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   3458篇
  免费   237篇
  国内免费   26篇
耳鼻咽喉   10篇
儿科学   86篇
妇产科学   50篇
基础医学   353篇
口腔科学   143篇
临床医学   397篇
内科学   884篇
皮肤病学   40篇
神经病学   277篇
特种医学   234篇
外科学   456篇
综合类   99篇
一般理论   1篇
预防医学   262篇
眼科学   34篇
药学   242篇
  1篇
中国医学   6篇
肿瘤学   146篇
  2023年   21篇
  2022年   47篇
  2021年   72篇
  2020年   40篇
  2019年   43篇
  2018年   78篇
  2017年   77篇
  2016年   67篇
  2015年   85篇
  2014年   118篇
  2013年   133篇
  2012年   202篇
  2011年   196篇
  2010年   117篇
  2009年   135篇
  2008年   151篇
  2007年   177篇
  2006年   185篇
  2005年   128篇
  2004年   129篇
  2003年   133篇
  2002年   135篇
  2001年   95篇
  2000年   76篇
  1999年   84篇
  1998年   53篇
  1997年   76篇
  1996年   67篇
  1995年   43篇
  1994年   49篇
  1993年   44篇
  1992年   63篇
  1991年   54篇
  1990年   57篇
  1989年   55篇
  1988年   39篇
  1987年   43篇
  1986年   34篇
  1985年   38篇
  1984年   30篇
  1983年   21篇
  1982年   23篇
  1981年   20篇
  1980年   14篇
  1979年   26篇
  1978年   14篇
  1976年   29篇
  1975年   21篇
  1971年   11篇
  1968年   12篇
排序方式: 共有3721条查询结果,搜索用时 31 毫秒
81.
Quito  FL; Beh  J; Bashayan  O; Basilico  C; Basch  RS 《Blood》1996,87(4):1282-1291
Fibroblast growth factor-4 (FGF-4), a highly mitogenic protein encoded by the k-fgf/hst oncogene, stimulates the growth of a variety of cells of mesenchymal and neuroectodermal origin. Addition of FGF-4 to human long-term bone marrow cultures increased both the cell density of the stromal layer and the number of hematopoietic colony forming cells in the cultures in a dose-dependent manner. Hematopoiesis in the stromal layer persisted for up to 8 months. Erythropoiesis was maintained for up to 4 weeks, but granulocytes were the predominant nonadherent cell type. Cultures treated with FGF had increased numbers of monocytes compared with control cultures and some CD14+, CD45+ monocytes could still be detected after 8 months of continuous culture. The addition of the growth factor increased the rate of growth of the stromal layer and appeared to delay its senescence. Subcultures made in the presence of FGF-4 had up to 10-fold increases in plating efficiency and grew as relatively uniform monolayers. These subcultures retained the capacity to support hematopoiesis for several months, while untreated subcultures, made without FGF-4, grew erratically and generally lost the capacity to support hematopoiesis within 4 to 6 weeks. The improved growth after subculture greatly enhanced the reliability of limit- dilution assays of multipotential hematopoietic stem cells that use stromal cell monolayers. The primary effect of FGF-4 appeared to be on the stromal cells of the long-term bone marrow cultures, but a direct effect on hematopoietic progenitors could not be ruled out.  相似文献   
82.
83.
84.
International Journal of Legal Medicine - This study aimed to evaluate the accuracy and precision of the Cameriere European formula, Demirjian, Haavikko, and Willems methods for estimating dental...  相似文献   
85.
This study characterizes a syndrome of partial common bile duct obstruction and marked elevation in serum alkaline phosphatase in 6 male alcoholic patients with calcific pancreatitis. In each patient, a marked elevation in serum alkaline phosphatase was associated with minimal, if any, elevation in serum bilirubin. In all cases, the alkaline phosphatase was hepatic in origin, and intravenous or operative cholangiography showed a dilated common bile duct. Liver biopsy showed canalicular bile stasis in 4 patients and bile duct proliferation in 2 patients. This study demonstrates that calcific pancreatitis may cause partial bile duct obstruction which differentially increases serum alkaline phosphatase without altering bilirubin or bromsulphthalein excretion.  相似文献   
86.
OBJECTIVE: To seek an association between articular chondrocalcinosis (AC) and calcification of the transverse ligament of the atlas (TLA), and to evaluate the frequency and the main computed tomography appearances of such calcification. METHODS: Axial computed tomography slices of the cervico-occipital hinge were performed routinely in 21 patients with AC (three men, 18 women; mean age 79 years, range 67-87) and compared with those from a control group of 21 age and gender matched patients without AC. RESULTS: Calcification of the TLA was present in 14 of the 21 patients (66%) in the AC group and in none of the 21 patients (0%) in the control group (chi 2 test: p < 0.001). Calcification was localised behind the odontoid process, inserted upon the osseous tubercles of the lateral masses of C1, and had a curvilinear profile; it varied in height (1.5 to 9 mm) and appearance (thin = < 1 mm; thick = > 1 mm) and formed either a single or a double band. CONCLUSION: This study has demonstrated a relationship between AC and calcification of the TLA. Although such calcification often remains asymptomatic (nine of 14 patients in our study), it may be associated with attacks of acute neck pain with segmentary stiffness, fever, and an increased erythrocyte sedimentation rate, sometimes revealing AC.  相似文献   
87.
