全文获取类型
收费全文 | 1839篇 |
免费 | 95篇 |
国内免费 | 14篇 |
专业分类
耳鼻咽喉 | 23篇 |
儿科学 | 61篇 |
妇产科学 | 16篇 |
基础医学 | 163篇 |
口腔科学 | 42篇 |
临床医学 | 213篇 |
内科学 | 440篇 |
皮肤病学 | 11篇 |
神经病学 | 168篇 |
特种医学 | 203篇 |
外国民族医学 | 1篇 |
外科学 | 272篇 |
综合类 | 64篇 |
一般理论 | 1篇 |
预防医学 | 105篇 |
眼科学 | 17篇 |
药学 | 80篇 |
1篇 | |
中国医学 | 7篇 |
肿瘤学 | 60篇 |
出版年
2020年 | 14篇 |
2018年 | 11篇 |
2017年 | 11篇 |
2016年 | 15篇 |
2015年 | 16篇 |
2014年 | 21篇 |
2013年 | 30篇 |
2012年 | 60篇 |
2011年 | 68篇 |
2010年 | 47篇 |
2009年 | 36篇 |
2008年 | 44篇 |
2007年 | 67篇 |
2006年 | 83篇 |
2005年 | 75篇 |
2004年 | 48篇 |
2003年 | 66篇 |
2002年 | 55篇 |
2001年 | 63篇 |
2000年 | 62篇 |
1999年 | 63篇 |
1998年 | 39篇 |
1997年 | 33篇 |
1996年 | 29篇 |
1995年 | 37篇 |
1994年 | 28篇 |
1993年 | 39篇 |
1992年 | 45篇 |
1991年 | 26篇 |
1990年 | 49篇 |
1989年 | 54篇 |
1988年 | 47篇 |
1987年 | 69篇 |
1986年 | 50篇 |
1985年 | 59篇 |
1984年 | 29篇 |
1983年 | 41篇 |
1982年 | 21篇 |
1981年 | 25篇 |
1980年 | 23篇 |
1979年 | 34篇 |
1978年 | 25篇 |
1977年 | 24篇 |
1976年 | 22篇 |
1975年 | 12篇 |
1974年 | 14篇 |
1973年 | 17篇 |
1972年 | 10篇 |
1971年 | 12篇 |
1969年 | 10篇 |
排序方式: 共有1948条查询结果,搜索用时 46 毫秒
111.
Ki-ras mutations are an early event and correlate with tumor stage in transplacentally-induced murine lung tumors 总被引:2,自引:2,他引:2
Leone-Kabler S; Wessner LL; McEntee MF; D'Agostino RB Jr; Miller MS 《Carcinogenesis》1997,18(6):1163-1168
A previous study from this laboratory demonstrated that treatment of
pregnant mice with 3-methylcholanthrene (MC) caused lung tumors in the
offspring at 1 year after birth, the incidence of which correlated with
fetal inducibility of Cyp1a1. Analysis by PCR amplification and allele-
specific hybridization (ASO) of paraffin-embedded tumors generated from
that study revealed the presence of point mutations in exon 1 of the Ki-
ras gene. This work has now been expanded by PCR amplification and ASO
analysis of 31 additional lesions. Point mutations were found in 37 of the
47 (79%) lesions analyzed in this and the previous study, the majority of
which were G-->T transversions in the first or second base of codon 12.
The mutational spectrum appeared to be dependent on the relative stage of
differentiation of the lesion, as both the incidence of mutation and type
of mutation produced correlated with malignant progression. Mutations
occurred in 60% of the hyperplasias, 80% of the adenomas and 100% of the
adenocarcinomas. In the lesions with mutations, GLY12-->CYS12
transversions occurred in 100% of the hyperplasias, 42% of the adenomas and
14% of the adenocarcinomas. The GLY12-->VAL12 transversions occurred in
none of the hyperplasias, 42% of the adenomas and 57% of the
adenocarcinomas. The remaining mutations, which consisted of ASP12
transitions and ARG13 transversions, occurred only in adenomas (17%) and
adenocarcinomas (29%). Between this study and our previous analyses, the
identity of the mutations obtained by ASO were confirmed by sequence
analysis of eight of the 37 lesions that harbored mutations at the Ki-ras
gene locus. There were no differences in the type or incidence of mutations
relative to the metabolic phenotype or sex of the mice. These data suggest
that mutational activation of the Ki-ras gene locus is an early event in
transplacental lung tumorigenesis, and that the type of mutations produced
by exposure to chemical carcinogens can influence the carcinogenic
potential of the tumor. This may have prognostic significance in
determining the malignant progression of the neoplasm.
相似文献
112.
