全文获取类型
收费全文 | 3688篇 |
免费 | 48篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 46篇 |
综合类 | 28篇 |
化学工业 | 141篇 |
金属工艺 | 9篇 |
机械仪表 | 105篇 |
建筑科学 | 45篇 |
矿业工程 | 13篇 |
能源动力 | 11篇 |
轻工业 | 385篇 |
水利工程 | 11篇 |
石油天然气 | 3篇 |
无线电 | 82篇 |
一般工业技术 | 148篇 |
冶金工业 | 2562篇 |
原子能技术 | 4篇 |
自动化技术 | 157篇 |
出版年
2022年 | 19篇 |
2021年 | 6篇 |
2020年 | 18篇 |
2019年 | 35篇 |
2018年 | 10篇 |
2017年 | 9篇 |
2016年 | 11篇 |
2015年 | 6篇 |
2014年 | 12篇 |
2013年 | 172篇 |
2012年 | 39篇 |
2011年 | 45篇 |
2010年 | 44篇 |
2009年 | 46篇 |
2008年 | 49篇 |
2007年 | 52篇 |
2006年 | 37篇 |
2005年 | 37篇 |
2004年 | 29篇 |
2003年 | 34篇 |
2002年 | 20篇 |
2000年 | 17篇 |
1999年 | 95篇 |
1998年 | 832篇 |
1997年 | 481篇 |
1996年 | 317篇 |
1995年 | 170篇 |
1994年 | 139篇 |
1993年 | 168篇 |
1992年 | 35篇 |
1991年 | 37篇 |
1990年 | 49篇 |
1989年 | 50篇 |
1988年 | 45篇 |
1987年 | 59篇 |
1986年 | 42篇 |
1985年 | 46篇 |
1984年 | 14篇 |
1983年 | 10篇 |
1982年 | 19篇 |
1981年 | 28篇 |
1980年 | 25篇 |
1979年 | 16篇 |
1978年 | 12篇 |
1977年 | 66篇 |
1976年 | 147篇 |
1975年 | 7篇 |
1973年 | 8篇 |
1955年 | 18篇 |
1954年 | 16篇 |
排序方式: 共有3750条查询结果,搜索用时 31 毫秒
91.
B Errede RM Cade BM Yashar Y Kamada DE Levin K Irie K Matsumoto 《Canadian Metallurgical Quarterly》1995,42(4):477-485
In the budding yeast, Saccharomyces cerevisiae, four separate but structurally related mitogen-activated protein kinase (MAPK) activation pathways are known. The best understood of these regulates mating. Pheromone binding to receptor informs cells of the proximity of a mating partner and induces differentiation to a mating competent state. The MAPK activation cascade mediating this signal is made up of Ste11 (a MEK kinase [MEKK]), Ste7 (a MAPK/ERK kinase [MEK]), and the redundant MAPK-related Fus3 and Kss1 enzymes. Another MAPK activation pathway is important for cell integrity and regulates cell wall construction. This cascade consists of Bck1 (a MEKK), the redundant Mkk1 and Mkk2 enzymes (MEKs), and Mpk1 (a MAPK). We exploited these two pathways to learn about the coordination and signal transmission fidelity of MAPK activation cascades. Two lines of evidence suggest that the activities of the mating and cell integrity pathways are coordinated during mating differentiation. First, cells deficient in Mpk1 are susceptible to lysis when they make a mating projection in response to pheromone. Second, Mpk1 activation during pheromone induction coincides with projection formation. The mechanism underlying this coordination is still unknown to us. Our working model is that projection formation generates a mobile second messenger for activation of the cell integrity pathway. Analysis of a STE7 mutation gave us some unanticipated but important insights into parameters important for fidelity of signal transmission. The Ste7 variant has a serine to proline substitution at position 368. Ste7-P368 has higher basal activity than the wild-type enzyme but still requires Ste11 for its function. Additionally, the proline substitution enables the variant to transmit the signal from mammalian Raf expressed in yeast. This novel activity suggests that Ste7-P368 is inherently more permissive than Ste7 in its interactions with MEKKs. Yet, Ste7-P368 cross function in the cell integrity pathway occurs only when it is highly overproduced or when Ste5 is missing. This behavior suggests that Ste5, which has been proposed to be a tether for the kinases in the mating pathway, contributes to Ste7 specificity and fidelity of signal transmission. 相似文献
92.
