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   6126篇
  免费   674篇
  国内免费   11篇
耳鼻咽喉   113篇
儿科学   145篇
妇产科学   167篇
基础医学   799篇
口腔科学   83篇
临床医学   873篇
内科学   1113篇
皮肤病学   67篇
神经病学   572篇
特种医学   201篇
外科学   705篇
综合类   93篇
预防医学   803篇
眼科学   122篇
药学   552篇
中国医学   5篇
肿瘤学   398篇
  2021年   91篇
  2020年   57篇
  2019年   84篇
  2018年   107篇
  2017年   81篇
  2016年   80篇
  2015年   116篇
  2014年   127篇
  2013年   185篇
  2012年   274篇
  2011年   277篇
  2010年   176篇
  2009年   156篇
  2008年   245篇
  2007年   294篇
  2006年   265篇
  2005年   274篇
  2004年   232篇
  2003年   252篇
  2002年   220篇
  2001年   193篇
  2000年   229篇
  1999年   215篇
  1998年   96篇
  1997年   85篇
  1996年   81篇
  1995年   56篇
  1994年   50篇
  1993年   75篇
  1992年   161篇
  1991年   174篇
  1990年   166篇
  1989年   166篇
  1988年   151篇
  1987年   126篇
  1986年   124篇
  1985年   110篇
  1984年   75篇
  1983年   74篇
  1982年   55篇
  1981年   59篇
  1980年   59篇
  1979年   66篇
  1978年   49篇
  1976年   33篇
  1975年   33篇
  1974年   36篇
  1973年   37篇
  1972年   41篇
  1967年   33篇
排序方式: 共有6811条查询结果,搜索用时 375 毫秒
51.
This study examined the acquisition of verb particles and prepositions in language-impaired, language-matched, and age-matched preschool children. A videotape experimental task, in which subjects viewed and described brief action sequences, was implemented. The videotape task included particle, preposition, full noun phrase, and pronoun noun phrase items for six different particle/preposition words. Primary results indicated that the use of verb particles constituted a particularly challenging linguistic task for the language-impaired subjects relative to both their age- and language-matched peers. These results suggest multiple sources of difficulty for language-impaired children in the acquisition of grammatical form classes. Lexical and grammatical difficulties, as well as possible processing limitations, are implicated.  相似文献   
52.
53.
54.
A C Eddy  V W Rusch  C L Fligner  D T Reay  C L Rice 《The Journal of trauma》1990,30(8):989-91; discussion 991-2
Traumatic rupture of the thoracic aorta (TRA) is a rare but highly lethal injury in children that occurs as a result of car versus pedestrian accidents and motor vehicle accidents. TRA is often associated with life-threatening injuries to other organ systems. Therefore children with TRA like adults sustaining TRA must be treated urgently but systematically. The rarity of this injury makes it all the more important for physicians treating pediatric trauma victims to be cognizant of the importance of the injury and the clinical and radiographic signs. Even when TRA is promptly recognized in children it is associated with a high in-hospital mortality. The proper use of child restraint systems and adherence to the 55 M.P.H. speed limit may be important factors in reducing the mortality of TRA in children after MVA.  相似文献   
55.
The pathology of head and neck tumors: vasoformative tumors, part 9B   总被引:2,自引:0,他引:2  
There are three principal malignant vasoformative tumors that can be found in the head and neck--hemangiopericytoma, angiosarcoma, and Kaposi's sarcoma. All are uncommon and provide challenges for the pathologist and the therapist both. The histogenesis of each tumor is different. Kaposi's sarcoma has many features which suggest that it is an altered immune-response disease. Angiosarcoma is a malignancy of endothelium. Hemangiopericytoma is a tumor whose cell of origin is considered to be the perithelial pericyte. The general prognosis for patients with Kaposi's sarcoma is good. The biologic course of a hemangiopericytoma is variable and unpredictable, but there appears to be a site dependency. Angiosarcomas, particularly high grade lesions, are resistant to therapy.  相似文献   
56.
