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   16212篇
  免费   1473篇
  国内免费   944篇
耳鼻咽喉   148篇
儿科学   161篇
妇产科学   283篇
基础医学   2010篇
口腔科学   266篇
临床医学   2151篇
内科学   2636篇
皮肤病学   184篇
神经病学   842篇
特种医学   564篇
外国民族医学   5篇
外科学   1919篇
综合类   2136篇
现状与发展   1篇
一般理论   6篇
预防医学   1078篇
眼科学   485篇
药学   1653篇
  15篇
中国医学   743篇
肿瘤学   1343篇
  2024年   46篇
  2023年   246篇
  2022年   579篇
  2021年   797篇
  2020年   555篇
  2019年   552篇
  2018年   558篇
  2017年   503篇
  2016年   490篇
  2015年   714篇
  2014年   870篇
  2013年   818篇
  2012年   1164篇
  2011年   1173篇
  2010年   848篇
  2009年   664篇
  2008年   781篇
  2007年   798篇
  2006年   824篇
  2005年   767篇
  2004年   637篇
  2003年   614篇
  2002年   568篇
  2001年   447篇
  2000年   386篇
  1999年   395篇
  1998年   272篇
  1997年   240篇
  1996年   179篇
  1995年   181篇
  1994年   114篇
  1993年   97篇
  1992年   108篇
  1991年   93篇
  1990年   72篇
  1989年   69篇
  1988年   65篇
  1987年   62篇
  1986年   42篇
  1985年   42篇
  1984年   22篇
  1983年   14篇
  1981年   14篇
  1980年   12篇
  1979年   21篇
  1978年   11篇
  1974年   15篇
  1973年   13篇
  1972年   10篇
  1969年   11篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Metasul metal-on-metal articulations have been used for 15 years in approximately 300,000 total hip replacements. We have used Metasul articulations in three clinical studies and have shown clinical success as measured by Harris hip scores and patient self-assessment; we also have had the usual mechanical complications. The only complications have been mechanical, including two cup loosenings and 24 dislocations in a total of 582 patients (619 hips; 3.8%) who had Metasul articulations and were included in these studies. In the randomized study, the group who had Metasul articulations had no clinical results or complications different from the control ceramic-on-polyethylene group. Authors of retrieval results in the literature report low annual linear wear rates and no consequences of elevated Co ion levels. Currently, the scientific evidence of the results of using the Metasul articulation would recommend its continued use in any patient who does not have compromised renal function.  相似文献   
992.
There is a very limited published material about experience with long-term pediatric mechanical circulatory support as a bridge to heart transplant. We report on a 2-year-old, 12 kg boy admitted with 2-week history of low-grade fever, ear pain, pulmonary edema, and congestive heart failure. Trans-thoracic echocardiography confirmed severe myocardial dysfunction with a left ventricular ejection fraction of 0.20 and percentage shortening of 13. After 2 days of ventilatory and inotropic support, the patient continued to deteriorate and subsequently required femoro-femoral extracorporeal life support (ECLS). This was later complicated by a progressive coagulopathy and massive bleeding. On day 17, a pulsatile pediatric paracorporeal biventricular assist device (VAD) (Berlin Heart) was implanted. The patient's condition improved significantly with all coagulopathies corrected, and the patient was extubated 21 days later. After 109 days of bi-VAD support, the patient was successfully transplanted and discharged home 45 days post transplant. Our early experience with initial ECLS bridge to VAD and subsequently to transplant was encouraging. It allowed for additional time to select the ideal organ donor and optimize the recipient's comorbid condition and multiorgan failure. VAD provides an additional armamentarium of circulatory support in pediatric patients with severe heart failure.  相似文献   
993.
