全文获取类型
收费全文 | 1446篇 |
免费 | 26篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 115篇 |
金属工艺 | 5篇 |
机械仪表 | 12篇 |
建筑科学 | 4篇 |
能源动力 | 14篇 |
轻工业 | 109篇 |
水利工程 | 5篇 |
石油天然气 | 7篇 |
无线电 | 46篇 |
一般工业技术 | 49篇 |
冶金工业 | 1085篇 |
原子能技术 | 2篇 |
自动化技术 | 18篇 |
出版年
2024年 | 3篇 |
2022年 | 12篇 |
2021年 | 23篇 |
2020年 | 13篇 |
2019年 | 20篇 |
2018年 | 28篇 |
2017年 | 11篇 |
2016年 | 11篇 |
2015年 | 9篇 |
2014年 | 20篇 |
2013年 | 38篇 |
2012年 | 19篇 |
2011年 | 28篇 |
2010年 | 19篇 |
2009年 | 22篇 |
2008年 | 16篇 |
2007年 | 11篇 |
2006年 | 12篇 |
2005年 | 10篇 |
2004年 | 11篇 |
2003年 | 7篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 35篇 |
1998年 | 325篇 |
1997年 | 217篇 |
1996年 | 119篇 |
1995年 | 54篇 |
1994年 | 64篇 |
1993年 | 64篇 |
1992年 | 17篇 |
1991年 | 8篇 |
1990年 | 17篇 |
1989年 | 12篇 |
1988年 | 20篇 |
1987年 | 19篇 |
1986年 | 8篇 |
1985年 | 11篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1981年 | 3篇 |
1980年 | 12篇 |
1978年 | 5篇 |
1977年 | 26篇 |
1976年 | 72篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1965年 | 1篇 |
1929年 | 1篇 |
排序方式: 共有1472条查询结果,搜索用时 15 毫秒
71.
72.
Colitis cystica profunda is a benign disease of the colon. Its importance lies in differentiating it from mucus-producing adenocarcinoma. It has rarely been described in the surgical literature. A review of records of patients seen at the Mayo Clinic produced 66 clinical cases of localized colitis cystica profunda, and in 21 patients the diagnosis was confirmed histologically. Follow-up, which was available in all patients, ranged from 2 months to 29 years, with a mean follow-up of more than 8 years. The data suggest that local excision is the preferred initial therapy. 相似文献
73.
Moraes JE Quina FH Nascimento CA Silva DN Chiavone-Filho O 《Environmental science & technology》2004,38(4):1183-1187
The application of the photo-Fenton process to the treatment of saline wastewater contaminated with hydrocarbons is investigated. Aqueous saline solutions containing raw gasoline were used as a model oil-field-produced water. The dependence on concentrations of the following reagents has been appropriately evaluated: hydrogen peroxide (100-200 mM), iron ions (0.5-1 mM), and sodium chloride (200-2000 ppm). The reactions were monitored by measurement of the absorption spectra and total organic carbon (TOC). Experimental results demonstrate that the photo-Fenton process is feasible for the treatment of wastewaters containing hydrocarbons, even in the presence of high concentrations of salt. The effect of the salt in this process is described through a series of reactions. A simple feedforward neural network model was found to correlate well the observed data for the degradation process. 相似文献
74.
A comparison of the effects of left stellate ganglion stimulation (SGS) on central and aortic hemodynamics has been made in chloralose-anesthetized mongrel (M), and greyhound (GH) dogs. Measurements of aortic pressure and flow, and left ventricular pressure were made during stimulation of the decentralized left SG at different frequencies from 0 to 20 Hz. The increases in aortic pressure and flow with SGS were larger in the GH, especially for low frequencies of stimulation. Stroke volume was increased with SGS in the GH at all stimulation rates, whereas in the M it was unchanged. A greater decrease in left ventricular end-diastolic pressure with SGS was found in the GH. These results suggest that differences exist in both the intrinsic and extrinsic control of cardiac output in the greyhound dog compared to the mongrel. These differences may be in part responsible for the elevated arterial blood pressure in the greyhound compared to the mongrel. 相似文献
75.
We report the 14th case of myelolipoma of the adrenal gland. Recommendations for appropriate diagnostic and therapeutic methods are made. Myelolipoma of the adrenal gland is a rare non-functioning tumor composed of lipoid and hematopoietic elements. The most consistent complaint is abdominal pain caused by hemorrhage within the tumor. We identified an association with obesity and hypertension. Ultrasound combined with computed tomography is useful in diagnosis. With expanded use of these studies, myelolipoma will be recognized more frequently. Definitive diagnosis and treatment are accomplished by simple excision; radical surgery is unnecessary. 相似文献
76.
Felipe de Lucia Lobo Evlyn Márcia Leão de Moraes Novo Claudio Clemente Faria Barbosa Lênio Soares Galvão 《International journal of remote sensing》2013,34(11):3422-3442
Reference spectra extracted from spectral libraries can distinguish different water types in images when associated with limnological information. In this study, we compiled available databases into a single spectral library, using field water reflectance spectra and limnological data collected by different researchers and campaigns in the Amazonian region. By using an iterative clustering procedure based on the combination of reflectance and optically active components (OACs), reference spectra representative of the major Amazonian water types were defined from this library. Differences between the resultant limnological classes were also evaluated by paired t-tests at significance level 0.05. Finally, reference spectra were tested for Spectral Angle Mapper (SAM) classification of waters in Hyperion/Earth Observing-One (EO-1) and Medium Resolution Imaging Spectrometer (MERIS)/Environment Satellite (Envisat) images acquired simultaneously as the field campaigns. Results showed highly variable concentrations of OACs due to the complexity of the Amazonian aquatic environments. Ten classes were defined to represent this complexity, broadly grouped into four limnological characteristics: clear waters with low concentrations of OACs (class 1); black waters rich in dissolved organic carbon (DOC) (class 2); waters with large concentrations of inorganic suspended solids (ISSs) (classes 3–7); and waters dominated by chlorophyll-a (chl-a) (classes 8–10). Using the ten reference spectra, SAM classification of the field water curves produced an overall accuracy of 86% with the highest values observed for classes 3, 4, 6 and 7 and the lowest accuracy for classes 1 and 2. The results of paired t-tests confirmed the class differences based on the concentrations of OACs. SAM classification of the Hyperion and MERIS images using ground truth information resulted in overall classification accuracies of 48% and 67%, respectively, with the highest errors associated with specific portions of the scenes that were not adequately represented in the spectral library. 相似文献
77.
78.
79.
80.