全文获取类型
收费全文 | 1971篇 |
免费 | 104篇 |
国内免费 | 34篇 |
专业分类
耳鼻咽喉 | 26篇 |
儿科学 | 84篇 |
妇产科学 | 25篇 |
基础医学 | 184篇 |
口腔科学 | 36篇 |
临床医学 | 183篇 |
内科学 | 497篇 |
皮肤病学 | 118篇 |
神经病学 | 81篇 |
特种医学 | 225篇 |
外科学 | 246篇 |
综合类 | 37篇 |
预防医学 | 140篇 |
眼科学 | 14篇 |
药学 | 130篇 |
中国医学 | 3篇 |
肿瘤学 | 80篇 |
出版年
2021年 | 18篇 |
2019年 | 30篇 |
2018年 | 24篇 |
2017年 | 17篇 |
2016年 | 26篇 |
2015年 | 33篇 |
2014年 | 40篇 |
2013年 | 105篇 |
2012年 | 51篇 |
2011年 | 47篇 |
2010年 | 64篇 |
2009年 | 75篇 |
2008年 | 69篇 |
2007年 | 56篇 |
2006年 | 64篇 |
2005年 | 66篇 |
2004年 | 43篇 |
2003年 | 49篇 |
2002年 | 43篇 |
2001年 | 42篇 |
2000年 | 31篇 |
1999年 | 34篇 |
1998年 | 89篇 |
1997年 | 85篇 |
1996年 | 86篇 |
1995年 | 54篇 |
1994年 | 69篇 |
1993年 | 57篇 |
1992年 | 24篇 |
1991年 | 23篇 |
1990年 | 37篇 |
1989年 | 55篇 |
1988年 | 54篇 |
1987年 | 47篇 |
1986年 | 34篇 |
1985年 | 37篇 |
1984年 | 24篇 |
1983年 | 15篇 |
1982年 | 26篇 |
1981年 | 18篇 |
1980年 | 14篇 |
1979年 | 18篇 |
1978年 | 16篇 |
1977年 | 16篇 |
1976年 | 17篇 |
1975年 | 15篇 |
1974年 | 10篇 |
1973年 | 16篇 |
1972年 | 16篇 |
1971年 | 10篇 |
排序方式: 共有2109条查询结果,搜索用时 15 毫秒
31.
Effect of the APOC3 Sst I SNP on fasting triglyceride levels in men heterozygous for the LPL P207L deficiency 总被引:1,自引:0,他引:1
Garenc C Couillard C Laflamme N Cadelis F Gagné C Couture P Julien P Bergeron J 《European journal of human genetics : EJHG》2005,13(10):1159-1165
Lipoprotein lipase (LPL) plays a major role in triglyceride (TG)-rich lipoprotein catabolism. A mutation at codon 207 (P207L) in the exon 5 of the LPL gene has been associated with 50% reduction in postheparin plasma LPL activity and significant increase in plasma TG levels in heterozygous individuals with low HDL. However, heterogeneity in fasting TG concentrations among these carriers suggests that other factors may be involved in the expression of this hypertriglyceridemic state. Indeed, previous studies have shown that the rare S2 allele of the APOC3 Sst I polymorphism was associated with higher concentrations of TG levels in noncarriers of LPL defect. Therefore, we investigated the association of the APOC3 Sst I variant on fasting lipoprotein-lipid levels in a sample of 35 heterozygous men bearing the LPL P207L mutation. Genetic association analyses were performed using the two-genotype groups S1/S1 and S1/S2. The genotype S1/S2 group was characterized by greater plasma cholesterol (plasma-C, P=0.02), plasma-TG (P=0.04), very low-density lipoproteins (VLDL)-C (P=0.004), VLDL-TG (P=0.01), VLDL-apolipoprotein B (apoB) (P=0.001) levels and cholesterol/HDL-C ratio (P=0.008), as well as lower VLDL-TG/VLDL-apoB ratio compared to the S1/S1 genotype group. These results support an exacerbating effect of the APOC3 Sst I single-nucleotide polymorphism on fasting TG levels since a large number of smaller VLDL particles are observed in LPL-deficient men bearing the APOC3 S2 allele. 相似文献
32.
Canfield MC; Tamarappoo BK; Moses AM; Verkman AS; Holtzman EJ 《Human molecular genetics》1997,6(11):1865-1871
Congenital nephrogenic diabetes insipidus (NDI) is a rare disease caused
most often by mutations in the vasopressin V2 receptor (AVPR2). We studied
a family which included a female patient with NDI with symptoms dating from
infancy. The patient responded to large doses of desmopressin (dDAVP) which
decreased urine volume from 10 to 4 I/day. Neither the parents nor the
three sisters were polyuric. The patient was found to be a compound
heterozygote for two novel recessive point mutations in the aquaporin-2
(AQP2) gene: L22V in exon 1 and C181W in exon 3. Residue Cys181 in AQP2 is
the site for inhibition of water permeation by mercurial compounds and is
located near to the NPA motif conserved in all aquaporins. Osmotic water
permeability (Pf) in Xenopus oocytes injected with cRNA encoding C181W-AQP2
was not increased over water control, while expression of L22V cRNA
increased the Pf to approximately 60% of that for wild-type AQP2.
