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   8041篇
  免费   497篇
  国内免费   142篇
耳鼻咽喉   88篇
儿科学   109篇
妇产科学   130篇
基础医学   1267篇
口腔科学   202篇
临床医学   562篇
内科学   1505篇
皮肤病学   233篇
神经病学   499篇
特种医学   682篇
外科学   949篇
综合类   83篇
预防医学   265篇
眼科学   102篇
药学   1061篇
中国医学   160篇
肿瘤学   783篇
  2024年   4篇
  2023年   48篇
  2022年   171篇
  2021年   288篇
  2020年   125篇
  2019年   149篇
  2018年   235篇
  2017年   161篇
  2016年   279篇
  2015年   427篇
  2014年   427篇
  2013年   502篇
  2012年   810篇
  2011年   716篇
  2010年   426篇
  2009年   365篇
  2008年   454篇
  2007年   392篇
  2006年   354篇
  2005年   391篇
  2004年   313篇
  2003年   238篇
  2002年   191篇
  2001年   130篇
  2000年   115篇
  1999年   93篇
  1998年   85篇
  1997年   95篇
  1996年   80篇
  1995年   71篇
  1994年   50篇
  1993年   50篇
  1992年   28篇
  1991年   43篇
  1990年   33篇
  1989年   57篇
  1988年   48篇
  1987年   41篇
  1986年   25篇
  1985年   28篇
  1984年   15篇
  1983年   8篇
  1982年   16篇
  1981年   22篇
  1980年   20篇
  1979年   14篇
  1978年   6篇
  1977年   14篇
  1976年   12篇
  1975年   8篇
排序方式: 共有8680条查询结果,搜索用时 15 毫秒
71.
A modern malaise   总被引:1,自引:0,他引:1  
JS Robertson Dr   《Public health》1999,113(4):155-156
  相似文献   
72.
73.
Since the completeness of case ascertainment is directly related to the validity of a study, the evaluation of completeness is an essential feature of a cohort study. To estimate the completeness of cancer case ascertainment during a three year period (Jan. 1, 1993, to Dec. 31, 1995) in which the Seoul Male Cohort was followed up, we applied capture-recapture method. Data were obtained from the cancer registries, medical records and death certificates, with cases identified from each source numbering 103, 105, and 38, respectively. After eliminating duplicate cases, the total number was 141, and by using a log-linear model, the number of cases not detected by any of the three data sources was estimated to be 16. For all cancers, the estimated completeness of follow-up was 89.9%.  相似文献   
74.
The methanol extracts of the leaves of Crataegus pinnatifida showed potent inhibitory activities against HIV-1 protease at a concentration of 100 micrograms/ml. The subsequent fractionation and isolation of the extract gave two active compounds. Their structures were identified as uvaol (1) and ursolic acid (2) by spectral data. These active compounds inhibit HIV-1 protease with IC50 values of 5.5 and 8.0 microM, respectively.  相似文献   
75.
Kwon BM  Jung HJ  Lim JH  Kim YS  Kim MK  Kim YK  Bok SH  Bae KH  Lee IR 《Planta medica》1999,65(1):74-76
Fifteen lignans were isolated from the fruits of SCHIZANDRA CHINENSIS, the leaves of MACHILUS THUNBERGII, and the flower buds of MAGNOLIA DENUDATA. They were identified as gomisins, schizandrin, wuweizisu, schizantherin, licarins, and machilin, which inhibited rat liver ACAT with IC (50) values of 25-200 microM. Comisin N is the most potent inhibitor with IC (50) value of 25 microM in these lignans.  相似文献   
76.
When liriodendrin or syringin was incubated for 24 h with human intestinal bacteria, two metabolites, (+)-syringaresinol-beta-D-glucopyranoside and (+)-syringaresinol, from liriodendrin and one metabolite, synapyl alcohol, from syringin were produced. The metabolic time course of liriodendrin was as follows: at early time, liriodendrin was converted to (+)-syringaresinol-beta-D-glucopyranoside, and then (+)-syringaresinol. The in vitro cytotoxicities of these metabolites, (+)-syringaresinol and synapyl alcohol, were superior to those of liriodendrin and syringin.  相似文献   
77.