D. M. dos Anjos K. B. Kokoh J.M. Léger A.R. DE Andrade P. Olivi G. Tremiliosi-Filho 《Journal of Applied Electrochemistry》2006,36(12):1391-1397
Pt–Mo alloy electrocatalysts were prepared by an arc-melting furnace process to investigate the origin of their enhanced activity toward ethanol oxidation. Two Mo contents were chosen in zones of the binary phase diagram where they are supposed to form either a pure alloy mixture or a solid solution. Pt–Mo alloy catalysts were more active than Pt-alone. Gradual Mo dissolution at the electrode surface was observed after voltammetric and chronoamperometric measurements. The dissolved Mo contributed to the catalytic effect of the electrode as underpotentially deposited (upd) adatoms. This dissolution probably also leads to an increase in the electrode surface roughness. Low molybdenum content in the electrode material enhances the activity toward ethanol oxidation when compared to Pt-alone. Ethanol oxidation was also investigated by in situ infrared reflectance spectroscopy in order to determine the presence of adsorbed intermediates like CO species. Acetaldehyde, acetic acid and CO2 were also found by spectroscopic experiments. 相似文献
93.
The application of combined g.c.-m.s. with automated data processing to the rapid analysis of coal solvents has been described. An analytical method, using commercially available data processing routines, has been developed for the automatic quantitative analysis of specific aromatic and hydroaromatic compounds in coal processing solvents. To demonstrate the use of this technique, raw anthracene oil was hydrogenated under different conditions and the resulting hydrogenated anthracene oils were analysed. The results showed correlations between the hydrogen content and the absolute concentrations of specific compounds in the samples. 相似文献
94.
AISI 304奥氏体不锈钢表面经激光熔化处理,引入一个大的张应力,它可用注Ne的方法使其缓解本文介绍测量0.1μm薄层应力变化的原理和技术,由测得的应力分布曲线证明了注Ne缓解表面张应力的效果 相似文献
95.
96.
DE Gibbons 《Canadian Metallurgical Quarterly》1998,60(11):669-671
The former purchaser-provider split underwent an important change during the last years in UK. Especially since the new government came into office in 1997 the approach to equity and equality in dental health care has been characterised by two decisions. Firstly, the level of commissioning services was shifted from the centre to so-called natural communities of about 100,000 people. Secondly, the groups responsible for planning and providing care are constituted from local medical practitioners, community nurses and social services representatives, in line with the Regional Health Authority and the national framework "Our Healthier Nation". The new community dental service is expected to be in a better position to improve the situation in areas of social exclusion. 相似文献
97.
M Delgado EJ Munoz-Elias Y Kan I Gozes M Fridkin DE Brenneman RP Gomariz D Ganea 《Canadian Metallurgical Quarterly》1998,273(47):31427-31436
98.
JD Reveille GS Alarcón SE Fowler SR Pillemer R Neuner DO Clegg IS Mikhail DE Trentham JC Leisen G Bluhm SM Cooper H Duncan M Tuttleman SP Heyse JT Sharp B Tilley 《Canadian Metallurgical Quarterly》1996,39(11):1802-1807
OBJECTIVE: To examine the effect of alleles encoding the "shared"/"rheumatoid" epitope on rheumatoid arthritis (RA) disease severity in patients who participated in the minocycline in RA (MIRA) trial. METHODS: Of 205 patients with a week-48 visit, blood was available for typing of HLA-DRB1 and HLA-DQB1 in 174 (85%) and successfully completed in 169 (82%). Baseline erosions were used to assess disease severity and new erosions at the last visit served as a proxy for progression. RESULTS: At baseline, there was no association between the presence of erosive disease or rheumatoid factor status and the dose of rheumatoid epitope (homozygous, heterozygous, none) or the specific alleles identified. At the final visit, a gradient was observed for the 3 allelic subgroups (and their gene doses) in the occurrence of new erosions among the Caucasian placebo-treated, but not the minocycline-treated, patients. A treatment group/HLA-DR4 epitope interaction was demonstrated in multivariate analyses. Approximately two-thirds of African-American patients did not have the rheumatoid epitope. CONCLUSION: HLA-DRB1 oligotyping may be useful in predicting the progression of disease in some Caucasian patients. Our study corroborates the infrequency of the epitope among African-American patients with RA. 相似文献
99.
Clients are leaving the hospital "quicker and sicker," and they frequently have acute care needs that must be met by resources outside the hospital setting. Community resources are diverse, vary widely from place to place, and have no central administration. Thus, using them can be challenging for both the nurse, client, and family. Reimbursement mechanisms underlie a person's ability to use resources and receive health care. By presenting two actual case scenarios where clients have mobility problems commonly seen by orthopaedic nurses, the authors discuss the community resources available, avenues of access to them, and their reimbursement mechanisms. 相似文献
100.