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   2059篇
  免费   58篇
  国内免费   14篇
耳鼻咽喉   11篇
儿科学   17篇
妇产科学   108篇
基础医学   328篇
口腔科学   15篇
临床医学   128篇
内科学   294篇
皮肤病学   12篇
神经病学   233篇
特种医学   46篇
外科学   177篇
综合类   4篇
预防医学   397篇
眼科学   53篇
药学   202篇
中国医学   4篇
肿瘤学   102篇
  2023年   4篇
  2022年   11篇
  2021年   15篇
  2020年   16篇
  2019年   24篇
  2018年   37篇
  2017年   26篇
  2016年   34篇
  2015年   35篇
  2014年   56篇
  2013年   71篇
  2012年   149篇
  2011年   165篇
  2010年   56篇
  2009年   58篇
  2008年   145篇
  2007年   185篇
  2006年   181篇
  2005年   205篇
  2004年   158篇
  2003年   145篇
  2002年   152篇
  2001年   5篇
  2000年   10篇
  1999年   4篇
  1998年   5篇
  1997年   5篇
  1996年   4篇
  1995年   5篇
  1991年   5篇
  1979年   4篇
  1978年   6篇
  1977年   4篇
  1976年   7篇
  1975年   6篇
  1973年   5篇
  1971年   5篇
  1970年   8篇
  1969年   11篇
  1966年   6篇
  1965年   4篇
  1942年   3篇
  1938年   4篇
  1937年   5篇
  1936年   3篇
  1935年   3篇
  1934年   5篇
  1933年   3篇
  1926年   5篇
  1924年   3篇
排序方式: 共有2131条查询结果,搜索用时 15 毫秒
51.
We describe a 49-year-old female patient who was diagnosed with breast cancer in her left breast. The patient underwent a modified radical mastectomy and immediate reconstruction with the placement of an expander implant. Two years later, the patient suffered a minor trauma and began to feel the softening of her reconstructed breast, and a growing palpable mass appeared in the contralateral (right) axilla. Examinations revealed the intracapsular rupture of the expander implant. Aspiration cytology from the palpable axillary mass suggested silicone lymphadenopathy. We replaced the ruptured implant, and the lymph node from the contralateral axilla was removed. Silicone lymphadenomegaly in the right axilla was verified by a postoperative histopathological review. This case represents a rare manifestation of silicone lymphadenopathy caused by altered lymphatic drainage due to previous axillary lymphadenectomy. Level of Evidence: Level V, diagnostic study.  相似文献   
52.
Inclusion body myositis is a slowly progressive myopathy affecting predominantly the middle-aged and older patient population. It is a major form of the idiopathic inflammatory myopathies which are chronic systemic autoimmune diseases characterized by symmetrical proximal muscle weakness. Unfortunately, there is no effective therapy yet; however, the early diagnosis is essential to provide treatment options which may significantly slow the progression of the disease. In our case-based clinicopathological study the importance of the close collaboration between the clinician and the neuropathologist is emphasised.  相似文献   
53.

Aim

To assess how ovarian-derived sex hormones (in particular progesterone) modify the effects of single acute stress on the mechanical and biochemical properties of left ventricular cardiomyocytes in the rat.

Methods

Non-ovariectomized (control, n = 8) and ovariectomized (OVX, n = 8) female rats were kept under normal conditions or were exposed to stress (control-S, n = 8 and OVX-S, n = 8). Serum progesterone levels were measured using a chemiluminescent immunoassay. Left ventricular myocardial samples were used for isometric force measurements and protein analysis. Ca2+-dependent active force (Factive), Ca2+-independent passive force (Fpassive), and Ca2+-sensitivity of force production were determined in single, mechanically isolated, permeabilized cardiomyocytes. Stress- and ovariectomy-induced alterations in myofilament proteins (myosin-binding protein C [MyBP-C], troponin I [TnI], and titin) were analyzed by sodium dodecyl sulfate gel electrophoresis using protein and phosphoprotein stainings.

