全文获取类型
收费全文 | 32431篇 |
免费 | 2234篇 |
国内免费 | 460篇 |
专业分类
耳鼻咽喉 | 641篇 |
儿科学 | 560篇 |
妇产科学 | 680篇 |
基础医学 | 4543篇 |
口腔科学 | 504篇 |
临床医学 | 2628篇 |
内科学 | 7293篇 |
皮肤病学 | 998篇 |
神经病学 | 2191篇 |
特种医学 | 1680篇 |
外科学 | 4339篇 |
综合类 | 805篇 |
一般理论 | 15篇 |
预防医学 | 1320篇 |
眼科学 | 926篇 |
药学 | 2762篇 |
1篇 | |
中国医学 | 339篇 |
肿瘤学 | 2900篇 |
出版年
2023年 | 211篇 |
2022年 | 579篇 |
2021年 | 1000篇 |
2020年 | 504篇 |
2019年 | 821篇 |
2018年 | 954篇 |
2017年 | 682篇 |
2016年 | 910篇 |
2015年 | 1261篇 |
2014年 | 1483篇 |
2013年 | 1698篇 |
2012年 | 2470篇 |
2011年 | 2548篇 |
2010年 | 1582篇 |
2009年 | 1348篇 |
2008年 | 1890篇 |
2007年 | 1801篇 |
2006年 | 1635篇 |
2005年 | 1547篇 |
2004年 | 1321篇 |
2003年 | 1261篇 |
2002年 | 1153篇 |
2001年 | 780篇 |
2000年 | 695篇 |
1999年 | 655篇 |
1998年 | 272篇 |
1997年 | 256篇 |
1996年 | 227篇 |
1995年 | 188篇 |
1994年 | 171篇 |
1993年 | 106篇 |
1992年 | 312篇 |
1991年 | 231篇 |
1990年 | 265篇 |
1989年 | 262篇 |
1988年 | 249篇 |
1987年 | 203篇 |
1986年 | 184篇 |
1985年 | 166篇 |
1984年 | 143篇 |
1983年 | 112篇 |
1982年 | 85篇 |
1981年 | 75篇 |
1980年 | 71篇 |
1979年 | 125篇 |
1978年 | 87篇 |
1977年 | 68篇 |
1975年 | 59篇 |
1974年 | 54篇 |
1972年 | 50篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Hematological indices were determined in a group of 427 elderly Chinese subjects over 60 years old; reference ranges were established after excluding subjects with hemoglobinopathies or diseases giving rise to anemia and those with values less or greater than 3 SD from the mean. The values were similar to those for elderly Caucasians. All the red cell indices were significantly higher in men than women, possibly reflecting the influence of androgens on bone marrow function. Previously reported age-related decline in hemoglobin, red cell count and hematocrit from studies of all age groups was not seen in men or women above age 60 years, but a fall in platelet count with age, which had not been previously reported, was observed. There were no age-related changes in any other indices. Reference ranges were lower for Hb, MCV, and MCH in men and women, compared to those derived from a study of Chinese of all age groups. The prevalence of anemia due to disease and hemoglobinpathies in this population was 6.4% in men and 6.3% in women. 相似文献
82.
