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   932224篇
  免费   66379篇
  国内免费   1343篇
耳鼻咽喉   12960篇
儿科学   24370篇
妇产科学   23233篇
基础医学   132941篇
口腔科学   28298篇
临床医学   80552篇
内科学   183348篇
皮肤病学   19230篇
神经病学   72180篇
特种医学   36809篇
外国民族医学   79篇
外科学   152164篇
综合类   18049篇
现状与发展   1篇
一般理论   234篇
预防医学   61743篇
眼科学   21320篇
药学   72605篇
  3篇
中国医学   2168篇
肿瘤学   57659篇
  2018年   8968篇
  2017年   7038篇
  2016年   7772篇
  2015年   8867篇
  2014年   11998篇
  2013年   17510篇
  2012年   24089篇
  2011年   25052篇
  2010年   14809篇
  2009年   14277篇
  2008年   24608篇
  2007年   25697篇
  2006年   26483篇
  2005年   25445篇
  2004年   24578篇
  2003年   23621篇
  2002年   23172篇
  2001年   54746篇
  2000年   56553篇
  1999年   46959篇
  1998年   10739篇
  1997年   9474篇
  1996年   9597篇
  1995年   8928篇
  1994年   8282篇
  1993年   7595篇
  1992年   35495篇
  1991年   33918篇
  1990年   32759篇
  1989年   31880篇
  1988年   29001篇
  1987年   28257篇
  1986年   26295篇
  1985年   25151篇
  1984年   17835篇
  1983年   15147篇
  1982年   7797篇
  1981年   6775篇
  1979年   15787篇
  1978年   10599篇
  1977年   9059篇
  1976年   7872篇
  1975年   8630篇
  1974年   10468篇
  1973年   9860篇
  1972年   9358篇
  1971年   8858篇
  1970年   8433篇
  1969年   7928篇
  1968年   7202篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
Sixteen dogs had one tibia filled with acrylic PMMA bone cement and the opposite, control tibia filled with inert bone wax. After 1, 4, and 12 weeks, the blood perfusion in diaphyses was measured with Sc-46 labeled microspheres. The blood flow rates increased from 1 to 4 weeks and dropped to about the 1-week level after 12 weeks on both sides, with the acrylic side lower than the control side. On both sides, Disulphine Blue staining of the bones showed severe endosteal avascularity after 1 and 4 weeks and massive periosteal apposition after 4 and 12 weeks. The initial increase in blood flow is considered due to periosteal apposition, and the differences in blood flow rates are attributed to avascularity caused by the polymerization heat and toxicity of the acrylic cement.  相似文献   
942.
We have developed an implant heating system (IHS) for interstitial hyperthermia of brain tumors. IHS consists of three compartments: ferromagnetic implant with low Curie point, induction coil and generator to produce high frequency magnetic field. The device works as follows: It is heated up to a Curie temperature (Tc) by Eddy current under the magnetic field. Heat generated in the implant is conducted to the tumor tissue into which it has been implanted. To evaluate the effect of this hyperthermia, a brain tumor model was produced by innoculation of VX2 tumor cells and treated either by hyperthermia with IHS alone, chemotherapy with ACNU alone, or with a combination of both. The longest survival was obtained by the combined treatment, and significant prolongation of survival was found in the single treatment groups. In the Phase I clinical trial, one or several implants (1.8 mm X 15 mm, Tc = 68 degrees C) made of Fe-Pt alloy were placed in the tumor by CT guided stereotactic procedure, or manually during craniotomy. Hyperthermia of above 42 degrees C for 30 to 60 minutes twice a week was brought about in ten cases of malignant brain tumor. CT evaluation was made in nine cases treated for more than ten times in this way. Five out of the nine cases responded to this hyperthermia with irradiation. In conclusion, a safe, repeated and longterm treatment was possible without significant side effects. The hyperthermia with IHS may also be applicable to benign intracranial tumors and neoplasms in other part of body as well.  相似文献   
943.
Based on repeated fluoroangiographic examinations in a group of 28 children with type I diabetes mellitus the authors observed progressing diabetic retinal changes. At the end of the three-year observation period they found progress in 32% of the children. They investigated influence of risk factors such as age, duration of the basic disease, its metabolic compensation, sex and HLA typing on the development of diabetic retinopathy.  相似文献   
944.
