全文获取类型
收费全文 | 15370篇 |
免费 | 1004篇 |
国内免费 | 85篇 |
专业分类
耳鼻咽喉 | 160篇 |
儿科学 | 460篇 |
妇产科学 | 197篇 |
基础医学 | 2028篇 |
口腔科学 | 360篇 |
临床医学 | 1782篇 |
内科学 | 3456篇 |
皮肤病学 | 340篇 |
神经病学 | 1301篇 |
特种医学 | 897篇 |
外科学 | 2239篇 |
综合类 | 176篇 |
一般理论 | 5篇 |
预防医学 | 1011篇 |
眼科学 | 359篇 |
药学 | 892篇 |
中国医学 | 16篇 |
肿瘤学 | 780篇 |
出版年
2023年 | 89篇 |
2022年 | 173篇 |
2021年 | 371篇 |
2020年 | 206篇 |
2019年 | 327篇 |
2018年 | 406篇 |
2017年 | 266篇 |
2016年 | 342篇 |
2015年 | 423篇 |
2014年 | 494篇 |
2013年 | 663篇 |
2012年 | 1021篇 |
2011年 | 981篇 |
2010年 | 615篇 |
2009年 | 500篇 |
2008年 | 877篇 |
2007年 | 879篇 |
2006年 | 843篇 |
2005年 | 759篇 |
2004年 | 608篇 |
2003年 | 598篇 |
2002年 | 485篇 |
2001年 | 208篇 |
2000年 | 180篇 |
1999年 | 234篇 |
1998年 | 195篇 |
1997年 | 205篇 |
1996年 | 183篇 |
1995年 | 139篇 |
1994年 | 139篇 |
1993年 | 125篇 |
1992年 | 136篇 |
1991年 | 142篇 |
1990年 | 135篇 |
1989年 | 170篇 |
1988年 | 147篇 |
1987年 | 136篇 |
1986年 | 130篇 |
1985年 | 138篇 |
1984年 | 141篇 |
1983年 | 82篇 |
1982年 | 90篇 |
1981年 | 84篇 |
1980年 | 109篇 |
1979年 | 98篇 |
1978年 | 79篇 |
1977年 | 72篇 |
1976年 | 78篇 |
1975年 | 75篇 |
1960年 | 69篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
X-linked mixed deafness (DFN3): cloning and characterization of the critical region allows the identification of novel microdeletions 总被引:5,自引:0,他引:5
Huber Irene; Bitner-Gllndzicz Maria; de Kok Yvette J.M.; van der Maarel Silvere M.; Ishikawa-Brush Yumiko; Monaco Anthony P.; Robinson David; Malcolm Susan; Pembrey Marcus E.; Brunner Han G.; Cremers Frans P.M.; Ropers Hans-Hilger 《Human molecular genetics》1994,3(7):1151-1154
We have found that the microsatellite marker AFM207zg5 (DXS995)maps to all previously described deletions which are associatedwith X-linked mixed deafness (DFN3) with or without choroideremiaand mental retardation. Employing this marker and pHU16 (DXS26)we have identified two partially overlapping yeast artificialchromosome clones which were used to construct a complete 850kb cosmid contig. Cosmids from this contig have been testedby Southern blot analysis on DNA from 16 unrelated males withX-linked deafness. Two novel microdeletions were detected inpatients which exhibit the characteristic DFN3 phenotype. Bothdeletions are completely contained within one of the known DFN3-deletions,but one of them does not overlap with two previously describeddeletions in patients with contiguous gene syndromes consistingof DFN3, chorolderemia, and mental retardation. Assuming thatonly a single gene is involved, this suggests that the DFN3gene spans a chromosomal region of at least 400 kb. 相似文献
82.
The heart in hypertension. 总被引:10,自引:0,他引:10
83.
Marie-Laure Muiras Marcus Müller François Schächter A. Bürkle 《Journal of molecular medicine (Berlin, Germany)》1998,76(5):346-354
Poly(ADP-ribosyl)ation is a posttranslational modification of nuclear proteins which is catalyzed by poly(ADP-ribose) polymerase
and represents an immediate response of eukaryotic cells to oxidative and other types of DNA damage. Previously a strong correlation
had been detected between maximal poly(ADP-ribose) polymerase activity in permeabilized mononuclear leukocytes of various
mammalian species and species-specific life span. To study a possible relation between longevity and poly(ADP-ribosyl)ation
in humans we measured maximal oligonucleotide-stimulated poly(ADP-ribose) polymerase activity in permeabilized, Epstein-Barr
virus transformed lymphoblastoid cell lines from a French population of 49 centenarians and 51 controls aged 20–70 years.
