全文获取类型
收费全文 | 2528篇 |
免费 | 131篇 |
国内免费 | 83篇 |
专业分类
耳鼻咽喉 | 16篇 |
儿科学 | 87篇 |
妇产科学 | 44篇 |
基础医学 | 249篇 |
口腔科学 | 35篇 |
临床医学 | 331篇 |
内科学 | 599篇 |
皮肤病学 | 38篇 |
神经病学 | 202篇 |
特种医学 | 292篇 |
外科学 | 301篇 |
综合类 | 88篇 |
一般理论 | 2篇 |
预防医学 | 181篇 |
眼科学 | 34篇 |
药学 | 132篇 |
中国医学 | 5篇 |
肿瘤学 | 106篇 |
出版年
2021年 | 34篇 |
2020年 | 19篇 |
2019年 | 35篇 |
2018年 | 41篇 |
2017年 | 26篇 |
2016年 | 27篇 |
2015年 | 43篇 |
2014年 | 57篇 |
2013年 | 66篇 |
2012年 | 101篇 |
2011年 | 93篇 |
2010年 | 97篇 |
2009年 | 89篇 |
2008年 | 86篇 |
2007年 | 121篇 |
2006年 | 84篇 |
2005年 | 91篇 |
2004年 | 76篇 |
2003年 | 80篇 |
2002年 | 84篇 |
2001年 | 80篇 |
2000年 | 73篇 |
1999年 | 58篇 |
1998年 | 109篇 |
1997年 | 78篇 |
1996年 | 71篇 |
1995年 | 69篇 |
1994年 | 55篇 |
1993年 | 54篇 |
1992年 | 55篇 |
1991年 | 49篇 |
1990年 | 56篇 |
1989年 | 57篇 |
1988年 | 55篇 |
1987年 | 46篇 |
1986年 | 49篇 |
1985年 | 50篇 |
1984年 | 36篇 |
1983年 | 24篇 |
1982年 | 26篇 |
1981年 | 15篇 |
1980年 | 17篇 |
1979年 | 18篇 |
1978年 | 15篇 |
1977年 | 26篇 |
1976年 | 26篇 |
1975年 | 26篇 |
1972年 | 11篇 |
1971年 | 9篇 |
1970年 | 9篇 |
排序方式: 共有2742条查询结果,搜索用时 15 毫秒
21.
22.
23.
Verschuren MC; Blom B; Bogers AJ; Spits H; van Dongen JJ 《International immunology》1998,10(12):1873-1880
Recombination of deltaRec to psiJalpha will delete the TCR delta gene,
which is thought to play an important role in the bifurcation of the TCR
alphabeta versus TCR gammadelta differentiation lineages. We recently
detected a DNA-binding protein in human thymocytes, the so- called PJA-BP,
which recognizes the psiJalpha gene segment and might be one of the factors
involved in the regulation of preferential deltaRec- psiJalpha
rearrangements. We now investigate PJA-BP expression and its correlation
with TCR delta gene deletion in thymocytes. Our electrophoretic mobility
shift assay experiments showed that the PJA-BP is evolutionary conserved in
human, murine and simian thymocytes. Using a large series of human
hematopoietic malignancies (n = 30), we conclude that PJA-BP expression is
thymocyte specific and seems to be restricted to thymocytes committed to
the TCR alphabeta lineage. Analysis of seven well-defined human thymocyte
subpopulations showed that preferential deltaRec-psiJalpha rearrangements
as well as PJA-BP expression can be detected from the immature
CD34-/CD1+/CD3- /CD4+/CD8alpha+beta- thymocyte differentiation stage
onwards. These experiments indicate that expression of PJA-BP in human
thymocytes starts simultaneously with preferential deltaRec-psiJalpha
rearrangements, which supports our hypothesis that PJA-BP is one of the
factors involved in the preferential recombination of deltaRec to
psiJalpha.
相似文献
24.