Promoting effects of sodium salts of phenobarbital (NaPB) and barbital (NaBB) on the development of bladder tumors were investigated in F344 male rats initiated with N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide (FANFT) or N-nitrosobutyl-4-hydroxybutylamine (BBN). To initiate with FANFT, rats were fed 0.2% FANFT mixed in diet for either 2 or 6 weeks and 2 weeks later were offered diet containing 1000 ppm of NaPB or NaBB. Rats were killed either at 52 or 68 weeks of age. To initiate with BBN, rats were given 0.05% BBN in drinking water for 4 weeks and beginning 1 day later were fed NaBB mixed in diet at 1000 ppm for up to 52 weeks. NaBB promoted bladder carcinogenesis initiated by either FANFT or BBN; the incidence and average number of simple or preneoplastic nodular (PN) hyperplasias, papillomas, and carcinomas per 10 cm of urothelium were significantly increased in the groups receiving NaBB following exposure to FANFT for 6 weeks (p less than 0.05) or BBN for 4 weeks (p less than 0.01). No such effect was seen in rats fed FANFT for only 2 weeks. NaPB also significantly increased (p less than 0.05) the frequency of preneoplastic PN hyperplasias but not the average number of papillomas and carcinomas per 10 cm of urothelium in rats fed FANFT for 6 weeks. NaBB was an effective promoter of bladder carcinogenesis under these experimental conditions, as expected from its known promoting effect on transitional epithelium of the renal pelvis, but NaPB in contrast did not affect the incidence or multiplicity of bladder papillomas or carcinomas under these conditions. NaPB could be considered a promoter for bladder urothelium only by the less rigorous criterion that it increased the frequency of preneoplastic PN hyperplasia.  相似文献   
57.
Norbinaltorphimine (nor-BNI) is a bifunctional reagent developed as a selective antagonist of the kappa opioid receptor. In this paper we examined the in vitro selectivity of nor-BNI, 6-desoxy-6 beta-fluoronaltrexone (cycloFOXY), and the enantiomer of cycloFOXY, among opioid receptor subtypes. Nor BNI exhibited the highest affinity for kappa binding sites labeled by 3H-U69593 (Ki = 1.8nM), and was 27- to 29-fold less potent at mu and delta binding sites. In contrast, cycloFOXY had the highest affinity for mu binding sites (Ki = 2.62 nM), and bound to kappa and delta binding sites with Ki's of 9.3 nM and 89 nM, respectively. The enantiomer of cycloFOXY, did not inhibit binding even at concentrations greater than 10 microM, validating in part the use of 18F-labeled (+)-cycloFOXY to estimate "non-specific binding" in positron emission tomography. Additionally, we report that (S,S)-U50 488 and (R.R)-U50 488 bind to kappa binding sites labeled by 3H-U69 593 with Ki's of 0.89 nM and 299 nM, respectively.  相似文献   
58.
In the National Institute of Mental Health Collaborative Program on the Psychobiology of Depression study, data were collected on 2226 first-degree relatives of 612 probands. A second, "blind" reassessment of all relatives was attempted 6 years after the initial evaluation. We report on a final sample of 1629 relatives assessed twice using the Schedule for Affective Disorders and Schizophrenia-Lifetime version. We summarize methods for using stability of diagnosis to model the relationship between clinical covariates and the probability of being a true case. Moreover, we define an index of caseness that can be used to narrow the criteria for who is a case. Of those positive for major depressive disorder at initial evaluation, 74% were positive (on a lifetime basis) at follow-up (ie, were stable). There is a gradient: 48% of those who had three symptoms and no treatment were stable, compared with 96% of those with eight symptoms and treatment. For major depressive disorder, we found the caseness index for those with lifetime mania more severe than that of nonbipolar patients, with those who had hypomania being intermediate. A hierarchical analysis indicated that bipolar I tends to be diagnosed as schizoaffective-manic across occasions, and vice versa. This is consistent with the prior familial analyses that suggest these two diagnoses be combined into a single bipolar phenotype. The analysis for major depressive disorder indicates that caseness appears to represent quantitative, rather than qualitative, differences, with no natural cutoff to identify distinct subgroups. Finally, we discuss implications including utility in genetic analyses, estimation of incidence or prevalence allowing for diagnostic error, and examination of cohort effects.  相似文献   
59.
Image-directed percutaneous biopsies with a biopsy gun   总被引:3,自引:0,他引:3  
Core tissue for histologic study is believed by many pathologists to be more diagnostic than material from needle aspiration. Recently, a biopsy "gun" has been introduced, which simplifies core biopsies. With this device, 182 biopsies of multiple anatomic sites were performed with ultrasonic, computed tomographic, and fluoroscopic guidance and 18-gauge needles. High-quality histopathologic specimens were obtained in 177 of the biopsies, and diagnostic target tissue was obtained in 167. Only three significant complications occurred: one bleeding complication that required transfusion and two cases of pneumothorax that necessitated placement of chest tubes. The biopsy gun eliminated the disjointed movements of conventional "skinny" needle biopsies, and none of the samples demonstrated significant "crush" artifact or obscuring blood, problems that are commonly associated with manual biopsy techniques. Patient discomfort was decreased with this system compared with that of manual biopsies, and the total procedure time was reduced. Because of these distinct advantages, the authors now use the biopsy gun exclusively for all percutaneous biopsies and recommend that other institutions consider the use of this biopsy method.  相似文献   
60.
The role of radiotherapy in small cell carcinoma of the lung is unsettled; however, the radiosensitivity of this neoplasm is unquestioned. The ability of radiotherapy to cure or improve patients with this disease is still undergoing study. A review of this challenging subject is presented.  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