OBJECTIVE: Late saphenous vein graft failure after coronary artery bypass graft surgery is initiated by medial thickening and neointima formation, both of which are mediated by the proliferation of vascular smooth muscle cells. Because porcine vein grafts contain high levels of endothelin 1 receptor subtypes and endothelin 1 promotes the proliferation of vascular smooth muscle cells, the effect of administration of the endothelin 1(A) receptor antagonist BSF 302146 ([+]-[S]-2-[4,6-dimethyl-pyrimidin-2-yloxy]-3,3-diphenyl-butanoic acid) on porcine vein graft thickening was investigated. METHODS: Saphenous vein-carotid artery interposition grafting was performed in 4 groups of large white pigs (30-35 kg, n = 10 for each group). BSF 302146 was administered orally (3, 10, and 30 mg x kg(-1) x d(-1)) for 4 weeks to one group of pigs, and placebo was administered to the other group (control animals). Pigs were then anesthetized, and the grafts were removed and fixed at 100 mm Hg with 4% paraformaldehyde. Histologic sections were prepared, and graft morphometry was carried out by using computer-aided planimetry. RESULTS: In vein grafts from animals treated with BSF 302146 compared with grafts from control animals (untreated), there were significant dose-dependent reductions in the increase in medial thickness and neointimal thickness, an increase in luminal area, and a decrease in proliferating cell nuclear antigen-positive cells in the medial-intimal area. CONCLUSIONS: The administration of BSF 302146 reduces graft thickening and promotes positive remodeling through an endothelin 1(A)-mediated effect on vascular smooth muscle cell replication. The administration of this endothelin 1(A) receptor antagonist might therefore be therapeutically effective in preventing late vein graft failure in patients undergoing coronary artery bypass grafting.  相似文献   
994.
BACKGROUND: Continuous pulse oximeter monitoring (CPOM) and daily intermittent arterial blood gas (ABG) were used to define the incidence, pattern, and severity of inapparent hypoxemia after long bone fractures. METHOD: Twenty long bone fracture patients and 19 normal control patients were studied. CPOM, daily ABG, hypoxic symptoms, and features of fat embolism syndrome were monitored for 72 hours after fractures and after surgical interventions. RESULTS: CPOM trend curves showed that all fracture patients except one had recurrent desaturations below 90% Sao2 of varying duration and depth. The lowest Sao2 was down to 60% and the longest episode lasted for 1.47 hours. ABG analysis could not show the recurrent phenomena and never detected the corresponding desaturation episodes. Long bone fracture patients had more desaturation episodes, longer total desaturation duration, and larger total area under desaturation curves in both the postfracture and postoperative periods (p < 0.05). The mean Sao2 was significantly lower in the postfracture period. Although most patients remained asymptomatic and recovered spontaneously, two required transient oxygen therapy and one progressed to fat embolism syndrome. CONCLUSION: Inapparent hypoxia with profound desaturation is common after long bone fractures. CPOM of all patients admitted with long bone fractures is recommended for early detection. In patients who develop inapparent hypoxia, additional pulmonary insult should be avoided or undertaken with care and well timed.  相似文献   
995.
Introduction Adduction of the ipsilateral hip joint is necessary to facilitate closed hip nailing for trochanteric fracture. Even though positioning the patient supine with the perineal post against the ipsilateral medial thigh can change the course of the neurovascular structure in the proximal thigh, there have been no reports regarding the position of the femoral artery in the hip nailing position.Materials and methods We studied the position of the superficial femoral artery in 59 thighs using color-flow duplex scanning method in three hip nailing positions.Results The mean of the distance between the superficial femoral artery and the femur in 48 normal limbs was 20.28 mm in neutral position (D1), 11.85 mm in 20o adduction (D2), and 9.53 mm in 20o adduction plus 20o internal rotation of the foot plate (D3). The distances D2 and D3 were always shorter than D1 (p<0.001). D3 was less than 10 mm in 30 of the normal limbs (62.5%) and less than 5 mm in 4 (8%). In 11 patients who sustained a trochanteric fracture, the mean of D1, D2, and D3 in the injured limbs was 25.28 mm, 17.98 mm, and 14.38 mm, respectively. The mid-thigh circumference and D3 of the injured limbs were always greater than those of the normal limbs (p<0.001). However, D3 of both sides was less than 10 mm in 3 patients.Conclusion To lessen the vascular injury during hip nailing, we recommend that the limb be placed in neutral position during preparation of the interlocking holes.  相似文献   
996.
The pattern of childhood non-Hodgkin's lymphoma (NHL) usually differs in adults. The most common subtypes are lymphoblastic, Burkitt's and anaplastic large cell lymphoma. Recent data indicate that a higher risk of developing lymphoma is associated in children of certain ethnic origins. The difference is probably related to the underlying etiological factors of these diseases, and Epstein-Barr virus (EBV) is a strong candidate. The present study aims to determine the disease pattern of childhood lymphomas in the University Hospital Kuala Lumpur, for a direct comparison to the reported data of adults from the same medical center. A total of 69 and 34 childhood NHL and Hodgkin's lymphomas, respectively, were retrieved. The most common subtypes were lymphoblastic (23 cases), Burkitt's (25 cases) and anaplastic large cell lymphomas (9 cases). Epstein-Barr virus association was more prevalent in B-cell (23%) than T-cell (12%) lymphomas. The most common EBV-associated tumor was Burkitt's lymphoma, and there was an increased risk of EBV association for Burkitt's lymphoma in Chinese patients. In conclusion, the pattern of childhood lymphoma in Malaysia is relatively similar to children elsewhere in the world. The EBV association of B- and T-NHL differs between children and adults from the same medical center because of differences in the subtype composition in these two age groups.  相似文献   
997.
