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   16031篇
  免费   1387篇
  国内免费   31篇
耳鼻咽喉   145篇
儿科学   540篇
妇产科学   408篇
基础医学   2095篇
口腔科学   405篇
临床医学   1721篇
内科学   2913篇
皮肤病学   293篇
神经病学   1401篇
特种医学   683篇
外科学   2578篇
综合类   309篇
一般理论   18篇
预防医学   1394篇
眼科学   389篇
药学   1252篇
  3篇
中国医学   9篇
肿瘤学   893篇
  2021年   226篇
  2020年   142篇
  2019年   232篇
  2018年   257篇
  2017年   184篇
  2016年   223篇
  2015年   269篇
  2014年   377篇
  2013年   530篇
  2012年   752篇
  2011年   831篇
  2010年   434篇
  2009年   415篇
  2008年   675篇
  2007年   678篇
  2006年   692篇
  2005年   595篇
  2004年   586篇
  2003年   588篇
  2002年   479篇
  2001年   464篇
  2000年   506篇
  1999年   420篇
  1998年   212篇
  1997年   159篇
  1996年   193篇
  1995年   170篇
  1994年   138篇
  1993年   168篇
  1992年   393篇
  1991年   353篇
  1990年   375篇
  1989年   348篇
  1988年   345篇
  1987年   330篇
  1986年   317篇
  1985年   337篇
  1984年   261篇
  1983年   213篇
  1982年   161篇
  1981年   126篇
  1980年   124篇
  1979年   236篇
  1978年   171篇
  1977年   131篇
  1976年   123篇
  1975年   116篇
  1974年   119篇
  1973年   128篇
  1970年   115篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
The expression of ras oncogene in normal and pathological liver disease   总被引:1,自引:0,他引:1  
Activation of the ras oncogene is associated with overproduction of the normal gene product (p21). Ninety one paraffin-embedded specimens were used to map the distribution of the normal form of p21 in normal, inflamed, cirrhotic and carcinomatous liver parenchyma. Monoclonal antibodies (Mo-RAP) were raised against the normal form of the ras-oncogene product and histological sections were stained by the peroxidase-antiperoxidase technique. Normal, inflamed and cirrhotic liver showed either minimal or moderate cytoplasmic staining. By contrast primary (n = 13) and secondary (n = 41) liver carcinomas exhibited intense staining. The differential pattern observed in p21 distribution could have useful clinical applications.  相似文献   
12.
13.
Objectives: To determine interobserver agreement between radiologists for computed tomography (CT) angiography and venography. CT venography of the lower extremities combined with standard CT angiography of the chest may result in an increased overall diagnosis rate of venous thromboembolism (pulmonary embolism or deep venous thrombosis).
Methods: The study had a retrospective cohort design. The population consisted of emergency department patients who were evaluated for suspected pulmonary embolism. A random sample of 50 patients diagnosed and treated for venous thromboembolism and 50 age- and gender-matched patients whose CT angiograms and venograms were read as negative were enrolled. The original reading (R1) was compared with readings of two study radiologists: R2, a general radiologist, and R3, a radiologist with fellowship training in cross-sectional imaging. All readers were blinded to each other.
Results: Both R2 and R3 found both CT angiogram and venogram components technically adequate in 95% (95% CI = 89% to 98%) and 86% (95% CI = 78% to 92%) of studies, respectively. The agreement was very good for CT angiography (lowest agreement = 92%; lowest κ = 0.83) and was good for CT venography (85%, κ = 0.65). In nine cases, R1 read the CT angiogram as negative but the venogram as positive for DVT, whereas both R2 and R3 read both components as negative in four of these nine, suggesting a false-positive isolated DVT rate of 44% (95% CI = 19% to 73%). In no case did R1 read both scan components as negative when R2 and R3 agreed on presence of pulmonary embolism or DVT.
Conclusions: Diagnosis of pulmonary embolism on CT angiography is more reliable than diagnosis of isolated DVT on CT venography.  相似文献   
14.
15.
Development of anti-G suits and their limitations   总被引:1,自引:0,他引:1  
Initial anti-G suits were based on the belief that decreased venous return was the critical effect of increased weight of blood during acceleration. Cumbersome water filled, pneumatic gradient or pulsatile pressure suits resulted. Subsequent centrifuge studies implicated arterial pressure, rather than venous return, as the major determinant of G tolerance in the sitting position. Consequently, methods of increasing arterial pressure were developed. Findings that the hypertensive, associated anti-blackout and discomfort effects of suit inflation all increase with bladder system pressure up to arterial occlusive levels resulted in the simplified G-suit used in W.W.II to the present. Recent +Gz loss of consciousness crashes indicate current straining maneuvers plus this suit are inadequate. Furthermore, because of very high pressures to maintain cerebral circulation in the sitting position, very high G suit protection is hazardous. If piloting is essential for full use of super performance fighters, the prone position with counter-weighted head support plus omni-directional surveilance is the surest strategem to obtain this advantage.  相似文献   
16.
17.
18.
A morphological examination of synovial tissue from 25 patients with rheumatoid arthritis revealed that binucleated or multinucleated plasma cells were present in all samples and absent in synovia obtained from 16 control patients. Plasma cells containing two, three of four nuclei constitutet a mean 3% of the total plasma cell population. They were aways found amongst plasma cell infiltrates and in close association with small blood vessels. Ultrastructural analysis found no evidence of cellular membranes separating the individual nuclei in binucleated or multinucleated plasma cells, suggesting that the cells did not arise from fusion. Some of these plasma cells had a diameter approaching 100 μm, and many were in intimate contact with macrophages. The demonstration of a few cells with mitotic figures within the infiltrates suggests that the maintenance of plasma cell numbers in rheumatoid synovium may depend, in part, upon their local proliferation. Received: 25 August 1997 / Accepted: 2 October 1997  相似文献   
19.
20.
Long-term survival in an infant with urethral atresia   总被引:2,自引:0,他引:2  
Complete urethral atresia is an anomaly that previously was incompatible with life. We report on a surviving infant with this anomaly. As a fetus urinary decompression was accomplished with a vesicoamniotic shunt. Peritoneal dialysis was initiated shortly after birth and at 9 months supramembranous scrotal inlay urethroplasty was performed to provide for egress of urine from the bladder. A maternal renal allograft was performed when he was 12 months old. When the patient was 3 1/2 years old he had normal renal function and emptied the bladder to completion through the reconstructed urethra. Although mildly delayed, he continues to progress with all developmental milestones.  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