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   19553篇
  免费   1562篇
  国内免费   110篇
耳鼻咽喉   223篇
儿科学   655篇
妇产科学   309篇
基础医学   2442篇
口腔科学   324篇
临床医学   2121篇
内科学   4895篇
皮肤病学   270篇
神经病学   1330篇
特种医学   978篇
外科学   2880篇
综合类   285篇
一般理论   9篇
预防医学   1330篇
眼科学   644篇
药学   1182篇
  1篇
中国医学   51篇
肿瘤学   1296篇
  2023年   84篇
  2022年   114篇
  2021年   292篇
  2020年   192篇
  2019年   365篇
  2018年   382篇
  2017年   314篇
  2016年   323篇
  2015年   360篇
  2014年   529篇
  2013年   801篇
  2012年   1075篇
  2011年   1045篇
  2010年   679篇
  2009年   705篇
  2008年   1085篇
  2007年   1170篇
  2006年   1194篇
  2005年   1122篇
  2004年   1085篇
  2003年   1040篇
  2002年   966篇
  2001年   320篇
  2000年   311篇
  1999年   280篇
  1998年   304篇
  1997年   301篇
  1996年   257篇
  1995年   268篇
  1994年   233篇
  1993年   219篇
  1992年   224篇
  1991年   184篇
  1990年   189篇
  1989年   205篇
  1988年   210篇
  1987年   189篇
  1986年   176篇
  1985年   155篇
  1984年   147篇
  1983年   153篇
  1982年   154篇
  1981年   155篇
  1980年   136篇
  1979年   105篇
  1978年   106篇
  1977年   129篇
  1976年   102篇
  1975年   67篇
  1974年   68篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
1.
2.
ABSTRACT

The lack of stable housing can impair access and continuity of care for patients living with human immunodeficiency virus (HIV). This study investigated the relationship between housing status assessed at multiple time points and several core HIV-related outcomes within the same group of HIV patients experiencing homelessness. Patients with consistently stable housing (CSH) during the year were compared to patients who lacked CSH (non-CSH group). The study outcomes included HIV viral load (VL), CD4 counts, and health care utilization. Multivariable and propensity weighted analyses were used to assess outcomes adjusting for potential group differences. Of 208 patients, 88 (42%) had CSH and 120 (58%) were non-CSH. Patients with CSH had significantly higher proportion of VL suppression and higher mean CD4 counts. The frequency of nurse visits in the CSH group was less than a half of that in the non-CSH group. Patients with CSH were less likely to be admitted to the medical respite facility, and if admitted, their length of stay was about a half of that for the non-CSH group. Our study findings show that patients with CSH had significantly better HIV virologic control and immune status as well as improved health care utilization.  相似文献   
3.
We present a patient with both dynamic left ventricular outflow tract obstruction and valvular aortic stenosis. The aortic valve was calcified, and velocities and gradients measured by continuous‐wave Doppler met standard criteria for severe aortic stenosis. The increased subvalvular velocities invalidated assumptions of the simplified Bernoulli equation; correction using the longer form of the Bernoulli equation suggested a lower but still significant gradient. The complex shape of the subvalvular spectral Doppler envelope indicated supranormal systolic function and dynamic left ventricular outflow obstruction. Left heart catheterization with an end‐hole catheter was required to determine the subvalvular and valvular components of the obstruction.  相似文献   
4.
5.
6.
7.
Birth weight on 12,644 singleton infants from 6,196 sibships born in Maryland between 1980 and 1984 were used to estimate the effects of nine maternal and infant covariates on the sibship correlation in birth weight. Assuming a homogeneous correlation across all families, the estimated intraclass correlation was 0.4664 (+/- 0.0099). This high sibship correlation makes it possible to predict, with reasonable accuracy, the birth weight of a child given information on previous sibs, as well as covariates on the mother and/or infant pertinent to a given pregnancy. The reduction in variance associated with incorporating information on the nine covariates used here was approximately equal to that obtained by conditioning on a single previous sib. Testing for heterogeneity in correlation among different groups of families showed that a crude measure of parity (first live birth vs. other), time between births, mother's marital status, and maternal age at the birth of the last child significantly influenced the sibship correlation in birth weight.  相似文献   
8.
Agenesis of the Gallbladder Revisited Laparoscopically   总被引:1,自引:0,他引:1  
Gallbladder agenesis is an extremely rare disease. Necropsy incidence has been reported to be 0.016%. Failure lo locate the gallbladder at the time of a planned cholecystectomy can be very challenging. We report such a case during a laparoscopic cholecystectomy. The indication for surgery in these patients are complaints of gallbladder symptoms along with a false-positive ultrasound study. During exploration, an abnormal location of the gallbladder has to be excluded. Ectopic gallbladder locations include intrahepatic, lesser omentum, retroperitoneal, retrohepatic, within the falciform ligament, retroduodenal, and retrohepatic areas. Thorough exploration and cholangiography are essential. Embryologically, the gallbladder and cystic duct arise from the caudal portion of the hepatic bud. All of the previously reported cases of gallbladder agenesis have shown an absence of both the gallbladder and cystic duct. We report an embryological oddity wherein a patent cystic duct was found along with an agenetic gallbladder. This is the first case report of this finding, along with this being the first absent gallbladder discovered laparoscopically.  相似文献   
9.
BACKGROUND: Human serum albumin (HAS) is used to treat hypoproteinaemia in neonates and as a volume expander. The aim of this study was to quantify the decrease in serum concentration of ionized magnesium ([Mg2+]) when human serum albumin is added to neonatal serum in vitro. METHODS: Human serum albumin was added to 20 cord serum samples of term infants to reach incremental concentrations of 0 to 20.0 g/l and [Mg2+] were measured. RESULTS: Serum [Mg2+] decreased significantly with the addition of serum albumin. At incremental serum albumin concentration of 10 to 20 g/l, which is within the range of the desired aim in the treatment of hypoalbuminaemia, the magnitude of the decrease in serum [Mg2+] was approximately 0.041 to 0.052 mmol/l (10 to 13 per cent) from the average baseline value. CONCLUSION: The addition of albumin causes a decrease in [Mg2+]. From this in vitro study we speculate that fast infusion of albumin in human neonates may potentially cause a clinically significant decrease in serum [Mg2+].  相似文献   
10.
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