全文获取类型
收费全文 | 1879篇 |
免费 | 96篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 14篇 |
化学工业 | 444篇 |
金属工艺 | 31篇 |
机械仪表 | 53篇 |
建筑科学 | 39篇 |
矿业工程 | 3篇 |
能源动力 | 79篇 |
轻工业 | 260篇 |
水利工程 | 19篇 |
石油天然气 | 17篇 |
无线电 | 62篇 |
一般工业技术 | 220篇 |
冶金工业 | 473篇 |
原子能技术 | 8篇 |
自动化技术 | 254篇 |
出版年
2024年 | 14篇 |
2023年 | 21篇 |
2022年 | 38篇 |
2021年 | 86篇 |
2020年 | 65篇 |
2019年 | 76篇 |
2018年 | 71篇 |
2017年 | 60篇 |
2016年 | 74篇 |
2015年 | 46篇 |
2014年 | 68篇 |
2013年 | 130篇 |
2012年 | 86篇 |
2011年 | 103篇 |
2010年 | 101篇 |
2009年 | 106篇 |
2008年 | 58篇 |
2007年 | 64篇 |
2006年 | 37篇 |
2005年 | 25篇 |
2004年 | 27篇 |
2003年 | 27篇 |
2002年 | 23篇 |
2001年 | 12篇 |
2000年 | 15篇 |
1999年 | 18篇 |
1998年 | 131篇 |
1997年 | 93篇 |
1996年 | 61篇 |
1995年 | 35篇 |
1994年 | 31篇 |
1993年 | 24篇 |
1992年 | 14篇 |
1991年 | 6篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 18篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 7篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 20篇 |
1976年 | 30篇 |
1961年 | 1篇 |
排序方式: 共有1976条查询结果,搜索用时 15 毫秒
101.
IV Bychkovskaia RP Stepanov PV Antonov DN Cherniakova 《Canadian Metallurgical Quarterly》1996,36(6):926-931
Electron microscopic investigation of capillary endothelium cells in myocardium of irradiated rats revealed an unusual effect of persistent increase of probability of cell damage, similar in many relations to that described earlier for various unicellular species. New effect, unlike those traditionally studied, is characterised by non-stochastic nature, large number of the involved cells, reveals itself even after faint influences, and can be induced as well by agents other than radiation. The question is put on the probable commonness between these changes and the pseudomutagenesis which has the similar phenomenology. 相似文献
102.
AV Demin AV Kolesnikov MA Olfer'ev PV Favorov KV Fegeding AG Gabibov NV Gnuchev 《Canadian Metallurgical Quarterly》1998,34(10):1333-1337
A new system for the expression of a catalytic light chain antibody to the vasoactive intestinal peptide is described. The system made possible the isolation the large amounts of a homogeneous protein without any additional peptide domains. The preparation obtained can be used in further experiments on light chain crystallization and in X-ray-structural analysis of its catalytic center. 相似文献
103.
In computer graphics we use techniques from different areas of mathematics. Mathematical models are used to simulate real-world objects, as well as natural phenomena. In order to understand these models and pose relevant problems in each particular field of this area, it is important to create levels of abstraction. These levels encapsulate common properties of the different models and allow us to have a global, conceptual view of the methods and techniques in each field. In this paper we study a paradigm for creating abstraction levels that can also be used to characterize more general problems in computational applied mathematics. We apply this paradigm to different areas of computer graphics: modeling, animation, illumination, color theory, image processing and human-computer interface. 相似文献
104.
