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   45040篇
  免费   5109篇
  国内免费   167篇
耳鼻咽喉   323篇
儿科学   1323篇
妇产科学   900篇
基础医学   6226篇
口腔科学   1247篇
临床医学   5712篇
内科学   8903篇
皮肤病学   698篇
神经病学   3615篇
特种医学   1878篇
外国民族医学   1篇
外科学   5954篇
综合类   1190篇
一般理论   26篇
预防医学   5248篇
眼科学   846篇
药学   3790篇
中国医学   78篇
肿瘤学   2358篇
  2021年   586篇
  2020年   357篇
  2019年   644篇
  2018年   734篇
  2017年   526篇
  2016年   601篇
  2015年   713篇
  2014年   941篇
  2013年   1376篇
  2012年   1990篇
  2011年   2001篇
  2010年   1131篇
  2009年   1104篇
  2008年   1901篇
  2007年   2051篇
  2006年   1971篇
  2005年   1900篇
  2004年   1744篇
  2003年   1661篇
  2002年   1626篇
  2001年   1541篇
  2000年   1478篇
  1999年   1465篇
  1998年   624篇
  1997年   490篇
  1996年   502篇
  1995年   493篇
  1994年   441篇
  1993年   479篇
  1992年   1216篇
  1991年   1127篇
  1990年   1082篇
  1989年   1051篇
  1988年   980篇
  1987年   976篇
  1986年   987篇
  1985年   900篇
  1984年   773篇
  1983年   634篇
  1982年   427篇
  1981年   352篇
  1979年   587篇
  1978年   485篇
  1977年   373篇
  1976年   386篇
  1974年   433篇
  1973年   400篇
  1972年   386篇
  1971年   350篇
  1969年   358篇
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
61.
Motility disorders of the gastrointestinal (GI) tract have traditionally been diagnosed by excluding mechanical small-bowel obstruction. In order to diagnose GI motility disorders in a positive fashion, small-bowel manometry was performed on 15 patients who were referred to the authors with intestinal motility disorders. Intestinal manometry was performed after first positioning a 200-cm multilumen tube into the small intestine. Ports located at 10-cm intervals were perfused with sterile water and connected to pressure transducers to record intraluminal pressures with a multichannel chart recorder. This low compliance water perfusion manometry system allowed examination of both fasting and postprandial motility. Intestinal manometry was able to assist in the diagnosis of two patients that had true mechanical small-bowel obstruction. One patient had a stenosis of the gastrojejunostomy and three patients had a functional gastric outlet obstruction secondary to a motility disorder in the Roux limb. One patient had a functional obstruction from a reversed jejunal loop and eight patients were identified as having intestinal pseudo-obstruction. We found intestinal manometry was a helpful adjunct in the diagnosis of GI motility disorders.  相似文献   
62.
Vibration perception threshold was measured with a biothesiometer by a single observer at both medial malleoli and both big toes in 110 diabetic patients aged 15-65 selected at random and in 64 non-diabetic subjects aged 20-65. The vibration perception threshold showed appreciable individual variation both between contralateral sites and between ipsilateral sites, differing by at least 30% between the big toes in 26 (24%) of the diabetic patients and 16 (25%) of the non-diabetic group. Variability between sites was significantly greater in the diabetics than the normal subjects. The vibration perception threshold exceeded published normal values at one or more sites in 22 of the diabetic patients but at all four sites in only four. The wide variability in vibration perception threshold among sites may be due to the tissue characteristics locally and, in diabetic patients, possibly to asymmetric neuropathy. Biothesiometer readings at single or unilateral sites may be unrepresentative or misleading.  相似文献   
63.
64.
65.
Many prostatectomies are performed on the basis of symptoms alone; 39% of patients referred by their family doctors and 23% of patients who were on waiting lists for prostatectomy of other hospitals, but who had not undergone any urodynamic investigations, were found to be unobstructed on urodynamic criteria. A screening peak urinary flow rate of 12 ml/s or less was associated with urodynamic evidence of obstruction in 95% of cases; 35% of patients with symptoms of outflow obstruction and a flow rate greater than 12 ml/s were also found to be obstructed. One year post-operatively, 84% of patients who were selected for surgery on combined symptomatic and urodynamic criteria were pleased symptomatically with their result. The failure of detrusor instability to resolve following prostatectomy was associated with symptomatic failure of treatment. Residual obstruction was demonstrated in 5 patients who had undergone prostatectomy and were asymptomatic at this time. This study illustrates that objective measures are necessary in the assessment of patients prior to prostatectomy in order to select only patients who are obstructed. The importance of a screening flow rate is emphasised. All patients who underwent surgery had cystometric evidence of obstruction but the symptomatic results of surgery were no better than the results in patients who had been assessed according to non-urodynamic selection criteria. We have thus failed to identify a need for routine cystometry in the pre-operative assessment of these patients. Cystometry does, however, have a role in assessing patients with pre-operative flow rates greater than 12 ml/s and in those who remain symptomatic following prostatectomy.  相似文献   
66.
