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   36426篇
  免费   1869篇
  国内免费   159篇
耳鼻咽喉   503篇
儿科学   654篇
妇产科学   437篇
基础医学   4532篇
口腔科学   1167篇
临床医学   2563篇
内科学   8328篇
皮肤病学   771篇
神经病学   3407篇
特种医学   1846篇
外国民族医学   1篇
外科学   5771篇
综合类   126篇
一般理论   6篇
预防医学   1150篇
眼科学   759篇
药学   2342篇
中国医学   71篇
肿瘤学   4020篇
  2023年   177篇
  2022年   302篇
  2021年   665篇
  2020年   378篇
  2019年   498篇
  2018年   625篇
  2017年   511篇
  2016年   658篇
  2015年   630篇
  2014年   827篇
  2013年   993篇
  2012年   1645篇
  2011年   1646篇
  2010年   1017篇
  2009年   853篇
  2008年   1508篇
  2007年   1761篇
  2006年   1594篇
  2005年   1536篇
  2004年   1559篇
  2003年   1431篇
  2002年   1488篇
  2001年   1328篇
  2000年   1430篇
  1999年   1292篇
  1998年   474篇
  1997年   391篇
  1996年   369篇
  1995年   305篇
  1994年   306篇
  1993年   282篇
  1992年   996篇
  1991年   858篇
  1990年   817篇
  1989年   807篇
  1988年   765篇
  1987年   758篇
  1986年   671篇
  1985年   624篇
  1984年   423篇
  1983年   345篇
  1979年   297篇
  1978年   199篇
  1977年   177篇
  1974年   190篇
  1973年   165篇
  1972年   163篇
  1971年   185篇
  1970年   162篇
  1969年   182篇
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
41.
OBJECTIVE: To evaluate a proposed technique for the 3-dimensional (3D) detection of hemangiomas, including vascular malformation and their feeding arteries, in the head and neck. The new technique combines phase-contrast magnetic resonance angiography (PCMRA) without contrast medium and 3D fast asymmetric spin-echo (FASE) sequences. METHODS: The technique was applied to 3 patients having hemangiomas in the head and neck region. In 1 patient the image obtained with the proposed technique was compared to that obtained by standard contrast angiography. RESULTS: In all 3 patients, the 3D presence of the hemangiomas and the feeding arteries were well defined in images created by the proposed technique. Additionally, the characterization of the hemangioma's 3D structure and distribution of the feeding arteries coincided with those observed using contrast angiography in the case for which contrast angiography was also performed. CONCLUSIONS: Preliminary experience shows that the proposed technique combining 3D-FASE and 3D-PCMRA is useful to visualize both the 3D structure of hemangiomas and to identify the 3D distribution of the feeding arteries without using contrast medium.  相似文献   
42.
43.
Lymphoepithelioma is a lymphocyte-rich, poorly differentiated and non-keratinizing squamous cell carcinoma of the nasopharynx. Tumors arising outside the nasopharynx are rare and are designated as lymphoepithelioma-like carcinomas (LELCs). This is the third reported case of LELC of the trachea. A 27-year-old woman was referred to our hospital on suspicion of bronchial asthma on August 2000. A polypoid tumor of the cervical trachea was recognized on neck X-ray, neck computed tomography (CT) scan, and fiberoptic bronchoscopy. The protruding tumor was resected endoscopically by an electrosurgical snare. Histological and immunohistochemical examinations demonstrated large irregular polygonal cells extending in an islet or trabecular pattern among lymphoid stroma. These polygonal cells showed non-keratinization, atypia and prominent nucleoli. In situ hybridization showed these cells were infected with the Epstein-Barr (EB) virus. The infiltrating lymphocytes consisted of both T-and B-lymphocytes with no atypia. Thus the tumor was diagnosed as LELC. Blood examination revealed a past EB viral infection. Sphenoid resection of the tracheal cartilaginous portion was performed for residual tumor. We gave 50 Gy postoperative radiation, and she has been disease free in the 6-year follow-up period.  相似文献   
44.
45.
Characterization of estrogen receptor in human gastric cancer   总被引:13,自引:0,他引:13  
M Matsui  O Kojima  Y Uehara  T Takahashi 《Cancer》1991,68(2):305-308
Estrogen receptors (ER) were examined in cytosol, nuclear potassium chloride (KCl) extractable fraction, and nuclear KCl unextractable fraction by the dextran-coated charcoal adsorption method in various gastric cancer tissue. The overall ER-positive rate in the cytosol and nuclear fraction was 19.2%. The maximum binding site (Bmax) was 36.0 to 175.0 fmol/mg of protein, and the dissociation constant (Kd) was 0.6 to 1.6 X 10(-9) in cytosol fraction. In the nuclear fraction, Bmax was 7.5 fmol/mg of DNA and Kd was 2.3 X 10(-9). Estrogen receptors were characterized in cytosol protein. In cytosol, the estrogen (E2)-ER complex was sedimented at approximately the 5S and 8S regions by 5% to 20% linear sucrose gradient centrifugation. A steroid specificity study of ER showed the presence of an binder in gastric cancer tissue. In conclusion, these results that gastric cancer tissue has E2 binding sites with the same biochemical characteristics as in breast cancer and endometrial cancer strongly suggest the hormonal dependency of gastric cancer.  相似文献   
46.
