全文获取类型
收费全文 | 4550篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 11篇 |
金属工艺 | 10篇 |
机械仪表 | 1篇 |
建筑科学 | 1篇 |
轻工业 | 11篇 |
无线电 | 1篇 |
一般工业技术 | 3篇 |
冶金工业 | 4504篇 |
原子能技术 | 2篇 |
自动化技术 | 5篇 |
出版年
2017年 | 1篇 |
2013年 | 3篇 |
2012年 | 2篇 |
2011年 | 9篇 |
2010年 | 1篇 |
2009年 | 2篇 |
2008年 | 2篇 |
2006年 | 2篇 |
2005年 | 4篇 |
2004年 | 2篇 |
2003年 | 6篇 |
2002年 | 2篇 |
1999年 | 152篇 |
1998年 | 1355篇 |
1997年 | 737篇 |
1996年 | 508篇 |
1995年 | 264篇 |
1994年 | 237篇 |
1993年 | 252篇 |
1992年 | 35篇 |
1991年 | 73篇 |
1990年 | 60篇 |
1989年 | 85篇 |
1988年 | 71篇 |
1987年 | 64篇 |
1986年 | 68篇 |
1985年 | 53篇 |
1983年 | 4篇 |
1982年 | 16篇 |
1981年 | 27篇 |
1980年 | 48篇 |
1979年 | 2篇 |
1978年 | 10篇 |
1977年 | 121篇 |
1976年 | 265篇 |
1975年 | 5篇 |
1955年 | 3篇 |
排序方式: 共有4551条查询结果,搜索用时 0 毫秒
41.
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
42.
43.
Chicken carcasses from a supermarket and from a poultry abattoir were examined using methods designed to isolate as many strains of campylobacters and related organisms as possible. Strains of arcobacter, but no campylobacters, were isolated from every carcass after enrichment. Campylobacter jejuni subsp. jejuni was isolated from all carcasses examined by direct plating and other Campylobacter-like strains were isolated from nine out of 15 abattoir carcasses by direct plating but not after enrichment. Only the Camp. jejuni subsp. jejuni strains could be identified to species level using a readily available identification scheme and/or a commercial identification kit. Examination of caecal contents from the 15 abattoir poultry yielded Camp. jejuni subsp. jejuni and Campylobacter-like strains from 15 and eight by direct plating, and from six and nine after enrichment, respectively. Four sites in the intestine of the abattoir birds (60 samples) were examined for arcobacters and only one strain was isolated. This indicates that arcobacters are probably not normal inhabitants of the poultry intestine. Poultry is a rich source of other campylobacteria besides the thermophilic Campylobacter spp. 相似文献
44.
45.
46.
47.
48.
We describe three case reports of hematomas in the abdominal wall muscles and discuss etiology, diagnostic findings and treatment. Abdominal wall hematomas are uncommon, and the condition is often misdiagnosed. One of our patients was laparotomised owing to suspected appendicitis, and one patient presented a tuberculous abscess that may have been an infected hematoma. Ultrasonographic examination or CT gives the correct diagnose. Conservative management is the treatment of choice unless bleeding is severe or the course is complicated by infection. 相似文献
49.
PE McAndrew A Frostholm JE Evans D Zdilar D Goldowitz IM Chiu AH Burghes A Rotter 《Canadian Metallurgical Quarterly》1998,391(4):444-455
50.
Effects of the intermediate retinoid metabolite retinal on the pattern of the dental lamina in vitro
Retinoids have important roles in pattern formation during embryonic development and might act as endogenous morphogens. They are necessary for normal odontogenesis and excess retinol alters the pattern of odontogenesis producing supernumerary buds of the dental lamina in the diastema region of the mouse mandible. Because the metabolism of retinoids in the developing mandible is unknown, the effects of retinal (an intermediate metabolite in the local conversion of retinol to retinoic acid) on the patterning of odontogenesis were examined. Retinal produces supernumerary buds and enhanced epithelial proliferation in day-9 mandibles in vitro. The endogenous levels of retinal in the mandible at the time of initiation of odontogenesis were also measured by high-performance liquid chromatography. Retinal was detected only at day 10 and not at later stages of development. Local metabolism of this intermediate retinoid may be a rate-determining step in the production of active retinoid metabolites that may control the pattern of the dentition, which is established at the time of the appearance of the dental lamina at embryonic day 12. 相似文献