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   36567篇
  免费   1430篇
  国内免费   147篇
耳鼻咽喉   502篇
儿科学   679篇
妇产科学   433篇
基础医学   4493篇
口腔科学   1178篇
临床医学   2527篇
内科学   8113篇
皮肤病学   780篇
神经病学   3493篇
特种医学   1845篇
外国民族医学   1篇
外科学   5547篇
综合类   136篇
一般理论   6篇
预防医学   1138篇
眼科学   768篇
药学   2404篇
  4篇
中国医学   73篇
肿瘤学   4024篇
  2023年   232篇
  2022年   350篇
  2021年   646篇
  2020年   425篇
  2019年   531篇
  2018年   606篇
  2017年   490篇
  2016年   621篇
  2015年   601篇
  2014年   786篇
  2013年   960篇
  2012年   1616篇
  2011年   1630篇
  2010年   983篇
  2009年   837篇
  2008年   1465篇
  2007年   1711篇
  2006年   1560篇
  2005年   1514篇
  2004年   1525篇
  2003年   1446篇
  2002年   1471篇
  2001年   1313篇
  2000年   1422篇
  1999年   1280篇
  1998年   473篇
  1997年   384篇
  1996年   362篇
  1995年   304篇
  1994年   304篇
  1993年   286篇
  1992年   993篇
  1991年   851篇
  1990年   818篇
  1989年   808篇
  1988年   764篇
  1987年   757篇
  1986年   668篇
  1985年   622篇
  1984年   425篇
  1983年   345篇
  1979年   297篇
  1978年   200篇
  1977年   177篇
  1974年   188篇
  1973年   162篇
  1972年   161篇
  1971年   181篇
  1970年   155篇
  1969年   178篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
101.
102.
103.
Surgical and autopsy specimens of normal pancreas from three human adults were submitted to morphometry of Langerhans islets and so-called extra insular islet cells, by measuring the islet radii on serial sections immunostained for either insulin or glucagon. All the islets contained in a test volume were measured including single cells, and the distribution of their radial sizes was studied. It was found that the distribution of islets was strongly skewed and continuous, with the majority of islets having radial values near to the minimum. From the fact that only one peak was found in the distribution curve, it is concluded that in spite of the distinction previously made between islets of Langerhans and so-called extra-islet cells, they are in fact both part of a continuous distribution. Moreover, the Weibull function, assumed as the theoretical distribution, fit well with the empirical histograms, giving support for the contention of continuous distribution with a single peak. Although the small islets account for a majority of the number of islets, they account for only a very small percentage of the islet volume. This is thought to indicate that the bulk of the endocrine functions of the pancreas are carried out by large islets, whereas the so-called extra-islet cells are likely to be their precursors. With regard to the cellular structure of the islets, it was found that the smaller the islet, the smaller the percentage of islets containing A cells, with the vast majority of cells in the smallest islets (often single cells) being B cells.  相似文献   
104.
105.
We examined whether differences in the location of myocardial hypertrophy influence the right ventricular diastolic function in patients with non-obstructive hypertrophic cardiomyopathy using cineangiography. Biplane right ventriculography was performed in 34 subjects (normal = 14, asymmetric septal hypertrophy = 9, apical hypertrophy = 11) during cardiac catheterization. In patients with asymmetric septal hypertrophy, compared with apical hypertrophy and normal groups, the indices of the right ventricular diastolic function including right ventricular peak filling rate and filling fraction of rapid filling phase were lower and the time to peak filling rate was prolonged. But in patients with apical hypertrophy, these indices were not significantly different compared with normal. There were no differences in right ventricular ejection fraction and cardiac index among the three groups. These data suggest that the location of the myocardial hypertrophy of the left ventricle is a significant factor affecting the right ventricular diastolic filling in non-obstructive hypertrophic cardiomyopathy.  相似文献   
106.
OBJECTIVES: The aim of this study was to investigate the effects of the menstrual cycle on QT interval dynamics and the autonomic tone in healthy women. METHODS: Holter ECGs were recorded in 11 healthy women aged 18-32 years during the follicular and luteal phases of their regular menstrual cycle. The interval from QRS onset to the apex (QaT) and to the end of the T-wave (QeT), the interval between the apex and the end of the T-wave (Ta-e), and RR intervals were measured automatically in the course of 24 hours by Holter ECGs. The QeT/RR, QaT/RR, and Ta-e/RR relationships were evaluated in each subject. The autonomic tone was assessed by the serum catecholamine level at rest and heart rate variability was measured by Holter ECGs. RESULTS: (1) The follicular and luteal phases did not differ significantly with respect to the slopes of the QeT/RR, QaT/RR, and Ta-e/RR relationships. However, QeT and QaT intervals were significantly shorter for all RR intervals in the luteal than in the follicular phase (P < 0.0001). (2) The serum progesterone concentration was significantly higher in the luteal than in the follicular phase (P < 0.001). (3) Noradrenaline was significantly higher in the luteal than in the follicular phase (P < 0.05). There was no significant difference in the follicular and luteal phases with respect to heart rate variability measurements. CONCLUSIONS: Our results suggest that the menstrual cycle affects the QT intervals. The observed shorter QT interval during the luteal than the follicular phase may be attributable to the increase in serum progesterone and sympathetic tone.  相似文献   