Two new furanolignans (3, 5), together with three known lignans (1, 2, 4), were isolated from the stem of Lindera obtusiloba (Lauraceae). The structures of the compounds were determined as actifolin (1), pluviatilol (2), 5,6-dihydroxymatairesinol (3), (+)-syringaresinol (4), and (+)-9'-O-trans-feruloyl-5,5'-dimethoxylariciresinol (5) on the basis of physicochemical and spectroscopic evidences. Compounds 1, 2, 3, and 5 showed cytotoxicity against a small panel of human tumor cell lines with ED50 values of 3.40 to approximately 19.27 microg/ml.  相似文献   
78.
Cytotoxicities of four urushiols, congeners isolated from the sap of Korean lacquer tree (Rhus vernicifera Stokes), to 29 human cancer cell lines originated from 9 organs were evaluated. Their values of 50% growth inhibition were below 4 microg/ml, and showed cell line specific cytotoxicity. The present result is the first report on the cytotoxicity of urushiols suggesting that they would have an anticancer activity to human cancer cells.  相似文献   
79.
The prevalence of microalbuminuria was assessed in 50 patients of non-insulin dependent diabetes mellitus. The mean age of patients was 52.1 ± 11.6 years and the duration of diabetes was 8.3 ± 6.8 years. Twenty (40%) patients had microalbuminuria. Microalbuminuria was more common in patients with a longer duration of diabetes (more than 5 years), a poor glycaemic control, and higher systolic blood pressure.KEY WORDS: Microalbuminuria, Diabetes mellitus, Diabetic nephropathy, Chronic renal failure  相似文献   
80.
PURPOSE: To evaluate the potential of the new prognostic information gained by analyzing the coexpression of epidermal growth factor receptor (EGFR) and cyclooxygenase-2 (COX-2) in cervical cancer patients. EXPERIMENTAL DESIGN: Sixty-eight patients with International Federation of Gynecology and Obstetrics stage IIB squamous cell carcinoma of the uterine cervix, who underwent concurrent chemoradiotherapy between 1993 and 1996, were divided into the following four groups according to their immunoreactivities for EGFR and COX-2 in paraffin-embedded sections: (a). the EGFR-negative/COX-2-negative group (n = 11); (b). the EGFR-negative/COX-2-positive group (n = 8); (c). the EGFR-positive/COX-2-negative group (n = 27); and (d). the EGFR-positive/COX-2-positive group (n = 22). The clinical features, patterns of treatment failure, and survival data in the four groups were compared. RESULTS: Positive immunoreactivity for EGFR and COX-2 was observed in 49 of 68 (72%) and 19 of 68 (28%), respectively. However, no strong correlation was found between the levels of EGFR and COX-2 immunopositivity (R(2) = 0.05, P = 0.07). Patients in the EGFR-positive/COX-2-positive group had a higher likelihood of locoregional recurrence than those in the other three groups (P = 0.02). Of the patients in the four groups, patients positive for both oncoproteins were found to have the worst prognosis with an overall 5-year disease-free survival rate of 55% compared with 91% for the EGFR-negative/COX-2-negative patients, 88% for the EGFR-negative/COX-2-positive patients, and 69% for the EGFR-positive/COX-2-negative patients (P = 0.05, log-rank test). In addition, the synchronous coexpression of the EGFR and COX-2 oncoproteins was found to be an independent prognostic factor by univariate and multivariate analyses (relative risk = 4.0, P = 0.03). CONCLUSIONS: Given these observations, we conclude that the coexpression of EGFR and COX-2 immunoreactivity may be used as a potent molecular risk factor for predicting the poor survival of patients with the International Federation of Gynecology and Obstetrics stage IIB squamous cell carcinoma of the uterine cervix.  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