全文获取类型
收费全文 | 1721篇 |
免费 | 119篇 |
国内免费 | 22篇 |
专业分类
耳鼻咽喉 | 2篇 |
儿科学 | 153篇 |
妇产科学 | 19篇 |
基础医学 | 194篇 |
口腔科学 | 48篇 |
临床医学 | 170篇 |
内科学 | 399篇 |
皮肤病学 | 25篇 |
神经病学 | 41篇 |
特种医学 | 470篇 |
外科学 | 109篇 |
综合类 | 29篇 |
预防医学 | 56篇 |
眼科学 | 15篇 |
药学 | 66篇 |
中国医学 | 3篇 |
肿瘤学 | 63篇 |
出版年
2022年 | 6篇 |
2021年 | 13篇 |
2020年 | 9篇 |
2019年 | 10篇 |
2018年 | 20篇 |
2017年 | 20篇 |
2016年 | 28篇 |
2015年 | 31篇 |
2014年 | 29篇 |
2013年 | 57篇 |
2012年 | 31篇 |
2011年 | 26篇 |
2010年 | 74篇 |
2009年 | 60篇 |
2008年 | 35篇 |
2007年 | 29篇 |
2006年 | 35篇 |
2005年 | 26篇 |
2004年 | 21篇 |
2003年 | 20篇 |
2002年 | 24篇 |
2001年 | 15篇 |
2000年 | 23篇 |
1999年 | 26篇 |
1998年 | 134篇 |
1997年 | 118篇 |
1996年 | 125篇 |
1995年 | 92篇 |
1994年 | 74篇 |
1993年 | 82篇 |
1992年 | 23篇 |
1991年 | 23篇 |
1990年 | 20篇 |
1989年 | 61篇 |
1988年 | 45篇 |
1987年 | 50篇 |
1986年 | 47篇 |
1985年 | 50篇 |
1984年 | 25篇 |
1983年 | 32篇 |
1982年 | 34篇 |
1981年 | 21篇 |
1980年 | 36篇 |
1979年 | 15篇 |
1978年 | 15篇 |
1977年 | 17篇 |
1976年 | 23篇 |
1975年 | 24篇 |
1971年 | 2篇 |
1966年 | 2篇 |
排序方式: 共有1862条查询结果,搜索用时 15 毫秒
91.
Tamoxifen and its analogues 4-hydroxytamoxifen, toremifene, 4-
hydroxytoremifene, clomifene and droloxifene were tested for clastogenic
effects in a human lymphoblastoid cell line (MCL-5) expressing elevated
native CYP1A1 and containing transfected CYP1A2, CYP2A6, CYP2E1 and CYP3A4
and epoxide hydrolase and in a cell line containing only the viral vector
(Ho1). MCL-5 or Ho1 cells were incubated with 4-hydroxytamoxifen,
4-hydroxytoremifene, clomifene or droloxifene and the incidence of
micronuclei estimated. With MCL-5 cells there was an increase in
micronuclei with 4-hydroxytamoxifen, 4- hydroxytoremifene and clomifene but
not with droloxifene. With Ho1 cells only 4-hydroxytamoxifen and
4-hydroxytoremifene caused an increase in micronuclei. MCL-5 cells were
incubated with tamoxifen, 4- hydroxytamoxifen, toremifene, droloxifene,
clomifene or diethylstilbestrol (0.25-10 microg/ml) for 48 h and subjected
to 3 h treatment with vinblastine (0.25 microg/ml) to arrest cells in
metaphase. The incidence of cells with chromosomal numerical aberrations
(aneuploidy) was increased in cells treated with tamoxifen,
4-hydroxytamoxifen, toremifene, clomifene and diethylstilbestrol but not
droloxifene. The frequency of cells with structural abnormalities
(excluding gaps) was increased in cells treated with tamoxifen and
toremifene but not 4-hydroxytamoxifen, clomifene, droloxifene or
diethylstilbestrol. The clastogenic activities of tamoxifen (35 mg/kg),
toremifene (36.3 mg/kg), droloxifene (35.2 mg/kg) and diethylstilbestrol
(25 mg/kg) were compared in groups of four female Wistar rats. Each
chemical was dissolved in glycerol formal, administered as a single dose by
gavage and hepatocytes isolated by collagenase perfusion 24 h later. The
cells were cultured in the presence of epidermal growth factor (40 ng/ml)
for 48 h, colchicine (10 microg/ml) being added for the final 3 h of
incubation. At least 100 chromosomal spreads were examined from each animal
for the presence of numerical and structural abnormalities. The incidences
of aneuploidy following treatment were: tamoxifen 81%, toremifene 46%,
droloxifene 9.6%, diethylstilbestrol 45.7%, vehicle control 5.3%. The
incidences of chromosomal structural abnormalities excluding gaps were:
tamoxifen 4.3%, toremifene 0.8%, droloxifene 0.5%, diethylstilbestrol 0.8%,
control 0.5%. The incidence of chromosomal structural aberrations excluding
gaps in the treated animals was not statistically significantly different
from controls except in the tamoxifen-treated group. Tamoxifen (35 mg/kg
per os) and toremifene (36.3 mg/kg per os) were dosed to rats for 4 weeks
and chromosomal spreads made from hepatocytes. The incidences of aneuploidy
were: tamoxifen 94%, toremifene 57%, control 6.5%. The incidences of
chromosomal aberrations excluding gaps were: tamoxifen 12%, toremifene 1%,
control 0.5%. The incidence of tamoxifen-induced chromosomal structural
abnormalities was significantly elevated compared with control levels. The
results demonstrate that tamoxifen and toremifene are the only two drugs
tested in the study that cause chromosomal structural and numerical
aberrations in vitro and tamoxifen is the only drug that induces both these
effects in rat liver cells stimulated to divide in culture following oral
dosing. Since chromosomal mutations require cell division for their
manifestation and tamoxifen is the only compound of those tested that
causes hyperplasia in the rat liver, chromosomal aberrations and aneuploidy
in the rat liver would only be expected to occur following treatment with
tamoxifen alone, although aneuploidy could be induced by toremifene in
conjunction with a promoter such as phenobarbitone.
