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   848篇
  免费   0篇
电工技术   1篇
化学工业   5篇
机械仪表   1篇
轻工业   4篇
无线电   1篇
冶金工业   836篇
  2023年   1篇
  2021年   1篇
  2008年   1篇
  2006年   1篇
  2005年   1篇
  2004年   2篇
  2003年   2篇
  1999年   18篇
  1998年   272篇
  1997年   147篇
  1996年   96篇
  1995年   53篇
  1994年   44篇
  1993年   44篇
  1992年   7篇
  1991年   10篇
  1990年   4篇
  1989年   9篇
  1988年   10篇
  1987年   10篇
  1986年   13篇
  1985年   11篇
  1983年   2篇
  1982年   3篇
  1981年   2篇
  1980年   12篇
  1978年   1篇
  1977年   19篇
  1976年   52篇
排序方式: 共有848条查询结果,搜索用时 15 毫秒
51.
The state of Oregon decided to cover all potentially eligible Medicaid citizens to 100% of poverty. Previously, Oregon had covered persons up to 67% of poverty. In order to keep overall program costs in check. Oregon decided to limit the number of services that its Medicaid program would cover. Oregon's normative choice was to contain program costs by covering all eligible persons up to 100% of poverty, while at the same time uniformly limiting access to certain services for everyone in the overall group of eligible persons. The state developed a prioritization list of medical services and priced the components on the list. The amount of money ultimately available for the Medicaid program was a political decision informed by data about the cost of different services and influenced by the priorities set through an independent process of priority-setting. Physicians were asked to determine what works medically, how well it works, and what benefits accrue to patients. Recognizing that physician perspectives on efficacy might vary from patients' perspectives on valuation of benefits, Oregon's planners developed a method for valuing medical outcomes that stemmed from particular medical interventions. This blend of medical fact and value to patients allowed for comparing valuations by introducing cost considerations. Condition-treatment (CT) pairs linked a medical condition with one or more courses of treatment. The goal was to determine the likely incremental medical benefit from a given treatment. In addition, Oregon developed a Quality-of-Well-Being scale to determine the net patient benefit from medical intervention and used a telephone survey to value that net benefit. A cost-benefit ratio was derived, and a prioritization of CT pairs was developed. The article analyzes and evaluates Oregon's use of cost-benefit calculations in the allocation of Medicaid funds, noting that Oregon itself backed away from many of the implications of its cost-benefit analysis and that the Americans with Disabilities Act has constrained use of quality-of-life judgments in Medicaid resource allocation decision-making.  相似文献   
52.
Erectile dysfunction is a common (affecting 10-20 million men in the USA) and multifactorial disease due to organic and/or psychological factors that strongly impairs the quality of life in man. During the past decade many advances in the understanding of the pathophysiology of erectile dysfunction have been made and new therapeutic strategies have become available. It has been established that an insufficient production of nitric oxide by penile nerve terminals and/or vascular endothelium may result in an impaired erection or complete impotence. Nowadays, intracavernous injection of vasoactive drugs represents a standardized approach for the diagnosis, and the treatment of choice, for erectile dysfunction, but is not widely accepted by the patients. The possibility of treating erectile dysfunction with intraurethral administration of prostaglandin-E1 has recently become available in the USA, and is a therapy more acceptable to the patients. Other noninvasive medical therapies are undergoing evaluation.  相似文献   
53.
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   
54.
55.
56.
The contributions of 23 insertion, deletion, or missense mutations within an 81-bp fragment of rpoB, the gene encoding the beta-subunit of the DNA-dependent RNA polymerase of Mycobacterium tuberculosis, to the development of resistance to rifamycins (rifampin, rifabutin, rifapentine, and KRM-1648) in 29 rifampin-resistant clinical isolates were defined. Specific mutant rpoB alleles led to the development of cross-resistance to all rifamycins tested, while a subset of mutations were associated with resistance to rifampin and rifapentine but not to KRM-1648 or rifabutin. To further study the impact of specific rpoB mutant alleles on the development of rifamycin resistance, mutations were incorporated into the rpoB gene of M. tuberculosis H37Rv, contained on a mycobacterial shuttle plasmid, by in vitro mutagenesis. Recombinant M. tuberculosis clones containing plasmids with specific mutations in either codon 531 or 526 of rpoB exhibited high-level resistance to all rifamycins tested, whereas clones containing a plasmid with a mutation in codon 516 exhibited high-level resistance to rifampin and rifapentine but were susceptible to both rifabutin and KRM-1648. These results provided additional proof of the association of specific rpoB mutations with the development of rifamycin resistance and corroborate previous reports of the usefulness of rpoB genotyping for predicting rifamycin-resistant phenotypes.  相似文献   
57.