107.
OBJECTIVE: Anesthesia and surgery decrease antimicrobial and increase proinflammatory functions of alveolar immune cells. Thus, anti-inflammatory agents that do not further suppress antimicrobial functions are required. We tested the hypothesis that intraoperative prostaglandin E1 (PGE1) suppresses proinflammatory responses and prevents the reduction in antimicrobial responses of alveolar immune cells. DESIGN: Prospective, randomized, controlled, double-blind study. SETTING: University hospital. PATIENTS: A total of 40 patients undergoing elective orthopedic surgery under propofol/fentanyl anesthesia. INTERVENTION: In double-blind fashion, the patients received PGE1 from the beginning to the end of surgery (PGE1 group, n = 20) or nothing (control group, n = 20). METHODS AND MAIN RESULTS: Alveolar immune cells were harvested by bronchoalveolar lavage immediately after induction of anesthesia; 2, 4, and 6 hrs after induction of anesthesia; and at the end of surgery. We measured opsonized and nonopsonized phagocytosis. Microbicidal activity was evaluated to directly kill Listeria monocytogenes in alveolar macrophages. Finally, we determined the expression of proinflammatory cytokines including interleukin (IL)-1beta, IL-8, interferon-gamma, and tumor necrosis factor-alpha, and that of anti-inflammatory cytokines (IL-4 and IL-10) by semiquantitative polymerase chain reaction. Nonopsonized and opsonized phagocytosis and microbicidal activity of alveolar macrophages decreased and the expression of genes for all pro- and anti-inflammatory cytokines increased significantly over time in both groups. Starting 2-4 hrs after induction of anesthesia, the increases in gene expression of proinflammatory cytokines were 1.5-3 times smaller in the PGE1 than in the control group. Starting 6 hrs after anesthesia, the increase in gene expression of IL-10 was 1.5-3 times greater in the PGE1 than in the control group. Intraoperative decreases in phagocytic and microbial activities were the same in the two groups. CONCLUSION: Intraoperative PGE1 not only suppressed proinflammatory responses, but also protected antimicrobial functions of alveolar macrophages, possibly because PGE1 is mostly inactivated in the pulmonary intravascular space. Our results suggest that intraoperative PGE1 protects the pulmonary immune defense in alveolar immune cells.  相似文献   
108.
109.
Tryptophan column immunoabsorption therapy is beneficial to the patient with a neuroimmunological disease, but some complications have been attributed to this treatment. There have been some instances of an abrupt shock state along with severe decreases in blood pressure. In regards to this shock state, it has been reported that plasma bradykinin levels increase during tryptophan column immunoabsorption therapy. In this study, we examined the correlation between plasma bradykinin levels and either blood pressure or the levels of its degrading enzymes, angiotensin converting enzyme (ACE) and carboxypeptidase R (CPR) in 6 patients. Increased concentrations of bradykinin were present in the latter half of the therapeutic interval, and plasma bradykinin levels were found to be inversely correlated to CPR activity. The decreased CPR level could augment the activities of bradykinin. We speculate that bradykinin could be responsible for the hypotension occurring in patients during tryptophan column immunoabsorption therapy and that the metabolism of bradykinin could be caused by the decreased activity of CPR.  相似文献   
110.

Background/Purpose

Intracranial hemorrhage (ICH) is a severe complication of biliary atresia (BA). We aimed to compare the clinical data of BA patients with and without ICH.

Methods

Sixty-three BA patients who underwent Kasai portoenterostomy were included in this study. We retrospectively reviewed their clinical records, and compared the ICH and non-ICH groups.

Results

ICH occurred in seven patients (11.1%). The patients with ICH were significantly older at the time of Kasai portoenterostomy (median age: 90.0 vs 65.5?days). The hepatobiliary enzyme levels of the patients with ICH were significantly lower in comparison to the patients without ICH (T-Bil 6.7 vs 9.8?mg/dl; AST 95 vs 194?U/L; ALT 44 vs 114?U/L). On the other hand, the coagulation test values of the patients with ICH were significantly higher in comparison to the patients without ICH (PT 50.0 vs 12.4?s; APTT 200.0 vs 36.9?s). Although the survival rates did not differ to a statistically significant extent, persistent neurological sequelae occurred in two patients in the ICH group.

Conclusions

The hepatobiliary enzyme levels of the patients with ICH were significantly lower than those without ICH. However, coagulopathy was found to be significantly more progressive in patients with ICH.

Levels of Evidence

Level III.  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