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   366419篇
  免费   14956篇
  国内免费   864篇
耳鼻咽喉   5058篇
儿科学   12989篇
妇产科学   9455篇
基础医学   48604篇
口腔科学   14138篇
临床医学   28067篇
内科学   73464篇
皮肤病学   8938篇
神经病学   26074篇
特种医学   15491篇
外国民族医学   124篇
外科学   50179篇
综合类   2513篇
现状与发展   1篇
一般理论   71篇
预防医学   34369篇
眼科学   7383篇
药学   24276篇
  2篇
中国医学   913篇
肿瘤学   20130篇
  2022年   2224篇
  2021年   4104篇
  2020年   2805篇
  2019年   3925篇
  2018年   8206篇
  2017年   7276篇
  2016年   6622篇
  2015年   8646篇
  2014年   9684篇
  2013年   10457篇
  2012年   20536篇
  2011年   16324篇
  2010年   8242篇
  2009年   9116篇
  2008年   11096篇
  2007年   12379篇
  2006年   11831篇
  2005年   19503篇
  2004年   20013篇
  2003年   15156篇
  2002年   9230篇
  2001年   9494篇
  2000年   6908篇
  1999年   10240篇
  1998年   2126篇
  1996年   1695篇
  1992年   9489篇
  1991年   9651篇
  1990年   9685篇
  1989年   9267篇
  1988年   8576篇
  1987年   8180篇
  1986年   7775篇
  1985年   6993篇
  1984年   4881篇
  1983年   3935篇
  1979年   4739篇
  1978年   2984篇
  1977年   2270篇
  1976年   1975篇
  1975年   3021篇
  1974年   3662篇
  1973年   3283篇
  1972年   3209篇
  1971年   3152篇
  1970年   3013篇
  1969年   2913篇
  1968年   2677篇
  1967年   2552篇
  1966年   2227篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Hypertension in developing countries   总被引:2,自引:0,他引:2  
Population surveys carried out since the 1970s in 15 developing countries including 23 population groups show that the prevalence of hypertension ranges from as low as 1% in some African countries to over 30% in Brazil. A trend analysis of the mortality statistics for 35-74 year-olds from 16 countries in which data are available shows a downward trend in mortality from hypertension and cerebrovascular diseases in most of these countries. In spite of the current low prevalence in some countries, the total number of hypertensives in the developing world is high, and a cost assessment of possible antihypertensive drug treatment indicates that developing countries cannot afford the same drug treatment levels as developed countries.  相似文献   
993.
Totally, 185 patients, operated on for a fresh hip fracture, were randomly allocated to either methicillin antibiotic prophylaxis or no prophylaxis and followed for 1 month. Two superficial wound infections were recorded in the prophylaxis group and one in the control group. Prophylactic use of antibiotics in surgery for hip fractures seems unnecessary provided strict aseptic routines in the operating room are followed.  相似文献   
994.
The authors give an account of 190 premature infants they treated in 1956-1988, suffering from retinopathy of prematurity--ROP, and for prolonged subsequent periods. As the head of the team followed up all the children, there is an integrated view of the problem. The birth weight of the infants was 640 g--1,900 g. From the total number 76.8% infants had a birth weight of 1,500 g or less, 13.7% had a birthweight of 1,000 g or less. Evidence of the increasing rate is provided by the number of patients treated since birth at the department for premature and pathological infants FNM as well as by the number of children admitted from other departments after development of ROP. In 1956-1970, i. e. in 15 years, the authors looked after 34 patients, in 1971-1988, i. e. in 18 years there were 156 children with ROP. In 1956-70 cases of ROP predominated which developed as a result of absolute or relative hypoxia. They were successfully treated by individually adjusted and carefully controlled oxygen therapy (6.9% blind children). In 1971-1975 the possibility to use this therapy declined briskly because after introduction of modern medical technique the number of findings suggesting a hyperoxic insult increased. At that time the results deteriorated greatly (50% blind children). In 1976-1980 the results were favourably influenced by individual dosage of oxygen therapy in all infants, based on regular monitoring of blood gases (10.5% blind children).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
995.
To obtain more insight into the effect of moderate alcohol intake on vitamin B-6 status indicators, we studied the associations of alcohol intake (unadjusted and adjusted for intake of vitamin B-6 and protein) with the erythrocyte aspartate aminotransferase activation coefficient (EAST-AC) and plasma pyridoxal 5'-phosphate (PLP) level. Data obtained from men (n = 224) and women (n = 217) aged 65-79 (nationwide sample in the Netherlands) were used for this purpose. Although alcohol intake (a maximum of 21% of the energy came from alcohol) tended to be positively associated with PLP, this association never reached statistical significance (p greater than or equal to 0.05). EAST-AC was inversely associated with alcohol intake, whether or not it was adjusted for vitamin B-6 and protein intake. Similar results were found for the total EAST activity (after adding PLP) or apoenzyme activity; the basal EAST activity (before adding PLP) or holoenzyme activity was not associated with the alcohol intake. These results indicate that caution is needed in the interpretation of the specificity of EAST-AC (i.e., the degree to which EAST-AC is unaffected by other factors) as an indicator of vitamin B-6 intake.  相似文献   
996.
