全文获取类型
收费全文 | 5669篇 |
免费 | 407篇 |
国内免费 | 18篇 |
专业分类
耳鼻咽喉 | 73篇 |
儿科学 | 241篇 |
妇产科学 | 134篇 |
基础医学 | 807篇 |
口腔科学 | 59篇 |
临床医学 | 760篇 |
内科学 | 986篇 |
皮肤病学 | 94篇 |
神经病学 | 480篇 |
特种医学 | 299篇 |
外科学 | 700篇 |
综合类 | 126篇 |
一般理论 | 3篇 |
预防医学 | 452篇 |
眼科学 | 140篇 |
药学 | 357篇 |
中国医学 | 4篇 |
肿瘤学 | 379篇 |
出版年
2021年 | 83篇 |
2020年 | 54篇 |
2019年 | 89篇 |
2018年 | 89篇 |
2017年 | 73篇 |
2016年 | 74篇 |
2015年 | 117篇 |
2014年 | 102篇 |
2013年 | 182篇 |
2012年 | 238篇 |
2011年 | 250篇 |
2010年 | 159篇 |
2009年 | 141篇 |
2008年 | 208篇 |
2007年 | 224篇 |
2006年 | 238篇 |
2005年 | 218篇 |
2004年 | 236篇 |
2003年 | 199篇 |
2002年 | 206篇 |
2001年 | 171篇 |
2000年 | 163篇 |
1999年 | 191篇 |
1998年 | 91篇 |
1997年 | 70篇 |
1996年 | 69篇 |
1995年 | 63篇 |
1994年 | 55篇 |
1993年 | 43篇 |
1992年 | 113篇 |
1991年 | 100篇 |
1990年 | 116篇 |
1989年 | 115篇 |
1988年 | 101篇 |
1987年 | 101篇 |
1986年 | 111篇 |
1985年 | 90篇 |
1984年 | 69篇 |
1983年 | 55篇 |
1982年 | 45篇 |
1981年 | 46篇 |
1979年 | 83篇 |
1978年 | 59篇 |
1977年 | 55篇 |
1976年 | 52篇 |
1975年 | 43篇 |
1974年 | 47篇 |
1973年 | 55篇 |
1972年 | 49篇 |
1969年 | 39篇 |
排序方式: 共有6094条查询结果,搜索用时 0 毫秒
41.
Harvey M.B.; Leco K.J.; Arcellana-Panlilio M.Y.; Zhang X.; Edwards D.R.; Schultz G.A. 《Human reproduction (Oxford, England)》1995,10(3):712-718
Several growth factor ligand and receptor gene products havebeen shown to play roles during preimplantation mammalian development.Genes for insulin-like growth factors (IGFs), transforming growthfactors (TGFs), fibroblast growth factor (FGF), platelet-derivedgrowth factor (PDGF) and receptors for insulin, IGF, PDGF, TGFand epidermal growth factor (EGF) are expressed by early embryosof several species including mouse, rat, cow and sheep. Rolesof growth factors during early development have been demonstratedby addition of purified growth factors to culture medium orby molecular genetic techniques that interfere with gene expression.In this way, it has been shown that successful development ofthe blastocyst is dependent on the action of epidermal growthfactor (EGF) and leukaemia inhibitory factor (LIF). Recent experimentsshow that both LIF and EGF stimulate secretion of urokinase-typeplasminogen activator (uPA) and gelatinase B/ matrix metalloproteinase-9(MMP-9) in day 7 mouse blastocyst outgrowths. At the same time,tissue inhibitors of MMPs (TIMPs) are also expressed by embryonic,decidual and uterine tissues during the implantation process.It appears that LIF may act directly or indirectly, by inducingthe expression of other cytokines, to regulate the temporaland spatial production and activity of proteases and proteaseinhibitors to create a favourable environment for implantation. 相似文献
42.
James L M Ferrara Claudio Anasetti Edward Stadtmauer Joseph Antin John Wingard Stephanie Lee John Levine Kirk Schultz Frederick Appelbaum Robert Negrin Sergio Giralt Christopher Bredeson Helen Heslop Mary Horowitz 《Biology of blood and marrow transplantation》2007,13(11):1268-1285
Outcomes of hematopoietic cell transplantation are steadily improving. New techniques have reduced transplant toxicities, and there are new sources of hematopoietic stem cells from unrelated donors. In June 2007 the Blood and Marrow Transplant Clinical Trials Network convened a State of the Science Symposium of more than 200 participants in Ann Arbor to identify the most compelling clinical research opportunities in the field. This report summarizes the symposium's discussions and identifies eleven high priority clinical trials that the network plans to pursue over the course of the next several years. 相似文献
43.
