全文获取类型
收费全文 | 18991篇 |
免费 | 1938篇 |
国内免费 | 29篇 |
专业分类
耳鼻咽喉 | 165篇 |
儿科学 | 695篇 |
妇产科学 | 323篇 |
基础医学 | 2635篇 |
口腔科学 | 392篇 |
临床医学 | 2008篇 |
内科学 | 3614篇 |
皮肤病学 | 494篇 |
神经病学 | 1742篇 |
特种医学 | 720篇 |
外国民族医学 | 12篇 |
外科学 | 2031篇 |
综合类 | 343篇 |
一般理论 | 25篇 |
预防医学 | 2056篇 |
眼科学 | 738篇 |
药学 | 1528篇 |
中国医学 | 12篇 |
肿瘤学 | 1425篇 |
出版年
2021年 | 259篇 |
2020年 | 154篇 |
2019年 | 320篇 |
2018年 | 310篇 |
2017年 | 225篇 |
2016年 | 262篇 |
2015年 | 339篇 |
2014年 | 429篇 |
2013年 | 617篇 |
2012年 | 833篇 |
2011年 | 898篇 |
2010年 | 497篇 |
2009年 | 473篇 |
2008年 | 728篇 |
2007年 | 730篇 |
2006年 | 738篇 |
2005年 | 745篇 |
2004年 | 784篇 |
2003年 | 683篇 |
2002年 | 642篇 |
2001年 | 635篇 |
2000年 | 678篇 |
1999年 | 543篇 |
1998年 | 257篇 |
1997年 | 252篇 |
1996年 | 231篇 |
1995年 | 225篇 |
1994年 | 192篇 |
1993年 | 188篇 |
1992年 | 430篇 |
1991年 | 433篇 |
1990年 | 426篇 |
1989年 | 426篇 |
1988年 | 380篇 |
1987年 | 433篇 |
1986年 | 356篇 |
1985年 | 361篇 |
1984年 | 287篇 |
1983年 | 271篇 |
1982年 | 170篇 |
1981年 | 157篇 |
1980年 | 161篇 |
1979年 | 283篇 |
1978年 | 222篇 |
1977年 | 159篇 |
1976年 | 165篇 |
1975年 | 164篇 |
1974年 | 182篇 |
1973年 | 173篇 |
1972年 | 171篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
101.
Connie Green 《Early child development and care》1987,28(2):129-136
This study investigated the impact of a home composing curriculum on kindergarten children's concepts about print (a measure of reading readiness), writing fluency (the number of words children can write), and writing achievement. In addition, the study investigated gender differences on the above measures, types of writing done by children at home, and family members with whom children wrote. The treatment group was found to be significantly higher on the Concepts about Print test, writing fluency, and the first post-test of writing achievement. There were no significant gender differences on any of the measures. Data from parent response sheets indicated that these children wrote notes, letters, and lists more than other types of writing. They wrote with their mother or alone more often than with other family members. The findings of this study suggest that a flexible home composing curriculum, combined with the sharing of writing at school can have an impact on reading readiness, the number of words children can write, and possibly writing ability. 相似文献
102.
Allan L. Reiss Lisa Freund Leslie Plotnick Thomas Baumgardner Kathleen Green Amanda C. Sozer Mark Reader Corinne Boehm Martha B. Denckla 《Annals of neurology》1993,34(1):95-107
Monosomy for the X chromosome is the most frequent cause of Turner's syndrome, a common clinical syndrome associated with particular physical and neurobehavioral features. The results from comprehensive assessment of prepubertal monozygotic female twins discordant for X monosomy are presented. Zygosity was established with DNA Fingerprinting and no evidence of chromosomal mosaicism was seen in either child. Physical features in the affected twin were relatively mild with respect to the full spectrum of physical malformations and disabilities associated with Turner's syndrome. The neurobehavioral phenotypes of the twins were compared. Although both sisters scored in the superior range of intelligence, the affected twin's Performance IQ was 18 points less than her sister, whereas Verbal IQ showed only a 3-point difference between the sisters. Other relative differences were noted within the executive, visuospatial, and visuomotor domains of function. Behavioral evaluation indicated greater problems with attention, hyperactivity, and anxiety in the affected twin. Quantitative analysis of brain anatomy revealed evidence of both general and regional effects of X monosomy on neurodevelopment. Cerebrospinal fluid volume was increased by 25% in the affected twin compared with her sister with a corresponding decrease in gray matter volume. The right frontal, right parietal–occipital, and left parietal-perisylvian regions showed the greatest discrepancy between the sisters with respect to increased cerebrospinal fluid and decreased gray matter volumes in the twin with X monosomy. Differences in the posterior fossa were also noted with a 50% relative increase in the volumes of the fourth ventricle and cisterna magna and a 10 to 15% relative reduction in size of the cerebellar vermis, pons, and medulla in the affected twin. The association between the neurobehavioral and neuroanatomical findings in the affected twin is discussed. The unique nature of the naturally occurring genetic phenomenon seen in this twin pair provides an opportunity to more fully elucidate the neurobehavioral phenotype associated with X monosomy and Turner's syndrome. 相似文献
103.
