全文获取类型
收费全文 | 642篇 |
免费 | 19篇 |
国内免费 | 9篇 |
专业分类
耳鼻咽喉 | 1篇 |
儿科学 | 42篇 |
妇产科学 | 9篇 |
基础医学 | 54篇 |
口腔科学 | 9篇 |
临床医学 | 46篇 |
内科学 | 185篇 |
皮肤病学 | 10篇 |
神经病学 | 4篇 |
特种医学 | 132篇 |
外科学 | 110篇 |
综合类 | 12篇 |
预防医学 | 12篇 |
眼科学 | 2篇 |
药学 | 20篇 |
1篇 | |
中国医学 | 6篇 |
肿瘤学 | 15篇 |
出版年
2022年 | 3篇 |
2021年 | 14篇 |
2020年 | 4篇 |
2019年 | 9篇 |
2018年 | 14篇 |
2017年 | 9篇 |
2016年 | 4篇 |
2015年 | 5篇 |
2014年 | 13篇 |
2013年 | 14篇 |
2012年 | 10篇 |
2011年 | 8篇 |
2010年 | 29篇 |
2009年 | 23篇 |
2008年 | 17篇 |
2007年 | 21篇 |
2006年 | 19篇 |
2005年 | 9篇 |
2004年 | 12篇 |
2003年 | 12篇 |
2002年 | 10篇 |
2001年 | 15篇 |
2000年 | 10篇 |
1999年 | 8篇 |
1998年 | 28篇 |
1997年 | 29篇 |
1996年 | 41篇 |
1995年 | 37篇 |
1994年 | 35篇 |
1993年 | 19篇 |
1992年 | 4篇 |
1991年 | 15篇 |
1990年 | 5篇 |
1989年 | 18篇 |
1988年 | 24篇 |
1987年 | 19篇 |
1986年 | 17篇 |
1985年 | 19篇 |
1984年 | 12篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1973年 | 2篇 |
1959年 | 1篇 |
排序方式: 共有670条查询结果,搜索用时 10 毫秒
1.
Pulmonary hamartomas are usually an incidental finding and range in size from 1 cm to 8 cm in diameter in various series. We report a case of a massive pulmonary hamartoma (size 25.5 × 17.5 × 6.5 cm and weighing 1134 g) in a 61 year old male who presented with a short history of breathlessness. The tumour was arising from the medial border of the right lung and occupying most of the right chest extending in to the anterior mediastinum. The tumour was compressing the right lung and there was no evidence of infiltration into the surrounding structures. It was successfully treated by surgical resection and final histology was pulmonary hamartoma with predominantly adipose and leiomyomatous differentiation. 相似文献
2.
Intestinal schistosomiasis japonica: CT-pathologic correlation 总被引:1,自引:0,他引:1
Lee RC; Chiang JH; Chou YH; Rubesin SE; Wu HP; Jeng WC; Hsu CC; Tiu CM; Chang T 《Radiology》1994,193(2):539
3.
The effects of antioxidant supplementation during Percoll preparation on human sperm DNA integrity 总被引:20,自引:6,他引:20
Hughes CM; Lewis SE; McKelvey-Martin VJ; Thompson W 《Human reproduction (Oxford, England)》1998,13(5):1240-1247
The integrity of sperm DNA is crucial for the maintenance of genetic
health. A major source of damage is reactive oxygen species (ROS)
generation; therefore, antioxidants may afford protection to sperm DNA. The
objectives of the study were, first, to measure the effects of antioxidant
supplementation in vitro on endogenous DNA damage in spermatozoa using the
single cell gel electrophoresis (comet) assay and, second, to assess the
effect of antioxidant supplementation given prior to X-ray irradiation on
induced DNA damage. Spermatozoa from 150 patients were prepared by Percoll
centrifugation in the presence of ascorbic acid (300, 600 microM), alpha
tocopherol (30, 60 microM), urate (200, 400 microM), or acetyl cysteine (5,
10 microM). DNA damage was induced by 30 Gy X-irradiation. DNA strand
breakage was measured using the comet assay. Sperm DNA was protected from
DNA damage by ascorbic acid (600 microM), alpha tocopherol (30 and 60
microM) and urate (400 microM). These antioxidants provided protection from
subsequent DNA damage by X-ray irradiation. In contrast, acetyl cysteine or
ascorbate and alpha tocopherol together induced further DNA damage.
Supplementation in vitro with the antioxidants ascorbate, urate and alpha
tocopherol separately has beneficial effects for sperm DNA integrity.
相似文献
4.
Detection of chromosomes and estimation of aneuploidy in human spermatozoa using fluorescence in-situ hybridization 总被引:11,自引:0,他引:11
The development and application of fluorescence in-situ hybridization
(FISH) has opened the way for comprehensive studies on numerical chromosome
abnormalities in human spermatozoa. FISH can be rapidly applied to large
numbers of spermatozoa and thus overcomes the major limitation of
karyotyping spermatozoa after penetration of zona-free hamster oocytes. The
simultaneous hybridization of two or more chromosome-specific probes to
spermatozoa and subsequent detection of the bound probes using different
fluorescent detection systems enables two or more chromosomes to be
localized simultaneously in the same spermatozoon and provides a technique
for undertaking reasonable estimates of aneuploidy. The most commonly used
probes are those which bind to the centromeric region of specific
chromosomes. Most studies to date have concentrated on estimating
aneuploidy in spermatozoa from normospermic men, although reports are
beginning to appear on aneuploidy in spermatozoa from subfertile and
infertile men. Multi- probe FISH studies have generally reported disomy
(hyperhaploidy) estimates of 0.05-0.2% per chromosome. There is preliminary
evidence that some chromosomes such as X, Y and 21 are predisposed towards
higher rates of non-disjunction during spermatogenesis. There are also
suggestions of inter-donor variability in aneuploidy frequencies for
specific chromosomes, although this requires confirmation in larger
studies. While FISH is clearly a powerful technique that has many
applications in reproductive medicine, it must also be realized that it
does have limitations and the technology itself is still evolving and has
yet to be fully validated on spermatozoa.
