全文获取类型
收费全文 | 210300篇 |
免费 | 15221篇 |
国内免费 | 749篇 |
专业分类
耳鼻咽喉 | 2284篇 |
儿科学 | 5485篇 |
妇产科学 | 4305篇 |
基础医学 | 27105篇 |
口腔科学 | 4512篇 |
临床医学 | 19999篇 |
内科学 | 44900篇 |
皮肤病学 | 2754篇 |
神经病学 | 20305篇 |
特种医学 | 6951篇 |
外国民族医学 | 13篇 |
外科学 | 32916篇 |
综合类 | 3412篇 |
现状与发展 | 2篇 |
一般理论 | 291篇 |
预防医学 | 19066篇 |
眼科学 | 4373篇 |
药学 | 14396篇 |
1篇 | |
中国医学 | 374篇 |
肿瘤学 | 12826篇 |
出版年
2023年 | 843篇 |
2022年 | 1405篇 |
2021年 | 3441篇 |
2020年 | 2107篇 |
2019年 | 3392篇 |
2018年 | 3969篇 |
2017年 | 3214篇 |
2016年 | 3413篇 |
2015年 | 4067篇 |
2014年 | 6097篇 |
2013年 | 8824篇 |
2012年 | 13124篇 |
2011年 | 14319篇 |
2010年 | 8097篇 |
2009年 | 7305篇 |
2008年 | 13589篇 |
2007年 | 14428篇 |
2006年 | 13920篇 |
2005年 | 14392篇 |
2004年 | 13810篇 |
2003年 | 12901篇 |
2002年 | 12436篇 |
2001年 | 1876篇 |
2000年 | 1458篇 |
1999年 | 2048篇 |
1998年 | 2829篇 |
1997年 | 2438篇 |
1996年 | 2205篇 |
1995年 | 1953篇 |
1994年 | 1756篇 |
1993年 | 1655篇 |
1992年 | 1208篇 |
1991年 | 1151篇 |
1990年 | 1056篇 |
1989年 | 953篇 |
1988年 | 1012篇 |
1987年 | 1019篇 |
1986年 | 998篇 |
1985年 | 1082篇 |
1984年 | 1478篇 |
1983年 | 1462篇 |
1982年 | 1814篇 |
1981年 | 1639篇 |
1980年 | 1555篇 |
1979年 | 812篇 |
1978年 | 958篇 |
1977年 | 932篇 |
1976年 | 831篇 |
1975年 | 682篇 |
1974年 | 666篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
931.
932.
James K. Yeh Meng-Meng Chen John F. Aloia 《Anatomical record (Hoboken, N.J. : 2007)》1995,241(4):505-512
Background: Hypophysectomy (HX) results in a cessation of bone growth and a decrease in bone metabolism. The purpose of this study is to examine the effect of HX on the static and dynamic histomorphometry of cancellous bone in the secondary spongiosa of the proximal tibial metaphysis in rats. Methods: Female rats, at 2 or 3 months of age, were HX and sacrificed at 0, 5 days, 2 and 5 weeks after the surgery. Age-matched intact rats served as controls. Cancellous bone histomorphometry was performed on doublefluorescent labeled, 30-um-thick sections of the proximal tibia. Tartrateresistant acid phosphatase histomorphometry was performed at 5 days on HX and control rats to evaluate the resorption in the metaphyseal bone. Results: Although the intact rats gained in body weight, tibial length, tibial weight, and density after 5 weeks, these changes did not occur following HX. As compared to the basal group, HX resulted in a decrease in the density and dry weight of the metaphysis. The histomorphometric data showed that the cancellous bone volume and trabecular number of the secondary spongiosa were decreased and the separation was increased in the HX rats. The dynamic results showed that HX significantly decreased longitudinal growth rate and tissue-based bone formation and resorption. However, the bone surface-based eroded surface, labeled surface, the mineral apposition rate, and the bone formation rate did not differ between the intact and the HX rats at either the 2 or 5 weeks study. Five days after HX, the bone surface and tissue-based osteoclast surfaces were significantly lower in the HX than in the intact rats. Conclusions: Pituitary hormone deficiency results in cancellous bone loss. The bone loss is due primarily to the suppression of longitudinal growth-dependent bone gain and the inhibition of tissue-based bone turnover with a lower bone formation relative to bone resorption. The surfacebased bone turnover is not affected. © 1995 Wiley-Liss, Inc. 相似文献
933.