相似文献
92.
Cytogenetic and molecular genetic analysis of tumorigenic human bronchial epithelial cells induced by radon alpha particles 总被引:4,自引:1,他引:4
To establish a cell culture model for lung carcinogenesis, independent
populations of the human papillomavirus 18-immortalized human bronchial
epithelial cell line BEP2D were treated with high linear energy transfer
radon-simulated alpha-particles, expanded and xenotransplanted into Nu/Nu
mice. Six independent cell lines were established from tumors that
developed from three separate radiation treatments as follows: treatment
(Tx) 1 (30 cGy--two doses), H2BT, Tx 2 (30 cGy-- single dose), R30T1L,
R30T2 and R30T3L, Tx 3 (30 cGy--single dose), H1ATN and H1ATBA1.
Cytogenetic analysis revealed common changes in all tumor lines: loss of
the Y chromosome (ch), one of three copies of ch8, one of three copies of
ch14, and one of two copies of ch4p16-pter and ch11p15-pter. Analysis of
polymerase chain reaction-amplified short tandem repeats of informative
loci confirmed the loss of chY in all lines and loss of heterozygosity
(LOH) at eight loci spanning the length of ch8 in all lines from Tx's 1 and
2. Our data support previous studies indicating the presence of tumor
suppressor genes on ch8. LOH also was confirmed on ch14 at locus D14S306 in
all cell lines from Tx 2 and in one of two lines from Tx 3. This region,
14q12-q13, may contain changes in one of the five known somatostatin
receptor genes (SSTR1). No LOH was detected at any of the informative loci
tested for on ch4 or ch11.
相似文献
93.
94.
JA BATCH 《Journal of paediatrics and child health》1996,32(4):278-280
Abstract: Evidence exists for a potential role for inhaled corticosteroids, particularly when used in high dose to cause growth impairment, delayed maturation and adrenal suppression in children and adolescents with asthma. The functional significance of biochemical adrenal suppression remains uncertain. Similarly, there is as yet insufficient evidence to determine whether inhaled corticosteroids may adversely affect bone mineral density in children and adolescents with asthma. 相似文献
95.
Objective : To review experience of CYP11β1 deficiency (previously known as 11β-hydroxylase) at the Royal Children's Hospital, Melbourne, Victoria.
Methodology : A retrospective case review was conducted from 1974 to 1995 with five cases identified.
Results : Age of presentation ranged from 1 day to 7 years. Presentation was with ambiguous genitatia at birth (two females), simple virilization (two males) and suspected early puberty in mid childhood (one female). Associated clinical features were hypertension (three cases) and tall stature with markedly advanced bone age (four cases). Biochemical abnormalities consistent with CYP11β1-deficiency were elevated urinary tetrahydro-11-deoxycortisol ( n = 5) and elevated serum 11-deoxycortisol ( n = 3). Additional abnormalities were elevated 17-hydroxyprogesterone ( n = 3), elevated androstenedione ( n = 4) and elevated dehydroepiandrosterone sulphate ( n = 4). The clinical features and investigations suggested CYP11β1-classical deficiency in four patients and CYP11β1-non-classical deficiency in one patient.
Conclusions : The five cases of CYP11β1-deficiency demonstrate a spectrum of clinical abnormalities, with diagnostic difficulties in two cases and delayed presentation in three cases. Prompt diagnosis of CYP11β1-deficiency is facilitated greatly by the availability of a gas chromatography-mass spectrometry instrument and is essential to avoid the long-term effects of hypertension and hyperandrogenism. 相似文献
Methodology : A retrospective case review was conducted from 1974 to 1995 with five cases identified.
