全文获取类型
收费全文 | 2504篇 |
免费 | 198篇 |
出版年
2023年 | 5篇 |
2022年 | 11篇 |
2021年 | 34篇 |
2020年 | 13篇 |
2019年 | 15篇 |
2018年 | 28篇 |
2017年 | 26篇 |
2016年 | 43篇 |
2015年 | 115篇 |
2014年 | 102篇 |
2013年 | 122篇 |
2012年 | 186篇 |
2011年 | 166篇 |
2010年 | 116篇 |
2009年 | 116篇 |
2008年 | 153篇 |
2007年 | 167篇 |
2006年 | 154篇 |
2005年 | 138篇 |
2004年 | 152篇 |
2003年 | 175篇 |
2002年 | 126篇 |
2001年 | 43篇 |
2000年 | 18篇 |
1999年 | 41篇 |
1998年 | 42篇 |
1997年 | 37篇 |
1996年 | 26篇 |
1995年 | 35篇 |
1994年 | 29篇 |
1993年 | 25篇 |
1992年 | 20篇 |
1991年 | 21篇 |
1990年 | 12篇 |
1989年 | 24篇 |
1988年 | 19篇 |
1987年 | 11篇 |
1986年 | 12篇 |
1985年 | 8篇 |
1984年 | 11篇 |
1983年 | 14篇 |
1982年 | 15篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1979年 | 9篇 |
1978年 | 10篇 |
1977年 | 11篇 |
1976年 | 5篇 |
1972年 | 4篇 |
1971年 | 6篇 |
排序方式: 共有2702条查询结果,搜索用时 15 毫秒
31.
32.
Martine E. Laethem Frans M. Belpaire Pascal Wijnant Marie-Thrse Rosseel Marc G. Bogaert 《Chirality》1994,6(5):405-410
The influence of endotoxin-induced inflammation on the enantioselective pharmacokinetics of propranolol, oxprenolol, and verapamil, which bind to α1-acid glycoprotein, was studied in the rat. The racemic mixtures were given orally. In the control animals, for propranolol and oxprenolol, the plasma concentrations of the (R)-enantiomer were higher than those of the (S)-enantiomer, while for verapamil the reverse was true. Protein binding and intrinsic clearance are the main factors responsible for this enantioselectivity. After endotoxin treatment, for the three drugs tested the plasma concentrations and the plasma binding of both enantiomers were significantly increased. This effect was more pronounced for (R)-propranolol, (R)-oxprenolol, and (S)-verapamil than for their respective antipodes. The enantioselective effect of endotoxin on the plasma concentrations of the drugs studied seems mainly due to the enantioselective increase in binding to α1-acid glycoprotein. © 1994 Wiley-Liss, Inc. 相似文献
33.
Martine Crasnier Valérie Dumay Antoine Danchin 《Molecular genetics and genomics : MGG》1994,243(4):409-416
In Escherichia coli, adenylate cyclase activity is regulated by phosphorylated EnzymeIIAGlc, a component of the phosphotransferase system for glucose transport. In strains deficient in EnzymeIIAGlc, CAMP levels are very low. Adenylate cyclase containing the D414N substitution produces a low level of cAMP and it has been proposed that D414 may be involved in the process leading to activation by EnzymeIIAGlc. In this work, spontaneous secondary mutants producing large amounts of cAMP in strains deficient in EnzymeIIAGlc were obtained. The secondary mutations were all deletions located in the cya gene around the D414N mutation, generating adenylate cyclases truncated at the carboxyl end. Among them, a 48 kDa protein (half the size of wild-type adenylate cyclase) was shown to produce ten times more cAMP than wild-type adenylate cyclase in strains deficient in EnzymeIIAGlc. In addition, this protein was not regulated in strains grown on glucose and diauxic growth was abolished. This allowed the definition of a catalytic domain that is not regulated by the phosphotransferase system and produces levels of cAMP similar to that of regulated wild-type adenylate cyclase in wild-type strains grown in the absence of glucose. Further analysis allowed the characterization of the COOH-terminal regulatory domain, which is proposed to be inhibitory to the activity of the catalytic domain. 相似文献
34.
35.
Martine de Boer Maaike te Lintel Hekkert Jiang Chang Bibi S. van Thiel Leonie Martens Maxime M. Bos Marion G. J. de Kleijnen Yanto Ridwan Yanti Octavia Elza D. van Deel Lau A. Blonden Renata M. C. Brandt Sander Barnhoorn Paula K. Bautista-Niño Ilona Krabbendam-Peters Rianne Wolswinkel Banafsheh Arshi Mohsen Ghanbari Christian Kupatt Leon J. de Windt A. H. Jan Danser Ingrid van der Pluijm Carol Ann Remme Monika Stoll Joris Pothof Anton J. M. Roks Maryam Kavousi Jeroen Essers Jolanda van der Velden Jan H. J. Hoeijmakers Dirk J. Duncker 《Aging cell》2023,22(3):e13768
36.
37.