Potential impact of hormonal male contraception: cross-cultural implications for development of novel preparations 总被引:5,自引:0,他引:5
Martin CW Anderson RA Cheng L Ho PC van der Spuy Z Smith KB Glasier AF Everington D Baird DT 《Human reproduction (Oxford, England)》2000,15(3):637-645
The prospect of a hormonal male contraceptive is no longer distant. Data on the potential impact of this improvement in contraceptive provision, however, is limited, particularly between different cultures. We have therefore carried out a multi-centre study to assess men's attitudes to proposed novel hormonal methods. Questionnaire-based structured interviews were administered to men in Edinburgh, Cape Town, Shanghai and Hong Kong. Approximately 450 men were interviewed in Edinburgh, Shanghai and Hong Kong, and a slightly larger group (n = 493) in Cape Town to give samples (n > 150) of black, coloured and white men. Knowledge of existing male and female methods of contraception was high in all centres and groups. The majority of men welcomed a new hormonal method of contraception, 44-83% stating that they would use a male contraceptive pill. Overall, a pill was more acceptable than an injectable form (most popularly given at 3-6 month intervals); long-acting implants were least so except in Shanghai. Familiarity with comparable female methods appeared to influence acceptability, for both oral and injectable methods. Hong Kong was the only centre where a male method (condom) was currently the most commonly used; men there appeared to rate the convenience of condoms highly while being least likely to think that they provided effective protection against pregnancy compared to other centres, and were least enthusiastic about novel male methods. The acceptability of potential male hormonal methods of contraception was high in some groups but showed wide variability, determining factors including cultural background and current contraceptive usage. These results suggest that the emerging emphasis that men should have greater involvement in family planning will be substantiated when appropriate contraceptive methods become available. 相似文献
83.
Hematopoietic progenitor cells and cellular microenvironment: behavioral and molecular changes upon interaction 总被引:2,自引:0,他引:2
Wagner W Saffrich R Wirkner U Eckstein V Blake J Ansorge A Schwager C Wein F Miesala K Ansorge W Ho AD 《Stem cells (Dayton, Ohio)》2005,23(8):1180-1191
Cell-cell contact between stem cells and cellular determinants of the microenvironment plays an essential role in controlling cell division. Using human hematopoietic progenitor cells (CD34+/CD38-) and a stroma cell line (AFT024) as a model, we have studied the initial behavioral and molecular sequel of this interaction. Time-lapse microscopy showed that CD34+/CD38- cells actively migrated toward and sought contact with stroma cells and 30% of them adhered firmly to AFT024 stroma through the uropod. CD44 and CD34 are colocalized at the site of contact. Gene expression profiles of CD34+/CD38- cells upon cultivation with or without stroma for 16, 20, 48, or 72 hours were analyzed using our human genome cDNA microarray. Chk1, egr1, and cxcl2 were among the first genes upregulated within 16 hours. Genes with the highest upregulation throughout the time course included tubulin genes, ezrin, c1qr1, fos, pcna, mcm6, ung, and dnmt1, genes that play an essential role in reorganization of the cytoskeleton system, stabilization of DNA, and methylation patterns. Our results demonstrate directed migration of CD34+/CD38- cells toward AFT024 and adhesion through the uropod and that upon interaction with supportive stroma, reorganization of the cytoskeleton system, regulation of cell division, and maintenance of genetic stability represent the most essential steps. 相似文献
84.
Ocular colobomata, cardiac defect, and other anomalies: a study of seven cases including two sibs. 下载免费PDF全文
An association of ocular colobomata and congenital heart disease was observed in seven patients. Two of these were maternal half sisters whose mother also had ocular colobomata. All the patients had normal karyotypes. There was a high incidence of other associated abnormalities involving the central nervous, skeletal, and urogenital systems. Discovery of an ocular coloboma should alert the clinician to search for other abnormalities. 相似文献
85.
86.
Calmodulin content was evaluated in 3 prolactin-secreting pituitary adenomas (prolactinoma) and 3 normal anterior pituitary glands. The calmodulin content in the normal anterior pituitary tissue was quite consistent, 3.32 +/- 0.016 micrograms/mg protein. In contrast, calmodulin content varied almost 4-fold in the prolactinoma tissue (10.97, 8.50 and 3.00 micrograms/mg protein). Preoperative serum prolactin levels varied inversely with the prolactinoma calmodulin content (125, 257 and 3526 ng/ml, respectively). This study reveals that prolactinoma calmodulin content differs from normal, although it is not uniformly elevated as in other transformed tissues and that elevation of prolactinoma calmodulin content does not positively correlate with serum prolactin levels. 相似文献
87.
