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   379488篇
  免费   24183篇
  国内免费   2808篇
耳鼻咽喉   5195篇
儿科学   8218篇
妇产科学   10113篇
基础医学   53162篇
口腔科学   11776篇
临床医学   30115篇
内科学   78286篇
皮肤病学   8550篇
神经病学   27284篇
特种医学   13921篇
外国民族医学   82篇
外科学   60608篇
综合类   9957篇
现状与发展   1篇
一般理论   64篇
预防医学   17457篇
眼科学   9526篇
药学   31013篇
  1篇
中国医学   2207篇
肿瘤学   28943篇
  2021年   2619篇
  2019年   2726篇
  2018年   4517篇
  2017年   3438篇
  2016年   3521篇
  2015年   4018篇
  2014年   5694篇
  2013年   7394篇
  2012年   10024篇
  2011年   10218篇
  2010年   6206篇
  2009年   5851篇
  2008年   9457篇
  2007年   10302篇
  2006年   10222篇
  2005年   9286篇
  2004年   8796篇
  2003年   8535篇
  2002年   8195篇
  2001年   28245篇
  2000年   28786篇
  1999年   23664篇
  1998年   5164篇
  1997年   4253篇
  1996年   3833篇
  1995年   3481篇
  1994年   3107篇
  1993年   2854篇
  1992年   16065篇
  1991年   14838篇
  1990年   14170篇
  1989年   13970篇
  1988年   12597篇
  1987年   12067篇
  1986年   11129篇
  1985年   10337篇
  1984年   6918篇
  1983年   5606篇
  1982年   2719篇
  1979年   5484篇
  1978年   3349篇
  1977年   2974篇
  1975年   2645篇
  1974年   3071篇
  1973年   2869篇
  1972年   2830篇
  1971年   2774篇
  1970年   2521篇
  1969年   2544篇
  1968年   2254篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The activities of lysosomal maltase in the serum, urine and kidney were determined in rats with diabetes induced by streptozotocin (STZ, 75 mg/kg, i.p.) and compared with the changes in N-acetyl-beta-D-glucosaminidase (NAG) activity. Moreover, effects of insulin on maltase and NAG activities of the serum, urine and kidney in diabetic rats were studied. The following results were obtained: 1) The serum maltase activity within 24 hr after administration of STZ was influenced by insulin secretion. 2) Significant increases in blood urea nitrogen (BUN) levels were observed from the 3rd week after a single administration of STZ. The serum insulin level significantly decreased at 3 weeks after treatment of STZ. In this time, maltase activity in the serum rapidly increased, while the enzyme activity in the kidney decreased considerably. On the other hand, the changes in NAG activities in the serum, urine and kidney after administering STZ were almost similar to those in maltase activities. 3) There were positive relationships between maltase and NAG activities in the serum and urine in diabetic rats, respectively. 4) When lente insulin (2U) was subcutaneously injected once daily for 20 days from 24 hr after administration of STZ, NAG activities in the serum and kidney approached to the control levels. However, maltase activities in the group treated with insulin were significantly higher in the serum and kidney than those in the control group.  相似文献   
992.
The electrophysiological actions of SUN 1165 on isolated guinea pig atrial and papillary muscles, canine Purkinje fibers, and rabbit sinoatrial node were studied using standard microelectrode techniques. SUN 1165 in low (10(-7) g/ml) concentration had little effect on any of the action potential parameters measured. Intermediate (10(-6) g/ml) concentration of the compound shortened the duration of action potential of canine Purkinje fibers and increased ratio of the effective refractory period to the duration of action potential at 90% repolarization in guinea pig atrial muscles. At high (10(-5) g/ml) concentration, the compound reduced the maximum rate of rise of phase 0 in guinea pig atrial, papillary muscles, and canine Purkinje fibers, though the change in the latter was not statistically significant, and also decreased the action potential amplitude in guinea pig atrial muscles and canine Purkinje fibers. At all concentrations (10(-7)-10(-5) g/ml) tested, the compound exerted little effect both on spontaneous action potentials in rabbit sinoatrial node cells and on Ca2+-mediated slow responses in partially depolarized guinea pig papillary muscles. These results indicate that SUN 1165 may selectively inhibit cardiac sodium channels and is likely to be of value in correcting not only ventricular but also supraventricular tachyarrhythmias.  相似文献   
993.
A new diterpene antitumor antibiotic, myrocin C, has been isolated from the culture filtrate of a soil fungus, Myrothecium verrucaria strain No. 55. The antibiotic was effective against Gram-positive bacteria, fungi and yeasts, and prolonged the life span of mice bearing Ehrlich ascites carcinoma.  相似文献   
994.
