全文获取类型
收费全文 | 2202520篇 |
免费 | 170274篇 |
国内免费 | 5498篇 |
专业分类
耳鼻咽喉 | 29216篇 |
儿科学 | 73976篇 |
妇产科学 | 62717篇 |
基础医学 | 315771篇 |
口腔科学 | 60354篇 |
临床医学 | 199755篇 |
内科学 | 432615篇 |
皮肤病学 | 51110篇 |
神经病学 | 178893篇 |
特种医学 | 83816篇 |
外国民族医学 | 752篇 |
外科学 | 327775篇 |
综合类 | 52516篇 |
现状与发展 | 3篇 |
一般理论 | 844篇 |
预防医学 | 173860篇 |
眼科学 | 50838篇 |
药学 | 157091篇 |
4篇 | |
中国医学 | 5124篇 |
肿瘤学 | 121262篇 |
出版年
2019年 | 17687篇 |
2018年 | 25025篇 |
2017年 | 19235篇 |
2016年 | 21835篇 |
2015年 | 24529篇 |
2014年 | 34279篇 |
2013年 | 51351篇 |
2012年 | 68909篇 |
2011年 | 73182篇 |
2010年 | 43291篇 |
2009年 | 41090篇 |
2008年 | 67624篇 |
2007年 | 71610篇 |
2006年 | 72473篇 |
2005年 | 69984篇 |
2004年 | 67287篇 |
2003年 | 64273篇 |
2002年 | 62026篇 |
2001年 | 106078篇 |
2000年 | 108651篇 |
1999年 | 90571篇 |
1998年 | 25721篇 |
1997年 | 23172篇 |
1996年 | 23184篇 |
1995年 | 22145篇 |
1994年 | 20317篇 |
1993年 | 19016篇 |
1992年 | 69638篇 |
1991年 | 67140篇 |
1990年 | 65096篇 |
1989年 | 62339篇 |
1988年 | 56889篇 |
1987年 | 56426篇 |
1986年 | 52695篇 |
1985年 | 50473篇 |
1984年 | 38249篇 |
1983年 | 32265篇 |
1982年 | 19611篇 |
1981年 | 17516篇 |
1979年 | 34474篇 |
1978年 | 24529篇 |
1977年 | 20520篇 |
1976年 | 19371篇 |
1975年 | 20108篇 |
1974年 | 24368篇 |
1973年 | 23463篇 |
1972年 | 21773篇 |
1971年 | 20009篇 |
1970年 | 18907篇 |
1969年 | 17509篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Toward a model for improved targeting of aged at risk of institutionalization. 总被引:3,自引:1,他引:2 下载免费PDF全文
A national sample of institutionalized and noninstitutionalized aged was created by merging the 1977 National Nursing Home Survey and its counterpart, the National Health Interview Survey for the same year. A weighted logistic regression analysis was conducted to identify factors that might be useful in calculating home- and community-based long-term care clients' risk of institutionalization. A model containing patient characteristics, nursing home bed supply, and a climate variable correctly classified 98.2 percent of cases residing in nursing homes or the community. Physical dependency, mental disorder and degenerative disease, lack of spouse, being white, poverty, old age, unoccupied nursing home beds, and climate all appear to be determinants of institutional residency among the aged. 相似文献
992.
Efficacy of transdermal clonidine for headache prophylaxis and reduction of narcotic use in migraine patients. A randomized crossover trial 总被引:1,自引:0,他引:1
R C Bredfeldt J E Sutherland J E Kruse 《The Journal of family practice》1989,29(2):153-6; discussion 157-8
Thirty patients completed a double-blind, randomized crossover study utilizing transdermal clonidine and an identical-appearing placebo. Crossover occurred at 6 weeks, with a total study time of 12 weeks. Subjects were asked to record daily in a special diary (1) the presence or absence of headache, (2) duration of headache, (3) severity of headache, and (4) use of pain medication for headache relief. The severity of the headaches was rated from 1 (very mild) to 5 (very severe). Although the subjects reported a decrease in frequency, duration, and intensity of headaches while using the medicated patch, these differences did not reach statistical significance. Nineteen patients subjectively preferred the medicated patch, while five preferred the placebo (P less than .01). During use of the medicated patch, a significant reduction (P = .039) occurred in use of class II narcotics. Three doses of these substances were used by the patients when treated with clonidine, while 34 doses were taken during placebo use. These findings suggest that clonidine might have a role in reduction of parenteral narcotic use in acute pain syndromes. 相似文献
993.
