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   6613篇
  免费   342篇
  国内免费   31篇
耳鼻咽喉   30篇
儿科学   80篇
妇产科学   90篇
基础医学   1003篇
口腔科学   57篇
临床医学   610篇
内科学   1207篇
皮肤病学   145篇
神经病学   748篇
特种医学   381篇
外科学   1119篇
综合类   18篇
一般理论   1篇
预防医学   230篇
眼科学   100篇
药学   481篇
中国医学   8篇
肿瘤学   678篇
  2023年   29篇
  2022年   59篇
  2021年   90篇
  2020年   74篇
  2019年   101篇
  2018年   122篇
  2017年   117篇
  2016年   154篇
  2015年   153篇
  2014年   207篇
  2013年   271篇
  2012年   367篇
  2011年   451篇
  2010年   268篇
  2009年   276篇
  2008年   433篇
  2007年   478篇
  2006年   446篇
  2005年   482篇
  2004年   460篇
  2003年   456篇
  2002年   399篇
  2001年   105篇
  2000年   56篇
  1999年   83篇
  1998年   94篇
  1997年   77篇
  1996年   53篇
  1995年   50篇
  1994年   46篇
  1993年   45篇
  1992年   28篇
  1991年   28篇
  1990年   23篇
  1989年   29篇
  1988年   27篇
  1987年   16篇
  1985年   24篇
  1984年   17篇
  1983年   15篇
  1982年   20篇
  1981年   23篇
  1980年   19篇
  1979年   19篇
  1978年   23篇
  1977年   22篇
  1976年   26篇
  1975年   16篇
  1974年   14篇
  1973年   16篇
排序方式: 共有6986条查询结果,搜索用时 0 毫秒
31.
There is some controversy over the treatment of acromioclavicular injuries. The use of the Rockwood classification as the basis for decisions on whether operative or nonoperative treatment is indicated is discussed critically, and the authors' preferred operative technique is described and illustrated by examples. We treat injuries classified according to the Rockwood classification as types I and II with conservative methods. In type III injuries the patient's age, job and free time activities determine whether or not surgery is indicated. In the case of type IV or type VI injuries we always perform temporary internal fixation of the acromioclavicular joint, using transarticular K-wire fixation or hookplate osteosynthesis. Satisfactory results of both operative and nonoperative treatment are reported in the literature. The authors' own results are presented.  相似文献   
32.
The present study was conducted to test the hypothesis that cholinergic basalforebrain neurons are a major source of cerebrospinal fluid (CSF) cholinesterases. To address thisquestion enzyme activities of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inboth CSF and parietal cortex were assayed following selective lesion of basal forebrain cholinergicneurons by a single intracerebroventricular application of the cholinergic immunotoxin192IgG-saporin. Cholinergic immunolesions led to a dramatic decrease in total AChE activity inparietal cortex, which was due to the specific loss of the G4 molecular form while the activity ofthe G1 form was increased as compared to nonlesioned animals. In contrast, the total enzymeactivity of BChE and its molecular forms were not affected by cholinergic lesion in both parietalcortex and CSF. The data suggest, that cholinergic basal forebrain neurons are seemingly not amajor source of cholinesterases in the CSF, and do not provide any evidence for using CSFcholinesterases as a diagnostic marker of basal forebrain cholinergic cell loss in humans.  相似文献   
33.
The impact of social defeat on lymphocyte subpopulations and T helper subsets was investigated in Long Evans rats. CD4 T helper cell subsets with distinct functional properties and different cytokine profiles can be distinguished by using the mAbs OX-22 (anti-CD45RC) and OX-7 (anti-CD90, Thy1.1). Male intruders were exposed for 2, 6, or 48 h to aggressive resident pairs. All intruders were attacked upon introduction and were defeated as indicated by frequent display of full submissive postures. After 2 and 48 h of confrontation, drastic but differential effects on blood leukocyte numbers, CD4 and CD8a cells, and CD4 subsets were evident. However, after 6 h of confrontation most lymphocyte subset numbers corresponded to baseline levels. Focusing on CD4 subsets after 2 h of confrontation, we demonstrated that only the number of the CD45RCCD90subset declines, whereas neither the number of the CD45RC+CD90subset nor the number of the CD45RCCD90+subset (recent thymic emigrants) was influenced. Con A stimulation of sorted subsets identified the CD45RCCD90as a poor producer of IFN-γ. The data clearly demonstrate that social factors might differentially influence not only T cell subsets but also T helper cell subsets with distinct cytokine profiles in a possibly time-dependent manner. Such a stress-induced shift toward a CD45RC+CD90-dominated milieu may have important consequences in interpreting results obtained from mitogenic stimulation of blood lymphocytes and cytokine production profiles measured after such a stimulation. In addition, a shift toward a CD45RC+CD90dominance may modify the type and magnitude of immune response, at least temporarily.  相似文献   
34.