The actions of prolonged treatment of rats within imipramine or lithium chloride on the β-adrenergic cAMP generating system of the cerebellum were compared in normal animals and in rats degranulated by neonatal X-irradiation. Whereas in normal animals imipramine treatment is without significant effect on the cerebellar cAMP system but lowers the β-adrenoceptor density significantly, in degranulated animals the cAMP system becomes subsensitive towards norepinephrine after prolonged imipramine treatment. These data support the hypothesis that in the cerebellum imipramine acts predominantly on β-adrenoceptors located particularly on Purkinje cells. Prolonged lithium treatment exhibited no significant effects on β-receptors nor the noradrenergic cAMP generating system of normal and degranulated cerebella. 相似文献
44.
Janice S. Lee Carol W. Bassim Harvey Kushner Ann G. Carr Pamela J. Gardner Laura A. Harney Kris Ann P. Schultz Douglas R. Stewart 《American journal of medical genetics. Part A》2019,179(9):1820-1825
Pathogenic germline variation in the microRNA processing gene DICER1 gives rise to an autosomal dominant, tumor‐predisposition disorder. Conditional deletion of Dicer1 in murine dental epithelium shows that it controls tooth patterning, size, number, and shape. The human dental phenotype of people with germline pathogenic variation in DICER1 is unknown. DICER1‐carriers (n = 57) and family controls (n = 55) were evaluated at the NIH Clinical Center dental clinic as part of a comprehensive medical evaluation. Digital panoramic radiographs, bite‐wing radiographs, and oral photographs were collected. A single observer, blind to DICER1 status, reviewed the dental records and determined the presence or absence of 11 dental characteristics as described in the clinic notes, radiographs, or oral photographs. Subjective phenotypes were reviewed on radiographs by two examiners (blind to DICER1 status) for the presence or absence of the dental characteristics to reduce inconsistencies. By simple association, bulbous crown, periodontitis, and taurodontism were all significant (p < .05). Logistic regression with chi‐square maximum likelihood estimates showed that bulbous crown and periodontitis remained significant. Recognition of these phenotypes may aid identification of individuals and families at risk for DICER1‐associated neoplasms. These findings may also guide dental care for individuals with germline DICER1 pathogenic variation. 相似文献
45.
Natural and immune cytolysis of canine distemper virus-infected target cells. 总被引:2,自引:1,他引:2 下载免费PDF全文
Natural and immune cytolysis of canine distemper virus (CDV)-infected target cells in vitro is described. Lymphocytes expressing natural cytotoxicity were found in specific-pathogen-free beagle dogs and in beagle-coonhound crosses before vaccination with CDV and indefinitely after vaccination, when the ephemeral immune lymphocyte-mediated cytotoxicity (ILMC) had declined. In contrast to the natural lymphocyte-mediated cytotoxicity, the ILMC was genetically restricted, could not be blocked by CDV-specific antibody, and was effective against measles virus-infected as well as CDV-infectd target cells. Lymphocyte populations were depleted of Fc receptor and surface immunoglobulin-bearing cells by rosetting techniques and tested in comparison. An antibody-dependent cell-mediated cytotoxicity was demostrated against CDV-infected target cells that were preincubated with CDV antibody when Fc receptor-bearing lymphocytes were not removed. The ILMC was measurable for approximately 10 days beginning at 6 days post-vaccination. In contrast, CDV antibody measured by virus neutralization and humoral cytotoxicity was detectable by 6 days postvaccination and persisted at peak levels for at least 5 months. 相似文献
46.
In this second of three articles exploring Engel's biopsychosocial model, five case histories illustrate how psychological factors, sometimes related to organic trauma or illness, may precipitate psychiatric conditions. The patients’ disorders, and their management by a consultation-liaison team, demonstrate the interaction of biologic, psychological, and social systems in assessment and treatment of disease. 相似文献
47.
