全文获取类型
收费全文 | 4099篇 |
免费 | 15篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 1篇 |
综合类 | 1篇 |
化学工业 | 52篇 |
金属工艺 | 1篇 |
机械仪表 | 21篇 |
建筑科学 | 34篇 |
能源动力 | 32篇 |
轻工业 | 48篇 |
水利工程 | 5篇 |
无线电 | 55篇 |
一般工业技术 | 114篇 |
冶金工业 | 3638篇 |
原子能技术 | 7篇 |
自动化技术 | 108篇 |
出版年
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 2篇 |
2018年 | 5篇 |
2017年 | 6篇 |
2016年 | 4篇 |
2015年 | 9篇 |
2014年 | 9篇 |
2013年 | 35篇 |
2012年 | 25篇 |
2011年 | 23篇 |
2010年 | 25篇 |
2009年 | 24篇 |
2008年 | 28篇 |
2007年 | 31篇 |
2006年 | 24篇 |
2005年 | 22篇 |
2004年 | 24篇 |
2003年 | 19篇 |
2002年 | 15篇 |
2001年 | 16篇 |
2000年 | 10篇 |
1999年 | 146篇 |
1998年 | 1200篇 |
1997年 | 633篇 |
1996年 | 435篇 |
1995年 | 213篇 |
1994年 | 205篇 |
1993年 | 200篇 |
1992年 | 52篇 |
1991年 | 40篇 |
1990年 | 53篇 |
1989年 | 48篇 |
1988年 | 48篇 |
1987年 | 45篇 |
1986年 | 46篇 |
1985年 | 50篇 |
1984年 | 4篇 |
1983年 | 16篇 |
1982年 | 21篇 |
1981年 | 20篇 |
1980年 | 33篇 |
1979年 | 3篇 |
1978年 | 8篇 |
1977年 | 58篇 |
1976年 | 137篇 |
1975年 | 12篇 |
1974年 | 5篇 |
1972年 | 4篇 |
1967年 | 2篇 |
排序方式: 共有4117条查询结果,搜索用时 0 毫秒
21.
The experience of our 16 patients treated for membranous duodenal stenosis is reported. Their treatment and course was analysed in a retrospective study. Eight patients were operated on within the first 16 days of life and in the remaining group surgery was performed at 1 month to 4 y of age. The presenting symptom leading to diagnosis was, in all but one case, non-bile-stained vomiting. Associated malformations were found in all but four patients, mostly morbus Down. The operative procedure performed was a partial excision of the duodenal membrane and a duodenoplasty in 10 patients, a duodenojejunostomy in 5 patients, and a duodenoplasty only in 1 patient. The postoperative course was without lethal complications. One late stricture in an anastomosis occurred. We conclude that in its presentation, duodenal stenosis differs from duodenal atresia, and can often be misinterpreted, resulting in a late diagnosis, and should be reported as a separate entity. 相似文献
22.
23.
24.
This paper investigates the effect of the waterproofing sleeve on the calibration of kilovoltage photon beams (50-300 kV). The sleeve effect correction factor, ps has been calculated using the Monte Carlo method as the ratios of the air kerma in an air cavity of a cylindrical chamber without the waterproofing sleeve to that with a sleeve. Three sleeve materials have been studied, PMMA, nylon and polystyrene. The calculations were carried out using the EGS4 (Electron Gamma Shower version 4) code system with the application of a correlated-sampling variance-reduction technique. The results show that the sleeve correction factor for 1-mm thick nylon and polystyrene sleeves, ps varies from 0.992 to 1.000 and from 0.981 to 1.000, respectively, for the same beam quality range. The ps factor varies with sleeve thickness, beam quality and phantom depth. No significant dependence of the ps factor on field size and source-surface distance has been found. Measurements for PMMA, nylon and polystyrene sleeves of various thicknesses have also been carried out and show excellent agreement with Monte Carlo calculations. 相似文献
25.
