全文获取类型
收费全文 | 2492篇 |
免费 | 6篇 |
专业分类
电工技术 | 12篇 |
化学工业 | 84篇 |
金属工艺 | 4篇 |
机械仪表 | 9篇 |
建筑科学 | 13篇 |
矿业工程 | 2篇 |
能源动力 | 6篇 |
轻工业 | 28篇 |
水利工程 | 9篇 |
无线电 | 34篇 |
一般工业技术 | 70篇 |
冶金工业 | 2123篇 |
原子能技术 | 7篇 |
自动化技术 | 97篇 |
出版年
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 6篇 |
2019年 | 5篇 |
2018年 | 8篇 |
2017年 | 4篇 |
2016年 | 6篇 |
2015年 | 10篇 |
2014年 | 6篇 |
2013年 | 21篇 |
2012年 | 9篇 |
2011年 | 27篇 |
2010年 | 13篇 |
2009年 | 14篇 |
2008年 | 18篇 |
2007年 | 21篇 |
2006年 | 17篇 |
2005年 | 16篇 |
2004年 | 9篇 |
2003年 | 17篇 |
2001年 | 10篇 |
2000年 | 7篇 |
1999年 | 73篇 |
1998年 | 712篇 |
1997年 | 405篇 |
1996年 | 271篇 |
1995年 | 143篇 |
1994年 | 97篇 |
1993年 | 122篇 |
1992年 | 13篇 |
1991年 | 18篇 |
1990年 | 38篇 |
1989年 | 34篇 |
1988年 | 19篇 |
1987年 | 15篇 |
1986年 | 14篇 |
1985年 | 16篇 |
1984年 | 10篇 |
1983年 | 12篇 |
1982年 | 11篇 |
1981年 | 23篇 |
1980年 | 13篇 |
1979年 | 8篇 |
1978年 | 12篇 |
1977年 | 42篇 |
1976年 | 85篇 |
1975年 | 10篇 |
1973年 | 3篇 |
1966年 | 3篇 |
1965年 | 2篇 |
排序方式: 共有2498条查询结果,搜索用时 0 毫秒
991.
B Delobel V Delannoy G Pini M Zapella M Tardieu L Vallée MF Croquette 《Canadian Metallurgical Quarterly》1998,80(3):273-280
BACKGROUND AND STUDY AIMS: Modern fine-caliber endoscopes enable clinicians to directly visualize the pancreatic duct. They allow intraductal manipulation under optical control. We tried to evaluate the additional diagnostic potential of pancreatoscopy in assessing inconclusive intraductal pancreatic changes. PATIENTS AND METHODS: We prospectively performed 20 pancreatoscopies in 18 patients with inconclusive ductal abnormalities that had been previously investigated by computed tomography (CT) scan, abdominal ultrasound and endoscopic retrograde cholangiopancreatography (ERCP). The CHF-BP 30 (Olympus Optical Co., Japan) endoscope with an outer diameter of 3.1 mm and an instrumentation channel of 1.2 mm was used. Biopsies, cytological brushing and fluid collection were carried out, and the site of ductal abnormality was visualized. Endoscopic sphincterotomy (EST) was carried out in every patient prior to insertion of the pancreatoscope. RESULTS: Seven intraductal tumors were histologically confirmed, i.e. five intraductal papillary mucinous tumors and two adenocarcinomas. Benign appearance of the intraductal lesion plus negative histopathological examinations were confirmed by a follow-up of two years in eight patients. Five had chronic pancreatitis, and a further three had pancreatitis with strictures, blood clot obstruction, and idiopathic benign stricture, respectively. There were no complications with the exception of one bleeding episode after EST; no pancreatitis occurred. CONCLUSIONS: Pancreatoscopy is of diagnostic value in addition to CT, transabdominal ultrasound and ERCP in the differential diagnosis of poorly defined pancreatic lesions, particularly when assessing alterations of the ductal caliber without parenchymatous lesions. 相似文献
992.
Gabi Steinbach Cristian Crisan Siu Lung Ng Brian K. Hammer Peter J. Yunker 《Journal of the Royal Society Interface》2020,17(173)
Bacterial communities are governed by a wide variety of social interactions, some of which are antagonistic with potential significance for bacterial warfare. Several antagonistic mechanisms, such as killing via the type VI secretion system (T6SS), require killer cells to directly contact target cells. The T6SS is hypothesized to be a highly potent weapon, capable of facilitating the invasion and defence of bacterial populations. However, we find that the efficacy of contact killing is severely limited by the material consequences of cell death. Through experiments with Vibrio cholerae strains that kill via the T6SS, we show that dead cell debris quickly accumulates at the interface that forms between competing strains, preventing physical contact and thus preventing killing. While previous experiments have shown that T6SS killing can reduce a population of target cells by as much as 106-fold, we find that, as a result of the formation of dead cell debris barriers, the impact of contact killing depends sensitively on the initial concentration of killer cells. Killer cells are incapable of invading or eliminating competitors on a community level. Instead, bacterial warfare itself can facilitate coexistence between nominally antagonistic strains. While a variety of defensive strategies against microbial warfare exist, the material consequences of cell death provide target cells with their first line of defence. 相似文献
993.