994.
Release of cortical catecholamines by visual stimulation requires activity in thalamocortical afferents of monkey and cat 总被引:3,自引:0,他引:3
R T Marrocco R F Lane J W McClurkin C D Blaha M F Alkire 《The Journal of neuroscience》1987,7(9):2756-2767
Catecholamine (CA) release was measured in vivo in the monkey and cat visual cortices electrochemically. Stereate-modified, graphite-paste electrodes were used to monitor changes in norepinephrine and dopamine release. Micromolar changes in CA concentration were obtained by stimulation of the eye with nonspecific (strobe) or specific (oriented bars, radial gratings) stimuli. CA release depended on which eye was illuminated. Electrodes passed tangentially through the striate area recorded release following visual stimulation of one eye or the other in succession, and the shift in eye dominance occurred at about 500 microns intervals. The magnitude of CA release was highly correlated with the ocular dominance of neuronal activity measured with tungsten microelectrodes. Light-stimulated release was not recorded in monkey area V2, V4, or somatosensory area 1, but was recorded in cat V2, suggesting that the presence of LGN afferents is associated with CA release. Results are discussed in terms of the role of geniculate activity and the specific role of CAs in cortical information processing. 相似文献
995.
Hernia through the foramen of Winslow: a complication of cholecystectomy. A case report 总被引:2,自引:0,他引:2
In 151 years since first described, there have been 112 reported cases of hernia through the foramen of Winslow (HFW). All thus far have described HFW as a primary entity. The case reported appears to be unique with HFW as a surgical complication. HFW is the least common of internal hernias. The primary symptom is pain referred from the herniated organ and the hepatoduodenal ligament. An interesting sign is that the patient is found curled up or stooped over for pain relief. Anatomic factors implicated in HFW are an enlarged epiploic foramen, a floppy cecum and ascending colon, or abnormal length of small bowel mesentery. Tension on these structures causes pain with the torso extended. Distention of bowel in the lesser sac mimics gastric obstruction. Organs herniated are: small bowel (63%); cecum, ascending colon, and terminal ileum (30%); and transverse colon (7%). Of 25 cases reported since 1966, cecal herniation comprised two-thirds. The diagnosis may be made radiologically and the treatment is surgical. The case and a review of the literature are presented with attention to the anatomy. Also provided are the signs and symptoms of this interesting and perplexing diagnosis. 相似文献
996.
Three-dimensional spinal curvature in idiopathic scoliosis 总被引:3,自引:0,他引:3
Scoliosis is usually considered as a deformity of the spine in the frontal plane, without reference to curvatures in other planes. In this study, the three-dimensional shape of the spine of 104 patients with untreated idiopathic scoliosis (5-55 degrees Cobb) was studied by means of stereo radiographs to determine relationships between curvature of the spine in the frontal plane view, in the lateral view, and in the intermediate views. There was a weak but statistically significant correlation (r = 0.2) relating greater scoliosis with lesser kyphosis or greater lordosis. In the thoracic region, the sagittal plane spinal curvature was less than that measured in a population without scoliosis (mean difference, 7.72 +/- 9.9 degrees). Seventy-four of 76 scolioses in the upper region of the spine with lateral curvature greater than 5 degrees Cobb were kyphotic. Sixty-four of 84 curves greater than 5 degrees Cobb in the lower region were lordotic. Measuring curvatures in the plane of symmetry of the rotated apical vertebra altered these ratios to 69 of 76 kyphotic in the upper region and 68 of 84 lordotic in the lower region. The plane of maximum curvature of sections of the spine with scoliosis was not related to the plane of symmetry of the rotated apical vertebra, for in kyphotic regions of the spine the rotations of these two planes were in opposite directions. In all cases, the magnitudes of the rotations were quite different, i.e., by a factor of -0.22 for curves in thoracic region and by a factor of 0.24 for curves in the lumbar region. This implies that mechanical measures to correct this spinal deformity or to prevent progression should apply different rotations to the apex from those applied to the curve as a whole and, in opposite senses, in curves in kyphotic regions. There was no evidence of an abnormality of sagittal curvature of a magnitude to implicate it in the etiology or in the treatment. 相似文献
997.