Recently, divergent reports on the role of mast cells (MC) in different glomerular diseases have brought our attention to their role in an accelerated model of anti-glomerular basement membrane (GBM) glomerulonephritis (GN). Genetically MC-deficient Kit(W)/Kit(W-v) mice, MC-reconstituted Kit(W)/Kit(W-v) mice and Kit+/+ control mice were subjected to anti-GBM GN. Kit(+/+) mice developed moderate proteinuria and glomerular damage following the induction of anti-GBM nephritis. In contrast, proteinuria and glomerular damage were dramatically increased in MC-deficient Kit(W)/Kit(W-v) mice. MC-reconstituted Kit(W)/Kit(W-v) mice showed proteinuria and glomerular damage comparable to Kit+/+ mice. A significant increase in infiltrating T cells and macrophages was detected in MC-deficient Kit(W)/Kit(W-v) mice as compared to Kit+/+ control mice and MC-reconstituted Kit(W)/Kit(W-v) mice. Accordingly, we observed an increase of TGF-beta1 mRNA in kidneys from Kit(W)/Kit(W-v) mice. Interestingly, we did not detect MC in the kidney using either Giemsa staining or RT-real-time PCR, but MC were found in the regional lymph nodes. Finally, mortality of Kit(W)/Kit(W-v) mice was significantly increased after the induction of anti-GBM GN due to uremia. Our report provides the first direct evidence that MC are protective in anti-GBM GN, possibly by modulating the influx of effector T cells and macrophages to inflammatory sites in the kidney.  相似文献   
35.
Vaccination against smallpox is again considered in order to face a possible bioterrorist threat, but the nature and the level of the immune response needed to protect a person from smallpox after vaccination are not totally understood. Therefore, simple, rapid, and accurate assays to evaluate the immune response to vaccinia virus need to be developed. Neutralization assays are usually considered good predictors of vaccine efficacy and more informative with regard to protection than binding assays. Currently, the presence of neutralizing antibodies to vaccinia virus is measured using a plaque reduction neutralization test, but this method is time-consuming and labor-intensive and has a subjective readout. Here, we describe an innovative neutralization assay based on a modified vaccinia virus Ankara (MVA) vector expressing the green fluorescent protein (MVA-gfp). This MVA-gfp neutralization assay is rapid and sensitive and has a high-throughput potential. Thus, it is suitable to monitor the immune response and eventually the efficacy of a large campaign of vaccination against smallpox and to study the vector-specific immune response in clinical trials that use genetically engineered vaccinia viruses. Most importantly, application of the highly attenuated MVA eliminates the safety concern in using the replication-competent vaccinia virus in the standard clinical laboratory.  相似文献   
36.
37.
Prostate carcinomas are one of the most common malignancies in western societies. The pathogenesis of this tumor is still poorly understood. These tumors present with two characteristic features: epithelial-mesenchymal interactions, which play a pivotal role for tumor development and most of clinically manifest cancers arise in prostate proper compared to a minority of tumors which develop in the transitional zone. Deciphering the epithelial-mesenchymal cross talk and identification of molecular pecularities of the sub-populations of cells in different zones can therefore help understanding carcinogenesis and development of new, non-invasive tools for the diagnosis and prognosis of prostate carcinomas which has remained a challenge until today. A ProteinChip array technology (SELDI = surface enhanced laser desorption ionization) has been developed recently by Ciphergen Biosystems enabling analysis and profiling of complex protein mixtures from a few cells. This study describes the analysis of approximately 500-1000 freshly obtained prostate cells by SELDI-TOF-MS (surface enhanced laser desorption ionization time-of-flight mass spectrometry). Pure cell populations of stroma, epithelium and tumor cells were selected by laser assisted microdissection. Multiple specific protein patterns were reproducibly detected in the range from 1.5 to 30 kDa in 28 sub-populations of 4 tumorous prostates and 1 control. A specific 4.3 kDa peak was increased in the prostate tumor stroma compared to normal prostate proper and transitional zone stroma and increased in prostate tumor glands compared to normal prostate proper and transitional zone glands. Coupling laser assisted microdissection with SELDI provides tremendous opportunities to identify cell and tumor specific proteins to understand molecular events underlying prostate carcinoma development. It underlines the vast potential of this technology to better understand pathogenesis and identify potential candidates for new specific biomarkers in general which could help to screen for and distinguish disease entities, i.e. between clinically significant and insignificant carcinomas of the prostate.  相似文献   
38.
