全文获取类型
收费全文 | 1990篇 |
免费 | 0篇 |
专业分类
化学工业 | 9篇 |
金属工艺 | 2篇 |
轻工业 | 3篇 |
无线电 | 3篇 |
一般工业技术 | 8篇 |
冶金工业 | 1962篇 |
自动化技术 | 3篇 |
出版年
2023年 | 1篇 |
2021年 | 1篇 |
2016年 | 1篇 |
2013年 | 1篇 |
2011年 | 3篇 |
2008年 | 2篇 |
2007年 | 2篇 |
2006年 | 1篇 |
2005年 | 1篇 |
2004年 | 1篇 |
2003年 | 4篇 |
2000年 | 3篇 |
1999年 | 71篇 |
1998年 | 706篇 |
1997年 | 382篇 |
1996年 | 229篇 |
1995年 | 116篇 |
1994年 | 111篇 |
1993年 | 114篇 |
1992年 | 16篇 |
1991年 | 21篇 |
1990年 | 8篇 |
1989年 | 17篇 |
1988年 | 9篇 |
1987年 | 14篇 |
1986年 | 9篇 |
1985年 | 15篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 7篇 |
1980年 | 12篇 |
1978年 | 1篇 |
1977年 | 32篇 |
1976年 | 67篇 |
1975年 | 4篇 |
1966年 | 1篇 |
1955年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有1990条查询结果,搜索用时 4 毫秒
1.
2.
3.
Assessing obesity: classification and epidemiology 总被引:1,自引:0,他引:1
Obesity is generally defined as a body mass index (BMI) of 30 kg/m2 and higher. Overweight is defined as a BMI between 25 and 30 kg/m2. The prevalence varies considerably between countries, and between regions within countries. It is estimated that more than half of adults aged 35-65 living in Europe are either overweight or obese. Overweight is more common among men than among women but obesity is more common among women. The prevalence of obesity in Europe is probably in the order of 10-20% in men and 15-25% in adult women. In most European countries who have reliable data on time-trends the prevalence of obesity seems to be increasing. In most European countries, obesity is usually inversely associated with socio-economic status, particularly among women. New classifications of overweight may be based on cut-off points for simple anthropometric measures which reflects both total adiposity as well as abdominal fatness. 相似文献
4.
We compared development of feline hindlimb collateral circulation after acute occlusion of the terminal aorta by ligation, thrombus formation, and formation of a "closed" aortic loop containing thromboplastin. Collateral circulation development was assessed by aortograms, scintillation scans, neurological signs following occlusion, measurement of hindlimb muscle blood flow, and forelimb and hindlimb temperature. In cats in which aortic occlusion was the result of ligation or thromboplastin in the aortic loop, paralysis was not evident. Aortograms and scintillation scans indicated hindlimb blood flow. Both muscle temperature and blood flow data indicated that the return of blood flow was rapid. The 5th lumbar artery appears to be the origin of the collateral vessels. The mid-zone component is a dorsal and ventral vertebral route and an epaxial muscle route. The reentry components are the 6th or 7th lumbar arteries. The collateral vessels arise from preexisting collateral vessels. Of those cats in which aortic occlusion was the result of a thrombus, all exhibited paralysis. Aortograms, scintillation scans, muscle temperature, and hindlimb blood flow data indicated reduced hindlimb blood flow. The results suggest that the thrombus has an inhibitory effect on the development of collateral circulation. 相似文献
5.
6.
J Marszalek W Zhang TR Hupp C Margulies KM Carr S Cherry JM Kaguni 《Canadian Metallurgical Quarterly》1996,271(31):18535-18542
DnaA protein of Escherichia coli is a sequence-specific DNA-binding protein required for the initiation of DNA replication from the chromosomal origin, oriC. It is also required for replication of several plasmids including pSC101, F, P-1, and R6K. A collection of monoclonal antibodies to DnaA protein has been produced and the primary epitopes recognized by them have been determined. These antibodies have also been examined for the ability to inhibit activities of DNA binding, ATP binding, unwinding of oriC, and replication of both an oriC plasmid, and an M13 single-stranded DNA with a proposed hairpin structure containing a DnaA protein-binding site. Replication of the latter DNA is dependent on DnaA protein by a mechanism termed ABC priming. These studies suggest regions of DnaA protein involved in interaction with DnaB protein, and in unwinding of oriC, or low-affinity binding of ATP. 相似文献
7.
