全文获取类型
收费全文 | 25924篇 |
免费 | 2588篇 |
国内免费 | 18篇 |
专业分类
28530篇 |
出版年
2022年 | 193篇 |
2021年 | 317篇 |
2020年 | 219篇 |
2019年 | 269篇 |
2018年 | 312篇 |
2017年 | 298篇 |
2016年 | 471篇 |
2015年 | 772篇 |
2014年 | 807篇 |
2013年 | 1111篇 |
2012年 | 1249篇 |
2011年 | 1267篇 |
2010年 | 943篇 |
2009年 | 780篇 |
2008年 | 980篇 |
2007年 | 988篇 |
2006年 | 962篇 |
2005年 | 931篇 |
2004年 | 1020篇 |
2003年 | 959篇 |
2002年 | 897篇 |
2001年 | 732篇 |
2000年 | 709篇 |
1999年 | 681篇 |
1998年 | 354篇 |
1997年 | 364篇 |
1996年 | 362篇 |
1995年 | 319篇 |
1994年 | 259篇 |
1993年 | 287篇 |
1992年 | 614篇 |
1991年 | 514篇 |
1990年 | 559篇 |
1989年 | 549篇 |
1988年 | 446篇 |
1987年 | 446篇 |
1986年 | 397篇 |
1985年 | 394篇 |
1984年 | 416篇 |
1983年 | 332篇 |
1982年 | 294篇 |
1981年 | 286篇 |
1980年 | 255篇 |
1979年 | 341篇 |
1978年 | 275篇 |
1977年 | 297篇 |
1976年 | 223篇 |
1975年 | 244篇 |
1974年 | 248篇 |
1973年 | 223篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
112.
113.
Peter W. Van Arsdale 《American anthropologist》2003,105(2):409-410
Healing the Modern in. Central Javanese City. Steve Ferzacca. Durham, NC: Carolina Academic Press, 2001. 280 pp. 相似文献
114.
Anton Pauw Sunshine A. Van Bael Halton A. Peters Steven D. Allison José L. C. Camargo Miguel Cifuentes-Jara Aurlstela Conserva Teresa Garcia Restom Tamara Heartsill-Scalley Scott A. Mangan Gabriela Nunez-lturri Elsie Rivera-Ocasio Mark Rountree Susanne Vetter Carolina Volkmer de Castllho 《Biotropica》2004,36(3):410-413
115.
Kristel Van Steen Nadia Tahri Geert Molenberghs 《Biometrical journal. Biometrische Zeitschrift》2004,46(2):187-202
Until recently, the most common parametric approaches to study the combined effects of several genetic polymorphisms located within a gene or in a small genomic region are, at the genotype level, logistic regressions and at the haplotype level, haplotype analyses. An alternative modeling approach, based on the case/control principle, is to regard exposures (e.g., genetic data such as derived from Single Nucleotide Polymorphisms – SNPs) as random and disease status as fixed and to use a marginal multivariate model that accounts for inter‐relationships between exposures. One such model is the multivariate Dale model. This model is based on multiple logistic regressions. That is why the model, applied in a case/control setting, leads to straightforward interpretations that are similar to those drawn in a classical logistic modeling framework. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
116.
117.
H. Pottel B. W. Van der Meer W. Herreman H. Depauw 《European biophysics journal : EBJ》1987,15(1):47-58
In the preceding paper, an alternative method is described for obtaining information about the reorientational behavior of a fluorophore in a membrane system from frequency domain measurements. To demonstrate this new analysis procedure, we present data for the probe-molecule 1,6-diphenyl-1,3,5-hexatriene (DPH) in l--dimyristoyl- and l--dipalmitoylphosphatidylcholine (DMPC and DPPC) obtained with two different phase fluorometers: the SLM 4800A Subnanosecond Spectrofluorometer which has only three fixed frequencies available (6, 18 and 30 MHz) and the recently constructed continuously variable multifrequency phasefluorometer (Gratton and Limkeman 1983).It will be shown that reasonable information about the anisotropy behavior of a fluorophore can be obtained even if only three frequencies are used. The phase modulation technique was also used to check the new expression for the anisotropy, r(t), called the general model and introduced by Van der Meer et al. (1984). The parameters P
2, P
4 and D, obtained from the nonlinear least squares fit (Bevington 1969) for this general model, confirm the results from the pulse technique of Ameloot and coworkers (Ameloot et al. 1984; Pottel et al. 1986). 相似文献
118.
G. Van den Eede B. Dreyfus K. Goethals M. Van Montagu M. Holsters 《Molecular & general genetics : MGG》1987,206(2):291-299
Summary After random Tn5 mutagenesis of the stem-nodulating Sesbania rostrata symbiont strain ORS571, Nif-, Fix- and Nod- mutants were isolated. The Nif- mutants had lost both free-living and symbiotic N2 fixation capacity. The Fix- mutants normally fixed N2 in the free-living state but induced ineffective nodules on S. rostrata. They were defective in functions exclusively required for symbiotic N2 fixation. A further analysis of the Nod- mutants allowed the identification of two nod loci. A Tn5 insertion in nod locus 1 completely abolished both root and stem nodulation capacity. Root hair curling, which is an initial event in S. rostrata root nodulation, was no longer observed. A 400 bp region showing weak homology to the nodC gene of Rhizobium meliloti was located 1.5 kb away from this nod Tn5 insertion. A Tn5 insertion in nod locus 2 caused the loss of stem and root nodulation capacity but root hair curling still occurred. The physical maps of a 20.5 kb DNA region of nod locus 1 and of a 40 kb DNA region of nod locus 2 showed no overlaps. The two nod loci are not closely linked to nif locus 1, containing the structural genes for the nitrogenase complex (Elmerich et al. 1982). 相似文献
119.
Cyclic nucleotide phosphodiesterase (3',5'-cyclic nucleotide nucleotidohydrolase, EC 3.1.4.17) activity isolated from Phaseolus vulgaris L. cv. Limberg seedlings was partially purified and characterized by fractional (NH4 )2 SO4 precipitation, DEAE-cellulose chromatography, chromatography on 3',5'-cAMP-agarose, gel permeation chromatography and chromatofocusing. A crude enzyme preparation, a 30–65% (NH4 )2 SO4 pellet, showed an acidic pH optimum. The enzyme activity was stimulated by imidazole and divalent cations such as Ca2+ , Mg2+ and Mn2+ , whereas NaF, PPi and Fe3+ were inhibitory. Isobutylmethylxanthine had no significant effect on the plant enzyme. An MI of 42 000 was estimated by gel permeation high performance liquid chromatography. By chromatography on 3',5'-cAMP-agarose a phosphodiesterase was resolved that produced 5'-AMP as sole reaction product. 相似文献
120.