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   10957篇
  免费   490篇
  国内免费   52篇
耳鼻咽喉   137篇
儿科学   121篇
妇产科学   99篇
基础医学   1384篇
口腔科学   244篇
临床医学   692篇
内科学   2513篇
皮肤病学   198篇
神经病学   892篇
特种医学   426篇
外科学   2204篇
综合类   50篇
一般理论   1篇
预防医学   413篇
眼科学   184篇
药学   909篇
中国医学   39篇
肿瘤学   993篇
  2022年   110篇
  2021年   185篇
  2020年   98篇
  2019年   145篇
  2018年   163篇
  2017年   144篇
  2016年   187篇
  2015年   166篇
  2014年   211篇
  2013年   327篇
  2012年   413篇
  2011年   477篇
  2010年   257篇
  2009年   254篇
  2008年   364篇
  2007年   452篇
  2006年   431篇
  2005年   423篇
  2004年   419篇
  2003年   405篇
  2002年   439篇
  2001年   421篇
  2000年   446篇
  1999年   404篇
  1998年   141篇
  1997年   123篇
  1996年   106篇
  1995年   79篇
  1994年   80篇
  1993年   76篇
  1992年   351篇
  1991年   308篇
  1990年   312篇
  1989年   290篇
  1988年   281篇
  1987年   281篇
  1986年   275篇
  1985年   213篇
  1984年   142篇
  1983年   141篇
  1982年   50篇
  1981年   55篇
  1979年   115篇
  1978年   56篇
  1977年   56篇
  1974年   51篇
  1973年   60篇
  1972年   65篇
  1970年   49篇
  1969年   46篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
Abstract: Light microscopic observations on the superficial pineal gland of Wistar-King rats were made to examine whether or not pineal volume and pinealocyte size, expressed as nuclear density, at daytime or nighttime are affected by long-term exposure to 50 Hz rotating magnetic field (MF) at 5.0 μT. Determinations of pineal volume and pinealocyte size were repeated twice (April and October) during the year. Size of pinealocytes in MF-exposed and sham-exposed rats exhibited, in addition to the difference between peripheral and central regions, regional differences in a proximodistal direction; pinealocytes in the distal and middle-peripheral regions were usually larger than those in the proximal and middle-central regions at daytime or nighttime. In October, distal and proximal pinealocytes showed significant day-night changes in size in sham-exposed rats, but not in MF-exposed animals. The situations in the two groups were almost reversed in April. Significant day-night differences were scarcely found in pinealocyte size in the middle region in the two groups. Throughout the study, pineal volume and pinealocyte size in each region were generally the same between MF-exposed and sham-exposed rats at daytime or nighttime. The results suggest that pinealocytes in the distal and proximal regions, but not those in the middle region, are affected by MF-exposure; day-night differences in sizes of distal and proximal pinealocytes appear in April and disappear in October under the influence of MF. MF may exert an effect on mechanisms controlling day-night rhythms of pinealocyte size in the rat.  相似文献   
12.
We describe an infertile man with normal secondary sexual characteristics and a 45X karyotype. Physical examination showed bilateral soft small testes and the semen contained no sperm. Serum testosterone, estrogen and gonadotropin levels were within normal range. Biopsy of the testis showed germinal aplasia.  相似文献   
13.
In order to investigate whether intravenous bolus injection of isosorbide dinitrate (ISDN) is a safe and efficient therapy in aged patients with congestive heart failure, we studied acute hemodynamic effects in 11 patients. Peak effects on preload were observed after 5 to 10 minutes of bolus injection and unloading effects continued effectively for 60 minutes. At peak effect, pulmonary systolic pressure decreased from 50.2 +/- 2.6 to 36.2 +/- 2.6 mmHg (-28.5%, p less than 0.01) and pulmonary end diastolic pressure decreased from 25.0 +/- 2.2 to 18.5 +/- 2.1 mmHg (-26.0%, p less than 0.01). Mean pulmonary artery wedge pressure decreased from 23.4 +/- 2.2 to 16.0 +/- 2.1 mmHg (-31.6%, p less than 0.01). Mean right atrial pressure decreased from 10.5 +/- 1.8 to 7.4 +/- 2.0 mmHg (-29.5%, p less than 0.01). Blood pressure, heart rate, cardiac index, systemic and pulmonary vascular resistance showed no significant changes. Thus, intravenous bolus injection of ISDN showed a potent vasodilator effects on preload, and may be a safe and useful treatment for aged patients with acute congestive heart failure.  相似文献   
14.
We encountered a rare case of hypersensitivity pneumonitis associated with bilateral hilar lymphadenopathy (BHL). The patient was a 53-year-old male, who developed dry cough and shortness of breath when using a humidifier since 1982. He was admitted to our hospital for further evaluation in 1987. Chest X-ray films showed BHL and ground glass appearance in the bilateral lung fields. Pulmonary function test indicated disturbance of diffusing capacity. Transbronchial lung biopsy revealed interstitial pneumonitis, and lymph node biopsy by mediastinoscopy showed lymphoid sinus histiocytosis without noncaseating granuloma. Provocation test using the humidifier was positive, and the diagnosis of humidifier lung with BHL was made.  相似文献   
15.
