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   13867篇
  免费   675篇
  国内免费   96篇
耳鼻咽喉   192篇
儿科学   267篇
妇产科学   146篇
基础医学   1718篇
口腔科学   326篇
临床医学   836篇
内科学   3693篇
皮肤病学   187篇
神经病学   1219篇
特种医学   547篇
外科学   2541篇
综合类   52篇
一般理论   2篇
预防医学   324篇
眼科学   126篇
药学   898篇
中国医学   22篇
肿瘤学   1542篇
  2024年   14篇
  2023年   98篇
  2022年   193篇
  2021年   324篇
  2020年   156篇
  2019年   266篇
  2018年   319篇
  2017年   258篇
  2016年   311篇
  2015年   334篇
  2014年   412篇
  2013年   530篇
  2012年   868篇
  2011年   892篇
  2010年   554篇
  2009年   466篇
  2008年   871篇
  2007年   965篇
  2006年   914篇
  2005年   909篇
  2004年   888篇
  2003年   844篇
  2002年   853篇
  2001年   172篇
  2000年   155篇
  1999年   164篇
  1998年   235篇
  1997年   160篇
  1996年   157篇
  1995年   97篇
  1994年   99篇
  1993年   109篇
  1992年   138篇
  1991年   106篇
  1990年   109篇
  1989年   71篇
  1988年   84篇
  1987年   66篇
  1986年   57篇
  1985年   59篇
  1984年   49篇
  1983年   61篇
  1982年   23篇
  1981年   27篇
  1980年   29篇
  1979年   19篇
  1978年   21篇
  1977年   19篇
  1975年   18篇
  1972年   15篇
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
991.
992.
Microvascular lesions are a predominant feature in systemic sclerosis (SSc) and seem to play a central pathogenic role. The presence of nailfold capillary abnormalities is useful in diagnosing SSc. Capillaroscopy, however, usually requires special equipment and may be time consuming. Dermatoscope has been presented as a new diagnostic tool for quick and efficient examination of nailfold capillaries for circumstances when standard microscope equipment is not available. To assess the practical utility of dermatoscope for assessment of capillary morphology in patients with SSc, 83 Japanese patients with SSc (68 women, 15 men) and 68 healthy controls were examined in the study. Twenty-one patients (16 women, 5 men) had diffuse cutaneous SSc and 62 (52 women, 10 men) had limited cutaneous SSc. Enlarged capillaries and hemorrhages were evaluated in all 10 fingers with either naked eyes or DermLite? DL100 dermatoscope. Enlarged capillaries and hemorrhages were significantly more frequently detected with dermatoscope than without it. These findings were observed most frequently in the fourth finger. The presence of two or more enlarged capillaries in one or more fingers showed 83.1% sensitivity and 100% specificity for SSc. Among patients with SSc with anti-topoisomerase I antibody, the disease duration correlated negatively with the dermatoscopic number of enlarged capillaries and hemorrhages. Dermatoscope allows the easy and rapid identification of capillary nailfold morphological changes in SSc and should be routinely used for diagnosing SSc.  相似文献   
993.
Ascidians belong to the primitive chordates and their larvae show symmetrical beating of the tail, which is reminiscent of the swimming pattern in primitive vertebrates. Since ascidian larva contains only a small number of neurons in their entire larval nervous system, they will potentially provide a simple model for the study of animal locomotion. In a step towards the goal of establishing the molecular basis underlying ascidian larval neurophysiology, we describe here a Kv4 class of voltage-gated potassium channel, TuKv4, from Halocynthia roretzi. Whole mount in situ hybridization indicates that TuKv4 is expressed in most of larval neurons including motor neurons. TuKv4-currents reconstituted in Xenopus oocytes show currents with similar properties to the lower-threshold A-type currents from cleavage-arrested ascidian blastomeres of neural lineage. However, the voltage-dependency of the steady-state inactivation and activation was shifted leftward by 20 mV, as compared with native A-type currents, suggesting that other components may be required to restore full function of the Kv4 channel. Unexpectedly, another isoform lacking C-terminal cytoplasmic region was also isolated. This truncated isoform did not lead to a functional current in Xenopus oocytes. RT-PCR analysis showed that the truncated form is transiently expressed during larval development, suggesting some developmental role for potassium channel expression.  相似文献   
994.
