全文获取类型
收费全文 | 37380篇 |
免费 | 1467篇 |
国内免费 | 59篇 |
专业分类
电工技术 | 386篇 |
综合类 | 29篇 |
化学工业 | 7329篇 |
金属工艺 | 736篇 |
机械仪表 | 767篇 |
建筑科学 | 2027篇 |
矿业工程 | 126篇 |
能源动力 | 1099篇 |
轻工业 | 3031篇 |
水利工程 | 439篇 |
石油天然气 | 123篇 |
武器工业 | 5篇 |
无线电 | 2531篇 |
一般工业技术 | 6340篇 |
冶金工业 | 6987篇 |
原子能技术 | 280篇 |
自动化技术 | 6671篇 |
出版年
2023年 | 203篇 |
2022年 | 268篇 |
2021年 | 687篇 |
2020年 | 472篇 |
2019年 | 628篇 |
2018年 | 792篇 |
2017年 | 703篇 |
2016年 | 840篇 |
2015年 | 764篇 |
2014年 | 1055篇 |
2013年 | 2445篇 |
2012年 | 1698篇 |
2011年 | 2126篇 |
2010年 | 1678篇 |
2009年 | 1586篇 |
2008年 | 1847篇 |
2007年 | 1813篇 |
2006年 | 1642篇 |
2005年 | 1475篇 |
2004年 | 1208篇 |
2003年 | 1155篇 |
2002年 | 1084篇 |
2001年 | 717篇 |
2000年 | 570篇 |
1999年 | 633篇 |
1998年 | 674篇 |
1997年 | 629篇 |
1996年 | 590篇 |
1995年 | 596篇 |
1994年 | 551篇 |
1993年 | 537篇 |
1992年 | 517篇 |
1991年 | 297篇 |
1990年 | 439篇 |
1989年 | 412篇 |
1988年 | 342篇 |
1987年 | 381篇 |
1986年 | 330篇 |
1985年 | 440篇 |
1984年 | 448篇 |
1983年 | 340篇 |
1982年 | 316篇 |
1981年 | 307篇 |
1980年 | 299篇 |
1979年 | 292篇 |
1978年 | 263篇 |
1977年 | 247篇 |
1976年 | 233篇 |
1975年 | 212篇 |
1974年 | 187篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
111.
The authors highlight several possible ways in which the construction industry could lower present emissions of the greenhouse gas, carbon dioxide. It is an excellent discussion document and is recommended reading. 相似文献
112.
113.
The purpose of the current study was to describe four models of cognitive deficit and to outline the statistical hypotheses underlying each model. The four models of cognitive deficit were (a) specific deficit; (b) subgroup deficit; (c) a syndrome dissociation model; and (d) a global function dissociation model. Neuropsychological data are analyzed to examine each of these four models in a sample of mild Multiple Sclerosis (MS) patients. The results suggest that for these subjects and tests, the specific deficit model best fits the data. The results are reviewed initially in the context of MS. There follows a consideration of statistical caveats and finally, general applications of the proposed procedures. 相似文献
114.
S Jamali D Archer P Ravussin M Bonnafous P David C Ecoffey 《Canadian Metallurgical Quarterly》1997,84(6):1292-1296
Directed delivery and distribution of anaesthetics (novocaine, lidocaine, trimecaine) immobilized on finely dispersed iron powders under the influence of an external magnetic field in body tissues of test animals have been studied. The data of emission spectral analysis relating to concentration of iron in soft and bone tissues of animals influenced by constant and alternating magnetic field on front and reverse sides over a period from 0 to 180 min are given. 相似文献
115.
Systemised serendipity for producing computer art 总被引:4,自引:0,他引:4
David Walter 《Computers & Graphics》1993,17(6):699-700
Serendipity applied to Newton's method, and its derivative the Secant Method, produces unusual and beautiful fractal patterns. Serendipity may be systemised, for example, by the introduction of a perturbation parameter P1, [1] to facilitate searches for interesting pattern variations. 相似文献
116.
117.
118.
PN Hawkins S Richardson DM Vigushin J David CR Kelsey RE Gray MA Hall P Woo JP Lavender MB Pepys 《Canadian Metallurgical Quarterly》1993,36(6):842-851
OBJECTIVE: To evaluate aspects of the natural history of AA amyloidosis complicating juvenile rheumatoid arthritis (JRA), and its response to therapy with chlorambucil. METHODS: Scintigraphy and 7-day turnover studies were performed in JRA patients with histologically proven (n = 35) or clinically suspected (n = 30) AA amyloidosis, following intravenous injection of 123I and 125I-labeled serum amyloid P component (SAP). Prospective monitoring studies were performed over 2-3 years in 20 patients with amyloidosis. All but 2 amyloidosis patients were treated with chlorambucil. RESULTS: Positive scanning results were obtained in all patients in whom imaging was performed within 12 years of positive biopsy findings of amyloid and in 5 patients with clinically suspected amyloidosis. Negative scanning results with normal SAP metabolism, indicating regression of amyloid, were obtained in 4 patients whose amyloidosis had been in full clinical remission for more than 12 years. Prospective monitoring studies in patients whose JRA-associated inflammatory activity was in remission demonstrated regression of amyloid in 8 patients and no substantial changes in 8 others; however, in 4 further patients with active inflammation, there was accumulation of amyloid. There was a very poor correlation between the amount of amyloid present at a particular site and the resultant organ dysfunction. CONCLUSION: Radiolabeled SAP scintigraphy and turnover studies are useful complementary tools in the diagnosis, screening, and quantitative monitoring of type AA amyloidosis in JRA. The amyloid deposits may progress and/or regress at different rates in different anatomic sites over short periods. 相似文献
119.
We consider the problem of generating a large state-space in a distributed fashion. Unlike previously proposed solutions that partition the set of reachable states according to a hashing function provided by the user, we explore heuristic methods that completely automate the process. The first step is an initial random walk through the state space to initialize a search tree, duplicated in each processor. Then, the reachability graph is built in a distributed way, using the search tree to assign each newly found state to classes assigned to the available processors. Furthermore, we explore two remapping criteria that attempt to balance memory usage or future workload, respectively. We show how the cost of computing the global snapshot required for remapping will scale up for system sizes in the foreseeable future. An extensive set of results is presented to support our conclusions that remapping is extremely beneficial. 相似文献
120.
We have used Path Integral Monte Carlo to study the surface melting of molecular hydrogen. Density profiles perpendicular and parallel to the bare H2 surface are computed showing the formation of a liquid adlayer at 6 K, less than half the bulk melting temperature of para-hydrogen, 13.8 K. To estimate the onset temperature and depth of H2 surface melting we determine the static structure factor within the individual H2-layers for wave vectors in the plane and find no crystalline order down to 3 K in a partially filled H2 adlayer at the free surface. We find quantum effects amplify the melting point depression at the free H2 surface compared to bulk by a factor of five over classical Lennard-Jones solids and find that the zero-point fluctuations of molecules at the surface are much enhanced over their bulk values. We see vacancy formation in the solid before melting. 相似文献