全文获取类型
收费全文 | 32870篇 |
免费 | 3641篇 |
国内免费 | 2347篇 |
专业分类
电工技术 | 2461篇 |
技术理论 | 1篇 |
综合类 | 2523篇 |
化学工业 | 4307篇 |
金属工艺 | 2195篇 |
机械仪表 | 1911篇 |
建筑科学 | 2250篇 |
矿业工程 | 1043篇 |
能源动力 | 965篇 |
轻工业 | 3751篇 |
水利工程 | 876篇 |
石油天然气 | 1033篇 |
武器工业 | 327篇 |
无线电 | 3587篇 |
一般工业技术 | 3423篇 |
冶金工业 | 2576篇 |
原子能技术 | 535篇 |
自动化技术 | 5094篇 |
出版年
2024年 | 221篇 |
2023年 | 577篇 |
2022年 | 1389篇 |
2021年 | 1833篇 |
2020年 | 1290篇 |
2019年 | 938篇 |
2018年 | 969篇 |
2017年 | 1172篇 |
2016年 | 1040篇 |
2015年 | 1469篇 |
2014年 | 1801篇 |
2013年 | 2064篇 |
2012年 | 2467篇 |
2011年 | 2598篇 |
2010年 | 2418篇 |
2009年 | 2232篇 |
2008年 | 2190篇 |
2007年 | 2095篇 |
2006年 | 1817篇 |
2005年 | 1565篇 |
2004年 | 1101篇 |
2003年 | 808篇 |
2002年 | 775篇 |
2001年 | 727篇 |
2000年 | 584篇 |
1999年 | 364篇 |
1998年 | 537篇 |
1997年 | 410篇 |
1996年 | 276篇 |
1995年 | 180篇 |
1994年 | 145篇 |
1993年 | 150篇 |
1992年 | 66篇 |
1991年 | 50篇 |
1990年 | 63篇 |
1989年 | 53篇 |
1988年 | 36篇 |
1987年 | 41篇 |
1986年 | 30篇 |
1985年 | 31篇 |
1984年 | 25篇 |
1983年 | 21篇 |
1982年 | 26篇 |
1981年 | 49篇 |
1980年 | 26篇 |
1979年 | 16篇 |
1978年 | 13篇 |
1977年 | 28篇 |
1976年 | 32篇 |
1975年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
101.
造纸毛毯的发展与应用 总被引:2,自引:0,他引:2
本文拟就1963年至今我国造纸毛毯的生产和应用技术的发展和现状及造纸毛毯清洗系统的关键技术问题进行了综述,并就造纸毛毯的合理使用,使其发挥最佳功能提出了若干建议。 相似文献
102.
Investigation of the Microstructure of Rolled Semi—Solid Steel 总被引:3,自引:0,他引:3
In this paper,spring steel-60Si2Mn and stainless steel-1Cr18Ni9Ti were rolled one pass in semi-solid state.The microstructural evolution during rolling of the steels with different solid fraction was investigated.The experimental results showed that the manner of liquid and solid phases flowing and deforming was different.During rolling,most of solid phases remained in the center of the rolled specimens,while liquid phase flowed to the edge,which resulted in the macrosegregation of liquid and solid phases.Only the amount of solid fraction reached a certain value,were the solid phases deformed and flattened. 相似文献
103.
104.
毛丰付 《湖南纺织高等专科学校学报》2007,17(2):8-10
通过对资本一般概念的分析,结合资本一般的运动功能论述,认为在经济全球化和网络条件下,资本增值属性必然导致对规则和标准的争夺与控制,标准战是资本一般在新的经济社会形态下发展的必然逻辑结果。 相似文献
105.
本文介绍了配电电力地理信息系统外业数据采集编码的方法;其中包括线路编码、点编码、线路分界点编码、变电所的编码、开关的编码方法等。 相似文献
106.
Activating point mutations in the Ras oncogene occur in a large number of human tumors, especially of epithelial origin. In thyroid follicular cells, ectopic expression of oncogenic H-Ras results in growth factor-independent proliferation, loss of differentiation and tumor formation in nude mice. In fibroblasts concomitant activation of the MAP kinase cascade and the small GTPase Rac-1 leads to full malignant transformation. We have tested the effects of these key downstream mediators of Ras in thyroid epithelial cells, by stably expressing either a constitutively active form of MEK-1 (MEK(deltaN3/S218E/S222D)), a constitutively active form of Rac-1 (Val12-Rac), or both. While the activation of one molecule or the other results in a weak phenotype, concomitant activation of both MEK-1 and Rac-1 in thyroid cells leads to growth factor-independent proliferation, morphological transformation and anchorage-independent growth. However, in contrast to Ras-transformed thyroid cells, the ones expressing the constitutively active forms of MEK-1 and Rac-1 maintain their differentiate phenotype and fail to form tumors when injected into nude mice. Thus, in thyroid epithelial cells, concomitant activation of MEK-1 and Rac-1 can reproduce only a subset of the Ras-induced effects and is not sufficient to cause full malignant transformation. Significantly, Ras-mediated increased proliferation and loss of differentiation can be dissociated in these cells. 相似文献
107.
