全文获取类型
收费全文 | 28921篇 |
免费 | 3665篇 |
国内免费 | 29篇 |
出版年
2016年 | 247篇 |
2015年 | 315篇 |
2014年 | 400篇 |
2013年 | 667篇 |
2012年 | 638篇 |
2011年 | 688篇 |
2010年 | 485篇 |
2009年 | 404篇 |
2008年 | 589篇 |
2007年 | 644篇 |
2006年 | 612篇 |
2005年 | 614篇 |
2004年 | 620篇 |
2003年 | 636篇 |
2002年 | 641篇 |
2001年 | 1847篇 |
2000年 | 1830篇 |
1999年 | 1434篇 |
1998年 | 462篇 |
1997年 | 465篇 |
1996年 | 474篇 |
1995年 | 422篇 |
1994年 | 425篇 |
1993年 | 419篇 |
1992年 | 1068篇 |
1991年 | 1080篇 |
1990年 | 1058篇 |
1989年 | 1025篇 |
1988年 | 955篇 |
1987年 | 896篇 |
1986年 | 767篇 |
1985年 | 746篇 |
1984年 | 586篇 |
1983年 | 506篇 |
1982年 | 368篇 |
1981年 | 341篇 |
1980年 | 331篇 |
1979年 | 560篇 |
1978年 | 444篇 |
1977年 | 412篇 |
1976年 | 336篇 |
1975年 | 455篇 |
1974年 | 468篇 |
1973年 | 414篇 |
1972年 | 393篇 |
1971年 | 310篇 |
1970年 | 258篇 |
1969年 | 241篇 |
1968年 | 225篇 |
1967年 | 205篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
L. Marklund M. Johansson U. Gustafsson L. Andersson A. K. Winterö M. Fredholm P. D. Thomsen 《Animal genetics》1993,24(5):333-338
Restriction fragment length polymorphisms (RFLPs) were described for the porcine loci for β-glucosidase (GBA) and the β-polypeptide 1 of the Na+, K+-transporting ATPase (ATP1B1). Linkage analyses using a three-generation pedigree provided evidence for the assignment of ATP1B1, GBA and two microsatellite loci (S0001 and S0067) to a previously described linkage group comprising the loci for blood group L (EAL) and an anonymous microsatellite (S0097). The linear order of the six markers was determined with confidence by multipoint analyses and the length of the linkage group was estimated at 88 CM. This linkage group was assigned to pig chromosome 4 on the basis of a previous physical localization of the ATP1B1 gene. In situ hybridization data for S0001 presented in this study were consistent with a localization on chromosome 4 and suggested a regional localization to 4pl2-pl3. The present study reveals conflicting data concerning the genetic localization of the K88 loci controlling the expression of the receptors for the E. coli pilus antigens. One group has reported data suggesting a loose linkage between K88 and EAL, now mapped to chromosome 4, whereas two other groups have found linkage between K88 and the transferrin locus (TF), mapped to chromosome 13 by in situ hybridization. 相似文献
22.
U. Calvet B. Balza N. Maillet P. Leandri G. Rossignol J. R. Gautier J. Corraze 《Andrologie》1991,1(3):133-135
The authors report their experience of 414 injections of prostaglandin E1 (prostine). The diagnostic orientation between functional or organic impotence was assessed through questionaires and more particularly on the presence or absence of nocturnal or morning erections. The prostine reconditioning and self injection use techniques are precised: 80% of positive responses with better results in the oldest patients, whatever their medical antecedents. No relation between positive response to prostaglandin E1 and normal nocturnal erections could be found. Patients still presenting erections can present good or bad responses. This confirms the results previously given only allow us to put in evidence the good functional and anatomic state of cavernous bodies, without any etiological orientation (not mentioning the cases in which these self-injections reveal the presence of deformation, bend or fibrosis). The acceptance of self injection is low (30%) as well as a regular and prolonged medical observance (only 15%). This work confirms the low rate of local complications after repeated injections and the low rate of prolonged erections or priapism during Test 1. However, these possibilities must incite to prudence as for the generalization of this kind of treatment, out of specialized centers. 相似文献
23.
Precursors of both conventional and Ly-1 B cells can escape feedback inhibition of Ig gene rearrangement 总被引:1,自引:0,他引:1
Experiments with transgenic mice carrying rearranged Ig transgenes have shown that membrane bound Ig molecules cause feedback inhibition of endogenous Ig gene rearrangement. However, this inhibition is never complete. It has been postulated that escape from feedback may be a property of the Ly-1 B cell subset, whereas rearrangement of endogenous Ig genes may be completely inhibited in conventional B cells. This possibility was investigated in transgenic mice carrying a lambda transgene under the control of the H chain enhancer. It was found that kappa producing B cells in these lambda transgenic mice were for the most part, although not exclusively, of the conventional B cell phenotype. Examination of peritoneal exudate cells revealed that a large proportion of Ly-1 B cells also express kappa. Adoptive transfer of bone marrow from adult lambda transgenic mice, a source of conventional B cell precursors, resulted in the production of relatively high levels of serum kappa 2 to 3 mo after transfer into recipient SCID mice. A high proportion of donor B cells in the spleen produced endogenous kappa protein with or without co-production of lambda. It is concluded that precursors of both conventional and Ly-1 B cells can escape feedback inhibition of L chain gene rearrangement. 相似文献
24.
25.
26.
A model for several algal species which compete both for light and for nutrients, and which are also subject to settling and diffusion, is considered. The settling speeds and diffusion coefficients are assumed to be small, in a sense to be made precise later, and a singular perturbation argument is used. In certain cases vertical segregation of the algal species is observed, and the mechanism for this is interpreted biologically.Supported by the Danish Natural Science Research Council (Grant No. 11-8321) 相似文献
27.
28.
29.
U. R. Kalkote R. R. Joshi R. A. Joshi T. Ravindranathan K. B. Bastawde S. G. Patil D. V. Gokhale 《Biotechnology letters》1992,14(9):785-788
Summary The Enzymatic enantioselective hydrolysis of prochiral 1,4-cyclopent-2-ene diacetate (3) was carried out using yeast and fungal cultures from inhouse culture collection. Of all the cultures tested, the yeast sp. NCIM 3574 gave 4 (S)-hydroxy-1 (R)- acetoxy-cyclopent-2-ene (4b) in high optical yields (99% ee). 相似文献
30.
B Nyasse B Fransson U Ragnarsson 《International journal of peptide and protein research》1990,36(3):316-319
The resolving power of liquid chromatography systems containing 1-pentane sulfonate, previously used to analyze basic hydrophilic peptides related to substrates of cAMP-dependent protein kinase, has been studied with respect to diastereomeric peptides. A set of peptides comprising RRASV and its five diastereomers containing one D-amino acid were used as model compounds. Complete resolution of all the peptides could be accomplished both with ethanol and acetonitrile as organic modifiers. The separation of the various peptides within the set turned out to be only modestly changed under the conditions investigated. These new results clearly demonstrate the potential of the chromatography systems studied. 相似文献