Del-Favero J; Krols L; Michalik A; Theuns J; Lofgren A; Goossens D; Wehnert A; Van den Bossche D; Van Zand K; Backhovens H; van Regenmorter N; Martin JJ; Van Broeckhoven C 《Human molecular genetics》1998,7(2):177-186
Autosomal dominant cerebellar ataxia with retinal degeneration (ADCAII) was
previously mapped by linkage analysis studies to chromosome 3p12- p21.1
(SCA7). Positional cloning efforts have recently identified a novel gene,
SCA7 , containing a translated CAG repeat, expanded in SCA7 patients. We
cloned the SCA7 gene from a yeast artificial chromosome (YAC) clone contig
spanning the SCA7 candidate region. Using a combination of genomic
sequencing and cosmid-based exon trapping, two expressed sequence tags were
identified. Sequencing of the corresponding cDNA clones and RT-PCR analysis
identified the full- length SCA7 cDNA. Together, our sequence data defined
the intron/exon boundaries of the first two coding exons of the SCA7 gene,
with the first exon containing the expanded CAG repeat. Further, sequence
comparison with the published SCA7 cDNA identified one additional putative
exon in the 5'-UTR region of the SCA7 gene. The SCA7 gene was mapped on the
YAC contig in the 2.5 cM interval between D3S1600 and D3S1287. In one
extended Belgian SCA7 pedigree the expanded alleles ranged from 38 to at
least 55 repeats with allele lengths being inversely correlated with onset
age of ADCAII symptoms. The SCA7 repeats increased in length in successive
generations. Normal alleles had from four to 18 repeats, with 10 repeats
being the most common allele.
相似文献
25.
Intracellular ion activities and Cl-transport mechanisms in bullfrog corneal epithelium 总被引:8,自引:0,他引:8
Cell membrane potentials, cell membrane resistances, and intracellular ionic activities were measured in bullfrog corneal epithelium. Equivalent circuit analysis was performed by adding adenosine to the apical surface and assuming that only the apical membrane is initially affected. From single-ion substitutions in the apical bathing solution, the apical membrane was found to have a high Cl- permeability, a low K+ permeability, and an unmeasurably small Na+ permeability. Under control conditions intracellular Cl- activity (aCli) was 22 +/- 2 (SE) mM, intracellular Na+ activity (aNai) was 14 +/- 3 mM, and intracellular K+ activity (aKi) was 106 +/- 5 mM. The electrical potential differences across apical and basolateral membranes were about 50 and 67 mV, respectively, both cell negative. aCli and aKi are higher, whereas aNai is much lower than predicted for equilibrium distribution. Inasmuch as Cl- is transported from the basolateral (stromal) to the apical (tear) side, basolateral entry of this anion is uphill and apical exit is downhill. Basolateral entry is Na+ dependent, as evidenced by a fall of aCli to near-equilibrium values after basolateral Na+ removal. The electrochemical gradient for Cl- efflux across the apical membrane is large enough to account for Cl- transport by electrodiffusion only. Na+ removal from the basolateral solution causes a reversible decrease of apical membrane Cl- permeability. The results support the hypothesis that net transepithelial Cl- transport results from coupled NaCl entry (or an equivalent process) at the basolateral membrane and electrodiffusional Cl- exit at the apical membrane. 相似文献
26.
Mast cell tryptase and proteinase-activated receptor 2 induce hyperexcitability of guinea-pig submucosal neurons 总被引:5,自引:2,他引:5
David E. Reed Carlos Barajas-Lopez Graeme Cottrell Sara Velazquez-Rocha Olivier Dery Eileen F. Grady Nigel W. Bunnett Stephen J. Vanner 《The Journal of physiology》2003,547(2):531-542
Mast cells that are in close proximity to autonomic and enteric nerves release several mediators that cause neuronal hyperexcitability. This study examined whether mast cell tryptase evokes acute and long-term hyperexcitability in submucosal neurons from the guinea-pig ileum by activating proteinase-activated receptor 2 (PAR2) on these neurons. We detected the expression of PAR2 in the submucosal plexus using RT-PCR. Most submucosal neurons displayed PAR2 immunoreactivity, including those colocalizing VIP. Brief (minutes) application of selective PAR2 agonists, including trypsin, the activating peptide SL-NH2 and mast cell tryptase, evoked depolarizations of the submucosal neurons, as measured with intracellular recording techniques. The membrane potential returned to resting values following washout of agonists, but most neurons were hyperexcitable for the duration of recordings (> 30 min–hours) and exhibited an increased input resistance and amplitude of fast EPSPs. Trypsin, in the presence of soybean trypsin inhibitor, and the reverse sequence of the activating peptide (LR-NH2 ) had no effect on neuronal membrane potential or long-term excitability. Degranulation of mast cells in the presence of antagonists of established excitatory mast cell mediators (histamine, 5-HT, prostaglandins) also caused depolarization, and following washout of antigen, long-term excitation was observed. Mast cell degranulation resulted in the release of proteases, which desensitized neurons to other agonists of PAR2. Our results suggest that proteases from degranulated mast cells cleave PAR2 on submucosal neurons to cause acute and long-term hyperexcitability. This signalling pathway between immune cells and neurons is a previously unrecognized mechanism that could contribute to chronic alterations in visceral function. 相似文献
27.