I Messana M Angeletti M Castagnola G De Sanctis E Di Stasio B Giardina S Pucciarelli M Coletta 《Canadian Metallurgical Quarterly》1998,273(25):15329-15334
The interaction of inositol hexakisphosphate (IHP) with oxygenated human adult hemoglobin (Hb) was investigated at 25 degreesC. The affinity of IHP for oxygenated Hb is strongly pH-dependent, and potentiometric measurements of proton uptake and release upon IHP addition have shown that over the range between pH 8.0 and pH 6.0 in oxygenated Hb there are three groups of residues that change their pKa values after IHP addition, likely because of their interaction with negative charges of the heterotropic effector. On the basis of previous calculations on the electrostatic properties of human Hb (Matthew, J. B., Hanania, G. I. H., and Gurd, F. R. N. (1979) Biochemistry 18, 1919-1928; Lee, A. W.-m., Karplus, M., Poyart, C., and Bursaux, E. (1988) Biochemistry 27, 1285-1301), two of these groups might be Val1beta and His143beta, which are located in the beta1beta2 dyad axis, where they have been also proposed to interact with 2,3-diphosphoglycerate, whereas the third group does not appear easily identifiable. Calorimetric measurements of the heat associated with IHP binding at different pH values over the same range indicate that IHP binding is mostly enthalpy-driven at pH < 7 and mostly entropy-driven at pH > 7. 相似文献
108.
Grizzle J.W. Di Benedetto M.D. Lamnabhi-Lagarrigue F. 《Automatic Control, IEEE Transactions on》1994,39(9):1782-1794
In the literature, it has been shown that if a single-input single-output analytic nonlinear plant 1) has a well-defined relative degree and 2) is minimum-phase, it is possible to achieve asymptotic tracking for an open set of output trajectories containing the origin in CN [0, ∞), the space of N-times continuously differentiable functions taking values in R. When either of these sufficient conditions is not met, various authors have investigated approximate analytic solutions, discontinuous solutions and solutions for restricted sets of trajectories. In this paper, it is shown that conditions 1) and 2) are necessary for the existence of an analytic compensator which yields asymptotic tracking for an open set of output trajectories. Analogous results are established for multi-input multi-output systems 相似文献
109.
AE Calogero F Nicoletti MA Palumbo N Burrello M Di Mauro M Lunetta K Bendtzen A Cianci 《Canadian Metallurgical Quarterly》1998,10(10):814-818
Myoclonus of the middle ear is a rare condition characterized by abnormal repetitive muscle contractions of the tympanic cavity. In this paper we describe what we believe is the first reported case of continuous high-frequency objective tinnitus caused by middle ear myoclonus. During exploratory tympanomastoidectomy it was hypothesized that a small dural arteriovenous malformation not identified on previous tests was the cause of the tinnitus. However, complete disappearance of the tinnitus during administration of curare for anesthesia led us to believe that the tinnitus might have been caused by myoclonus of the middle ear. Sectioning of the stapedius and tensor tympani tendons rendered the patient asymptomatic and confirmed the diagnosis of middle ear myoclonus. At follow-up of one year, the patient's quality of life had improved substantially; the tinnitus did not recur and she no longer had vertigo. 相似文献
110.
1. The spontaneously hypertensive rat (SHR) exhibits a lower bodyweight in utero and an exaggerated salt appetite post partum. To determine whether salt appetite is affected by the perinatal environment, we measured the salt appetite of embryo-cross-transferred SHR and Wistar Kyoto (WKY) rats at maturity. 2. One-cell embryos were collected from the oviducts of donor rats and transferred into the oviducts of recipients through the infundibulum. The salt appetite of the resultant female offspring for 0.10 and 0.15 mol/L saline was measured at 20-30 weeks of age. 3. Salt intake of SHR gestated in WKY rats was significantly lower than that of SHR gestated in SHR, while that of WKY rats gestated in SHR was higher than that of WKY rats gestated in WKY rats. 4. Therefore, some maternal factor plays a role in the development of the exaggerated salt appetite of the SHR. This factor is also able to affect the later salt appetite of WKY rat offspring born to SHR surrogates. 相似文献