Expression of the human T cell receptor V beta repertoire. 总被引:5,自引:0,他引:5
P J Doherty C M Roifman S H Pan U Cymerman S W Ho E Thompson S Kamel-Reid A Cohen 《Molecular immunology》1991,28(6):607-612
We have used a sensitive assay, based on amplification of cDNA by the polymerase chain reaction, to determine in a variety of human tissues the relative levels of expression of the genes coding for each of the twenty families of human TcR V beta. We have determined the diversity of the expressed TcR V beta repertoire early in the development of the immune system. We have shown that the full TcR V beta repertoire is expressed early into the second trimester; the expressed repertoire is as diverse at this point, in both fetal thymus and spleen, as it is in mature thymus and peripheral blood lymphocytes. In addition the relative expression in the fetal thymus of each V beta gene is conserved to a large extent in the fetal spleen. 相似文献
88.
In this study we investigate the expression pattern of mucin genes in the human testis and evaluate the relationship between the expression of mucin genes and impaired spermatogenesis in the human testis. Thirty human testis tissues were collected from patients undergoing diagnostic testicular biopsy to investigate the cause of infertility. One part of the tissue underwent histological observation, and the other part of the tissue was subjected to semiquantitative RT-PCR of mucin genes, that is, mucin1, 2, 3, 4, and 9. The relative amount of mucin mRNAs was calculated by densitometry using glyceraldehydes-3-phosphate dehydrogenase (GAPDH) as an internal control. The samples were histologically diagnosed as either obstructive azoospermia with normal spermatogenesis (n = 13) or non-obstructive azoospermia with impaired spermatogenesis (n = 17). In the human testis with normal spermatogenesis, mRNA expression of mucin1, 9, 13 and GAPDH were found, but RT-PCR products of mucin 2, 3 and 4 were not detected. In the testis with impaired spermatogenesis, however, RT-PCR product of mucin1 was not found. There was no difference in the other mucin mRNA expression patterns between the testis with either normal or impaired spermatogenesis. To our knowledge, this study is the first that has detected the mRNA of mucin9 and 13 in human testis. This study also shows that mucin1 expression might be closely related to spermatogenesis. Our findings should be substantiated by more direct evidence, such as mucin protein expression and localization. 相似文献
89.
Jeune syndrome (JS) and short-rib polydactyly syndrome type III (SRP type III) are autosomal recessive disorders characterized by short ribs and polydactyly. They are distinguished from each other by the more severe radiological and histological bone findings as well as the occurrence of facial anomalies, ambiguous genitalia, and occasionally, cloacal abnormalities in SRP type III. We present a family in which two children have mild JS and one has SRP type III as evidence that JS and SRP type III are variants of the same disorder. The intrafamilial variability may reflect the effects of modifying loci on gene expression. 相似文献
90.
4-1BB(CD137) is a member of the tumour necrosis factor receptor superfamily and is expressed on activated T cells, monocytes and natural killer (NK) cells. The interaction of 4-1BB and 4-1BB ligand provides a costimulatory signal leading to T-cell activation. The expression of 4-1BB has been known to be activation dependent. Interestingly, we found that expression of 4-1BB increased in human peripheral blood mononuclear cells after exposure to mitomycin C. Thus, we tested whether the treatment with other DNA-damaging agents, such as doxorubicin, bleomycin, and gamma-irradiation, could induce 4-1BB expression. The data indicated that 4-1BB expression increased dose-dependently by these agents reaching maximum at 2-3 days after the exposure. We found that the major 4-1BB-expressing population was CD3+ T cells, although a moderate number of CD14+ cells and a few NKB1+ cells also expressed 4-1BB. The levels of 4-1BB expression induced by anticancer drugs, were relatively lower than that induced by CD3 ligation. Interestingly, at subcytotoxic concentrations, doxorubicin and bleomycin considerably enhanced 4-1BB expression induced by CD3 ligation in CEM cells. The ligation of the damage-induced 4-1BB by monoclonal antibody enhanced the viability and proliferating capacity of the cells. In conclusion, the expression of 4-1BB might be one of the cellular responses of the immune cells against various genotoxic stresses. 相似文献