全文获取类型
收费全文 | 36512篇 |
免费 | 2074篇 |
国内免费 | 108篇 |
专业分类
耳鼻咽喉 | 445篇 |
儿科学 | 2173篇 |
妇产科学 | 757篇 |
基础医学 | 4686篇 |
口腔科学 | 846篇 |
临床医学 | 2562篇 |
内科学 | 7415篇 |
皮肤病学 | 851篇 |
神经病学 | 1920篇 |
特种医学 | 817篇 |
外科学 | 5027篇 |
综合类 | 1330篇 |
一般理论 | 15篇 |
预防医学 | 2145篇 |
眼科学 | 1563篇 |
药学 | 3565篇 |
中国医学 | 277篇 |
肿瘤学 | 2300篇 |
出版年
2023年 | 220篇 |
2022年 | 531篇 |
2021年 | 1203篇 |
2020年 | 654篇 |
2019年 | 894篇 |
2018年 | 1083篇 |
2017年 | 740篇 |
2016年 | 995篇 |
2015年 | 1028篇 |
2014年 | 1393篇 |
2013年 | 1791篇 |
2012年 | 2489篇 |
2011年 | 2510篇 |
2010年 | 1422篇 |
2009年 | 1266篇 |
2008年 | 1835篇 |
2007年 | 1799篇 |
2006年 | 1814篇 |
2005年 | 1423篇 |
2004年 | 1426篇 |
2003年 | 1219篇 |
2002年 | 1032篇 |
2001年 | 825篇 |
2000年 | 869篇 |
1999年 | 733篇 |
1998年 | 314篇 |
1997年 | 214篇 |
1996年 | 223篇 |
1995年 | 217篇 |
1994年 | 177篇 |
1993年 | 150篇 |
1992年 | 499篇 |
1991年 | 404篇 |
1990年 | 430篇 |
1989年 | 395篇 |
1988年 | 357篇 |
1987年 | 356篇 |
1986年 | 348篇 |
1985年 | 323篇 |
1984年 | 262篇 |
1983年 | 219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 | 182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 113 毫秒
101.
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
102.
K. M. Bijli† B. P. Singh S. Sridhara S. N. Gaur‡ N. Arora 《Clinical and experimental allergy》2003,33(1):65-71
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
103.
Mark M. Jones Pramod K. Singh Mark A. Basinger Glen R. Gale Alayne B. Smith 《Basic & clinical pharmacology & toxicology》1994,74(2):76-83
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
104.
105.
BACKGROUND: A common problem facing patients suffering from psoriasis is the need for surgery that requires incision through active psoriatic skin. Many patients have been denied surgery because of the fear of an increased risk of infection, decreased wound healing ability, and worsening of the psoriatic lesions. OBJECTIVE: To assess the practices and beliefs of dermatologists and surgeons (orthopedic and plastic surgeons) faced with the decision of whether to operate through active psoriatic skin. METHODS: Dermatologists, orthopedic surgeons, and plastic surgeons selected from various professional membership lists from five representative cities were sent a survey to ascertain their opinions on operating on active psoriatic skin. Psoriatic patients were also given forms asking about the severity of their psoriasis and whether they had ever been denied surgery. RESULTS: Dermatologists are more likely to condone surgery in active psoriatic skin and to believe that there is not a risk of increased infection or decreased wound healing than are orthopedic surgeons and plastic surgeons. These findings are statistically significant (P<0.05). CONCLUSION: With proper preoperative measures and dermatologic treatment, surgery can be performed on active psoriatic skin in most cases with minimal reservations, although a controlled, prospective study is necessary to arrive at a definitive conclusion. 相似文献
106.
107.
S. C. Mohapatra P. Mohapatra I. J. Singh S. D. Gaur 《European journal of epidemiology》1989,5(1):117-122
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
108.
109.
110.
Estimation of plasma cortisol by fluorometric technique desorbed by Mallingly's was carried out in 56 cases, including 38 cases of myopia (19 cases of simple myopia and 19 cases of degenerative myopia) and 18 normal individuals. Urinary 17-keto steroids/24 hours was also estimated by Zimmermann technique in 12 out of the 56 cases, which include 8 cases of myopia (4 cases of simple myopia and 4 cases of degenerative myopia) and 4 normal individuals as control. Plasma cortisol level is lower in simple and degenerative myopia than in normal subjects, but on statistical analysis the difference was not of much significance. Patients with simple myopia with positive family history showed lower value of plasma cortisol than patients with simple myopia with negative family history, the difference was also statistically insignificant (P-0.1). In degenerative myopia patients, with and without family history, there was very little difference in plasma cortisol level and statistically highly insignificant (P-0.8). Urinary 17 keto steroid/24 hour values are lower in simple and degenerative myopia than in normal subjects. 相似文献