up to 25,000 D.Kr. per IVF-ET treatment in private fertility clinics. Since there is no scientific basis for this discrimination, it is urged that the present rules are changed, so that couples with unexplained and male infertility and endometriosis are also allowed IVF treatment free of charge in the public fertility clinics. 相似文献
9.
10.
It has been reported that it is harder to switch to a strong, well-practiced task from a weaker, less-practiced task than vice versa. Three experiments replicated this surprising asymmetry and investigated how it is affected by a reduction in interference between tasks. Experiment 1 progressively delayed the onset of the stimulus attribute associated with the stronger task. Experiments 2 and 3 separated the response sets of the tasks. Both manipulations reduced, without eliminating, interference of the stronger with the weaker task but reversed the asymmetry of switch costs, resulting in a larger cost of switching to the weaker task. The results are interpreted in terms of a model of the interactions between control input, task strength, and task priming. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献