全文获取类型
收费全文 | 41886篇 |
免费 | 1382篇 |
国内免费 | 146篇 |
专业分类
电工技术 | 569篇 |
综合类 | 246篇 |
化学工业 | 7229篇 |
金属工艺 | 937篇 |
机械仪表 | 907篇 |
建筑科学 | 1490篇 |
矿业工程 | 117篇 |
能源动力 | 1213篇 |
轻工业 | 5527篇 |
水利工程 | 351篇 |
石油天然气 | 178篇 |
武器工业 | 6篇 |
无线电 | 3642篇 |
一般工业技术 | 6111篇 |
冶金工业 | 9132篇 |
原子能技术 | 407篇 |
自动化技术 | 5352篇 |
出版年
2023年 | 198篇 |
2022年 | 616篇 |
2021年 | 1011篇 |
2020年 | 657篇 |
2019年 | 779篇 |
2018年 | 904篇 |
2017年 | 977篇 |
2016年 | 968篇 |
2015年 | 704篇 |
2014年 | 1144篇 |
2013年 | 2072篇 |
2012年 | 1740篇 |
2011年 | 2233篇 |
2010年 | 1660篇 |
2009年 | 1695篇 |
2008年 | 1646篇 |
2007年 | 1484篇 |
2006年 | 1215篇 |
2005年 | 1264篇 |
2004年 | 1243篇 |
2003年 | 1142篇 |
2002年 | 1093篇 |
2001年 | 984篇 |
2000年 | 827篇 |
1999年 | 853篇 |
1998年 | 2953篇 |
1997年 | 1921篇 |
1996年 | 1371篇 |
1995年 | 953篇 |
1994年 | 749篇 |
1993年 | 809篇 |
1992年 | 375篇 |
1991年 | 426篇 |
1990年 | 367篇 |
1989年 | 336篇 |
1988年 | 337篇 |
1987年 | 270篇 |
1986年 | 273篇 |
1985年 | 337篇 |
1984年 | 239篇 |
1983年 | 186篇 |
1982年 | 191篇 |
1981年 | 215篇 |
1980年 | 210篇 |
1979年 | 183篇 |
1978年 | 125篇 |
1977年 | 250篇 |
1976年 | 378篇 |
1975年 | 133篇 |
1973年 | 109篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
JL Van Laethem M Cremer MO Peny M Delhaye J Devière 《Canadian Metallurgical Quarterly》1998,43(6):747-751
Microcapsules are used for the formulation of drug controlled release and drug targeting dosage forms. Encapsulated hydrophobic drugs are often applied as their solutions in plant oils. The uptake of the oils in the complex coacervate microcapsules can be improved by the addition of surfactants. In this study, soybean, olive and peanut oils were chosen as the representatives of plant oils. The well characterized complex coacervation of gelatin and acacia has been used to produce the microcapsules. The amount of encapsulated oil has been determined gravimetrically. The encapsulation of the oils was high (75-80%). When the surfactants with HLB values from 1.8 to 6.7 were used, the amount of encapsulated oil was high (65-85%). A significant decrease of the oil content in the microcapsules was found when Tween 61 with HLB = 9.6 had been added into the mixture. No oil was found inside the microcapsules from the coacervate emulsion mixture containing Tween 81 (HLB = 10) and Tween 80 (HLB = 15), respectively. The results of the experiment confirm the dependence of hydrophobic substance encapsulation on the HLB published recently for Squalan. 相似文献
82.
EJ Velthuis-te Wierik H van den Berg JA Weststrate KH van het Hof C de Graaf 《Canadian Metallurgical Quarterly》1996,50(4):214-219
Plasma levels of fibrinogen, factor VIIc and prothrombin fragment F1 + 2, a marker of thrombin generation in vivo, were studied in 68 subjects with serum total cholesterol (TC) levels between 135 and 349 mg/dl but without clinical evidence of cardiovascular disease and other atherosclerotic risk factors. F1 + 2 plasma levels were directly correlated with TC (p < 0.0004), low-density lipoprotein cholesterol (LDL-C; p < 0.0018) and factor VIIc (p < 0.024). Thirty-five subjects with TC greater than 249 mg/dl (median value of the whole group) showed higher levels of F1 + 2 (p < 0.0001) and fibrinogen (p < 0.0015) than those with TC lower than 249 mg/dl. In subjects with TC > 249 mg/dl and F1 + 2 > 1.2 nM (median value of the whole group), a cholesterol-lowering drug (simvastatin) was able to reduce F1 + 2 (p < 0.009) as well as TC and LDL-C. This study shows a relationship between serum cholesterol and the rate of thrombin generation supporting the hypothesis that a hypercoagulable state may occur in hypercholesterolemic subjects before the onset of clinical evidence of atherosclerotic cardiovascular disease. 相似文献
83.