JJ Favre Ph Chaffanjon JG Passagia JP Chirossel 《Surgical and radiologic anatomy : SRA》1995,17(2):133-138
Summary The authors report the results of a series of dissections and anatomic sections of the fronto-basal region of the brain and of the anterior cranial fossa in human cadavers. The constant presence of an arachnoidal cistern above the olfactory nerve was verified. The arachnoid separates from the pial membrane and forms a bridge with the ventral part of the olfactory bulb and tract, from the lateral edge of the olfactory sulcus to the medial edge of the gyrus rectus. The cistern is wide in its anterior portion, between the gyrus rectus and the olfactory bulb, and is reduced to a virtual slit in its posterior portion where the tract is lodged in the olfactory sulcus. The olfactory nerve can be separated without damaging fronto-basal arachnoidial adhesions over several centimeters. Dissection of this region after intravascular injection of colored media shows the constant presence of an artery destined to the olfactory bulb and tract. It originates either from the lateral surface of the anterior cerebral a. (segment A2), or from the medial fronto-basal a., and consistently provides terminal branches in front of the olfactory trigone in the medial olfactory sulcus. At their ventral extremity, the olfactory structures are therefore vascularised independently for several centimeters, from the lower face of the frontal lobe. The independent vascularisation of the olfactory nerve, the tenuous and easily detachable adhesions, and the actual presence of a true arachnoidal cistern all contribute to enabling surgical techniques which conserve olfactory function during anterior approaches.
Vascularisation du nerf olfactif. Rapports méningés et applications chirurgicales
Résumé Les auteurs rapportent les résultats d'une série de dissections et de coupes de la région fronto-basale de l'encéphale et de la fosse crânienne antérieure sur sujets cadavériques. La présence constante d'une citerne arachnoïdienne au dessus du n. olfactif a été vérifiée. L'arachnoïde se sépare du feuillet pial et passe en pont à la partie ventrale du bulbe et du tractus olfactifs, du bord latéral du sillon olfactif au bord médial du gyrus rectus. La citerne est large dans sa portion antérieure, entre le gyrus rectus et le bulbe olfactif, se réduit à une fente virtuelle postérieure lorsque le tractus se loge dans le sillon olfactif. Le n. olfactif peut être séparé sans dommage des adhérences arachnoïdiennes fronto-basales sur quelques centimètres. La dissection de cette région, après injection intravasculaire de masses colorées montre, de façon originale, la présence constante d'une artère destinée au tractus et au bulbe olfactifs. Elle naît soit de la face latérale de l'a. cérébrale antérieure (segment A2), soit de l'a. fronto-basale médiale, pour donner ses branches terminales toujours en avant du trigone olfactif dans le sillon orbitaire médial. Sur quelques centimètres à leur extrémité ventrale, les structures olfactives ont donc une vascularisation indépendante de la face inférieure du lobe frontal. L'indépendance vasculaire du n. olfactif, des adhérences ténues, facilement détachables, et la réalité vérifiée d'une véritable citerne arachnoïdienne permettent d'imaginer des techniques conservatrices de la fonction olfactive utilisées dans plusieurs indications de la chirurgie de la fosse crânienne antérieure.相似文献
28.
The infrapyloric artery and cephalic pancreatoduodenectomy with pylorus preservation: preliminary study 总被引:1,自引:0,他引:1
Ph Wind JM Chevallier JJ Sarcy V Delmas PH Cugnenc 《Surgical and radiologic anatomy : SRA》1994,16(2):165-172
Summary Cephalic pancreatoduodenectomy (CPD) with pylorus preservation has been suggested to improve the functional and nutritional result of surgery. At operation, the first two centimeters of the duodenum are preserved, the vascular arch of the lesser gastric curvature is saved and the right gastroepiploic artery is resected at its origin. The aim of this study on 15 fresh cadavers was to determine the origin of the vascularization of the remaining duodenum and also the possibilities of preserving an optimal vascularization after CPD and pylorus preservation. All of the arteries supplying the remaining duodenum and arising either from the right gastric artery or the right gastroepiploic artery were identified. The distances between the origin of the infrapyloric artery and the termination of the gastroduodenal artery on the cranial and ventral pancreaticoduodenal artery and the left gastroepiploic artery were measured. At CPD with pylorus preservation, the study demonstrated that: 1) the cranial side of the remaining duodenum remains vascularized in 80% of the cases by one or two supraduodenal branches coming from the right gastric artery; 2) ligation of the right gastroepiploic artery eliminates all vascular supply to the caudal side of the remaining duodenum in almost half of the cases; 3) in these cases, the dissection of the bifurcation of the gastroduodenal artery and the vascular section beyond the origin of the infrapyloric artery allowed a direct vascular supply to the remaining duodenum to be preserved.This work was presented at the French Section of the European Association of Clinical Anatomy meeting, Bobigny, France, 1992 相似文献
29.
