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   869篇
  免费   3篇
化学工业   7篇
机械仪表   1篇
轻工业   41篇
石油天然气   1篇
无线电   1篇
冶金工业   818篇
自动化技术   3篇
  2022年   1篇
  2014年   4篇
  2013年   2篇
  2012年   5篇
  2011年   6篇
  2010年   3篇
  2009年   2篇
  2008年   8篇
  2007年   6篇
  2006年   9篇
  2003年   2篇
  2002年   1篇
  1999年   28篇
  1998年   260篇
  1997年   133篇
  1996年   86篇
  1995年   53篇
  1994年   58篇
  1993年   51篇
  1992年   3篇
  1991年   6篇
  1990年   4篇
  1989年   5篇
  1988年   6篇
  1987年   9篇
  1986年   9篇
  1985年   4篇
  1982年   3篇
  1981年   2篇
  1980年   10篇
  1978年   1篇
  1977年   24篇
  1976年   61篇
  1975年   2篇
  1966年   1篇
  1960年   1篇
  1955年   3篇
排序方式: 共有872条查询结果,搜索用时 15 毫秒
91.
This study examines whether, while controlling for local economic conditions, job design and other organizational factors affect facility aide turnover rates in a sample of 250 nursing homes from 10 states. Facility characteristics were largely based on administrator and director of nursing interviews conducted in 1993 as part of the Health Care Financing Administration's evaluation of the Resident Assessment Instrument (RAI) implementation. Aide turnover was significantly reduced by involvement in interdisciplinary care plan meetings. Turnover rates were higher in for-profit homes. Aide involvement in assessments, aide training and workload, case mix severity, payor source mix, and facility size were not significantly related to aide turnover.  相似文献   
92.
Telomere length is maintained through a dynamic balance between addition and loss of the terminal telomeric DNA. Normal telomere length regulation requires telomerase as well as a telomeric protein-DNA complex. Previous work has provided evidence that in the budding yeasts Kluyveromyces lactis and Saccharomyces cerevisiae, the telomeric double-stranded DNA binding protein Rap1p negatively regulates telomere length, in part by nucleating, by its C-terminal tail, a higher-order DNA binding protein complex that presumably limits access of telomerase to the chromosome end. Here we show that in K. lactis, truncating the Rap1p C-terminal tail (Rap1p-DeltaC mutant) accelerates telomeric repeat turnover in the distal region of the telomere. In addition, combining the rap1-DeltaC mutation with a telomerase template mutation (ter1-kpn), which directs the addition of mutated telomeric DNA repeats to telomeres, synergistically caused an immediate loss of telomere length regulation. Capping of the unregulated telomeres of these double mutants with functionally wild-type repeats restored telomere length control. We propose that the rate of terminal telomere turnover is controlled by Rap1p specifically through its interactions with the most distal telomeric repeats.  相似文献   
93.
Knowledge about carbohydrate recognition domains of galectins, formerly known as S-type animal lectins, is important in understanding their role(s) in cell-cell interactions. Here we report the crystal structure of human galectin-7 (hGal-7), in free form and in the presence of galactose, galactosamine, lactose, and N-acetyl-lactosamine at high resolution. This is the first structure of a galectin determined in both free and carbohydrate-bound forms. The structure shows a fold similar to that of the prototype galectins -1 and -2, but has greater similarity to a related galectin molecule, Gal-10. Even though the carbohydrate-binding residues are conserved, there are significant changes in this pocket due to shortening of a loop structure. The monomeric hGal-7 molecule exists as a dimer in the crystals, but adopts a packing arrangement considerably different from that of Gal-1 and Gal-2, which has implications for carbohydrate recognition.  相似文献   
94.
PURPOSE: We compared laparoscopic with open colectomy for treatment of colorectal cancer. METHODS: We performed a retrospective review of patients undergoing colectomy for colorectal cancer between January 1991 and March 1996 at a large private metropolitan teaching hospital. Operative techniques included open (n=90) and laparoscopic (n=80) colectomy. Laparoscopic colectomy was further subdivided into the following groups: facilitated (n=62), with extracorporeal anastomosis; near-complete (n=9), with small incision for specimen delivery only; complete (n=3), with specimen removal through the rectum; and converted to an open procedure (n=6). Main outcome measures included operative time, blood loss, time to oral intake, length of postoperative hospitalization, morbidity, lymph node yield, recurrence, survival, and costs. RESULTS: Operative time was equivalent in the laparoscopic and open groups (laparoscopic, 161 minutes; open, 163 minutes; P=0.94). Blood loss was less for the laparoscopic group (laparoscopic, 104 ml; open, 184 ml; P=0.001), and resumption of oral intake was earlier (laparoscopic, 3.9 days; open, 4.9 days; P=0.001), but length of hospitalization was similar. Mean lymph node yield in the laparoscopic group was 12 compared with 16 in the open group (P=0.16). Rates of morbidity, recurrence, and survival were similar in both groups. No port-site recurrences occurred. CONCLUSIONS: Laparoscopic and open colectomy were therapeutically similar for treatment of colorectal cancer in terms of operative time, length of hospitalization, recurrence, and survival rates. The laparoscopic approach was superior in blood loss and resumption of oral intake.  相似文献   
95.
