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   10264篇
  免费   1篇
电工技术   3篇
化学工业   39篇
机械仪表   3篇
建筑科学   7篇
轻工业   12篇
水利工程   3篇
石油天然气   2篇
无线电   5篇
一般工业技术   10篇
冶金工业   10167篇
原子能技术   1篇
自动化技术   13篇
  2019年   1篇
  2017年   1篇
  2016年   2篇
  2015年   1篇
  2013年   5篇
  2012年   2篇
  2011年   2篇
  2010年   2篇
  2009年   3篇
  2008年   4篇
  2007年   2篇
  2006年   6篇
  2005年   5篇
  2004年   5篇
  2003年   14篇
  2002年   1篇
  2000年   5篇
  1999年   292篇
  1998年   3304篇
  1997年   1926篇
  1996年   1175篇
  1995年   661篇
  1994年   527篇
  1993年   627篇
  1992年   64篇
  1991年   129篇
  1990年   108篇
  1989年   122篇
  1988年   133篇
  1987年   98篇
  1986年   87篇
  1985年   60篇
  1984年   3篇
  1983年   12篇
  1982年   50篇
  1981年   49篇
  1980年   68篇
  1979年   3篇
  1978年   23篇
  1977年   192篇
  1976年   460篇
  1975年   13篇
  1974年   2篇
  1965年   3篇
  1962年   1篇
  1955年   8篇
  1954年   4篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
In head injured patients changes were found in the CSF levels of metabolites of the dopaminergic and the serotonergic neurotransmission (HVA and 5-HIAA). After the fifth day following trauma a significant decrease of the HVA levels in the lumbar CSF after probenecid treatment was found. The intensity of this decrease was found to be related to the severity of the trauma (period of unconsciousness), but not to the state of consciousness. Also the probenecid-induced 5-HIAA levels in conscious patients were decreased after the fifth post-traumatic day. In unconscious patients, the period of unconsciousness, particularly in the period of 5-20 days after trauma. Between 21 and 60 days after trauma the 5-HIAA concentrations in unconscious patients decreased remarkably, but they were still significantly higher than in the conscious patients. It can be concluded that during unconsciousness serotonergic neurons have a high rate of turnover, but that both neurotransmitter systems are damaged by the direct or indirect consequences of the injury.  相似文献   
72.
A case of primary retroperitoneal germinoma is presented in which markedly elevated serum lactic dehydrogenase levels were present before diagnosis, but declined to normal with abdominal irradiation. It is the first report of lactic dehydrogenase serving as a tumor marker in germinoma.  相似文献   
73.
74.
75.
Members of the immediate families of twenty children with specific reading disability were examined to determine the prevalence of reading disability within the families. A procedure was developed for identifying adults who may have compensated for a disability manifested more clearly in childhood. Forty-five percent of 75 first-degree relatives of the parents were affected and there was a significantly greater number of affected male relatives than females. No single mode of genetic transmission is evident after inspection of the pedigrees. It is suggested that the disorder is genetically heterogeneous and that subgroups of disabled readers should be looked for.  相似文献   
76.
Long-term low-dosage prophylaxis may be used in children with recurrent urinary tract infection to prevent reinfection of the urinary tract while the underlying cause of infection persists. Co-trimoxazole in a dose of 2 mg trimethoprin combined with 10 mg sulphamethoxazole per kg body weight daily has proved very effective: only six of 130 children receiving this treatment during a total period of 2637 months developed a reinfection. Co-trimoxazole was acceptable, compliance was good, and there were no important adverse effects. Supportive measures during prophylaxis are important. Sixty-five children were follow up after completion of their co-trimoxazole prophylaxis. Twenty-seven developed reinfections with fresh organisms, over two-thirds occurring within three months of discontinuing prophylaxis. Each one of these reinfections was sensitive to trimethoprin. The rectal flora were similarly sensitive.  相似文献   
77.
