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   20480篇
  免费   1174篇
  国内免费   195篇
耳鼻咽喉   133篇
儿科学   1182篇
妇产科学   299篇
基础医学   2476篇
口腔科学   353篇
临床医学   1239篇
内科学   3513篇
皮肤病学   414篇
神经病学   1299篇
特种医学   848篇
外国民族医学   5篇
外科学   2778篇
综合类   796篇
一般理论   1篇
预防医学   1418篇
眼科学   1072篇
药学   2025篇
  5篇
中国医学   308篇
肿瘤学   1685篇
  2022年   269篇
  2021年   408篇
  2020年   279篇
  2019年   302篇
  2018年   367篇
  2017年   295篇
  2016年   367篇
  2015年   410篇
  2014年   592篇
  2013年   782篇
  2012年   1116篇
  2011年   1134篇
  2010年   673篇
  2009年   547篇
  2008年   934篇
  2007年   956篇
  2006年   882篇
  2005年   841篇
  2004年   757篇
  2003年   757篇
  2002年   707篇
  2001年   616篇
  2000年   635篇
  1999年   571篇
  1998年   255篇
  1997年   243篇
  1996年   219篇
  1995年   198篇
  1994年   161篇
  1993年   163篇
  1992年   364篇
  1991年   390篇
  1990年   352篇
  1989年   411篇
  1988年   306篇
  1987年   324篇
  1986年   261篇
  1985年   288篇
  1984年   244篇
  1983年   213篇
  1982年   133篇
  1981年   118篇
  1979年   190篇
  1978年   124篇
  1977年   109篇
  1975年   140篇
  1974年   143篇
  1973年   136篇
  1972年   123篇
  1971年   142篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Interference in the measurement of CA-125 in peritoneal fluid   总被引:1,自引:0,他引:1  
CA-125 has been found to be mildly elevated in the serum of patients with advanced stages of endometriosis, but not with minimal endometriosis. Peritoneal fluid levels were measured in conjunction with serum levels in 12 consecutive patients with endometriosis and 12 consecutive normal controls. Apparent peritoneal fluid values were found to be 10-fold higher than serum levels, with no difference between the study groups (130 versus 106 U/ml, respectively). However, when peritoneal fluid was diluted to validate the assay system in peritoneal fluid, no sample of peritoneal fluid showed decreased binding with serial dilutions of 1:2, 1:5, and 1:10. At a dilution of 1:100, there was some decreased binding, but the level was 17-fold higher than expected. The source of this interference is unknown.  相似文献   
992.
Peritoneal endometriotic implants and adjacent normal peritoneum from five patients were analyzed for prostaglandin (PG) release. Each tissue biopsy was incubated using medium 199 in triplicate at 37 degrees C for six hours, and PGF2 alpha and PGE2 concentrations were measured in the incubation medium every two hours. This study demonstrates that peritoneum involved with endometriosis releases significantly more PGF2 alpha and PGE2 (P less than .05) than adjacent normal peritoneum, and suggests that peritoneal endometriotic implants may be a source of the elevated peritoneal fluid PG levels previously reported in patients with endometriosis.  相似文献   
993.
AIM: To assess the prevalence of active and inactive uveitis unrelated to previous surgery or trauma in an urban population in southern India. METHODS: As part of the Andhra Pradesh Eye Disease Study, 2522 subjects (85.4% of those eligible), a sample representative of the population of Hyderabad city in southern India, underwent interview and detailed dilated eye examination. Presence of sequelae of uveitis without current active inflammation was defined as inactive uveitis. RESULTS: Unequivocal evidence of active or inactive uveitis unrelated to previous surgery or trauma was present in 21 subjects, an age-sex adjusted prevalence of 0.73% (95% confidence interval (CI) 0.44-1.14%). Active uveitis was present in eight subjects, an age-sex adjusted prevalence of 0.37% (95% CI 0. 19-0.70), of which 0.06% was anterior, 0.25% intermediate, and 0.06% posterior. The 0.36% (95% CI 0.17-0.68%) prevalence of inactive uveitis included macular chorioretinitis scars (0.26%), anterior (0. 07%) and previous vasculitis involving the whole eye (0.03%). The prevalence of visual impairment due to uveitis of less than 6/18 in at least one eye was 0.27%, less than 6/60 in at least one eye was 0. 16%, and less than 6/60 in both eyes was 0.03%. CONCLUSION: These population based cross sectional data give an estimate of the prevalence of various types of uveitis in this urban population in India. Active or past uveitis that might need treatment at some stage was present in one of every 140 people in this population.  相似文献   
994.
AIM: To review the clinical characteristics, diagnosis, and visual outcome in patients with non-contact lens related Acanthamoeba keratitis and compare the findings with reported series of contact lens associated Acanthamoeba keratitis. METHODS: Medical and microbiology records of 39 consecutive patients with a diagnosis of Acanthamoeba keratitis, at a tertiary eyecare centre in India between January 1996 and June 1998, were analysed retrospectively. RESULTS: A majority of the patients presented with poor visual acuity and large corneal stromal infiltrates (mean size 38.20 (SD 26. 18) mm). A predisposing factor was elicited in 19/39 (48.7%) patients (trauma 15, dirty water splash three, leaf juice one). None of the patients had worn contact lenses. Most patients (26/39 (66. 6%)) came from a low socioeconomic background. Complaint of severe pain was not a significant feature and radial keratoneuritis was seen in 1/39 (2.5%) patients. A ring infiltrate was present in 41.1% of cases. A clinical diagnosis of fungal keratitis was made in 45% of the patients before they were seen by us. However, all patients were diagnosed microbiologically at our institute based on demonstration of Acanthamoeba cysts in corneal scrapings (34/39) and/or culture of Acanthamoeba (34/39). Treatment with biguanides (PHMB, 15/38 (39.4%), PHMB with CHx, 23/38 (60.5%), one patient did not return for treatment) resulted in healing with scar formation in 27 out of 31(87.0%) followed up patients (mean time to healing 106.9 days). Overall visual outcome was poor with no statistical difference between cases diagnosed within 30 days (early) or 30 days after (late) start of symptoms. The visual outcome in cases requiring tissue adhesive (five) and keratoplasty (three) was also poor. CONCLUSIONS: This is thought to be the largest series of cases of Acanthamoeba keratitis in non-contact lens wearers. In such cases, the disease is advanced at presentation in most patients, pathognomonic clinical features are often not seen, disease progression is rapid, and visual outcome is usually poor. Possible existence of Acanthamoeba pathotypes specifically associated with non-contact lens keratitis and unique to certain geographical areas is suggested.  相似文献   
995.
