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   54024篇
  免费   5139篇
  国内免费   361篇
耳鼻咽喉   675篇
儿科学   1413篇
妇产科学   1342篇
基础医学   7168篇
口腔科学   1365篇
临床医学   6596篇
内科学   8835篇
皮肤病学   686篇
神经病学   3893篇
特种医学   2202篇
外国民族医学   1篇
外科学   6708篇
综合类   2819篇
现状与发展   1篇
一般理论   23篇
预防医学   6085篇
眼科学   1178篇
药学   4568篇
  15篇
中国医学   796篇
肿瘤学   3155篇
  2022年   480篇
  2021年   913篇
  2020年   610篇
  2019年   760篇
  2018年   859篇
  2017年   821篇
  2016年   746篇
  2015年   1001篇
  2014年   1299篇
  2013年   1969篇
  2012年   2888篇
  2011年   2917篇
  2010年   1812篇
  2009年   1578篇
  2008年   2402篇
  2007年   2504篇
  2006年   2454篇
  2005年   2383篇
  2004年   2069篇
  2003年   1834篇
  2002年   1820篇
  2001年   1710篇
  2000年   1800篇
  1999年   1473篇
  1998年   633篇
  1997年   500篇
  1996年   507篇
  1995年   525篇
  1994年   442篇
  1993年   451篇
  1992年   1258篇
  1991年   1170篇
  1990年   1147篇
  1989年   1066篇
  1988年   988篇
  1987年   991篇
  1986年   913篇
  1985年   913篇
  1984年   710篇
  1983年   623篇
  1982年   440篇
  1980年   400篇
  1979年   657篇
  1978年   520篇
  1977年   409篇
  1976年   399篇
  1974年   451篇
  1973年   438篇
  1972年   450篇
  1971年   423篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
21.
Measurement of P-selectin on activated platelets as a means of measuring platelet function utilizing the technology described here has the advantage of not requiring immediate access to specialist equipment and expertise. Blood samples are activated, fixed, stored, and transported to a central laboratory for flow cytometric analysis. Here we have compared P-selectin with other more traditional approaches to measuring platelet function in blood and/or platelet-rich plasma (PRP) from patients with acute coronary syndromes on treatment for at least 1 month with either aspirin and clopidogrel or aspirin with prasugrel. The comparators were light transmission aggregometry (LTA), VerifyNow and Multiplate aggregometry (for determining the effects of aspirin) and LTA, VerifyNow and Multiplate together with the BioCytex VASP phosphorylation assay (for the P2Y12 antagonists). The P-selectin Aspirin Test revealed substantial inhibition of platelet function in all but three of 96 patients receiving aspirin with clopidogrel and in none of 51 patients receiving aspirin and prasugrel. The results were very similar to those obtained using LTA. There was only one patient with high residual platelet aggregation and low P-selectin expression. The same patients identified as “non-responders” to aspirin also presented with the highest residual platelet activity as measured using the VerifyNow system, although not quite as well separated from the other values. With the Multiplate test only one of these patients clearly stood out from the others. The results obtained using the P-selectin P2Y12 Test in 102 patients taking aspirin and clopidogrel were similar to the more traditional approaches in that a wide scatter of results was obtained. Generally, high values seen with the P-selectin P2Y12 Test were also high with the LTA, VerifyNow, Multiplate, and BioCytex VASP P2Y12 Tests. Similarly, low residual platelet function using the P2Y12 test was seen irrespective of the testing procedure used. However, there were differences in some patients. Prasugrel was always more effective than clopidogrel in inhibiting platelet function with none of 56 patients (P-selectin and VerifyNow), only 2 of 56 patients (Multiplate) and only 3 of 56 patients (Biocytex VASP) demonstrating high on-treatment residual platelet reactivity (HRPR) defined using previously published cut-off values. The exception was LTA where there were 11 of 56 patients with HRPR. It remains to be seen which experimental approach provides the most useful information regarding outcomes after adjusting therapies in treated patients.  相似文献   
22.
23.
24.
25.
26.
27.
In cystic fibrosis (CF), perturbations of total daily energy expenditure (TDEE) may be a major determinant of altered nutrition and growth. Measurement of TDEE is problematic, though the flex-heart rate method (FHRM) provides a close estimation of TDEE, as compared to the cost-prohibitive, gold standard, the double-labeled water method, and permits estimates of the energy cost of daily activities (ECA) above resting energy expenditure (REE). We hypothesize that alterations in ECA affects TDEE in CF. PURPOSE: To measure components of TDEE in adolescents with CF and normal lung function compared with controls, and to determine whether ECA can be improved by diet and exercise. METHODS: Clinically stable CF subjects (aged 9-13, n=12) and age- and gender-matched controls (n=13) had repeated measurements of TDEE by FHRM, REE, and maximal cardiopulmonary exercise testing (CPET) during a 6-week exercise and diet program. RESULTS: While the mean REE was similar in both groups, ECA was significantly lower in CF adolescents as compared to controls (p=0.02). During CPET, maximal exercise in CF was characterized by hyperventilation, which was unrelated to ventilation-perfusion mismatching. There were no changes in REE after dietary intervention. CONCLUSION: ECA in CF adolescents with normal lung function is lower when compared to healthy controls. These findings support the hypothesis that clinically stable patients with CF have inefficient energy metabolism or alternatively conserve energy during activities of daily living.  相似文献   
28.
29.
选用菜心作为富硒的研究对象,采用不同质量浓度的亚硒酸钠进行喷施处理,测定总硒和有机硒的含量以及不同的富硒浓度对菜心植株产量和各营养成分的影响。结果显示:喷施低浓度硒可以增进菜心品质而高浓度硒则抑制了菜心植株的正常生长和生理代谢。在富硒菜心中,75%以上的硒以有机硒的形式存在,体内的无机硒主要以6价硒存在,6价硒占总无机硒的94%以上;硒可以明显的提高菜心叶绿素、蛋白质、维生素C和氨基酸的含量,但可溶糖的含量降低。  相似文献   
30.
BACKGROUND: Preoperative dietary counseling (PDC) before bariatric surgery is mandated by a growing number of insurance payers. Their claim is that PDC improves outcomes and postoperative compliance. We compared outcomes of GBP patients undergoing a mandatory 13 weeks of PDC (n = 72) to a contemporaneous group of patients with no such requirement (no-PDC; n = 252) who underwent operation between January 2000 and December 2002. METHODS: The PDC and no-PDC groups were characterized by similar male:female ratios (1:4 vs 1:4.6), mean age (42 years), mean body weight (324 lb vs 309 lb), and mean body mass index (BMI) (52 kg/m2 vs 50 kg/m2). The PDC group had a higher incidence of obstructive sleep apnea compared with the no-PDC group (41% vs 28%; P < .04) but otherwise the two groups had similar incidences of obesity-related comorbidities. The presurgery dropout rate was 50% higher in the PDC group than in the no-PDC group (28% vs 19%; P < .05). RESULTS: At 1 year follow-up, the no-PDC patients had a statistically greater percentage excess weight loss (67% vs 60%; P < .0001), lower BMI (32 vs 35; P < .015), and lower body weight (197 vs 218; P < .01). Resolution of major comorbidities, complication rates, 30-day postoperative mortality, and postoperative compliance with follow-up were similar in the two groups. CONCLUSIONS: The data demonstrate that insurance-mandated PDC is an obstacle to patient access for surgical treatment of severe obesity and has no impact on weight loss outcome or postsurgical compliance. PDC should be abandoned by the insurance industry.  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