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   203887篇
  免费   18176篇
  国内免费   11528篇
耳鼻咽喉   1764篇
儿科学   2865篇
妇产科学   4025篇
基础医学   22502篇
口腔科学   4158篇
临床医学   25568篇
内科学   31708篇
皮肤病学   2377篇
神经病学   10442篇
特种医学   6865篇
外国民族医学   69篇
外科学   20545篇
综合类   31638篇
现状与发展   33篇
一般理论   30篇
预防医学   14615篇
眼科学   5417篇
药学   21502篇
  192篇
中国医学   10709篇
肿瘤学   16567篇
  2024年   657篇
  2023年   2891篇
  2022年   6935篇
  2021年   9212篇
  2020年   6880篇
  2019年   6114篇
  2018年   6493篇
  2017年   6014篇
  2016年   5478篇
  2015年   8539篇
  2014年   10724篇
  2013年   10724篇
  2012年   15808篇
  2011年   16885篇
  2010年   11376篇
  2009年   9204篇
  2008年   11908篇
  2007年   11713篇
  2006年   10941篇
  2005年   10264篇
  2004年   7449篇
  2003年   6749篇
  2002年   5761篇
  2001年   4818篇
  2000年   4656篇
  1999年   4542篇
  1998年   2522篇
  1997年   2415篇
  1996年   1936篇
  1995年   1867篇
  1994年   1625篇
  1993年   970篇
  1992年   1420篇
  1991年   1295篇
  1990年   1091篇
  1989年   934篇
  1988年   821篇
  1987年   748篇
  1986年   582篇
  1985年   464篇
  1984年   304篇
  1983年   249篇
  1982年   155篇
  1981年   139篇
  1980年   100篇
  1979年   183篇
  1978年   129篇
  1977年   97篇
  1974年   111篇
  1972年   102篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
Mice deficient for the fifth component of murine complement (C5), unlike normal mice, do not possess the secreted form of C5 in their body fluids and can be readily immunized to serum-derived normal C5. Although macrophages from C5-deficient mice do not secrete C5, they synthesize the precursor form (pro-C5). Therefore contact of T cells with autologous pro-C5 presented by macrophages is theoretically possible. We show that macrophages from C5-deficient mice can indeed stimulate a class II restricted C5-specific T cell clone without addition of exogenous C5. Immunization of C5-deficient mice with autologous pro-C5 induces vigorous C5-specific T cell proliferation and pro-C5 is recognized by C5-specific T cells in vitro, demonstrating that this protein fails to induce tolerance under physiological conditions. Thus, intracellular pro-C5 is processed and presented by C5-deficient macrophages and can activate T cell clones in vitro, yet is neither immunogenic nor tolerogenic for T cells in vivo.  相似文献   
64.
Experimental study on the immunosuppressive effects of gui zhi tang   总被引:1,自引:0,他引:1  
X F Lu 《中西医结合杂志》1989,9(5):283-5, 262
In this paper the immunosuppressive effects of Gui Zhi Tang (a famous Chinese medicine) on the murine immune functions are reported. Varying dosages of Gui Zhi Tang administrated orally, i.p. and i.m. were able to inhibit the amounts of PFC, SRFC and the DTH response induced by BSA and the proliferation response of murine spleen cells to Con A and LPS. Further studies showed that Gui Zhi Tang had the inhibitory effect on Interleukin-2 production of murine spleen cells, which might be one of the mechanisms leading to the immunosuppressive effects of Gui Zhi Tang.  相似文献   
65.
目的:研究成釉细胞瘤(AB)和牙源性角化囊肿(OKC)中c-mycmRNA的表达,探讨c-myc在AB和OKC中的发生、发展及其生物学意义。方法:使用原位杂交法检测54例AB、16例OKC和7例口腔正常黏膜(NOM)组织中c-mycmRNA的表达,并将AB按原发、复发、恶变分组,结果使用χ2检验进行统计分析。结果:AB、OKC及NOM组织中c-mycmRNA的阳性表达率分别为81.5%(44/54)、75.0%(12/16)和14.3%(1/7),3组比较有显著性差异(χ2=15.488,P<0.05)。原发组AB中c-mycmRNA的阳性表达率为71.0%,复发组为94.7%,恶变组为100.0%,伴随原发、复发、恶变,差异有显著性(χ2=16.912,P﹤0.05)。结论:c-myc表达在AB的发生、发展中有重要作用;c-mycmRNA的表达与AB的临床生物学行为有关,伴随其生物学行为变化,c-mycmRNA表达增强;提示c-myc有可能成为评价预后的有效指标。  相似文献   
66.