BACKGROUND: The congenital long-QT syndrome, caused by mutations in cardiac potassium-channel genes (KVLQT1 at the LQT1 locus and HERG at the LQT2 locus) and the sodium-channel gene (SCN5A at the LQT3 locus), has distinct repolarization patterns on electrocardiography, but it is not known whether the genotype influences the clinical course of the disease. METHODS: We determined the genotypes of 541 of 1378 members of 38 families enrolled in the International Long-QT Syndrome Registry: 112 had mutations at the LQT1 locus, 72 had mutations at the LQT2 locus, and 62 had mutations at the LQT3 locus. We determined the cumulative probability and lethality of cardiac events (syncope, aborted cardiac arrest, or sudden death) occurring from birth through the age of 40 years according to genotype in the 246 gene carriers and in all 1378 members of the families studied. RESULTS: The frequency of cardiac events was higher among subjects with mutations at the LQT1 locus (63 percent) or the LQT2 locus (46 percent) than among subjects with mutations at the LQT3 locus (18 percent) (P<0.001 for the comparison of all three groups). In a multivariate Cox analysis, the genotype and the QT interval corrected for heart rate were significant independent predictors of a first cardiac event. The cumulative mortality through the age of 40 among members of the three groups of families studied was similar; however, the likelihood of dying during a cardiac event was significantly higher (P<0.001) among families with mutations at the LQT3 locus (20 percent) than among those with mutations at the LQT1 locus (4 percent) or the LQT2 locus (4 percent). CONCLUSIONS: The genotype of the long-QT syndrome influences the clinical course. The risk of cardiac events is significantly higher among subjects with mutations at the LQT1 or LQT2 locus than among those with mutations at the LQT3 locus. Although cumulative mortality is similar regardless of the genotype, the percentage of cardiac events that are lethal is significantly higher in families with mutations at the LQT3 locus.  相似文献   
96.
97.
PURPOSE: The objective of this study was to correlate the findings of sarcoidosis on high resolution CT (HRCT) with indexes of disease activity as measured with 67Ga scan, bronchoalveolar lavage (BAL), and serum angiotensin-converting enzyme (SACE) assay. METHOD: Twenty-nine patients with proven sarcoidosis underwent HRCT scan, 67Ga scan, BAL, and SACE assay within a 1 month period. The extent of parenchymal involvement by nodules, consolidation, ground-glass attenuation, and linear opacities was quantified to the nearest 10% of surface area affected on the CT examination. Whole-lung gallium uptake was quantified and the percentage of BAL-recovered lymphocytes (BAL-%LC) and SACE levels obtained by chart review. CT scores of disease extent were correlated with measured indexes of activity using the Spearman rank correlation coefficient. RESULTS: The mean extent of nodules, consolidation, ground-glass attenuation, and linear opacities on HRCT images was 15.1 +/- 16.6, 1.6 +/- 4.0, 17.5 +/- 25.4, and 7.6 +/- 9.6%, respectively. The extent of nodules and consolidation correlated with the intensity of lung gallium uptake (r = 0.46, p < 0.02), BAL-%LC (r = 0.50, p < 0.01), and SACE levels (r = 0.38, p < 0.05). No significant correlation was found between extent of ground-glass attenuation or linear opacities with any indexes of disease activity. CONCLUSION: On HRCT scan, nodules and consolidation in sarcoidosis reflect disease activity as measured by 67Ga scan, BAL, and SACE assay.  相似文献   
98.
PURPOSE: This study was undertaken to document the effect of pudendal nerve function on anal incontinence after repair of rectal prolapse. METHODS: Patients with full rectal prolapse (n = 24) were prospectively evaluated by anal manometry and pudendal nerve terminal motor latency (PNTML) before and after surgical correction of rectal prolapse (low anterior resection (LAR; n = 13) and retrorectal sacral fixation (RSF; n = 11)). RESULTS: Prolapse was corrected in all patients; there were no recurrences during a mean 25-month follow-up. Postoperative PNTML was prolonged bilaterally (> 2.2 ms) in six patients (3 LAR; 3 RSF); five patients were incontinent (83 percent). PNTML was prolonged unilaterally in eight patients (4 LAR; 4 RSF); three patients were incontinent (38 percent). PNTML was normal in five patients (3 LAR; 2 RSF); one was incontinent (20 percent). Postoperative squeeze pressures were significantly higher for patients with normal PNTML than for those with bilateral abnormal PNTML (145 vs. 66.5 mmHg; P = 0.0151). Patients with unilateral abnormal PNTML had higher postoperative squeeze pressures than those with bilateral abnormal PNTML, but the difference was not significant (94.8 vs. 66.5 mmHg; P = 0.3182). The surgical procedure did not affect postoperative sphincter function or PNTML. CONCLUSION: Injury to the pudendal nerve contributes to postoperative incontinence after repair of rectal prolapse. Status of anal continence after surgical correction of rectal prolapse can be predicted by postoperative measurement of PNTML.  相似文献   
99.
The value of protective gloves in the health care environment is well known. However, these gloves are not perfect. Some are permeable to microorganisms and various chemicals, and/or result in side effects for health care professionals. Gloves that offer the greatest protection and least side effects are highly desirable. Protection against microorganisms and protection against chemicals used in health care are described in Part II of this three-part series.  相似文献   
100.
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