A E O'Hare MD FRCP G N Dutton FRCS FRCOphth D Green MB ChB MRCP Rosemary Coull 《Developmental medicine and child neurology》1998,40(6):417-420
The progress of cognitive visual dysfunction over an 8-year period of a child who sustained bilateral occipital-lobe infarctions at the age of 21/2 years is described. She survived with normal intelligence and went on to attend mainstream school. She manifested many features of cognitive visual impairment and, in particular, developed a form of pure alexia without agraphia. She achieved some letter-by-letter reading but no sight vocabulary development, including to her own name. She learned to write imaginatively employing phonetically true spelling but cannot read what she has written. Her progress and the difficulties encountered during the management of her condition are discussed in this first case report of the evolution of pure alexia without agraphia in childhood. The features of this syndrome in the developing child who has never developed the capacity to read are contrasted with that seen in affected adults. 相似文献
104.
Among 129 patients with spine pain and radiculopathy in both the cervical and lumbar region, there were significant differences between the upper and lower extremity DSER groups, noting the higher number of normal studies by our criteria in the upper extremities as compared to the lower extremities. This difference may be due to the intertwining of the "nerve circuitry" of the input pathways. It appears that the dermatomal somatosensory evoked response is a study of low sensitivity and of high specificity. 相似文献
105.
Phillip A. Reece Heather S. Hill R. Malcolm Green Raymond G. Morris Barry M. Dale Dusan Kotasek Robert E. Sage 《Cancer chemotherapy and pharmacology》1988,22(4):348-352
Summary The renal clearance of melphalan and the fraction unbound in plasma were determined after intravenous infusion of 5 mg/m2 over 5 min in nine patients with cancer to obtain information regarding the mechanism of renal handling of melphalan. Four of the patients underwent bone marrow transplantation and also received an IV dose of 220 mg/m2. Total melphalan clearance after the 5 mg/m2 dose ranged from 66.0 to 272 ml/min per m2; the percentage of the dose excreted unchanged in urine, from 2.5% to 92.8%; renal clearance, from 4.1 to 188 ml/min per m2; the fraction unbound in plasma, from 0.0598 to 0.460; and t1/2, from 39.4 to 84.3 min. Unbound melphalan clearance and renal clearance calculated from the unbound fraction in plasma for each patient ranged from 441 to 3356 ml/min per m2 and 15 to 961 ml/min per m2 respectively and were not related to serum albumin, serum creatinine or creatinine clearance. The percentage of the dose exctreted and melphalan renal clearance were not related to urine flow. There was evidence of active secretion of melphalan in the kidney an possible reabsorption. There were no significant paired differences in melphalan disposition between the high- and low-dose studies. Highly variable renal clearance involving active secretion may contribute in part to large interpatient differences in the total plasma clearance of melphalan in patients with cancer.This study was supported by a grant from The Queen Elizabeth Hospital Research Foundation 相似文献
106.
S Green 《Biomedical and environmental sciences : BES》1988,1(4):424-430
The Center for Food Safety and Applied Nutrition of the Food and Drug Administration has published guidelines for the safety assessment of direct food and color additives. These guidelines are to be updated beginning in 1988. The safety of a food and color additive must be established prior to marketing by an evaluation of probable exposure of consumers and appropriate toxicological information. "Safe" and "safety" are defined as a reasonable certainty that a substance is not harmful under the intended conditions of use. A number of tests are used in determining the safety of food additives. Some of these are: subchronic toxicity studies, chronic toxicity studies, carcinogenicity, reproduction, teratogenicity, and occasionally short-term tests for carcinogenicity. The Center also has a research program in toxicology which in part focuses on diet/toxicity interaction and risk assessment. Examples of such activities are investigation of the teratogenicity of textured vegetable protein and of the potential of zinc to prevent or ameliorate such effects, the development of whole rat embryo cultures as a model to investigate the mechanisms by which teratogens may act, and a program in pharmacokinetics and molecular toxicology to aid in studying assumptions underlying risk assessment. 相似文献
107.
