全文获取类型
收费全文 | 7404篇 |
免费 | 393篇 |
国内免费 | 38篇 |
专业分类
耳鼻咽喉 | 56篇 |
儿科学 | 148篇 |
妇产科学 | 92篇 |
基础医学 | 790篇 |
口腔科学 | 156篇 |
临床医学 | 565篇 |
内科学 | 2116篇 |
皮肤病学 | 134篇 |
神经病学 | 511篇 |
特种医学 | 254篇 |
外科学 | 1521篇 |
综合类 | 15篇 |
预防医学 | 173篇 |
眼科学 | 93篇 |
药学 | 504篇 |
中国医学 | 24篇 |
肿瘤学 | 683篇 |
出版年
2023年 | 41篇 |
2022年 | 45篇 |
2021年 | 126篇 |
2020年 | 84篇 |
2019年 | 104篇 |
2018年 | 142篇 |
2017年 | 100篇 |
2016年 | 137篇 |
2015年 | 154篇 |
2014年 | 181篇 |
2013年 | 224篇 |
2012年 | 310篇 |
2011年 | 372篇 |
2010年 | 212篇 |
2009年 | 180篇 |
2008年 | 342篇 |
2007年 | 365篇 |
2006年 | 338篇 |
2005年 | 399篇 |
2004年 | 361篇 |
2003年 | 325篇 |
2002年 | 338篇 |
2001年 | 277篇 |
2000年 | 311篇 |
1999年 | 231篇 |
1998年 | 89篇 |
1997年 | 71篇 |
1996年 | 58篇 |
1995年 | 51篇 |
1994年 | 63篇 |
1993年 | 60篇 |
1992年 | 166篇 |
1991年 | 163篇 |
1990年 | 143篇 |
1989年 | 160篇 |
1988年 | 115篇 |
1987年 | 131篇 |
1986年 | 139篇 |
1985年 | 120篇 |
1984年 | 68篇 |
1983年 | 64篇 |
1982年 | 35篇 |
1979年 | 34篇 |
1978年 | 31篇 |
1975年 | 29篇 |
1971年 | 34篇 |
1970年 | 30篇 |
1969年 | 30篇 |
1968年 | 33篇 |
1966年 | 29篇 |
排序方式: 共有7835条查询结果,搜索用时 15 毫秒
81.
The development and distribution of lymphocyte subsets in bovine gut-associated lymphoid tissues (ileal and jejunal Peyer's patches (PP)) were examined. Before birth, the composition of lymphocyte subsets in both PP follicles did not differ except for the dimensions of the interfollicular area and the dome region. Many IgM+ cells were observed in these follicles, but very few CD3+, IgG+, and IgA+ cells could be found. At neonatal period, the IgG+ cells, which did not produce IgG mRNA, were dominant within both PP follicles. From 1 month after birth, many CD3+ cells, IgG mRNA expression, and IgA mRNA expression were detected within the jejunal PP follicles, but very few were in the ileal PP follicles. These data suggest that the characteristics of the jejunal PP follicles metamorphose into secondary lymphoid tissue such as germinal centers at around 1 month after birth, whereas the characteristics of ileal PP follicles were distinct from those of germinal centers. 相似文献
82.
Kenichi Ohashi Yo Kato Jun Kanno Tsutomu Kasuga 《Virchows Archiv : an international journal of pathology》1990,417(2):137-143
Summary Normal oesophagus specimens taken from 65 autopsy cases and surgical specimens from 127 oesophageal carcinoma cases were examined
histopathologically to determine melanocyte incidence and distribution. Melanocytes were found in the epithelio-stromal junction
in 7.7% of normal oesophagus specimens examined at autopsy, and in 29.9% of surgical cases with oesophageal carcinoma. Positive
specimens in the latter groups, especially from pre-operatively irradiated individuals, showed a more remarkable increase
of melanocytes than was evident in any of the normal oesophageal samples. There were no significant differences in incidence
between males and females, or between age groups. In cases where the cancer invaded into deeper stroma, the melanocytes were
mainly observed in the normal epithelium around the carcinomas. Epithelial and stromal elements of the melanotic mucosa commonly
showed hyperplastic changes such as acanthosis or basal cell hyperplasia, and chronic oesophagitis. Melanocytes were observed
most commonly in the lower part of the oesophagus, the site where malignant melanoma of the oesophagus, most often originates.
These results strongly suggest that the melanocyte increase observed in areas of hyperplastic epithelium and chronic oesophagitis
may play an important role as a precursor lesion for malignant melanoma in the oesophagus. 相似文献
83.
84.
85.