Results

Serum progesterone levels were significantly increased in stressed rats (control-S, 35.6 ± 4.8 ng/mL and OVX-S, 21.9 ± 4.0 ng/mL) compared to control (10 ± 2.9 ng/mL) and OVX (2.8 ± 0.5 ng/mL) groups. Factive was higher in the OVX groups (OVX, 25.9 ± 3.4 kN/m2 and OVX-S, 26.3 ± 3.0 kN/m2) than in control groups (control, 16.4 ± 1.2 kN/m2 and control-S, 14.4 ± 0.9 kN/m2). Regarding the potential molecular mechanisms, Factive correlated with MyBP-C phosphorylation, while myofilament Ca2+-sensitivity inversely correlated with serum progesterone levels when the mean values were plotted for all animal groups. Fpassive was unaffected by any treatment.Conclusion Stress increases ovary-independent synthesis and release of progesterone, which may regulate Ca2+-sensitivity of force production in left ventricular cardiomyocytes. Stress and female hormones differently alter Ca2+-dependent cardiomyocyte contractile force production, which may have pathophysiological importance during stress conditions affecting postmenopausal women.The relation between stress, gender, and cardiovascular diseases is well established (1-4). Some of the known risk factors for cardiovascular disease such as smoking, unhealthy diet, and behavioral and psychosocial stress have deleterious effects on the cardiovascular system via activation of the sympathetic nervous system and the hypothalamic-pituitary-adrenal (HPA) axis (5-8). Acute restraint stress is a preferred and widely used method to induce physical stress in animal models (9). Moreover, restraint and immobilization are important as models for psychological stress, which was shown to adversely affect ovarian function (10) and to play a pivotal role in the pathomechmanism of Takotsubo (stress) cardiomyopathy in postmenopausal women (11).Gender is a very important factor in the development of cardiovascular diseases. Premenopausal women have better lipid profile, endothelial function (12), and a lower risk to develop coronary artery disease and myocardial infarction (MI) than men. These advantages of female gender, however, are abolished after menopause, which is associated with increased prevalence of left ventricular (LV) hypertrophy, decreased LV ejection fraction, and LV contractility (13). One of the explanations for the distinct myocardial responses is the cardioprotective effect of female sex hormones (eg, estrogens) (14,15).Progesterone performs several actions on the heart: it exerts an antiarrhythmic effect by accelerating cardiac repolarization (16) and has a preventive role in ischemia-reperfusion injury via reducing inflammatory response (17). It has been shown to inhibit cardiomyocyte apoptosis (18), induce vasodilation, and reduce blood pressure via increasing nitric oxide (NO) levels in normotensive and hypertensive patients (19). Importantly, progesterone is produced by the both ovaries and the adrenal gland: Moreover, the adrenal progesterone content is similar or even larger than that in the ovaries (20). Adrenal progesterone production and secretion increase along with corticosterone regardless of gender and estradiol under stress conditions (21). Progesterone, being an indirect precursor of cortisol (22), increases in response to adrenocorticotrophic hormone (ACTH) stimulation (23).In the heart, there are multiple estrogen hormone receptor types (24). The expression of aromatase in the heart suggests that estrogen may be synthesized also within the cardiomyocyte to exert autocrine/paracrine actions (25). Myocyte contractility seems to be modulated by systemic estrogen levels and altered in cardiomyocytes derived from ovariectomized (OVX) rats (26). In particular, myofilament Ca2+-sensitivity is increased in isolated myofibrillar preparations from OVX rats, and restored to the basal levels with estrogen supplementation (27,28).Activation of the sympathetic nervous system plays a central role in the regulation of cardiomyocyte contractile function and myofilament Ca2+-sensitivity through beta-adrenergic receptor stimulation, activating the protein kinase A (PKA). PKA-mediated phosphorylation of Ca2+-handling and myofilament proteins (myosin binding protein-C [MyBP-C], troponin I [TnI], titin) were shown to alter cardiomyocyte contractile function (29,30). It has been suggested that female cardiomyocytes operate at lower levels of intracellular Ca2+ than those of males, particularly under inotropic conditions (31). This difference in Ca2+ homeostasis may be related to the fact that estrogen suppresses the L-type Ca2+ current (32,33) and may reduce the amount of Ca2+ released from the sarcoplasmic reticulum (SR) (34), which was shown to be larger in myocytes from OVX rats (35). Not only cardiomyocyte contraction, but relaxation may also be affected by estrogen via altered Ca2+ re-uptake into the SR and modified Ca2+ efflux via increased sarcolemmal Na+/Ca2+ exchange (36). Interestingly, despite similar SR Ca2+ content in males and females (37), studies using OVX models report conflicting results concerning changes in the expression and activity of the SR Ca2+-ATPase and its regulator protein phospholamban (38-41). Much less is known about the possible effect of progesterone on cardiomyocyte contractile function. We hypothesized that progesterone affected force production of single isolated cardiomyocytes. Therefore, in the present study we aimed to investigate how sex hormones (particularly progesterone) and single acute restraint stress altered cardiomyocyte contractile function and to identify the consequent posttranslational myofilament protein modifications in OVX rats.  相似文献   
54.
