全文获取类型
收费全文 | 1003篇 |
免费 | 49篇 |
国内免费 | 47篇 |
专业分类
耳鼻咽喉 | 3篇 |
儿科学 | 52篇 |
妇产科学 | 12篇 |
基础医学 | 99篇 |
口腔科学 | 11篇 |
临床医学 | 129篇 |
内科学 | 278篇 |
皮肤病学 | 22篇 |
神经病学 | 79篇 |
特种医学 | 167篇 |
外科学 | 65篇 |
综合类 | 24篇 |
预防医学 | 16篇 |
眼科学 | 12篇 |
药学 | 82篇 |
中国医学 | 3篇 |
肿瘤学 | 45篇 |
出版年
2023年 | 4篇 |
2021年 | 9篇 |
2019年 | 4篇 |
2018年 | 6篇 |
2017年 | 15篇 |
2016年 | 7篇 |
2015年 | 29篇 |
2014年 | 23篇 |
2013年 | 29篇 |
2012年 | 23篇 |
2011年 | 28篇 |
2010年 | 37篇 |
2009年 | 32篇 |
2008年 | 22篇 |
2007年 | 54篇 |
2006年 | 21篇 |
2005年 | 18篇 |
2004年 | 16篇 |
2003年 | 11篇 |
2002年 | 24篇 |
2001年 | 24篇 |
2000年 | 12篇 |
1999年 | 20篇 |
1998年 | 49篇 |
1997年 | 47篇 |
1996年 | 56篇 |
1995年 | 31篇 |
1994年 | 36篇 |
1993年 | 26篇 |
1992年 | 13篇 |
1991年 | 15篇 |
1990年 | 18篇 |
1989年 | 43篇 |
1988年 | 35篇 |
1987年 | 32篇 |
1986年 | 27篇 |
1985年 | 23篇 |
1984年 | 24篇 |
1983年 | 16篇 |
1982年 | 21篇 |
1981年 | 13篇 |
1980年 | 19篇 |
1979年 | 18篇 |
1978年 | 9篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1975年 | 12篇 |
1974年 | 3篇 |
1972年 | 6篇 |
1969年 | 3篇 |
排序方式: 共有1099条查询结果,搜索用时 31 毫秒
1.
Changes in latencies of the visual evoked response (VER) during early post-natal development were examined in protein-deprived (PD) rats. The evoked response to light-flash stimulation was recorded in the dorsal lateral geniculate nucleus (dLGN) and on the surface of the visual cortex. In control rats, latencies of the cortical VER decreased rapidly up to 20 days and slowly thereafter. In PD rats, the latencies of the cortical VER were increased by 10-15 ms at 17 days; the developmental decrease was delayed by approximately 3 days. After 20 days, PD rats also went into a phase with slow decrease of the latencies, and the onset latency of the cortical VER was still increased by some 10 ms at 26/27 days. At this age, PD rats showed an increase in the latencies of the VER in the dLGN which was of similar magnitude to that in the cortical VER, indicating that alterations were more marked in the peripheral parts of the visual system at this stage of development. The findings are in agreement with previous studies indicating that there is a delay of visual system development in PD rats before 20 days. A maturational event which turns rapid into slow development at approximately 20 days in both C and PD rats turns this delay into a distortion of development. The delays and distortions of visual system development may be one causative factor for the functional deficit present in the visual cortex of adult PD rats. 相似文献
2.
It was recently shown that an increase in latency of the cortical visual evoked response (VER) seen in young malnourished animals persists in adult rats given a low protein diet. In the present paper the VER latencies of the specific visual pathway were measured in order to establish the level at which the latency increase occurs in protein-deprived rats. The VER in the dorsal lateral geniculate nucleus (dLGN) showed no significant differences to onset or peak latencies between control (C) and the protein-deprived (PD) rats. The dLGN activity was higher in C rats than in PD rats. Late components differed in median values between the two groups, but the individual variations were large. Generally, the VER of the dLGN in PD rats was more stereotype compared with the C rats. Intracortical VER at a depth of 0.4-0.5 mm showed a small negative component of short onset latency in both C and PD rats. This component preceded the onset of the initial positivity recorded from the cortical surface by 1-2 ms in C rats and by 3-6 ms in PD rats. Following electrical stimulation of the dLGN, no differences in onset latency of the first cortical activity (monosynaptic response) were recorded between C and PD rats, whereas later activity was significantly delayed in PD compared with C rats. The laminar potential pattern was less distinct in PD compared with C rats, and the late components of the evoked response from deep cortical layers were markedly attenuated or lacking.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
3.
