全文获取类型
收费全文 | 12837篇 |
免费 | 402篇 |
国内免费 | 58篇 |
专业分类
电工技术 | 260篇 |
综合类 | 16篇 |
化学工业 | 2279篇 |
金属工艺 | 367篇 |
机械仪表 | 362篇 |
建筑科学 | 219篇 |
矿业工程 | 73篇 |
能源动力 | 707篇 |
轻工业 | 1177篇 |
水利工程 | 190篇 |
石油天然气 | 82篇 |
无线电 | 1630篇 |
一般工业技术 | 2777篇 |
冶金工业 | 1545篇 |
原子能技术 | 198篇 |
自动化技术 | 1415篇 |
出版年
2024年 | 39篇 |
2023年 | 177篇 |
2022年 | 505篇 |
2021年 | 506篇 |
2020年 | 411篇 |
2019年 | 410篇 |
2018年 | 559篇 |
2017年 | 514篇 |
2016年 | 486篇 |
2015年 | 284篇 |
2014年 | 447篇 |
2013年 | 888篇 |
2012年 | 520篇 |
2011年 | 678篇 |
2010年 | 540篇 |
2009年 | 531篇 |
2008年 | 477篇 |
2007年 | 390篇 |
2006年 | 332篇 |
2005年 | 263篇 |
2004年 | 245篇 |
2003年 | 221篇 |
2002年 | 180篇 |
2001年 | 145篇 |
2000年 | 147篇 |
1999年 | 156篇 |
1998年 | 355篇 |
1997年 | 231篇 |
1996年 | 251篇 |
1995年 | 219篇 |
1994年 | 183篇 |
1993年 | 171篇 |
1992年 | 143篇 |
1991年 | 151篇 |
1990年 | 115篇 |
1989年 | 108篇 |
1988年 | 130篇 |
1987年 | 109篇 |
1986年 | 89篇 |
1985年 | 115篇 |
1984年 | 94篇 |
1983年 | 107篇 |
1982年 | 99篇 |
1981年 | 88篇 |
1980年 | 78篇 |
1979年 | 54篇 |
1978年 | 46篇 |
1977年 | 56篇 |
1976年 | 76篇 |
1975年 | 32篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
J. Singh 《Drug development and industrial pharmacy》1986,12(6):851-866
Glibenclamide has limited gastrointestinal absorption. Therefore, different concentrations of sodium lauryl sulphate and tweenR80 were included into the tablet formulations to increase the absorption of the drug and hence, to enhance the BSL lowering in rabbits and human volunteers suffering from maturity onset diabetes mellitus. It was found that the surfactants had enhanced both the rate and extent of BSL lowering in rabbits as well as in diabetic patients in higher concentrations present in the tablet formulations. 相似文献
52.
Narendra Singh Shah & Nirankar Nath 《International Journal of Food Science & Technology》2006,41(9):1073-1081
Litchi (Litchi chinensis Sonn.) fruits are very susceptible to pericarp browning which adversely affects consumer acceptability even though the aril portion remains in excellent condition. Litchi arils (litchis) were treated with a solution containing 0–2% (w/v) calcium lactate (CL), 0–0.02% (w/v) 4‐hexyl resorcinol (4‐HR) and 1% potassium sorbate. The pH of solution was adjusted to 4.0 with citric acid. Treated litchis were packed in polystyrene trays, over‐wrapped with polypropylene film, vacuum‐packed (0, 47409.3, 94831.9 Pa) and stored at 4 ± 2 °C. Drip losses, pH, total soluble solids (TSS), sensory attributes and microbiological quality of stored samples were estimated. A four‐factor, three‐level experimental design (D6 Hokes design) with 19 experiments was chosen. Mathematical models were developed to analyse and predict the effect of CL, 4‐HR, in‐package vacuum and storage time on the responses. TSS, pH and sensory scores decreased significantly (P 0.01), whereas drip losses and microbial count increased significantly (P 0.01) with time. Drip loss was significantly (P 0.1) reduced by addition of CL. 4‐HR prevented browning and changes in colour score during storage were significantly less. Vacuum in packages exerted significant (P 0.01) effect over pH, TSS, sensory and microbiological qualities of minimally processed litchis. 相似文献
53.
The degradation behaviour of Kodar [poly(1,4-cyclohexylene dimethyl-eneterephthalate)] was investigated in air using thermogravimetry, differential thermal analysis and wide angle X-ray diffraction studies. The rates of crystallization and degradation were influenced by thermal exposure and polychromatic irradiation (Λ > 290 nm) for different time intervals. The crystallinity changes (Xc%) and activation energies (ΔE) for the systems have been determined. 相似文献
54.
