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   2124篇
  免费   0篇
  国内免费   1篇
电工技术   3篇
综合类   1篇
化学工业   9篇
金属工艺   1篇
机械仪表   38篇
建筑科学   5篇
能源动力   1篇
轻工业   40篇
水利工程   1篇
无线电   5篇
一般工业技术   4篇
冶金工业   2010篇
自动化技术   7篇
  2021年   2篇
  2019年   2篇
  2018年   1篇
  2017年   1篇
  2015年   1篇
  2013年   3篇
  2012年   1篇
  2011年   2篇
  2010年   5篇
  2009年   6篇
  2008年   5篇
  2007年   4篇
  2006年   7篇
  2005年   6篇
  2004年   3篇
  2003年   7篇
  2002年   7篇
  2001年   7篇
  2000年   15篇
  1999年   74篇
  1998年   602篇
  1997年   353篇
  1996年   222篇
  1995年   139篇
  1994年   99篇
  1993年   119篇
  1992年   12篇
  1991年   18篇
  1990年   15篇
  1989年   17篇
  1988年   23篇
  1987年   13篇
  1986年   16篇
  1985年   17篇
  1984年   1篇
  1983年   7篇
  1982年   7篇
  1981年   19篇
  1980年   27篇
  1978年   6篇
  1977年   66篇
  1976年   160篇
  1975年   3篇
  1973年   1篇
  1964年   1篇
  1955年   3篇
排序方式: 共有2125条查询结果,搜索用时 31 毫秒
991.
The paper describes a non-invasive oscillometric blood pressure (BP) measuring device. It provides an algorithm for the automatic measurement of systolic and diastolic BP values. A variant of assessing the BP measurement stability is proposed and the results of this assessment are given for 3 devices made by different firms. The total errors made by the studied device that functions as part of a physician's computer monitor are defined. Health institutions, resuscitation units, operating rooms for children and adults are an application sphere of the device.  相似文献   
992.
Forty critically ill adult patients with severe Gram-negative infection were treated with once-daily amikacin combined with ceftazidime. The mean age was 56.6 +/- 19 years and mean APACHE II score was 22.7 +/- 6.6. Forty percent of patients required mechanical ventilation. The mean creatinine clearance at onset of therapy was 59.4 +/- 28 ml/min. All bacterial isolates were sensitive to amikacin. Fixed doses of amikacin 15 mg/kg, 12 mg/kg, and 8 mg/kg body weight were given once daily to patients with estimated creatinine clearance of > 80 ml/min., 50-80 ml/min., and < 50 ml/min, respectively. Forty-two causative gram-negative bacteria were isolated from 40 patients. The most common bacteria were Pseudomonas aeruginosa (18), and Escherichia coli (10). Overall clinical success and bacteriological eradication occurred in 85% and 87.5% of patients; 78.9% and 79% of patients with hospital-acquired infections; 90.5% and 95.2% of patients with community-acquired infections; and 62.5% and 81.3% of patients requiring mechanical ventilation, respectively. Therapeutic failure was documented in 15% of patients. Death due to infection was scored in two patients. The remaining were all due to persistence of the initial causative bacteria in patients with hospital-acquired infections. Persistence was documented with Ps. aeruginosa (2), Serratia spp. (1), and Acinetobacter spp. (1). Overall mortality occurred in 22.5% patients. Death unrelated to infection occurred in 7 patients. There was no clinical evidence of ototoxicity in any of our patients, however, nephrotoxicity was documented in 5%. In conclusion, once-daily amikacin combined with ceftazidime is practical, efficacious and probably safe in critically ill infected patients.  相似文献   
993.
A patient with a history of drug abuse and histologically diagnosed hepatitis B-related polyarteritis nodosa was admitted for severe hypertension. After a cesarean section because of worsening of her clinical status with severe proteinuria and edema, she improved dramatically. No sign of acute polyarteritis nodosa occurred.  相似文献   
994.
Although liposarcoma is the second most common soft-tissue sarcoma in adults, its incidence within the gastrointestinal tract is distinctly low. Esophageal involvement is exceedingly rare and only four cases have been described so far. A fifth case is presented here along with a thorough review of the literature of polypoid lipomatous tumors of the esophagus. Diagnostic and therapeutical strategies of these tumors are discussed in detail.  相似文献   
995.
Tuberculosis is an ancient disease which has had a resurgence in the United States. Many elderly clients were exposed to tuberculosis as children and young adults and are still carrying the infection today. This article describes tuberculosis as it affects the elderly client in community and nursing home settings. The history, etiology, clinical manifestations, treatment, and prevention of tuberculosis infection and disease are presented. Because nurses can be very instrumental in controlling tuberculosis in the elderly, gerontological nursing implications are discussed.  相似文献   
996.
