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   2626634篇
  免费   189509篇
  国内免费   10505篇
耳鼻咽喉   34604篇
儿科学   85804篇
妇产科学   72107篇
基础医学   368428篇
口腔科学   70304篇
临床医学   239966篇
内科学   521838篇
皮肤病学   62813篇
神经病学   215867篇
特种医学   101142篇
外国民族医学   753篇
外科学   390791篇
综合类   56980篇
现状与发展   10篇
一般理论   974篇
预防医学   198622篇
眼科学   57806篇
药学   192093篇
  39篇
中国医学   7170篇
肿瘤学   148537篇
  2021年   22055篇
  2019年   22083篇
  2018年   30768篇
  2017年   23879篇
  2016年   27428篇
  2015年   31284篇
  2014年   42660篇
  2013年   62434篇
  2012年   83185篇
  2011年   87679篇
  2010年   52911篇
  2009年   50713篇
  2008年   81143篇
  2007年   85998篇
  2006年   87601篇
  2005年   83797篇
  2004年   80055篇
  2003年   77374篇
  2002年   74434篇
  2001年   129246篇
  2000年   132234篇
  1999年   111518篇
  1998年   31857篇
  1997年   28578篇
  1996年   28709篇
  1995年   27829篇
  1994年   25459篇
  1993年   23700篇
  1992年   85449篇
  1991年   81822篇
  1990年   78997篇
  1989年   76243篇
  1988年   69624篇
  1987年   68148篇
  1986年   63672篇
  1985年   60600篇
  1984年   44984篇
  1983年   38002篇
  1982年   22495篇
  1981年   20029篇
  1979年   38987篇
  1978年   27451篇
  1977年   23264篇
  1976年   21502篇
  1975年   22820篇
  1974年   26800篇
  1973年   25384篇
  1972年   23754篇
  1971年   21960篇
  1970年   20185篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
971.
We developed a novel method which enables bloodless exposure of the levator veli palatini muscle in rat in order to investigate the physiological properties of this muscle. The levator veli palatini muscle which is innervated by a branch of the glossopharyngeal nerve showed rhythmic spontaneous movement in rats. Cutting the branch supplying LVP of the glossopharyngeal nerve caused cessation of the spontaneous movement of the levator veli palatini muscle. The spontaneous discharges of the glossopharyngeal nerve were synchronized with those of the phrenic nerve. A mixture of 95% oxygen and 5% room air influenced the efferent discharges from the branch of the glossopharyngeal nerve supplying the levator veli palatini muscle. These findings indicate that the motor nerve supply to the levator veli palatini muscle is the glossopharyngeal nerve, and the levator veli palatini muscle is related to the respiratory system, in particular with inspiration in rats.  相似文献   
972.
This paper discusses the application of intravenous Kalipsol anesthesia in combination with Seduxen (Relanium) in 22 patients who underwent antro-mastoidectomy (expanded) and fronto-ethmoidectomy. No complications related to the method of anesthesia were identified. It is concluded that the use of Kalipsol anesthesia in urgent ENT operations provides better surgical intervention. This method ensures adequate analgesia during operation.  相似文献   
973.
This paper reports the changes in prolactin levels after 12 spontaneous and 52 induced pregnancies in 54 women with unambiguous hyperprolactinaemia (median plasma prolactin levels 67.5 ng/ml, range 40-400). Twenty-three of the patients showed radiological evidence of prolactinoma. The pregnancies were induced in 37 patients by bromocriptine, in nine by metergoline, in two by lisuride and in four by other treatments. Of the 64 pregnancies, 16 ended in spontaneous abortion, while 48 went to term. Follow-up was continued for at least 6 months after delivery or until the end of lactation. In a control group of 32 hyperprolactinaemic women (median prolactin 70 ng/ml, range 40-400) not wishing to become pregnant, prolactin changes were similarly registered over a mean period of 15 months without any treatment (range 6-38 months). After pregnancy, a significant downward trend of plasma prolactin was observed in the puerperal women with a 'normalization' rate of 17%. No changes were observed in the 32 controls who did not become pregnant.  相似文献   
974.
X chromosome instability associated with familial Turner syndrome   总被引:1,自引:0,他引:1  
A family with two members (two generations) exhibiting Turner syndrome is described. Cytogenetic studies on these individuals showed the presence of multiple X chromosome changes. Evidence is presented to show that the maternally inherited X chromosome is the chromosome involved in the structural alterations observed. The effect of a tendency of the maternal X chromosome to break at specific sites on the development of the Turner phenotype and abnormal karyology is discussed.  相似文献   
975.
976.