We report cytogenetic findings in 19 c-Kit-positive gastrointestinal stromal tumors (GISTs) that represent a heterogenous group of mesenchymal neoplasms with respect to site, histology, and biologic behavior. All of the GISTs (5 low-risk, 11 high-risk, 3 recurrences) displayed clonal chromosomal aberrations; 15 were hypo- to near-diploid, and 4 were near-triploid and hypotetraploid. The most common abnormalities were loss of chromosomes 14 and/or 22, demonstrated in 14 GISTs irrespective of site or predominant phenotype. Ten cases (2 low-risk, 5 high-risk, 3 recurrences) were characterized by loss of both chromosomes 14 and 22, 2 cases (1 low-risk, 1 high- risk), by loss of chromosome 14; and 2 high-risk cases, by loss of chromosome 22. Additional chromosomal aberrations occurred preferentially in high-risk and recurrent GISTs, including loss of 9p and 1p in 8 cases each, loss of 15 in 6 cases, loss of 3p in 5 cases, loss of 13q and 10q in 4 cases each, loss of 19 in 3 cases, and complete or partial gains of chromosomes 5 and 4 in 2 cases each. More significantly, 5 of 6 patients with clinically aggressive GISTs, including 2 recurrences and 3 metastasing GISTs, were additionally characterized by loss of 9p; four of these had additional loss of chromosomes 1p and 15. The presented results herein indicate that loss of chromosome 14 and/or 22 is an early change in GIST tumorigenesis irrespective of site or differentiation, whereas malignant transformation and progression of GISTs appear to be associated with an increasing incidence of additional secondary aberrations.  相似文献   
39.
BACKGROUND: Human cytomegalovirus (CMV) is the most common cause of viral intrauterine infection. Primary CMV infection in early pregnancy bears a high risk of fetal damage. Accurate measurement of CMV-specific IgG avidity may help to improve the serodiagnosis of CMV-infected women by determining the time of infection and fetal outcome. OBJECTIVES: To study the performance of the CMV avidity assay with the fully automated Vidas analyzer (bioMérieux) as a function of the concentration of CMV-specific IgG present in the serum sample. STUDY DESIGN: Eighty-two serum samples were investigated from 3 clinical scenarios: 18 individuals with sera negative for CMV-specific IgG and IgM (control group), 20 pregnant women (44 samples) containing CMV-specific IgG- and IgM-antibodies suggesting acute or recent primary infection and 20 patients with evidence of past infection (CMV-IgG positive and CMV-IgM negative). RESULTS: In the group with presumed acute or recent primary infection 12 of 44 sera had CMV-specific IgG values above 100 arbitrary units (AU, bioMérieux)/ml and in these cases an increase in AI was measurable upon dilution of the serum sample. In two cases, AI's were shifted towards or above the cut-off value of AI>or=0.8, indicative of past infection. Dilution of sera which were CMV-specific IgM positive and had specific IgG concentrations of 相似文献   
40.
Poly[2-(methylsulfinyl)ethyl acrylate] ( 1 ) was synthesized as well as derivatives 14C-labelled in side groups ( 6 ) or 14C-labelled in the main chain ( 11 ). Polymer 11 with the 14C-labelled main chain was fractionated by precipitation. The η-M-relation determined by measurements of unlabelled polymers in the ultracentrifuge for comparison was used to establish the viscosimetrically determined molecular weights of the labelled fractions. After intravenous application of aqueous solutions of the polymer in rats the excretion rate up to 72 h after treatment was ascertained to ca. 50%; the concentration in the blood serum was found to be strikingly high. A tendency to reinforced storage in organs of high phagocytose activity by growing molecular weight was observed. The tumor affinity was — if at all — low.  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