全文获取类型
收费全文 | 11996篇 |
免费 | 1349篇 |
国内免费 | 918篇 |
专业分类
电工技术 | 1070篇 |
综合类 | 1034篇 |
化学工业 | 1300篇 |
金属工艺 | 626篇 |
机械仪表 | 886篇 |
建筑科学 | 773篇 |
矿业工程 | 351篇 |
能源动力 | 474篇 |
轻工业 | 1194篇 |
水利工程 | 468篇 |
石油天然气 | 340篇 |
武器工业 | 153篇 |
无线电 | 1225篇 |
一般工业技术 | 1036篇 |
冶金工业 | 1414篇 |
原子能技术 | 269篇 |
自动化技术 | 1650篇 |
出版年
2024年 | 62篇 |
2023年 | 169篇 |
2022年 | 390篇 |
2021年 | 514篇 |
2020年 | 351篇 |
2019年 | 297篇 |
2018年 | 254篇 |
2017年 | 339篇 |
2016年 | 301篇 |
2015年 | 446篇 |
2014年 | 573篇 |
2013年 | 702篇 |
2012年 | 812篇 |
2011年 | 936篇 |
2010年 | 855篇 |
2009年 | 940篇 |
2008年 | 873篇 |
2007年 | 850篇 |
2006年 | 755篇 |
2005年 | 678篇 |
2004年 | 464篇 |
2003年 | 323篇 |
2002年 | 266篇 |
2001年 | 270篇 |
2000年 | 208篇 |
1999年 | 97篇 |
1998年 | 230篇 |
1997年 | 173篇 |
1996年 | 126篇 |
1995年 | 92篇 |
1994年 | 69篇 |
1993年 | 62篇 |
1992年 | 30篇 |
1991年 | 22篇 |
1990年 | 33篇 |
1989年 | 34篇 |
1988年 | 32篇 |
1987年 | 27篇 |
1986年 | 37篇 |
1985年 | 29篇 |
1984年 | 23篇 |
1981年 | 29篇 |
1980年 | 31篇 |
1979年 | 34篇 |
1977年 | 68篇 |
1976年 | 118篇 |
1974年 | 20篇 |
1973年 | 27篇 |
1971年 | 19篇 |
1970年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
51.
52.
提出了ERP编码的原则,介绍了常见的四种编码方法:顺序码、分类码、结构码和组合码.最后结合实例介绍了编码系统中各模块的设计。 相似文献
53.
赵青南 《武汉理工大学学报(材料科学英文版)》2005,(4)
1Introduction Theultravioletrays(UV)insunlight(-4%)cantransmitintoroomthroughcommonfloatglass,theUVcanmakethematerialsintheroom,eg,paper,furni ture,textilefabricandplastics,becoloredanddeterio rated.ShieldingfromUVirradiationisofinterestinmanyfields.Formu… 相似文献
54.
We present several algorithms for rapidly four-coloring large planar graphs and discuss the results of extensive experimentation with over 140 graphs from two distinct classes of randomly generated instances having up to 128,000 vertices. Although the algorithms can potentially require exponential time, the observed running times of our more sophisticated algorithms are linear in the number of vertices over the range of sizes tested. The use of Kempe chaining and backtracking together with a fast heuristic which usually, but not always, resolves impasses gives us hybrid algorithms that: (1) successfully four-color all our test graphs, and (2) in practice run, on average, only twice as slow as the well-known, nonexact, simple to code, Θ(n) saturation algorithm of Brélaz. 相似文献
55.
Sellis T.K. Shapiro L. 《IEEE transactions on pattern analysis and machine intelligence》1991,17(1):77-86
Database query languages and their use for programming nontraditional applications, such as engineering and artificial intelligence applications, are discussed. In such environments, database programs are used to code applications that work over large data sets residing in databases. Optimizing such programs then becomes a necessity. An examination is made of various optimization techniques, and transformations are suggested for improving the performance of database programs. These transformations result in new equivalent database programs with better space and time performance. Several of these techniques apply to classical query languages, although extended query languages which include an iteration operator are specifically discussed 相似文献
56.
The dependence between the activity parameters of muscarine antagonists in the prevention of haloperidol catalepsy in rats and those in tests characterizing the interaction of ligands and various subtypes of m-cholinoceptors was studied. It was established by constructing the mathematical dependence that blockade of m1-cholinoceptors increases, while that of m2-cholinoceptors reduces the antiparkinsonian activity of the drugs. The activity of the muscarine antagonist pentiphan in the prevention of haloperidol-induced catalepsy in rats exceeds the activity of such traditional antiparkinsonian drugs as cyclodol and amedin. 相似文献
57.
30 patients were exposed to interference currents (IC) alone (group 1) versus 34 patients treated with IC plus iodobromine baths (group 2). After IC action on the region of the kidney projection patients of group 1 experienced positive changes in cellular and humoral immunity providing an antiinflammatory effect. In group 2, the improvement was seen in renal and urinary functions, 24-h urinary excretion of oxalates and calcium diminished. Interference current proved beneficial in chronic pyelonephritis patients with latent inflammation. The combined therapy was effective in patients at high risk of lithogenesis. 相似文献
58.
59.
VT Za?tsev VV Bo?ko BI Peev EM Klimova NI Potapova FK Dib IA Taraban 《Canadian Metallurgical Quarterly》1996,(5-6):86-89
Based on a comprehensive analysis of findings from examination and surgical treatment of 196 patients with bleeding pyloroduodenal ulcers, it was found out that patients with concurrent helicobacteriosis of the stomach are prone to more unfavourable course of their illness, which fact is evidenced by a greater loss of blood and higher risk for bleeding recurrences. A classification is proposed by the authors, taking advantage of the data from endoscopic, microscopic and immunoenzymatic techniques, with the purpose of providing an assessment of degree of severity of helicobacteriosis of the stomach. 相似文献
60.
NI Gluck 《Canadian Metallurgical Quarterly》1996,19(1):41-47
Blood-borne cytokines enter the brain by transport across the blood-brain barrier (BBB) or by leakage through extracellular pathways at sites, such as circumventricular organs (CVOs), without a BBB. We used radioactively labeled albumin (T-Alb) to differentiate the relative contribution of transport and extracellular pathways to the passage of interleukin-1 alpha ([125I]IL-1 alpha) across the BBB. The major mechanism of entry for [125I]IL-1 alpha after intravenous (i.v.) injection was a saturable transport system with extracellular pathways accounting for only a small fraction of entry into brain. CVOs concentrated blood-borne [125I]IL-1 alpha in a saturable manner to a much greater extent than did the cerebral cortex and cerebellum, but accounted for less that 5% of total brain uptake. After intracerebroventricular (i.c.v.) injection, [125I]IL-1 alpha and T-Alb were concentrated in the CVOs, especially the median eminence, although CVOs contained less that 1% of the substances injected. Distribution after i.c.v. injection was largely due to diffusion and leakage through extracellular pathways. We conclude that after i.c.v. injection, leakage across extracellular pathways accounts for the small but concentrated amount of [125I]IL-1 alpha found in CVOs. After i.v. injection, transport across the BBB accounts for the majority of [125I]IL-1 alpha in brain. 相似文献