Increased neutrophil counts have been associated with an increased risk of adverse clinical events after acute myocardial infarction (AMI). We examined the association of neutrophil counts on admission with degree of microvascular injury and left ventricular functional recovery after primary coronary angioplasty in AMI. We studied 116 patients with a first anterior wall AMI who underwent primary coronary angioplasty within 12 hours of onset. Patients were categorized into 3 groups based on initial neutrophil count: low (<5,000/mm(3)), intermediate (5,000 to 10,000/mm(3)), and high (>10,000/mm(3)). Coronary flow velocity parameters were assessed immediately after reperfusion using a Doppler guidewire. We defined severe microvascular injury as the presence of systolic flow reversal and a diastolic deceleration time <600 ms. Echocardiographic wall motion was analyzed before revascularization and 4 weeks after revascularization. In patients with a high neutrophil count, systolic flow reversal was more frequently observed, diastolic deceleration time was shorter, and coronary flow reserve was lower. By regression analysis, neutrophil count significantly correlated with diastolic deceleration time (r = -0.38, p <0.0001), coronary flow reserve (r = -0.33, p = 0.0004), and score for change in wall motion (r = -0.36, p = 0.0004). Multivariate analysis showed that neutrophil count on admission was an independent predictor of severe microvascular injury (odds ratio 2.94, p = 0.02). In conclusion, neutrophilia on admission is associated with impaired microvascular reperfusion and poor functional recovery after primary coronary angioplasty.  相似文献   
995.
PURPOSE: We evaluated the usefulness of magnetic resonance imaging for the preoperative diagnosis of deep anorectal abscesses. METHODS: Subjects were 21 patients with deep anorectal abscesses. Deep anorectal abscesses were classified into two types, ischiorectal and pelvirectal, according to their location. Patients were also classified into a single abscess group, which showed either an ischiorectal or pelvirectal abscess, and a double abscess group, which showed both ischiorectal and pelvirectal abscesses. The final diagnosis was made from surgical findings, and the types of deep anorectal abscesses determined by digital examination and magnetic resonance imaging were compared. RESULTS: Sensitivity of ischiorectal abscesses (20 lesions) with digital examination and magnetic resonance imaging was 75 and 95 percent, respectively, and that of pelvirectal abscesses (10 lesions) with digital examination and magnetic resonance imaging was 60 and 70 percent, respectively. Sensitivity of the magnetic resonance imaging was significantly higher than that of digital examination in ischiorectal abscesses. Diagnostic accuracy of digital examination and magnetic resonance imaging were both 83 percent in the single abscess group (12 patients), whereas in the double abscess group (9 patients) it was 22 and 78 percent, respectively. The rate of accurate diagnosis of magnetic resonance imaging compared with digital examination in the double abscess group was significantly higher than that in the single abscess group. CONCLUSION: Magnetic resonance imaging was useful for diagnosing and differentiating ischiorectal and pelvirectal abscesses.  相似文献   
996.
A 62‐year‐old man with precordial pain and fever consulted a local practitioner. Blood tests revealed jaundice. Acute cholecystitis was diagnosed on ultrasonographic examination, and percutaneous transluminal gall‐bladder drainage was performed. The patient was referred to the Department of Surgery for operation. Imaging studies performed via a drain disclosed compression and stenosis of the lower portion of the common bile duct. A computed tomographic scan showed a multilocular nodule‐like low‐density area measuring 2.0 × 2.0 cm in diameter at the head of the pancreas. Endoscopic retrograde cholangiopancreatography disclosed compression and stenosis of the main pancreatic duct at the head of the pancreas. Angiographic examination revealed encasement of the intrapancreatic branch of the posterior pancreatic arcade, located in the same area as the compression stenosis of the bile duct. The results of imaging studies suggested cancer of the head of the pancreas, and a pancreatoduodenectomy was performed. The resected specimen included a mass measuring 3.5 × 2.7 × 1.7 cm, which was located at the head of the pancreas. On examination of a cut section, the mass was found to consist of small multilocular cysts. The cysts invaded the intrapancreatic bile duct. The histopathological diagnosis was serous cystadenoma.  相似文献   
997.
