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   4458847篇
  免费   342842篇
  国内免费   15008篇
耳鼻咽喉   61704篇
儿科学   142119篇
妇产科学   116766篇
基础医学   680075篇
口腔科学   121659篇
临床医学   403393篇
内科学   811668篇
皮肤病学   110099篇
神经病学   376775篇
特种医学   171864篇
外国民族医学   755篇
外科学   667801篇
综合类   121807篇
现状与发展   24篇
一般理论   2634篇
预防医学   373639篇
眼科学   103494篇
药学   315314篇
  26篇
中国医学   12322篇
肿瘤学   222759篇
  2021年   57695篇
  2020年   36614篇
  2019年   60392篇
  2018年   77133篇
  2017年   58781篇
  2016年   64872篇
  2015年   77844篇
  2014年   112329篇
  2013年   178679篇
  2012年   131159篇
  2011年   136831篇
  2010年   129066篇
  2009年   129706篇
  2008年   121279篇
  2007年   129141篇
  2006年   137357篇
  2005年   131139篇
  2004年   132035篇
  2003年   121917篇
  2002年   110923篇
  2001年   168954篇
  2000年   164238篇
  1999年   150431篇
  1998年   71940篇
  1997年   67755篇
  1996年   65779篇
  1995年   61174篇
  1994年   55066篇
  1993年   51087篇
  1992年   107744篇
  1991年   102467篇
  1990年   98324篇
  1989年   95731篇
  1988年   88068篇
  1987年   86216篇
  1986年   81140篇
  1985年   79244篇
  1984年   66025篇
  1983年   58738篇
  1982年   47456篇
  1981年   44071篇
  1980年   41263篇
  1979年   55885篇
  1978年   45271篇
  1977年   40506篇
  1976年   37318篇
  1975年   37358篇
  1974年   40391篇
  1973年   38606篇
  1972年   36172篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
A retrospective analysis of results of treatment of 104 patients with fractures of long tubular bones associated with injuries of peripheral nerves has shown complex therapy to be necessary. Main components of this treatment were biogenic stimulators, vitamin B12, spasmolytic and dehydration drugs in combination with electrophoresis with potassium iodide and thermal procedures. Rapid disturbance of conductivity of nerve trunks after trauma should be followed by revision of the given segment of the extremity in order to remove hematoma and make reposition of displaced fragments of the bone, which can provide recovery of the disturbed function of the nerve.  相似文献   
992.
Summary Cytochemical staining of normal human bone cells in monolayer cultures for alkaline phosphatase (ALP) indicated that the cultures contained mixed-cell populations. Time course evaluations of the cytochemical staining revealed, in addition to the ALP-negative cell population, at least two subpopulations of ALP-positive human bone cells with different levels of ALP. A cytochemical method has been developed which separates the ALP-positive cells into high and intermediate ALP subpopulations. In this method, human bone cells were stained for ALP using an azo-dye method and incubating at 4°C for 10 and 30 minutes, respectively. We defined the cell population that stained positively for ALP at 10 minutes as strong ALP-positive cells, and both strong and intermediate cells were stained at 30 minutes. The intermediate cells were determined from the difference between the values at the two time points. The intra- and interassay variations of the assay, with the same investigator in blinded investigations, were both less than 10% and the interobserver variation was approximately 25%. Analysis of the distribution of ALP levels in cells with a laser densitometer confirmed the presence of at least three cell subpopulations. 1,25(OH)2D3 treatment increased the proportions of both ALP-positive cell populations, whereas TGF-beta treatment increased only the intermediate ALP-positive cell population. On the contrary, fluoride increased the proportion of the strong ALP cells, and IGF-1 had no effect on the proportions of either ALP-positive subpopulation. When the ALP-specific activity was compared with the percentage of each ALP-positive subpopulations for the cells treated with effectors, the ALP-specific activity correlated with the total ALP-positive and with the strong ALP-positive populations but not with the intermediate ALP-positive subpopulation. In summary, this study represents the first evidence that normal human bone cells in monolayer cultures contained at least two subpopulations of ALP-positive cells, and that bone cell effectors could have differential effects on each cell population.  相似文献   
993.
Studies were conducted to evaluate several cholecalciferol (D3 metabolites: 1,25-dihydroxycholecalciferol [1,25-(OH)2D3], 1,24R,25-trihydroxycholecalciferol [1,24R,25-(OH)3D3], 1 alpha-hydroxy-cholecalciferol (1 alpha-OHD3), 24R,25-dihydroxycholecalciferol [24R,25-(OH)2D3], 1,25-dihydroxy-26,27 hexadeuterium cholecalciferol (1,25-(OH)2-26,27[2H]6D3) and 1,25-dihydroxy-24R-fluorocholecalciferol [1,25-(OH)2-24R-FD3] for their activity in preventing the development of tibial dyschondroplasia in broilers. The basal diet used is low in calcium, high in phosphorus and chlorine and is known to promote a high incidence of tibial dyschondroplasia. The chicks received ultraviolet radiation from fluorescent lights in addition to 1100 ICU/kg (27.5 micrograms/kg) of D3 in the basal diet. Supplementation of the diet with 10 micrograms/kg of all the metabolites except 24R,25-(OH)2D3 significantly lowered the incidence and severity of tibial dyschondroplasia and increased bone ash when compared to birds receiving the basal diet. None of the active D3 metabolites was effective when fed at 0.1 or 1.0 micrograms/kg of diet. Two active compounds tested [1,25-(OH)2D3 and 1,24R,25-(OH)3D3] at 5 micrograms/kg of diet were effective in reducing either the incidence or severity of tibial dyschondroplasia.  相似文献   
994.
