全文获取类型
收费全文 | 831篇 |
免费 | 17篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 17篇 |
综合类 | 2篇 |
化学工业 | 207篇 |
金属工艺 | 22篇 |
机械仪表 | 23篇 |
建筑科学 | 29篇 |
能源动力 | 25篇 |
轻工业 | 52篇 |
水利工程 | 3篇 |
无线电 | 106篇 |
一般工业技术 | 169篇 |
冶金工业 | 70篇 |
原子能技术 | 3篇 |
自动化技术 | 123篇 |
出版年
2022年 | 14篇 |
2021年 | 26篇 |
2020年 | 21篇 |
2019年 | 18篇 |
2018年 | 24篇 |
2017年 | 20篇 |
2016年 | 14篇 |
2015年 | 14篇 |
2014年 | 16篇 |
2013年 | 63篇 |
2012年 | 20篇 |
2011年 | 31篇 |
2010年 | 20篇 |
2009年 | 28篇 |
2008年 | 39篇 |
2007年 | 26篇 |
2006年 | 26篇 |
2005年 | 25篇 |
2004年 | 22篇 |
2003年 | 15篇 |
2002年 | 16篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 21篇 |
1997年 | 22篇 |
1996年 | 13篇 |
1995年 | 13篇 |
1994年 | 9篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1991年 | 11篇 |
1990年 | 13篇 |
1989年 | 8篇 |
1988年 | 16篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 8篇 |
1984年 | 16篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1981年 | 9篇 |
1980年 | 12篇 |
1979年 | 14篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 19篇 |
1975年 | 12篇 |
1974年 | 8篇 |
1971年 | 8篇 |
1970年 | 5篇 |
排序方式: 共有851条查询结果,搜索用时 15 毫秒
91.
The purpose of this project was to develop a rugged and efficient solar lantern. The lantern was designed to meet the requirements of persons who reside in areas in which access to the electrical grid is limited and whose resources do not permit import of electrical generation capabilities. A representative of a missionary organization operating in Africa developed the original set of specifications for the solar lantern. It will be used by the local school children for doing homework in the evening. These specifications prioritized reliability, ease of operation, rugged construction, portability, and low cost. The resulting design was realized in a single prototype. The design and construction of the prototype was completed as a student/faculty project in the Junior Engineering Clinic course at Rowan University in Glassboro, NJ. It was funded and directed by ETM Solar Works, a New York-based corporation. 相似文献
92.
In Vitro Antiamoebic Activity Evaluation and Docking Studies of Metronidazole–Triazole Hybrids
下载免费PDF全文
![点击此处可从《ChemMedChem》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Beena Negi Dr. K. Kranthi Raj Shadab Miyan Siddiqui Dr. Dittakavi Ramachandran Dr. Amir Azam Prof. Diwan S. Rawat 《ChemMedChem》2014,9(11):2439-2444
An in‐house database of 520 compounds was docked against Entamoeba histolytica thioredoxin reductase (EhTrR), a promising target for the treatment of amoebiasis. Amongst these, some metronidazole (MTZ)–triazole hybrids were ranked high, with docking scores from ?10.23 to ?7.56. Studies of the binding orientations and conformations show that the head groups of MTZ–triazole hybrids interact with the arginine residues within the binding pocket of EhTrR, making it clear that such is the optimal and most reliable orientation for this class of compounds. The top‐ten MTZ–triazole hybrids were then selected for evaluation of their activity against the HM1:IMSS strain of amoeba. The most active compound, 2‐pyridyl‐(1,2,3‐triazolyl)metronidazole 10 , with an IC50 value of 8.4 nM , was significantly more active than the standard drug MTZ alone. Docking studies revealed that compound 10 may act as an EhTrR inhibitor with activity in the nanomolar range and satisfactory ADME properties; it is a suitable candidate to be carried forward as a potential lead in the discovery of drugs to combat amoebiasis. 相似文献
93.
Blaszczyk-Thurin Magdalena; Murali Ramachandran; Westerink M.A.Julie; Steplewski Zenon; Co Man Sung; Kieber-Emmons Thomas 《Protein engineering, design & selection : PEDS》1996,9(5):447-459
The murine monoclonal antibody BR55-2 is directed against thetumor-associated antigen Lewis Y oligosaccharide. The LewisY core antigen is a difucosylated structure consisting of fourhexose units. Analysis of binding profiles of lactoseries isomericstructures by BR552 suggest that the binding epitopeincludes the OH-4 and OH-3 groups of the ß-D-galactoseunit, the 6-CH3 groups of the two fucose units and the N-acetylgroup of the subterminal ß-D-N-acetylglucosamine (ßDGlcNAc).To elucidate the molecular recognition properties of BR552for the Y antigen, BR552 was cloned, sequenced and itsthree-dimensional structure was examined by molecular modeling.The crystal structure of BR96, another anti-Lewis Y antibody,solved in complex with a nonoate methyl ester Lewis Y tetrasaccharide,and the lectin IV protein in complex with a Lewis b tetrasaccharidecore were used as a guide to probe the molecular basis for BR552antigen recognition and specificity. Our modeling study showsthat BR552 shares similar recognition features for thedifucosylated type 2 lactoseries Lewis Y structure observedin the BR96-sugar complex. We observe that a major source ofspecificity for the Lewis Y structure by anti-Y antibodies emanatesfrom interaction with the ß-D-N-acetylglucosamineresidue and the nature of the structures extended at the reducingsite of the fucosylated lactosoamine. 相似文献
94.