Solution of temperature fields in hydrodynamics bearings by the numerical network method 总被引:1,自引:0,他引:1
Solution to the 2-D steady-state nonlinear heat conduction equation, involving cylindrical coordinates, applied to a plain bearing by a simple and versatile numerical technique based on network method is presented in this work. These advantages of the technique are necessary for the status evaluation of industrial machines during operation because time and computing resources are limited. The pressure field in the fluid is previously solved from the Reynolds equation by finite element method. The main difficulty is associated with the exponential dependency of the viscosity on temperature. The proposed model is very efficient and requires negligible computing times. Solutions are very close to the experimental and numerical results of other researchers. 相似文献
84.
International Journal of Computer Vision - 相似文献
85.
Cristiane Vieira Helm Alicia de Francisco Salete Aparecida Gaziola Ricardo Francisco Fornazier Georgia Bertoni Pompeu Ricardo Antunes Azevedo 《Food Biotechnology》2005,18(3):327-341
Barley (Hordeum vulgare L.) has had an important impact on human nutrition. Hull-less barley is a genetically improved type that has been widely used in recent years. Six Brazilian hull-less barley varieties (IAC-IBON 214-82; IAC 8612-421; IAC 8501-31; IAC 8501-12; IAPAR 39-ACUMAI; IAC 8501-22) were analyzed for storage protein constituents, amino acid contents, and similarity among the hull-less barley varieties. Albumins, globulins, prolamins I and II, and glutelins were extracted and separated by SDS-PAGE. The total protein amino acid contents of the flour were also determined for each variety by TLC and HPLC. Variations in intensity and appearance and disappearance of protein bands were observed among the varieties suggesting genetic variability. However, the amino acid profile did not indicate any major variations in the amino acid concentrations. The high lysine and threonine total concentrations detected in the seeds of the hull-less barley varieties encouraged an investigation into the regulation of amino acid metabolism and storage protein synthesis. 相似文献
86.
Fbio Gomes Costa Elias Andrade Braga Soraia Teixeira Brando Alexandre de Freitas Espeleta Zênis Novais da Rocha Lílian Maria Tosta Simplício Emerson Andrade Sales 《Applied Catalysis A: General》2005,290(1-2):221-226
Infrared and UV–vis studies of metallocene immobilization on silica are reported here. The results have indicated changes in the Zr coordination sphere of metallocene depending on the immobilization route used. The reaction of [(Cp)2ZrCl2] with silica formed [(Cp)2ZrCl]+[SiO]− species. The same metallocene, reacting with TMA modified silica, formed monomethylated and dimethylated species by the substitution of chloro for methyl ligands, stabilized on the surface by interaction with “MAO-like” species (methylaluminoxane, MAO). These monomethylated and dimethylated cationic zirconium species are the active centers for the polymerization reaction. Different order of TMA addition in the silica modification step generated surface species of a similar nature, differing in their relative quantities. The highest amount of these active species was obtained when the support was added to the TMA solution rather than adding the TMA solution to the silica support. This was the most significant parameter affecting catalytic activity in ethylene polymerization. 相似文献
87.
Wisse M. Feliksdal G. Van Frankkenhuyzen J. Moyer B. 《Robotics & Automation Magazine, IEEE》2007,14(2):52-62
In this article, we presented our passive-based biped Denise. Using only two foot contact switches as sensors and simple on/off pneumatic muscle action, it walks at 0.4 m/s and can handle floor disturbances up to 6 mm (leg length is 0.7 m). Its simplicity, efficiency, and die natural look of its motions make it a promising lead for the development of commercially viable humanoid robots. The aim of this article is to provide other researchers enough details so that they can reproduce the work or use it as a basis for future research. 相似文献
88.
An adaptable die is one that not only produces the correct geometrical shape, but also is designed through an adaptable method to impart other desirable properties to the product or process. In this first part of a series of papers, six kinematically admissible velocity fields are developed for use in upper bound models for axisymmetric extrusion through various dies, including extrusion through adaptable dies. Three base velocity fields are presented:
- (1) assuming proportional angles in the deformation zone,
- (2) assuming proportional areas in the deformation zone, or
- (3) assuming proportional distances from the centerline in the deformation zone.
89.
We describe a method for computing solutions of multi-point boundary value problems, where the polychotomic structure of the underlying solution space is specifically exploited. After the system is integrated in a multiple shooting way, the resulting linear system is solved by a special decoupling algorithm that takes into account the fact that the dichotomy on each interval is potentially different (in contrast to the two point case). A number of examples sustains the theory. 相似文献
90.
Jing Wang Walker D.M. Xiang Lu Majhi A. Kruseman B. Gronthoud G. Villagra L.E. van de Wiel P.J.A. Eichenberger S. 《Design & Test of Computers, IEEE》2007,24(3):226-234
Excessive power supply noise during test can cause overkill. This article discusses two models for supply noise in delay testing and their application to test compaction. The proposed noise models avoid complicated power network analysis, making them much faster than existing power noise analysis tools. can cause performance degradation and 相似文献