全文获取类型
收费全文 | 12656篇 |
免费 | 1026篇 |
国内免费 | 359篇 |
专业分类
电工技术 | 118篇 |
技术理论 | 1篇 |
综合类 | 784篇 |
化学工业 | 6915篇 |
金属工艺 | 578篇 |
机械仪表 | 197篇 |
建筑科学 | 981篇 |
矿业工程 | 216篇 |
能源动力 | 171篇 |
轻工业 | 1293篇 |
水利工程 | 135篇 |
石油天然气 | 512篇 |
武器工业 | 27篇 |
无线电 | 175篇 |
一般工业技术 | 888篇 |
冶金工业 | 563篇 |
原子能技术 | 103篇 |
自动化技术 | 384篇 |
出版年
2024年 | 53篇 |
2023年 | 113篇 |
2022年 | 278篇 |
2021年 | 449篇 |
2020年 | 309篇 |
2019年 | 273篇 |
2018年 | 259篇 |
2017年 | 334篇 |
2016年 | 403篇 |
2015年 | 434篇 |
2014年 | 674篇 |
2013年 | 688篇 |
2012年 | 814篇 |
2011年 | 911篇 |
2010年 | 649篇 |
2009年 | 715篇 |
2008年 | 691篇 |
2007年 | 766篇 |
2006年 | 787篇 |
2005年 | 662篇 |
2004年 | 566篇 |
2003年 | 461篇 |
2002年 | 421篇 |
2001年 | 373篇 |
2000年 | 357篇 |
1999年 | 277篇 |
1998年 | 237篇 |
1997年 | 146篇 |
1996年 | 157篇 |
1995年 | 136篇 |
1994年 | 132篇 |
1993年 | 116篇 |
1992年 | 78篇 |
1991年 | 54篇 |
1990年 | 50篇 |
1989年 | 42篇 |
1988年 | 22篇 |
1987年 | 34篇 |
1986年 | 16篇 |
1985年 | 19篇 |
1984年 | 27篇 |
1983年 | 18篇 |
1982年 | 17篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1959年 | 2篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Intact and ovariectomized oxytocin (OT)-deficient (OT-/-) and wild-type (OT+/+) mice were tested for consumption of 0.5 M NaCl solution or tap water in a 2-bottle choice test. During 3 days of acclimation, voluntary ingestion of NaCl was equal between genotypes. After overnight fluid deprivation, intact OT-/- mice ingested 2 times more NaCl solution than OT+/+ mice in the 6th hr, but not the 1 st hr, after reintroduction of fluid. Ovariectomized mice consumed less than intact mice after overnight fluid deprivation. When a 0.2 M NaCl solution was administered for 6 days in ovariectomized mice, OT-/- mice voluntarily consumed greater amounts than OT+/+ mice. After overnight fluid deprivation, consumption by OT-/- mice was 3 times that of OT+/+ mice at 1 hr and 2-fold greater after 6 hr. Enhanced intake of NaCl-containing solutions in female OT-/- mice suggests that central OT may be an important inhibitor of sodium consumption. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
32.
模拟我国南方沿海浪溅区和水位变动区的海工钢筋混凝土结构物的腐蚀环境,对掺入粉煤灰和矿渣的混凝土抗氯离子侵蚀性进行了试验。结果表明,在水灰比相同的条件下,加掺和料的混凝土抗氯离子侵蚀性高于普通混凝土。 相似文献
33.
34.
35.
X-ray photoelectron spectroscopy (XPS) applied to the study of fluorinated polymer surfaces presents several problems related both to peak assignment and to degradation. In this work, we analyse extensively the question of XPS peak assignments in this kind of surfaces. We conclude that in this kind of surfaces using binding energy differences between fluorine and carbon is better than using absolute binding energies. Also a useful relation between fluorine photoelectron energy vs. polymer composition expressed through the atomic ratio fluorine/carbon (F/C) was found. A protocol for data treatment is proposed and applied to a XPS study of the degradation induced by X-ray on high-density polyethylene surfaces modified by direct fluorination. Results obtained for the degradation, namely the atomic ratio F/C obtained by two different methods, combined with angle resolved X-ray photoelectron spectroscopy (ARXPS) were used to study the fluorine concentration profile in depth, producing self-consistent results. 相似文献
36.
37.
空心微珠改性硬质聚氯乙烯复合材料的应用研究 总被引:13,自引:1,他引:12
经过改性的超细空心微珠可以作为填料加入到硬质聚氯乙烯(PVC-U)树脂中,同时改善PVC树脂的流变性、冲击性能和刚性等性能。研究结果表明,超细空心微珠加入到硬质PVC管材中,可以明显改善PVC硬管的加工流动性能,显著缩短塑化时间,降低最大扭矩。而超细空民微珠加入到硬质PVC板材时,可以提高PVC硬板的冲击性能,减小制品的收缩率,赋予PVC硬板优异的耐腐蚀性能,且产品的各项性能均符合PVC板材国家标准GB/T4454-96。 相似文献
38.
分子结构对增塑聚氯乙烯性能的影响 总被引:2,自引:0,他引:2
研究了聚合度、分子量分布和支化结构对增塑聚氯乙烯加工流变性能和物理力学性能的影响。结果表明,增塑PVC的加工流变性能随聚合度的增加而恶化;拓宽分子量分布和引入支化结构均有利于加工流变性能的提高;增塑PVC的拉伸强度随聚合度的增加而提高,而压缩永久变形却随之减小;分子量分布对物理力学性能的影响不大;支化PVC的拉伸强度略有下降。 相似文献
39.
Ana Mafalda RibeiroJosé Miguel Loureiro 《Chemical engineering science》2002,57(9):1621-1626
The system ASC carbon filter/cyanogen chloride was studied by simulation. Three filter configurations and several models, taking into account Langmuir adsorption and second-order reaction between the adsorbed toxic vapour and the active metal on the surface, were developed.The effects of axial dispersion, number of reaction units, film mass transfer units and intraparticle mass transfer resistance on the breakthrough time were studied.Simulation results show that a complex model should be used in order to predict with reasonable accuracy the protection imparted by these filters. 相似文献
40.
L. Z. Jin 《Journal of Materials Engineering and Performance》1994,3(6):734-739
Chloride-induced stress-corrosion cracking (SCC) is one of the failure modes of stainless steels. Highly alloyed austenitic
stainless steels S32654, S31254, and N08028, and duplex grades S32750 and S31803 possess much improved resistance to SCC compared
with S30400 and S31600 steels. With the development of a database, SSData, experimental data collected from calcium chloride
tests, autoclave tests, and drop evaporation tests were evaluated. Stress-corrosion cracking data generated by autoclave tests
agreed well with the practical service conditions and can be used to discriminate alloys for SCC resistance in sodium chloride
solution. Drop evaporation test data can be used in situations where evaporation may occur and cyclic loading may be involved.
The SCC resistance of alloys under each method increased with increasing molybdenum equivalent Mo + 0.25Cr + 0.1Ni. For a
given alloy, the testing result depends on the stress state and environment; different test methods can give different ranking
orders concerning SCC resistance. The performance of duplex stainless steels in a chloride-containing environment at higher
temperatures was not as good as expected when dynamic loading was involved. 相似文献