In order to explore the underlying dimensionality of beliefs about aging, two sets of opinion statements (one dealing with general attitudes toward aging and the other with programmatic issues) were factor analyzed for two age groups: persons under 60 (N = 290) and persons 60 and older (N = 181). For the first set of social-psychological belief statements, a common factor structure was found for the two age groups. For the second set of programmatic statements, there was some communality between age groups, but most of the items loading on the factors tended to be age-specific. The belief structure of the older group was generally more complex and variegated than was the case with the younger group. Except where the items were personal relevance, positive and negative items tended to load on separate, unipolar factors. 相似文献
8.
In 11 patients with alcohol-induced hyperlipemia, of whom 6 showed a Zieve Syndrome increased phospholipids, triglycerides and total cholesterol were found in the red cells stromal. The gasliquid chromatographic analysis of the phospholipid fatty acids showed increased contents of saturated and monounsaturated fatty acids C 16-C 18 smaller contents of longchain highly unsaturated fatty acids. The changes in the fatty acid pattern mainly occurred in patients with Zieve Syndrome and could be important for the mechanism of the hemolytic anemia. Theses findings could be in connexion with vitamin E deficiency. 相似文献
9.
The changes in unconjugated estradiol-17beta and estriol, progesterone and chorionic somatomammotropin (HCS) in peripheral plasma have been studied in 18 women at 30-minute intervals following intra-uterine prostaglandin E2 administration for therapeutic termination of second trimester pregnancy. The hormonal changes were related to the time of fetal death detected by the disappearance of fetal heart pulsations. Prostaglandin E2 was given by the intra-amniotic route with urea (5 patients) or with intravenous oxytocin (5 patients), or by the extra-amniotic route with intravenous oxytocin (8 patients). Fetal death occurred rapidly with intra-amniotic PGE2, but usually at a late stage with extra-amniotic PGE2. Three fetuses in the extra-amniotic group died at or just before abortion. A variety of fetal heart changes were noted and the time of fetal death did not appear to influence the time of abortion within each treatment subgroup. Estradiol and estriol showed a sligh but persistent fall over 24 hours prior to induction of abortion. A more rapid fall usually occurred after induction, with a consistent fall around the time of fetal death. Progesterone and HCS usually fell much less before and immediately after fetal death. A marked rise in estradiol sometimes occurred before fetal death, particularly in the intraamniotic PGE2 and urea subgroup. Estriol levels declined more rapidly before than after fetal death, whereas fetal death had less consistent effects on the other hormones. All hormones had usually fallen considerably at the time of abortion, and in some individuals marked fluctuations in hormone levels were seen. 相似文献
10.
KM Koslowski PR Shaver JT Casey T Wilson G Yamanaka AK Sheaffer DJ Tenney NE Pederson 《Canadian Metallurgical Quarterly》1999,73(2):1704-1707
Herpes simplex virus (HSV) DNA is cleaved from concatemers and packaged into capsids in infected cell nuclei. This process requires seven viral proteins, including UL15 and UL28. UL15 expressed alone displays a nuclear localization, while UL28 remains cytoplasmic. Coexpression with UL15 enables UL28 to enter nuclei, suggesting an interaction between the two proteins. Additionally, UL28 copurified with UL15 from HSV-infected cells after ion-exchange and DNA affinity chromatography, and the complex sedimented as a 1:1 heterodimer upon sucrose gradient centrifugation. These findings are evidence of a physical interaction of UL15 and UL28 and a functional role for UL15 in directing UL28 to the nucleus. 相似文献