Reward-related neuronal activity during go-nogo task performance in primate orbitofrontal cortex 总被引:8,自引:0,他引:8
The orbitofrontal cortex appears to be involved in the control of voluntary, goal-directed behavior by motivational outcomes. This study investigated how orbitofrontal neurons process information about rewards in a task that depends on intact orbitofrontal functions. In a delayed go-nogo task, animals executed or withheld a reaching movement and obtained liquid or a conditioned sound as reinforcement. An initial instruction picture indicated the behavioral reaction to be performed (movement vs. nonmovement) and the reinforcer to be obtained (liquid vs. sound) after a subsequent trigger stimulus. We found task-related activations in 188 of 505 neurons in rostral orbitofrontal area 13, entire area 11, and lateral area 14. The principal task-related activations consisted of responses to instructions, activations preceding reinforcers, or responses to reinforcers. Most activations reflected the reinforcing event rather than other task components. Instruction responses occurred either in liquid- or sound-reinforced trials but rarely distinguished between movement and nonmovement reactions. These instruction responses reflected the predicted motivational outcome rather than the behavioral reaction necessary for obtaining that outcome. Activations preceding the reinforcer began slowly and terminated immediately after the reinforcer, even when the reinforcer occurred earlier or later than usually. These activations preceded usually the liquid reward but rarely the conditioned auditory reinforcer. The activations also preceded expected drops of liquid delivered outside the task, suggesting a primary appetitive rather than a task-reinforcing relationship that apparently was related to the expectation of reward. Responses after the reinforcer occurred in liquid- but rarely in sound-reinforced trials. Reward-preceding activations and reward responses were unrelated temporally to licking movements. Several neurons showed reward responses outside the task but instruction responses during the task, indicating a response transfer from primary reward to the reward-predicting instruction, possibly reflecting the temporal unpredictability of reward. In conclusion, orbitofrontal neurons report stimuli associated with reinforcers are concerned with the expectation of reward and detect reward delivery at trial end. These activities may contribute to the processing of reward information for the motivational control of goal-directed behavior. 相似文献
48.
Six hundred fifty-eight cases of previously untreated non-Hodgkin's lymphoma seen between 1970 and 1979 at the Medical Department, the Finsen Institute, were the basis for a comparative study of the prognostic value of the Rappaport, Kiel, and Lukes & Collins classifications and the new translation system, the Working Formulation of Non-Hodgkin's Lymphoma. Each histopathologic system proved equally effective in separating patients into subgroups with a spectrum of prognoses ranging from a median survival of less than 1 year to greater than 7 years. The established classifications were compared with the Working Formulation in order to evaluate its translational value. The Working Formulation was more similar to the Rappaport and the Lukes & Collins systems than to the Kiel system, since 82%, 89%, and 75% of the cases, respectively, were translatable following the guidelines outlined in the National Cancer Institute (NCI)-sponsored study. Similarities among the four systems were demonstrated in lymphomas with follicular growth pattern, and in diffuse lymphomas composed of small mature appearing lymphocytes or small cleaved lymphocytes. Incongruity among the systems was more marked in lymphomas composed of large lymphoid cells or in lymphomas of mixed cellular composition. A comparison was performed for each classification against the Working Formulation. All such subdivided subsets were tested for prognostic heterogeneity and the following conclusions were reached: the diffuse poorly differentiated lymphocytic category of Rappaport was separated into two subgroups (malignant lymphoma [ML] small cleaved cell and ML lymphoblastic) with different prognoses (P = 0.01); the diffuse "histiocytic" lymphomas were prognostically homogeneous, since none of the newer systems were able to identify subpopulations with significantly different prognoses; the subtypes of the Kiel classification were prognostically homogeneous; the only weakness of the Lukes & Collins classification was the undefined cell subtype, encompassing two populations with different prognoses; and (5) the importance of follicular growth pattern was confirmed for small cleaved cell and mixed cell cytology, whereas large cell cytology implied a poor prognosis regardless of pattern. By the use of the Cox regression model it could be demonstrated that the Working Formulation can substitute any of the established classifications in terms of prognostic value. 相似文献
49.
IntroductionPatients with traumatic brain injury are referred to the neurosurgical unit at James Cook University Hospital, Middlesbrough, either from local accident and emergency departments (direct transfer from the scene) or from other hospitals (indirect transfer). This study looked at the outcome in both groups.Material and methodsThis was a retrospective observational study using trauma audit research network data for patients treated for traumatic brain injury at the neurosurgery department at the neurosurgical unit at James Cook University Hospital.ResultsA total of 356 patients with traumatic brain injury were admitted under the care of neurosurgeons; 143 (40%) of these patients had a neurosurgical procedure. Of the patients undergoing a neurological procedure, 111 patients were transferred directly while 32 were indirect transfers; 213 patients were managed conservatively. Of those managed conservatively, 165 were transferred directly while 48 were indirect transfers.We compared the length of hospital stay and Glasgow Outcome Scale score for the patients based on whether they were conservatively managed or required surgery in the direct and indirect transfer groups. The difference in the length of stay in the surgical and conservative groups following direct and indirect transfer was insignificant (p = 0.07). The time to the operation in direct and indirect transfer was also not statistically significant (p = 0.06).ConclusionPatients are as safe, if not safer, by reaching the nearest trauma unit with facilities for resuscitation and imaging. 相似文献