Jacob Hammer 《International journal of control》2013,86(7):643-656
The problem of optimizing the efficiency of large capacity communication networks is considered. An important objective is to reduce the effects of traffic uncertainties on network efficiency, especially in cases where statistical models of the traffic uncertainties are not available. The main result is the development of algorithms for adjusting the data flow of each network customer so as to optimize network efficiency. It is shown that, in some common situations, the use of feedback control makes it possible to eliminate completely the effects of traffic uncertainties on network efficiency, despite the lack of statistical models. 相似文献
994.
Jacob Hammer 《International journal of control》2013,86(3):307-331
The problem of controlling a sequential machine under the influence of disturbances is considered. A methodology is developed for the design of controllers that guarantees that the effect of a 'small' disturbance on the performance of the controlled machine remains 'small'. The methodology is based on a theory of fraction representations of sequential machines reminiscent of the general theory of fraction representations of nonlinear systems. 相似文献
995.
LS Coles P Diamond F Occhiodoro MA Vadas MF Shannon 《Canadian Metallurgical Quarterly》1996,24(12):2311-2317
The human granulocyte-macrophage colony stimulating factor (GM-CSF) gene promoter binds a sequence-specific single-strand DNA binding protein termed NF-GMb. We previously demonstrated that the NF-GMb binding sites were required for repression of tumor necrosis factor-alpha (TNF-alpha) induction of the proximal GM-CSF promoter sequences in fibroblasts. We now describe the isolation of two different cDNA clones that encode cold shock domain (CSD) proteins with NF-GMb binding characteristics. One is identical to the previously reported CSD protein dbpB and the other is a previously unreported variant of the dbpA CSD factor. This is the first report of CSD factors binding to a cytokine gene. Nuclear NF-GMb and expressed CSD proteins have the same binding specificity for the GM-CSF promoter and other CSD binding sites. We present evidence that CSD factors are components of the nuclear NF-GMb complex. We also demonstrate that overexpression of the CSD proteins leads to complete repression of the proximal GM-CSF promoter containing the NF-GMb/CSD binding sites. Surprisingly, we show that CSD overexpression can also directly repress a region of the promoter which apparently lacks NF-GMb/CSD binding sites. NF-GMb/CSD factors may hence be acting by two different mechanisms. We discuss the potential importance of CSD factors in maintaining strict regulation of the GM-CSF gene. 相似文献
996.
R Whelpton AT Michael-Titus RP Jamdar K Abdillahi MF Grahn 《Canadian Metallurgical Quarterly》1996,63(6):885-891
The biodistribution and excretion of temoporfin (tetra[m-hydroxyphenyl]chlorin, m-THPC), a recently developed photosensitizer, was investigated in BALB/c mice. [14C]temoporfin was administered intravenously (0.73 mumol/kg) to tumor-free mice or to mice implanted with the Colo 26 colorectal carcinoma. Blood, tissue and fecal samples were collected for 35 days and 10 days postdose from tumor-free mice and tumor-bearing mice, respectively. Blood concentrations fell rapidly such that at later time points they were indistinguishable from background counts. Tumor concentrations rose to a peak of 0.34 microgram temoporfin equivalents/mL at 2 days and then declined in parallel (log plot) with the blood concentrations. Tumor: tissue ratios at 2 days for skin, adipose tissue and skeletal muscle underlying the tumor were 1.5, 2.3 and 3.8, respectively. By 4 days the corresponding values were 1.6, 3.4 and 4.0. Nearly 40% of the administered radioactivity was excreted in the feces in the first 24 h and more than 80% had been excreted by 20 days. Less than 0.2% of the dose was recovered from the urine. An elimination half-life of 10-12 days was calculated from the excretion data. 相似文献
997.
998.
Criticizes the validity of the D. Smith and F. Dumont study (see record 1995-34868-001) of unwarranted interpretations of the Draw A Person test, describing the study as a built-in setup that tricks its participants rather than being a sensible test of the authors' hypothesis. The author offers a more refined and ethical procedure aimed at achieving the study's purpose. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
999.
The purpose of this study was to determine whether proliferative activity is a prognostic factor in ovarian clear cell adenocarcinoma. The paraffin-embedded sections from eight cases of ovarian clear cell adenocarcinoma were immunostained with monoclonal antibody MIB1 using microwave oven heating for antigen retrieval. The difference in survival (Kaplan-Meier) between patients with high and low MIB1 expression was estimated with the generalized Wilcoxon test. MIB1 positivity ranged from 1.80 to 27.12% with a mean of 11.43%. A cutoff point of 10% dichotomized patients into two groups. The survival of high (> or = 10%) expressing tumors was worse than that of low (< 10%) expressing tumors (p < 0.05). MIB1 immunostaining may have useful prognostic value in ovarian clear cell adenocarcinoma. 相似文献
1000.
The susceptibility of 64 Malassezia furfur isolates to Melaleuca alternifolia oil was determined. The minimum inhibitory concentration for 90% of isolates was 0.25% by agar dilution and 0.12% by broth dilution. These data indicate that tea tree oil may be useful in the treatment of skin conditions involving M. furfur. 相似文献