全文获取类型
收费全文 | 6686篇 |
免费 | 99篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 19篇 |
综合类 | 1篇 |
化学工业 | 280篇 |
金属工艺 | 31篇 |
机械仪表 | 68篇 |
建筑科学 | 81篇 |
矿业工程 | 1篇 |
能源动力 | 57篇 |
轻工业 | 184篇 |
水利工程 | 24篇 |
石油天然气 | 1篇 |
无线电 | 248篇 |
一般工业技术 | 586篇 |
冶金工业 | 4981篇 |
原子能技术 | 9篇 |
自动化技术 | 218篇 |
出版年
2022年 | 18篇 |
2021年 | 33篇 |
2020年 | 20篇 |
2019年 | 29篇 |
2018年 | 66篇 |
2017年 | 70篇 |
2016年 | 40篇 |
2015年 | 37篇 |
2014年 | 55篇 |
2013年 | 109篇 |
2012年 | 110篇 |
2011年 | 113篇 |
2010年 | 118篇 |
2009年 | 98篇 |
2008年 | 72篇 |
2007年 | 92篇 |
2006年 | 66篇 |
2005年 | 86篇 |
2004年 | 66篇 |
2003年 | 68篇 |
2002年 | 55篇 |
2001年 | 37篇 |
2000年 | 54篇 |
1999年 | 192篇 |
1998年 | 1485篇 |
1997年 | 920篇 |
1996年 | 554篇 |
1995年 | 304篇 |
1994年 | 280篇 |
1993年 | 310篇 |
1992年 | 59篇 |
1991年 | 63篇 |
1990年 | 96篇 |
1989年 | 91篇 |
1988年 | 79篇 |
1987年 | 79篇 |
1986年 | 65篇 |
1985年 | 56篇 |
1984年 | 18篇 |
1983年 | 18篇 |
1982年 | 21篇 |
1981年 | 41篇 |
1980年 | 61篇 |
1979年 | 15篇 |
1978年 | 21篇 |
1977年 | 115篇 |
1976年 | 237篇 |
1975年 | 22篇 |
1973年 | 10篇 |
1969年 | 8篇 |
排序方式: 共有6789条查询结果,搜索用时 0 毫秒
991.
992.
Kainate-induced seizures are widely studied as a model of human temporal lobe epilepsy due to behavioral and pathological similarities. While kainate-induced neuronal injury is well characterized in rats, relatively little data is available on the use of kainate and its consequences in mice. The growing availability of genetically altered mice has focused attention on the need for well characterized mouse seizure models in which the effects of specific genetic manipulations can be examined. We therefore examined the kainate dose-response relationship and the time-course of specific histopathological changes in C57/BL mice, a commonly used founder strain for transgenic technology. Seizures were induced in male C57/BL mice (kainate 10-40 mg/kg i.p.) and animals were sacrificed at various time-points after injection. Seizures were graded using a behavioral scale developed in our laboratory. Neuronal injury was assayed by examining DNA fragmentation using in situ nick translation histochemistry. In parallel experiments, we examined the expression an inducible member of the heat shock protein family, HSP-72, another putative marker of neuronal injury, using a monoclonal antibody. Seizure severity paralleled kainate dosage. At higher doses DNA fragmentation is seen mainly in hippocampus in area CA3, and variably in CA1, thalamus and amygdala within 24 h, is maximal within 72 h, and is largely gone by 7 days after administration of kainate. HSP-72 expression is also highly selective, occurring in limbic structures, and it evolves over a characteristic time-course. HSP-72 is expressed mainly in structures that also manifest DNA fragmentation. Using double-labeling techniques, however, we find essentially no overlap between neurons expressing HSP-72 and DNA fragmentation. These findings indicate that DNA fragmentation and HSP-72 expression are complementary markers of seizure-induced stress and injury, and support the notion that HSP-72 expression is neuroprotective following kainate-induced seizures. 相似文献
993.
994.