The results of treatment of 160 patients with coccygodynia were analysed. The condition was caused by contusion, fracture or dislocation of coccygeal vertebrae or excess of osteochondral tissue around the coccyx. The patients were treated conservatively and surgically, 56 and 104 respectively. In 94 cases (50,3%) of surgically treated complete recovery was achieved. Surgery should be undertaken in cases not responding to conservative measures.  相似文献   
997.
The ability of the Lyme disease spirochete to attach to host components may contribute to its ability to infect diverse tissues. We present evidence that the Lyme disease spirochete expresses a lectin activity that promotes agglutination of erythrocytes and bacterial attachment to glycosaminoglycans. Among a diverse collection of 21 strains of Lyme disease spirochete, hemagglutinating activity was easily detected in all but 3 strains, and these three strains were noninfectious. The ability to agglutinate erythrocytes was associated with the ability of the spirochete to bind to the sulfated polysaccharide dextran sulfate and to mammalian cells. Soluble dextran sulfate was a potent inhibitor of both hemagglutination and attachment to mammalian cells, while dextran had no effect on either activity, suggesting that dextran sulfate may inhibit attachment by mimicking host cell glycosaminoglycans. Consistent with this, the spirochete bound to immobilized heparin, and soluble heparin inhibited bacterial adhesion to mammalian cells. The bacterium did not bind efficiently to Vero cells treated with heparinase or heparitinase or to mutant CHO cell lines that are deficient in proteoglycan synthesis. Sulfation of glycosaminoglycans was critical for efficient bacterial recognition, as Vero cells treated with an inhibitor of sulfation, or a mutant CHO cell line that produces undersulfated heparan sulfate, did not mediate maximal spirochetal binding. Binding of the spirochete to extracellular matrix also appeared to be dependent upon this attachment pathway. These findings suggest that a glycosaminoglycan-binding activity which can be detected by hemagglutination contributes to the attachment of the Lyme disease spirochete to host cells and matrix.  相似文献   
998.
1. Guanosine 3':5'-cyclic monophosphate (cyclic GMP) release and vascular tone was measured in the isolated kidney of the rat perfused at constant flow with Krebs-Henseleit solution. The effects of 3 vasodilators, acetylcholine (ACh), atrial natriuretic factor (ANF) and sodium nitroprusside (SNP) on the renal release of cyclic GMP and vascular tone were examined. The ability of the endothelial-derived relaxing factor (EDRF) inhibitors, haemoglobin and gossypol, to modify vasodilatation and vasodilator-induced changes in cyclic GMP releases from the kidney was also investigated. 2. Renal cyclic GMP release was elevated 8 fold by ANF (0.01 microM), 5 fold by SNP (1 microM) and 3 fold by ACh (0.3 microM). 3. For ACh, both the increase in renal cyclic GMP release and the vasodilatation were reduced by the EDRF inhibitors, haemoglobin (1 microM) and gossypol (15 microM). For SNP, neither the increase in renal cyclic GMP release nor vasodilatation were inhibited by gossypol (15 microM). 4. For ANF, neither the increase in cyclic GMP release from the kidney nor its vasodilator activity were affected by haemoglobin (1 microM). 5. EDRF inhibitors reduced the basal release of cyclic GMP from 0.32 +/- 0.06 pmol min-1 to 0.18 +/- 0.03 pmol min-1, gossypol being more effective than haemoglobin. 6. The results are consistent with the ability of ACh to induce EDRF-mediated vasodilatation in the isolated perfused kidney of the rat. Basal EDRF release appears to contribute approximately 50% to the basal release of cyclic GMP from this preparation.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
999.
Case report of a very large ectasia of the urethra in a 9 years old boy without any organic conflict and without any neuro-urologic trouble. It could be a particular syndrome.  相似文献   
1000.
The scanning laser ophthalmoscope provided a high quality television image of the fundus with minimal illumination of the retina. This new device based on a totally new electro-optical principle allowed a detailed exploration of macular function directly under simultaneous fundus control. The focused beam of a yellow krypton laser (568,2 nm) was swept up and down, rights and links across the fundus to form a raster of parallel lines on the retina. The S.L.O. illuminated only a single retinal point at a time and illumination was reduced to less than 70 microw/cm2 versus 100,000 microns/cm2 for indirect ophthalmoscopy and 4,000,000 microw/cm2 for fluorescein angiography. The intensity of the laser beam could be modified with the microcomputer by means of an acousto-optic modulator. It was possible to produce static or dynamic graphic designs that were simultaneously viewed by the patient and observed by the examiner on the patient's fundus on the video monitor. Further computerized analysis of the videotaped scanning laser ophthalmoscopic images gave a functional retinal map with correction for shifts of stimulus position due to fixational saccadic eye movements. The map showed true retinal location of 1. fixation area; 2. scotoma. The clinical evaluation was completed with 3. measurement of visual acuity in any foveal or parafoveal location. The results of scanning laser ophthalmoscopy were illustrated with the report of datas in a patient with diffuse retinal pigment epithelial decompensation.  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