The laminar structure and cellular distribution of cytochrome-oxidase (CO) reactivity in supragranular puffs of striate cortex was examined in adult macaque monkeys surviving various periods of monocular enucleation, lid suture, and retinal impulse blockage with tetrodotoxin (TTX). Enucleation and TTX produced a rapid and severe loss in the size of the CO reactive region in puffs dominated by the removed or treated eye compared to slower and less marked reductions obtained in deprived puffs of lid-sutured monkeys. In all deprived animals, the cross-sectional areas of deprived puffs decreased most rapidly in the upper layers (2 and 3A). In long-term enucleated (60 wks) and TTX-treated (4 wks) monkeys, puff area was severely reduced in layer 3B, while reactivity in layer 3B appeared partially spared in lid-sutured monkeys. The density of the CO reaction product was significantly and evenly reduced throughout deprived puffs for all of the monkeys examined; however, this decrease was less severe in adult monkeys lid-sutured for 11 wks. Although no evidence for cell loss was obtained, all three forms of visual deprivation led to lower counts of neuronal perikarya with high levels of CO reaction product in both deprived puff and interpuff areas. This effect was less marked in the deprived puffs of monkeys lid-sutured for 2.5 and 3 yrs, suggesting recovery of CO activity in some neurons. Neurons in deprived puffs and interpuffs were generally similar in size to those in nondeprived regions, although CO-reactive cells were significantly smaller in the deprived puffs of monkeys enucleated for 28.5 or 60 wks. These results indicate that the metabolic response of neuronal elements in supragranular striate cortex depends upon the nature of the visual deficit. The partial sparing of CO reactivity in deprived puffs of lid-sutured monkeys may reflect the continued transmission of certain types of visual stimuli through a closed eyelid.  相似文献   
945.
946.
Immunoblotting of streptococcal antigens in guttate psoriasis   总被引:6,自引:0,他引:6  
Guttate psoriasis may be precipitated by acute streptococcal infection, usually of the upper respiratory tract. We have studied the immune response to streptococci in 26 patients presenting with a first or recurrent episode of acute guttate psoriasis (AGP), using immunoblotting. Eighteen of 26 patients studied had a demonstrable response to a wide range of streptococcal antigens using this approach, compared with 14 of 26 patients who demonstrated a response using more conventional anti-streptococcal antibody tests. Patients with AGP had a significantly higher antibody detection score using immunoblotting than did control subjects (P<0.005). We conclude that immunoblotting is a useful technique in studying this condition and may be of benefit in exploring the immunopathogene-sis of AGP.  相似文献   
947.
Trazodone hydrochloride is an oral antidepressant agent which has been associated with the improvement of erections in impotent men and the development of prolonged erections or priapism in potent men. An in vivo study in animal and human subjects was performed to gain experience with the effect of intracavernosal trazodone. In the anesthetized New Zealand White rabbit, intracavernosal trazodone or its major metabolite m-chlorophenylpiperazine (m-CPP) produced full penile erection in 76% and 84% of animals studied respectively with doses ranging from one to 15 mg. On the other hand, intracavernosal administration of five mg. papaverine resulted in a prolonged erection in 90% of animals studied. In 13 selected volunteer patients, intracavernosal trazodone caused tumescence but not full penile erection with corporal body pressures of 28.2 +/- 5.8 mm. Hg. Intracavernosal papaverine or papaverine and phentolamine in these subjects resulted in significantly higher corporal body pressures of 58 +/- 18 mm. Hg (p less than .05). Intracavernosal administration of alpha adrenoceptor agonists but not normal saline resulted in complete detumescence of trazodone- or m-CPP-induced prolonged erection in the animal studies. Intracavernosal trazodone results in erectile activity that appears in part based on its local alpha blocking activity but like other intracavernosal alpha-blocking agents is not as effective in initiating penile erections as are intracavernosal agents that directly induce smooth muscle relaxation.  相似文献   
948.
On the basis of analysis of surgical treatment of 753 patients with coxarthrosis during 1970-1987, the authors set forth the stages of arthroplasty development in the USSR, using the experience of the Kharkov research institute of orthopaedics and traumatology named after M. I. Sitenko on the problems of arthrodesis operations, endoprosthetics and biological arthroplasty. In the article are presented the peculiar features of diagnostic and surgical tactics in case of patients with idiopathic and dysplastic coxarthrosis; operation technique for each form is presented in details. The authors have developed a new perosseous access to the hip joint, which made a good showing and permits to preserve the integrity of periarticular muscles and neurovascular formations. Application of the given access made possible the extension of indications for arthroplasty in case of grave forms of coxarthrosis, met earlier in a reserved manner.  相似文献   
949.
950.
A 10-month-old child with achondroplasia with progressive head enlargement, ventriculomegaly, and wide subarachnoid spaces over the hemispheres was referred for evaluation. A steady-state lumbar infusion test revealed increased cerebrospinal fluid (CSF) outflow resistance (14 mm Hg/ml/min), and intra-arterial digital subtraction angiography (DSA) demonstrated bilateral venous outflow obstruction due to stenosis of the jugular foramen. Surgical decompression by opening the right jugular foramen relieved the clinical signs of intracranial hypertension. During the following year, the patient's head enlargement was moderate with relative normalization of size. Repeat DSA demonstrated improved venous runoff on the right side, and a steady-state lumbar infusion test demonstrated reduced CSF outflow resistance (10 mm Hg/ml/min). Venous decompression is causal therapy and may prove to be preferable to shunting in children with hydrocephalus and bilateral stenosis of the jugular foramen.  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