Co-injection of the mutant cRNAs with the wild-type cRNA did not affect the
function of the wild-type AQP2. Immunolocalization of AQP2-transfected CHO
cells showed that the C181W mutant had an endoplasmic reticulum-like
intracellular distribution, whereas L22V and wild-type AQP2 showed endosome
and plasma membrane staining. Water permeability assays showed a high Pf in
cells expressing wild-type and L22V AQP2. This study indicates that AQP2
mutations can confer partially responsive NDI.
相似文献
33.
The role of size, sequence and haplotype in the stability of FRAXA and FRAXE alleles during transmission 总被引:2,自引:5,他引:2
Murray A; Macpherson JN; Pound MC; Sharrock A; Youings SA; Dennis NR; McKechnie N; Linehan P; Morton NE; Jacobs PA 《Human molecular genetics》1997,6(2):173-184
Factors involved in the stability of trinucleotide repeats during
transmission were studied in 139 families in which a full mutation,
premutation or intermediate allele at either FRAXA or FRAXE was
segregating. The transmission of alleles at FRAXA, FRAXE and four
microsatellite loci were recorded for all individuals. Instability within
the minimal and common ranges (0-40 repeats for FRAXA, 0-30 repeats for
FRAXE) was extremely rare; only one example was observed, an increased in
size at FRAXA from 29 to 39 repeats. Four FRAXA and three FRAXE alleles in
the intermediate range (41-60) repeats for FRAXA, 31-60 for FRAXE) were
unstably transmitted. Instability was more frequent for FRAXA intermediate
alleles that had a tract of pure CGG greater than 37 although instability
only occurred in two of 13 such transmissions: the changes observed were
limited to only one or two repeats. Premutation FRAXA alleles over 100
repeats expanded to a full mutation during female transmission in 100% of
cases, in agreement with other published series. There was no clear
correlation between haplotype and probability of expansion of FRAXA
premutations. Instability at FRAXA or FRAXE was more often observed in
conjunction with a second instability at an independent locus suggesting
genomic instability as a possible mechanism by which at least some FRAXA
and FRAXE mutations arise.
相似文献
34.
35.
Identification of group B streptococcal Sip protein, which elicits cross-protective immunity 总被引:12,自引:0,他引:12
Brodeur BR Boyer M Charlebois I Hamel J Couture F Rioux CR Martin D 《Infection and immunity》2000,68(10):5610-5618
A protein of group B streptococci (GBS), named Sip for surface immunogenic protein, which is distinct from previously described surface proteins, was identified after immunological screening of a genomic library. Immunoblots using a Sip-specific monoclonal antibody indicated that a protein band with an approximate molecular mass of 53 kDa which did not vary in size was present in every GBS strain tested. Representatives of all nine GBS serotypes were included in the panel of strains. Cloning and sequencing of the sip gene revealed an open reading frame of 1,305 nucleotides coding for a polypeptide of 434 amino acid residues, with a calculated pI of 6. 84 and molecular mass of 45.5 kDa. Comparison of the nucleotide sequences from six different strains confirmed with 98% identity that the sip gene is highly conserved among GBS isolates. N-terminal amino acid sequencing also indicated the presence of a 25-amino-acid signal peptide which is cleaved in the mature protein. More importantly, immunization with the recombinant Sip protein efficiently protected CD-1 mice against deadly challenges with six GBS strains of serotypes Ia/c, Ib, II/R, III, V, and VI. The data presented in this study suggest that this highly conserved protein induces cross-protective immunity against GBS infections and emphasize its potential as a universal vaccine candidate. 相似文献
36.
- The effects of intrathecally (i.t.) injected substance P (SP), neurokinin A (NKA), [β-Ala8]NKA (4–10) and [MePhe7]neurokinin B (NKB) at T13 thoracic spinal cord level were investigated on renal excretion of water, sodium and potassium in the conscious saline-loaded rat. Antagonists selective for NK1 (RP 67580), NK2 (SR 48968) and NK3 (R 820; 3-indolylcarbonyl-Hyp-Phg-N(Me)-Bzl) receptors were used to characterize the spinal effect of SP on renal function.
