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   1355777篇
  免费   105295篇
  国内免费   2163篇
耳鼻咽喉   19307篇
儿科学   46638篇
妇产科学   36908篇
基础医学   194513篇
口腔科学   35998篇
临床医学   118840篇
内科学   274047篇
皮肤病学   29230篇
神经病学   108147篇
特种医学   54195篇
外国民族医学   700篇
外科学   206562篇
综合类   27576篇
现状与发展   2篇
一般理论   454篇
预防医学   102834篇
眼科学   29345篇
药学   99846篇
  2篇
中国医学   2601篇
肿瘤学   75490篇
  2019年   10428篇
  2018年   14675篇
  2017年   11138篇
  2016年   12301篇
  2015年   13944篇
  2014年   19219篇
  2013年   29328篇
  2012年   40358篇
  2011年   42504篇
  2010年   25693篇
  2009年   24408篇
  2008年   40547篇
  2007年   43237篇
  2006年   43462篇
  2005年   42222篇
  2004年   41132篇
  2003年   39748篇
  2002年   38869篇
  2001年   66211篇
  2000年   68761篇
  1999年   58437篇
  1998年   16159篇
  1997年   14611篇
  1996年   14985篇
  1995年   14164篇
  1994年   13413篇
  1993年   12466篇
  1992年   46070篇
  1991年   44880篇
  1990年   43554篇
  1989年   41420篇
  1988年   38024篇
  1987年   37362篇
  1986年   34741篇
  1985年   33318篇
  1984年   24909篇
  1983年   20963篇
  1982年   12196篇
  1981年   11158篇
  1979年   22050篇
  1978年   15224篇
  1977年   12934篇
  1976年   12004篇
  1975年   13032篇
  1974年   15103篇
  1973年   14510篇
  1972年   13341篇
  1971年   12103篇
  1970年   11352篇
  1969年   10293篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Tracheomalacia is commonly associated with oesophageal atresiaand tracheo-oesophageal fistula. Severe cases may present withlife threatening cyanotic and apnoeic attacks following surgicalrepair of the oesophageal atresia. The anaesthetic, and surgicalmanagement (by tracheopexy), of such a case are described.  相似文献   
992.
993.
Failure of genetically selected miniature swine to model NIDDM   总被引:2,自引:0,他引:2  
Ten young adult miniature swine from a line reported to be genetically selected for glucose intolerance and eight normal controls were obtained from Colorado State University. They were consecutively exposed to 4 mo of a high-fiber, low-fat standard swine diet; 4 mo of a high-sucrose, high-fat, low-fiber diabetogenic diet; and 4 mo of excess diabetogenic diet for obesification. Results of oral glucose tolerance and intravenous insulin tolerance tests conducted at the end of each regimen were compared. Hyperglycemia was not observed in any animals after any manipulation. Insulin sensitivity was also not influenced by diet. We conclude that F7 low-K miniature swine from this colony fail to model human non-insulin-dependent diabetes.  相似文献   
994.
995.
Serum protein electrophoresis (SPEP) data obtained at diagnosis were available for 98 of 342 patients with chronic lymphocytic leukemia (CLL) identified in a population-based case-control epidemiologic study. Patients tested with SPEP at diagnosis were significantly younger, more likely to have lymphadenopathy, and more likely to have had their conditions diagnosed at a university hospital than those not tested. Four categories of electrophoretic patterns were identified: normal (N = 56), hypogammaglobulinemia (N = 28), hypergammaglobulinemia (N = 11), and monoclonal gammopathy (N = 3). A higher proportion of those with hypergammaglobulinemia were black, and patients with hypergammaglobulinemia and monoclonal gammopathy were more likely to die within the first year following diagnosis than patients in the other SPEP groups. No association was found, however, between SPEP pattern and a clinical staging classification for CLL. These findings suggest that SPEP may be a useful adjunct in categorizing possible subtypes of CLL and developing future clinical staging classifications.  相似文献   
996.
The electrocardiographic features of Noonan's syndrome have been known for several years, but the discordance between these electrical findings and the underlying haemodynamic disorders remains unexplained. In an attempt to elucidate the genesis of electrical abnormalities, we present here a retrospective study of 14 children with Noonan's disease, aged from a few days to 16 years and evaluated by electrocardiography, vectography, one- or two-dimensional echocardiography, angiography and His bundle electrophysiology. The electrocardiographic abnormalities observed concerned ventricular depolarization and intracardiac electric conduction with, notably, a QRS axis directed towards the right upper part of the electric field and a first degree infra-hisian atrioventricular block (His bundle potentials). Vectography showed in some cases an image of inferior pseudo-necrosis due to the absence of initial inferior forces; this image is highly characteristic. In other cases the QRS loop showed an image of left segmental block which is unusual in this type or cardiac pathology (pulmonary stenosis with or without atrial septal defect of the ostium secundum type).  相似文献   
997.
