全文获取类型
收费全文 | 2815篇 |
免费 | 183篇 |
国内免费 | 27篇 |
专业分类
耳鼻咽喉 | 2篇 |
儿科学 | 173篇 |
妇产科学 | 43篇 |
基础医学 | 308篇 |
口腔科学 | 81篇 |
临床医学 | 227篇 |
内科学 | 694篇 |
皮肤病学 | 50篇 |
神经病学 | 90篇 |
特种医学 | 507篇 |
外科学 | 312篇 |
综合类 | 43篇 |
预防医学 | 196篇 |
眼科学 | 29篇 |
药学 | 106篇 |
中国医学 | 8篇 |
肿瘤学 | 156篇 |
出版年
2023年 | 9篇 |
2022年 | 30篇 |
2021年 | 35篇 |
2020年 | 36篇 |
2019年 | 49篇 |
2018年 | 68篇 |
2017年 | 45篇 |
2016年 | 51篇 |
2015年 | 63篇 |
2014年 | 62篇 |
2013年 | 101篇 |
2012年 | 77篇 |
2011年 | 85篇 |
2010年 | 112篇 |
2009年 | 91篇 |
2008年 | 90篇 |
2007年 | 98篇 |
2006年 | 109篇 |
2005年 | 83篇 |
2004年 | 73篇 |
2003年 | 63篇 |
2002年 | 72篇 |
2001年 | 58篇 |
2000年 | 59篇 |
1999年 | 66篇 |
1998年 | 139篇 |
1997年 | 123篇 |
1996年 | 132篇 |
1995年 | 93篇 |
1994年 | 75篇 |
1993年 | 86篇 |
1992年 | 31篇 |
1991年 | 33篇 |
1990年 | 31篇 |
1989年 | 70篇 |
1988年 | 52篇 |
1987年 | 54篇 |
1986年 | 67篇 |
1985年 | 52篇 |
1984年 | 29篇 |
1983年 | 39篇 |
1982年 | 37篇 |
1981年 | 24篇 |
1980年 | 36篇 |
1979年 | 15篇 |
1978年 | 19篇 |
1977年 | 21篇 |
1976年 | 23篇 |
1975年 | 27篇 |
1970年 | 6篇 |
排序方式: 共有3025条查询结果,搜索用时 15 毫秒
21.
We report an adult female with a rare giant choledochal cyst. The patient presented following a normal pregnancy with the classical triad of an abdominal mass associated with jaundice and right upper quadrant abdominal pain. The cyst was excised using an intramural technique and biliary reconstruction achieved with a Roux-en-Y hepaticojejunostomy. Our patient has remained well with no evidence of malignancy over a 12 year review period. The aetiology and current management of this condition are discussed. 相似文献
22.
23.
Krummenacher C Baribaud F Ponce de Leon M Baribaud I Whitbeck JC Xu R Cohen GH Eisenberg RJ 《Virology》2004,322(2):286-299
The herpesvirus entry mediator A (HVEM/HveA) and nectin-1 (HveC/CD111) are two major receptors for herpes simplex virus (HSV). Although structurally unrelated, both receptors can independently mediate entry of wild-type (wt) HSV-1 and HSV-2 by interacting with the viral envelope glycoprotein D (gD). Laboratory strains with defined mutations in gD (e.g. rid1) do not use HVEM but use nectin-2 (HveB/CD112) for entry. The relative usage of HVEM and nectin-1 during HSV infection in vivo is not known. In the absence of a defined in vivo model, we used in vitro approaches to address this question. First, we screened HSV clinical isolates from various origins for receptor tropism and found that all used both HVEM and nectin-1. Second, we determined the numbers of surface receptors on various susceptible and resistant cell lines as well as on primary fibroblasts derived from an individual with cleft lip/palate ectodermal dysplasia (CLPED1). Although CLPED1 cells can only express a defective form of nectin-1, they allowed entry of wild type and mutant HSV strains by usage of either HVEM or nectin-2. Finally, we compared the ability of HVEM and nectin-1 to mediate entry when expressed at varying cell surface densities. Both receptors showed a direct relationship between the number of receptors and HSV susceptibility. Direct comparison of receptors suggests that nectin-1 is more efficient at promoting entry than HVEM. Overall, our data suggest that both receptors play a role during HSV infection in vivo and that both are highly efficient even at low levels of expression. 相似文献
24.
Na+ dependence of in vitro pancreatic amylase release 总被引:1,自引:0,他引:1
25.
Determination of optimal cryoprotectants and procedures for their addition and removal from human spermatozoa 总被引:9,自引:7,他引:9
The objective was to test the hypothesis that the optimal cryoprotective
agent for cryopreservation of human spermatozoa would be a solute for which
cells have the highest plasma membrane permeability, resulting in the least
amount of volume excursion during its addition and removal. To test this
hypothesis, theoretical simulations were performed using membrane
permeability coefficients to predict optimal procedures for the addition
and removal of a cryoprotectant. Simulations were performed using data from
four different cryoprotectants: (i) glycerol, (ii) dimethyl sulphoxide,
(iii) propylene glycol and (iv) ethylene glycol. Thermodynamic formulations
were applied to determine approaches for the addition and removal of 1 M
and 2 M final concentrations of cryoprotectant, allowing the spermatozoa to
maintain a cell volume within their osmotic tolerance limits. Based on
these data, ethylene glycol was predicted to be optimal for minimizing
volume excursions among the solutes evaluated. These predictions were then
experimentally tested using glycerol as the control cryoprotectant and
ethylene glycol as the experimental cryoprotectant. The results indicate
that there was a higher (P < 0.05) recovery of motile spermatozoa after
cryopreservation when using 1 M ethylene glycol than with 1 M glycerol,
supporting the hypothesis that use of the cryoprotectant for which the cell
has the highest permeability will result in higher cell survival.