Neurosteroids are synthesized de novo and involved in a variety of physiological functions in the central and peripheral nervous systems. Although the steroidogenic acute regulatory protein (StAR) plays an essential role in the steroidogenesis of peripheral endocrine glands, its presence and role in the brain had been previously questioned because of difficulties in detecting it. However, a number of recent studies have confirmed the presence of StAR in rodent and human brains. Moreover, there is evidence suggesting that StAR plays a role in steroidogenesis in the brain, as it does in peripheral endocrine organs. The present review presents data regarding the presence and role of StAR in brain steroidogenesis, demonstrating the essential characteristics of the protein.  相似文献   
998.
Objective To evaluate the efficacy and safety of misoprostol in term labour induction. Data sources Data from published English and Chinese literatures about misoprostol in term labour induction were identified from Medline and CBMdisk (using the search terms “misoprostol” and “labour induction”) before 2001; hand searches of reference lists of original studies and reviews (including meta-analyses) and contact with investigators in this field before 2001. Study selection Studies were included if they had data on misoprostol and labour induction. Altogether 623 articles were found and 124 were admitted, including 19 287 cases. Data extraction Data were collected on efficacy and incidence of side-effects of misoprostol and oxytocin. Data were checked for consistency within the published articles and converted into a standard format for incorporation into a central database. Data synthesis The average successful induction rate, rates of caesarean section; incidence of tachysystole, hypertonus of uterus and precipitous labour, and rates of meconium stained amniotic fluid between the misoprostol and oxytocin groups were significantly different (P&lt;0.05). There were no significant differences between the two groups concerning the average interval from the administration of misoprostol and oxytocin to the onset of labour, duration of the total stage of labour, incidence rate of foetal distress, neonatal asphyxia (1-minute Apgar score≤7), postpartum haemorrhage or amount of blood loss in postpartum.Conclusions Misoprostol is a superior agent over oxytocin on the induction of term labour, but its application might increase the risk of precipitatous labour, abnormal uterine contractions or meconium stained amniotic fluid. Therefore, the doasges and regimens of the agent need further investigation.  相似文献   
999.
1000.
Penetration of epithelial cells represents the rate-determining step for the absorption of many drugs and pharmaceutical macromolecules such as proteins and nucleic acid therapeutics. While the potential of using cell-penetrating peptides (CPPs) to facilitate absorption has been increasingly recognized, the mechanism of cell penetration and the uptake into certain cells have recently been called into question due to methodological artifacts. Therefore, the objective of this study was to quantitatively assess the ability of RI-Tat-9, a proteolytically stable CPP, to penetrate epithelial cell monolayers. The permeability of RI-Tat-9 with two epithelial cell lines, Madin-Darby canine kidney (MDCK) and Caco-2 cells, was comparable to the leakiness of the respective intact monolayers. Microscopic imaging showed that fluorescence-tagged RI-Tat-9 did not enter these cells, further supporting a paracellular transport mechanism. Although insufficient data were generated in these studies to generalize the observed phenomenon, the entry of RI-Tat-9 into nonepithelial T lymphocytic MT2 cells, possibly by endocytosis, suggested that a cell type-specific barrier might exist that controlled uptake of RI-Tat-9 by cells. Compared to that in MT2 and HeLa cells, the active uptake of the peptide into MDCK monolayers was much slower and showed no dependence of cell energy. Furthermore, the equilibrium binding of RI-Tat-9 to MDCK cells at 0 degrees C was indicative of an interaction with a nonspecific receptor. A correlation between binding density and concentration difference across a leaky separation barrier suggested that repulsion of free peptide molecules by bound peptide molecules at the MDCK monolayer surface may be significant at micromolar concentrations. The results of this study quantitatively show that Tat CPP uptake into two commonly used epithelial cell types is minimal and possibly cell type-specific. Implications for Tat CPP-assisted drug delivery are discussed.  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