相似文献
5.
6.
Debelenko LV; Brambilla E; Agarwal SK; Swalwell JI; Kester MB; Lubensky IA; Zhuang Z; Guru SC; Manickam P; Olufemi SE; Chandrasekharappa SC; Crabtree JS; Kim YS; Heppner C; Burns AL; Spiegel AM; Marx SJ; Liotta LA; Collins FS; Travis WD; Emmert-Buck MR 《Human molecular genetics》1997,6(13):2285-2290
Lung carcinoids occur sporadically and rarely in association with multiple
endocrine neoplasia type 1 (MEN1). There are no well defined genetic
abnormalities known to occur in these tumors. We studied 11 sporadic lung
carcinoids for loss of heterozygosity (LOH) at the locus of the MEN1 gene
on chromosome 11q13, and for mutations of the MEN1 gene using dideoxy
fingerprinting. Additionally, a lung carcinoid from a MEN1 patient was
studied. In four of 11 (36%) sporadic tumors, both copies of the MEN1 gene
were inactivated. All four tumors showed the presence of a MEN1 gene
mutation and loss of the other allele. Observed mutations included a 1 bp
insertion, a 1 bp deletion, a 13 bp deletion and a single nucleotide
substitution affecting a donor splice site. Each mutation predicts
truncation or potentially complete loss of menin. The remaining seven
tumors showed neither the presence of a MEN1 gene mutation nor 11q13 LOH.
The tumor from the MEN1 patient showed LOH at chromosome 11q13 and a
complex germline MEN1 gene mutation. The data implicate the MEN1 gene in
the pathogenesis of sporadic lung carcinoids, representing the first
defined genetic alteration in these tumors.
相似文献
7.
A prospective study of methylenetetrahydrofolate reductase and methionine synthase gene polymorphisms, and risk of colorectal adenoma 总被引:8,自引:2,他引:8
Chen J; Giovannucci E; Hankinson SE; Ma J; Willett WC; Spiegelman D; Kelsey KT; Hunter DJ 《Carcinogenesis》1998,19(12):2129-2132
We examined the relationship between a functional polymorphism (667C--
>T, ala-->val) of the methylenetetrahydrofolate reductase gene
(MTHFR) and the risk of colorectal adenomas in the prospective Nurses'
Health Study. Among 257 incident polyp cases and 713 controls, the MTHFR
val/val polymorphism [relative risk (RR) = 1.35, 95% confidence interval
(CI) 0.84-2.17] was not significantly associated with risk of adenomas.
This lack of association was observed for both small (RR = 1.36, 95% CI
0.76-2.45) and large (RR = 1.32, 95% CI 0.66-2.66) adenomas. Furthermore,
there was no significant interaction between this polymorphism and
consumption of either folate, methionine or alcohol. We also examined the
relationship of a newly identified polymorphism (asp919gly) of the
methionine synthase gene (MS) with the risk of colorectal adenomas in the
same population. The MS gly/gly polymorphism was also not significantly
associated with risk of colorectal adenomas (RR = 0.66, 95% CI 0.26-1.70).
These results, which need to be confirmed in other studies, suggest that
the MTHFR val/val polymorphism, which has been previously inversely
associated with risk of colorectal cancer, plays a role only in a late
stage (adenoma-- >carcinoma) of colorectal tumorigenesis, and/or may
protect against malignant transformation in the subset of benign adenomas,
which may progress to malignancy.
相似文献
8.
9.
10.
Transforming growth factor beta (TGF-beta) is a bifunctional regulator of the growth of myeloid progenitors and is here demonstrated to directly inhibit the growth of primitive erythroid progenitors by 95% to 100% regardless of the cytokines stimulating growth. Autocrine TGF- beta production of primitive hematopoietic progenitors has previously been reported. In the present study, a neutralizing TGF-beta antibody (anti-TGF-beta) added to serum-containing cultures, resulted in a 3-, 4- , and 25-fold increase in burst-forming unit erythroid (BFU-E) colony formation in response to interleukin-4 (IL-4) plus erythropoietin (Epo), SCF plus Epo, and IL-11 plus Epo, respectively. The growth of BFU-E progenitors has been suggested to require a burst-promoting activity in addition to Epo. Accordingly, we observed no BFU-E colony formation in serum-containing cultures in response to Epo alone. In contrast, 50 BFU-E colonies were formed when anti-TGF-beta was included in the culture. In serum-free cultures, Epo also stimulated BFU-E colony formation in the absence of other cytokines, whereas anti-TGF- beta had no effect on the number of colonies formed. Quantitation of TGF-beta 1 in serum by an enzyme-linked immunosorbent assay method showed predominantly the presence of precursor (latent) TGF-beta 1, but also showed active TGF-beta 1 at a concentration sufficient to potently inhibit erythroid colony formation. Thus, neutralization of active TGF- beta 1 in serum shows that Epo alone is sufficient to stimulate the growth of murine BFU-E progenitors. 相似文献