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   220443篇
  免费   18680篇
  国内免费   4648篇
耳鼻咽喉   3468篇
儿科学   4429篇
妇产科学   3706篇
基础医学   17901篇
口腔科学   7316篇
临床医学   21318篇
内科学   21475篇
皮肤病学   2424篇
神经病学   11065篇
特种医学   6469篇
外国民族医学   11篇
外科学   21134篇
综合类   34064篇
现状与发展   9篇
一般理论   24篇
预防医学   30490篇
眼科学   2001篇
药学   20632篇
  350篇
中国医学   26246篇
肿瘤学   9239篇
  2024年   976篇
  2023年   4431篇
  2022年   8376篇
  2021年   11044篇
  2020年   10663篇
  2019年   12145篇
  2018年   10615篇
  2017年   9038篇
  2016年   8084篇
  2015年   7486篇
  2014年   14927篇
  2013年   15135篇
  2012年   13151篇
  2011年   14158篇
  2010年   11343篇
  2009年   9954篇
  2008年   9253篇
  2007年   9253篇
  2006年   7822篇
  2005年   6580篇
  2004年   5506篇
  2003年   4895篇
  2002年   3721篇
  2001年   3097篇
  2000年   2767篇
  1999年   2247篇
  1998年   1802篇
  1997年   1614篇
  1996年   1329篇
  1995年   1269篇
  1994年   1161篇
  1993年   1029篇
  1992年   943篇
  1991年   855篇
  1990年   742篇
  1989年   721篇
  1988年   665篇
  1987年   604篇
  1986年   555篇
  1985年   1822篇
  1984年   2099篇
  1983年   1305篇
  1982年   1743篇
  1981年   1203篇
  1980年   1038篇
  1979年   930篇
  1978年   758篇
  1977年   574篇
  1976年   715篇
  1975年   486篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
The Low Vision Clinic at the Palmerston North Hospital has now been oerating for 70 years. Over the course of these ten years a number of factors have emerged which can be as readily applied to general ophthalmological practice as to low vision practice. The philosophy of low vision care is one of which all ophthalmologists should be aware and includes factors to be taken into account when dealing with children, people in the workplace, and everyday factors involved in daily living activities, all of which are equally relevant in routine ophthalmological practice. This paper endeavours to share some thoughts on these factors and also discusses means by which the visually handicapped can be helped in areas where specialist low vision services are not readily available.  相似文献   
22.
23.
目的 探讨老年人急性阑尾炎的临床特点,更好地把握腹腔镜阑尾切除(LA)术的方法和特点。方法 回顾分析50例老年人急性阑尾炎LA的临床资料。结果 LA均获成功,患者全部治愈,无严重的并发症发生,肠功能恢复时间及住院时间均缩短。结论 老年人反应迟钝,阑尾炎进展快,易发生坏疽及穿孔,合并症多,手术风险较高,LA是安全、可行的,除个别腹膜后阑尾炎外,其余均可施行LA。  相似文献   
24.
Summary— To investigate if the functional alterations observed in resistance arteries of spontaneously hypertensive rats (SHRs) were also present at the coronary level, in vitro experiments were performed in mesenteric resistance arteries (MRA) and in right (RIC) and left interventricular coronary (LIC) arteries taken from 15–25-week-old SHR and age-matched Wistar Kyoto rats WKYs. Using a passive extension protocol, internal diameters corresponding to 100 mmHg intraluminal pressure (D100) were determined and vessels were set up to a normalized internal diameter (0.9 D100). SHR mesenteric resistance arteries had a significantly smaller diameter compared to WKY arteries, whereas both types of SHR coronary arteries had a greater diameter compared to those of WKY rats. In arteries in the absence of contracting agonist, nitro-L-arginine (NOLA, 100 μM) induced a progressive rise in basal tone, which could be reversed by subsequent addition of L-arginine (100 μM) but not D-arginine (100 μM). When expressed as percent of maximal contractions induced by agonists (noradrenaline, NA [10 μM] in MRA; serotonin, 5-HT [10 μM], in RIC and LIC), these contractions were significantly stronger in WKY compared to SHR coronary and mesenteric resistance arteries. In NA-precontracted MRA and 5HT-precontracted coronary arteries in the presence of indomethacin (10 μM), the magnitude of acetylcholine-induced maximal relaxations (expressed as percent of maximal contractions induced by agonists) was greater in WKY compared to SHR arteries. After a 30-min incubation period, NOLA (100 μM) completely inhibited relaxations induced by acetylcholine (0.01–10 μM) in all types of precontracted arteries. Subsequent additions of sodium nitroprusside, (SNP, 10 μM) induced complete relaxations in all preparations. These results show that a basal release of NO or NO-like compound by endothelial cells is present in isolated mesenteric resistance and coronary arteries of WKY rats and SHRs. The contribution of endothelium-derived relaxing factor-nitric oxide (EDRF-NO) to arterial tone was lower in MRA compared to coronary arteries in both strains and in SHR compared to WKY arteries. In the SHR preparations, the impaired relaxation induced by acetylcholine appeared to be due to a functional alteration of the endothelium in the presence of normal reactivity of the smooth muscle cells.  相似文献   
25.