Maximal enzyme activity was significantly higher in centenarians than in controls [median of controls: 9035 cpm/106 cells (lower quartile: 6156; upper quartile: 11,410); median of centenarians: 10,380 cpm/106 cells (lower quartile: 7994; upper quartile: 12,991); P=0.031 by Mann-Whitney U test]. In a subset of 16 controls and 24 centenarians, cellular poly(ADP-ribose) polymerase content was determined by quantitative
western blotting, thus allowing the calculation of specific enzyme activity. The latter was significantly higher in centenarians
(P=0.006), the median value for centenarians being about 1.6-fold that of controls. Specific poly(ADP-ribose) polymerase activity
was a more powerful parameter for differentiating between centenarians and controls than enzyme activity relative to cell
number. In addition, in a genetic association study we analyzed 437 DNA samples (239 centenarians and 198 controls) by PCR
amplification of a polymorphic dinucleotide repeat located in the promoter region of the poly(ADP-ribose) polymerase gene
in an attempt to detect an association between this polymorphic marker and variability of enzyme activity or human longevity.
However, this genetic analysis revealed no significant enrichment of any of the alleles or genotypes identified among centenarians
or controls, but its power was limited by the relatively weak hetero-zygosity of this polymorphic marker in our population
(51%). Viewed together with previous results on poly(ADP-ribose) polymerase activity in various mammalian species, the present
data provide further evidence for the notion that longevity is associated with a high poly(ADP-ribosyl)ation capacity.
Received: 5 September 1997 / Accepted: 10 November 1997 相似文献
84.
Synergistic interaction of topographic features in the production of bone-like nodules on Ti surfaces by rat osteoblasts 总被引:4,自引:0,他引:4
The objective of this study was to study the responses of osteoblast-like cells to rough Titanium (Ti)-coated epoxy surfaces of differing topographic complexity. Four topographies were studied: polished (PO), coarse-blasted (CB), acid-etched (AE) and coarse-blasted+acid-etched (SLA). Rat osteoblasts were cultured on these surfaces and their morphology, thickness as well as the number and size of bone-like nodules measured. To determine cell shape and cell thickness, fluorescein-5-thiosemicarbazide was used to stain the cell components including the cell membrane, the stained cells were optically sectioned using epifluorescent microscopy and the optical sections were computationally reconstructed to obtain three-dimensional images in which cell volume and cell thickness could be determined. Similarly optical sections of bone-like nodules labeled with tetracycline were also reconstructed to determine their size. The different surface topographies were found to alter the thickness and morphology of osteoblasts cultured on these surfaces. Osteoblasts produced significantly more and larger nodules on SLA compared to other surfaces. Nevertheless and perhaps surprisingly, given the evidence in various cell populations that cell shape can affect cell differentiation, cell thickness was not directly correlated with an increase in bone-like nodule formation. Data were analyzed by factorial analysis of variance. In this way the primary effect of each surface treatment ( i.e. blasting and acid etching) could be assessed as well as their interaction. Both the acid etching and blasting processes significantly affected the number and size of bone-like nodules cultured on Ti surfaces. Moreover there were significant interaction effects indicating that surface topographic features can act synergistically to enhance bone formation. This result suggests that a useful approach to the optimization of surfaces for bone production could involve systematic investigation of combinations of processes each of which produces distinct surface topographical features. 相似文献
85.
86.
Life expectancy in British Marfan syndrome populations 总被引:2,自引:0,他引:2
JR Gray AB Bridges RR West L. McLeish AG Stuart JCS Dean MEM Porteous M. Boxer SJ Davies 《Clinical genetics》1998,54(2):124-128
A total of 206 patients with Marfan syndrome were ascertained throughout genetic clinics in Wales and Scotland during the period 1970–1990. There were 45 deaths representing 22% of the cohort. Mean age at death was 45.3 ± 16.5 years. 50% median cumulative survival in the total cohort (n = 206) was 53 years for males and 72 years for females. Multivariate analysis confirmed severity as the best independent indicator of survival. These findings and survival curves will assist in the counselling of British families and individuals with Marfan syndrome. 相似文献
87.
