全文获取类型
收费全文 | 4657篇 |
免费 | 33篇 |
专业分类
电工技术 | 13篇 |
综合类 | 4篇 |
化学工业 | 139篇 |
金属工艺 | 15篇 |
机械仪表 | 22篇 |
建筑科学 | 27篇 |
矿业工程 | 1篇 |
能源动力 | 18篇 |
轻工业 | 157篇 |
水利工程 | 4篇 |
石油天然气 | 4篇 |
无线电 | 141篇 |
一般工业技术 | 106篇 |
冶金工业 | 3925篇 |
原子能技术 | 10篇 |
自动化技术 | 104篇 |
出版年
2021年 | 11篇 |
2020年 | 6篇 |
2019年 | 5篇 |
2018年 | 11篇 |
2017年 | 19篇 |
2016年 | 13篇 |
2015年 | 16篇 |
2014年 | 17篇 |
2013年 | 23篇 |
2012年 | 32篇 |
2011年 | 50篇 |
2010年 | 43篇 |
2009年 | 29篇 |
2008年 | 36篇 |
2007年 | 35篇 |
2006年 | 42篇 |
2005年 | 23篇 |
2004年 | 27篇 |
2003年 | 32篇 |
2002年 | 15篇 |
2001年 | 12篇 |
2000年 | 20篇 |
1999年 | 150篇 |
1998年 | 1217篇 |
1997年 | 681篇 |
1996年 | 474篇 |
1995年 | 241篇 |
1994年 | 202篇 |
1993年 | 239篇 |
1992年 | 49篇 |
1991年 | 75篇 |
1990年 | 76篇 |
1989年 | 64篇 |
1988年 | 64篇 |
1987年 | 71篇 |
1986年 | 39篇 |
1985年 | 51篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 26篇 |
1981年 | 32篇 |
1980年 | 37篇 |
1979年 | 14篇 |
1978年 | 15篇 |
1977年 | 90篇 |
1976年 | 209篇 |
1975年 | 8篇 |
1974年 | 4篇 |
1973年 | 6篇 |
1972年 | 4篇 |
排序方式: 共有4690条查询结果,搜索用时 0 毫秒
41.
42.
43.
The cytoskeletal components of hamster oocytes, zygotes, and spontaneously activated parthogenotes were examined after immunocytochemical labeling. Microtubules were found only in the anastral, tangentially arranged second meiotic spindle of unfertilized oocytes. Taxol treatment of unfertilized oocytes greatly augmented astral microtubules in both the metaphase II spindle and the cortex. Disruption of the meiotic spindle microtubules with nocodazole resulted in cortical chromosomal scattering. During hamster sperm incorporation and pronuclear formation, no sperm aster was detected in association with the male DNA. Instead, a large overlapping array of microtubules assembled in the cortex. By mitosis, this interphase array disassembled and an anastral metaphase spindle formed. Microtubule and chromatin configurations were also imaged in hamster oocytes injected with human sperm. Astral microtubules were absent from the sperm centrosome. The implications of these results are discussed in relation to the hamster oocyte penetration assay, a test commonly used by in vitro fertilization clinics to demonstrate the fertilizing ability of human sperm. We conclude that since hamsters and humans follow different methods of centrosome inheritance, maternal and paternal, respectively, the hamster may be an inappropriate model for exploring microtubule and centrosomal defects in humans or for assaying postinsemination forms of human male fertility defects. 相似文献
44.
Audiological tests were conducted on 34 patients before and after undergoing an operation in spinal anaesthesia. One of these patients developed a considerable unilateral hearing loss in the low-frequency range, which persisted until an epidural blood-patch was given. Unexpectedly, we also found a general small but significant threshold shift at 500 Hz, which has never before been described in the literature. The biological mechanism is discussed, and the results suggest that the explanation of the hearing loss could be a condition similar to endolymphatic hydrops, resulting from perilymphatic hypotension due to loss of liquor during and after the spinal anaesthesia. 相似文献
45.
DM Wyatt 《Canadian Metallurgical Quarterly》1993,23(7):32U, 32Y-32Z passim
46.
47.
48.
49.
DM Haig A Percival J Mitchell I Green D Sargan 《Canadian Metallurgical Quarterly》1995,45(3-4):221-236
An in vitro culture system is described which allows an analysis of the signals responsible for the survival, growth and functional maturation of afferent lymph dendritic cells (ALDC), a subpopulation of migrating dermal dendritic cells involved in antigen carriage and presentation to T-cells. Purified ALDC survived and grew for up to 30 days in lymph node conditioned medium and survived 14 days in recombinant ovine (rov) TNF-alpha whereas none were detected after 24 h in rov GM-CSF, rov IFN-gamma or rh M-CSF. However, when rov GM-CSF was added to cultures along with rov TNF-alpha, increased numbers of ALDC compared with input numbers (growth) were recorded on Days 14 and 21. In contrast, when 50-200 units ml-1 of rov IFN-gamma were added to cultures of ALDC along with TNF-alpha or rov TNF-alpha plus rov GM-CSF, cell survival and growth was inhibited. Antibody blocking studies confirmed the cytokine specificity of these effects. ALDC cultured in rov TNF-alpha or rov TNF-alpha plus rov GM-CSF retained MHC Class-II and ov CD-1 antigen expression and accessory function for autologous ov CD-4 T-cell proliferation, although at reduced levels compared with freshly isolated cells. Neither fresh nor cultured ALDC expressed coagulation factor XIIIa. 相似文献
50.