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   619篇
  免费   0篇
综合类   1篇
化学工业   24篇
机械仪表   2篇
轻工业   7篇
一般工业技术   2篇
冶金工业   583篇
  2025年   1篇
  2018年   1篇
  2017年   2篇
  2015年   1篇
  2014年   2篇
  2013年   16篇
  2012年   3篇
  2011年   1篇
  2010年   1篇
  2008年   3篇
  2007年   2篇
  2005年   1篇
  1999年   15篇
  1998年   183篇
  1997年   101篇
  1996年   63篇
  1995年   32篇
  1994年   40篇
  1993年   39篇
  1992年   2篇
  1991年   2篇
  1990年   1篇
  1989年   3篇
  1988年   4篇
  1987年   5篇
  1986年   2篇
  1985年   1篇
  1983年   2篇
  1982年   4篇
  1981年   4篇
  1980年   6篇
  1979年   1篇
  1977年   21篇
  1976年   49篇
  1975年   2篇
  1974年   1篇
  1969年   1篇
  1955年   1篇
排序方式: 共有619条查询结果,搜索用时 0 毫秒
611.
The jejunum was able to metabolize p-nitrophenol (PNP) rapidly and to transport the metabolites efficiently back into the luminal solution. About 21, 16, 6 and 3.5% of recirculated amount of PNP could be detected in 90 minutes as glucuronide in the lumen of jejunal loop, when 20, 100, 500 or 1,000 microM PNP was perfused, which shows that the luminal appearance of p-nitrophenol-glucuronide (PNP-G) tended to saturability. Biliary excretion rate of PNP-G was lower than the luminal appearance of this metabolite, when PNP was recirculated at 20 or 100 microM concentrations, however, at higher concentrations (500, 1,000 microM) the biliary excretion exceeded the luminal appearance of this conjugate and no saturability was observed in the biliary glucuronidation of PNP. Biliary excretion of sulfate conjugate of p-nitrophenol (PNP-S) exceeded the luminal appearance of this metabolite.  相似文献   
612.
613.
614.
CONTEXT: The US Preventive Services Task Force recommends that physicians assess patients' health risk behaviors, addressing those needing modification. OBJECTIVE: To examine the relationship between patient income, health risk behaviors, the prevalence of physician discussion of these behaviors, and the receptiveness of patients to their physicians' advice. DESIGN: Employee survey. PARTICIPANTS: A random sample of 6549 Massachusetts state employees in 12 health plans. MAIN OUTCOME MEASURES: Data were obtained using a patient-completed mail survey. Trend tests were used to discern differences in the prevalence of health risk behaviors, physician discussion of these behaviors, and patient receptiveness to discussions by patient income. RESULTS: Although unhealthy behaviors were common among all income groups, physician discussion of health risk behaviors fell far short of the universal risk assessment recommended by the US Preventive Services Task Force. Low-income patients were more likely to be obese and smoke than high-income patients and were less likely to wear seat belts and exercise. In contrast, stress and alcohol consumption increased with income, while the proportion of heavy drinkers did not vary significantly. Physicians were more likely to discuss diet and exercise with high-income patients in need of these discussions than with low-income patients, but were more likely to discuss smoking with low-income patients who smoked than with high-income patients who smoked. Among patients with whom discussions occurred, low-income patients were much more likely to report attempting to change their behavior based on physician advice. CONCLUSIONS: Physician counseling of patients regarding health risk behaviors should be greatly improved if the US Preventive Services Task Force recommendations are to be fulfilled. Improvement is especially needed in regard to alcohol consumption, safe sex, and seat belt use. Physicians also need to be more vigilant in properly identifying and counseling low-income patients at risk in regard to diet and exercise and high-income patients who smoke.  相似文献   
615.
616.
617.
A recently developed method to rapidly quantify the elemental composition of bulk organic aerosols (OA) using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) is improved and applied to ambient measurements. Atomic oxygen-to-carbon (O/C) ratios characterize the oxidation state of OA, and O/C from ambient urban OA ranges from 0.2 to 0.8 with a diurnal cycle that decreases with primary emissions and increases because of photochemical processing and secondary OA (SOA) production. Regional O/C approaches approximately 0.9. The hydrogen-to-carbon (H/C, 1.4--1.9) urban diurnal profile increases with primary OA (POA) as does the nitrogen-to-carbon (N/C, approximately 0.02). Ambient organic-mass-to-organic-carbon ratios (OM/OC) are directly quantified and correlate well with O/C (R2 = 0.997) for ambient OA because of low N/C. Ambient O/C and OM/OC have values consistent with those recently reported from other techniques. Positive matrix factorization applied to ambient OA identifies factors with distinct O/C and OM/OC trends. The highest O/C and OM/OC (1.0 and 2.5, respectively) are observed for aged ambient oxygenated OA, significantly exceeding values for traditional chamber SOA,while laboratory-produced primary biomass burning OA (BBOA) is similar to ambient BBOA, O/C of 0.3--0.4. Hydrocarbon-like OA (HOA), a surrogate for urban combustion POA, has the lowest O/C (0.06--0.10), similar to vehicle exhaust. An approximation for predicting O/C from unit mass resolution data is also presented.  相似文献   
618.
Four different heparin preparations--sodium and calcium salts of the same batch of heparin (mean molecular weight 15,000), low molecular weight sodium heparin (mean m.w. 9,000) and high molecular weight sodium heparin (mean m.w. 22,000) were injected subcutaneously on different days each into 6 healthy young volunteers in a randomized trial. Plasma heparin levels were measured using the anti-Xa assay at 1 hour, 3-4 hours and 6-7 hours after the injection. The highest anti-Xa potentiating effect was obtained after the injection of the low molecular weight sodium heparin (mean 0.381 i.u./ml) at 3-4 hours after the injection. With sodium heparin (m.w. 15,000) the highest values (0.135 i.u./ml) were found at 1 hour. Significantly lower anti-Xa potentiating effect was obtained 1 hour after the injection of calcium heparin and in particular after the injection of high molecular weight heparin (mean values 0.072 i. u./ml and 0.043 i. u./ml respectively). Both these preparations showed an increase from 1 hour after injection to 3-4 hours after injection (mean values 0.082 i. u./ml and 0.057 i. u./ml at 3-4 hours after injection). These results indicate that the salt and the molecular weight of the preparation may strongly influence the degree of anticoagulation achieved after subcutaneous injection.  相似文献   
619.
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