全文获取类型
收费全文 | 4306篇 |
免费 | 51篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 25篇 |
综合类 | 1篇 |
化学工业 | 476篇 |
金属工艺 | 42篇 |
机械仪表 | 52篇 |
建筑科学 | 65篇 |
矿业工程 | 9篇 |
能源动力 | 76篇 |
轻工业 | 134篇 |
水利工程 | 13篇 |
石油天然气 | 19篇 |
无线电 | 212篇 |
一般工业技术 | 381篇 |
冶金工业 | 2502篇 |
原子能技术 | 27篇 |
自动化技术 | 326篇 |
出版年
2021年 | 45篇 |
2020年 | 31篇 |
2019年 | 31篇 |
2018年 | 32篇 |
2017年 | 32篇 |
2016年 | 21篇 |
2015年 | 29篇 |
2014年 | 48篇 |
2013年 | 82篇 |
2012年 | 65篇 |
2011年 | 65篇 |
2010年 | 65篇 |
2009年 | 63篇 |
2008年 | 80篇 |
2007年 | 78篇 |
2006年 | 71篇 |
2005年 | 60篇 |
2004年 | 59篇 |
2003年 | 69篇 |
2002年 | 47篇 |
2001年 | 60篇 |
2000年 | 53篇 |
1999年 | 106篇 |
1998年 | 672篇 |
1997年 | 425篇 |
1996年 | 325篇 |
1995年 | 191篇 |
1994年 | 173篇 |
1993年 | 164篇 |
1992年 | 45篇 |
1991年 | 68篇 |
1990年 | 63篇 |
1989年 | 52篇 |
1988年 | 61篇 |
1987年 | 47篇 |
1986年 | 42篇 |
1985年 | 69篇 |
1984年 | 35篇 |
1983年 | 26篇 |
1982年 | 41篇 |
1981年 | 38篇 |
1980年 | 34篇 |
1979年 | 25篇 |
1978年 | 27篇 |
1977年 | 95篇 |
1976年 | 134篇 |
1975年 | 20篇 |
1974年 | 22篇 |
1973年 | 18篇 |
1972年 | 17篇 |
排序方式: 共有4360条查询结果,搜索用时 9 毫秒
1.
Renal length has been measured by ultrasound in 237 subjects with homozygous sickle cell (SS) disease, 147 with sickle cell-hemoglobin C (SC) disease, and in 78 age-matched controls with a normal hemoglobin (AA) genotype. As expected, renal length increased with age in all genotypes but mean length was significantly greater in SS disease compared with SC disease (mean difference 4.3 mm after adjustment for height) and significantly greater in both genotypes than in AA controls (SS/AA difference 9.2 mm, SC/AA difference 5.0 mm after adjustment for height). Examination of relationships between renal length and some hematological indices (hemoglobin, fetal hemoglobin, reticulocyte counts, alpha thalassemia status) in SS or SC disease showed only a significant negative correlation with hemoglobin and positive correlation with reticulocyte count in SS disease. Further analysis suggested that the stronger relationship was between renal length and high reticulocyte count. The mechanism of renal enlargement is unknown although glomerular hypertrophy and increased renal blood volume are likely contributors. 相似文献
2.
Electron-beam or ultrafast computerized tomographic (CT) scanning provides a convenient and sensitive means of detecting coronary calcification, which is an early index of atherosclerosis. The procedure has strong negative predictive power for the presence of coronary artery disease, but a limited ability to predict disease severity. However, preliminary indications are that it is as good or better than conventional risk factors in this respect. Although further validation is needed before electron-beam CT can be regarded as an established method of detecting presymptomatic coronary atherosclerosis, the procedure has potential in this context. 相似文献
3.
4.
5.
The results of the thermal and catalytic reactions of lignin model compounds are used in the a priori prediction of its liquefaction. Lignin was defined probabilistically as an ensemble of single ring aromatics with substituents on each of their six ring positions. Elements in a substituent vector x1, for each ring position i, were matched into all possible combinations to describe lignin. Initial number fractions, or probabilities, for each vector element were ascertained through inspection of lignin structural data. The reaction of lignins altered the probabilities within each substituent vector, and reaction products were also calculated by matching all combinations of vector elements for each ring position. Model compound results provided the identities and rates of change of vector elements.
This simulation of lignin liquefaction predicted the yields of permanent gases, aqueous liquids, single- and two-ring phenolic products, and a carbonaceous residue. The impact of the distribution of oligomeric sizes on catalyst effectiveness was probed. 相似文献
This simulation of lignin liquefaction predicted the yields of permanent gases, aqueous liquids, single- and two-ring phenolic products, and a carbonaceous residue. The impact of the distribution of oligomeric sizes on catalyst effectiveness was probed. 相似文献
6.
N‐p‐Bromophenylmaleimide (BrPMI) does not polymerize in solution by conventional free radical mechanism. However, it readily polymerized in bulk when mixed with a free radical initiator and heated in a microwave oven for 7–8 min. Copolymerization of ethyl methacrylate or butyl methacrylate with BrPMI was conducted in dioxane. The copolymers were characterized by IR and 1H NMR spectroscopy and gel permeation chromatography. The monomer reactivity ratios were calculated by a non‐linear least‐square analysis. Thermal analysis indicated a great improvement in thermal stability of the copolymers compared with the methacrylate homopolymers. BrPMI was also polymerized in bulk in the DSC pan, which allowed the calculation of the activation energy of its polymerization. Copyright © 2003 Society of Chemical Industry 相似文献
7.
R Albrecht TC Awes C Baktash P Beckmann F Berger R Bock G Claesson G Clewing L Dragon A Eklund RL Ferguson A Franz S Garpman R Glasow HA Gustafsson HH Gutbrod J Idh P Jacobs K Kampert BW Kolb P Kristiansson IY Lee H Loehner I Lund FE Obenshain A Oskarsson I Otterlund T Peitzmann S Persson F Plasil AM Poskanzer M Purschke H Ritter S Saini R Santo HR Schmidt T Siemiarczuk SP Sorensen E Stenlund ML Tincknell GR Young 《Canadian Metallurgical Quarterly》1991,44(6):2736-2752
8.
GR McKee 《Canadian Metallurgical Quarterly》1995,76(2):427-434
Legal responsibility for acts presumes that a person's behavior is rationally intentional and under voluntary control. Automatism, a type of insanity defense, contends that the person's conscious, voluntary control of behavior has been impaired by a mental disorder. In a recent case in South Carolina, automatism was offered as a defense to adultery, an at-fault grounds to divorce. On appeal, the State Supreme Court recognized the novel application of mental impairment defenses in domestic litigation and remanded the case for rehearing. Implications of the ruling for clinical and forensic practice in family court are discussed. 相似文献
9.
Saksenaea vasiformis, a zygomycete belonging to the order Mucorales, is a rare cause of zygomycosis with 17 cases documented world-wide. It usually infects the immunocompromised or traumatized and has a high mortality rate. Because of its failure to sporulate under normal laboratory conditions it may be difficult to identify. We describe here an unusual case report of Saksenaea vasiformis with sporulation and identification within a week using a modified sporulation technique. 相似文献
10.