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   61006篇
  免费   4102篇
  国内免费   193篇
耳鼻咽喉   639篇
儿科学   1859篇
妇产科学   1964篇
基础医学   8306篇
口腔科学   967篇
临床医学   7842篇
内科学   11819篇
皮肤病学   1117篇
神经病学   6287篇
特种医学   1747篇
外国民族医学   4篇
外科学   6100篇
综合类   892篇
一般理论   80篇
预防医学   6137篇
眼科学   1099篇
药学   4154篇
中国医学   102篇
肿瘤学   4186篇
  2023年   267篇
  2022年   494篇
  2021年   1077篇
  2020年   633篇
  2019年   1024篇
  2018年   1240篇
  2017年   939篇
  2016年   1075篇
  2015年   1271篇
  2014年   1762篇
  2013年   2564篇
  2012年   3899篇
  2011年   4091篇
  2010年   2085篇
  2009年   2043篇
  2008年   3544篇
  2007年   3872篇
  2006年   4038篇
  2005年   3873篇
  2004年   3717篇
  2003年   3573篇
  2002年   3322篇
  2001年   1041篇
  2000年   966篇
  1999年   869篇
  1998年   740篇
  1997年   638篇
  1996年   508篇
  1995年   497篇
  1994年   368篇
  1993年   443篇
  1992年   559篇
  1991年   517篇
  1990年   529篇
  1989年   509篇
  1988年   489篇
  1987年   456篇
  1986年   414篇
  1985年   406篇
  1984年   368篇
  1983年   351篇
  1982年   345篇
  1981年   284篇
  1980年   273篇
  1979年   311篇
  1978年   229篇
  1977年   231篇
  1975年   233篇
  1974年   251篇
  1973年   207篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
61.
Distance learning in a school nurse credential program.   总被引:4,自引:0,他引:4  
Distance learning, which encompasses many methodologies, is becoming a more readily available educational alternative. Because there are a limited number of school nurse credential programs and the demand for school nurses is increasing, distance learning may be a viable method of instruction. This article describes the authors' experiences organizing and presenting distance learning courses to five remote sites for students in a university school nurse credential program. After numerous inquiries, potential students from several areas were surveyed, and arrangements were made with universities in those areas to receive two-way audio and video transmissions of two seminar courses; later, two clinically oriented courses in the school nurse program. Students were able to complete their program requirements by taking equivalent course work at their local universities. Perceptions of students and the instructor, course evaluation, and practical suggestions are shared. Guidelines for potential students about selecting quality distance education programs are also noted.  相似文献   
62.
BACKGROUND: The efficacy of nasal continuous positive airway pressure (nCPAP) as a prophylactic method for preventing cardiopulmonary complications after major vascular surgery has not been investigated. PATIENTS/METHODS: In a prospective randomized trial, 204 patients undergoing elective midline laparotomy for vascular surgery were randomized to receive standard therapy ( n=105) or additional prophylactic nCPAP ( n=99) for the first postoperative night. Postoperative oxygenation, incidence of severe cardiac, and pulmonary complications, length of intensive care surveillance and length of total postoperative hospital stay (LOS) were compared. RESULTS: Prophylactic nCPAP significantly reduced the number of patients with severe oxygenation disturbances defined as paO(2) < 70 mmHg with FiO(2) > or = 0.7 (5 versus 17, P=.01). There were no differences with respect to death, cardiac and pulmonary complications, length of intensive care surveillance or LOS. CONCLUSION: Prophylactic 12 h nCPAP significantly reduces the occurrence of postoperative oxygenation disturbances but has no effect on cardiac or pulmonary complications, need for intensive care, LOS or mortality after major vascular surgery.  相似文献   
63.
