全文获取类型
收费全文 | 2903125篇 |
免费 | 238197篇 |
国内免费 | 5680篇 |
专业分类
耳鼻咽喉 | 43066篇 |
儿科学 | 88560篇 |
妇产科学 | 78631篇 |
基础医学 | 411542篇 |
口腔科学 | 84344篇 |
临床医学 | 263008篇 |
内科学 | 563771篇 |
皮肤病学 | 59183篇 |
神经病学 | 243895篇 |
特种医学 | 116866篇 |
外国民族医学 | 1042篇 |
外科学 | 441905篇 |
综合类 | 72615篇 |
现状与发展 | 6篇 |
一般理论 | 1178篇 |
预防医学 | 234213篇 |
眼科学 | 69835篇 |
药学 | 217225篇 |
4篇 | |
中国医学 | 5521篇 |
肿瘤学 | 150592篇 |
出版年
2018年 | 29045篇 |
2016年 | 25049篇 |
2015年 | 28656篇 |
2014年 | 41082篇 |
2013年 | 62354篇 |
2012年 | 84090篇 |
2011年 | 88420篇 |
2010年 | 52054篇 |
2009年 | 49690篇 |
2008年 | 83478篇 |
2007年 | 89387篇 |
2006年 | 89853篇 |
2005年 | 87617篇 |
2004年 | 84726篇 |
2003年 | 81778篇 |
2002年 | 80447篇 |
2001年 | 130084篇 |
2000年 | 134566篇 |
1999年 | 113947篇 |
1998年 | 33517篇 |
1997年 | 30587篇 |
1996年 | 30148篇 |
1995年 | 29145篇 |
1994年 | 27457篇 |
1993年 | 25581篇 |
1992年 | 93022篇 |
1991年 | 89779篇 |
1990年 | 86903篇 |
1989年 | 83720篇 |
1988年 | 78020篇 |
1987年 | 77031篇 |
1986年 | 72868篇 |
1985年 | 69946篇 |
1984年 | 53443篇 |
1983年 | 45715篇 |
1982年 | 28239篇 |
1981年 | 25245篇 |
1980年 | 23767篇 |
1979年 | 51275篇 |
1978年 | 36323篇 |
1977年 | 30603篇 |
1976年 | 28600篇 |
1975年 | 30334篇 |
1974年 | 37520篇 |
1973年 | 35869篇 |
1972年 | 33637篇 |
1971年 | 31078篇 |
1970年 | 29402篇 |
1969年 | 27645篇 |
1968年 | 25148篇 |
排序方式: 共有10000条查询结果,搜索用时 19 毫秒
991.
Maria A. Giovino Robert J. Hawley Matt W. Dickerson Roseann Glaser Deborah H. Meshulam Robert Ardtsini Margaret D. Rosa Rod L. Monroy 《Xenotransplantation》1997,4(2):112-119
Abstract: Establishment of mixed bone marrow chimerism in pig-to-primate transplantation, as a means of inducing specific immune tolerance, will require that both immune and nonimmune barriers be overcome. As a preliminary step in evaluating nonimmune barriers in this system, we have developed an in vitro model of engraftment in which long-term culture of porcine bone marrow-derived hematopoietic cells is supported on preformed primate bone marrow stromal layers. In the absence of cytokine supplementation, primate stromal cells were unable to support long-term porcine hematopoiesis in these cultures. Supplementation with porcine Steel Factor was required for long-term maintenance of hematopoietic progenitor cell content and total hematopoietic activity. Addition of porcine IL-3, in combination with porcine Steel Factor, increased long-term progenitor cell content and hematopoietic activity on primate stroma to levels comparable to that obtained in cultures on porcine stroma. The combination of porcine GM-CSF and Steel Factor increased progenitor cell content and hematopoietic activity early in the cultures, but had little effect in long-term cultures. The Steel Factor and IL-3 combination was species-specific in its action in these cultures, as the corresponding human cytokines were unable to effectively support long-term porcine hematopoiesis. Likewise, the combination of porcine cytokines had only minimal effects on long-term bone marrow culture of primate CD34+ cells I on primate stroma. 相似文献
992.
Laparoscopic cholecystectomy and time-course changes in renal function 总被引:13,自引:3,他引:10
Y. Miki K. Iwase W. Kamiike E. Taniguchi K. Sakaguchi J. Sumimura H. Matsuda I. Nagai 《Surgical endoscopy》1997,11(8):838-841
Background: Recently, the retraction method has been used to reduce intraabdominal pressure (IAP) during laparoscopic surgery. The purpose
of this study was to determine the serial changes in renal function during laparoscopic cholecystectomy (LC) using the retraction
method.
Methods: Urine output, effective renal plasma flow (ERPF), and glomerular filtration rate (GFR) were measured serially in seven patients
who underwent LC with 12 mmHg pneumoperitoneum (High-IAP group) and five who underwent LC using the retraction method with
4 mmHg pneumoperitoneum (Low-IAP group).
Results: Urine output, ERPF, and GFR were decreased during pneumoperitoneum in the High-IAP group, whereas no significant changes
in any of these parameters were observed in the Low-IAP group.
Conclusions: Our findings demonstrate that reduction of IAP to 4 mmHg using the retraction method prevents the transient renal dysfunction
caused by prolonged 12 mmHg pneumoperitoneum during LC, suggesting that the retraction method reduces the risk of perioperative
renal dysfunction during laparoscopic surgery.
