首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2627篇
  免费   0篇
化学工业   4篇
轻工业   4篇
水利工程   1篇
一般工业技术   3篇
冶金工业   2612篇
自动化技术   3篇
  2021年   1篇
  2019年   2篇
  2015年   1篇
  2008年   1篇
  2007年   1篇
  2006年   1篇
  2004年   1篇
  2003年   3篇
  1999年   75篇
  1998年   874篇
  1997年   501篇
  1996年   256篇
  1995年   166篇
  1994年   151篇
  1993年   164篇
  1992年   10篇
  1991年   19篇
  1990年   19篇
  1989年   33篇
  1988年   29篇
  1987年   21篇
  1986年   21篇
  1985年   22篇
  1983年   5篇
  1982年   12篇
  1981年   16篇
  1980年   22篇
  1978年   3篇
  1977年   55篇
  1976年   137篇
  1975年   2篇
  1955年   2篇
  1954年   1篇
排序方式: 共有2627条查询结果,搜索用时 0 毫秒
41.
42.
The third documented case of primary squamous cell carcinoma of the urachus in the English literature is reported. The interesting coincidental occurrence of the dermoid cyst of the right ovary and a complete longitudinal septum of the vagina and uterine cervix is described.  相似文献   
43.
Thirty-eight patients diagnosed as having continuous schizophrenia progrediens, 35 patients with shift-like schizophrenia and six patients with hypertoxic (feverish) schizophrenia were studied. The examinees displayed a marked increase in the blood content of lipid peroxidation products, such as malonic dialdehyde and conjugated dienes, together with an enhancement of the degree of erytrocytolysis, which events are particularly noticeable in hypertoxic- and continuous schizophrenia. Blood catalase activity gets higher, that of superoxide dismutase is on the decrease, which facts suggest to us some faults in the system of antioxidant defence.  相似文献   
44.
Isolated reaction centers (RCs) from Rhodobacter sphaeroides were found to bind Zn(II) stoichiometrically and reversibly in addition to the 1 equiv of non-heme Fe(II). Metal and EPR analyses confirm that Zn(II) is ligated to a binding site that is distinct from the Fe site. When Zn(II) is bound to this site, electron transfer between the quinones QA and QB (QA-QB --> QAQB-) is slowed and the room-temperature kinetics become distributed across the microsecond to millisecond time domain. This effect of metal binding on the kinetics is similar to the more global effect of cooling RCs to 2 degreesC in the absence of Zn(II). This suggests that Zn(II) binding alters localized protein motions that are necessary for rapid QA-QB --> QAQB- electron transfer. Inspection of the RC crystal structure suggests a cluster of histidine ligands located beneath the QB binding pocket as a potential binding site.  相似文献   
45.
46.
47.
Mechanism of suppression of cell-mediated immunity by measles virus   总被引:2,自引:0,他引:2  
The mechanisms underlying the profound suppression of cell-mediated immunity (CMI) accompanying measles are unclear. Interleukin-12 (IL-12), derived principally from monocytes and macrophages, is critical for the generation of CMI. Measles virus (MV) infection of primary human monocytes specifically down-regulated IL-12 production. Cross-linking of CD46, a complement regulatory protein that is the cellular receptor for MV, with antibody or with the complement activation product C3b similarly inhibited monocyte IL-12 production, providing a plausible mechanism for MV-induced immunosuppression. CD46 provides a regulatory link between the complement system and cellular immune responses.  相似文献   
48.
49.
In 1957 California began placing responsibility for public mental health services on county programs still vary widely in emphasis and size. The authors explored determinants of counties' unequal program developments using per capita expenditures as the measure of county services. Sociodemographic variables that help explain states' social program expenditures correlate weakly or not at all with county mental health expenditures. The most powerful predictor of these expenditures is number of psychiatrists per 10,000 population. Equal per capita expenditures, however, are not a reasonable goal; these can mask wide variations in program content, efficiency, and quality of care.  相似文献   
50.
Sexual coercion, a topic of relevance to school health personnel, may be as common in high school populations as in university populations. Twenty-one sexuality education curricula were examined for information on the topics of date rape, stranger rape, pressure, incest, sexual harassment, unwanted/inappropriate touch, and exploitation/victimization. Curricula scoring highest in total coverage also were the most comprehensive with six of the seven sexual coercion topics covered. Overall, pressure and exploitation/victimization received the greatest attention, while sexual harassment was not covered in any of the curricula. Common themes occurring within the coercion topic areas included guilt, communication/assertiveness skills, blame, drug use, premeditation, fear, sources of help. Results suggest sexuality education curricula have not responded to the increased concern regarding sexual harassment in schools.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号