全文获取类型
收费全文 | 1812篇 |
免费 | 107篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 28篇 |
综合类 | 10篇 |
化学工业 | 163篇 |
金属工艺 | 11篇 |
机械仪表 | 28篇 |
建筑科学 | 39篇 |
矿业工程 | 16篇 |
能源动力 | 22篇 |
轻工业 | 321篇 |
水利工程 | 7篇 |
石油天然气 | 6篇 |
武器工业 | 1篇 |
无线电 | 154篇 |
一般工业技术 | 192篇 |
冶金工业 | 762篇 |
原子能技术 | 33篇 |
自动化技术 | 134篇 |
出版年
2022年 | 14篇 |
2021年 | 16篇 |
2020年 | 11篇 |
2019年 | 17篇 |
2018年 | 19篇 |
2017年 | 13篇 |
2016年 | 24篇 |
2015年 | 18篇 |
2014年 | 15篇 |
2013年 | 62篇 |
2012年 | 50篇 |
2011年 | 64篇 |
2010年 | 31篇 |
2009年 | 34篇 |
2008年 | 62篇 |
2007年 | 62篇 |
2006年 | 60篇 |
2005年 | 66篇 |
2004年 | 61篇 |
2003年 | 50篇 |
2002年 | 52篇 |
2001年 | 35篇 |
2000年 | 28篇 |
1999年 | 40篇 |
1998年 | 212篇 |
1997年 | 119篇 |
1996年 | 98篇 |
1995年 | 47篇 |
1994年 | 59篇 |
1993年 | 67篇 |
1992年 | 13篇 |
1991年 | 27篇 |
1990年 | 20篇 |
1989年 | 24篇 |
1988年 | 14篇 |
1987年 | 16篇 |
1986年 | 16篇 |
1985年 | 19篇 |
1984年 | 14篇 |
1983年 | 18篇 |
1982年 | 15篇 |
1981年 | 15篇 |
1980年 | 19篇 |
1979年 | 14篇 |
1978年 | 13篇 |
1977年 | 28篇 |
1976年 | 57篇 |
1974年 | 12篇 |
1971年 | 8篇 |
1970年 | 10篇 |
排序方式: 共有1927条查询结果,搜索用时 15 毫秒
21.
This naver analvzes the surface emission coefficient corresponding to anv diffusion coefficient expressed as an exponential function of the concentration diffusing substance in capillary porous solids. Theoretical equations for surface emission coefficient for both sorption and desorption are presented. Procedures to derive the diffusion coefficient and to verify the corresponding surface emission coefficient are made using experimental sorption data of aspen (Populur sp.) wood. It is of interest to note that the theoretical models for diffusion and surface emission coefficients can be established and/or evaluated using the same set of experimental dara. 相似文献
22.
DT Smoot JH Resau MH Earlington M Simpson TL Cover 《Canadian Metallurgical Quarterly》1996,39(6):795-799
BACKGROUND: Many Helicobacter pylori strains produce a cytotoxin that induces cytoplasmic vacuolation in various types of eukaryotic cells. In contrast with the marked cell vacuolation that occurs in vitro in response to this cytotoxin, comparatively little epithelial vacuolation has been observed in the gastric mucosa of H pylori infected persons. AIMS: Experiments were performed to determine the susceptibility of human gastric epithelial cells in vitro to H pylori vacuolating cytotoxin activity. METHODS: Human gastric epithelial cells, harvested from upper gastrointestinal endoscopic biopsy specimens, were incubated overnight with broth culture supernatants from either a wild type cytotoxin producing (tox+) H pylori strain or an isogenic mutant strain that lacks cytotoxin activity. RESULTS: Prominent cytoplasmic vacuolation occurred in response to tox+ supernatant, but not supernatant from the isogenic mutant strain. Primary human gastric epithelial cells were significantly more sensitive to H pylori vacuolating cytotoxin activity than were either HeLa or AGS cells. Exposure of human gastric epithelial cells to high concentrations of tox+ supernatant for 48 hours caused lethal cell injury. CONCLUSIONS: These studies indicate that primary human gastric epithelial cells are highly sensitive to H pylori vacuolating cytotoxin activity. 相似文献
23.
