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   1395260篇
  免费   104548篇
  国内免费   4405篇
耳鼻咽喉   17722篇
儿科学   45218篇
妇产科学   38186篇
基础医学   206504篇
口腔科学   37673篇
临床医学   133392篇
内科学   271868篇
皮肤病学   28238篇
神经病学   116927篇
特种医学   49550篇
外国民族医学   368篇
外科学   191379篇
综合类   29051篇
现状与发展   1篇
一般理论   479篇
预防医学   121216篇
眼科学   30512篇
药学   103816篇
  6篇
中国医学   3349篇
肿瘤学   78758篇
  2021年   11892篇
  2019年   12840篇
  2018年   18447篇
  2017年   13572篇
  2016年   14492篇
  2015年   16639篇
  2014年   22313篇
  2013年   34523篇
  2012年   48505篇
  2011年   51104篇
  2010年   29266篇
  2009年   26460篇
  2008年   46176篇
  2007年   48697篇
  2006年   48695篇
  2005年   47110篇
  2004年   44794篇
  2003年   42477篇
  2002年   41130篇
  2001年   62531篇
  2000年   64183篇
  1999年   53699篇
  1998年   14867篇
  1997年   13434篇
  1996年   13297篇
  1995年   12604篇
  1994年   11743篇
  1993年   11025篇
  1992年   42310篇
  1991年   41451篇
  1990年   40066篇
  1989年   37945篇
  1988年   35129篇
  1987年   34244篇
  1986年   32674篇
  1985年   31139篇
  1984年   23415篇
  1983年   19903篇
  1982年   11891篇
  1979年   21215篇
  1978年   15064篇
  1977年   12267篇
  1976年   12098篇
  1975年   12369篇
  1974年   15192篇
  1973年   14837篇
  1972年   13662篇
  1971年   12698篇
  1970年   11803篇
  1969年   10718篇
排序方式: 共有10000条查询结果,搜索用时 508 毫秒
851.
BACKGROUND: Gastric cancer (GC) is the leading cause of cancer deaths in China. Our study prospectively evaluated the impact of repeated endoscopic screens on GC mortality in a high-risk population in China. METHODS: Between 1989 and 1999, a population-based gastroscopic screening was conducted in 4,394 residents of Linqu County, China, a region with the highest rates of GC worldwide. Residents ages 35 to 64 years received initial gastroscopies with biopsies in 1989. Repeated endoscopies were performed in 1994 and 1999. Cancer occurrences and deaths were actively monitored throughout the entire period until July 2000. Mortality from GC was compared with expected values based on mortality rates obtained for Linqu in the 1990-1992 Chinese Cancer Mortality Survey. RESULTS: Between March 1989 and July 2000, 39,303 person-years were accumulated; 85 new GCs occurred, 29 (34.5%) were in early stage. Fifty-eight cases (68%) were identified at one of the screens. The number of observed deaths from GC (37) was close to the expected (36.8). The standardized mortality ratio was 1.01 (95% CI 0.72-1.37) for the entire cohort, 1.13 (95% CI 0.77-1.57) for males, and 0.65 (95% CI 0.26-1.32) for females. CONCLUSIONS: Despite high population coverage with repeated screens, no reduction in GC mortality was observed in this high-risk population in China.  相似文献   
852.
Molecular chaperones assist in the biosynthesis and processing of proteins. Most chaperones are induced by physiological stresses. We have shown that dietary energy restriction decreases the mRNA and protein levels of many endoplasmic reticulum chaperones in the livers of mice. Here, we have investigated the response of chaperone mRNA to feeding. Control and 50% energy-restricted C3B10RF1 mice were deprived of food for 24 h, fed, and killed 0, 1.5, 5 or 12 h after feeding. Chaperone mRNAs were strongly induced as early as 1.5 h after feeding in control and energy-restricted mice. The integrated levels of these mRNA over 24 h were significantly lower in energy-restricted mice. The mRNA response to energy intake was mirrored over the course of days in the level of chaperone protein. A similar but smaller response to feeding was found in kidney and muscle. Puromycin and cycloheximide failed to inhibit the feeding response, suggesting that feeding releases chaperone expression from an unstable inhibitor. Studies with dibutyryl-cAMP- and glucagon-supplemented, normal and streptozotocin-diabetic mice suggest that glucagon and insulin may be mediators of the feeding response. Adrenalectomy enhanced the feeding induction, but dexamethasone administration had no effect. Thus, postprandial changes in insulin and glucagon may link chaperone gene expression to feeding, possibly in several tissues including liver.  相似文献   
853.