- Saline gavage (4.5% of the body weight) enhanced renal excretion of water, sodium and potassium over the subsequent hour of measurement. Whereas these renal responses were not affected by 0.65 nmol SP, the dose of 6.5 nmol SP blocked the natriuretic response (aCSF value 3.9±0.8; SP value 0.7±0.3 μmol min−1, P<0.01) as well as the renal excretion of water (aCSF value 48.9±5.8; SP value 14.5±4.0 μl min−1, P<0.01) and potassium (aCSF value 4.8±0.6; SP value 1.5±0.6 μmol min−1, P<0.01) at 30 min post-injection. SP had no significant effect on urinary osmolality. The SP-induced renal inhibitory effects during the first 30 min were abolished in rats subjected to bilateral renal denervation 1 week earlier or in rats injected i.t. 5 min earlier with 6.5 nmol RP 67580. In contrast, the co-injection of SR 48968 and R 820 (6.5 nmol each) did not affect the inhibitory responses to SP. On their own, these antagonists had no direct effect on renal excretion function. Since SP induced only transient changes in mean arterial blood pressure (−18.8±3.8 mmHg at 1 min and +6.3±2.4 mmHg at 5 min post-injection), it is unlikely that the renal effects of SP are due to systemic haemodynamic changes.
- NKA (6.5 nmol but not 0.65 nmol) produced a transient drop in renal excretion of water (aCSF value 31.2±5.1; NKA value 11.3±4.2 μl min−1, P<0.05), sodium (aCSF value 1.7±0.8; NKA value 0.4±0.2 μmol min−1, P<0.05) and potassium (aCSF value 4.1±0.7; NKA value 1.5±0.4 μmol min−1, P<0.05) at 15 min post-injection. However, the same doses (6.5 nmol) of selective agonists for tachykinin NK2 ([β-Ala8]NKA(4-10)) and NK3 ([MePhe7]NKB) receptors were devoid of renal effects.
- This study provided functional evidence that tachykinins may be involved in the renal control of water and electrolyte excretion at the level of the rat spinal cord through the activation of NK1 receptors and the sympathetic renal nerve.
37.
Prat A Biernacki K Pouly S Nalbantoglu J Couture R Antel JP 《Journal of neuropathology and experimental neurology》2000,59(10):896-906
The kinin B1 receptor is an inducible receptor expressed in response to inflammatory mediators. We sought to determine whether kinin B1 receptor can be expressed on human brain endothelial cells (HBECs) in vitro and whether signaling via this receptor can regulate permeability and chemokine production properties of these cells. Multiplex RT-PCR amplification and western blot techniques were used to evaluate B1 receptor expression by HBECs. Although B1 receptor mRNA and protein could not be detected on resting HBECs, interferon-gamma induced a dose- and time-dependent up-regulation of B1 receptor mRNA and protein on HBECs. Stimulation of interferon-gamma-treated HBECs with the selective B1 agonist R-838 (Sar [D-Phe8] des Arg9-BK) induced a dose- and time-dependent increase in the production of inositol 3,4,5 tri-phosphate and nitric oxide. Permeability of the HBECs monolayer, as measured by BSA diffusion, was significantly increased by application of the B1 agonist. This biological effect of R-838 could be prevented by R-715, a B1 receptor antagonist and by L-NAME, a nitric oxide synthase blocker. R-838 also inhibited interleukin-8 release from HBECs. We demonstrate that B1 receptors can be up regulated on the surface of HBECs by molecules released during inflammatory response and that signaling via this receptor can regulate BBB permeability and chemokine production in vitro. 相似文献
38.
PC NG KW SO TF FOK MC YAM MY WONG W WONG 《Journal of paediatrics and child health》1997,33(4):324-328
Objectives: A prospective study comparing the efficiacy and side-effects of oral sulindac with intravenous indomethacin in clinically stable preterm infants (<1750 g) requiring non-invasive closure of haemodynamically significant patent ductus arteriosus.
Methodology: As maturity and birthweight are the two major determinants of ductal closure, infants were matched as closely as possible for these parameters. An eligible patient was first assigned to the sulindac group and a subsequent patient with similar gestational age (± 1 week) and birthweight (±100 g) to the previously recruited infant would automatically receive indomethacin. A total of eight infants were enrolled in each group.
Results: The ductus arteriosus was successfully closed in all eight infants receiving indomethacin, and in seven of eight infants receiving sulindac. No significant differences were found with regards to the ductal size between the two groups at diagnosis or on each of the consecutive days of treatment ( P >0.25). More renal adverse effects were encountered in the indomethacin group. Significant differences in changes from baseline value for urine output, plasma sodium, urea and creatinine concentrations were noted at 24, 48 and 72 h after commencement of treatment between the two groups ( P <0.05). All the parameters returned to normal or pre-treatment levels 48 h after stopping therapy. Unexpectedly, severe gastrointestinal complications were encountered in the sulindac group.