ABO blood group incompatible kidney transplantation: a case report and review of the literature 总被引:1,自引:0,他引:1
A patient with end-stage renal failure, two previously failed kidney transplants and high serum lymphocytotoxic antibody levels was transplanted electively with an ABO-mismatched, HLA-identical kidney from his sibling. Immunosuppression consisted of pretransplant splenectomy and plasma exchange, followed by rabbit antithymocyte serum, azathioprine, prednisone and plasma exchange in the early post-transplant period. He is now 3 years post-transplant with normal renal function on conventional immunosuppressive therapy. This case, and a review of the literature, suggest that ABO blood group incompatibility need not be an absolute barrier to successful kidney transplantation. ABO incompatible kidney transplantation may be a potentially fruitful area for further research as the demand for donor organs continues to outstrip the supply. 相似文献
998.
Extensor mechanism complications following 281 knee arthroplasties that included patellar resurfacing, performed by two surgeons in one hospital over a 6-year period, were reviewed. The mean follow-up period was 42 months. There were 28 (10%) extensor mechanism complications: 3 quadriceps tendon ruptures, 5 patellar fractures, 4 patellar tendon ruptures, 11 recurring patellar subluxations, 4 cases of patellar pain, and 1 malrotated patella. Nine (3%) required further surgery. Surgical technique may have contributed to the tendon ruptures; patellar fractures occurred mainly in patients who had rheumatoid arthritis. Patients with patellar subluxation had abnormal preoperative valgus deformities of their knees and presented with this subluxation problem an average of 4 months after surgery, but it appeared to cause them less discomfort with time. Patellar resurfacing as part of a knee arthroplasty procedure is recommended but should be performed with care to the integrity and vasculature of the extensor mechanism. 相似文献
999.
Predicting failure in polytetrafluoroethylene vascular access grafts for hemodialysis: a pilot study
C R Shackleton D C Taylor A R Buckley V A Rowley P L Cooperberg P D Fry 《Canadian journal of surgery》1987,30(6):442-444
In order to determine if serial, noninvasive evaluation of polytetrafluoroethylene (PTFE) vascular access grafts could identify a subgroup of patients at risk for thrombosis, the authors studied flow characteristics, using duplex ultrasonic scanning, in 18 hemodialysis patients with forearm loop grafts. On average, five examinations were performed per patient over the 10-month study period. Seven episodes of thrombosis occurred in six patients. The mean Doppler flow in grafts that subsequently thrombosed was significantly lower than in those that did not (544 +/- 218 ml/min versus 843 +/- 391 ml/min, p less than 0.001). The interval from last examination to thrombosis ranged from 13 to 58 days. At a defined cut-off flow of 450 ml/min, this test yielded a sensitivity of 83% and a specificity of 75% for episodes of thrombosis occurring within 2 to 6 weeks. The authors conclude that episodes of thrombosis in PTFE arm loop grafts are usually preceded by significantly lower Doppler-measured flow than grafts that do not thrombose and that it may be possible, by this means, to identify grafts at risk. 相似文献
1000.
EVA ÅKERLÖF B. FREDRICSON O. GUSTAFSSON A. LUNDIN† N. O. LUNELL L. NYLUND L. ROSENBORG Å. POUSETTE 《International journal of andrology》1987,10(5):663-669
Two methods of separating human sperm were compared using twenty-two semen samples. The sperm were separated by a swim-up technique or by self-migration on a Percoll gradient followed by medium change. After separation, the sperm obtained were assessed for progressive motility, ATP content, energy charge index ([ATP + 0.5 ADP]/[ATP + ADP + AMP]) and morphology. In general, and especially for semen samples containing less than 20 X 10(6) sperm/ml, separation by Percoll gradient selected sperm that were superior to those separated by the swim-up technique. The relatively high energy charge index (greater than 0.8) showed that the sperm tolerated the separation conditions well. It is suggested that self-migration on a Percoll gradient should prove useful for obtaining sperm of high quality. 相似文献