RL Simpson 《Canadian Metallurgical Quarterly》1997,28(7):17-18
Nurses now have a central place to check standards and evaluate systems. The Nursing Information and Data Set Evaluation Center develops, disseminates and evaluates nursing practice sets used by vendors. This center, established by the American Nurses Association, ensures that interventions and outcomes related to nursing diagnosis are appropriate and accurate. 相似文献
24.
WE Farrell DJ Simpson JE Bicknell AJ Talbot AS Bates RN Clayton 《Canadian Metallurgical Quarterly》1997,57(13):2703-2709
We have screened 57 cases of primary, nonfunctional, pituitary adenomas for loss of heterozygosity of markers on chromosome 9p. Using a panel of 11 microsatellite markers, we found hemizygous deletion with at least one of the markers in 18 tumors (31.5%). The frequency of loss was similar in both noninvasive (8 of 26; 31%) and invasive tumors (10 of 31; 32%), suggesting that loss on this chromosome might be an early event in pituitary tumorigenesis. Two discrete areas of loss were punctuated by a region of retention of heterozygosity between the markers D9S171 and IFNA, indicative of homozygous deletion. However, multiplex PCR analysis (MTS1 and MTS2) and the presence of a 3' untranslated region polymorphism in MTS1 suggested that neither of these tumor suppressor genes was homozygously deleted. In 6 of the 18 tumors showing LOH, sufficient DNA was also available for Southern blot analysis and, in all cases, showed retention of MTS1. Cell mixing experiments of tumor cell DNA homozygously deleted for MTS1 with DNA in which neither copy of the gene was deleted only gave rise to a signal at contamination levels greater than 30% and could discriminate homozygous and hemizygous loss. These studies support the recent findings that mechanisms other than hemi- and homozygous deletion are most likely responsible for the loss of MTS1 gene product in pituitary tumors (M. Woloschak et al., Cancer Res., 56: 2493-2486, 1996.). These data show that losses on either side of 9p21-22, both or either of which may be deleted, are involved in pituitary tumorigenesis and provide evidence for distinct suppressor gene loci, in addition to MTS1, on chromosome 9p. 相似文献
25.
26.
Most (98%) of the fat in human milk is present as triglycerides. This paper describes the use of a clarification procedure that enables the level of human milk fat to be determined by measurement of glycerol released by enzymic hydrolysis of triglycerides. The method requires only 10-50 microliters milk, thus presenting a possible technique for work with small mammals, and is suitable for use with autoanalysers, permitting rapid sample throughput. 相似文献
27.
Describes the Drug Abuse Reporting Program, the 1st national evaluation study of community-based treatment programs, implemented in the early 1970s. It evolved into a 20-yr longitudinal research program that included during-treatment assessments of client performance, evaluations of treatment effectiveness based on outcomes in the years immediately following treatment, and long-term studies of addiction careers. The Treatment Outcome Prospective Study began in the early 1980s and is now being followed by the Drug Abuse Treatment Outcome Study in the 1990s. These multisite and multimodality studies have helped establish broad-based evidence for treatment efficacy and directions for new studies in the US. The AIDS crisis has had the effect of sharply increasing federal research funds, including grants allocated to enhance and evaluate psychosocial intervention programs for drug users. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
28.
29.
Twenty mothers of preterm babies who had survived to 1 year old, were matched for age and parity of the mother and time of birth of the baby, with 20 mothers delivering fullterm. Bone mineral, body composition and anthropometric measurements were obtained for each mother and analysed using paired t-tests. The only significant difference (P < 0.01) between the groups was a lower fat-free mass in the preterm mothers calculated from skinfold thickness measurements. 相似文献
30.