An ecofriendly synthesis for 1,2,3,4,5,6,8-octahydro- 3-amino-2-thioxo-benzothieno[2,3-d]pyrimidin-4-one (7A, B) has been developed. A series of hitherto unreported compounds (2a-i, 3a-c) have been synthesized by treating 3-Amino-2-mercaptopyrimidinones (7A, B) with one carbon donors like chloroacetyl chloride or chloroacetic acid and subsequently replacing the chloro group by various nucleophiles. Compound 2f was successfully synthesized by an alternate route. All the new compounds were characterized by elemental and spectral analyses. They were screened for analgesic activity in mice. Compounds 2a, b, 3a, b, and 2e, showed very good activity.  相似文献   
996.
Two series of 6-substituted benzimidazo[1,2-c]quinazolines (Ia-p and IIa-l) have been synthesized and characterized. The compounds were evaluated for their bronchodilator activity, in vitro and in vivo. All the test compounds exhibited good activity both in vivo and in vitro methods. The structure-activity relationships based on the results obtained for these series have also been studied. In the 6-alkyl substituted compounds II, a longer alkyl chain and a 4-substitution by an electron-withdrawing group in compounds I, showed more activity. The presence of halogens altered the biological activity in both series. Among the compounds tested, 10-iodo-6-(n-propyl)-benzimidazol[1,2-c]quinazoline (II) was found to be the most potent (% protection = 75%; relative activity = 1.1).  相似文献   
997.
Henoch schonlein syndrome (HSP) represents a diagnostic challenge when gastrointestinal symptoms or other atypical symptoms precede the cutaneous manifestations. We describe two patients whose abdominal symptoms antedated cutaneous manifestations. Six-year-old, black male patient, presented with 1 wk history of vomiting (without diarrhea or urinary symptoms), hypertension (140/90 mmHg), diffuse abdominal pain and hypoactive bowel sounds:. WBC’s 40,000/Cu mm3 with 80 percent hypoproteinemia, (albumin 1.6 G%), high plasma renin and stools positive for occult blood. Renal function and urinalysis was normal. Two weeks later patient developed urticarial purpuric rash over the ankles, gross hematuria and gross edema. Biopsy of the skin lesion was consistent with HSP vasculitis. Second patient 4 yr Brazilian male patient presented with abdominalpain, vomiting, blood in the stools, and pain in the right testis. Three days later, developed purpuric rash over his limbs and trunk. He also had hypoproteinemia, hypoalbuminemia, leukocytosis and normal urine analysis. Abdominal pain, bloody stools, painful testicular swelling and hypoproteinemia abated with steroid therapy. In HSP patients, atypical presentation of abdominal pain, hypertension, hypoproteinemia without proteinuria testicular swelling and leucocytosis in the absence of cutaneous and joint manifestations poses as diagnostic problem. Protein-losing enteropathy should be considered in HSP patients with hypoproteinemia.  相似文献   
998.
999.
1000.
PURPOSE: To evaluate the effect of age on the outcome of myopic photorefractive keratectomy (PRK). SETTING: University-based refractive surgery practice. METHODS: A retrospective analysis of 197 eyes that had PRK for myopia was performed. Four groups of patients were compared: Group 1, patients < 30 years (n=35); Group 2, patients 31 to 40 years (n=56); Group 3, patients 41 to 50 year s (n=47); Group 4, patients > 50 years (n=59). The percentage of eyes with an uncorrected visual acuity of 20/20 or better and 20/40 or better and the percentage of eyes with spherical correction within +/-0.5 and +/-1.0 diopter (D) of the attempted correction were derived for each age group. The percentage of patients overcorrected and undercorrected by 1.0 D or more in each age group was also calculated.The difference between the percentage of patients who achieved a visual acuity of 20/20 or better in Group 4 and in the younger groups was statistically significant at 3 months (P =.02) but not at 6 months (P =.70) and 12 months (P =.55). The difference between the percentage of patients who achieved an acuity of 20/40 or better was not significant at any time. The difference between the percentage of patients who were within +/-0.5 D of intended correction in Group 4 and in the younger groups was statistically significant at 3 months (P =.001), 6 months (P =.006), and 12 months (P =.008); the difference between the percentage of patients who were within +/-1.0 D of intended correction was not significant at any time. The difference between the percentage of patients overcorrected and undercorrected by 1.0 D or more in Group 4 and in the younger groups was not significant at any time.In the 3 younger groups, age did not significantly affect visual outcome or predictability. However, there was a significant difference between Group 4 and the 3 younger groups in predictability of the refractive outcome at 3, 6, and 12 months. Age may play a role in the outcome of refractive surgery.  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