OBJECTIVE: Review of cases of perinatally diagnosed congenital diaphragmatic hernias with special regard to time of diagnosis, organs herniated into the thorax, associated malformations, and outcomes. METHODS: We analyzed the data of 106 cases between July 1, 1990, and June 30, 2005. The observation period was analyzed in two parts. RESULTS: Prenatal ultrasound was performed in 89.6% (95/106) of the cases. 51.7% (46/89) of the pre- and postnatally verified congenital diaphragmatic hernia cases were diagnosed before the 24th week of gestation. 11% (11/100) of the hernias were identified postnatally. 71% (71/100) of the cases were associated with other malformations. The hernia was on the left side in 86% (86/100) and bilateral in 5% (5/100) of the cases. Between 1990 and 1997, the proportion of right-sided hernias was 4.3% (2/46), while during the second period it was 13% (7/54). 27.5% (14/51) of the newborns survived the perinatal period. The survival rate of the newborns delivered by caesarean section was three times higher than that of infants delivered vaginally. In the latter group, the rate of premature deliveries was considerably higher. The pregnancy was terminated in 45% (40/89) of the cases. 15% (6/40) of the terminated cases were isolated. Intrauterine or intrapartum deaths occurred in 5.6% (5/89) of the prenatally diagnosed cases. Simultaneous thoracic herniation of liver, spleen, or stomach decreased the survival rate. In these cases, the discharge rate was between 6 and 22%. CONCLUSIONS: According to the analysis of 15-year data, the herniated organs, multiple malformations, as well as the mode of delivery influence the survival in a large number of cases. Early diagnosis predicts a large hernia, a higher malformation rate, and a less favourable prognosis.  相似文献   
55.
Joó JG  Beke A  Papp Z  Csaba A  Rab A  Papp C 《Prenatal diagnosis》2007,27(11):1028-1032
OBJECTIVE: The goal of the current publication is to review isolated central nervous system malformations (CSMs) using a database in excess of 75 000 cases, with special regard to the risk of recurrence of these malformations alone or in combination. METHODS: In the period between 1 January 1976 and 31 December 2005, among the 75 320 documented cases, consultations were requested due to earlier isolated CSMs in the patients' histories in 3030 cases (4.2%). Processing the data we only considered disorders of genetic origin, and that was why we excluded the cases due to intrauterine infection. Monogenically inherited malformations were also excluded from the analysis. The diagnosis of the malformations was based on the prenatal diagnosis of ultrasonography as well as the findings of the foetopathological examination. RESULTS: In 65% of the cases, the couples sought counselling because of malformation in a previous pregnancy. In these cases, the risk of recurrence was thought to be 5.2%, while in the case of two affected children this figure stood at 21.9%. Analysing the values for the risk of recurrence in 5-year periods, neural tube defects (NTDs) (particularly anencephaly and spina bifida) showed a detectable decrease, which could be attributed to a growing use of folic acid supplementation around the time of conception and during pregnancy. CONCLUSION: There is a clear decrease of risk of recurrence of NTDs, while in the case of the other CSMs in this study, there is no noteworthy chronological change in their risk of recurrence.  相似文献   
56.
57.
A large population of infracortical white matter neurons, or white matter interstitial cells (WMICs), are found within the subcortical white matter of the mammalian telencephalon. We examined WMICs in three species of megachiropterans, Megaloglossus woermanni, Casinycteris argynnis, and Rousettus aegyptiacus, using immunohistochemical and stereological techniques. Immunostaining for neuronal nuclear marker (NeuN) revealed substantial numbers of WMICs in each species—M. woermanni 124,496 WMICs, C. argynnis 138,458 WMICs, and the larger brained R. aegyptiacus having an estimated WMIC population of 360,503. To examine the range of inhibitory neurochemical types we used antibodies against parvalbumin, calbindin, calretinin, and neural nitric oxide synthase (nNOS). The calbindin and nNOS immunostained neurons were the most commonly observed, while those immunoreactive for calretinin and parvalbumin were sparse. The proportion of WMICs exhibiting inhibitory neurochemical profiles was ~26%, similar to that observed in previously studied primates. While for the most part the WMIC population in the megachiropterans studied was similar to that observed in other mammals, the one feature that differed was the high proportion of WMICs immunoreactive to calbindin, whereas in primates (macaque monkey, lar gibbon and human) the highest proportion of inhibitory WMICs contain calretinin. Interestingly, there appears to be an allometric scaling of WMIC numbers with brain mass. Further quantitative comparative work across more mammalian species will reveal the developmental and evolutionary trends associated with this infrequently studied neuronal population.  相似文献   
58.
59.
60.
PURPOSE: To correlate prenatal sonographic diagnosis of cystic lung malformations with fetopathologic findings after termination of pregnancy. METHODS: We retrospectively analyzed the data of 16 terminated cases in which a cystic lung lesion was diagnosed pre- or postnatally. RESULTS: On average, prenatal diagnosis was established on the 21(st) gestational week (range, 19-26 weeks). The cause of termination was severe polyhydramnios in 4 cases, nonimmune fetal hydrops in 4 cases, other congenital malformation in 5 cases (renal malformation, 2 cases; congenital diaphragmatic hernia, 3 cases), and obstetrical conditions (intrauterine death, placental abruption, spontaneous abortion) in 3 cases. In 11 cases, congenital cystic adenomatoid malformation (CCAM) was the presumptive prenatal diagnosis. Autopsy confirmed the prenatal diagnosis in 6 of them, while in the other 5 cases, an enteric cyst, a laryngeal atresia, an unidentified tumor, a pulmonary hypoplasia, and an extralobar pulmonary sequestration were found on histologic examination. On the other hand, the autopsy revealed CCAM in those 5 cases in which other malformations were suggested prenatally. CONCLUSION: The prenatal sonographic diagnosis of CCAM is difficult. Our cases emphasize the important role of fetopathology even today in the verification of prenatal diagnosis based on sonographic examinations.  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