The silicone breast implant controversy rages on. Recent work has demonstrated that normal or baseline breast tissue silicon levels in women who had had no prior exposure to any type of breast implant may be as high as 446 microg/gm of tissue. These data ranged from 4 to 446 microg/gm of tissue, with a median of 27.0 microg/gm of tissue. In addition, numerous other epidemiologic and rheumatologic studies have demonstrated no association between silicone breast implants and any connective-tissue diseases. Despite these reports, the use of silicone implants remains restricted. The present study measured breast and capsular tissue silicon levels from 23 breasts in 14 patients with saline implants, and from 42 breasts in 29 patients with silicone implants. No patient in the saline implant group presented with signs or symptoms of connective-tissue disease. Patients with silicone implants, however, were divided into three groups based on the presence or absence of signs or symptoms of connective-tissue disease: group I, no symptoms or signs; group II, + symptoms, no signs; and group III, + symptoms, + signs. Six patients in group III were diagnosed with a specific connective-tissue disease, including systemic lupus erythematosus, rheumatoid arthritis, or scleroderma. The most common indications for implant removal or exchange were capsular contracture and implant rupture, although 41 percent of patients with silicone implants expressed media-related concern over the implant issue. The most common symptoms described by patients in groups II and III were joint pain and stiffness, arm pain and numbness, and fatigue. In all groups, capsular tissue silicon levels were significantly greater than breast tissue levels. This finding may indicate that the capsule serves as a barrier to the distribution of silicone from the implant into adjacent breast tissue. Although breast tissue silicon levels in patients with silicone implants were not significantly greater than those in patients with saline implants (p = 0.48), capsular tissue levels in patients with silicone implants were, indeed, significantly greater than those in patients with saline implants (p < 0.001). However, no statistically significant differences in tissue silicon levels were observed with relation to the presence or absence of connective-tissue disease signs or symptoms in patients with silicone implants (groups I to III). Therefore, these data strengthen the conclusion that there is no association between tissue silicon levels and connective-tissue disease.  相似文献   
58.
59.
The modification of reactive protein sulfhydryls by S-nitrosoglutathione and other NO donors has been studied by gel isoelectric focusing. S-nitrosylated, unmodified, and S-glutathiolated protein forms are differentiated by this method. With specific antibodies for the protein of interest, both S-nitrosylation and S-glutathiolation of the protein were analyzed in mixtures obtained as soluble tissue or cell extracts. The effect of S-nitrosoglutathione (GSNO) on purified phosphorylase b, on carbonic anhydrase III in an extract from rat liver, and on H-ras expressed in Escherichia coli was examined. When fresh GSNO reacted with pure phosphorylase b, only S-nitrosylated forms of the protein were observed. Likewise the NO donors, amyl nitrite, spermine NONOate, and diethylamine NONOate, all generated S-nitrosylated phosphorylase b. When crude mixtures of proteins from rat liver (containing carbonic anhydrase III) or from E. coli (containing an overexpressed form of H-ras) were exposed to fresh GSNO, both the S-nitrosylated and the S-glutathiolated forms of the proteins were observed. It is suggested that reactive intermediates from the breakdown of GSNO are responsible for the observed S-glutathiolation. These experiments show that both S-nitrosylated and S-glutathiolated forms of proteins may be generated by the addition of GSNO to mixtures containing proteins with reactive sulfhydryls. These protein modifications may exhibit metabolic consequences independent of the release of nitric oxide.  相似文献   
60.
We studied the effect of rehabilitation strength training and return to activities on anterior-posterior knee displacements after patellar tendon autogenous anterior cruciate ligament reconstruction. A total of 938 measurements were sequentially collected for 142 patients with the KT-2000 arthrometer. Rehabilitation included immediate knee motion and early weightbearing, light sports at 6 months, and competitive sports at 8 months or later. At a minimum of 2 years after surgery, 121 patients (85%) had normal displacements (less than 3 mm of increase at 134 N), 14 (10%) had 3 to 5.5 mm of increase (partial function), and 7 (5%) had more than 5.5 mm of increase (failed). There was no association found between the initial onset of the abnormal displacements in the 21 knees and either the amount of time after surgery or the rehabilitation program. Six of the seven grafts that failed did so in the 1st postoperative year. Serial displacement measurements allow early detection of graft stretching and subsequent modification of rehabilitation or delay in return to strenuous activities. These measurements showed that the rehabilitation program used in this study was not itself injurious and resulted in an acceptable failure rate of 5%.  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