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   36234篇
  免费   2059篇
  国内免费   106篇
耳鼻咽喉   440篇
儿科学   2146篇
妇产科学   716篇
基础医学   4635篇
口腔科学   820篇
临床医学   2539篇
内科学   7392篇
皮肤病学   851篇
神经病学   1935篇
特种医学   814篇
外科学   4987篇
综合类   1333篇
一般理论   15篇
预防医学   2129篇
眼科学   1537篇
药学   3567篇
中国医学   277篇
肿瘤学   2266篇
  2023年   217篇
  2022年   528篇
  2021年   1198篇
  2020年   664篇
  2019年   868篇
  2018年   1070篇
  2017年   741篇
  2016年   975篇
  2015年   1009篇
  2014年   1373篇
  2013年   1787篇
  2012年   2464篇
  2011年   2480篇
  2010年   1402篇
  2009年   1258篇
  2008年   1804篇
  2007年   1767篇
  2006年   1800篇
  2005年   1413篇
  2004年   1404篇
  2003年   1207篇
  2002年   1031篇
  2001年   825篇
  2000年   869篇
  1999年   733篇
  1998年   310篇
  1997年   216篇
  1996年   225篇
  1995年   219篇
  1994年   177篇
  1993年   154篇
  1992年   500篇
  1991年   405篇
  1990年   430篇
  1989年   395篇
  1988年   358篇
  1987年   356篇
  1986年   348篇
  1985年   323篇
  1984年   262篇
  1983年   220篇
  1979年   230篇
  1978年   148篇
  1977年   180篇
  1976年   139篇
  1975年   171篇
  1974年   182篇
  1973年   183篇
  1972年   173篇
  1971年   161篇
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
101.
102.
103.
A prospective randomized controlled study was designed to evaluate differences in efficacy and complication rate between the two most commonly used sclerosing agents, sodium tetradecyl sulfate (STD) and polidocanol. Of 52 patients with esophageal variceal bleeding, 26 were randomized to receive sclerotherapy with 1.5% STD and 26 to receive 1% polidocanol at weekly intervals. Eradication of varices was achieved in 88% patients each of the STD and polidocanol group. There was no significant difference between patients injected with STD and polidocanol with regard to re-bleeding (27% vs. 15%) and mortality (11.5% in both). The use of STD, in contrast to polidocanol, was associated with a higher incidence of complications in terms of severe retrosternal pain (27% vs. 4%), deep ulceration (53% vs. 23%), dysphagia (88% vs. 46%), and stricture formation (27% vs. 8%). It was concluded that these two agents were similar in efficacy. However, polidocanol was superior due to a lower incidence of complications.  相似文献   
104.
Standardization of allergens are achieved by in vitro and in vivo methods. Some of the allergens from Western countries are standardized using biological potency of the extracts but no attempt has been made till now to standardize any of the pollen extracts from India based on biological units. Therefore, we have attempted to standardize two important pollen allergens Ricinus communis and Holoptelea integrifolia by biological methods. Broadly the methods adopted by Dreborg and Grimmer (1983) was followed. Skin prick tests were carried out with the extracts of R. communis and H. integrifolia on 15 allergic patients in five three fold log dilutions starting with 1:10, in 50% glycerinated buffer. Glycerinated buffer (50%) and histamine dihydrochloride (1 mg/ml) were used as negative and positive controls, respectively. The mean wheal diameter obtained with different concentrations showed a gradual systematic fall with increase in dilution. The mean relative diameter (% of histamine reaction) varied from 124.1 +/- 8.9 to 33.7 +/- 6.1 and 78.9 +/- 5.5 to 21.4 +/- 3.8 with the highest and lowest concentrations of R. communis and H. integrifolia pollen antigens, respectively. The histamine equivalent concentration of antigen 1,000 Biological Units (BU) obtained for crude pollen extracts of R. communis and H. integrifolia was 1:17 and 1:22 respectively.  相似文献   
105.
Five new N alpha-(5,8-dideazapteroyl)-L-ornithines have been prepared using multistep synthetic sequences. These include N alpha-[5-(trifluoromethyl)-5,8-dideazapteroyl]-L-ornithine, 3, as well as N alpha-[5-(trifluoromethyl)-5,8-dideazaisopteroyl]-L-ornithine, 4, and its 5-fluoro and 5-chloro analogues. Both of the compounds containing a 5-(trifluoromethyl) group (3 and 4) were found to be excellent inhibitors of homogeneous hog liver folylpolyglutamate synthetase, having Ki values in the same range as N alpha-(5-chloro-5,8-dideazapteroyl)-L-ornithine, 2, (approximately 10 nM). However, the bridge-reversed isomer of 2 was 60-fold less inhibitory than 2.  相似文献   
106.