Results : Age of presentation ranged from 1 day to 7 years. Presentation was with ambiguous genitatia at birth (two females), simple virilization (two males) and suspected early puberty in mid childhood (one female). Associated clinical features were hypertension (three cases) and tall stature with markedly advanced bone age (four cases). Biochemical abnormalities consistent with CYP11β1-deficiency were elevated urinary tetrahydro-11-deoxycortisol ( n = 5) and elevated serum 11-deoxycortisol ( n = 3). Additional abnormalities were elevated 17-hydroxyprogesterone ( n = 3), elevated androstenedione ( n = 4) and elevated dehydroepiandrosterone sulphate ( n = 4). The clinical features and investigations suggested CYP11β1-classical deficiency in four patients and CYP11β1-non-classical deficiency in one patient.
Conclusions : The five cases of CYP11β1-deficiency demonstrate a spectrum of clinical abnormalities, with diagnostic difficulties in two cases and delayed presentation in three cases. Prompt diagnosis of CYP11β1-deficiency is facilitated greatly by the availability of a gas chromatography-mass spectrometry instrument and is essential to avoid the long-term effects of hypertension and hyperandrogenism. 相似文献
96.
JA Batch HR Davies BA Evans IA Hughes MN Patterson 《Archives of disease in childhood》1993,68(4):453-457
The partial androgen insensitivity syndrome occurs in 46,XY subjects with phenotypes ranging from perineoscrotal hypospadias with cryptorchidism and micropenis (mild undervirilisation) to clitoromegaly and partial labial fusion (marked undervirilisation). Within an affected family, wide variation in the degree of genital ambiguity between individuals can be seen. Two cousins of a previously reported subject who had severe genital ambiguity and partial androgen insensitivity were investigated. Neither of the cousins had genital abnormalities as marked as the index case, who also had qualitatively abnormal androgen binding and two mutations of the androgen receptor gene. Despite marked phenotypic differences between the index case and his cousins, similar androgen binding and the same androgen receptor mutations were shown in the cousins. Furthermore, one of the androgen receptor gene mutations has been shown in the mother and sister of one of the boys indicating that they are carriers. Thus phenotypic variation in families affected by partial androgen insensitivity is dependent on factors other than abnormalities of the androgen receptor gene alone. Although carrier status in partial androgen insensitivity can be determined, the severity of genital abnormalities in an affected offspring cannot be reliably predicted. 相似文献
97.
Twenty nine patients, aged 5-16 years, were studied to evaluate whether biofeedback training is effective in treating children with chronic constipation and encopresis; the clinical outcome at six weeks and 12 months was also evaluated. Patients received on average five biofeedback training sessions. The existence of external anal contraction or decreased rectal sensation in 16 (55%) and eight (27%) of the children, respectively was identified on manometry. After biofeedback training, 26 (90%) of the patients learned to relax the external anal sphincter; 18 (63%) normalised rectal sensation. The training resulted in a significant increase in defecation frequency and a significant decrease in encopresis. At six weeks, 16 (55%) of the patients were clinically symptom free. At follow up after 12 months the results were sustained. Only three patients showed a relapse within six months, of whom two were successfully treated with one extra training session. Biofeedback training might be a useful therapeutical approach in children with chronic constipation and encopresis. 相似文献
98.
M Cole L Parker AW Craft S Bell G Dale AC McGill JA Seviour J Smith 《Archives of disease in childhood》1993,68(3):376-378
The relationship between homovanillic acid (HVA), vanillylmandelic acid (VMA), and creatinine in the urine of 6 month old babies has been studied and reference ranges in the form of centiles constructed for HVA and VMA against creatinine. Over 10,000 urine samples were collected from babies in four health districts in the north of England. HVA and VMA concentration, either independently or when divided by creatinine concentration, were dependent upon the absolute concentration of creatinine in the sample. After adjustment for creatinine significant differences in the mean concentration of HVA were found between sexes. No such differences were found for VMA. HVA and VMA were also found to be age dependent. Centiles were constructed using a procedure which makes no distributional assumptions about the data. The net effect of utilising these centiles was to increase the predictive value of a positive screening test from 20% to 40% without any increase in the false negative rate. 相似文献
99.
NA Bridges JA Christopher PC Hindmarsh CG Brook 《Archives of disease in childhood》1994,70(2):116-118
The aetiology of 197 girls and 16 boys presenting with sexual precocity was reviewed. Ninety one girls and four boys had central precocious puberty (M:F 23:1); a cause was identified in all the boys but in only six girls. All boys with precocious puberty need detailed investigation; in girls investigation should be based on clinical findings, particularly the consonance of puberty. 相似文献
100.