A consecutive series of patients (1978–1981) comprising all patients with acute leukaemia from a population of 475000 inhabitants was reviewed. Thus, 94 patients were diagnosed as having acute leukaemia. No patients were lost from follow-up. The incidence figures of ALL and AML differed significantly from those of Sweden as a whole. 9 patients were < 15 years old. The median age of adult patients was 64 years, 60.8% being ≥ 60 years old. Of adult patients with AML, 20% had a preleukaemic history (chronic myeloproliferative disorders, myelodysplastic syndromes and others). None of 6 patients with leukaemia as a metamorphosis of a chronic myeloproliferative disorder achieved a complete remission. The overall remission rate of the remaining adult patients was 25%. Treated patients, 15–39 years old, with AML without any preleukaemic history, had a complete remission rate of 80% compared to 12% for patients ≥ 60 years old with the same diagnosis. Of 60 patients with ‘primary’ AML, 14 were not treated, mainly because of advanced age and complicating diseases. Most of these patients died within a week of admission.  相似文献   
854.
The effect of unilateral ureteral occlusion on fibrin deposition in the kidney and the interrelation of the fibrin deposition and the renal blood flow was studied in rat. Intravascular coagulation in the kidney was induced by infusion of thrombin and inhibition of fibrinolysis with tranexamic acid. The effects unilateral occlusion of the ureter for 1 and 24 h on fibrin deposition and renal blood flow were studied. Fibrin in the kidneys was quantitated by intravenous injection of 125I-labelled fibrinogen 24 h before the experiment. The renal blood flow was measured before and after infusion of thrombin by injection of 85Sr- and 141Ce-labelled microspheres into the left ventricle. After ureteral occlusion for 1 h the deposition of fibrin in the kidneys was unaffected. After 24 h substantially less fibrin deposition was found in the occluded than in the unoccluded kidney (0.3 +/- 0.2 and 5.7 +/- 1.6 mg, respectively; p less than 0.05). Before thrombin infusion the blood flow to the occluded kidney was less than that in the unoccluded kidney (2.1 +/- 0.8 and 3.7 +/- 1.2 ml/min, 100 g body weight, respectively; p less than 0.05). The blood flow after infusion of thrombin was equally reduced in both kidneys. The results contradict the hypothesis that vasoconstriction increases the amount of fibrin in the kidneys in thrombin-induced intravascular coagulation.  相似文献   
855.
Three cases of enteritis necroticans seen at Port Moresby General Hospital are described. All three cases proved diagnostic problems and in all three the diagnosis was made only at laparotomy. While the condition is uncommon in Port Moresby, these cases indicate that it must now be considered earlier rather than later.  相似文献   
856.
A 19 years old, male patient presented with symptoms of smoky urine for 2 weeks, puffiness of face and diminished urine output for 3 weeks associated with occasional lower abdominal and flank pain. Patient's history, clinical findings and available investigations were strongly suggestive of Idiopathic Rapidly Progressive Glomerulonephritis. The patient showed excellent response to glucocorticoid and cytotoxic agent.  相似文献   
857.
A rare case of an advanced primary broad ligament carcinoma is discussed, with a review of the literature regarding its incidence, presentation and management. This patient showed a complete response to adjuvant cisplatin-based chemotherapy following panhysterectomy and is presently without any evidence of disease, 15 months after completion of her treatment.  相似文献   
858.
Nineteen N-acyl-5-bromanthranilic acid amides were synthesized via acylation of 5-bromanthranilamide with suitable anhydrides. The antimicrobial activity of the synthesized compounds with respect to Staphylococcus aureus and Escherichia coli was evaluated. Compounds with diphenyl, furoyl, and tetrachlorophthalyl moieties in the acyl part of the molecule showed significant inhibition of microbial growth. The minimum inhibiting concentrations of this compounds were 15.6 μg/ml against S. aureus and 15.6 – 31 μg/ml against E. coli. Other tested amides were considerably less active.__________Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 39, No. 1, pp. 17 – 18, January, 2005.  相似文献   
859.
Physicians have long been wary of chronically administering neuroleptic drugs to the demented elderly for fear of significant side effects. In this article, the authors present evidence to support these fears. A discussion of the early and late emerging side effects of neuroleptic drugs is presented.  相似文献   
860.
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