The GAP-related domain of tuberin, the product of the TSC2 gene, is a target for missense mutations in tuberous sclerosis 总被引:5,自引:0,他引:5
Maheshwar MM; Cheadle JP; Jones AC; Myring J; Fryer AE; Harris PC; Sampson JR 《Human molecular genetics》1997,6(11):1991-1996
Tuberous sclerosis is an autosomal dominant trait in which the
dysregulation of cellular proliferation and differentiation results in the
development of hamartomatous growths in many organs. The TSC2 gene is one
of two genes determining tuberous sclerosis. Inactivating germline
mutations of TSC2 in patients with tuberous sclerosis and somatic loss of
heterozygosity at the TSC2 locus in the associated hamartomas indicate that
TSC2 functions as a tumour suppressor gene and that loss of function is
critical to expression of the tuberous sclerosis phenotype. The TSC2
product, tuberin, has a region of homology with the GTPase activating
protein rap1GAP and stimulates the GTPase activity of rap1a and rab5a in
vitro. Here we show that the region of homology between tuberin and human
rap1GAP and the murine GAP mSpa1 is more extensive than previously reported
and spans approximately 160 amino acid residues encoded within exons 34-38
of the TSC2 gene. Single strand conformation polymorphism analysis of these
exons in 173 unrelated patients with tuberous sclerosis and direct
sequencing of variant conformers together with study of additional family
members enabled characterisation of disease associated mutations in 14
cases. Missense mutations, which occurred in exons 36, 37 and 38 were
identified in eight cases, four of whom shared the same recurrent change
P1675L. Each of the five different missense mutations identified was shown
to occur de novo in at least one sporadic case of tuberous sclerosis. The
high proportion of missense mutations detected in the region of the TSC2
gene encoding the GAP-related domain supports its key role in the
regulation of cellular growth.
相似文献
88.
89.
Permeation of human ovarian tissue with cryoprotective agents in preparation for cryopreservation 总被引:18,自引:10,他引:18
Newton H; Fisher J; Arnold JR; Pegg DE; Faddy MJ; Gosden RG 《Human reproduction (Oxford, England)》1998,13(2):376-380
The recent improvements in the treatment of cancer by chemo- and
radiotherapy have led to a significant increase in the survival rates of
patients with malignant disease, but at the expense of distressing side
effects. One major problem, especially for younger patients, is that
aggressive therapy destroys a significant proportion of the follicular
population, which can result in either temporary or permanent infertility.
Freeze-banking pieces of ovarian cortex prior to treatment is one strategy
for preserving fecundity. When the patient is in remission, fertility
could, theoretically, be restored by autografting the thawed tissue at the
orthotopic site or by growing isolated follicles to maturity in vitro.
Recent studies have found good follicular survival in frozen-thawed human
ovarian tissue but to optimize the process an effective cryopreservation
method needs to be developed. An essential part of such a technique is to
permeate the tissue with a cryoprotectant to minimize ice formation and the
extent of this equilibration is an important determinant of post-thaw
cellular survival. In the current study, we have investigated the diffusion
of four cryoprotective agents into human tissue at both 4 degrees C and 37
degrees C. We have also studied the effect of adding different
concentrations of the non penetrating cryoprotective agent, sucrose, to the
freezing media using the release of lactate dehydrogenase as a measure of
its protective effect. At 4 degrees C propylene glycol and glycerol
penetrated the tissue significantly slower than either ethylene glycol or
dimethyl sulphoxide. At the higher temperature of 37 degrees C all four
cryoprotectants penetrated at a faster rate, however concern about enhanced
toxicity prevents the use of these conditions in practice. Thus, the
results suggest that the best method of preparing tissue for freezing is
exposure for 30 min to 1.5 M solutions of ethylene glycol or dimethyl
sulphoxide at 4 degrees C; this achieved a mean tissue concentration that
was almost 80% that of the bathing solution. We also report that the
addition of low concentrations of sucrose to the freezing medium does not
have a significant protective effect against freezing injury.
相似文献
90.
We have developed a sandwich-type ELISA system for measuring total IgD levels in the serum of atopics and non-atopic controls. In this ELISA system, affinity purified goat anti-human IgD was used for capture. Results were superior to those obtained with monoclonal anti-human IgD antibody. No cross-reactivity could be demonstrated to IgG, IgM, IgA or IgE. The assay showed minimal non-specific binding even with initial serum dilutions of 1:2. The results obtained were reproducible among replicates (Mean CV +/- SEM = 0.03 +/- 0.002; n = 251), between dilutions (CV = 0.08 +/- 0.006; n = 108), and between assays (CV = 0.05 +/- 0.12; n = 5). We used routine radioimmunoassay for measuring total serum IgE. Using these assays total serum IgD and IgE levels were measured in 75 atopic patients and 33 normal subjects. None of the atopics had recent immunotherapy. As expected, the geometric mean serum IgE in atopics (373 ng/ml) was significantly higher than that in normal subjects (49 ng/ml) (P less than 0.01). However, geometric mean serum IgD was also significantly higher in atopics (20.3 micrograms/ml) than that in normal subjects (8.4 micrograms/ml) (P less than 0.02). In both atopic and normal groups, mean serum IgD level did not differ significantly on the bases of age, sex or asthmatic status. Furthermore, total serum IgD was not significantly correlated with total serum IgE (r = 0.14; P = 0.14; n = 108), indicating that immunoregulatory control of the basal levels of the two isotypes is not linked.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献