TB Lovelace JT Mellonig RM Meffert AA Jones PV Nummikoski DL Cochran 《Canadian Metallurgical Quarterly》1998,69(9):1027-1035
The purpose of this study was to compare the use of bioactive glass to demineralized freeze-dried bone allograft (DFDBA) in the treatment of human periodontal osseous defects. Fifteen systemically healthy patients (6 males and 9 females, aged 30 to 63) with moderate to advanced adult periodontitis were selected for the study. All patients underwent initial therapy, which included scaling and root planing, oral hygiene instruction, and an occlusal adjustment when indicated, followed by re-evaluation 4 to 6 weeks later. Paired osseous defects in each subject were randomly selected to receive grafts of bioactive glass or DFDBA. Both soft and hard tissue measurements were taken the day of surgery (baseline) and at the 6-month re-entry surgery. The clinical examiner was calibrated and blinded to the surgical procedures, while the surgeon was masked to the clinical measurements. Statistical analysis was performed by using the paired Student's t test. The results indicated that probing depths were reduced by 3.07 +/- 0.80 mm with the bioactive glass and 2.60 +/- 1.40 mm with DFDBA. Sites grafted with bioactive glass resulted in 2.27 +/- 0.88 mm attachment level gain, while sites grafted with DFDBA had a 1.93 +/- 1.33 mm gain in attachment. Bioactive glass sites displayed 0.53 +/- 0.64 mm of crestal resorption and 2.73 mm bone fill. DFDBA-grafted sites experienced 0.80 +/- 0.56 mm of crestal resorption and 2.80 mm defect fill. The use of bioactive glass resulted in 61.8% bone fill and 73.33% defect resolution. DFDBA-grafted defects showed similar results, with 62.5% bone fill and 80.87% defect resolution. Both treatments provided soft and hard tissue improvements when compared to baseline (P < or = 0.0001). No statistical difference was found when comparing bioactive glass to DFDBA; however, studies with larger sample sizes may reveal true differences between the materials. This study suggests that bioactive glass is capable of producing results in the short term (6 months) similar to that of DFDBA when used in moderate to deep intrabony periodontal defects. 相似文献
105.
The catecholamine hypothesis of progressive spinal cord necrosis following mechanical trauma was investigated with the histofluorometric method. Forty-four adult mongrel dog were examined as control, L1 crush-injured, and crush-injured with prior T1 total transection groups. In crush injured dogs, catecholamines were present in a 1 cm length of white matter at the crush site, with the greatest accumulation in the deep lateral and ventral funiculi. Gray matter fluorescence was not enhanced. Prior transection did not abolish the intense accumulation of catecholamines at the site of the cord injury. We propose that the catecholamines accumulating at the cord injured site are not central in origin, but represent an uptake mechanism into white matter as a reflection of cord microperfusion. 相似文献
106.
107.
Maternal lymphocyte reactivity to human trophoblast antigens was studied in placentas of gestational ages 8 to 14 weeks and 32 to 34 weeks, respectively. Significant trophoblast lysis became apparent after 24 hours' incubation in the latter case compared with a time lag of 72 hours in the terminated gestations. Maternal cellular immunity, therefore, was not detected during the first 3 1/2 months of pregnancy, but was detectable by the time of parturition. The possible significance is discussed with respect to the antigenic stimulus and survival of the fetal allograft. 相似文献
108.
Economic time series are of two types: stock and flows, and may be available at different levels of aggregation (for instance,
monthly or quarterly). The economist, in many situations, is interested in forecasting the aggregated observations. The forecast
function, in this case, can be based either on the disaggregated series or the aggregated series. The forecasts based on the
disaggregated data are at least as efficient, in terms of mean squared forecast errors, as the forecasts based on temporally
aggregated observations when the data generating process (DGP) is a known ARIMA process. However, the effect of outliers on
both forecast functions is not known. In this paper, we consider the effect of additive and innovation outliers on forecasting
aggregated values based on aggregated and disaggregated models when the DGP is a known ARIMA process and the presence of the
outliers is ignored. Results when the model is not known and tests applied for the detection of outliers are derived through
simulation. 相似文献
109.
Raul A. Feijoo Luiz Bevilacqua 《International journal for numerical methods in engineering》1976,10(1):133-143
In the present paper it is shown how to achieve special interpolation functions that can be applied to the finite element method, least squares methods or other related numerical techniques. We call these functions sequential interpolation functions since one of the main characteristics of this technique refers to the fact that the refinement of the solution does not require the redefinition of the interpolation funtions used in a previous step, as the case for instance in the FEM. The present theory and the FEM using an isoparametric element were compared for a plane stress problem. The results show that both have the same degree of accuracy. The choice of the sequential interpolation functions is easier than those used in the finite element formulation and the computer time was reduced by about 50 per cent. 相似文献
110.
Cledja Rolim Alejandro C. Frery Eliana Almeida Evandro Costa Luiz Marcos Gonçalves 《The Visual computer》2007,23(6):409-418
In this work we propose a new approach for fast visualization and exploration of virtual worlds based on the use of cartographic
concepts and techniques. Versions of cartographic maps with different levels of details can be created by using a set of operations
named cartographic generalization. Cartographic generalization employs twelve operators and domain-specific knowledge, being the contribution of this work their
transposition to 3D virtual worlds. The architecture of a system for 3D generalization is proposed and the system is implemented.
Differently from traditional cartographic processes, we use artificial intelligence for both selecting the key objects and
applying the operators. As a case study, we present the simplification of the historical quarter of Recife (Brazil). 相似文献