全文获取类型
收费全文 | 746篇 |
免费 | 18篇 |
专业分类
电工技术 | 9篇 |
综合类 | 1篇 |
化学工业 | 70篇 |
金属工艺 | 1篇 |
机械仪表 | 5篇 |
建筑科学 | 25篇 |
矿业工程 | 2篇 |
能源动力 | 19篇 |
轻工业 | 93篇 |
水利工程 | 1篇 |
无线电 | 67篇 |
一般工业技术 | 70篇 |
冶金工业 | 288篇 |
自动化技术 | 113篇 |
出版年
2023年 | 5篇 |
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 14篇 |
2019年 | 10篇 |
2018年 | 8篇 |
2017年 | 12篇 |
2016年 | 12篇 |
2015年 | 7篇 |
2014年 | 10篇 |
2013年 | 19篇 |
2012年 | 23篇 |
2011年 | 25篇 |
2010年 | 28篇 |
2009年 | 23篇 |
2008年 | 27篇 |
2007年 | 23篇 |
2006年 | 32篇 |
2005年 | 25篇 |
2004年 | 20篇 |
2003年 | 20篇 |
2002年 | 23篇 |
2001年 | 11篇 |
2000年 | 21篇 |
1999年 | 30篇 |
1998年 | 54篇 |
1997年 | 34篇 |
1996年 | 24篇 |
1995年 | 21篇 |
1994年 | 19篇 |
1993年 | 22篇 |
1992年 | 11篇 |
1991年 | 14篇 |
1990年 | 9篇 |
1989年 | 13篇 |
1988年 | 18篇 |
1987年 | 9篇 |
1986年 | 14篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1971年 | 2篇 |
1939年 | 2篇 |
1938年 | 2篇 |
排序方式: 共有764条查询结果,搜索用时 15 毫秒
71.
Many herpesviruses attach to cells in a two-step process, using the glycoprotein gC family of homologs to bind the primary receptor, heparan sulfate (HS) proteoglycan, and glycoprotein gD homologs to bind an unknown secondary receptor. We have previously shown by deletion analysis that the amino-terminal one-third of gC from pseudorabies virus (PRV), a swine herpesvirus, includes at least the principal HS receptor-binding domain. This portion of PRV gC contains three discrete clusters of basic residues that exactly or nearly match proposed consensus sequences for heparin-binding domains (HBDs); four additional potential HBDs lie in the distal two-thirds of the glycoprotein. We now specifically implicate each of the three amino-terminal HBDs in virus attachment. Mutational analysis demonstrated that any one of the three HBDs could mediate efficient virus infectivity; HS-dependent PRV attachment to cells was eliminated only after all three amino-terminal HBDs were altered. Furthermore, the binding dysfunction was due to a disruption of the specific HBDs and not to total charge loss. Thus, unlike previously described viral receptor-binding domains, the PRV gC receptor-binding domain is composed of multiple, discrete units that can function independently of one another. These units may function redundantly either to increase binding affinity or perhaps to effectively increase the virus's host range. 相似文献
72.
Tara J Fano Sheila M Tyminski Mary A T Flynn 《Revue canadienne de la pratique et de la recherche en diététique》2004,65(2):72-80
To evaluate the impact of the Calgary Health Region Collective Kitchen Program on various Population Health Promotion Model health determinants, data were collected through mail-in questionnaires that examined the members' (n=331) and coordinators' (n=58) perspectives of the program. Seventy-nine members (24%) and 26 coordinators (45%) were included in the study. Three incomplete questionnaires (from prenatal program members) were discarded. Sixty-one percent of members who reported income level and family size (n=61) had incomes below the low-income cut-off. Fifty-eight members (73%) reported improvements in their lives because of the program. Sixty-four members (81%) perceived they learned to feed their families healthier foods. The members reported their fruit and vegetable consumption before and since joining a collective kitchen, and the proportion of those consuming at least five fruit and vegetable servings a day rose from 29% to 47%. The most common reasons for joining this program concerned social interactions and support. Over 90% of the coordinators perceived that they were competent to coordinate a kitchen. The results indicate that the collective kitchens program addresses several health determinants, and may increase members' capacity to attain food security and to achieve improved nutritional health. 相似文献
73.
74.
Consultants with experience of GP intrapartum care believe it is safe for the low-risk woman. However, GPs are perceived as lacking enthusiasm and as having varying degrees of obstetric expertise. Consultants feel that women themselves are not requesting more intrapartum care from GPs. 相似文献
75.
Dendritic cells (DC) play an essential role in the initiation of primary T cell responses to foreign Ag. It is likely that these potent APC are critical in the initiation of immune responses to pathogens, such as bacteria or parasites. However, little is known about the interaction of these important APC with pathogens. To address this issue, the interaction of the bacterium Mycobacterium tuberculosis with human DC was studied. DC generated from human peripheral blood by short term culture in medium containing recombinant human cytokines granulocyte-macrophage-CSF and IL-4 were capable of phagocytosing M. tuberculosis. Infection of DC with live M. tuberculosis bacilli resulted in increased APC surface expression of the costimulatory molecules CD54, CD40, and B7.1, as well as MHC class I molecules. In addition, infected DC secreted elevated levels of inflammatory cytokines, including TNF-alpha, IL-1, and IL-12. M. tuberculosis-infected human monocytes also secreted inflammatory cytokines, but exhibited no enhancement of costimulatory or MHC class I molecule expression. These data indicate that infection with M. tuberculosis results in the direct activation and maturation of these DC. In vivo, such activation may facilitate migration to the lymph nodes, and enhance presentation of Ag to T cells, thereby facilitating the induction of the immune response against this pathogen. 相似文献
76.
77.
The Design of a Human Memory Prosthesis 总被引:1,自引:0,他引:1
Lamming M.; Brown P.; Carter K.; Eldridge M.; Flynn M.; Louie G.; Robinson P.; Sellen A. 《Computer Journal》1994,37(3):153-163
78.
79.
Gallbladder hypokinesis is an uncommon condition and a potential etiologic factor in the formation of gallstones and the development of cholecystitis. It is associated with a number of different conditions, but gallbladder hypokinesia as a cause of small bowel obstruction is unreported. In the case presented below, we saw a postoperative partial upper small bowel obstruction due to hypokinesia of the gallbladder. The investigations, management, and subsequent recovery are described. A review of the literature failed to reveal any similar occurrence. 相似文献
80.