88.
The aim of this work was to investigate the first step in the vectorial translocation of bile acids from the fetus to the mother, which is the transfer across the basal (i.e., fetal-facing) plasma membrane of the trophoblast. Thus, the uptake of [14C]taurocholate by basal plasma membrane vesicles obtained from normal human term placentas was studied. Taurocholate retention into vesicles was studied using a rapid filtration technique that was modified to reduce the taurocholate binding to the filters and to the external surface of the vesicles. Using 100 mumol/L substrate, the membrane vesicles showed a temperature-dependent, Na(+)-independent transport of taurocholate into an osmotically reactive intravesicular space. The initial rate of taurocholate influx in the presence of 100 mmol/L KNO3 followed saturation kinetics (apparent Km for taurocholate = 670 +/- 128 mumol/L; Vmax = 1.86 +/- 0.28 nmol/mg protein.60 s at 37 degrees C). Over the 6.9-7.9 pH range neither internal nor external pH nor inward nor outward proton gradients affected the uptake of taurocholate. When the electrical potential difference across the basal membrane was manipulated by external anion replacement (Cl-, SCN-, SO4(2-), or NO3-) or by valinomycin-induced K(+)-diffusion potential (vesicle inside negative), taurocholate uptake was not significantly modified. Taurocholate uptake was cis-inhibited in the presence of 1 mmol/L glycocholate, 0.5 mmol/L 4,4'-diisothiocyanostilbene-2,2'-disulfonate and 0.5 mmol/L sulfobromophthalein. However, 1 mmol/L probenecid or 0.5 mmol/L p-aminohippurate had no effect. Moreover, preloading the vesicles with 100 mmol/L HCO3- (but not with 100 mmol/L Cl- or 50 mmol/L SO4(2-) induced a significant enhancement in the initial rate of taurocholate uptake. In summary, these findings provide strong evidence for the presence of an electroneutral transport system for taurocholate in the basal plasma membrane of human chorionic trophoblast. They also suggest that this is likely to be an anion-exchange system.  相似文献   
89.
BackgroundRecurrent respiratory papillomatosis (RRP) is a respiratory tract disease that affects children and adults and is characterized by the recurrent proliferation of multiple papillomas. The etiologic agent is the human papillomavirus, mainly genotypes 6 and 11. Furthermore, polymorphisms in TAP1 appear to influence the selection of antigenic peptides and the transport process to the rough endoplasmic reticulum, for their subsequent presentation to T lymphocytes, an essential process against viral diseases and tumor processes. Previous studies have shown that individuals with those polymorphisms are susceptible to immune, infectious, and tumor‐related diseases. The present study aimed to determine the association between the TAP1 rs1057141 (c.1177A>G) and rs1135216 (c.2090A>G) single nucleotide polymorphisms (SNPs) and RRP.MethodsA case–control study was carried out on a group of 70 individuals (35 controls and 35 patients). RRP diagnosis, HPV genotyping, and viral load were determined through histology and PCR. SNPs rs1057141 and rs1135216 were identified through allelic discrimination, using real‐time PCR. The haplotypic analyses were performed using the Arlequin 3.5 program.ResultsHPV‐6 and HPV‐11 were the genotypes found in the samples. In the polymorphism analysis, rs1057141 showed no significant differences (p = 0.049, CI = 0.994–7.331). In contrast, a significant difference was found in rs1135216 (p = 0.039, OR = 2.4) in the allelic analysis, as well as in the dominant (p = 0.027, OR = 3.06), codominant (p = 0.033, OR = 3.06), and additive model (p = 0.043, OR = 2.505) in subjects with the G allele.ConclusionThe G allele in rs1135216 was associated with a genetic risk of susceptibility for RRP in a population in Western Mexico.  相似文献   
90.
Treatment guidelines state that cognitive–behavioral therapy (CBT) and interpersonal therapy are the best-supported psychotherapies for bulimia nervosa (BN) and that CBT is the preferred psychological treatment for binge eating disorder (BED). However, no meta-analysis which both examined direct comparisons between psychological treatments for BN and BED and considered the role of moderating variables, such as the degree to which psychotherapy was bona fide, has previously been conducted Thus, such an analysis was undertaken. We included 77 comparisons reported in 53 studies. The results indicated that: (a) bona fide therapies outperformed non-bona fide treatments, (b) bona fide CBT outperformed bona fide non-CBT interventions by a statistically significant margin (only approaching statistical significance for BN and BED when examined individually), but many of these trials had confounds which limited their internal validity, (c) full CBT treatments offered no benefit over their components, and (d) the distribution of effect size differences between bona fide CBT treatments was homogeneously distributed around zero. These findings provide little support for treatment specificity in psychotherapy for BN and BED.  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