AS Grumach RC Carmona D Lazarotti MA Ribeiro RB Rozentraub ML Racz A Weinberg MMS Carneiro-Sampaio 《Acta paediatrica (Oslo, Norway : 1992)》1993,82(3):284-290
Breast milk samples from three groups of Brazilian women were evaluated: G1, mothers delivering term babies of low birth weight (n=16); G2, mothers delivering preterm babies of appropriate birth weight (n = 20); G3, mothers delivering term babies of appropriate birth weight ( n = 30). Milk samples were obtained at 48 h and on the 7th, 15th, 30th and 60th days after delivery and they were analyzed for lysozyme and total IgA levels and for the presence of specific antibodies against Poliovirus types I, II, III, Rotavirus, Herpes simplex virus, Varicella zoster and Cytomegalovirus. The groups were not statistically different in relation to mother's age, parity, type of delivery or socio-economic levels. IgA levels were higher in both low-birth-weight groups (G1 & G2) compared to the control group (G3) throughout the study period. Lysozyme levels decreased up to the 15th day, increasing thereafter up to the 60th day in all groups. Specific antibodies were detected throughout the study period, with no differences among groups. We conclude that breast milk composition of mothers delivering low-birth-weight babies (G1 & G2) was similar despite the different gestational ages. 相似文献
113.
Marks LB Bentel G Light K Zhou SM Sibley G Anscher M 《Oncology (Williston Park, N.Y.)》2000,14(8):1191-201; discussion 1201, 1205-8
Three-dimensional (3D) treatment planning refers to the use of software and hardware tools to design and implement more accurate and conformal radiation therapy. This is a major advance in oncology that should lead to the reduction of treatment-associated morbidity and facilitate safe dose escalation for many tumor sites. This technology affords the incorporation of physiologic and anatomic information into the treatment planning process, further enhancing our ability to improve the therapeutic ratio. However, as with any new technology, care must be taken when applying it in the clinic. The introduction of 3D planning presents new challenges to existing quality assurance systems. These need to be addressed to maintain patient safety. Based on our experience with over 1,500 patients treated at Duke University, the benefits, challenges, and hazards of routine 3D treatment planning are discussed. 相似文献
114.
Early pregnancy complications: endovaginal sonographic findings correlated with human chorionic gonadotropin levels 总被引:2,自引:0,他引:2
Endovaginal sonography results were compared with quantitatively determined human chorionic gonadotropin (hCG) levels in 84 women referred for early pregnancy complications. Of the 27 with normal intrauterine pregnancies, an intrauterine gestational sac was prospectively identified in one of five cases (20%) in which hCG levels were below 500 IU/L (Second International Standard), four of five (80%) with hCG levels of 500-1,000 IU/L, and all 17 with hCG levels above 1,000 IU/L. In comparison, 17 of the 26 women with ectopic pregnancies (65%) had hCG levels greater than 1,000 IU/L, and none of the 26 had an intrauterine gestational sac. Endovaginal sonography demonstrated an adnexal mass and/or a gestational sac-like structure in 16 of the 17 cases (94%) in which hCG levels were above 1,000 IU/L, compared with only three of the nine (33%) with lower hCG levels (P less than .01). These findings indicate that an intrauterine gestational sac should be normally visualized with endovaginal sonography when the hCG level exceeds 1,000 IU/L, and that visualization of an extrauterine gestational sac and/or adnexal mass is significantly more likely in ectopic pregnancies when the hCG level exceeds 1,000 IU/L. 相似文献
115.
116.
Intragastric Intubation of Alcohol During Postnatal Development of Rats Results in Selective Cell Loss in the Cerebellum 总被引:1,自引:0,他引:1
Dwight R. Pierce Dellan C. Serbus Kim E. Light 《Alcoholism, clinical and experimental research》1993,17(6):1275-1280
Postnatal alcohol exposure produces reductions in the number of Purkinje cells in the rat cerebellum. The goal of this study was to determine if the method of postnatal alcohol exposure would influence the degree of vulnerability of the Purkinje cells. Previously reported studies from other laboratories have demonstrated cerebellar Purkinje cell count reductions following postnatal alcohol exposure via artificial rearing and vapor inhalation techniques. This study used gastric intubation to administer alcohol (3.6 g ethanol/kg body weight, bid) to male rat pups from postnatal days 4–10. Peak blood alcohol levels were 203 ± 12.7 mg/dl on postnatal day 6. On postnatal day 10, the animals were perfused, and brain weights were obtained. Body weight was not significantly altered by the postnatal alcohol exposure, yet the wet weights of the cerebral cortex and whole brain were significantly reduced. Although the cerebellar weight was not significantly reduced, the overall number of Purkinje cells measured in the cerebellar vermis was significantly reduced by 24% compared with the isocaloric and normal control groups. The pattern of vulnerability for the individual cerebellar lobules was similar to the previously reported studies, indicating that alcohol's teratogenicity transcends experimental paradigm and is remarkedly consistent, when relatively similar blood alcohol profiles are established. 相似文献
117.
118.
The AS792 artificial urinary sphincter was implanted in 11 incontinent patients with the epispadias-exstrophy complex. To date 10 patients (91 per cent) are totally continent of urine with normal renal function and intact urinary systems. The recent reports concerning success with bladder neck reconstruction in this syndrome are reviewed. Owing to the relatively poor success of this procedure in achieving total urinary continence it is recommended strongly that insertion of the artificial urinary sphincter be the initial anti-incontinence procedure for these patients. The success rate with the artificial sphincter currently is superior to any form of bladder neck reconstruction in patients with the epispadias-exstrophy complex. 相似文献
119.
120.