全文获取类型
收费全文 | 45913篇 |
免费 | 3819篇 |
国内免费 | 1912篇 |
专业分类
电工技术 | 2456篇 |
技术理论 | 3篇 |
综合类 | 2680篇 |
化学工业 | 6577篇 |
金属工艺 | 2197篇 |
机械仪表 | 2418篇 |
建筑科学 | 2966篇 |
矿业工程 | 1134篇 |
能源动力 | 1118篇 |
轻工业 | 2638篇 |
水利工程 | 773篇 |
石油天然气 | 2509篇 |
武器工业 | 379篇 |
无线电 | 4902篇 |
一般工业技术 | 4750篇 |
冶金工业 | 7584篇 |
原子能技术 | 404篇 |
自动化技术 | 6156篇 |
出版年
2024年 | 240篇 |
2023年 | 827篇 |
2022年 | 1511篇 |
2021年 | 2056篇 |
2020年 | 1523篇 |
2019年 | 1149篇 |
2018年 | 1365篇 |
2017年 | 1426篇 |
2016年 | 1178篇 |
2015年 | 1670篇 |
2014年 | 2156篇 |
2013年 | 2410篇 |
2012年 | 2723篇 |
2011年 | 2941篇 |
2010年 | 2614篇 |
2009年 | 2179篇 |
2008年 | 2318篇 |
2007年 | 2078篇 |
2006年 | 2010篇 |
2005年 | 1744篇 |
2004年 | 1141篇 |
2003年 | 971篇 |
2002年 | 928篇 |
2001年 | 803篇 |
2000年 | 800篇 |
1999年 | 1145篇 |
1998年 | 2669篇 |
1997年 | 1687篇 |
1996年 | 1265篇 |
1995年 | 846篇 |
1994年 | 664篇 |
1993年 | 616篇 |
1992年 | 279篇 |
1991年 | 216篇 |
1990年 | 181篇 |
1989年 | 143篇 |
1988年 | 122篇 |
1987年 | 90篇 |
1986年 | 82篇 |
1985年 | 81篇 |
1984年 | 32篇 |
1983年 | 37篇 |
1982年 | 42篇 |
1981年 | 59篇 |
1980年 | 75篇 |
1978年 | 26篇 |
1977年 | 140篇 |
1976年 | 299篇 |
1975年 | 20篇 |
1973年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
采用电子表格软件EXCEL5.0可以方便地解决许多选煤生产中的线性规划问题。本文通过选煤过程线性规划实例介绍EXCEL5.0在此领域的应用方法。 相似文献
32.
E Ashihara AM Vannucchi G Migliaccio AR Migliaccio 《Canadian Metallurgical Quarterly》1997,171(3):343-356
The Word Accentuation Test assesses the accentuation of 30 infrequent Spanish words written without the accentuation mark and is an easy-to-use tool for estimating premorbid intelligence of Spanish-speaking people. Its intraobserver (0.97) and interobserver (0.93) reliabilities and its correlation with the Wechsler Adult Intelligence Scale (.837) and Raven's Progressive Matrices (.655) are high, offering a good prediction of general intelligence. It is resistant to mental deterioration; 20 demented and 40 controls matched by sex, age, and education obtained similar scores. The discrepancies between current and predicted scores in Raven's scale can diagnose mild-moderate dementia with 0.79 accuracy (sensitivity, 0.78; specificity, 0.82). 相似文献
33.
本文研究短程透镜的焦点位于端面外的球差特性。对焦点位于波导外部(包括端面)的情况给出了一种精确测量焦距新方法,采用这种方法简单易行,测量精度取决于读数显微镜的读数精度(0.01mm)。 相似文献
34.
35.
The data of nine children with post-traumatic intramural haematoma of the duodenum treated in Aghia Sophia Children's Hospital of Athens from 1967 to 1980 were retrospectively analysed. Diagnosis was preoperative in all but two children, in whom diagnosis was made during laparotomy. All but one were managed by operative intervention which consisted of simple evacuation of the haematoma and closure of the serosal incision in two out of eight children. Six out of eight children operated on were followed up for 15 years, during which they were free of symptoms. Hypotonic duodenography performed in the above patients was negative for deformity or stricture of the duodenum. 相似文献
36.
37.
IuP Spizhenko AV Biliaiev AM Zaremba IV Nahorny? AP Tkachenko 《Canadian Metallurgical Quarterly》1997,43(5-6):42-48
Investigated all links of oxygen homeostasis of patients in early period afterwards surgical stoppage gastro-intestinal bleeding and urgent intravascular volume replacement. Macrodelivery of oxygen (DO2) was reduced in two and more time in comparison with norm predominant in connection with anemia. In spite of the infringement of transport of oxygen through alveolar-capillary membrane (especially in patients with complications and death in early postoperative period), little affected of degree of hemoglobin saturation by oxygen. Despite decrease of erythrocyte zeta-potential, largely expressed in cases of lethal outcome, considerable infringement of passage through microcirculation vessels is fixed was not. The increase of degree of morbidity and anaerobic metabolism in early postoperative period was accompanied of hyperdynamic hemodynamic reaction. The increase of degree of morbidity was accompanied of increase oxygen deficit owing to infringement of oxidoreduction in fabries also. 相似文献
38.
AM Luciani S Di Capua L Guidoni R Ragona A Rosi V Viti 《Canadian Metallurgical Quarterly》1996,41(3):509-521
NMR relaxation times T1 and T2 of agarose and Fricke agarose gels have been measured in the range 17-51 MHz. The analysis of the spin echo curves indicates a multiexponential behaviour, characterized by three components, at all the examined frequencies. The relative T2 values, ranging from a few to a hundred milliseconds, can be attributed to different species of water molecules present in the gel. Two of these components are characterized by relaxation rates R2a and R2b, more sensitive than R1 to gamma irradiation, the sensitivity S being S(R1) = 0.066 s-1 Gy-1, S(R2a) = 0.088 s-1 Gy-1, S(R2b) = 0.17 s-1 Gy-1. The three T2 values decrease as a function of frequency, but no gain in dose sensitivity is obtained by changing the working frequency in the examined range. The relaxivity of agarose gels containing ferrous or ferric ions has also been measured and found to be different from those of the corresponding solutions in the absence of agarose. Thus it was possible to estimate the irradiation yield from three independent parameters, R1, R2a and R2b. No effect of the dose rate or of the source energy has been observed for any of these parameters. 相似文献
39.
40.
Z. -G. Fan Y. -X. Zhuang G. Yang R. Shao G. -F. Zhang 《Journal of Alloys and Compounds》1993,200(1-2):33-36
The oxygen absorption process in highly aligned YBa2Cu3Ox samples in air and in pure oxygen was studied at several constant temperatures. The process can be expressed in two steps, a chemical reaction controlled step and a diffusion controlled step. The kinetic equations are as follows respectively:
(1 − at) ln(1 − at) + at = kDt
The activation energy was calculated using an Arrhenius equation. The technical conditions of heat treatment for oxygen absorption of highly aligned YBa2Cu3Ox crystals are discussed. 相似文献