Hybrid cells derived from rat L6 myoblasts and mouse primary fibroblasts (M x F hybrids), as well as those derived from rat L6 myoblasts and mouse primary myoblasts (M x M hybrids), were examined for their ability to engage in myogenesis as judged by muscle fiber formation plus the expression of skeletal muscle myosin and creatine kinase (CK). Of 172 primary hybrid colonies scored, 59% were myogenic in the M x F fusion and 97% exhibited muscle fiber formation in the M x M fusion. Individual hybrid clones from each cross were isolated, expanded and analyzed for myogenic capabilities as well. All three M x M and all ten M x F isolated clones exhibited preferential elimination of mouse chromosomes. Nonetheless, all were capable of fusing spontaneously and of elaborating skeletal muscle myosin and CK. The three M x M hybrids expressed only MM-CK whereas nine out of ten M x F hybrids produced all three CK isoenzymes (MM, MB, BB). These results suggest that M x M hybrids express CK patterns reminiscent of the rat L6 parental cells while M x F hybrids apparently mimic mouse muscle fiber CK patterns. Various models are discussed which address these phenomena. 相似文献
934.
Consultation length, patient-estimated consultation length, and satisfaction with the consultation. 下载免费PDF全文
John Cape 《The British journal of general practice》2002,52(485):1004-1006
Lack of time is a frequently expressed patient concern, but actual measured consultation length is often not associated with patient satisfaction. Correlational analysis of patients from nine GP practices was used to test the hypothesis that patients' perceptions of consultation length are influenced not just by actual consultation length, but by other aspects of their experience of consultations. The consultations of 160 patients were timed, and patients in subsequent interviews gave estimates of consultation duration and completed a satisfaction questionnaire. Consultations where patients were more satisfied appeared to patients to have lasted longer (partial correlation r = 0.26), but were not actually longer. Patient concerns about time may be as much about quality time as about actual time. 相似文献
935.
The Cdc7p protein kinase plays an essential, but undefined, role promoting S phase in the budding yeast, Saccharomyces cerevisiae. Previous experiments have shown that the essential function of Cdc7 is executed near the G1–S boundary; after Start but before the elongation phase of DNA replication. Origins of DNA replication fire throughout S phase in budding yeast. Therefore, the G1–S transition is a cell-cycle event that precedes, and is distinct from, the activation of individual origins. Consequently, we have asked whether Cdc7 is only required for S-phase entry or if it plays a role during S phase in origin firing. In this article, we show that partial loss of Cdc7 function results in slow progression through S phase rather than slow entry into S phase and that Cdc7 is still required for the timely completion of S phase after a block to elongation with hydroxyurea. This is because Cdc7 is still required for the activation of late-firing origins after the hydroxyurea block. These experiments show that, rather than acting as a global regulator of the G1–S transition, Cdc7 appears to play a more direct role in the firing of replication origins during S phase. 相似文献
936.
Between 1996 and 1998, two clades (B and C; genotype I) of dengue virus type 1 (DENV-1) appeared in Myanmar (Burma) that were new to that location. Between 1998 and 2000, a third clade (A; genotype III) of DENV-1, which had been circulating at that locality for at least 25 years, became extinct. These changes preceded the largest outbreak of dengue recorded in Myanmar, in 2001, in which more than 95% of viruses recovered from patients were DENV-1, but where the incidence of severe disease was much less than in previous years. Phylogenetic analyses of viral genomes indicated that the two new clades of DENV-1 did not arise from the, now extinct, clade A viruses nor was the extinction of this clade due to differences in the fitness of the viral populations. Since the extinction occurred during an inter-epidemic period, we suggest that it was due to a stochastic event attributable to the low rate of virus transmission in this interval. 相似文献
937.