Current concepts in clinical therapeutics: anxiety disorders, Part 2   总被引:1,自引:0,他引:1  
  相似文献   
998.
The fate of isoprene inhaled by rats: comparison to butadiene   总被引:1,自引:0,他引:1  
Isoprene (2-methyl-1,3-butadiene), a volatile monomer occurring in the natural environment and used in the manufacture of elastomers, is a close chemical relative of the animal carcinogen 1,3-butadiene. To obtain toxicokinetic data for inhaled isoprene, male F344 rats were exposed in groups of 30 to 14C-labeled isoprene vapor at four concentrations from 8 to 8200 ppm. The percentage of the inhaled isoprene that was metabolized decreased with increasing exposure concentration. The percentage of the total metabolites (that is, non-isoprene-retained 14C) excreted in urine and feces or expired was determined as a function of vapor concentration. About 75% of the total metabolites was excreted in urine. This was independent of inhaled isoprene concentration. After exposure to 8200 ppm, a larger percentage of the metabolites was excreted in feces than after exposure to lower concentrations. Using vacuum line techniques, blood metabolite concentrations were determined as functions of both vapor concentration and exposure duration. At one exposure concentration (1480 ppm) metabolites were measured in the nose, lungs, liver, kidney, and fat, as well as in blood. A mutagenic metabolite, isoprene diepoxide, was tentatively identified in all tissues examined. Between 0.0018 and 0.031% of the inhaled 14C label was tentatively identified as this metabolite in blood. The relative amount of the metabolites present in blood was highest for low concentrations of inhaled isoprene and for shorter exposure durations. Body fat appeared to be a reservoir for both isoprene metabolites and isoprene itself. The appearance of metabolites in the respiratory tract after short exposure durations together with low blood concentrations of isoprene indicated that substantial metabolism of inhaled isoprene in the respiratory tract may occur.  相似文献   
999.
3-(Methylnitrosamino)propionitrile (MNPN), a potent carcinogen in F344 rats, was detected for the first time in the saliva of betel quid chewers at levels ranging from 0.5 to 11.4 micrograms/liter. The tumorigenic properties of MNPN and its potential to methylate DNA in F344 rats were evaluated. Groups of 21 male and 21 female rats were given 60 s.c. injections over a 20-week period (total doses 0.055 and 0.23 mmol per rat). The experiment was terminated after 106 weeks. MNPN at the higher dose induced 18 (86%) malignant tumors of the nasal cavity in male and 15 (71%) in female rats. The lower dose induced nine (43%) liver tumors. Groups of four or five male F344 rats were treated with a single s.c. or i.v. injection of MNPN (0.4 mmol/kg). MNPN was also administered to rats by swabbing the oral cavity (2.21 mmol/kg). The levels of 7-methylguanine and O6-methylguanine, formed 0.5-36 h after treatment, were measured in the liver, nasal mucosa, esophagus, and oral issues. The highest levels of methylated guanines were detected in the nasal cavity independent of the route of administration. The results of this study demonstrate that MNPN is present in the saliva of betel quid chewers and is a potent carcinogen in F344 rats.  相似文献   
1000.
Relatives of 22 schizotypal probands were evaluated for lifetime psychiatric diagnoses. Forty-four (N = 44) of the 97 available relatives were interviewed directly using the Diagnostic Interview Schedule. The rates of psychiatric diagnoses were compared with those of sixty-six (N = 66) of 140 relatives of 30 depressed patients. Family history of mental illness was ascertained by the informant method on the remainder of relatives of both proband groups. The rate of depression found in the relatives of schizotypal patients was 52% in those directly interviewed and 25.7% when informants' reports on unavailable relatives are pooled with direct interview data. These rates were not significantly higher than those found for the relatives of depressed probands (34.8% by direct interview and 21% including reports from informants). The high rates of depression in the relatives of schizotypal probands may indicate that schizotypal personality is associated with affective disorder and not only with schizophrenia. However, the high rates may be due to the presence of depressive character traits in relatives, which inflate the rates of dysthymic disorder and other chronic depressive disorders in the relatives of borderline patients.  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