Conclusions: Sulindac is capable of promoting ductal constriction in clinically stable preterm infants without compromising the renal function. The spectrum of gastrointestinal complications observed in sulindac treated infants were similar to those described for indomethacin. The use of sulindac for ductal closure in the preterm infant should remain experimental. 相似文献
Methodology: As maturity and birthweight are the two major determinants of ductal closure, infants were matched as closely as possible for these parameters. An eligible patient was first assigned to the sulindac group and a subsequent patient with similar gestational age (± 1 week) and birthweight (±100 g) to the previously recruited infant would automatically receive indomethacin. A total of eight infants were enrolled in each group.
Results: The ductus arteriosus was successfully closed in all eight infants receiving indomethacin, and in seven of eight infants receiving sulindac. No significant differences were found with regards to the ductal size between the two groups at diagnosis or on each of the consecutive days of treatment ( P >0.25). More renal adverse effects were encountered in the indomethacin group. Significant differences in changes from baseline value for urine output, plasma sodium, urea and creatinine concentrations were noted at 24, 48 and 72 h after commencement of treatment between the two groups ( P <0.05). All the parameters returned to normal or pre-treatment levels 48 h after stopping therapy. Unexpectedly, severe gastrointestinal complications were encountered in the sulindac group.
Conclusions: Sulindac is capable of promoting ductal constriction in clinically stable preterm infants without compromising the renal function. The spectrum of gastrointestinal complications observed in sulindac treated infants were similar to those described for indomethacin. The use of sulindac for ductal closure in the preterm infant should remain experimental. 相似文献
39.
Background. Colour Doppler sonography (CDS) has become the procedure of choice in evaluating testicular perfusion but false negative
findings have been reported. Objective. To determine if direct visualisation of the twisted spermatic cord using high resolution US is a reliable sign to assess
testicular torsion. Material and methods. Thirty patients (aged 2–26 years) with equivocal diagnosis of testicular torsion prospectively underwent high resolution
and CDS. The results were correlated with surgical findings. Serial transverse and longitudinal scans were performed to compare
the scrotal contents on each side and study the complete spermatic cord course, from inguinal canal to testis, to detect a
spiral twist. Results. In 14 of the 23 cases of torsion, the diagnosis was based on the colour Doppler findings in the scrotum because blood flow
was absent in the symptomatic testis and detectable without difficulty on the normal side. In nine cases, CDS was unreliable;
in six cases intratesticular perfusion was present in a twisted testis and in three small boys, no colour signal was obtained
in either testis. In all cases of torsion, the spiral twist of spermatic cord was detected at the external inguinal ring.
The twist induced an abrupt change in spermatic cord course, size and shape below the point of torsion. It appeared in the
scrotum as a round or oval, homogeneous or heterogeneous extratesticular mass with or without blood flow, that could be connected
cephalad with the normal inguinal cord. In the other seven cases (three late torsions of the appendix testis, one epididymo-orchitis
and three torsions with spontaneous reduction), no spiral twist was detectable. Conclusion. The detection of spermatic cord spiral twist appears a reliable US sign of torsion whatever the testicular consequences.
Received: 1 December 1997 Accepted: 17 June 1998 相似文献
40.
Aberrant crypt focus promotion and glucose intolerance: correlation in the rat across diets differing in fat, n-3 fatty acids and energy 总被引:1,自引:0,他引:1
Koohestani N; Chia MC; Pham NA; Tran TT; Minkin S; Wolever TM; Bruce WR 《Carcinogenesis》1998,19(9):1679-1684
McKeown-Eyssen (Cancer Epidemiol. Biomarkers Prevent., 3, 687-695, 1994)
and Giovannucci (Cancer Causes Control, 6, 164-179, 1995), noting the
striking similarity in lifestyle risk factors for colorectal cancer and
insulin resistance, proposed that the hyperinsulinemia, glycemia and
hypertriglyceridemia associated with insulin resistance promotes colon
cancer. To compare the effect of diet on colon cancer promotion and insulin
resistance in the F344 rat, we assessed the effect of fat, n-3 fatty acids
and energy in pairwise comparisons on average size of aberrant crypt foci
(ACF) and on glucose intolerance in the same animals in a single
experiment. Diets high in fat and energy increased and diets with increased
n-3 fatty acids and calorie restriction decreased both ACF growth and
glucose intolerance compared with control diets. The measures of promotion
of colon cancer and insulin resistance were strongly correlated (n = 98, r
= 0.67, P < 0.001). In addition, both were highly correlated with daily
energy intake (r = 0.62 and 0.66) and were also correlated with basal
(post-prandial) insulin, glucose and triglycerides (r = 0.31-0.53, P <
0.01). We concluded that ACF growth and glucose intolerance are correlated
for a wide range of diets and that increased circulating energy (glucose
and triglycerides) may lead to both colon cancer promotion and insulin
resistance.
相似文献