全文获取类型
收费全文 | 7729篇 |
免费 | 404篇 |
国内免费 | 43篇 |
专业分类
耳鼻咽喉 | 92篇 |
儿科学 | 286篇 |
妇产科学 | 216篇 |
基础医学 | 1117篇 |
口腔科学 | 389篇 |
临床医学 | 743篇 |
内科学 | 1480篇 |
皮肤病学 | 250篇 |
神经病学 | 712篇 |
特种医学 | 424篇 |
外科学 | 1102篇 |
综合类 | 68篇 |
一般理论 | 10篇 |
预防医学 | 415篇 |
眼科学 | 38篇 |
药学 | 449篇 |
中国医学 | 8篇 |
肿瘤学 | 377篇 |
出版年
2021年 | 101篇 |
2020年 | 72篇 |
2019年 | 76篇 |
2018年 | 112篇 |
2017年 | 90篇 |
2016年 | 110篇 |
2015年 | 122篇 |
2014年 | 169篇 |
2013年 | 235篇 |
2012年 | 343篇 |
2011年 | 336篇 |
2010年 | 216篇 |
2009年 | 227篇 |
2008年 | 317篇 |
2007年 | 354篇 |
2006年 | 313篇 |
2005年 | 322篇 |
2004年 | 277篇 |
2003年 | 269篇 |
2002年 | 306篇 |
2001年 | 266篇 |
2000年 | 234篇 |
1999年 | 224篇 |
1998年 | 116篇 |
1997年 | 105篇 |
1996年 | 103篇 |
1995年 | 80篇 |
1994年 | 91篇 |
1993年 | 73篇 |
1992年 | 124篇 |
1991年 | 105篇 |
1990年 | 110篇 |
1989年 | 131篇 |
1988年 | 121篇 |
1987年 | 132篇 |
1986年 | 116篇 |
1985年 | 98篇 |
1984年 | 85篇 |
1983年 | 79篇 |
1982年 | 64篇 |
1981年 | 56篇 |
1978年 | 61篇 |
1977年 | 53篇 |
1976年 | 69篇 |
1975年 | 52篇 |
1973年 | 55篇 |
1971年 | 48篇 |
1969年 | 50篇 |
1966年 | 51篇 |
1932年 | 47篇 |
排序方式: 共有8176条查询结果,搜索用时 15 毫秒
71.
Human mini-chromosomes in mouse embryonal stem cells 总被引:3,自引:2,他引:3
We have introduced human mini-chromosomes of 4 Mb and approximately 15 Mb
in size into mouse embryonal stem cells. Although these human mini-
chromosomes are stable in hamster and chicken cells, they re-arrange or
segregate aberrantly in the embryonal stem cells and are rapidly lost in
the absence of selection. However, one of the mini-chromosomes re-
arranged, acquired mouse centromeric sequences and was then stably
maintained for at least 60 population doublings in culture. This mini-
chromosome, which is 4 Mb in size, is a candidate for a mouse germ line
chromosome vector.
相似文献
72.
Determination of the parent of origin in nine cases of prenatally detected chromosome aberrations found after intracytoplasmic sperm injection 总被引:1,自引:17,他引:1
Van Opstal D; Los FJ; Ramlakhan S; Van Hemel JO; Van Den Ouweland AM; Brandenburg H; Pieters MH; Verhoeff A; Vermeer MC; Dhont M; In't Veld PA 《Human reproduction (Oxford, England)》1997,12(4):682-686
Prenatal cytogenetic analysis of 71 fetuses conceived by intracytoplasmic
sperm injection (ICSI) resulted in the detection of nine (12.7%) chromosome
aberrations including two cases of 47,XXY, four cases involving a 45,X cell
line and three autosomal trisomies. Molecular analysis of the parental
origin of the deleted or supernumerary chromosome was performed by using
polymorphic microsatellite markers. Six cases involving a sex chromosome
abnormality were found to be of paternal origin while the two trisomic
cases that could be analysed were of maternal origin. Two cases involved
the same infertile couple who had two consecutive ICSI pregnancies
terminated because of a chromosome abnormality. The replaced embryos in
both cases originated from a single batch of ICSI fertilized oocytes of
which part was used to initiate the first pregnancy and part was
cryopreserved and used to initiate the second pregnancy.
相似文献
73.
Summary The numbers of the carbohydrate side chains have been analyzed on a series of subtype 7 hemagglutinins of influenza A virus. The procedure employed involves growth of the virus in the presence of the trimming inhibitor N-methyl-1-desoxynojirimycin followed by controlled removal of the resulting mannose-rich oligosaccharides with endo-N-acetylglucosaminidase H. By comparative analysis with virus grown in the absence of the inhibitor oligomannosidic side chains can be discriminated from complex ones. The results show that all H7 hemagglutinins have a complex and an oligomannosidic side chain on HA2, whereas the oligosaccharides of HA1 vary in number. 相似文献
74.
R Mings A P Knutsen H Krantman K B Schwarz S T Roodman 《Annals of allergy》1987,58(5):322,372-322,374
75.
Schwarz J. A. Kaboth U. Reikowski H. Jost H. Müting D. Ortmanns H. 《Journal of molecular medicine (Berlin, Germany)》1975,53(11):535-538
Journal of Molecular Medicine - Monomeres IgM, bisher nur bei lymphoproliferativen Autoimmun- und einigen Infektionserkrankungen sowie vereinzelt bei Lebercirrhosen beschrieben, ließ sich... 相似文献
76.
77.