Received: 26 March 1996/Accepted: 27 July 1996 相似文献
993.
F. M. RAAPHORST R. LANGLOIS VAN DEN BERGH J. L. M. WAAIJER J. M. VOSSEN & M. J. D. VAN TOL 《Scandinavian journal of immunology》1997,46(3):292-297
Fetal B lymphocytes in mice and humans use a limited number of the available VH gene segments. Mouse fetal B cells primarily utilize 3' VH elements, suggesting that the localization of these elements determines their rearrangement frequency. The previously reported non-random usage of human VH genes has been more difficult to explain. In this study the authors analysed the expression of the most proximal 3' human VH element (VH 6) using a monoclonal antibody (JE-6). VH 6 expression was assessed in various B cell differentiation stages from fetal liver, bone marrow and spleen at 12–20 weeks of gestation. The authors demonstrate that the level of VH 6 expression does not exceed a stochastic usage frequency. This suggests that the localization of VH 6 does not significantly promote its expression during human fetal life, and that other factors must affect the usage of VH genes during human fetal development. 相似文献
994.
The authors aimed at evaluating the impact of psychotraumas in psychiatric outpatients. One hundred forty psychiatric outpatients were consecutively included, without distinction of their current pathology. They filled in an inventory of potentially traumatic experiences, a psychological dissociative experiences scale, a somatoform dissociative experiences questionnaire, and underwent a structured interview for diagnosis of posttraumatic stress disorder (according to the DSM-IV). One hundred subjects related psychological trauma, and 76 patients suffered from posttraumatic stress disorder. Dissociative disorders are found significantly correlated with traumatic experience and to posttraumatic stress disorder. The traumatic impact is found more substantial as the number of events was elevated. This study confirms the elevated prevalence of the psychological traumas and psychotraumatic aftermaths in outpatients of a department of psychiatry, independently from the mental disorder. 相似文献
995.
996.
Koichi Masuda Robert L Sah Michael J Hejna Eugene J-M A Thonar 《Journal of orthopaedic research》2003,21(1):139-148
Most attempts to tissue-engineer cartilage have involved seeding of cultured cells into a biological or synthetic scaffold. We have developed a novel two-step culture approach that makes possible the in vitro formation of cartilaginous-like tissue by mature adult bovine chondrocytes without the aid of a synthetic matrix. The first step consists of culturing chondrocytes under conditions that maintain their rounded shape and their molecular phenotype as assessed by type II collagen and aggrecan production. This step was accomplished by culturing the isolated chondrocytes in alginate beads until the cells have reestablished a proteoglycan-rich cell-associated matrix (CM). The second step consists of culturing the cells with their CM, after recovery from the beads, on a tissue culture insert with a porous membrane. In this study, young adult bovine articular chondrocytes were cultured in alginate beads in the presence of 10% or 20% fetal bovine serum (FBS). After 7 days of culture, the alginate beads were dissolved by incubating the beads for 20 min in sodium citrate buffer, a calcium chelator. Following a brief centrifugation, the cells with their CM were recovered, resuspended in medium containing 10% or 20% FBS and seeded onto a tissue culture insert. After 1 week of culture on the insert, the individual cells with their CM progressively became incorporated into a mass of cartilaginous tissue. Culture with 20% FBS resulted in the best formation of tissues. These tissues, easily recovered from the insert, were then subjected to biochemical and histological analyses. The biochemical results showed that the chondrocytes remain phenotypically stable in the tissues. The de novo tissue has a relatively high ratio of PG/collagen. Histological examination of the tissue revealed it contained a cartilage-like matrix strongly stained with toluidine blue. This scaffold-free system appears ideal to study, in vitro, the development of transplantable cartilaginous tissue. 相似文献
997.
998.
A case-control study of squamous cell carcinoma of the upper aerodigestive tract conducted in Heidelberg and Giessen (FRG) provided information on occupational factors in 200 patients and 800 controls (adjusted to sex, age and area of living; 4:1 matched design). The number of subjects exposed to wood dusts, organic chemicals, coal products or to cement was significantly elevated in the tumour group. An increased risk for head and neck cancer was observed after exposition to wood dust (RR = 2,2), organic compounds (RR = 2,4), coal products (RR = 2,7) and especially to cement (RR = 4,4). The cancer risk due to cement exposition showed a positive correlation to the duration of exposition and remained significantly elevated after adjustment for alcohol and tobacco consumption. 相似文献
999.
1000.
Prior immunologic experience potentiates the subsequent antibody response when Salmonella strains are used as vaccine carriers. 总被引:6,自引:5,他引:1 下载免费PDF全文
Prior immunologic experience with homologous and heterologous serotype Salmonella strains potentiated the subsequent antibody response when the same strains were used as vaccine carriers of foreign antigens. This potentiation was positively correlated with the appearance of antibody directed against the lipopolysaccharide of the carrier strain. Both serum and mucosal antibody responses against the foreign antigen increased over time. Antibody responses in sera of animals primed with either the homologous or heterologous serotype strain were not statistically significantly different, while animals primed with the homologous serotype strain developed significantly better mucosal antibody responses against the foreign antigen. 相似文献