Comorbid psychiatric disorders in depressed outpatients: demographic and clinical features 总被引:2,自引:0,他引:2
Rush AJ Zimmerman M Wisniewski SR Fava M Hollon SD Warden D Biggs MM Shores-Wilson K Shelton RC Luther JF Thomas B Trivedi MH 《Journal of affective disorders》2005,87(1):43-55
BACKGROUND: This study evaluated the clinical and sociodemographic features associated with various degrees of concurrent comorbidity in adult outpatients with nonpsychotic major depressive disorder (MDD). METHODS: Outpatients enrolled in the STAR*D trial completed the Psychiatric Diagnostic Screening Questionnaire (PDSQ). An a priori 90% specificity threshold was set for PDSQ responses to ascertain the presence of 11 different concurrent DSM-IV Axis I disorders. RESULTS: Of 1376 outpatients, 38.2% had no concurrent comorbidities, while 25.6% suffered one, 16.1% suffered two, and 20.2% suffered three or more comorbid conditions. Altogether, 29.3% met threshold for social anxiety disorder, 20.8% for generalized anxiety disorder, 18.8% for posttraumatic stress disorder, 12.4% for bulimia, 11.9% for alcohol abuse/dependence, 13.4% for obsessive-compulsive disorder, 11.1% for panic disorder, 9.4% for agoraphobia, 7.3% for drug abuse/dependence, 3.7% for hypochondriasis, and 2.2% for somatoform disorder. Those with more concurrent Axis I conditions had earlier ages at first onset of MDD, longer histories of MDD, greater depressive symptom severity, more general medical comorbidity (even though they were younger than those with fewer comorbid conditions), poorer physical and mental function, health perceptions, and life satisfaction; and were more likely to be seen in primary care settings. LIMITATIONS: Participants had to meet entry criteria for STAR*D. Ascertainment of comorbid conditions was not based on a structured interview. CONCLUSIONS: Concurrent Axis I conditions (most often anxiety disorders) are very common with MDD. Greater numbers of concurrent comorbid conditions were associated with increased severity, morbidity, and chronicity of their MDD. 相似文献
938.
939.
Adherence of Streptococcus pneumoniae to Human Bronchial Epithelial Cells (BEAS-2B) 总被引:1,自引:0,他引:1 下载免费PDF全文
John E. Adamou Theresa M. Wizemann Philip Barren Solomon Langermann 《Infection and immunity》1998,66(2):820-822
Pneumococcal adherence to alveolar epithelial cells and nasopharyngeal epithelial cells has been well characterized. However, the interaction of Streptococcus pneumoniae with bronchial epithelial cells has not been studied. We have now shown that pneumococci bind specifically to a human bronchial epithelial cell line (BEAS-2B cells). Pneumococci adhered to BEAS-2B cells in a time- and dose-dependent manner. These results suggest that the bronchial epithelium may serve as an additional site of attachment for pneumococci and demonstrate the utility of the BEAS-2B cell line for studying mechanisms of pneumococcal infection. 相似文献
940.
Differentiation of Strains of Infectious Bovine Rhinotracheitis Virus by Neutralization Kinetics with Late 19S Rabbit Antibodies 总被引:2,自引:0,他引:2 下载免费PDF全文
Two vaccine, two respiratory (infectious bovine rhinotracheitis [IBR]), and two genital (infectious pustular vulvovaginitis [IPV]) strains of infectious bovine rhinotracheitis virus were compared by neutralization kinetics using late 19S antibody (AB). The two vaccine strains were indistinguishable from one another, but were neutralized far more rapidly than the other four strains when either anti-IBR or anti-IPV 19S AB was used. The two IPV strains were indistinguishable from one another, but were neutralized significantly more rapidly than the two IBR strains when anti-IBR 19S AB was used. The 2 IBR strains were neutralized at a similar rate with the latter globulin preparation. Almost identical results were obtained with anti-IPV 19S AB, except that one IPV strain was neutralized at a rate similar to the IBR strains. However, when early and late rabbit 7S AB were used, IBR strains could not be distinguished from IPV strains by neutralization kinetics. Preliminary experiments indicated that both early and late 19S rabbit antibodies neutralized the homologous strain more rapidly than the heterologous strain, but the difference was more noticeable with late 19S AB. It was also determined that neutralization of IBR-IPV virus by specific early and late 19S rabbit AB and early 7S rabbit AB was markedly enhanced by guinea pig complement. Neutralization of this virus by late 7S AB, however, was only slightly enhanced by complement. These results suggest that vaccine strains of IBR-IPV virus may be distinguished by neutralization kinetics with late 19S rabbit AB, and that genital and respiratory strains may possibly also be distinguishable with some 19S AB preparations. 相似文献