Muscle relaxant action of excitatory amino acid antagonists 总被引:2,自引:0,他引:2
L Turski M Schwarz W A Turski T Klockgether K H Sontag J F Collins 《Neuroscience letters》1985,53(3):321-326
Antagonists of neuronal excitation induced by dicarboxylic amino acids were tested in genetically spastic rats of the Han-Wistar strain. These animals exhibit an increased muscle tone which can be measured as a spontaneous tonic activity in the electromyogram of the gastrocnemius-soleus muscle. Compounds that block excitation due to N-methyl-D-aspartic acid reduced the spontaneous activity measured in the electromyogram in a dose-related manner. The most potent compounds, 2-amino-7-phosphonoheptanoic and kynurenic acids were effective muscle relaxants when given either intraperitoneally or intracerebroventricularly. 2-Amino-5-phosphonopentanoic acid possessed much weaker muscle relaxant activity, while L-glutamic acid diethylester was inactive by either route. The results suggest that blockade of N-methyl-D-aspartic acid receptors results in a myorelaxant effect. Specific antagonists of excitation at N-methyl-D-aspartic acid receptors may provide a new class of muscle relaxants. 相似文献
78.
Characterization of antisera against bovine prolactin for in vivo studies on prolactin function in the rat. 下载免费PDF全文
R Kofler M Tabarelli S Schwarz H Wolf K Loewit G Wick 《Clinical and experimental immunology》1980,41(1):55-62
The IgG fraction of rabbit antisera to bovine prolactin (PRL), intended for in vivo studies on the role of PRL in the rat, was prepared and characterized in vitro and in vivo. The antibodies showed a strong reaction with bovine PRL in double diffusion, immunoelectrophoresis, radioimmunoassay and passive haemagglutination using bovine PRL-coated erythrocytes. In indirect immunofluorescence on paraffin sections of bovine pituitary glands the antibodies could be used for the detection of PRL-producing cells. Cross-reaction with rat PRL was observed in passive haemagglutination with rat PRL-coated erythrocytes and in indirect immunofluorescence on rat pituitary gland, but not in any of the other test systems. The ability of the antibodies to neutralize homologous, i.e. bovine, PRL was tested in lactating rats depleted of endogenous PRL by bromergocriptin treatment. The impaired lactation performance of such animals can be restored by substitution with bovine PRL. If the bovine PRL used for substitution was complexed with anti-bovine PRL-IgG, it lost its biological activity. On the other hand, injections of even high amounts of the antibodies into lactating rats failed to reveal any effect on lactation. It is concluded that either the antibodies do not cross-react with circulating rat PRL in contrast to pituitary PRL (preprolactin?) or that the cross-reacting antibody-populations(s) lack(s) the ability to neutralize the biological function of rat PRL. 相似文献
79.
The proteasome regulator PA28alpha/beta can enhance antigen presentation without affecting 20S proteasome subunit composition 总被引:1,自引:0,他引:1
Schwarz K Eggers M Soza A Koszinowski UH Kloetzel PM Groettrup M 《European journal of immunology》2000,30(12):3672-3679
PA28alpha/beta is a regulatory complex of the 20S proteasome which consists of two IFN-gamma inducible subunits. Both subunits, alpha and beta, contribute equally to the formation of hexa- or heptameric rings which can associate with the 20S proteasome. Previously, we have shown that overexpression of the PA28alpha subunit enhanced the MHC class I-restricted presentation of two viral epitopes and that purified PA28alpha/beta accelerated T cell epitope generation by the 20S proteasome in vitro, indicating a role for PA28alpha/beta in antigen presentation. This conclusion was recently confirmed in PA28beta gene targeted mice which were severely deficient in MHC class I-restricted antigen presentation. These mice displayed a defect in the assembly of immunoproteasomes, suggesting that a lack of the proteasome subunits LMP2, LMP7, and MECL-1 may account for the deficiency in antigen presentation. In this study we investigated whether the effect of PA28alpha/beta on antigen presentation is dependent on a change of proteasome subunit composition. We have analyzed the assembly and subunit composition of proteasomes in fibroblast transfectants overexpressing both, alpha and beta subunits of PA28. In these transfectants we found a marked enhancement in the presentation of the immunodominant H-2Ld-restricted pp89 epitope of murine cytomegalovirus, although the 20S proteasome composition was the same as in recipient cells. We, therefore, conclude that PA28alpha/beta can enhance antigen processing independently of changes in 20S proteasome subunit composition or assembly. 相似文献
80.
Smoller JW Rosenbaum JF Biederman J Susswein LS Kennedy J Kagan J Snidman N Laird N Tsuang MT Faraone SV Schwarz A Slaugenhaupt SA 《American journal of medical genetics》2001,105(3):226-235
Genes influence the development of anxiety disorders, but the specific loci involved are not known. Genetic association studies of anxiety disorders are complicated by the complexity of the phenotypes and the difficulty in identifying appropriate candidate loci. We have begun to examine the genetics of behavioral inhibition to the unfamiliar (BI), a heritable temperamental predisposition that is a developmental and familial risk factor for panic and phobic disorders. Specific loci associated with homologous phenotypes in mouse models provide compelling candidate genes for human BI. We conducted family-based association analyses of BI using four genes derived from genetic studies of mouse models with features of behavioral inhibition. The sample included families of 72 children classified as inhibited by structured behavioral assessments. We observed modest evidence of association (P = 0.05) between BI and the glutamic acid decarboxylase gene (65 kDA isoform), which encodes an enzyme involved in GABA synthesis. No significant evidence of association was observed for the genes encoding the adenosine A(1A) receptor, the adenosine A(2A) receptor, or preproenkephalin. This study illustrates the potential utility of using candidate genes derived from mouse models to dissect the genetic basis of BI, a possible intermediate phenotype for panic and phobic disorders. 相似文献