Dithiothreitol prevents age-associated decrease in oocyte/conceptus viability in vitro 总被引:2,自引:0,他引:2
The present study was designed to ascertain whether the negative effects on
reproductive potential of post-ovulatory ageing in vitro of oocytes can be
prevented by antioxidant therapy. Mouse metaphase II (MII) oocytes were
aged in vitro for 12 h prior to insemination in the presence of varying
concentrations of L-ascorbic acid, 6-methoxy-
2,5,7,8-tetramethylchromane-2-carboxylic acid (Trolox), L-cystine
dihydrochloride, ethylenediaminetetraacetic acid (EDTA), beta-
mercaptoethanol and DL-dithiothreitol (DTT). In-vitro ageing of oocytes was
associated with lower fertilization rate, higher proportion of concepti
exhibiting cellular fragmentation at 24 h post-insemination and lower
percentage of concepti reaching the blastocyst stage. Ascorbic acid, Trolox
and EDTA had no effect on cellular fragmentation or potential of oocytes
for development. However, the probability of an oocyte reaching the
blastocyst stage was decreased (P < or = or = 0.05) in oocytes incubated
in the presence of L-cystine (50 and 500 microM) and beta-mercaptoethanol
(5, 50 and 500 microM) when compared to control aged oocytes.
Age-associated cellular fragmentation at 24 h post-insemination was
partially prevented (P < or = 0.05) by incubating oocytes in the
presence of beta-mercaptoethanol (500 microM). DTT (50 and 500 microM)
increased (P < or = 0.05) fertilization rate and number of cells at 81 h
post-insemination to levels similar to those exhibited by control oocytes.
Furthermore, both age-associated fragmentation at 24 h post-insemination (P
< or = 0.05) and decreased potential of oocytes for development to the
blastocyst stage (P < or = 0.05) were prevented, at least in part, by
culturing oocytes in the presence of DTT (50 microM). Although the
mechanism by which DTT exerts its beneficial effects on aged oocytes
remains to be elucidated, it may protect oocytes by preventing oxidation of
free thiol groups and/or altering a redox-independent signalling pathway
that mediates cellular fragmentation and death.
相似文献
30.
Vankeerberghen A; Wei L; Jaspers M; Cassiman JJ; Nilius B; Cuppens H 《Human molecular genetics》1998,7(11):1761-1769
In order to gain a better insight into the structure and function of the
regulatory domain (RD) of the cystic fibrosis transmembrane conductance
regulator (CFTR) protein, 19 RD missense mutations that had been identified
in patients were functionally characterized. Nine of these (I601F, L610S,
A613T, D614G, I618T, L619S, H620P, G628R and L633P) resulted in aberrant
processing. No or a very small number of functional CFTR proteins will
therefore appear at the cell membrane in cells expressing these mutants.
These mutations were clustered in the N- terminal part of the RD,
suggesting that this subdomain has a folding pattern that is very sensitive
to amino acid changes. Mutations that caused no aberrant processing were
further characterized at the electrophysiological level. First, they were
studied at the whole cell level in Xenopus laevis oocytes. Mutants that
induced a whole cell current that was significantly different from
wild-type CFTR were subsequently analysed at the single channel level in
COS1 cells transiently expressing the different mutant and wild-type
proteins. Three mutant chloride channels, G622D, R792G and E822K CFTR, were
characterized by significantly lower intrinsic chloride channel activities
compared with wild-type CFTR. Two mutations, H620Q and A800G, resulted in
increased intrinsic chloride transport activities. Finally, T665S and E826K
CFTR had single channel properties not significantly different from
wild-type CFTR.
相似文献