Duodeno-gastro-esophageal reflux has been thought to induce Barrett's esophagus. Recently, we designed a new duodenal reflux model using rats, and studied sequential morphological changes of esophageal mucosa leading to Barrett's esophagus. A specialized columnar epithelium (SCE) developed 20 weeks after operation. Barrett's epithelium originated from pyloric-foveolar metaplasia of stem cells in the basal layer of the esophageal squamous epithelium. The pyloric-foveolar metaplasia was then followed by the appearance of goblet cells, becoming a typical SCE. The expression of homeobox gene Cdx2 was seen in this process, thereby suggesting a role of Cdx2 in intestinal differentiation of Barrett's esophagus. We noticed the pyloric-foveolar metaplasia followed by the appearance of goblet cells is common to entire gut in regenerative process, and proposed a concept of GRCL (gut regenerative cell lineage), and an implication of GRCL in digestive tract carcinogenesis was discussed.  相似文献   
998.
A new series of (E)-3-styrylpyridine derivatives as potential diagnostic imaging agents targeting amyloid plaques in Alzheimer's disease (AD) were synthesized and examined. When in vitro binding studies using AD brain homogenates were carried out with a series of styrylpyridine derivatives, (E)-2-Bromo-5-(4-dimethylaminostyryl)pyridine (7) with a dimethylamino group showed the highest binding affinity. Compound 7 intensely stained neuritic and diffused plaques and cerebrovascular amyloids on postmortem AD brain sections. (E)-2-Iodo-5-(4-dimethylaminostyryl)pyridine, the iodo derivative of compound 7, also stained senile plaques in human AD sections. The radioiodinated ligand [125I] was successfully prepared through an iododestannylation reaction from the corresponding tributyltin derivatives using hydrogen peroxide as the oxidant in high yields and with high radiochemical purity. A biodistribution study in normal mice after an intravenous injection of [125I] displayed high brain uptake and fast washout. Taken together, the data suggest that the new radio tracer, [125I], may be useful as a radioiodinated imaging agent for mapping A beta plaques in the brains of patients with AD.  相似文献   
999.
The efficacy of elective neck irradiation (ENI) for patients with N0 carcinoma of the maxillary sinus has been controversial. The purpose of our study was to investigate the incidence of late neck recurrence and the mortality rate from regional disease in patients with N0 maxillary sinus cancer after superselective cisplatin infusion and concomitant radiotherapy (RADPLAT) without ENI. We retrospectively analyzed 48 patients with N0 maxillary sinus cancer who underwent RADPLAT. Chemotherapy consisted of 100–120 mg/m2 superselective intra-arterial cisplatin administered at a median rate of four times weekly. Concurrent radiation therapy was administered at a median dose of 65 Gy without ENI. Late neck recurrence was observed in 8.3 % (4/48). Three patients underwent salvage neck dissection and survived without any evidence of disease. The remaining patient did not undergo neck dissection due to coexistence with distant metastasis, and he died of regional disease. The mortality rate from regional disease was calculated to be 2 % (1/48). The incidence of late neck recurrence was not frequent, and the mortality rate from regional disease was low. Salvage neck dissection was considered to be feasible for patients with late neck recurrence. When definitive radiotherapy and concomitant chemotherapy are applied, it is considered that ENI is not required for cases of N0 maxillary sinus cancer.  相似文献   
1000.
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