Béatrice Drouet Luis Garcia Dominique Simon-Chazottes Marie Geneviève Mattei Jean-Louis Guénet Arnold Schwartz Gyula Varadi Martine Pinçon-Raymond 《Mammalian genome》1993,4(9):499-503
Using both chromosomal in situ hybridization and molecular techniques, we report the genetic localization of the gene coding for the alpha 1 subunit of the skeletal slow Ca2+ current channel/DHP receptor gene (Cchl1a3) on human Chromosome (Chr) 1 (1q31–1q32 region) and on mouse Chr 1 region (F-G). On the basis of single-strand conformation polymorphism (SSCP-PCR) analysis in an interspecific backcross, we have determined that the Cchl1a3=mdg (muscular dysgenesis) locus is very closely linked to the myogenin (Myog) locus. 相似文献
38.
Can the biotic nestedness matrix be used predictively? 总被引:3,自引:1,他引:3
The biotas of a suite of neighboring patches of remnant vegetation often form a series of nested sub-sets, in which the species present in species-poor patches are non-random sub-sets of those present in richer patches. There has been recent interest in ways in which this knowledge may be used to aid conservation. We focus here on whether nested patterns can be used predictively. If nestedness in a fragmented system increases over time through biotic relaxation, locations where particular species may become extinct or are likely to colonize might be predictable and this could be useful in threatened-species management. We used the Temperature Calculator of Atmar and Patterson (1995) to arrange a matrix of bird species' occurrences in a series of buloke Allocasuarina leuhmannii woodland remnants so that nestedness was maximized. Probability bands generated by the calculator were used to predict possible colonization and extinction events. We then re-surveyed the avifauna of the fragments after a seven-year interval to test these predictions. Although nestedness increased between the two survey periods, there was no linear relationship between the generated probability of extinctions or colonizations and the accuracy of the predictions. The predictions derived from the calculator were no more accurate than a second set of predictions generated by use of a simple non-nested model. Despite the increase in nestedness, the arrangement of sites in each of the two maximally packed matrices was substantially different. For the nestedness matrix to generate accurate predictions, an increase in nestedness must be due to a minimization of unexpected species presences and absences rather than an extensive redistribution of species among remnants, as we found. The potential utility of nested patterns in predicting systematic colonization and extinction events should be further evaluated in other, less dynamic, fragmented systems such as those undergoing biotic relaxation. 相似文献
39.
Marc Pauly Isabelle Kayser Martine Schmitz Fernand Ries François Hentges Mario Dicato 《Journal of molecular evolution》1995,41(6):974-978
The mdr1 gene, first member of the human multidrug-resistance gene family, is a major gene involved in cellular resistance to several drugs used in anticancer chemotherapy. Its product, the drug-excreting P-glycoprotein, shows a bipartite structure formed by two similar adjacent halves. According to one hypothesis, the fusion of two related ancestral genes during evolution could have resulted in this structure. The DNA sequence analysis of the introns located in the region connecting the two halves of the human mdr1 gene revealed a highly conserved poly(CA) · poly (TG) sequence in intron 15 and repeated sequences of the Alu family in introns 14 and 17. These repeated sequences most likely represent molecular fossils of ancient DNA elements which were involved in such a recombination event.
Correspondence to: M. Pauly 相似文献
40.
Offshore fluxes of Cu, Zn, Cd, Pb and Hg were calculated based onresidual flow patterns and salinity gradients along the Belgian
coast. Theresidual flow lines along the Belgian coast are more or less parallel to thecoast except in the area where the north-easterly
flowing watermass comingfrom the Channel encounters the south-westerly-oriented Scheldt outflow,forming a residual hydrodynamical
front. From the steady-state salinitypattern, diffusion coefficients perpendicular to the residual flow werededuced; they
ranged from 21 to 108 m2 s-1.
Offshore fluxes of dissolved and particulate trace metals based on diffusiveand mixing processes are calculated. The steady
state profiles of dissolvedmetals show a dilution effect in the coastal waters, reaching an almostconstant concentration in
the marine watermass in the 1981–1983dataset. The ratios of the Scheldt input of trace metals to the totaldissolved offshore
flux vary from 38 to 55% (1981–1983),depending on the kind of metal, and from 55 to 91% (1995–1996).The ratio of the Scheldt
input to the dissolved metal flow parallel to thecoast, is in both periods (1981–1983 and 1995–1996), smallerthan 1%. The
steady-state concentration profiles of particular metalsversus salinity are fairly constant in the coastal-estuarine and marinewatermasses,
but decrease very abruptly from the first to the secondwatermass. Assuming a conservative behaviour of the particular metals,offshore
fluxes and the resulting concentration increases agree fairly wellwith the observed values. The ratios of the Scheldt input
to the particulatetrace metal offshore flux vary between 30 to 46% (1981–1983)and 13 to 37% (1995–1996). The contribution
of the Scheldtestuary to the flows parallel to the coast ranges from 1.6 to 2.9%(1981–1983) and from 0.6 to 1.6% (1995).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献