BACKGROUND: Allergen extracts are unstable, heat labile or susceptible to proteases. Stability of allergen extracts is important for proper diagnosis and therapy of allergic disorders. OBJECTIVE: The present study was undertaken to determine the preservation and stabilization conditions of Imperata cylindrica (Ic) grass pollen extract. METHODS: The Ic extract was kept with 0.1 mepsilon-aminocaproic acid (EACA), 0.75 m sucrose, 5% glycerol, 0.03% human serum albumin (HSA) or 0.4% phenol for different time periods. The extracts were stored for 3, 6 and 12 months each at 4 degrees C, 4 degrees C with daily exposure to room temperature (RT) for 1 h, and RT. The quality of extracts was analysed by SDS-PAGE, Western blot, ELISA, ELISA inhibition and skin test. RESULTS: Extracts kept with EACA and sucrose retained most of the protein bands followed by glycerol as determined by SDS-PAGE and Western blot during all storage periods and conditions in comparison with standard extracts. The extracts kept with HSA, phenol and without preservative (WP) showed protein degradation below 33 kDa after 3 months storage at all conditions. However, a 67-kDa allergen was stable in these extracts. EACA extract required 75 to 120 ng of protein for 50% inhibition in IgE binding under different conditions, whereas standard extract required 70 ng for the same. ELISA also demonstrated high allergenic reactivity of EACA extract. ID test on allergy patients with EACA extract demonstrated same allergenic potency as that of standard extract. CONCLUSION: EACA is the best preservative/stabilizing agent of Ic pollen extract, followed by sucrose and glycerol. Ic extract kept with phenol, HSA and without preservative showed degradation within 3 months. EACA preserved extract is equally potent as that of standard extract up to 1 year's storage.  相似文献   
107.
Syntheses and relative cadmium mobilizing properties are described for three new monoaralkyl esters (HOOCCH(SH)CH(SH)COOR, where R = phenylethyl ((CH2)2C6H5), MPhEDMS; R = 3-phenylpropyl ((CH2)3C6H5), MPhPDMS; and R = 2-phenoxyethyl ((CH2)2OC6H5), MPhOEDMS) of meso-2,3-dimercaptusuccinic acid. These were prepared by the reaction of the corresponding alcohol with meso-2,3-dimercaptosuccinic acid (DMSA) in aqueous HCl. When administered intraperitoneally to cadmium-loaded mice at 0.50 mmol/kg/day for four consecutive days, all induced significant reductions in the whole body cadmium levels. MPhEDMS, 60%; MPhPDMS, 66%; and MPhOEDMS, 58% in comparison with control levels. At the same dosage monoisoamyl meso-2,3-dimercaptosuccinate (Mi-ADMS) and a dithiocarbamate, sodium N-benzyl-4-O-(β-D-galactopyranosyl)-d -glucamine-N-carbodithioate (BLDTC) induced reductions of 65% and 57%, respectively. Hepatic and renal cadmium were also depleted significantly, while brain cadmium levels were unchanged. These compounds induced a significant reduction in the cadmium levels of the spleen, and one, MPhOEDMS, produced a 10% decrease in pancreatic cadmium. The manner in which the later injections removed smaller fractions of the total body cadmium is consistent with a bodily distribution of these compounds by which they are concentrated primarily in the kidneys and the liver, with much smaller amounts reaching other organs. It is proposed that these compounds enter renal and hepatic cells through an anion transport system.  相似文献   
108.
109.
110.
The pattern of gastro-intestinal (GIT) and Respiratory tract (RTI) diseases in rural areas of the Varanasi district, U.P. (India) was studied from the outpatient (OPD) attendance between July 1985 to June 1986. Out of a total of new patients, 19.71% had respiratory diseases in contrast to 27.9% with GIT disease. A decreasing trend was observed in attendance rates as age advanced. The difference in age distribution of males and females was statistically significant. The attendance rates for GIT diseases were higher in female (29.16%) than in males (25.16%) whereas in RTI, the rates were higher in males (19.39%) than in females (18.77%). The attendance rate was found to be higher in rainy season (23.59%) followed by summer (14.50%). Diarrhoea (15.44%) and upper (URTI) respiratory tract infection (19.93%) occupied the major recorded episodes.  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