收费全文 | 375643篇 |
免费 | 43590篇 |
国内免费 | 3211篇 |
耳鼻咽喉 | 7242篇 |
儿科学 | 11065篇 |
妇产科学 | 6658篇 |
基础医学 | 32045篇 |
口腔科学 | 5711篇 |
临床医学 | 49038篇 |
内科学 | 93376篇 |
皮肤病学 | 10427篇 |
神经病学 | 37317篇 |
特种医学 | 15938篇 |
外国民族医学 | 13篇 |
外科学 | 75348篇 |
综合类 | 2753篇 |
现状与发展 | 73篇 |
一般理论 | 177篇 |
预防医学 | 23108篇 |
眼科学 | 8651篇 |
药学 | 16273篇 |
1篇 | |
中国医学 | 325篇 |
肿瘤学 | 26905篇 |
2024年 | 785篇 |
2023年 | 5806篇 |
2022年 | 3275篇 |
2021年 | 8137篇 |
2020年 | 8642篇 |
2019年 | 7000篇 |
2018年 | 12927篇 |
2017年 | 11269篇 |
2016年 | 12655篇 |
2015年 | 13521篇 |
2014年 | 22833篇 |
2013年 | 25813篇 |
2012年 | 22238篇 |
2011年 | 23010篇 |
2010年 | 19710篇 |
2009年 | 22584篇 |
2008年 | 21195篇 |
2007年 | 20299篇 |
2006年 | 22184篇 |
2005年 | 19472篇 |
2004年 | 17788篇 |
2003年 | 15559篇 |
2002年 | 15063篇 |
2001年 | 5493篇 |
2000年 | 4244篇 |
1999年 | 5028篇 |
1998年 | 6202篇 |
1997年 | 5484篇 |
1996年 | 5079篇 |
1995年 | 4789篇 |
1994年 | 3348篇 |
1993年 | 2963篇 |
1992年 | 2275篇 |
1991年 | 2252篇 |
1990年 | 1792篇 |
1989年 | 1861篇 |
1988年 | 1641篇 |
1987年 | 1421篇 |
1986年 | 1479篇 |
1985年 | 1353篇 |
1984年 | 1421篇 |
1983年 | 1277篇 |
1982年 | 1521篇 |
1981年 | 1347篇 |
1980年 | 1178篇 |
1979年 | 752篇 |
1978年 | 832篇 |
1977年 | 825篇 |
1976年 | 638篇 |
1975年 | 583篇 |
Methods: Infant, adolescent, and adult rats were evaluated for proprioceptive, thermal, and mechanical nociceptive and motor function before and after sciatic blockade using a detailed neurologic examination.
Results: Mechanical and thermal nociception were present in all rats, starting from age 1 day. The withdrawal reflex latency to pinch was rapid at all ages, whereas that reaction to thermal stimulus depended on both age and temperature. In contrast, the tactile placing response and hopping response were absent at birth and developed completely during the first 10 days of life. The extensor postural thrust was absent in the first 2 weeks of life and developed variably during the first 50 days of life. Sciatic blockade duration is shorter in infant rats than in adult rats receiving the same dose per kilogram. A brief halothane general anesthetic at the time of sciatic injection in infant or adult rats does not alter the duration of blockade. 相似文献
Methods: Rats were anesthetized with halothane or sevoflurane in 100% oxygen and the lungs were mechanically ventilated. Leukocyte behavior in mesenteric venules was recorded through intravital video microscopy under monitoring microvascular hemodynamics. To examine the mechanisms for leukocyte rolling and adhesion, these studies were repeated after animals were pretreated with a monoclonal antibody against P-selectin (MAb PB1.3) or against intracellular adhesion molecule-1 (ICAM-1; MAb 1A29): P-selectin required for rolling of circulating leukocytes and ICAM-1 for firm adhesive interactions with leukocyte integrins.
Results: Under baseline anesthetic conditions (1 minimum alveolar concentration [MAC]), venular wall shear rates, an index of the disperse force on marginating leukocytes, in the sevoflurane-treated rats were about two times higher than those with halothane. At 2 MAC, halothane caused a marked arteriolar constriction and decreasing shear rates concurrent with an increasing density of venular leukocyte adhesion. Sevoflurane at 2 MAC induced leukocyte rolling and adhesion, which were attenuated by PB1.3 and 1A29, without alterations in the wall shear rates. Halothane-induced leukocyte adhesion was not prevented by PB1.3 but it was by 1A29. 相似文献
Methods: In 25 children studied with carotid artery Doppler, embolic signals were counted and timed in relation to 13 intraoperative events. Patients were classified as either at high risk (obligate right-to-left shunt or uncorrected transposition of the great arteries) or at low risk (net left-to-right shunt or simple obstructive lesions) for paradoxical (venous to arterial) emboli.
Results: The median number of emboli detected was 122 (range, 2-2,664). Forty-two percent of all emboli were detected within 3 min of release of the aortic crossclamp. The high-risk group had significantly more emboli (median, 66; range, 0-116) during the time interval before cardiopulmonary bypass than did the low-risk group (median, 8; range, 0-73), with P < 0.01. There was no significant difference between the high-and low-risk groups in the total number of emboli detected. There was no apparent association between number of emboli and gross neurologic deficits. 相似文献
Design: Prospective, randomized study.
Setting: Teaching hospital.
Patients: 600 ASA physical status I and II parturients scheduled for labor and delivery or elective cesarean section.
Interventions: After identification of the epidural space with pulsations of an air-fluid column, parturients for vaginal delivery (n = 380) were randomized to receive a test dose of 3 ml 3% 2-chloroprocaine with epinephrine 20 μg, two doses of 7 ml bupivacaine 0.03 % with sufentanil 1 μg/ml and epinephrine 2 μg/ml by either gravity flow (Group 1) given over 30 seconds or by bolus injection (Group 2) given over 5 seconds through the epidural needle; parturients for Cesarean delivery (n = 220) were randomized to receive a test dose and two doses of 6 ml lidocaine 2 % with sufentanil 1 μg/ml and epinephrine 2 μg/ml by either gravity flow or by bolus injection through the epidural needle. Changes in maternal heart rate (HR) and blood pressure, signs of intravascular injection, and adverse effects of epidural bupivacaine-sufentanil were recorded after each dose.
Measurements and Main Results: Gravity flow administration (Group 1) was associated with a smaller increase in mean maternal HR (p < 0.001), less hypotension (p < 0.01), sedation (p < 0.01), nausea (p = 0.01), and segmental spread (p < 0.0001) than were corresponding doses given by traditional bolus injection (Group 1) for vaginal or Cesarean deliveries. The incidence of systemic toxicity was zero of 300 (0%) with gravity flow and 4 of 300 (1.3%) by bolus injection, p = 0.12, Fisher's exact test. No patient in either group had an accidental intrathecal injection.
Conclusion: Gravity flow administration of local anesthetic-opioid solution during epidural block for obstetrics was associated with fewer signs of systemic drug absorption and cardiovascular perturbations than was the traditional bolus injection. This study supports the current opinion that slow administration of local anesthetic during epidural black contributes to fewer adverse events. 相似文献