Metabolic disorders during hepatic transplantation can be partly induced by blood transfusion. A retrospective survey of perioperative biological data recorded in patients under 18 years of age having liver transplantation was performed. Blood transfusion was also studied. For this evaluation, patients were divided in a paediatric group I (n = 20; mean age: 3.7 years) and an adolescent group II (n = 11; mean age: 14.3 years). Blood transfusion was significantly (p less than 0.05) more important in group I (302 +/- 286 ml X kg-1) than in group II (148.5 +/- 156 ml X kg-1). Autotransfusion of washed red cells was performed in six patients, allowing a mean 17 +/- 7% saving in blood transfusion. Severe hypernatraemia over 152 mmol X l-1 due to blood transfusion was observed only in five patients in group I. Hyperglycaemia increasing till the revascularization of the new liver was constant in both groups, but significantly more pronounced in group II. Cardiac arrest occurred twice in group I at initial revascularization. In group I, children with biliary atresia were not significantly different from the others for the duration of operation and the volume of blood transfusion; however the latter was more abundant. Conversely, in group II, the duration of operation was longer (p less than 0.05) in patients with previous abdominal surgery than in others. Finally the paediatric group differs from the adolescent group by obvious differences in anaesthesia and intensive care and specifically in hepatic transplantation by larger volume of blood transfusion leading to severe hypernatraemia. In further studies, adolescents should be distinct from the paediatric group and included in the adult group.  相似文献   
995.
OK-432 is an immunopotentiator which is normally administered by injection. In the present study, the antitumor activity of orally administered OK-432 on various solid tumors and the absorption of OK-432 from the gut were studied. Orally administered OK-432 inhibited the growth of Meth-A and BAMC-1 fibrosarcomas which had been subcutaneously transplanted in BALB/c mice. Autoradiograms of mice which had been administered 14C-labelled OK-432 orally demonstrated the absorption of OK-432 from the gut, and about 6% of orally administered OK-432 was absorbed 24 hrs after its administration. Moreover, an immunofluorescent study using an anti-OK-432 antibody revealed specific fluorescence in the mesenteric lymph node of mice which had been orally administered with OK-432. These results suggest that oral administration of OK-432 may be a beneficial immunotherapy.  相似文献   
996.
2-(2,3,3-Triiodoallyl)tetrazole (ME1401), a novel antifungal agent, showed therapeutic effectiveness in topical treatment of experimental dermal infections with Trichophyton mentagrophytes and Candida albicans in guinea-pigs. Addition of diethyl sebacate to the ME1401 preparations increased its in vivo antifungal activity and its penetration into the skin. When the estimation of efficacy of treatment with active formulations was made on the basis of skin lesion and the rate of negative skin cultures in comparison with those for infected, untreated or placebo-treated controls, the in vivo activity of 0.5% ethanol tincture or gel of ME1401 was comparable to that of reference antimycotic drugs such as clotrimazole, haloprogin and others. Pharmacokinetic studies in the experimental animals demonstrated that ME1401 was unstable in vivo, being readily converted to an active metabolite 2-(3-iodopropargyl)tetrazole (CN144) first and then to 2-propargyltetrazole (CN151). CN144 showed potent in vitro and in vivo antifungal activities, while the in vitro activity of CN151 was negligible.  相似文献   
997.
The ontogeny of gamma-melanocyte stimulating hormone (gamma-MSH)-like immunoreactive (gamma-MSHI) structures in the brain and hypophysis was investigated in the rat by means of indirect immunofluorescence. gamma-MSHI neurons in the arcuate nucleus appeared at Day 13 of gestation, in the anterior hypophysis at Day 16, in the intermediate lobe at Day 18, and in the nucleus commissuralis after birth. gamma-MSHI fibers first appeared at Day 15 of gestation in the hypothalamic area and extended dorsally to reach the surface of the diencephalon. At Day 16 of gestation, another gamma-MSHI fiber bundle was found that ran laterally along the ventral surface of the diencephalon. At Day 19, immunoreactive fibers first appeared in the forebrain, diencephalon, midbrain and upper pons, and thereafter they increased in number, reaching a maximum at postnatal Day 15. gamma-MSHI fibers in the lower pons and medulla oblongata first appeared after birth. They also increased in number with age and reached a maximum at postnatal Day 15. The present ontogenetical study has demonstrated the different times of first appearance of each of the 3 major gamma-MSHI structures-containing cell groups in the brain, i.e., the arcuate nucleus, hypophysis and nucleus commissuralis. These findings may reflect the different functions of 3 groups of cells.  相似文献   
998.
999.
1000.
The purpose of this communication was to find out the factors influencing the late patency ratio of coronary artery bypass grafts of 42 patients in our institution. The following results were obtained: 1. The size of the measured diameters of coronary arteries and the graft flow rates were correlated well to the late patency ratio (p less than 0.05). 2. The regular physical exercise trainings were significantly important to keep patent grafts (p less than 0.01). 3. In blood serum studies, serum uric acid levels were significantly lower (p less than 0.05), the average mean HDL cholesterol levels were much higher (p less than 0.001) and the ratio of total cholesterol to HDL cholesterol were significantly lower in the group with late patent grafts than with grafts occluded. Therefore, we found out the variables affecting graft patency ratio which were examined by a stepwise method were the diameter of the coronary artery, regular physical exercise training, the average of lower serum uric acid levels and higher HDL cholesterol levels. The multiple coefficient for these four variables was 0.562 (p less than 0.001) and the contribution was 31.6%. According to the base of this studies, we have concluded that postoperative regular physical exercise, low fat and restricted calorie intake were very important to keep the late patent grafts in long-term follow up period after coronary bypass surgery.  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