MG Narducci L Virgilio JB Engiles AM Buchberg L Billips A Facchiano CM Croce G Russo JL Rothstein 《Canadian Metallurgical Quarterly》1997,15(8):919-926
In human leukemias and lymphomas nonrandom chromosomal rearrangements cause changes in cell growth and/or survival in such a way as to promote malignancy. The detailed study of the biochemical and genetic pathways altered in human cancer requires the identification or development of models to allow the study and manipulation of cancer gene function. Recently, the breakpoint gene TCL1, involved in chromosome translocations observed mostly in mature T-cell proliferations and chronic lymphocytic leukemias (CLL), was isolated and characterized, and showed to be part of a new gene family of proteins involved in these tumors. The murine Tcl1 gene, is similar in sequence to the murine and human MTCP1 gene also involved in T cell leukemias. The murine Tcl1 gene was shown to reside on mouse chromosome 12 in a region syntenic to human chromosome 14. Furthermore, we show that the murine Tcl1 gene is expressed early in mouse embryonic development and demonstrates expression in fetal hematopoietic organs as well as in immature T and B cells. Characterization of the murine Tcl1 gene will help in developing a mouse model of CLL and would provide the best opportunity to study and decipher the role of TCL1 in malignant transformation. 相似文献
26.
27.
CM Newton 《Canadian Metallurgical Quarterly》1993,26(4):327-343
GRIFFIN (graphics investigation of familial information), an interactive graphics system for exploratory investigation of data on individuals associated by familial relationships, was designed to provide genetic epidemiologists a flexible, rapidly responsive tool for viewing and guiding exploration of complex databases in the context of familiar pedigree structures. It graphically portrays both categorical and multivariate scalar data on individuals in those structures. The display can be inverted to show all ancestors and descendants of any individual the user designates. It provides cues to censored information when bushy pedigrees cannot be fully displayed without sacrificing legibility. These guide users on where to next invert the system. Investigators may translate/zoom the display, vary the mode of representing data, point to individuals to obtain displays of alphameric information about them, etc. Developed in Fortran using IBM's GDDM graphics subroutines for an IBM 3090 mainframe, GRIFFIN's design anticipates porting to smaller systems. 相似文献
28.
Lonigan Christopher J.; Carey Michael P.; Finch A. J. 《Canadian Metallurgical Quarterly》1994,62(5):1000
Self-reported depression and anxiety were examined in 233 inpatient children (aged 6–17 yrs) diagnosed with either an anxiety disorder or a depressive disorder. Depressed children reported more problems related to a loss of interest and low motivation, and they had a more negative view of themselves. Anxious children reported more worry about the future, their well-being, and the reactions of others. The groups did not differ in the degree of depressed affect reported in terms of being sad, lethargic, bothered by things, or feeling alone and isolated. Findings suggest that a general negative affectivity component is common to both anxiety and depression disorders and measures. Results demonstrate that anxiety and depression in children have distinguishing features that can be measured by common self-report instruments, and the findings indicate that one factor that may distinguish between anxiety and depression in children is positive affectivity. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
29.
Intraneural injection of 10-20 x 10(6) viable Mycobacterium leprae into the sciatic nerve of normal, unsensitized, Swiss white mice gives rise to a tuberculoid type of granulomatous response in 2 weeks. The same dose of viable M. leprae when injected into the sciatic nerves of unsensitized immunosuppressed mice (T200 x 5R) elicited a macrophage response. When macrophages were systemically immobilized using an intraperitoneal injection of silica quartz dust in normal mice, the lesion produced was of the lepromatous type, suggesting a role for the macrophage in the induction of the tuberculoid type of granulomatous response. In all of these in situ experiments, M. leprae failed to enter the Schwann cells. 相似文献
30.
The Drosophila developmental mutation quartet causes late larval lethality and small imaginal discs and, when expressed in the adult female, has a lethal effect on early embryogenesis. These developmental defects are associated with mitotic defects, which include a low mitotic index in larval brains and incomplete separation of chromosomes in mitosis in the early embryo. quartet mutations also have a biochemical effect, i.e., a basic shift in isoelectric point in three proteins. We have purified one of these proteins, raised an antibody to it, and isolated and sequenced its cDNA. At the amino acid level, the sequence shows 68% identity and 81% similarity to bovine smg p25a GDP dissociation inhibitor (GDI), a regulator of ras-like small GTPases of the rab/SEC4/YPT1 subfamily. The correlation between a basic shift in isoelectric point in Drosophila GDI in quartet mutant tissue and the quartet developmental phenotype raises the possibility that a posttranslational modification of GDI is necessary for its function and that GDI function is essential for development. 相似文献