全文获取类型
收费全文 | 3817篇 |
免费 | 4篇 |
专业分类
电工技术 | 1篇 |
综合类 | 2篇 |
化学工业 | 11篇 |
轻工业 | 4篇 |
无线电 | 1篇 |
一般工业技术 | 7篇 |
冶金工业 | 3789篇 |
自动化技术 | 6篇 |
出版年
2021年 | 1篇 |
2019年 | 1篇 |
2017年 | 2篇 |
2016年 | 1篇 |
2014年 | 1篇 |
2010年 | 1篇 |
2007年 | 2篇 |
2006年 | 4篇 |
2004年 | 1篇 |
2003年 | 5篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 134篇 |
1998年 | 1209篇 |
1997年 | 666篇 |
1996年 | 415篇 |
1995年 | 216篇 |
1994年 | 180篇 |
1993年 | 243篇 |
1992年 | 23篇 |
1991年 | 46篇 |
1990年 | 46篇 |
1989年 | 60篇 |
1988年 | 62篇 |
1987年 | 52篇 |
1986年 | 34篇 |
1985年 | 35篇 |
1983年 | 8篇 |
1982年 | 17篇 |
1981年 | 21篇 |
1980年 | 20篇 |
1979年 | 2篇 |
1978年 | 8篇 |
1977年 | 96篇 |
1976年 | 196篇 |
1975年 | 9篇 |
1974年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有3821条查询结果,搜索用时 0 毫秒
61.
62.
63.
JS Weissman JS Haas FJ Fowler C Gatsonis MP Massagli GR Seage P Cleary 《Canadian Metallurgical Quarterly》1999,19(1):16-26
In 1982, the World Health Organization (WHO) identified inadequate relief from cancer pain as an international health problem. WHO recommended that governments develop and implement national policies and programs for cancer pain relief. This report evaluates national health policy and the systems of health care delivery in relation to cancer pain management in the new South Africa. This field study included multiple methods of data collection: analysis of documents, field trips with participant observation in sites of care delivery, focused interviews, and in-depth interviews of key informants. The purposive sample of key informants (n = 33) represented multiple stakeholders in a variety of settings. Strengths of the developing health policy include specific recommendations related to palliative care; the shift to universal primary care; policies to support drug availability; the inclusion of morphine and codeine as essential drug at the primary health care level; and the development of a national standard related to cancer pain management. Health services are characterized by two parallel systems of care (private and public) with numerous vestiges of the inequities of apartheid. The management of pain varies by provider and setting; major problems with access exist in the rural areas. Health services in South Africa have been plagued by inequity and inadequate resources. New health policies have set a path to ensure universal access to health care including palliative care for cancer. Their successful implementation is the next necessary step toward improving health services and alleviating the suffering of increasing numbers of individuals with cancer. 相似文献
64.
65.
BACKGROUND: Dehydroepiandrosterone (DHEA) is among the most abundant steroids in the human body and appears to have diverse biochemical activities. This multifunctional hormone has long been a compound of interest to research psychiatrists. Its recent promotion and availability as an over-the-counter supplement to the general public has led to widespread use. Little is known about potential adverse effects of DHEA when consumed on an acute or chronic basis. We report a case of mania in an older man acutely admitted to our psychiatric facility with no previous personal or family history of bipolar disorder that appeared to be related to recent DHEA use. The patient had initiated DHEA use 6 months prior to admission and was taking 200-300 mg/day at the time of presentation. METHODS: He was treated with valproic acid 500 mg twice daily. RESULTS: The patient showed sufficient improvement to be discharged following a 7-day inpatient hospitalization. CONCLUSIONS: A wide range of medications have been associated with the induction of hypomania and mania, and we have provided a brief discussion of the potential for DHEA to trigger manic symptoms. 相似文献
66.
JS Kim I Lopez PL DiPatre F Liu A Ishiyama RW Baloh 《Canadian Metallurgical Quarterly》1999,52(1):40-44
Immunocytochemical examination for mitochondrial protein and cytochrome oxidase was performed to demonstrate oncocytes in normal adenohypophysis obtained from 28 patients of various age. A small number of solitary large epithelial cells showed intense cytoplasmic granular immunoreactivities for mitochondrial protein and cytochrome oxidase. The proportions of the cells positive for the former and the latter ranged from 0% to 5.9% (mean+/-SD; 1.5+/-1.7%) and from 0% to 4.9% (1.4+/-1.6%), respectively. These cells were either absent or extremely rare in young patients (under 10 years) but tended to increase in number with age (P < 0.0001). On the other hand, the mirror section technique showed that most of these cells were negative for adenohypophysial hormones, but a few of them were faintly positive for: alpha-subunit (8.0%), beta-subunits of follicle-stimulating hormone (4.8%), luteinizing hormone (2.5%), thyroid-stimulating hormone (1.0%), and growth hormone (0.5%), and were negative for prolactin and adrenocorticotropic hormone. We considered that these cells represent oncocytes that exist in varying numbers in normal adenohypophysis. It was suggested that oncocytes in normal adenohypophysis share various common features with tumorous oncocytes of pituitary oncocytomas. 相似文献
67.
GH Posner MH Parker J Northrop JS Elias P Ploypradith S Xie TA Shapiro 《Canadian Metallurgical Quarterly》1999,42(2):300-304
In only three chemical operations, natural trioxane lactone artemisinin (1) was converted into a series of C-10 carbon-substituted 10-deoxoartemisinin compounds 4-9. The three steps involved lactone reduction, replacement of the anomeric lactol OH by F using diethylaminosulfur trifluoride, and finally boron trifluoride-promoted substitution of F by aryl, heteroaryl, and acetylide nucleophiles. All of these C-10 nonacetal, chemically robust, enantiomerically pure compounds 4-9 have high antimalarial potencies in vitro against Plasmodium falciparum malaria parasites, and furans 5a and 5b and pyrrole 7a are antimalarially potent also in vivo even when administered to rodents orally. 相似文献
68.
69.
70.