全文获取类型
收费全文 | 2273篇 |
免费 | 0篇 |
专业分类
电工技术 | 6篇 |
综合类 | 1篇 |
化学工业 | 42篇 |
金属工艺 | 7篇 |
机械仪表 | 10篇 |
建筑科学 | 13篇 |
矿业工程 | 1篇 |
能源动力 | 3篇 |
轻工业 | 18篇 |
水利工程 | 4篇 |
石油天然气 | 1篇 |
无线电 | 40篇 |
一般工业技术 | 48篇 |
冶金工业 | 2049篇 |
原子能技术 | 11篇 |
自动化技术 | 19篇 |
出版年
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 2篇 |
2014年 | 2篇 |
2013年 | 14篇 |
2012年 | 12篇 |
2011年 | 11篇 |
2010年 | 8篇 |
2009年 | 8篇 |
2008年 | 16篇 |
2007年 | 16篇 |
2006年 | 9篇 |
2005年 | 14篇 |
2004年 | 7篇 |
2003年 | 16篇 |
2002年 | 13篇 |
2001年 | 10篇 |
2000年 | 5篇 |
1999年 | 64篇 |
1998年 | 665篇 |
1997年 | 332篇 |
1996年 | 232篇 |
1995年 | 108篇 |
1994年 | 127篇 |
1993年 | 125篇 |
1992年 | 23篇 |
1991年 | 21篇 |
1990年 | 29篇 |
1989年 | 34篇 |
1988年 | 28篇 |
1987年 | 20篇 |
1986年 | 23篇 |
1985年 | 17篇 |
1984年 | 4篇 |
1983年 | 12篇 |
1982年 | 12篇 |
1981年 | 13篇 |
1980年 | 22篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 44篇 |
1976年 | 101篇 |
1974年 | 5篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1971年 | 3篇 |
1970年 | 5篇 |
1959年 | 2篇 |
1955年 | 2篇 |
1932年 | 2篇 |
排序方式: 共有2273条查询结果,搜索用时 15 毫秒
51.
This paper presents summaries of initiatives and demonstration programs developed by professional and patient care organizations to improve care at the end of life. 相似文献
52.
53.
DG Winkler RE Cutler JK Drugan S Campbell DK Morrison JA Cooper 《Canadian Metallurgical Quarterly》1998,273(34):21578-21584
We have identified mutations in Raf-1 that increase binding to Ras. The mutations were identified making use of three mutant forms of Ras that have reduced Raf-1 binding (Winkler, D. G., Johnson, J. C., Cooper, J. A., and Vojtek, A. B. (1997) J. Biol. Chem. 272, 24402-24409). One mutation in Raf-1, N64L, suppresses the Ras mutant R41Q but not other Ras mutants, suggesting that this mutation structurally complements the Ras R41Q mutation. Missense substitutions of residues 143 and 144 in the Raf-1 cysteine-rich domain were isolated multiple times. These Raf-1 mutants, R143Q, R143W, and K144E, were general suppressors of three different Ras mutants and had increased interaction with non-mutant Ras. Each was slightly activated relative to wild-type Raf-1 in a transformation assay. In addition, two mutants, R143W and K144E, were active when tested for induction of germinal vesicle breakdown in Xenopus oocytes. Interestingly, all three cysteine-rich domain mutations reduced the ability of the Raf-1 N-terminal regulatory region to inhibit Xenopus oocyte germinal vesicle breakdown induced by the C-terminal catalytic region of Raf-1. We propose that a direct or indirect regulatory interaction between the N- and C-terminal regions of Raf-1 is reduced by the R143W, R143Q, and K144E mutations, thereby increasing access to the Ras-binding regions of Raf-1 and increasing Raf-1 activity. 相似文献
54.
Choline, a vital amine 总被引:1,自引:0,他引:1
JK Blusztajn 《Canadian Metallurgical Quarterly》1998,281(5378):794-795
55.
56.
Collecting and processing records from the ultracentrifuge in "real-time" using an on-line computer 总被引:1,自引:0,他引:1
An analytical system consisting of an analytical cantrifuge coupled 'on-line' to a computer was assembled and tested. Collection of records from up to 9 solutions was achieved through programmes which sum readings to reduce noise as well as controlling the positioning of the scanner. With this system it was found that the limit on accuracy for molecular weights at concentrations less than 0.01 g cm-3 was +/- 3% estimated from sedimentation equilibrium experiments. The same system was used to collect records for similar concentrations from velocity experiments by employing a scanning schlieren. In this case the accuracy in estimating sedimentation coefficients was similar to those found when measuring photographs. Since the collection yields detailed information about the shape of the sedimenting boundary, the centroids of the boundary were routinely computed by second moment analysis rather than relying on the position of the maximum of the schlieren peak. In the same analysis estimates of diffusion coefficients were made routinely by calculating corrected height/area ratios for each scan. These calculations were made during the real-time of the experiment, so making available molecular parameters rather than records which must be evaluated some time after stopping the experiment. 相似文献
57.
Colitis cystica profunda is a benign disease of the colon. Its importance lies in differentiating it from mucus-producing adenocarcinoma. It has rarely been described in the surgical literature. A review of records of patients seen at the Mayo Clinic produced 66 clinical cases of localized colitis cystica profunda, and in 21 patients the diagnosis was confirmed histologically. Follow-up, which was available in all patients, ranged from 2 months to 29 years, with a mean follow-up of more than 8 years. The data suggest that local excision is the preferred initial therapy. 相似文献
58.
59.
We developed a model to predict the availability of PAHs and PCBs to earthworms (Lumbricus terrestris L.) in soils. We related the uptake of PAHs and PCBs by earthworms to the extraction with octadecyl-modified silica disks (C18 disks). Eleven soils (data set A) were used to develop the model, and 14 additional soils (data set B) were used to validate it independently. The biota-to-soil accumulation factors (BSAFs) of higher molecular weight PAHs (> or =202 g mol(-1)) and PCBs were higher than the corresponding Cl8 disk-soil partition coefficients (Kdisk) in the soils of data set A. This suggested that PAHs and PCBs were not only partitioned between soil and earthworms but also selectively ingested or metabolized. Nevertheless, we could predict the BSAFs of individual PAHs and PCBs for data set A by regression equations of log BSAF on log Kdisk (r=0.47-0.87). To predict the BSAFs of all PAHs and PCBs, respectively, we derived a model for each compound class that uses Kdisk and K(ow) values. Both the compound and the compound-class specific model were suitable to predict the BSAFs of PAHs and PCBs in data set B within a factor of 10-15. 相似文献
60.
Frese Michael; Krauss Stefanie I.; Keith Nina; Escher Susanne; Grabarkiewicz Rafal; Luneng Siv Tonje; Heers Constanze; Unger Jens; Friedrich Christian 《Canadian Metallurgical Quarterly》2007,92(6):1481
A model of business success was developed with motivational resources (locus of control, self-efficacy, achievement motivation, and self-reported personal initiative) and cognitive resources (cognitive ability and human capital) as independent variables, business owners' elaborate and proactive planning as a mediator, and business size and growth as dependent variables. Three studies with a total of 408 African micro and small-scale business owners were conducted in South Africa, Zimbabwe, and Namibia. Structural equation analyses partially supported the hypotheses on the importance of psychological planning by the business owners. Elaborate and proactive planning was substantially related to business size and to an external evaluation of business success and was a (partial) mediator for the relationship between cognitive resources and business success. The model carries important implications for selection, training, and coaching of business owners. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献