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   293篇
  免费   9篇
耳鼻咽喉   1篇
儿科学   12篇
妇产科学   7篇
基础医学   43篇
口腔科学   3篇
临床医学   15篇
内科学   55篇
皮肤病学   6篇
神经病学   13篇
特种医学   7篇
外科学   25篇
综合类   2篇
预防医学   56篇
眼科学   6篇
药学   6篇
肿瘤学   45篇
  2023年   2篇
  2022年   4篇
  2021年   3篇
  2020年   2篇
  2019年   8篇
  2018年   6篇
  2017年   5篇
  2016年   6篇
  2015年   8篇
  2014年   4篇
  2013年   19篇
  2012年   20篇
  2011年   18篇
  2010年   17篇
  2009年   6篇
  2008年   17篇
  2007年   10篇
  2006年   7篇
  2005年   18篇
  2004年   11篇
  2003年   6篇
  2002年   3篇
  2001年   3篇
  2000年   9篇
  1999年   8篇
  1995年   3篇
  1994年   2篇
  1993年   3篇
  1992年   3篇
  1991年   7篇
  1990年   9篇
  1989年   4篇
  1988年   2篇
  1987年   3篇
  1986年   2篇
  1982年   4篇
  1978年   3篇
  1977年   3篇
  1974年   3篇
  1972年   2篇
  1971年   2篇
  1970年   3篇
  1969年   4篇
  1942年   2篇
  1940年   2篇
  1908年   1篇
  1906年   1篇
  1899年   1篇
  1896年   1篇
  1890年   1篇
排序方式: 共有302条查询结果,搜索用时 15 毫秒
1.
This study examined the effects of acute and chronic ethanol on cortical somatosensory-evoked potentials (SEPs) of laboratory rats. Evoked potentials were recorded following stimulation of the left hindpaw before and after injection of either saline or ethanol. Animals were then chronically exposed to ethanol in vapor inhalation chambers for five weeks. Recordings of SEPs before and after acute ethanol injection were then obtained 24 h and again seven days after withdrawal from ethanol exposure. The results indicate that acute ethanol produced a dose-dependent reduction in SEP amplitude, but did not alter peak latencies. Chronic ethanol exposure and withdrawal resulted in a significant increase in preinjection baseline response amplitudes when measured at 24 h after withdrawal, but not at seven days, and this treatment did not alter response latency or the effects of acute ethanol administration.  相似文献   
2.
A versatile and practical semi-automatic computerized system of karyotype analysis has been developed for phylogenetic cytotaxonomy for under $4,000. The modular software system is designed for use solely with a small 8-bit microcomputer and requires virtually no custom made hardware. The system interacts with the operator and greatly augments the speed and accuracy of cytotaxonomic investigations.  相似文献   
3.
Two different classes of neoplastic T cells were isolated from radiation leukemia virus (RadLV)-inoculated and from X-ray-treated C57BL/6 mice. One consisted of growth factor-dependent T-cell lymphoma (FD-TCL) lines which were established from the spleens and thymuses of treated mice within a day of lymphoma detection. FD-TCL cells were often eudiploid and could be grown in pure culture only at high concentrations, or on stromal feeder layers. Non-thymic, factor-dependent TCL cells produced interleukin-2 upon lectin stimulation, and were autostimulatory because they secreted growth factor(s) constitutively. Single cell cloning of FD-TCL cells in semisolid medium required the addition of exogenous conditioned medium. In vivo, FD-TCL cells that were injected intraperitoneally or intravenously homed to the spleen, proliferated in it and killed the injected mice. FD-TCL cells did not produce local tumors at the site of subcutaneous injection. The isolation and study of FD-TCL cells was facilitated by their cultivation on stromal hematopoietic monolayers in supplemented "lymphocyte medium", until an autostimulating, self-sustaining concentration of FD-TCL cells was obtained. FD-TCL cells could not be grown from lymphoid tissue of normal, control mice. In contrast, T-cell lymphoma (TCL) lines, which were established from virus-induced thymomas which had been kept in situ for 4-6 weeks after detection, consisted of factor-independent cells that possessed an aneuploid karyotype (in some cases trisomic for chromosome No. 15), and produced local tumors at the site of subcutaneous injection. These cells could be cloned in semisolid medium without addition of exogenous factor(s). The phenotypic markers of TCL cells differed from those of FD-TCL cells, suggesting heterogeneity in the stages of differentiation at which cells can give rise to growth factor-independent (TCL) and to growth factor-dependent (FD-TCL) lines.  相似文献   
4.