BACKGROUND: High rates of morbidity and mortality are observed in patients with advanced heart failure (AHF). AHF is now considered the most costly syndrome in cardiology owing to the substantial economic burden associated with hospitalizations for acute decompensation. A management program that involves specialized follow-up by a multidisciplinary team has been suggested as a desirable strategy for improving outcomes for these patients. ObjectivE: To evaluate the impact of a specialized outpatient heart failure (HF) follow-up program for patients with AHF on frequency and duration of hospitalization for HF and functional status. METHODS: We retrospectively studied 167 consecutive patients with AHF who were referred to the outpatient HF follow-up program in our institution between January and November 2002, of whom 147 followed for > or =30 days were included in the analysis. In addition to demographic and baseline clinical characteristics, HF medication and NYHA functional class, the number and duration of hospitalizations for HF during the previous 12 months were recorded and compared at the time of referral and after a follow-up period of 6.5+/-3 months. RESULTS: Of the 147 patients analyzed (aged 60.8+/-13 years; 79% male; left ventricular ejection fraction 27+/-11%), 67% were in NYHA functional class III, 20% in class II and 13% in class IV at the time of referral. There was a significant improvement in functional class during the mean follow-up period: 55% of the patients were in class III, 37% in class II, 5% in class I and 3% in class IV (p<0.0001). The proportion of patients on beta-blockers or spironolactone increased from 33% and 51% at the time of referral to 69% and 71% respectively after referral (p<0.0001). In the 12 months before referral, 39% of the patients had been hospitalized for acute decompensation of HF (87 hospitalizations - mean 7.2/month) versus 13% of the patients during the mean follow-up period (25 hospitalizations - 3.8/month, p<0.0001). No significant differences were found in the proportion of patients on angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers, digoxin or diuretics, or in the mean duration of hospitalization before and after referral. ConclusioN: The specialized follow-up of patients with AHF by a team with expertise in HF resulted in significant therapeutic optimization. Increased use of beta-blockers and spironolactone was associated with significant improvement in functional capacity and significant reduction in hospitalizations.  相似文献   
67.
Apical ballooning is a novel clinical entity reported in different contexts of physical and psychological stress, which is more common in middle-aged women. Of unknown etiology, the syndrome is characterized by a sudden and transient dilatation of the left ventricular apex in the absence of obstructive atherosclerotic coronary disease or evidence of myocardial necrosis, with total late recovery of ventricular function. The authors report the case of a 53-year-old woman who was admitted to the emergency room with left arm ischemia and low cardiac output, requiring ventilatory support. Left catheterization showed typical medial and apical myocardial dysfunction, with normal coronary arteries. Transesophageal echocardiography revealed a thrombus attached to the lower face of the aortic arch, which probably explained the thromboembolism of the arm but was unlikely to be the cause of the left ventricular dysfunction since there were no enzymatic or electrocardiographic signs of myocardial necrosis and normal wall motion was fully recovered.  相似文献   
68.
The relationship of large and vascularized chorioangiomas to adverse pregnancy outcome is well recognized. We present a patient with a large placental tumor and signs of impending fetal cardiac failure. The angioarchitecture of the tumor depicted by three-dimensional (3D) power Doppler ultrasound enabled us to accurately diagnose a placental chorioangioma. During the follow-up period, quantitative flow data obtained using 3D power Doppler indicated altered hemodynamics in the tumor and concomitant improvement in the condition of the fetus, enabling us to manage the mother conservatively. Spontaneous delivery occurred at 38 weeks without any complications. This report demonstrates the potential value of 3D power Doppler in prenatal diagnosis and monitoring of pregnancies complicated by large, vascularized chorioangioma.  相似文献   
69.
70.
BACKGROUND: Aerobic exercise training has been associated with beneficial effects on the cardiovascular system, improving arterial compliance, possibly related to a positive impact on the endothelium. The effects of competitive aerobic exercise are not so well documented. This prompted us to evaluate the possible modulation of arterial properties in a group of athletes and their response to the aging process. METHODS: 423 healthy males were enrolled in a cross-sectional study, 212 of whom were competitive athletes and 211 were controls. All underwent carotid-femoral pulse wave velocity (PWV) evaluation, and casual blood pressure and other relevant anthropometric data were evaluated. RESULTS: To control the effects of age, each group was divided into two subgroups with an age cut-point of 20 years. PWV was 6.3 +/- 0.9 m/s (athletes) vs. 7.0 +/- 1.0 m/s (controls) for ages <20 years, and 7.6 +/- 1.2 m/s (athletes) vs. 8.1 +/- 0.9 m/s (controls) for ages >20 years, with statistically significant differences in both comparisons. A linear regression model with logarithmic tendency analysis with age as the independent determinant of PWV revealed a different progression of age-related deterioration of aortic compliance between the two groups (athletes and controls). CONCLUSIONS: Our data documented better compliance indices in competition athletes compared with controls, which may reflect optimization of endothelial function. This improvement was age-dependent, being less pronounced as the athletes grow older, which could be due partially to sustained stretching effects on the arterial walls in long-term competitors.  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