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   1490篇
  免费   1篇
化学工业   4篇
轻工业   3篇
一般工业技术   3篇
冶金工业   1481篇
  2015年   1篇
  2013年   2篇
  2012年   1篇
  2010年   1篇
  2006年   1篇
  2003年   4篇
  2000年   1篇
  1999年   35篇
  1998年   468篇
  1997年   277篇
  1996年   179篇
  1995年   91篇
  1994年   72篇
  1993年   84篇
  1992年   7篇
  1991年   23篇
  1990年   18篇
  1989年   17篇
  1988年   16篇
  1987年   26篇
  1986年   16篇
  1985年   13篇
  1982年   7篇
  1981年   14篇
  1980年   11篇
  1979年   2篇
  1978年   3篇
  1977年   24篇
  1976年   75篇
  1975年   1篇
  1955年   1篇
排序方式: 共有1491条查询结果,搜索用时 15 毫秒
1.
2.
3.
A memory-based processing approach to discourse comprehension emphasizes the rapid deployment of information in memory to facilitate understanding of the text that is currently being read. S. B. Greene, R. J. Gerrig, G. McKoon, and R. Ratcliff (1994) demonstrated that when a text described the reunion of 2 characters who had previously discussed a 3rd character, the accessibility of the 3rd character increased, and the use of an unheralded pronoun (R. J. Gerrig, 1986) to refer to that character was felicitous. In experiments in this article, the authors demonstrate that concepts related to the unheralded pronoun also increase in accessibility and that those concepts form associations in memory with concepts present in the discourse at the time the pronoun is used. The authors also show that the increase in accessibility for the referent of the pronoun, as well as the appropriate long-term memory associations, occurs even in the absence of the pronoun.  相似文献   
4.
5.
Bowen's disease has a particular predilection for the lower leg, especially in women. A review of the literature for treating Bowen's disease is presented and the problems associated with treating the lower leg emphasized. Evidence for the various treatment modalities used to treat Bowen's disease largely comes from studies that lack good methodology in terms of standardized techniques, patient controls and adequate follow-up. In particular the widely accepted recommendation for excision is not supported by evidence that this treatment is superior to other modalities. The choice of treatment for Bowen's disease should take into account the patient's general condition, the site and size of the lesion.  相似文献   
6.
In experiments on male rabbits with the lack of insulin it is been revealed violations after the past immobilization the intensivity and duration of neutrophilic leukocytosis decrease, contents of lysosomes in neutrophils, activity of acid phosphatase. By lysosomal ferments don't determine the can observer discordance of processes of coagulation, fibrinolysis, kininogenesis.  相似文献   
7.
Current methods used clinically to assess myocardial perfusion are invasive and expensive. As the technology of ultrasound imaging improves, CE may provide a relatively inexpensive, noninvasive means of quantitating myocardial perfusion. Issues regarding stability of microbubble contrast agents must be studied more closely under physiologic conditions. As such, encapsulated microbubbles may provide more stability under physiologic pressures than free gas microbubbles. Introducing high concentrations of contrast, either by hyperconcentrating the contrast agent or by increasing the injection rate, may provide greater stability under physiologic conditions. Further, before quantitative statement of tissue perfusion can be made, the relationship between tracer concentration and system response must be established. Further, a "linear" postprocessing ultrasound setting does not eliminate this requirement as data must still undergo nonlinear transformation during log compression and time-gain compensation. Additionally, issues regarding "electronic thresholding" must be explored more extensively in vivo. Commercial ultrasound scanners, in their present form, may not offer adequate sensitivity for absolute quantitative studies. Further development of modified ultrasound systems may provide sufficient sensitivity for quantitative perfusion imaging. CE offers a potentially powerful tool in the clinical management of patients with ischemic heart disease. Conventional coronary angiography provides information on the size of a lesion, but accompanying tissue perfusion distal to the lesion cannot be determined. Doppler ultrasonography determines velocity of blood flow in large vessels but does not offer the potential to quantitate tissue perfusion. Clearly, CE has a place in the future of diagnostic imaging. The recent work of Ito et al. demonstrated the qualitative potential of CE in the identification of "areas at risk" in patients who had undergone thrombolysis or percutaneous transluminal coronary angioplasty after an acute myocardial infarction. With further improvement in the ultrasound imaging techniques and microbubble stability, CE may offer an inexpensive, noninvasive means of assessing myocardial perfusion.  相似文献   
8.
Mechanisms of temperature regulation were assessed by measurements of oxygen consumption (VO2), body temperature (Rre = rectal, Tsk = skin), evaporative water loss (EWL), regional distribution of blood flow, and blood volume. Hamsters (Mesocricetus auratus) were acclimated to ambient temperatures of 34 or 22 degrees C. VO2 of 34 degrees C-exposed animals was reduced to 50% of that of controls at 22 degrees C, whereas EWL with heat exposure was almost double that of controls. Heat-acclimated animals had a slightly elevated Tre in comparison to 22 degrees C-acclimated animals, whereas there was a marked elevation in Tsk with heat exposure, in contrast to control animals at 22 degrees C. Blood flow distribution measurements indicated that with 34 degrees C exposure there was a decreased flow in liver, kidney, and intestine, whereas there was an increase to the carcass. Red cell and plasma volumes in heat-acclimated hamsters were decreased belwo the values of the 22 degrees C controls. Heat acclimation of the fhamster appears to involve reduced VO2 and increased WEL. Convective and radiative heat loss appear to be maintained by increased Tsk with heat exposure. Nonevaporative heat dissipation mechanisms are of primary importance in thermoregulation of the heat-acclimated hamster, and it is suggested that this is mediated by increased peripheral blood flow with reduced flow to the viscera.  相似文献   
9.
The relative frequency of gonorrhea and nongonococcal urethritis was studied among all active duty US Navy and Marine Corps personnel. Between 1966 and 1974, the incidence of the two diseases increased in parallel fashion, reaching 80.2 cases of gonorrhea and 61.8 cases of nongonococcal urethritis per 1000 average strength in 1974. The 56,457 cases of gonorrhea and 43,538 cases of nongonococcal urethritis reported in 1974 were unevenly distributed geographically. In the United States that year, nongonococcal urethritis was the more commonly reported condition, with 32.9 cases per 1000 average strength per year compared to 28.6 for gonorrhea; and, for the last four years, the ratio of the two was 1.05 cases of nongonococcal urethritis for each case of gonorrhea. These findings imply that nongonococcal urethritis is a significantly greater problem than has been generally recognized.  相似文献   
10.
Two hundred twenty-three children who underwent anti-reflux surgery were evaluated. Pyelonephritic scarring was more apt to occur with greater degrees of reflux. Postoperative infection was principally confined to the bladder and occurred primarily in females. The beneficial effect of anti-reflux surgery is discussed.  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