In tissues that closely approximate bone, sufficient heat may be transferred to the bone during laser surgery to cause damage and/or necrosis. To date, there have been few studies examining the temperatures elicited at the bone surface as a result of laser application to the overlying soft tissues. The purpose of this investigation was to determine, under in vitro conditions, temperature changes at the bone/soft tissue interface during laser ablation with CO2 and Nd:YAG lasers used with and without (w/wo) air/water coolant. Experimental specimens consisted of 5 mandibles from freshly sacrificed hogs; laser treatment sites were the buccal and lingual attached gingiva of the molars and the lingual keratinized mucosa of the incisor region. CO2 and Nd:YAG lasers were used w/wo coolant at power settings of 4 to 8 W and 5 to 9 W, respectively. Temperature changes were measured with a copper constant thermocouple contained within a 21 gauge hypodermic needle. In comparing the lasers at comparable energy densities w/wo coolant, temperature increases at the bone/soft tissue interface ranged from 8.0 to 11.1 degrees C with the Nd:YAG and 1.4 to 2.1 degrees C with the CO2. Similarly, in comparing the times required for the interface to return to baseline temperature following removal of the laser, values ranged from approximately 143 to 205 and approximately 119 to 139 seconds for the Nd:YAG and CO2, respectively. Results from this study suggest that, at energy densities equal or above those reported here, the increase in temperature at the bone surface as a result of periodontal soft tissue surgery with the Nd:YAG laser could be damaging, especially if the exposure is prolonged.  相似文献   
997.
OBJECTIVES: To assess the efficacy of a combination of oral and topical 5-aminosalicylic acid (5-ASA) for the maintenance treatment of ulcerative colitis, we undertook a double-blind randomized clinical trial. METHODS: Patients aged 18 to 65 yr (with disease extent greater than proctitis only) were eligible for inclusion in the study if they met the following criteria: (a) history of two or more relapses in the last year; (b) achievement of remission in the last 3 months (with maintenance of remission for at least 1 month). Patients enrolled in the study were randomly assigned to one of the two following 1-yr treatments: (1) combined therapy with 5-ASA tablets 1.6 g/day and 5-ASA enemas 4 g/100 ml twice weekly; (2) oral therapy with 5-ASA tablets 1.6 g/day and placebo enemas/twice weekly. The main end point of the study was the maintenance of remission at 12 months. RESULTS: Upon completion of the study, relapse occurred in 13 of 33 patients in the combined treatment group versus 23 of 36 patients in the oral treatment group (39 vs 69%; p = 0.036). No significant side effects related to treatment were observed in either group. A simplified pharmacoeconomic analysis shows that this form of combined treatment can have a favorable cost-effectiveness ratio. CONCLUSIONS: Our results indicate that 5-ASA given daily by oral route and intermittently by topical route can be more effective than oral therapy alone. This form of combination treatment can be appropriate for patients at high risk of relapse.  相似文献   
998.
Major Histocompatibility Complex (MHC, HLA in humans) class I antigens play an important role in cellular immunology by presenting antigens to T cells. Downregulation of MHC class I expression is thought to be a mechanism by which tumor cells escape from T cell-mediated lysis. In primary human melanomas and melanoma cell lines, HLA-B expression is frequently downmodulated, correlating with elevated expression of the c-myc oncogene. Transfection experiments have shown that c-myc induces HLA-B downregulation through a -68 to +13 base pairs (bp) core promoter fragment, containing CCAAT and TATA-like (TCTA) boxes. Since (i) c-myc has been reported to activate the human p53 promoter and (ii) p53 is capable of repressing a large array of basal promoters, we investigated whether c-myc-induced HLA-B abrogation is mediated by p53. In this article, it is shown that the HLA-B core promoter is indeed repressed by wild-type p53, making p53 a candidate for mediating c-myc-induced HLA-B downregulation. However, transfection of c-myc into p53-null cell lines still resulted in suppression of the basal HLA-B promoter, demonstrating that c-myc and p53 repress the minimal HLA-B promoter through independent mechanisms.  相似文献   
999.
Appearance and maturation of T-cell subsets during rat thymus ontogeny   总被引:1,自引:0,他引:1  
This study measured the release of glutamate (Glu) and aspartate (Asp) amino acid transmitters in the ventrocaudal compartment of the rat periaqueductal gray (PAG) following exposure to unilateral peripheral inflammation. The release of endogenous Glu and Asp from the rat ventrocaudal PAG was monitored with the microdialysis technique in unanesthetized, unrestrained rats. There was significant increase (1,300%) in the basal concentrations of Glu release in the 7 days Complete Freund's Adjuvant (CFA) treated group compared to 24 h mineral oil control group. Amino acid release was induced by infusing veratridine (75 microM, a sodium channel activator) directly through the 1 mm long dialysis probe. Perfusion of veratridine into the ventrocaudal PAG resulted in significant elevation of Glu and Asp amino acids. In the 24 h and 7 days CFA treated rats, veratridine-evoked release of Glu was significantly decreased in the lateral ventrocaudal PAG compared to control rats injected with mineral oil (CFA vehicle). The peak minus baseline concentrations of Glu in 24 h and 7 days CFA treated groups decreased 55.7% and 43.9%, respectively. In contrast, The basal and the peak minus baseline concentrations of Asp showed no significant change between control group and 24 h and 7 days CFA treated animals. The results provide direct evidence that Glu excitatory amino acid may be involved in nociception/nociception modulation pathway in the ventrocaudal PAG.  相似文献   
1000.
An interesting case of congenital double uterus and the intrapartum events associated with it are described. In view of the rarity of the condition, its implication to the patient, her general practitioner and the obstetrician/gynaecologist is discussed, with special reference to contraception, cervical smear and operative surgical technique.  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