相似文献
26.
Morphological studies have hypothesized different origins for the precursors of the vascular smooth muscle cells (SMCs). The intriguing possibility that intimal SMCs may arise from the endothelium has newly emerged. As a first step towards understanding of the possible mechanisms involved in the transdifferentiation of endothelium into smooth muscle cells, we characterized the in vivo phenotype of the cells located in the aortic wall (distal to the aortic arches). This was accomplished using advanced stages of chicken embryo development. Furthermore, we investigated whether the cells present at the intimal thickening derive from the endothelial cell transdifferentiation. Immunolabeling of serial cryosections suggested that mesenchymal cells observed in the intimal thickening may arise from the endothelium. These cells may persist either as non-muscle throughout the development or possibly convert to cells expressing smooth muscle alpha-actin (SM alpha-actin). To determine whether endothelial cells may actually transdifferentiate into mesenchymal cells, aortic explants from 14-day-old chicken embryos (stage 40) were used. We found that explanted endothelial cells lose their cobblestone-appearance and migrate toward cell-free area. Some of these cells maintain the vWf immunoreactivity, whereas other cells coordinately lose vWf and gain SM alpha-actin expression (transitional cells). Taken together these findings strongly support the possibility that embryonic aortic endothelial transdifferentiate into mesenchymal cells, some of which express SM alpha-actin. Since TGFbeta-3 is considered an essential factor during epithelial to mesenchymal transitions in earlier chicken heart development, we also investigated the distribution of this growth factor at day 14. Our observations indicated that the immunoreactivity for TGFbeta-3 in this stage may be associated with migrating mesenchymal cells and that this immunoreactivity appears to decrease as cell differentiation advances. Therefore, the present study provides evidence that could help to explain 1) the presence of cells displaying a phenotype reminiscent of fetal-like cells in the normal chicken aorta and in the intimal region of the human aorta; 2) the SM lineage diversity in the chicken embryo reported by others; 3) a subpopulation of immature cells in the subendothelial region of the main pulmonary arteries of fetal, neonatal and adult bovines; and 4) the presence of intimal cushions, intimal pads, eccentric and diffuse intimal thickening that are observed in mammalian and avian vessels at birth. 相似文献
27.
Transmission of Pneumocystis carinii DNA from a patient with P. carinii pneumonia to immunocompetent contact health care workers 总被引:1,自引:0,他引:1
Vargas SL Ponce CA Gigliotti F Ulloa AV Prieto S Muñoz MP Hughes WT 《Journal of clinical microbiology》2000,38(4):1536-1538
The transmission of Pneumocystis carinii from person to person was studied by detecting P. carinii-specific DNA in prospectively obtained noninvasive deep-nasal-swab samples from a child with a documented P. carinii pneumonia (PCP), his mother, two contact health care workers, and 30 hospital staff members who did not enter the patient's room (controls). Nested-DNA amplification was done by using oligonucleotide primers designed for the gene encoding the mitochondrial large subunit rRNA of rat P. carinii (P. carinii f. sp. carinii) that amplifies all forms of P. carinii and internal primers specific for human P. carinii (f. sp. hominis). P. carinii f. sp. hominis DNA was detected in samples from the patient and all of his contacts versus none of the 30 hospital staff members. The results, as previously shown in murine models of P. carinii pneumonia, document that person-to-person transmission of P. carinii is possible. This observation suggests that immunocompromised patients not on PCP prophylaxis should not enter the room of a patient with PCP, and it also raises the question as to whether healthy contacts can transmit the disease to immunocompromised patients at risk. 相似文献
28.
Comparison of isolation of Haemophilus vaginalis (Corynebacterium vaginale) from peptone-starch-dextrose agar and Columbia colistin-nalidoxic acid agar.
下载免费PDF全文
![点击此处可从《Journal of clinical microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A total of 447 cervical or vaginal specimens were inoculated in parallel onto peptone-starch-dextrose (PSD) and Columbia colistin (10 mg/ml)-nalidixic acid (15 mug/ml) (CNA) agar and were incubated for 48 h at 35 degrees C in an atmosphere with 2 to 10% CO2. One hundred (22.4%) of the cultures were positive for Haemophilus vaginalis. Forty-eight of the isolates were recovered from both PSD and Columbia CNA agar, five from PSD only, and 47 from Columbia CNA agar only (P less than 0.001). On Columbia CNA agar, 76 of the isolates were detected after 24 h of incubation, and the remainder were detected within 4 days of incubation. 相似文献
29.
30.