HJ Aubin S Tilikete C Laureaux HT Nguyen Hac MC Roullet-Volmi S Troupel D Barrucand 《European psychiatry》1995,10(8)
The aim of this study was to assess alcoholic inpatients' smoking and coffee intake variation following withdrawal. Only moderate smokers (less than 30 cigarettes/day) showed a significant increase of cigarette consumption after alcohol withdrawal. However, their urinary cotinine level did not vary, suggesting a behavioral, and not biological, compensation through smoking following alcohol withdrawal. Heavy smokers (30 cigarettes/day or more) showed no significant clinical or biological variation of smoking behavior. Coffee consumption increased after alcohol withdrawal in all patients, irrespective of smoking habits. 相似文献
4.
BACKGROUND: A simple, rapid, inexpensive method for measuring the flow in a
patient's vascular access would permit routine monitoring during
haemodialysis, and hence provide information of access graft deterioration
sufficiently early to increase the success of minimally invasive remedial
procedures. This paper reports the validation of such a method in animals.
METHODS: A PTFE graft was implanted in sheep between the carotid artery and
the jugular vein. While the sheep was under general anaesthesia and on an
haemodialysis circuit, ultrasound velocity in its blood was perturbed by
the injection of a 5-10 ml bolus of isotonic NaCl. The pump tubing flow was
measured by a transit-time blood flow meter. This flow was combined with
the areas of perturbation generated by the injection before and after
mixing in the access flow to estimate graft flow. The calculated graft flow
was compared to flow measured directly by a transit-time probe on the same
carotid artery. RESULTS: Over a 10-fold range, 120-1260 ml/min, graft flow
measured by ultrasound velocity dilution agreed well with graft flow
measured directly with a scatter of 76 ml/min about the regression line.
CONCLUSION: Ultrasound velocity dilution provides a method for measuring
flow in the graft accurate enough for clinical evaluation of patients on
dialysis.
相似文献
5.
M Kaplan HJ Vreman C Hammerman C Leiter B Rudensky MG MacDonald DK Stevenson 《Acta paediatrica (Oslo, Norway : 1992)》1998,87(4):455-457
The incidence (%) of hyperbilirubinemia (serum bilirubin ≥257 μmol/l) was similar in neonates with a combination of ABO incompatibility and glucose-6-phosphate dehydrogenase (G-6-PD) deficiency (45%), with ABO incompatibility (54%) or G-6-PD deficiency (37%), alone (ns). Carboxyhemoglobin values, corrected for inspired CO, were similarly elevated in all three groups (0.87 ± 0.32%, 0.82 ± 0.29%, 0.76 ± 0.18%, respectively, ns), but correlated with bilirubin only in those with ABO incompatibility alone. ABO-incompatible/G-6-PD-deficient neonates, compared with those with either condition alone, are not at increased risk for hemolysis or hyperbilirubinemia. 相似文献
6.
Eleven experiments were conducted on minipigs for the purpose of determining heat distribution in tissue exposed to therapeutic doses of microwaves. Temperatures were measured by means of coated thermocouples from the cutis, subcutis, musculature, and periost. Irradiation was applied to intensities of 10 W, 40 W and 60 W by means of a "Radarmed 12 S 251" circular emitter and to 60 W, 100 W and 140 W, using a trough emitter. Maximum temperature in superficial tissue layers was reached after five to ten minutes of microwave exposure. The temperature rise in the cutis and subcutis was steeper and at a higher rate than that in the muscles. Continuation of microwave irradiation did not cause any further rise in temperature, which was attributed to induction of hyperaemia. No difference regarding heat distribution was found to exist between pulsed and continuous irradiation at equal wattage. 相似文献
7.
A brief case report is presented describing a patient who unknowingly ingested a fatal amount of paraquat, presumably mixed in some illicit moonshine alcohol. Despite an initial clinical presentation typical of paraquat intoxication, the herbicide was absent upon analysis of multiple urine and blood specimens, and the diagnosis was confirmed only postmortem after determination of high paraquat tissue concentrations in all the major organs. Autopsy results are presented along with a discussion of the histopathologic changes observed in the lungs, liver, and kidneys. Because the combination of toxicologic sequelae attributable to acute paraquat poisoning is fairly unique to this agent, the diagnosis must be suspected highly early in the clinical course of such cases and appropriate therapy initiated, despite the inability to isolate paraquat on preliminary laboratory screening. 相似文献
8.