M Fukuoka K Yasuda H Fujiwara H Kanzaki T Mori 《Human reproduction (Oxford, England)》1992,7(10):1361-1364
We have reported that the cytokines, interleukin-1 (IL-1), tumour necrosis factor alpha (TNF alpha), and interferon (IFN) alpha, beta, and gamma modulate the steroidogenic function of human luteinized granulosa cells in culture. In the present study we examined the interactions between these cytokines in modulating progesterone and oestradiol production by these cells. Neither IL-1 nor TNF alpha had significant effects on human chorionic gonadotrophin (HCG)-stimulated progesterone production, whereas IFN gamma (1-10 ng/ml) significantly reduced HCG-stimulated progesterone production by 26-37%. Concomitant treatment with IL-1 (1 ng/ml) did not further enhance the inhibitory effect of IFN gamma on HCG-stimulated progesterone production. In contrast, the combination of TNF alpha (1 ng/ml) and IFN gamma (10 ng/ml) acted synergistically to markedly inhibit HCG-stimulated progesterone production by 81%. In addition, IL-1 and TNF alpha, neither of which was effective alone, acted synergistically to reduce significantly HCG-stimulated progesterone production by 30%. The combination of TNF alpha and IFN gamma also markedly inhibited follicle stimulating hormone (FSH)-stimulated oestradiol production by 97%, a significantly greater inhibition than that obtained with either cytokine alone. These results suggest that the cytokines may interact to modulate the steroidogenic function of luteal cells in the developing corpus luteum. 相似文献
86.
Takakuwa K Hataya I Arakawa M Kikuchi A Higashino M Yasuda M Kurabayashi T Tanaka K 《American journal of reproductive immunology (New York, N.Y. : 1989)》1999,42(4):233-239
PROBLEM: To clarify whether HLA-DP antigens are associated with patient population of unexplained recurrent abortion. METHOD OF STUDY: The frequency of HLA-DPB1 alleles in patients with unexplained recurrent abortion, and the compatibility of HLA-DPB1 alleles between patient couples, were studied using a polymerase chain reaction (PCR)-restricted fragment length polymorphism (RFLP) method. Thirty patients who had a history of unexplained primary recurrent abortion, and their husbands, were typed for HLA-DPB1 genotype. Two hundred and ninety-nine base pair fragments from the second exon of HLA-DPB1 genes were selectively amplified using the PCR-primers. After amplification, the DNAs were digested with restriction endonucleases, and subjected to electrophoresis in a 12% polyacrilamide gel to determine HLA-DPB1 genotype. RESULTS: The frequency of HLA-DPB1*0402 and DPB1*04 alleles in the patient group (n = 30) was significantly increased, as compared to that in the normal fertile women (n = 30). The frequency of HLA-DPB1*04 allele in the patient group was significantly increased, as compared to that in the general population (n = 112). No significant compatibility of HLA-DPB1 alleles could be observed between patient couples and normal fertile couples. CONCLUSION: These findings suggest a possible new class II association with patient population of unexplained recurrent abortion. 相似文献
87.
When chicken erythrocytes (CRBC) were pretreated with non-haemolytic Sendai virions or isolated HANA spikes, they acquired a resistance to the haemolytic action of "second challenge" viruses. This resistance was dependent on the quantity of N-acetylneuraminic acid liberated from the surface of the CRBC by the initial virus, and not on the use of different viral sources. When exposed to Sendai virus, CRBC were more difficult to be lysed and easier liberated N-acetylneuraminic acid than human 0 erythrocytes. The restricted number of virions able to fuse CRBC was explained by such neuraminidase function of the HANA spike of the virion. 相似文献
88.
89.
90.
Khan MH Yasuda M Higashino F Haque S Kohgo T Nakamura M Shindoh M 《The American journal of pathology》2001,158(5):1785-1791
nm23-H1 is a candidate gene for the suppression of cancer metastasis. Several studies on human breast, hepatocellular, gastric, ovarian, and colon carcinomas and melanomas have shown that reduced nm23-H1 expression was closely related to metastatic progression with poor prognosis. However, the biochemical mechanism by which nm23-H1 suppresses the metastasis has yet to be elucidated. In this study, we analyzed the correlation between nm23 expression, cell motility, and the invasive abilities of six different oral squamous cell carcinoma cell lines (HSC2, HSC3, HSC4, KB, OSC19, and OSC20). Reduced mRNA/protein expression of the nm23-H1 was observed in three cell lines (HSC2, HSC3, and HSC4). These cell lines exhibited increased cell motility and an invasive character on organotypic raft culture. On the other hand, the cell lines (KB, OSC19, and OSC20) that showed a higher expression of nm23-H1 exhibited a threefold to fivefold reduced motility and also reflected fewer invasions compared to the former three cell lines. Because the HSC3 cells demonstrated the lowest nm23-H1 expression with the highest cell motility and invasive character, we established nm23-H1-transfected HSC3 cell lines to investigate whether exogenous nm23-H1 protein could inhibit cell migration and invasive activity. These transfectants showed a significant reduction in cell motility with exogenous nm23-H1 in a dose-dependent manner, and exhibited a noninvasive character. An immunofluorescence study demonstrated a distinct stress-fiber distribution at peripheral region of these transfectants. However, no significant difference of matrix metalloproteinase (MMP)-2 and MMP-9 expression was observed between mock transfectant and nm23-H1-transfected cells. These findings suggest that nm23-H1 inhibits the invasive activity of oral squamous cell carcinoma by suppression of cell motility without altering the MMP-2 and MMP-9 status. 相似文献