95.
Yezdezard Lashkari Viswanath Ramachandran Sanjay Malpani S. L. Mehndiratta 《Software》1993,23(7):799-811
With the increasing proliferation of computer networks and distributed systems, there is a growing number of applications using multicast communication. This paper presents the Vartalaap system developed at IIT, Bombay. Vartalaap is an hierarchical distributed system for multicast communication over a network, implemented in a hardware-independent fashion. The multicast is achieved without resorting to unnecessary broadcasting of messages over the network. Issues covered in this paper include the primitives for multicast, the multicast model and the system architecture. We discuss the implementation of Vartalaap and compare it with some other systems. We conclude with a discussion on the limitations of the current implementation and directions for future work. 相似文献
96.
Bolam R.J. Ramachandran V. Coolbaugh D. Watson K.M. 《Electron Devices, IEEE Transactions on》2003,50(4):941-944
In this paper, we discuss the electrical characteristics and reliability of UV transparent Si/sub 3/N/sub 4/ metal-insulator-metal (MIM) capacitors. We examine film thicknesses in the range of 55 to 25 nm with capacitance densities from 1.2 ff//spl mu/m/sup 2/ to 2.8 ff//spl mu/m/sup 2/, respectively, for single MIM capacitors. A new approach for projecting the dielectric reliability of these films extends the limits of maximum operating voltage. Accounting for temperature acceleration and area scaling, the projected lifetimes can be met for a wide range of operating conditions. 相似文献
97.
S. Ramachandran M.F. Yan E. Monberg F.V. Dimarcello P. Wisk S. Ghalmi 《Photonics Technology Letters, IEEE》2003,15(11):1561-1563
We demonstrate resonant grating couplers with the broadest bandwidth (565 nm) reported to date, using microbend gratings in dispersion-optimized few-mode fibers. Control of modal dispersion enables the demonstration of spectrally flat (< 0.25-dB ripple) coupling. This enables a compact (1 cm), broad-band (110 nm) variable optical attenuator, which is highly cost-effective, since device assembly simply involves pressing an as-drawn fiber between two corrugated blocks. 相似文献
98.
Chen E. Ramachandran Qi Zhao Arlette Zikanova Milan Kocirik Linda J. Broadbelt Randall Q. Snurr 《Catalysis communications》2006,7(12):936-940
PFG NMR diffusion measurements were carried out to determine the effect of solvent on intracrystalline reactant diffusivities and on 1-hexene epoxidation rates in TS-1 catalyst. Using n-hexane in silicalite as a mimic for the TS-1 system, the self-diffusivity of n-hexane in silicalite was found to be 24% higher in methanol solvent than in acetonitrile solvent and 45% higher than in acetone solvent. The presence of trace Al did not affect n-hexane diffusivity. Based on analysis of the Weisz modulus for a slab morphology, the 1-hexene epoxidation reaction in TS-1 was found to be diffusion limited only if the crystal size is at least 38 μm in the methanol system. 相似文献
99.
U Kapil N Saxena S Ramachandran TD Sharma D Nayar 《Canadian Metallurgical Quarterly》1997,34(4):338-340
Using polymerase chain reaction single strand conformational polymorphism (PCR-SSCP) and EB staining technique, paraffin-embeded sections of 20 hydatidiform mole and 4 choriocarcinoma were detected in the exons 5 and 8 of p53 gene. The results showed that mutations of p53 gene were 0/9 in the normal chorionic villi, 6/20 (30%) in hydatidiform mole and 3/4 in choriocarcinoma. This study suggests that mutations of p53 gene may be an important event in human gestational trophoblastic neoplastigenesis and its progression. 相似文献
100.
Jaimohan Ramachandran David Rubenstein Danny Bluestein Jolyon Jesty 《Nicotine & tobacco research》2004,6(5):835-841
Mainstream and sidestream smoke extracts of both high-tar and low-tar cigarettes have been shown to increase platelet activation directly and to sensitize them to further activation by exposure to mechanical stimuli such as shear stress. However, nicotine has an inhibitory effect on platelet activation, opposite to that of whole cigarette smoke extracts. To distinguish between the nicotine-dependent and non-nicotine-dependent effects of smoke, platelets were exposed to mainstream and sidestream smoke extracts of low-nicotine and zero-nicotine cigarettes in vitro under flow conditions comparable with the normal circulation, and their activation state was measured using a modified prothrombinase-based assay. Both low-nicotine and zero-nicotine extracts caused increased platelet activation upon exposure to shear stress, and they caused significantly greater activation than extracts from ordinary high-tar, high-nicotine cigarettes. That nicotine was crucial was confirmed by adding 50 nM nicotine (comparable with the nicotine level in smokers' plasma) to zero-nicotine smoke extracts and demonstrating a reduction in the shear-dependent rate of platelet activation of more than 75%. 相似文献