The American approach to drug control is conditioned by several national characteristics, including fragmentation of the law enforcement system, a 12,000-mile international boundary and a legal system that restricts police authority to search, arrest, detain, eavesdrop and maintain intelligence files. Drug problems in the United States, though, are by all accounts greater than in any other country. Enforcement has traditionally emphasized street-level arrests, investigation of distribution networks, crop eradication and smuggling interdiction. These practices can be shown to produce arrests and seizures, but there is little evidence to show that they reduce drug supply or drug abuse. More contemporary and promising approaches include community policing, problem-oriented policing, financially oriented investigations, increased international co-operation and a renewed emphasis on drug demand reduction. The most pressing needs in law enforcement are (a) improved intelligence-gathering and analysis and (b) research on the illicit drug industry and on the effectiveness of drug control strategies.  相似文献   
67.
The talar beak is a well-described secondary sign of talocalcaneal coalition but is not pathognomonic of the condition and may be seen in other causes of restricted or abnormal subtalar motion. We present an unusual complication of talar beaks in two patients who sustained fractures through their beaks. One of the patients described did not have a talocalcaneal coalition but had developed a beak following a compound fracture dislocation of the ankle joint complicated by infection, a previously undescribed predisposing cause.  相似文献   
68.
A family of P-glycoproteins are overproduced in multidrug-resistant cells derived from the murine macrophage-like line J774.2. To determine whether individual family members are overproduced in response to different drugs, the P-glycoprotein precursors in several independently isolated cell lines, which were selected for resistance to vinblastine or taxol, were compared. Individual cell lines selected with vinblastine overproduced P-glycoprotein precursors of either 120 or 125 kDa. Taxol-selected cell lines overproduced either the 125-kDa precursor or both precursors simultaneously. Two similar but distinct peptide maps for the mature P-glycoproteins were observed. These maps corresponded to each precursor regardless of the drug used for selection. One vinblastine-resistant cell line switched from the 125- to the 120-kDa precursor when grown in increasing concentrations of drug. This change coincided with the overexpression of a distinct subset of mRNA species that code for P-glycoprotein. It is concluded that precursor expression is not drug-specific. These data suggest that individual overproduced P-glycoprotein family members are translated as distinct polypeptides. The results may help to explain the diversity in the multidrug-resistant phenotype.  相似文献   
69.
1. The present study aimed to determine the feasibility of conducting a 5 year cardiovascular outcome trial of the treatment of 6000 elderly hypertensive patients in Australian general practices. 2. General practitioners (GPs) were invited to participate by mail and personal follow-up. Patient records were reviewed to identify subjects for a blood pressure (BP) screening programme. Blood pressure was measured on three occasions and eligible subjects were included if the average BP was 160 mmHg systolic or 90 mmHg diastolic if systolic BP was 140 mmHg. 3. Seven hundred and forty-one GPs were approached and 89 were enrolled in the study (12% of mail invites and 75% of those receiving a personal contact). In 16 practices where screening was completed, 82 000 records were reviewed to identify 4% patients eligible for screening. Twenty-two per cent of eligible subjects attended screening. Of 1938 subjects screened, 180 (9%) had BP 5=160/90 mmHg. Forty-seven percent of subjects (n = 916) were receiving antihypertensive therapy and 184 (20%) were withdrawn from therapy. One hundred and sixteen (63%) of these subjects had BP return to study entry levels within 6 weeks. Fifty-seven newly diagnosed and 81 previously treated subjects were randomized (7% of the screened population). 4. Based on the high participation rate of GPs, the response rate of patients to attend a BP screening programme and the 7% randomization to screening ratio for entry into the study, the ANBP2 pilot study has demonstrated that it is feasible to recruit subjects from Australian general practices to a cardiovascular outcome trial.  相似文献   
70.
A case study of multicentric reticulohistiocytosis is presented with extensive immunohistochemical studies of the infiltrate in both paraffin and cryostat sections. These studies showed that the cells are of monocyte/macrophage origin. B- and T-cell gene rearrangement analysis of multicentric reticulohistiocytosis was also performed and showed a germline configuration.  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