Udaya DeSilva Laura Elnitski Jacquelyn R Idol Johannah L Doyle Weiniu Gan James W Thomas Scott Schwartz Nicole L Dietrich Stephen M Beckstrom-Sternberg Jennifer C McDowell Robert W Blakesley Gerard G Bouffard Pamela J Thomas Jeffrey W Touchman Webb Miller Eric D Green 《Genome research》2002,12(1):3-15
Williams syndrome is a complex developmental disorder that results from the heterozygous deletion of a approximately 1.6-Mb segment of human chromosome 7q11.23. These deletions are mediated by large (approximately 300 kb) duplicated blocks of DNA of near-identical sequence. Previously, we showed that the orthologous region of the mouse genome is devoid of such duplicated segments. Here, we extend our studies to include the generation of approximately 3.3 Mb of genomic sequence from the mouse Williams syndrome region, of which just over 1.4 Mb is finished to high accuracy. Comparative analyses of the mouse and human sequences within and immediately flanking the interval commonly deleted in Williams syndrome have facilitated the identification of nine previously unreported genes, provided detailed sequence-based information regarding 30 genes residing in the region, and revealed a number of potentially interesting conserved noncoding sequences. Finally, to facilitate comparative sequence analysis, we implemented several enhancements to the program, including the addition of links from annotated features within a generated percent-identity plot to specific records in public databases. Taken together, the results reported here provide an important comparative sequence resource that should catalyze additional studies of Williams syndrome, including those that aim to characterize genes within the commonly deleted interval and to develop mouse models of the disorder. 相似文献
108.
Pediatric solid-organ transplant recipients carry chronic loads of Epstein-Barr virus exclusively in the immunoglobulin D-negative B-cell compartment 下载免费PDF全文
Rose C Green M Webber S Ellis D Reyes J Rowe D 《Journal of clinical microbiology》2001,39(4):1407-1415
Solid-organ transplant recipients are at risk for development of lymphoproliferative diseases. The purpose of this study was to examine the distribution of Epstein-Barr virus (EBV) load in the peripheral blood of pediatric transplant recipients who had become chronic viral load carriers (>8 copies/10(5) lymphocytes for >2 months). A total of 19 patients with viral loads ranging from 20 to 5,000 viral genome copies/10(5) lymphocytes were studied. Ten patients had no previous diagnosis of posttransplant lymphoproliferative disease (PT-LPD), while nine had recovered from a diagnosed case of PT-LPD. No portion of the peripheral blood viral load was detected in the cell-free plasma fraction. Viral DNA was found in a population of cells characterized as CD19(hi) and immunoglobulin D negative, a phenotype that is consistent with the virus being carried exclusively in the memory B-cell compartment of the peripheral blood. There was no difference in the compartmentalization based upon either the level of the viral load or the past diagnosis of an episode of PT-LPD. These results have implications for the design of tests to detect EBV infection and for the interpretation and use of positive EBV PCR assays in the management of transplant recipients. 相似文献
109.
Treaba D Assad L Govil H Sariya D Reddy VB Kluskens L Green L Selvaggi SM Gattuso P 《Diagnostic cytopathology》2002,26(6):380-383
At the present time fine-needle aspiration (FNA) is considered a routine diagnostic procedure in evaluating neoplastic vs. nonneoplastic lesions in many organs, with high sensitivity and specificity. The purpose of this study was to assess the utility of FNA in areas of diagnostic difficulty and its limitations in evaluating bone lesions in patients with a previous history of malignancy. From 1989 to 2000, 249 CT-guided FNAs of bone lesion were performed at our institutions; 187/249 (75.1%) patients had a previous history of malignancy. Aspirated material was air-dried for Diff-Quik stain or fixed in ethanol for Papanicolaou staining. Subsequent surgical tissue was available in 69/187 (36.9%) of the cases. There were 114 males and 73 females, ages 14-86 yr (mean, 64 yr). The primary tumor site was lung 49, genitourinary 46, breast 31, gastrointestinal 28, hematopoietic 26, soft tissue/skin 5, and thyroid 2. There were 125 FNAs of the vertebral spine, 19 from the pelvis, 11 from the ribs, 9 from the sternum, 5 from the femur, and 18 from miscellaneous bone sites. Out of 187, 166 (88.7%) were malignant aspirates confirming the patients' primary malignancies. The most common malignancy encountered was adenocarcinoma, 126/187 (67.4%). Surgical tissue was available for review in 69 patients and the results were in agreement with the FNAs diagnosis in all cases. Nine out of 187 (4.8%) cases were diagnosed as marrow elements on cytological material. These patients have been followed for 1-9 yr and have failed to reveal signs or symptoms of clinical recurrence. Three out of 187 (1.6%) cases showed osteomyelitis. Nine out of 187 (4.8%) were unsatisfactory specimens, with biopsy follow-up available in four cases, showing three metastatic tumors and one case of osteomyelitis. FNA of metastatic bone lesions is a major step in pretreatment diagnosis. On satisfactory specimens, the cytological diagnosis viewed in the clinical-radiological context proves to be similar to surgical diagnosis. FNA is an excellent technique with a high accuracy rate in assessing metastatic bone lesions. 相似文献
110.
To test the hypothesis that complement-mediated cell lysis and cell-mediated cytotoxicity operate by analogous mechanisms, cell membranes from two antibody-dependent cytotoxicity systems were examined by electron microscopy after negative staining. Ring-shaped membrane lesions generally similar to, but larger than, those previously described for complement lysis were observed. These findings are in agreement with recent measurements of larger functional pores for ADCC than complement. 相似文献