A 40-year-old man who lived in a wooden house built 30 years ago presented with complaints of fever, dry cough and dyspnea. Chest X-ray findings showed interstitial shadows throughout bilateral lung fields. After admission, high-dose administration of 3000 mg of methylprednisolone was performed because of deterioration of chest X-ray shadows and symptoms. In a week, clinical data and symptoms improved. Findings of BAL fluid on admission revealed a relative increase of lymphocytes, neutrophils and mast cells, and pathological findings of transbronchial lung biopsy revealed non-caseous granulation and alveolitis. Precipitating antibodies and indirect fluorescent antibodies against Trichosporon cutaneum and Cryptococcus neoformans had positive reactions and T. cutaneum was isolated and identified from the patient's house. A diagnosis of summer-type hypersensitivity pneumonitis was made according to the criteria advocated by Ando et al. This seemed to be a rare case of summer-type hypersensitivity pneumonitis prolonged after isolation from his normal living environment, successfully treated by high-dose administration of steroid.  相似文献   
16.
Oral adsorbent (AST-120) reduces blood levels of urea and creatinine in experimental studies. It has also been shown to retard the progression of chronic renal failure in clinical studies. In the present study, the effect of AST-120 was examined in the rat model of subtotal nephrectomy (sNPX). This experimental model of chronic renal failure is characterized by glomerular hyperfunction, glomerular hypertrophy, increased mesangial trapment of macromolecules and subsequent glomerular sclerosis. We report the effect of AST-120 on glomerular hyperfunction, glomerular hypertrophy and mesangial trapment of macromolecules in the early stage and glomerular function and histology in the late stage of the rat model of sNPX. From 2 days after sNPX, rats were fed regular rat chow with (AST group: AST) or without (control) AST-120. At 2 weeks, iron dextran (ID) was injected intravenously. Three days after the injection, mesangial trapment of ID was largely ameliorated in AST when compared with control (p less than 0.02). The value of mean planar area of glomerulus (PAmean) in AST was significantly lower than that in control (p less than 0.05). At 2 and 9 weeks, the values of GFR and RPF in AST were all statistically higher than those in control. At 9 weeks, whereas average glomerular sclerosis index (SI: 0-4 scale) was 1.07 in control, significantly lower SI (0.57) was noted in AST (p less than 0.05). Thus, AST-120 has effects on glomerular hypertrophy, increased mesangial trapment of macromoleculus and finally the progression of chronic renal failure in the rat model of sNPX. The effects are not through reducing glomerular hyperfunction.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
17.
During the past 4 years, the performances of various tumor markers such as CA15-3, CEA, ferritin, beta 2-microglobulin and TPA have been evaluated in 78 cases of mammary cancer. The results were categorised according to differences in stages, difference in values from patients with recurrent tumors, the incidence of abnormal values and differences in values before and after surgery. When the incidence of values higher than the cutoff value was determined for each of stage I, II and III + IV, the rates for CEA were 14.3%, 4.9% and 27.8%, respectively, whereas those for TPA were 25.0%, 22.2% and 26.7%, respectively. In addition, for CA15-3, the incidences were 0% in stage I, 5.0% in stage II and 57.1% for combined stages III + IV. The average values for patients with recurrent tumors were 3.2 ng/ml CEA, 194.5 ng/ml ferritin, 316.2 U/l TPA and 81.3 U/ml CA15-3. The rates of abnormal values were 40.0% for CEA, 40.0% for ferritin, 85.7% for TPA and 63.6% for CA15-3. Differences in the values after surgical removal of the tumor were observed with these tumor markers: the CEA value was reduced from 1.6 +/- 1.4 to 1.1 +/- 0.5 (p less than 0.01) and the CA15-3 value from 12.2 +/- 8.4 to 9.3 +/- 4.1 (p less than 0.05), respectively, whereas that for ferritin was conversely increased from 48.9 +/- 48.0 to 74.0 +/- 70.0 (p less than 0.01). However, the values for TPA, despite showing a tendency to decrease, did not show any statistically significant alteration. The fluctuations of these marker levels in patients with recurrent tumors reflects the progress of the disease, with a sudden elevation in values indicating imminent death. The diagnostic significance of these markers is not high, but they are considered to be useful in detecting the progress or condition of a recurrent tumor.  相似文献   
18.
A 50-year-old man with the symptom of anal pain was treated by pelvic exenteration, ileal conduit diversion and artificial anus. The pathologic diagnosis was leiomyosarcoma of the prostate. At 5 months post-operatively, the patient had no evidence of metastasis or recurrence.  相似文献   
19.
Ontogenesis of neural segments and positional relationships between the segments and other organs during neurulation were studied in 1,423 ICR mouse embryos by binocular dissecting, light, and scanning electron microscopy. Late in the presomite stage, two transverse sulci, preotic and otic, were seen on the prospective luminal surface of the neural folds. By somite stage 19, the former subdivided into five neuromeres, and by somite stage 21, the latter subdivided into four neuromeres. From the rostral, preotic sulcus, moreover, five other neuromeres were formed by somite stage 20, and between the otic sulcus and the first somite, two neuromeres were formed by somite stage 28. In the caudal part, from the level of the first somite, a total of 39 neuromeres were formed one after another by somite stage 39, and their positions almost correlated with each corresponding somite. Furthermore, the isthmus grew in the boundary between the fifth and sixth neuromere. The most protruding zone in the preotic sulcus formed the eighth neuromere and was located adjacent to the first branchial arch and the trigeminal ganglion. The most protruding zone in the otic sulcus also formed the 11th neuromere and was located adjacent to the second branchial arch. The 12th and 13th neuromeres were situated adjacent to the otic vesicle; the 23rd to 28th neuromeres, adjacent to the forelimb bud; and the 40th to 46th neuromeres, adjacent to the hindlimb bud.  相似文献   
20.
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