Mazur  EM; Cohen  JL; Bogart  L 《Blood》1988,71(6):1544-1550
Peripheral blood mononuclear cells from five patients with essential thrombocythemia (ET) were cultured in vitro to evaluate restricted megakaryocytic (CFU-Meg), myeloid (CFU-GM), and erythroid (BFU-E) progenitor cell development. Varying concentrations of aplastic canine serum served as the source of megakaryocyte colony-stimulating activity, and cultured megakaryocyte ploidy distributions were determined by Feulgen staining and microfluorometry. Megakaryocyte colony growth was strikingly abnormal in all five patients evaluated. Four of the 5 had a marked expansion in the concentration of circulating CFU-Meg and 3 of 4 manifested abnormalities in cultured megakaryocyte colony size (2 unusually large and 1 small). Unstimulated megakaryocyte colony growth was substantially increased in three patients. However, the fraction of megakaryocyte progenitors in cell cycle was near or below normal in all instances. Endomitotic megakaryocyte development was disordered in each of the four ET patients in whom it was evaluable. In normal subjects, mean megakaryocyte ploidy values vary biphasically with aplastic canine serum concentration and peak at 13.2 N following 12 to 15 days of culture. In contrast, day 12 mean ploidy values in cultures from the ET patients remained low at all aplastic canine serum concentrations and reached a maximum averaging only 8.4 N. Three patients were evaluated serially at extended culture durations of up to 21 days. The cultured megakaryocyte ploidy was unchanged during this interval for two of the patients. For the third patient, ploidy increased steadily, reaching abnormally high ploidy values by day 21. Progenitor cell expansion was limited to the megakaryocyte line in three patients. However, two patients had substantial increases in CFU-GM, one of whom also had a marked increase in BFU-E. There was no significant unstimulated colony growth by either CFU-GM or BFU-E. These data indicate that ET is usually characterized by an expansion in the concentration of circulating CFU-Meg in vivo which manifest both disordered replication and endoreduplication in vitro.  相似文献   
5.
This report describes a prospective randomized trial of 503 patients who underwent a cardiac catheterization or interventional procedure at a single institution. In an effort to study femoral complications postprocedure, we evaluated three methods of femoral artery hemostasis as well as 38 variables that were felt to potentially relate to local complications. Only a marginally significant relationship between the hemostasis method and complication rate was found. The factors that contributed to femoral artery complications were: restarting heparin postsheath removal, number of procedures done during one hospitalization, noncompliance of the patient with bedrest after the procedure, number of arterial punctures to initiate the procedure, and preprocedure treatment with corticosteroids.  相似文献   
6.
We examined the interconnectedness of stigma experiences in families living with HIV, from the perspective of multiple family members. Semi-structured interviews were conducted with 33 families (33 parents with HIV, 27 children under age 18, 19 adult children, and 15 caregivers). Parents were drawn from the HIV Cost and Services Utilization Study, a representative sample of people in care for HIV in US. All of the families recounted experiences with stigma, including 100% of mothers, 88% of fathers, 52% of children, 79% of adult children, and 60% of caregivers. About 97% of families described discrimination fears, 79% of families experienced actual discrimination, and 10% of uninfected family members experienced stigma from association with the parent with HIV. Interpersonal discrimination seemed to stem from fears of contagion. Findings indicate a need for interventions to reduce HIV stigma in the general public and to help families cope with stigma.  相似文献   
7.