Examined are several measures currently used in the assessment of child abuse, sexual abuse, and trauma. These measures include structured clinical interviews, self report measures, screening inventory, symptom checklist, and some measures that include decision making properties. Issues and implications for clinical practice are explored.  相似文献   
26.
Summary Rats were treated with desipramine 5mg/kg, nomifensine 10mg/kg, zimelidine 25 mg/kg or with 0.9% sodium chloride once a day during the second and third weeks after birth, and brain stem, caudate/putamen and cortical monoamines, and caudate/putamen dopamine D1 (3[H]SCH 23390) and D2 (3[H]spiroperidol) receptor binding were measured when rats were at two months of age. In the brain stem, the concentration of 3-methoxy-4-hydroxy-phenyl glycol was increased in nomifensine rats and the ratio of 5-hydroxyindoleacetic acid to 5-hydroxytryptamine was increased in zimelidine rats. In the caudate/putamen, the concentrations of 3,4-dihydroxyphenylacetic acid and homovanillic acid and the ratio of homovanillic acid to dopamine were increased in desipramine rats; neither3[H]SCH 23390 nor3[H]spiroperidol binding were affected by any of the three monoamine uptake inhibiting antidepressants studied. In the cortex, the ratio of 5-hydroxyindoleacetic acid to 5-hydroxytryptamine was increased in desipramine and zimelidine rats. The findings suggest that desipramine but not nomifensine increases the metabolism of dopamine in the caudate/ putamen and nomifensine but not desipramine increases the metabolism of norepinephrine in the brain stem, and furthermore that the metabolism of serotonin is affected by desipramine as well as by zimelidine. It is possible that also treatment of women with these drugs during late pregnancy causes long-lasting changes in the brain of human fetus.  相似文献   
27.
This article identifies common characteristics of educationally related programs that form a common basis for understanding and working with gifted programs. Special approaches and programs for educational enrichment as well as specific activities that have been successful are discussed.  相似文献   
28.
Hepatocyte regeneration has been widely investigated, with the mitotic index and the incorporation of [3H]thymidine being used as regeneration markers. We focused on the induction of DNA replication enzymes, particularly DNA polymerases (pol) α, δ, and ε. Using rat models, we have shown that the activity of pol α in crude liver extract well represents the regenerating capacity of hepatocytes. Using pol α as an indicator, we analyzed liver regeneration in rat models under various conditions: obstructive jaundice, external or internal biliary drainage, and the obstruction of portal vein branches. It has been revealed that the ligation of the common bile duct alone induces a certain amount of hepatocyte proliferation. It was striking that external biliary drainage suppressed regeneration capacity in cholestatic rat liver after partial hepatectomy. The strong regeneration in nonligated lobes induced by portal branch ligation was similar to the liver regeneration seen after partial hepatectomy with respect to the induction of DNA polymerases. Taken together, the aspects of DNA replication, particularly the induction of DNA polymerases, may contribute to shedding new light on the regeneration of human liver. This work was supported in part by a Grant-in-Aid for General Scientific Research and for Cancer Research from the Ministry of Education, Science and Culture, Japan, and by grants from the Uehara Memorial Foundation  相似文献   
29.
? The paper describes a multiproject practice development programme undertaken over a period of 1 year. ? The background and development of the programme are outlined, whilst attention is paid to the innovatory nature of the work, particularly the use of inductive, deductive and integrated approaches to both change implementation and project supervision. ? The programme was monitored throughout using different data sources and the paper uses evaluative material retrospectively to provide answers to organizational and professional difficulties which arose during the course of the programme. ? The authors conclude that the use of combinations of different models for practice development has potential, but requires careful supervision. ? They also recommend that those involved in practice development are made fully aware of its local or micropolitics, and develop strategies to deal with change before it occurs, not after it has taken place.  相似文献   
30.
Abstract. Twenty-one patients were studied at rest and during exercise after heart transplantation to compare cardiac output measured by thermodilution and impedance cardiography. Exercise was performed on a bicycle ergometer over a limited range of work load (25 and 50 watt) whilst metabolic gas exchange was recorded. One patient was studied at rest whilst his circulation was maintained by a Jarvik-7 artificial heart. The values of cardiac output measured by impedance cardiography corresponded closely with the flow rate from the artificial heart. There was also close agreement between the impedance and thermodilution measurements of cardiac output at rest and during exercise. Both measurements followed the changes in heart rate and oxygen consumption. Both thermodilution and impedance cardiography methods elicited good reproducibility of cardiac output measurements at rest and during exercise. These observations suggest that the noninvasive and continuous record of cardiac output obtained by impedance cardiography can be used for the postoperative monitoring of heart transplant recipients.  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