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   191599篇
  免费   11012篇
  国内免费   490篇
耳鼻咽喉   2485篇
儿科学   6158篇
妇产科学   3968篇
基础医学   25800篇
口腔科学   8151篇
临床医学   13977篇
内科学   43691篇
皮肤病学   4803篇
神经病学   16101篇
特种医学   5785篇
外国民族医学   26篇
外科学   23891篇
综合类   1515篇
现状与发展   1篇
一般理论   68篇
预防医学   19246篇
眼科学   3844篇
药学   11391篇
中国医学   761篇
肿瘤学   11439篇
  2023年   1028篇
  2022年   2220篇
  2021年   4263篇
  2020年   2776篇
  2019年   3971篇
  2018年   5500篇
  2017年   4042篇
  2016年   3827篇
  2015年   4524篇
  2014年   6116篇
  2013年   7796篇
  2012年   12154篇
  2011年   12755篇
  2010年   6513篇
  2009年   5883篇
  2008年   9982篇
  2007年   10619篇
  2006年   9942篇
  2005年   10098篇
  2004年   9383篇
  2003年   8686篇
  2002年   6673篇
  2001年   5242篇
  2000年   5248篇
  1999年   4627篇
  1998年   1717篇
  1997年   1423篇
  1996年   1418篇
  1995年   1213篇
  1994年   1205篇
  1993年   1071篇
  1992年   2774篇
  1991年   2680篇
  1990年   2430篇
  1989年   2420篇
  1988年   2183篇
  1987年   2043篇
  1986年   1906篇
  1985年   1818篇
  1984年   1324篇
  1983年   1066篇
  1982年   613篇
  1981年   573篇
  1980年   521篇
  1979年   965篇
  1978年   646篇
  1977年   517篇
  1975年   568篇
  1974年   564篇
  1973年   573篇
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
41.
42.
43.
We review the association between surgically resolvable aortic disease and horseshoe kidney with a discussion of diagnostic problems and therapeutic options.Male patient 81 years of age with horseshoe kidney and an abdominal aortic aneurysm that was discovered by chance in an abdominal ultrasound during a check-up for his prostate condition.A retroperitoneal approach was used in order to resect the aneurysm and perform an aorto-aortic bypass with no complications occurring. Two years after the diagnosis, the patient is still asymptomatic from a vascular point of view.The co-presence of horseshoe kidney and aortic disease needing surgical correction is infrequent, but it significantly increases the technical complexity of aortic reconstruction. A literature review is included.  相似文献   
44.
OBJECTIVE.--To determine behavioral and demographic risk factors for human immunodeficiency virus (HIV) infection in central Africa. DESIGN.--Cross-sectional survey. SETTING.--Kigali, Rwanda. PARTICIPANTS.--A representative sample of 1458 childbearing women aged 19 to 37 years who were recruited from outpatient prenatal and pediatric clinics at the only community hospital in the city. MAIN OUTCOME MEASURE.--Antibodies to HIV assessed by enzyme immunoassay and confirmed by Western blot or indirect immunofluorescence. RESULTS.--The HIV seroprevalence was 32% overall. Infection rates were higher in women who were single, in those in steady relationships that began after 1981, and in the 33% of women reporting more than one lifetime sexual partner. Women in legal marriages or monogamous partnerships had lower rates of infection, but even low-risk women had prevalences on the order of 20%. History of venereal disease in the past 5 years, although the strongest risk factor in a multiple logistic analysis (odds ratio, 2.7; 95% confidence interval, 2.0 to 3.7), was reported by only 30% of those infected. Having a male sexual partner who drank alcohol or who had higher income were significant risk factors for HIV infection in the multivariate analysis, but use of oral contraceptives and having an uncircumcised partner were not. CONCLUSIONS.--The epidemic of the acquired immunodeficiency syndrome in Rwanda has spread beyond high-risk groups to the general population of women without known risk factors. For most of these women, a steady male partner is the source of their HIV risk and therefore a vital target for intervention efforts.  相似文献   
45.
46.
47.
The aim of the present study was to probe the structural integrity of insulin after being entrapped into chitosan/alginate nanoparticles produced by ionotropic polyelectrolyte pre-gelation. By manipulating the alginate:chitosan mass ratio and the pH during nanoparticle production, desired nanoparticles with a mean size of 850 (+/-88)nm and insulin association efficiency of 81 (+/-2)% were obtained. Insulin secondary structure was assessed by Fourier transform infrared (FTIR) and circular dichroism (CD) after entrapment into nanoparticles and after release from the particles under gastrointestinal simulated conditions. FTIR second-derivative spectra and area-overlap compared to an insulin standard confirmed that no significant conformational changes of insulin occurred in terms of alpha-helix and beta-sheet content. Far-UV-CD spectra corroborated the preservation of insulin structure during the nanoparticle production procedure. The presented nanoparticulate system is a promising carrier for insulin oral delivery since it preserves insulin structure and therefore also, potentially, its bioactivity.  相似文献   
48.
BACKGROUND: Exposure to a high level of house dust mite allergens (HDMAs) is considered as a risk factor for HDM sensitization and development of asthma in genetically disposed people. Mattresses are one of the most important sources of HDMA in people's living environment. OBJECTIVE: The aim of this study was to evaluate the association between mattress characteristics and HDMA concentrations on mattresses. METHODS: Dust samples of mattress surfaces were taken to evaluate the level of Der p 1 allergen. All participants filled in a questionnaire about the type of mattress, the type of covering (upper layer) of the mattress, dwelling characteristics and cleaning habits. Humidity and temperature of the bedroom were measured at the time of dust sampling. RESULTS: One hundred and sixty-eight questionnaires were filled in. Synthetic upper layer of the mattress was associated with a higher level of Der p 1 compared with cotton upper layer (2.6 vs. 0.8 microg/g Der p 1). Moreover, higher relative humidity (RH) was associated with significant higher concentrations and density of Der p 1. CONCLUSIONS: Two factors were associated with lower levels of Der p 1 found on mattresses, namely: a cotton upper layer of the mattress compared with a layer of synthetic material and lower RH at the time of sampling. As far as we know, the association between type of upper layer and concentration of Der p 1 has not been described before and could lead to the formulation of practical advices in order to reduce HDMA concentrations on mattresses.  相似文献   
49.
Plasma pyridoxal-5'-phosphate and pyridoxal levels increased significantly (p less than 0.05) when single, oral bolus doses of pyridoxine were increased from 10 to 25 and from 25 to 50 mg in nine female volunteers. However, when the dose was increased to 100 mg, plasma pyridoxal-5'-phosphate levels did not differ significantly from those recorded after the 50 mg dose. Within 3 h plasma pyridoxal levels rose with a factor of 3.85 compared with the 50 mg dose but high pyridoxal levels were eliminated from the circulation. Renal clearance of pyridoxal remained a constant, low percentage (less than 2.0%) of each pyridoxine supplement in spite of the observed very high circulating pyridoxal levels. Pyridoxine supplementation is discussed in relation to circulating pyridoxal-5'-phosphate and pyridoxal availability for cellular metabolism.  相似文献   
50.
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