Twenty-six patients with severe COPD or asthma completed standard questionnaires before, and 2 months after, starting home nebulized bronchodilator therapy. Patients' perceived illness severity and their expectations of treatment with regard to symptoms were examined in the first questionnaire, and outcome was assessed in the second. Before treatment started patients expected a definite improvement in all symptoms studied. After treatment the group showed only a marginal subjective improvement in all symptoms. The improvement attained with regard to breathlessness, ability to get out and about, and general quality of life was significantly lower than had been expected. While home nebulized bronchodilator therapy is well tolerated and confers some subjective benefit in selected individuals, patients appear to have unrealistically high expectations of treatment. 相似文献
995.
996.
Axelrod Bradley N.; Putnam Steven H.; Woodard John L.; Adams Kenneth M. 《Canadian Metallurgical Quarterly》1996,8(1):73
Equations for prorating the Wechsler Memory Scale—Revised General Memory (GM) and Delayed Recall (DR) index scores (J. L. Woodard & B. N. Axelrod,1995) were confirmed in a new clinical sample of 258 patients. Raw score results for Logical Memory, Visual Reproduction, and Verbal Paired Associates were entered into the prediction equations. Predicted GM and DR scores fell within 6 points of obtained scores for 94% and 97% of the sample, respectively. A multiple regression analysis yielded multiple R–2 of .976 and .984 for GM and DR, respectively. In addition, the unstandardized regression weights were virtually identical to those initially presented by Woodard and Axelrod. These prediction equations for the GM and DR summary scores have validity for patient samples similar to those of the present study. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
997.
The CBP co-activator is a histone acetyltransferase 总被引:5,自引:0,他引:5
998.
Intrathecal treatment with cytosine arabinoside (ara-C) in combination with radiation has been used as prophylactic treatment in children with acute lymphatic leukaemia. Animal experiments have shown that ara-C enhances the effect of radiation on the spinal cord when administered shortly before irradiation, and that the long-term recovery after a combined treatment may be impaired. In the present experiments immature, 3-week-old rats, were treated with ara-C and radiation on the cervical spinal cord, and the long-term recovery was examined by reirradiation after different intervals. The endpoint of the study was paresis due to radiation myelopathy. The results showed a clear enhancement of the radiation effect with a dose-modifying factor of 1.2, when ara-C was administered before irradiation. However, no indications for impaired long-term recovery were observed. Additional experiments in adult rats with ara-C treatments during a 6-month interval between two radiation doses also did not suggest any interference between ara-C treatment and long-term recovery of radiation induced injury. It is concluded that for both the adult and immature nervous tissue, only when ara-C is administered intraspinally shortly before irradiation, interaction between ara-C and radiation results in a significant reduction of the isoeffective radiation dose by a factor of 1.2 (1.13-1.37, 95% confidence interval). 相似文献
999.
To examine the relationship between insurance coverage and the diagnostic content of residents' experience in a hospital-based pediatric teaching clinic, we analyzed outpatient problem lists for 6543 patients seen in our clinic over a 15-month period. Problem-list contents were categorized using diagnostic clusters. The frequency distribution of clustered problems was compared for patients with four types of insurance coverage: indemnity insurance, health maintenance organization, Medicaid, and no insurance. The four insurance categories differed in the overall distribution of problems, but the differences could not be attributed to a disparity in the frequency of any single diagnosis or diagnostic cluster. We conclude that there was no important effect of insurance coverage on the diagnostic content of residents' experience in a teaching clinic. 相似文献
1000.
JJ Bradley 《Canadian Metallurgical Quarterly》1993,24(10):64J, 64N-64J, 64O
The perception of contemporary nursing as being subordinate and subservient to medicine can be compared to the role of chloroform, which in its day served the purpose intended. However, like nursing, today's anesthetic agents require greater expertise to maximize their effectiveness. As nursing enters a new era in its struggle for autonomy, androgynous approaches promise increased independent thinking, action and self-esteem. Nurses possessing these qualities can address effectively, many of the challenges today's nursing practice poses. 相似文献