Vroom's (1964) expectancy theory model was used to predict older workers' choices between continued employment or immediate retirement. It was hypothesized that a person's preference for one of the two alternatives would be a function of the differences between the instrumentality of employment and the instrumentality of retirement for the attainment of outcomes, multiplied by the valence of each outcome, summed over outcomes. To test this, 290 Israeli male workers, aged 57 to 64, were interviewed. Measures included: preference for employment or retirement; valences of 35 outcomes; perceived instrumentalities of employment and retirement. The results supported the hypothesis (R = .40; p less than .01). It is suggested that further research along these lines could equip organizations with a tool for assisting older employees in the transition to retirement or for encouraging those who are still capable of making a significant contribution to remain employed.  相似文献   
78.
Percutaneous transfemoral arterial balloon occlusion or gelatin sponge embolization of the splenic artery or both were carried out in three high-risk patients with hepatic cirrhosis to reduce splenic hyperfunction and improve severe thrombocytopenia. Although this maneuver raised peripheral platelet counts in each patient, in one patient left upper quadrant pain with splinting of the lower chest cage led to hypostatic lower lobe pneumonia, while in another septic splentitis with gas-forming organisms necessitated splecectomy. Transfemoral occlusion of the splenic artery, although an effective, noninvasive approach to control splenic hyperfunction, has at the same time potential dangers that should be viewed with extreme caution in therapeutic application.  相似文献   
79.
1. The effects of intravenous (i.v.) administration of the vasodilator drugs prazosin or diazoxide on blood pressure and plasma renin activity were evaluated in the anaesthetized dog. 2. Prazosin and diazoxide both induced a rapid reduction in the mean arterial pressure to 73% and 75% of control values respectively. 3. Prazosin lowered plasma renin activity to 62% (P less than 0-025) of the control value whereas diazoxide raised plasma renin activity to 178% (P less than 0.05) of the control value. 4. The combination of vasodilatation and low renin activity observed following the administration of prazosin is unique, and may have clinical significance if these factors reduce the vascular complications of hypertension.  相似文献   
80.
In a cytogenetic study on the spermatogonia of Chinese hamster, cyclohexylamine (neutral sulphate) was evaluated for mutagenic effects in comparison with an untreated control group and a group treated with the mutagenic compound cyclophosphamide, by assessing spermatogonial metaphases of treated Chinese hamster for chromosomal structural changes. Each test group comprised 8 male hamsters selected at random. Approximately 100 metaphases from each animal were assessed. The doses were 5 X 150 mg cyclohexylamine sulphate (approx. 5 X 102 mg base) per kg body-weight orally, and 5 X 100 mg cyclophosphamide per kg body-weight orally. The individual doses were administered at intervals of 24 h. Preparations were made 24 h after the final treatment, essentially by the method of Hoo and Bowles [10]. Gaps, breaks, fragments, deletions and translocations were assessed as structural changes; frequencies were determined of the metaphases (a) with aberration(s) including gaps, (b)with aberration(s) less gaps and (c)with translocation(s). Aberrations occurred in the untreated negative control group (1.24% incl. gaps, 0.25% without gaps). Translocations were not seen in the untreated group. In the cyclochexylamine group, the frequencies of the aberrant metaphases were sometimes less than in the control group (0.87% including gaps, 0.37% without gaps). Statistically, the results were not significantly different from the control data. No translocations were seen after administration of cyclohexylamine. The positive cyclophosphamide control group clearly differed from the untreated control and from the cyclohexylamine group in the parameters (a) to (c); mainly, the results were highly significantly different from those obtained in the untreated control group. The frequencies of the aberrant metaphases were 3.41% including gaps and 1.99% without gaps. The frequency of the translocations was 0.71% (5 out of 704). Cyclohexylamine sulphate, administered 5 times at 150 mg/kg body-weight orally, had no mutagenic effect, whereas cyclophosphamide, adminstered 5 times at 100 mg/kg body-weight orally, had a chromosome-damaging effect on Chinese hamster spermatogonia.  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