全文获取类型
收费全文 | 4233篇 |
免费 | 77篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 6篇 |
综合类 | 3篇 |
化学工业 | 281篇 |
金属工艺 | 18篇 |
机械仪表 | 30篇 |
建筑科学 | 42篇 |
矿业工程 | 8篇 |
能源动力 | 53篇 |
轻工业 | 135篇 |
水利工程 | 10篇 |
石油天然气 | 8篇 |
无线电 | 41篇 |
一般工业技术 | 118篇 |
冶金工业 | 3397篇 |
原子能技术 | 2篇 |
自动化技术 | 160篇 |
出版年
2024年 | 5篇 |
2023年 | 18篇 |
2022年 | 46篇 |
2021年 | 67篇 |
2020年 | 28篇 |
2019年 | 39篇 |
2018年 | 55篇 |
2017年 | 59篇 |
2016年 | 45篇 |
2015年 | 31篇 |
2014年 | 31篇 |
2013年 | 83篇 |
2012年 | 60篇 |
2011年 | 72篇 |
2010年 | 36篇 |
2009年 | 42篇 |
2008年 | 31篇 |
2007年 | 37篇 |
2006年 | 19篇 |
2005年 | 22篇 |
2004年 | 13篇 |
2003年 | 17篇 |
2002年 | 17篇 |
2001年 | 5篇 |
2000年 | 8篇 |
1999年 | 106篇 |
1998年 | 999篇 |
1997年 | 605篇 |
1996年 | 378篇 |
1995年 | 244篇 |
1994年 | 177篇 |
1993年 | 214篇 |
1992年 | 36篇 |
1991年 | 65篇 |
1990年 | 52篇 |
1989年 | 66篇 |
1988年 | 60篇 |
1987年 | 46篇 |
1986年 | 36篇 |
1985年 | 36篇 |
1983年 | 7篇 |
1982年 | 20篇 |
1981年 | 16篇 |
1980年 | 21篇 |
1979年 | 2篇 |
1978年 | 6篇 |
1977年 | 94篇 |
1976年 | 129篇 |
1975年 | 6篇 |
1955年 | 1篇 |
排序方式: 共有4312条查询结果,搜索用时 687 毫秒
81.
82.
83.
84.
85.
R Kapur BJ Spargo MS Chen JM Calvert AS Rudolph 《Canadian Metallurgical Quarterly》1996,33(4):205-216
A new method is described for producing biomedically relevant polymers with precisely defined micron scale surface texture in the x, y, and z planes. Patterned Si templates were fabricated using photolithography to create a relief pattern in photoresist with lateral dimensions as small as 1 micron. Electroless Ni was selectively deposited in the trenches of the patterned substrate. The Ni served as a resilient mask for transferring the patterns onto the Si substrate to depths of up to 8.5 microns by anisotropic reactive ion etching with a fluorine-based plasma. The 3-dimensional (3-D) textured silicon substrates were used as robust, reusable molds for pattern transfer onto poly (dimethyl siloxane), low density poly (ethylene), poly (L-lactide), and poly (glycolide) by either casting or injection molding. The fidelity of the pattern transfer from the silicon substrates to the polymers was 90 to 95% in all three planes for all polymers for more than 60 transfers from a single wafer, as determined by scanning electron microscopy and atomic force microscopy. Further, the 3-D textured polymers were selectively modified to coat proteins either in the trenches or on the mesas by capillary modification or selective coating techniques. These selectively patterned 3-D polymer substrates may be useful for a variety of biomaterial applications. 相似文献
86.
87.
88.
Ideas derived from the study of the process of crystallization may provide insights into molecular recognition in biological systems. Both processes exploit the cooperativity which arises from the formation of a large array of weak interactions. 相似文献
89.
Different intravascular ultrasound (IVUS) systems vary in their image presentation. The purpose of this study was to compare four IVUS systems in vitro to determine the accuracy of tissue characterization of atherosclerotic plaque compared with histology. Ninety-eight plaque segments from 23 formalin-fixed human iliac arteries were imaged in saline at room temperature with four different IVUS systems. To assess the accuracy of IVUS in describing plaque, three types of analysis were performed: (1) the ability to identify the presence and extent of lumen or plaque boundary; (2) sensitivity, specificity, and interobserver variability of IVUS in qualitatively identifying plaque components compared with histology; and (3) quantification of calcification. The synthetic aperture device had a lower sensitivity in identifying lumen and plaque boundaries (87%, 38% respectively) compared with other machines (96%-100%, 95%-100%). All three mechanically rotating systems had fair to good sensitivities for identifying calcification (57%-73%) or lipid filled areas (50%-83%). The sensitivity of discriminating fibrous tissue from fatty areas was low (39%-52%). The synthetic aperture system had a significantly lower sensitivity for identifying all three tissue types (4%-21%). There was significant interobserver variability (kappa value = 0.47-0.68) as well as machine to machine variability (kappa value = 0.52) for tissue characterization. Calcified areas were underestimated by System 1 (p < .05) and System 4 (p < .01) because of weaker echo reflections or poor image quality. There are significant differences in image representation among these four IVUS systems in the diagnosis of tissue components of complex atherosclerotic plaque. These variabilities should be considered when interpreting studies performed with different machines. 相似文献
90.
SB Levery MS Toledo E Suzuki ME Salyan S Hakomori AH Straus HK Takahashi 《Canadian Metallurgical Quarterly》1996,222(2):639-645
An acidic glycolipid (Band 1), purified from P. brasiliensis by a combination of ion exchange chromatography, HPLC, and HPTLC, was found to be reactive with sera of all patients with paracoccidioidomycosis (PCM). Monosaccharide analysis of Band 1 yielded mannose and galactose in a 2:1 ratio, while mild acid hydrolysis and mild periodate oxidation/NaB3H4 reduction indicated the presence of a terminal galactofuranose. Preliminary analysis of 1H-NMR and MS data suggests that the structure of the glycan is Galf beta 1-->6(Manp alpha 1-->3)Manp beta 1-->2Ins (Ins = myo-inositol). Removal of the galacto-furanose decreased by 60-80% the reactivity of sera from PCM patients with Band 1, suggesting that this residue is immunodominant. With the presumed absence of galactofuranose in mammalian hosts, compounds containing this residue may be useful targets for therapy of several parasitic and fungal diseases. 相似文献