1,3,5‐Triglyceratetriazine [first tier (G1)] and tri(1,3,5‐triglycerate) triazine [second tier (G2)] dendrimers were prepared with 1,3,5‐trichlorotriazine and sodium glycerate in a 1 : 3 mass ratio in an ethanolic medium.G1 and G2 were amorphous, white, solid substances. Their structures were elucidated with IR, 1H‐NMR, and 13C‐NMR, and their thermal stability was studied with thermogravimetric analysis. The activation energy was calculated with the Freeman–Carroll model. Densities, viscosities, and surface tensions for 0.01–0.08 mol/kg aqueous solutions increased at 0.01 mol/kg for sodium glycerate, 1,3,5‐trichlorotriazine, 1,3,5‐triazine triglycerate chloride, G1, and G2. These values were measured at 298.15 K. The apparent molal volume, reduced viscosity, and inherent viscosity were calculated from the densities and viscosities, respectively. The data were regressed for the limiting densities, limiting apparent molal volumes, intrinsic viscosities, limiting inherent viscosities, and limiting surface tensions for solute–solvent interactions. The positive limiting apparent molal volume values were noted in the order of G2 > 1,3,5‐triazine triglycerate chloride > G1 > 1,3,5‐trichlorotriazine > sodium glycerate, with weaker hydrophilic intermolecular interactions of G2. The higher intrinsic viscosity and limiting inherent viscosity values for G2 implied stronger G2–H2O hydrophilic interactions, and the higher limiting apparent molal volume of G2 indicated slightly higher dynamic conformational changes in comparison with G1, with stronger structural activities. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
55.
Instrumental characterization of clay by XRF,XRD and FTIR 总被引:2,自引:0,他引:2
Instrumental characterizations of the clay were performed by different techniques such as XRF, XRD and FTIR. XRF shows the
chemical compositions of the clay where Al-oxide and silica oxide are present in major quantity whereas XRD confirms the presence
of these minerals in clay. FTIR studies show the presence of quartz, alumina, haematite and different mineral matters. 相似文献
56.
C. D. Singh S. K. Dhua M. Kumar A. K. Jha T. Mrinal K. Sharma R. R. Abhyuday Y. Kumar 《Journal of Failure Analysis and Prevention》2007,7(4):292-301
A concentric reducer tube, which was a part of the top exit roughing hydraulic descaler in a hot strip mill failed prematurely
under working pressure. A detailed metallurgical investigation comprising physical examination, optical microscopy, scanning
electron microscopy, and electron probe microanalysis was carried out to find out the genesis of the failure. Physical examination
revealed cracks located symmetrically around the circumference of the tube that ran along its full length, up to the weld
beads at both ends. Optical microscopy of etched samples revealed a banded ferrite-pearlite structure and the existence of
forging folds near the change-in-section(160° fillets). Cracks were found to initiate from these forging folds. No structural
abnormalities were found in the weld beads and heat-affected zones. 相似文献
57.
RB Singh H Mori J Chen S Mendis M Moshiri S Zhu SH Kim RG Sy AM Faruqui 《Canadian Metallurgical Quarterly》1996,3(6):489-494
PURPOSE: Two types of glass wool were used to remove leukocytes in semen for evaluation of reactive oxygen species production by spermatozoa in oligozoospermic patients with leukocytospermia. METHODS: Semen samples were prepared using fine-structure glass wool (SpermFertil) and coarse-structure glass wool. In each treatment group, native semen was evaluated for sperm concentration, percentage motility, viability, leukocyte concentration, and production of reactive oxygen species. RESULTS: Electron microscopically, SpermFertil showed a higher number of leukocytes attached to the fibers compared to coarse-structure glass wool. Leukocytes in native semen and after glass wool filtration as determined by peroxidase cytochemistry confirmed this observation. Reactive oxygen species decreased from 45.303 counts/10(7) viable cells in native semen to 15.806 counts/10(7) cells in coarse structure wool and 7.465 counts/10(7) cells in Spermfertil, respectively. CONCLUSIONS: Removal of leukocytes from semen of oligozoospermic patients by means of glass wool filtration is a useful method to distinguish production of reactive oxygen species by leukocytes versus sperm cells. 相似文献
58.
This paper describes an algorithm for finding the minimal cutsets between a specified source and terminal nodes of directed/undirected networks. Adjacent nodes of a source node/merged node are determined by the collection of node numbers of columns corresponding to non-zero elements of the first row of the adjacency matrix to form the reduced adjacency matrix (RAM) corresponding to merged nodes. Connectivity of RAM has been checked to obtain the minimal cutsets. 相似文献
59.
V. K. Singh 《Journal of Materials Science》1996,31(19):5163-5168
Measurement of the initial sintering shrinkage of CaAl2O4 at temperatures of 1300, 1325 and 1350 °C are reported. The particle sizes chosen were –53 + 45, –63 + 53 and –75 + 63 microns and the soaking periods were from 15 to 360 min. A time dependence of the shrinkage has shown that volume diffusion is the dominant mechanism of sintering. At any given time and temperature, the per cent shrinkage was found to be a decreasing function of particle size. The activation energy for the sintering of CaAl2O4 was found to be 766.38 KJ mol–1. 相似文献
60.