A 13-year-old girl who had severe brain damage due to unknown prenatal cause presented rhabdomyolysis triggered by a mild viral infection. Her muscle biopsy revealed mild variation in fiber size and type 2 fiber atrophy without excess lipid storage. Biochemical analysis of the biopsied material showed decreased carnitine palmitoyltransferase (CPT) activity (15% of the control). Serum and urinary carnitine levels were normal. Skeletal muscle CT scanning showed multiple low density spots. The patient was diagnosed as having CPT deficiency. She recovered from rhabdomyolysis without renal failure after a month with conservative therapy. CPT deficiency is usually found in young healthy persons. This is the first case report of CPT deficiency which presented severe psychomotor retardation since neonatal period.  相似文献   
47.
OBJECTIVES: To determine the value of the loss of expression of E-cadherin and cadherin associated molecules as useful markers for both prognosis and chemosensitivity in bladder cancer patients who have undergone radical cystectomy. PATIENTS AND METHODS: In 55 paraffin embedded specimens of radical cystectomy at our hospital from 1982 to 2000, the expression of E-cadherin, alpha-, beta- and gamma-catenin was examined by immunohistochemical staining. To evaluate the prognostic significance of these molecules, Kaplan-Meier survival curves were constructed and a statistical analysis was calculated by a log-rank test. A multivariate test (tumor stage, tumor grade, lymph node metastasis, configuration, the expression of E-cadherin, alpha-, beta- and gamma-catenin) was performed to detect prognostic markers. RESULTS: Normal expression was found in 33 cases (60.0%) for E-cadherin, 29 (52.7%) for alpha-catenin, 31 cases (56.4%) for beta-catenin, and 31 cases (56.4%) for gamma-catenin. The expression patterns for E-cadherin, alpha-, beta- and gamma-catenin were significantly correlated with each other (P < 0.01). Survival analysis showed a significant difference between normal and aberrant expression in each staining. A multivariate analysis revealed that the expression of alpha- catenin was an independent prognostic factor (P = 0.0191). In 23 patients that received adjuvant chemotherapy, there was a significant difference in survival between the normal and aberrant expression of alpha-catenin, but not other molecules. CONCLUSION: Alpha-catenin may not only be a good prognostic marker, but also one of key molecules that determine the chemosensitivities in patients with invasive bladder cancer.  相似文献   
48.
The incidence of stonestreet formation after extracorporeal shock wave lithotripsy (ESWL) rises with increasing stone burden. However, stonestreet after ESWL is often experienced even in stones smaller than 20 mm. To examine whether the non-contrast helical computed tomography (CT) data could predict stonestreet formation in these stones, 53 radiopaque stones of 5-20 mm treated with ESWL were evaluated. Maximal dimension was measured on plain radiograph. From an attenuation value histogram graphed from the CT data, total stone volume and mean attenuation value were calculated. Seven stonestreets longer than 25 mm developed. There was no significant difference in maximal dimension and total stone volume between stones that did and stones that did not develop stonestreet. Mean attenuation value was the sole significant predictive factor. Application of mean attenuation value with cut-off level of 650 HU would anticipate stonestreet formation with a sensitivity of 85.7% and a specificity of 71.7%. The estimated risk of stonestreet formation is high in the treatment of stones with higher mean attenuation value.  相似文献   
49.
OBJECTIVE: Although hypercalciuria, a well-established adverse effect of vitamin D3, can be a risk factor of renal stone formation, the risk of nephrolithiasis has not been well defined. The consumption of a diet high in acid precursors is often cited as a risk factor for the development of calcium-based kidney stones. In the present study, we investigated the effect of chronic acid ingestion on kidney stone formation in rats treated with calcitriol (1-25[OH]2 D3). METHODS: Control rats (C-C), calcitriol-treated rats (C-V; three treatments of 0.5 microg of calcitriol per week) and acid-ingested (water containing 0.21 mol/L NH4Cl), calcitriol-treated (three treatments of 0.5 microg of calcitriol per week) rats (A-V) were fed in metabolic cages. After 1 month, urine, blood, kidney and bone samples were analyzed. RESULTS: The A-V rats exhibited elevated serum calcium concentrations, urinary calcium and phosphate excretion, urinary type I collagen cross-linked N-peptide (NTx)/creatinine values, mRNA expression of osteopontin in the kidney, and renal calcium contents as well as decreased bone mineral densities, compared with the C-C and C-V rats. Urinary citrate excretion was lower and NaDC-1 mRNA expression in the kidney was higher in the A-V rats than in the C-C and C-V rats. Calcium phosphate kidney stones were found in the A-V rats. CONCLUSIONS: The ingestion of NH4Cl, an acid precursor, promotes calcium phosphate kidney stone formation in calcitriol-treated rats. The chronic intake of a diet rich in acid precursors may be a risk factor for the development of kidney stones in subjects who are being treated with calcitriol.  相似文献   
50.
A 75-year-old man had been admitted to another hospital because of left abdominal pain, and was given a diagnosis of left hydronephrosis and acute pancreatitis. After a JJ stent insertion and medication, he was transferred to our hospital for further examinations. US and EUS revealed a chronic pancreatitis-like pattern and multicystic lesion in the pancreas head and body. At that time enhanced CT findings showed an extrapancreatic low density area to be inflammatory change, extending from the pancreas body to the left crus of the diaphragm and posteriorly the spreading from the left crus of the diaphragm via the left urinary duct into the left iliopsoas muscle, in which MRI revealed partial high intensity. ERCP and MRCP showed focal irregular narrowing of the pancreatic duct of unknown cause, and we decided that an internal pancreatic fistula due to pancreatitis had induced left ureteral obstruction, caused by a protein plug or alcohol. Follow-up 6 months later showed that extrapancreatic spreading of the low density area had markedly regressed without any change in the ureteral obstruction.  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