Two types of contrast media are now used in clinical magnetic resonance imaging (MRI). Intravenous gadolinium-DTPA serves as a marker of blood-brain barrier disruption while intravenous magnetic iron oxide particles are of value in imaging the liver and spleen. The efficacy of MRI is improved with these agents but the examination is prolonged.  相似文献   
995.
On the basis of experience with the treatment of more than 1,500 patients with post-burn defects, deformities, and trophic ulcers, the authors distinguished types of affection in which the traditional methods are ineffective. These 133 patients were subjected to plasty with ++cutaneo-fascial grafts; the zones of donor areas from which the grafts are taken are determined. Plasty with ++cutaneo-fascial grafts is indicated in defects of the face, deformity of the neck, total adduction contracture of the arm, defect of the breast, and affections of the hand, leg, and foot. Concrete grafts and the site from which they are taken for restoration of certain regions of the body are suggested. ++Cutaneo-fascial grafts make it possible to restore the shape, function, and the skin of the involved region.  相似文献   
996.
997.
Thirteen cases of primary appendicular adenocarcinoma are reported. This rare tumour usually presents as acute appendicitis. The correct diagnosis is rarely entertained before or during surgery. The main treatment choice lies between appendicectomy alone and appendicectomy followed by right hemicolectomy. There are anatomical reasons for advising the latter and survival figures from the literature tend to support this preference. The cases reported here indicate that in the period 1972-1984, in the North West Region, there was a slight preference for appendicectomy alone. The additional procedure of right hemicolectomy did not confer any clear-cut survival advantage.  相似文献   
998.
1. Effects of a novel imidazoindole derivative on cholinergic function were studied in isolated tissue preparations. 2. The compound demonstrated a dose-dependent (10(-11)-10(-9) potentiation (20-60%) of acetylcholine induced tension in guinea pig ileal tissue. 3. Increases in the size of end-plate potentials and nerve evoked muscle twitches were observed in frog nerve-skeletal muscle preparations. 4. Cholinesterase activity was not inhibited. 5. The results suggest that the compound has actions at the post-synaptic muscarinic receptor complex in smooth muscle and causes pre-synaptic increases in ACh release at the neuromuscular junction.  相似文献   
999.
Absorption mechanism and absorption site of a prodrug of L-DOPA, L-3-(3-hydroxy-4-pivaloyloxyphenyl)alanine (NB-355, 1) was investigated using rats. Prodrug 1 (0.5 mM) was taken up by intestinal tissue segments time-dependently in vitro at pH 6.0. However, the rate of uptake was less than that of L-dopa. Inhibitors of the amino acid active transport system (L-Phe, dinitrophenol, ouabain) had no effect on the uptake of prodrug 1. In the intestinal tissue segments, prodrug 1 was extensively hydrolyzed by diisopropylfluorophosphate-sensitive esterase(s). To characterize the absorption site, gastrointestinal tracts were ligated to make acute loops in situ and prodrug 1 or L-dopa was injected into the loops. L-dopa disappeared rapidly from the lumen of the jejunum. In contrast, prodrug 1 disappeared rapidly from the ileum rather than the duodenum or jejunum. From these results, it was suggested that prodrug 1 was slowly absorbed primarily from the lower small intestine.  相似文献   
1000.
Mortality prognostic factors in chest injury   总被引:2,自引:0,他引:2  
1,026 multiple trauma patients (P) were compared to P with chest injuries (PCT) (407). Severity indices were related to type of thoracic injury and mortality. The Injury Severity Score (ISS), Glasgow Coma Scale (GCS), Trauma Score (TS), CHOP, and the Respiratory Index (RI) were used. The mortality rate of P was 27.1% but increased to 32.9% for PCT (p less than 0.05). We noted that mortality rate was highly dependent on major chest trauma: 68.6% for flail chest (FC), 56% for lung contusion (LC), 42.3% for hemothorax (HA), and 38.1% for pneumothorax (PN). ISS and RI scores for PCT survivors were greater than ISS + RI scores for P survivors (p less than 0.05 and p less than 0.01). ISS values for LC, HA, and PN PCT survivors were greater than the ISS of P survivors (p less than 0.01). Nonsurviving PCTs, especially those with lung contusion, showed a highly significant increase in ISS and RI scores.  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