全文获取类型
收费全文 | 4250篇 |
免费 | 403篇 |
国内免费 | 2篇 |
出版年
2023年 | 15篇 |
2022年 | 31篇 |
2021年 | 89篇 |
2020年 | 50篇 |
2019年 | 56篇 |
2018年 | 65篇 |
2017年 | 64篇 |
2016年 | 107篇 |
2015年 | 231篇 |
2014年 | 191篇 |
2013年 | 255篇 |
2012年 | 380篇 |
2011年 | 305篇 |
2010年 | 204篇 |
2009年 | 135篇 |
2008年 | 229篇 |
2007年 | 253篇 |
2006年 | 206篇 |
2005年 | 216篇 |
2004年 | 224篇 |
2003年 | 202篇 |
2002年 | 187篇 |
2001年 | 43篇 |
2000年 | 37篇 |
1999年 | 34篇 |
1998年 | 89篇 |
1997年 | 43篇 |
1996年 | 46篇 |
1995年 | 35篇 |
1994年 | 41篇 |
1993年 | 30篇 |
1992年 | 43篇 |
1991年 | 30篇 |
1990年 | 39篇 |
1989年 | 40篇 |
1988年 | 25篇 |
1987年 | 19篇 |
1986年 | 26篇 |
1985年 | 24篇 |
1984年 | 31篇 |
1983年 | 32篇 |
1982年 | 40篇 |
1981年 | 26篇 |
1980年 | 30篇 |
1979年 | 23篇 |
1978年 | 17篇 |
1977年 | 22篇 |
1976年 | 19篇 |
1974年 | 12篇 |
1973年 | 9篇 |
排序方式: 共有4655条查询结果,搜索用时 109 毫秒
91.
David E. Moody Jacqueline L. James Edward A. Smuckler 《Biochemical and biophysical research communications》1980,97(2):673-679
Treatment of male rats with carbon tetrachloride, bromotrichloromethane, chloroform, 1,2-dibromoethane, 1-bromo-2-chloroethane, and 1,2-dibromo-3-chloropropane results in a decrease in cytochrome P-450 content and alterations in the relative content of fatty acids in hepatic microsomes. A high correlation was found between the loss of cytochrome P-450, the decrease in arachidonic acid (r=0.93), and the increases in linoleic (r=?0.91) and oleic acids (r=?0.89). 相似文献
92.
Summary The effect of aging on the morphology and function of the thyroid gland of the cream hamster was studied by light and electron microscopy coupled with autoradiography or histochemistry.Morphologically, aging induces an accumulation of lysosomal dense bodies and a loss of the phagocytosis of colloid droplets after stimulation with TSH. Iodine uptake and organification occur normally and thyroglobulin synthesis, estimated by autoradiography with 3H-leucine, is not different from that observed in young animals. The basal T4 and T3 plasma levels are lower in the old animals. A low iodine diet administered for several months prevents the age related accumulation of lysosomal dense bodies. Hormone secretion seems to proceed by two different mechanisms; phagocytosis of colloid droplets, the classical mechanism that decreases with age, and an additional mechanism, probably micropinocytosis, that is maintained during the whole lifespan.Presented at the First French Congress of Endocrinology, Montpellier, September 1980Work was performed under contracts n 3.4523.79 and n 3.4512.80 of the Fonds de la Recherche Scientifique Médicale, thanks to a grant of the Ministère Belge de la Politique Scientifique (Action concertée) and with the help of the Fondation Interuniversitaire pour la Recherche du Processus du Vieillissement, Belgium 相似文献
93.
94.
Jacqueline Jollès Jean-Pierre Périn Pierre Jollès 《Molecular and cellular biochemistry》1977,17(1):39-44
Summary The purification of Ostrich (Struthio camelus) egg-white lysozyme is reported. The quantitative amino acid composition, the molecular weight, the N-terminal sequence (34 amino acids) as well as kinetic studies allow to range this enzyme among the goose type lysozymes.106th communication on lysozymes. 相似文献
95.
Mohamed Saïd Hifnawy Jacqueline Vaquette Thierry Sévenet Jean-Louis Pousset André Cavé 《Phytochemistry》1977,16(7):1035-1039
Stems and leaves of Myrtopsis macrocarpa, M. myrtoidea, M. novae-caledoniae and M. sellingii yielded terpenes, sterols, coumarins, alkaloids (furoquinolines and quinolones) and amides. A new quinolone (8-methoxy flindersine) occurs in Myrtopsis macrocarpa, a new amide (N-benzoyltryptamine) in M. myrtoidea, two new coumarins (myrsellin and myrsellinol) and a new dihydrofuroquinoline (myrtopsine) in M. sellingii. Structures of the new compounds are proposed from chemical and spectroscopic evidence. 相似文献
96.
A phage-plasmid hybrid was constructed for use as a recombinant DNA vector, allowing the propagation of cloned EcoRI restriction endonuclease fragments of about 2 X 10(6) to 11 X 10(6) daltons. The colicin E1 plasmid replicon was fused to the left arm of a lambdagt generalized transducing phage with a thermolabile repressor, yielding a genome which could be replicated either by phage lambda functions or via the colicin E1 plasmid replicon. At the nonpermissive temperature, phage functions were derepressed and phage growth occurred lytically. Alternatively, at the permissive temperature, lambda functions were repressed and the vector replicated as a covalently closed circular plasmid. The phage-plasmid hybrid vector could be maintained at a copy number determined by the colicin E1 plasmid replicon and was also sensitive to amplification after chloramphenicol treatment. An EcoRI fragment of Escherichia coli DNA encoding genes of the arabinose operon also was inserted into the central portion of the vector. 相似文献
97.
98.
The heavy and light chains of pooled antibodies of the hybodont shark,Heterodontus francisci (horned shark), were subjected to amino acid sequence analysis. Yield determinations showed that more than 90% of the available polypeptides in the respective pools were sequenced. The heavy chains were homogeneous in the initial framework segment and showed a sequence homology of approximately 70% with the corresponding region of the more recently evolved nurse shark and a 45% homology with a human myeloma heavy chain. The light chains were less homogeneous and not identifiable as either kappa or lambda chains as known in higher species. The first half-cystine characteristics of the variable domain intrachain disulfide bridge of immunoglobulins was present in the same position (22 for heavy chains; 23 for light chains) in the horned shark as in mammalian species. The sequence analysis also suggested the presence of a hypervariable region in the horned shark light chains. The combined data imply that the antigen-binding function of immunoglobulins is mediated in much the same manner in this primitive shark as in more recently evolved species, including mammals. 相似文献
99.
Hermann B. Lück Jacqueline Lück Pierre Rouane 《Plant biology (Stuttgart, Germany)》1977,90(1):277-285
Die Seitenzweige von Cupressus sempervirens L. sind auf vier Orthostichen in scheinbar mehr oder weniger zufälligen, voneinander unabhängigen Mustern angeordnet. Eine auf L-Systeme sich berufende mathematische Konstruktion gestattet die Definition eines Morphismus. Acht Parameter, Periodizität der absoluten Wachstumsrate der zugrundeliegenden theoretischen Serien, die Väriation dieser Raten in komplementaren Unterserien und eine Schwellenreaktion sind die Hauptargumente. 相似文献
100.