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   4741篇
  免费   301篇
  国内免费   14篇
耳鼻咽喉   76篇
儿科学   100篇
妇产科学   93篇
基础医学   651篇
口腔科学   41篇
临床医学   382篇
内科学   1010篇
皮肤病学   46篇
神经病学   353篇
特种医学   184篇
外科学   743篇
综合类   81篇
一般理论   4篇
预防医学   315篇
眼科学   243篇
药学   364篇
中国医学   30篇
肿瘤学   340篇
  2023年   35篇
  2022年   40篇
  2021年   110篇
  2020年   52篇
  2019年   90篇
  2018年   121篇
  2017年   66篇
  2016年   79篇
  2015年   110篇
  2014年   116篇
  2013年   217篇
  2012年   281篇
  2011年   273篇
  2010年   202篇
  2009年   152篇
  2008年   244篇
  2007年   245篇
  2006年   232篇
  2005年   219篇
  2004年   203篇
  2003年   171篇
  2002年   174篇
  2001年   117篇
  2000年   138篇
  1999年   117篇
  1998年   48篇
  1997年   33篇
  1996年   42篇
  1995年   29篇
  1994年   43篇
  1993年   35篇
  1992年   79篇
  1991年   98篇
  1990年   71篇
  1989年   78篇
  1988年   80篇
  1987年   78篇
  1986年   44篇
  1985年   51篇
  1984年   35篇
  1983年   25篇
  1982年   38篇
  1981年   26篇
  1980年   30篇
  1979年   28篇
  1978年   27篇
  1977年   22篇
  1976年   20篇
  1974年   18篇
  1971年   14篇
排序方式: 共有5056条查询结果,搜索用时 31 毫秒
1.
2.
Sniff nasal inspiratory pressure (SNIP) measurement is a volitional noninvasive assessment of inspiratory muscle strength. A maximum of 10 sniffs is generally used. The purpose of the present study was to investigate whether the maximum SNIP improved after the tenth sniff. In total, 20 healthy volunteers and 305 patients with various neuromuscular and lung diseases were encouraged to perform 40 and 20 sniffs, respectively. The best SNIP among the first 10 sniffs was lower than the best SNIP among the next 10 sniffs in the healthy volunteers and patients. The SNIP improvement after the twentieth sniff was marginal. In conclusion, a learning effect persists after the tenth sniff. The current authors suggest using 10 additional sniffs when the best result of the first 10 sniffs is slightly below normal, or when sniff nasal inspiratory pressure is used to monitor a progressive decline in inspiratory muscle strength.  相似文献   
3.
Atherosclerotic renal artery stenosis (ARAS) may cause hypertension, progressive renal failure, and recurrent pulmonary edema. It typically occurs in high risk patients with coexistent vascular disease elsewhere. Most patients with ARAS are likely to die from coronary heart disease or stroke before end-stage renal failure occurs. Recent controlled trials have shown that most patients undergoing angioplasty to treat renovascular hypertension still need antihypertensive agents 6 or 12 months after the procedure. Nevertheless, the number of antihypertensive agents required to control blood pressure adequately is lower following angioplasty than for medication alone. Trials assessing the value of revascularization for preserving renal function or preventing clinical events are only in the early recruitment phase. Revascularization should be undertaken in patients with ARAS and resistant hypertension or heart failure, and probably in those with rapidly deteriorating renal function or with an increase in plasma creatinine levels during angiotensin-converting enzyme inhibition. With or without revascularization, medical therapy using antihypertensive, hypolipidemic and antiplatelet agents is necessary in almost all cases.  相似文献   
4.
In the brain of quaking and shiverer mutants, vitamin E content was normal when related to both wet weight and dry weight. When related to lipid extract, phosphorus, and polyunsaturated fatty acids, vitamin E was slightly increased only in the quaking mutant. In the sciatic nerve from trembler mutants, vitamin E was 134% of control values in the dry material, but normal in relation to wet weight. It was 260% in the lipid extract and 716% based on phosphorus. In relation to total fatty acids, there was a threefold increase in trembler mutants. Interestingly, it was increased approximately three times when related to 18∶2 n?6, 20∶4 n?6, and 20∶5 n?3, and seven times when related to 22∶6 n?3. The fact that the amount of vitamin E in fresh weight was normal, suggests that vitamin E plays a role in some nonmembrane material, such as the extracellular matrix or the basal lamina.  相似文献   
5.
6.
The present study aimed to determine the alterations of antioxidant activities in erythrocytes from patients with nonsmall cell lung carcinoma (NSCLC). A comparative study of the systemic antioxidant activities in red blood cell lysate from subjects with NSCLC and healthy control subjects was conducted. The antioxidants catalase, superoxide dismutase (SOD) and glutathione peroxidase (GPx) were measured using chemical kinetic reactions under spectrophotometry. In total, 189 cases of mostly advanced-stage IIIB or stage IV NSCLC and 202 healthy controls were studied. In subjects with lung cancer, there was similar catalase activity, lower SOD activity (median (interquartile range) 13.4 (9.0-27.2) versus 48.7 (27.0-64.3) U x (ghaemoglobulin(Hb)(-1)), and higher GPx activity (175.2 (126.6-288.3) versus 49.2 (39.5-59.2) mU x (gHb)(-1)) compared with controls. The antioxidant activities in lung cancer subjects were not associated with age, sex, smoking status, or tumour cell types. However, more advanced disease (stage IV compared with stage IIIB) was associated with lower SOD activity. Using multivariable analysis, the presence of lung cancer independently predicted SOD and GPx activities. In conclusion, nonsmall cell lung carcinoma in Chinese subjects is associated with alterations in systemic antioxidant activities, which may play an important role in carcinogenesis.  相似文献   
7.
8.
9.
In contrast to the systolic blood pressure at the posterior tibial artery, the evaluation of pressure at the digital artery of the foot before and after exercise in patients with peripheral arterial disease is not well known. Twenty three patients with peripheral vascular disease were examined. The systolic pressure was measured by means of an ultrasound velocity detector at the brachial and posterior tibial artery. Digital artery pressure was determined with photoplethysmography. Pressures were measured before and within 5 and 10 minutes after a treadmill test. Ankle and toe index was calculated. At rest the toe index is lower than the ankle index and after a treadmill test the decrease in toe index occurs in parallel to the ankle index.  相似文献   
10.
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