Human subjects maintained isometric plantar or dorsal flexions of the ankle in a matching task. H-reflexes of different sizes were superimposed on the steady activity. The peak-to-peak amplitude of the reflexes was measured on the electromyogram (EMG) of the soleus muscle. The size of the corresponding muscle contractions was determined on the isometric torque signal in relation to the maintained flexion force. The EMG-torque relation which was defined as the reflex muscle contraction as a function of the EMG reflex signal approximated a square root function for a given steady contraction level. It was not modulated by steady dorsal flexions, but it decreased continuously with stronger plantar steady torques. This dependence was caused by the silent period following the reflex discharge. Since the reflex discharge and the silent period were near in time to the duration of the contraction, the silent period had a direct effect on the reflex contraction amplitude.  相似文献   
977.
Plasma tumor necrosis factor and mortality in critically ill septic patients   总被引:23,自引:0,他引:23  
Tumor necrosis factor (TNF) cachectin has been implicated as an important host mediator responsible for shock and multiple organ failure (MOF) observed during sepsis. Using a sensitive enzyme-linked immunosorbent assay, we measured plasma TNF levels in 43 septic patients suffering from a broad range of diseases. Measurements were taken on the day that sepsis was diagnosed. Eleven patients had detectable TNF plasma levels ranging from 10 to 100 pg/ml (TNF-positive group); in 32 patients circulating TNF could not be detected (TNF-negative group). The groups did not differ significantly as to age, underlying disease, percentage positive bacteremia and bacteriologic profile, sepsis score, and extent of MOF. Eight (73%) of 11 TNF-positive patients died from sepsis during ICU stay, vs. 11 (34%) of 32 TNF-negative patients (p less than .05). This study demonstrates that sepsis is accompanied by detectable circulating TNF in 25% of the cases, and for these patients mortality is twice that for comparable TNF-negative patients.  相似文献   
978.
B R Wang  E Senba  M Tohyama 《Neuroscience》1989,28(3):711-723
Studies were made on whether substance P-, leucine-enkephalin- and 5-hydroxytryptamine (serotonin)-like immunoreactive fibers exert a direct influence on the cremaster motoneurons of the male rat by immunocytochemistry combined with retrograde tracing at the light- and electron-microscopic levels. Horseradish peroxidase was used as a retrograde tracer. Two days after injection of horseradish peroxidase into the genitofemoral nerves, its accumulation in the cremaster motoneurons was demonstrated by the diaminobenzidine-nickel method. On immunocytochemical examination of the same sections immunoreactive end-products were detected by the peroxidase-antiperoxidase method. Two different kinds of reaction products were distinguishable at both the light- and electron-microscopical levels. The horseradish peroxidase-labeled cremaster motoneurons at the L1 and L2 levels of the spinal cord were surrounded by abundant immunoreactive terminals. Examination at the ultrastructural level showed that substance P-like immunoreactive terminals formed synaptic contacts almost exclusively with the proximal dendrites of these horseradish peroxidase-labeled cremaster motoneurons. On the other hand, in the leucine-enkephalin- and serotonin-like boutons, significant numbers of axosomatic contacts with horseradish peroxidase-labeled cells were seen although axodendritic contacts with horseradish peroxidase-labeled cells were predominant. Occasionally, leucine-enkephalin-like immunoreactive fibers with synapses on horseradish peroxidase-labeled neurons formed axoaxonic contacts with other leucine-enkephalin-like axonal terminals. Thus, substance P-, leucine-enkephalin- and serotonin-like fibers clearly regulate the function of cremaster motoneurons monosynaptically. The varied synaptic contacts of these fibers according to the neuroactive substances involved suggest different actions of these substances on the cremaster motoneurons.  相似文献   
979.
Formulae for the calculation of the count of microorganisms isolated from natural bacterial biocenoses of a child's body have been derived. The authors suggest a variant of simplified drip method for the computation of microorganism colonies in solid media. The described method helps cut down the nutrient media consumption at least 3-fold and is time-saving.  相似文献   
980.
A fluid-fiber-collagen stress tensor is used to describe the rheology of the left ventricle of the heart. Linear theory is used to find the equilibrium solutions for the end-diastolic and end-systolic states of general axisymmetric shapes that are small perturbations of a thick-walled finite cylinder. The general problem can be studied by superposing the effects of variable midwall radius but constant wall thickness with those of variable wall thickness but constant midwall radius. A Fourier series representation is used to describe the midwall radius and thickness functions. Numerical calculations are performed to determine the deformed geometry and spatial distributions of tissue pressure, stresses, and fiber strains. The calculations proved to be highly accurate when compared to an analytical solution obtained for the special case of no fibers. The results show significant longitudinal differences when compared to results for the cylindrical geometry, with more sensitivity to variation in wall thickness than to variation in midwall radius.  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