全文获取类型
收费全文 | 4017篇 |
免费 | 380篇 |
国内免费 | 2篇 |
专业分类
4399篇 |
出版年
2023年 | 15篇 |
2022年 | 34篇 |
2021年 | 80篇 |
2020年 | 45篇 |
2019年 | 46篇 |
2018年 | 58篇 |
2017年 | 58篇 |
2016年 | 95篇 |
2015年 | 216篇 |
2014年 | 178篇 |
2013年 | 240篇 |
2012年 | 362篇 |
2011年 | 294篇 |
2010年 | 195篇 |
2009年 | 130篇 |
2008年 | 218篇 |
2007年 | 248篇 |
2006年 | 199篇 |
2005年 | 207篇 |
2004年 | 222篇 |
2003年 | 192篇 |
2002年 | 181篇 |
2001年 | 34篇 |
2000年 | 31篇 |
1999年 | 34篇 |
1998年 | 84篇 |
1997年 | 33篇 |
1996年 | 45篇 |
1995年 | 34篇 |
1994年 | 40篇 |
1993年 | 28篇 |
1992年 | 33篇 |
1991年 | 24篇 |
1990年 | 31篇 |
1989年 | 35篇 |
1988年 | 25篇 |
1987年 | 21篇 |
1986年 | 22篇 |
1985年 | 24篇 |
1984年 | 32篇 |
1983年 | 30篇 |
1982年 | 38篇 |
1981年 | 26篇 |
1980年 | 31篇 |
1979年 | 23篇 |
1978年 | 11篇 |
1977年 | 21篇 |
1976年 | 17篇 |
1974年 | 14篇 |
1973年 | 9篇 |
排序方式: 共有4399条查询结果,搜索用时 15 毫秒
51.
52.
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
53.
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
54.
55.
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
56.
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
57.
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
58.
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
59.
60.
Summary The spinning apparatus ofLinyphia triangularis, adult females and males, was studied with the scanning electron microscope and the main anatomical and histochemical characteristics of the silk glands, including the epigastric apparatus of males, are presented. The epigastric glands seem to be important for the construction of sperm webs. A detailed account of the use of the different kinds of silk in web building is given.The spinning apparatus ofLinyphia closely corresponds to the araneid pattern. Characteristic of linyphiid spiders is the poor development of the aciniform glands. Corresponding to the minor importance of capture threads forLinyphia, the triads (aggregate and flagelliform glands) are less developed than in Araneidae.Linyphia make much less use of the secretions of the piriform glands for connecting threads than Araneidae. Capture threads adhere to other threads by their own glue; other threads seem mostly to be bound to one another by the secretion of the minor ampullate glands whose chemical properties, inLinyphia, appear especially adapted to this function. Neither the anatomical and histochemical data concerning the spinning apparatus nor the structure of the webs provide any indication of close relationships between Linyphiidae and Agelenidae, as was recently claimed. 相似文献