Lymphoid neogenesis is the process by which ectopic lymphoid accumulations that resemble lymph nodes arise in nonlymphoid tissues. Such lymphoid accumulations, known as tertiary lymphoid organs (TLO), are observed in chronic autoimmunity and they propagate immune pathology by setting up local antigen presenting sites. Whether lymphoid neogenesis occurs in transplanted organs and contributes to rejection is not well understood. To begin to address this question, we retrospectively analyzed 319 murine cardiac allografts for microscopic evidence of lymph-node-like structures. We found 78 allografts that had either classical TLO, characterized by discrete T- and B-cell zones and high endothelial venules (HEV) expressing peripheral node addressin (PNAd) (n = 34), or PNAd(+) HEV without organized lymphoid accumulations (n = 44). These changes were present in both short- and long-lived allografts and were invariably associated with rejection. Importantly, they occurred in 78% of allografts undergoing chronic rejection (n = 85) but in only 7% of allografts undergoing primarily acute rejection (n = 184). These findings indicate that, like autoimmunity, alloimmunity is associated with lymphoid neogenesis in the target organ and suggest a role for local T-cell activation in chronic allograft rejection.  相似文献   
64.
Metabolic syndrome is associated with increased risk for cardiovascular and cerebrovascular disease. The World Health Organization and National Cholesterol Education Program Adult Treatment Panel III have identified physiologic abnormalities associated with metabolic syndrome, including impaired glucose metabolism, high blood pressure, elevated cholesterol levels, and abdominal obesity. It is estimated that 47 million Americans have metabolic syndrome. A variety of therapies may help reduce the incidence and risk, including diet, weight loss, physical exercise, glycemic control, and pharmacological treatments. Nursing care is focused on developing an individualized plan of care that includes family members and providing education, psychosocial support, close monitoring, and continued follow-up to ensure adherence and success in achieving patient outcomes.  相似文献   
65.
66.
67.
68.
ObjectiveTo assess for the presence of gastric dysmotility in familial and sporadic Parkinson disease (PD).Methods10 subjects with familial Parkinson disease (fPD), 35 subjects with sporadic Parkinson disease (sPD), and 15 controls, all from academic tertiary care movement disorders centers, were studied. fPD was defined as the presence of at least 2 affected individuals within 2–3 consecutive generations in a family. Molecular genetic analysis has not revealed, thus far, any known genomic abnormality in these families. Gastric emptying was assessed by dynamic abdominal scintigraphy over 92 min following ingestion of a solid meal containing 99mTc-labeled colloid of 40 MBq activity. The main outcome measures were gastric emptying half-time and radiotracer activity over the gastric area at 46 and at 92 min.ResultsGastric emptying time was delayed in 60% of subjects with PD. In comparison to mean t1/2 of 38 ± 7 min in controls, mean t1/2 was 58 ± 25 min in fPD (p = 0.02) and 46 ± 25 min in sPD (p = 0.10). Both fPD and sPD groups included subjects with delayed gastric emptying at an early stage of disease.ConclusionsPatients with fPD showed significantly delayed gastric emptying in comparison to normal age-matched individuals. Further studies of gastrointestinal dysfunction in PD, particularly fPD, are warranted.  相似文献   
69.
Lesion evolution during focal cerebral ischemia may depend on flow restrictions or on accumulation of toxic mediators within the infarct and expansion of these factors to the periinfarct region. So far, the precise contribution of flow dependent versus spreading-mediated impairment of viable periinfarct tissue has not been determined. Therefore, we measured lesion expansion, flow restrictions and glutamate distribution on serial brain sections at different time points after experimental focal ischemia.Permanent focal ischemia was induced by occlusion of the right middle cerebral artery in male rats and the flow reduction was subsequently measured at 1, 12 and 24 h using iodo[14C]antipyrine autoradiography. Additionally, the necrotic volume was determined on serial brain sections and the glutamate content was measured in tissue samples from adjacent microdissections.Twelve hours after focal ischemia no noteworthy viable areas with blood flow restrictions of 20-40 ml 100 g− 1 min− 1 existed but at 24 h the necrotic tissue exceeded the hemodynamically compromised region by 40 ± 21 mm3 (24%). Furthermore, at 12 and 24 h the glutamate content was elevated in areas surrounding the infarct.Relevant flow restrictions are detectable only during early stages of infarct maturation, whereas the propagation of secondary factors may be the predominant mechanism for delayed infarct evolution.  相似文献   
70.
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