The effects of co-culture with human fibroblasts on human embryo development in vitro and implantation 总被引:5,自引:0,他引:5
Wetzels AM; Bastiaans BA; Hendriks JC; Goverde HJ; Punt-van der Zalm AP; Verbeet JG; Braat DD 《Human reproduction (Oxford, England)》1998,13(5):1325-1330
In a human in-vitro fertilization (IVF) programme, the effect of co-
culture of embryos with human fibroblasts was evaluated with respect to
pregnancy rate and embryo development. Patients were included in the study
after giving informed written consent. The IVF treatments were randomly
assigned by stratification of both age (<36 versus > or =36 years)
and previous IVF attempts (yes versus no). After fertilization was
established, the zygotes were transferred to a 4-well dish with or without
fibroblasts and cultured for 2 days. On the third day after ovum pick-up
(OPU), cell number and quality [5 (good) to 1 (poor)] of the embryos were
scored and a maximum of three embryos was transferred. Supernumerary
embryos of good quality were cryopreserved. The design of this study was a
group sequential trial with the objective of detecting differences between
pregnancy rates following IVF with conventional incubation or incubation in
co-culture with fibroblasts. This design included one evaluation at
half-way data collection. In the study, 148 patients had an OPU, of whom 77
were allocated to the co-culture group. There was no statistically
significant difference in pregnancy rate, cell number and embryo quality
between the two groups. The ongoing pregnancy rate per embryo transfer was
27% in co-culture and 30% in the conventional culture group. The
implantation rates per transferred embryo were 17 and 18% respectively.
Using a multivariate logistic regression model for the probability of
ongoing pregnancies, the odds ratio of co-culture, adjusted for age and
previous IVF attempts, was not statistically significant. In conclusion,
co-culture with human fibroblasts does not contribute to an improvement of
embryo quality nor to a higher pregnancy rate after IVF in an unselected
group of patients.
相似文献
9.
Endothelin receptor expression in human decidua 总被引:3,自引:1,他引:3
Kohnen G; Campbell S; Irvine GA; Church HJ; MacLachlan F; Titterington M; Cameron IT 《Molecular human reproduction》1998,4(2):185-193
The endothelins are signalling peptides that act via two receptors, ET(A)
and ET(B). In the human endometrium, endothelin receptors have been
demonstrated in glands and stroma and have been shown to vary during the
course of the menstrual cycle. The present study was undertaken to
determine whether or not expression of endothelin receptors changes during
pregnancy or after administration of exogenous progestagens. The expression
of the receptors was correlated with the appearance of basement membrane
components during decidualization of the endometrial stroma. Decidual
specimens (n = 15) were obtained during the first trimester of pregnancy
and 10 at term. Sixteen pairs of endometrial biopsies were obtained from
women with menorrhagia before and after exposure to exogenous progestagens.
A total of 15 hysterectomy specimens were used as controls for the
expression of stromal basement membrane proteins in the absence of
decidualization. Autoradiography was carried out with selective ligands for
ET(A) ([125I]-PD 151242) and ET(B) ([125I]-BQ3020). The distribution of
ligand binding was then compared with the distribution of laminin alpha2
light chain and collagen IV. ET(A), ET(B), laminin alpha2 light chain, and
collagen IV were expressed in stromal decidual cells in the first trimester
of pregnancy. ET(B) was also found on endometrial glandular epithelium.
Quantitative macro-autoradiography and multiple regression analysis
demonstrated a highly significant positive correlation (P < 0.001)
between expression of ET(B) and laminin alpha2 light chain. In the third
trimester qualitative examination suggested a reduction of ET(A) in the
stroma. Progestagen-induced decidua exhibited a similar pattern to that
found in first trimester decidua. This study has demonstrated up-regulation
of ET(B) during the progesterone- dependent process of decidualization and
suggests a paracrine or autocrine role for endothelins in the decidua.
相似文献
10.
Induction of a differentiated ciliated cell phenotype in primary cultures of Fallopian tube epithelium 总被引:5,自引:1,他引:5
Human Fallopian tubal epithelial cells in culture lose morphological
features associated with the epithelium in situ and the extent to which
they retain their in-vivo phenotype or function is unknown. In order to
address this question, immunocytochemical markers were identified which
distinguish secretory (HMFG2+, LhS28-) from ciliated (HMFG2-, LhS28+)
epithelial cells in tissue sections of Fallopian tube. These markers were
used to analyse the phenotype of tubal cells in vitro. Primary cultures of
human tubal epithelial cells were seeded onto glass and grown to confluence
before addition of oestradiol-17beta. In the absence of hormone, tubal
epithelial cells expressed cytokeratins and nuclear receptors for oestrogen
and progesterone and adopted a homogeneous (HMFG2+, LhS28-) secretory cell
phenotype. Following the addition of oestradiol-17beta, a proportion of
cells became positive for LhS28. The induction of a ciliated epithelial
cell phenotype was confirmed by scanning electron microscopy, where on
permeable collagen membranes, approximately one-third of tubal epithelial
cells became ciliated in the presence of oestradiol-17beta. We suggest that
in vitro, tubal epithelial cells adopt an immature secretory-like phenotype
and that oestrogen can induce differentiation to a ciliated epithelial cell
phenotype.
相似文献