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   45628篇
  免费   5029篇
  国内免费   72篇
耳鼻咽喉   324篇
儿科学   1330篇
妇产科学   903篇
基础医学   6252篇
口腔科学   1226篇
临床医学   5682篇
内科学   8934篇
皮肤病学   721篇
神经病学   3615篇
特种医学   1909篇
外国民族医学   1篇
外科学   6043篇
综合类   1412篇
一般理论   26篇
预防医学   5278篇
眼科学   848篇
药学   3774篇
中国医学   77篇
肿瘤学   2374篇
  2021年   589篇
  2020年   358篇
  2019年   646篇
  2018年   737篇
  2017年   527篇
  2016年   600篇
  2015年   730篇
  2014年   947篇
  2013年   1378篇
  2012年   2002篇
  2011年   2002篇
  2010年   1160篇
  2009年   1132篇
  2008年   1931篇
  2007年   2036篇
  2006年   2018篇
  2005年   1915篇
  2004年   1785篇
  2003年   1675篇
  2002年   1639篇
  2001年   1553篇
  2000年   1486篇
  1999年   1486篇
  1998年   620篇
  1997年   505篇
  1996年   516篇
  1995年   508篇
  1994年   449篇
  1993年   474篇
  1992年   1214篇
  1991年   1129篇
  1990年   1078篇
  1989年   1045篇
  1988年   982篇
  1987年   973篇
  1986年   986篇
  1985年   902篇
  1984年   781篇
  1983年   637篇
  1982年   431篇
  1981年   354篇
  1979年   586篇
  1978年   487篇
  1977年   373篇
  1976年   382篇
  1974年   432篇
  1973年   400篇
  1972年   386篇
  1971年   349篇
  1969年   358篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Preoperative cytologic examinations were performed on bronchial material from 92 patients with postsurgical (pathologic) stage I (American Joint Committee) adenocarcinoma of the lung. All patients were followed up for at least 5 years or until death; thus, cases of adenocarcinoma metastatic to the lungs were virtually excluded. Only 22 patients (24%) had abnormal preoperative cytologic findings. This low cytologic sensitivity is ascribed to the small size and peripheral location of the tumors. Large lesions of high histologic grades were more likely to have positive preoperative cytologic findings than small, well-differentiated ones.  相似文献   
82.
The length of the thoracic spine was measured in chest roentgenograms of 331 children from birth to 16 years and standards for thoracic spine length in this age group were obtained.  相似文献   
83.
Aspects of humoral and cell-mediated immunity that might characterize the continuation of symptoms in 25 patients with chronic Meniere's disease were examined. We found significant elevations of both humoral and cellular immune responses to viral antigens of herpes simplex I, varicella-zoster, rubella, and cytomegalovirus. Serum immunoglobulins were quantitatively abnormal in 24 of 25 patients, without a consistent pattern. These immune responses may be linked to persistent viral infection in chronic Meniere's disease.  相似文献   
84.
The short-term albumin affinity and thrombo-resistance of a polyether polyurethane vascular graft have been improved. The method is based on the C18 alkylation of the polymer. Thrombus formation by a planimetric technique and albumin retention on wire-reinforced polyurethane tubes, both C18 alkylated and untreated, were measured in short-term (4-h) exposure at femoral arterial sites in the dog. 125I-Albumin was preabsorbed on tubes and then exposed to blood for successive 2-h periods. Albumin uptake on alkylated tubes prior to blood exposure and retention following 2 h of blood exposure were significantly greater than on controls. Following a fast desorption phase in blood, the remaining albumin was more slowly desorbed from alkylated than from control tubes. Reincubation with albumin and blood reexposure produced a similar tendency, suggesting blood conditioning does not reduce the albumin affinity-enhancing property of C18 alkylation in the short term. Blood-preconditioning experiments suggested endogenous albumin has a high affinity for the C18-alkylated surface. Scanning electron microscopic examination showed thrombus and platelet densities were higher on control than on alkylated surfaces. These results suggest in vivo albumin affinity is increased for C18-alkylated polyurethane, which may be linked to decreased thrombus formation on these surfaces.  相似文献   
85.
The effect of cirrhosis on the accuracy of ultrasonography and scintigraphy in the diagnosis of hepatocellular carcinoma (HCC) has not been established. We have therefore studied the findings on ultrasound and scintigraphy in four groups of patients. Fourteen had HCC and cirrhosis, 13 had HCC but no cirrhosis, 53 had cirrhosis but no HCC and 31 had evidence neither of cirrhotic nor malignant liver disease. The accuracies of a positive interpretation of HCC on ultrasound and scintigraphy in the absence of cirrhosis were 85% and 66% respectively (NS), but fell (significantly in the case of scintigraphy: p less than 0.05) to 80% and 31% respectively in the presence of cirrhosis (p less than 0.01). The poorer performance of scintigraphy in the presence of cirrhosis was a result both of its lower sensitivity (50% compared with 85%) and the greater frequency of false positives (28% vs 5%: p less than 0.001). The accuracy of a negative interpretation of HCC on scintigraphy in the absence of cirrhosis was 96% but fell to 84% in the presence of cirrhosis, whereas on ultrasound it remained the same (96%). In conclusion, we recommend ultrasound in preference to scintigraphy as a more accurate technique for the diagnosis of HCC in the presence of cirrhosis.  相似文献   
86.
Extradural sacral (caudal) block was performed in 17 cases (14 patients) of chronic low back pain. In each case 22 ml of a bupivacaine/methylprednisolone solution incorporating a radioopaque dye was injected over a 2-min period. Patients were randomly assigned to receive the injection in the horizontal position or with 15 degrees head-up or head-down tilt applied to the operating table. Results indicate that analgesia is usually more localised than spread of solution determined by x-ray evidence and that higher levels of analgesia are achieved in patients in the head-up position. Possible causes are the differing distribution characteristics of the constituents of the solution and the gravitational effects of posture on cerebrospinal fluid mechanics. Technical problems associated with obesity, congenital abnormalities, vascular uptake of solution, and delayed spread of the injectant due to adhesions are discussed.  相似文献   
87.
88.
Between 1 January and 31 March 1986, 2434 strains of Haemophilus influenzae collected from 23 laboratories in the United Kingdom were examined. With the same criteria as previous studies in 1977 and 1981 the prevalence of resistance was: ampicillin 7.8% (6.2% beta-lactamase producers and 1.6% non-producers), tetracycline 2.7%, chloramphenicol 1.7%, trimethoprim 4.2%, and sulphamethoxazole 3.5%. of the 87 capsulated strains, 15 produced beta-lactamase, nine were resistant to ampicillin but did not produce beta-lactamase, and two strains, one of which produced beta-lactamase, were resistant to chloramphenicol and tetracycline. Since 1977 the prevalence of resistance to ampicillin, chloramphenicol, and trimethoprim has increased significantly. During 1981-6 strains resistant to ampicillin but not producing beta-lactamase and strains resistant to trimethoprim have significantly increased.  相似文献   
89.
90.
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