Human chorionic gonadotropin levels in pregnancies with aneuploid fetuses   总被引:1,自引:0,他引:1  
Maternal serum human chorionic gonadotropin (hCG) and the free alpha-hCG subunit were evaluated in 249 women from 9 to 11 weeks gestation who subsequently underwent chorionic villus sampling for determination of fetal karyotype and in 20 women of 18 or more weeks gestation who were ascertained to have an aneuploid fetus by genetic amniocentesis. Seven of the first-trimester pregnancies were determined to be aneuploid and six had hCG levels in the normal range (one triploid pregnancy had elevated hCG levels) whereas 12 of the 20 second-trimester cases had abnormal hCG levels and an additional three had elevated levels of alpha-hCG. This study confirms the previous report of abnormal maternal serum hCG levels in women with an aneuploid fetus at greater than or equal to 18 weeks gestation and demonstrates that hCG evaluation is not useful at 9-11 weeks gestation for selecting pregnancies at risk for fetal aneuploidy.  相似文献   
8.
OBJECTIVES: The purpose of this study was to examine perceived race-based discrimination in obtaining family planning or contraceptive services among African American women in the U.S. METHODS: We conducted a 30-minute telephone survey with a random sample of 500 African Americans (aged 15-44), which included questions about race-based discrimination when obtaining family planning services. The present analyses were limited to the 326 women who completed interviews. RESULTS: The majority (79%) of women reported having seen a health care provider for family planning or birth control services. Of those, 67% reported race-based discrimination when obtaining such services. Half of the women reported more general experiences of discrimination when obtaining family planning services (e.g., poorer service), and 52% reported experiences that reflect stereotypes of African American women (e.g., doctor or nurse assumed they had multiple sexual partners). Most indicated that experiences of discrimination occurred infrequently. Generally, background characteristics were not significantly associated with perceived discrimination. However, in multivariate models, stronger Black identity, younger age, and lower income were associated with reports of discrimination. CONCLUSION: African American women may be vulnerable to prejudice within reproductive health care contexts, including family planning.  相似文献   
9.
Transgenic mouse models have been essential for understanding the pathogenesis of Alzheimer's disease (AD) including those that model the deposition process of beta-amyloid (Abeta). Several laboratories have focused on research related to the non-invasive detection of early changes in brains of transgenic mouse models of Alzheimer's pathology. Most of this work has been performed using regional image analysis of individual mouse brains and pooling the results for statistical assessment. Here we report the implementation of a non-linear image registration algorithm to register anatomical and transverse relaxation time (T2) maps estimated from MR images of transgenic mice. The algorithm successfully registered mouse brain magnetic resonance imaging (MRI) volumes and T2 maps, allowing reliable estimates of T2 values for different regions of interest from the resultant combined images. This approach significantly reduced the data processing and analysis time, and improved the ability to statistically discriminate between groups. Additionally, 3D visualization of intra-regional distributions of T2 of the resultant registered images provided the ability to detect small changes between groups that otherwise would not be possible to detect.  相似文献   
10.
Background: Prior research concerning the effects of occupational status and work stress on ambulatory blood pressure (AmBP) has seldom included women, and available results are equivocal. Moreover, the concurrent effects of occupational status and job characteristics have rarely been investigated. Some research is consistent with the idea that stressful job characteristics are especially detrimental to health in low-status workers, creating a cumulative physiological burden.Purpose: To examine the independent and joint effects of occupational status and perceived demands, control, and social support at work on AmBP and heart rate (HR) in women.Methods: One hundred eight women (M age = 41.07 years) wore an AmBP monitor for 2 days and completed a self-report assessment of job control, demands, and support (i.e., Karesek et al.’s Job Content Questionnaire).Results: After controlling for numerous potential confounds, occupational status and job characteristics accounted for 18% and 22% of the inter-individual variability in ambulatory systolic blood pressure (SBP) and HR, respectively. Occupational status independently predicted ambulatory cardiovascular activity and interacted with job characteristics, particularly in relation to SBP.Conclusions: Inasmuch as ambulatory SBP and HR predict future cardiovascular morbidity and mortality, women with both lower status occupations and stressful job circumstances could be at disproportionately high cardiovascular risk. Laura Bogart is now with RAND Corporation, Santa Monica, California. This research was supported in part by a Kent State University Summer Research and Creativity Grant and by NIH Grant MH66101-01. We thank Amy Jones and Evangelia Banou for assistance with data collection and data entry.  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