全文获取类型
收费全文 | 2343篇 |
免费 | 152篇 |
国内免费 | 2篇 |
出版年
2023年 | 4篇 |
2022年 | 16篇 |
2021年 | 25篇 |
2020年 | 10篇 |
2019年 | 17篇 |
2018年 | 16篇 |
2017年 | 24篇 |
2016年 | 46篇 |
2015年 | 61篇 |
2014年 | 87篇 |
2013年 | 240篇 |
2012年 | 125篇 |
2011年 | 142篇 |
2010年 | 102篇 |
2009年 | 94篇 |
2008年 | 147篇 |
2007年 | 169篇 |
2006年 | 164篇 |
2005年 | 171篇 |
2004年 | 163篇 |
2003年 | 143篇 |
2002年 | 149篇 |
2001年 | 23篇 |
2000年 | 22篇 |
1999年 | 37篇 |
1998年 | 22篇 |
1997年 | 25篇 |
1996年 | 16篇 |
1995年 | 18篇 |
1994年 | 13篇 |
1993年 | 15篇 |
1992年 | 10篇 |
1991年 | 17篇 |
1990年 | 11篇 |
1989年 | 18篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1984年 | 14篇 |
1983年 | 14篇 |
1982年 | 15篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 6篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1965年 | 3篇 |
排序方式: 共有2497条查询结果,搜索用时 15 毫秒
31.
Mary M. Sherman Robert P. Borris Masaru Ogura Geoffrey A. Cordell Norman R. Farnsworth 《Phytochemistry》1980,19(7):1499-1501
A new triterpene has been isolated from the root bark of Ailanthus excelsa (Simaroubaceae) and identified as 3S,24S,25-trihydroxytirucall-7-ene. 相似文献
32.
33.
Summary The present study deals with cytological observations, DNA and protein synthesis in artificially activated sea urchin eggs. The eggs were activated by means of Loeb's double treatment with butyric acid and hypertonic sea water. Most of the eggs ofHemicentrotus pulcherrimus divided when the chromosomes duplicated after formation of the first monaster and other eggs divided at a later cell cycle. In the eggs ofTemnopleurus toreumaticus, however, haploid division at the first cell cycle was observed predominantly.Activated eggs that were treated for 25 min with hypertonic sea water showed a marked uptake of3H-thymidine during the two periods of 30–40 min and 90–100 min after the double treatment. These periodic changes in the3H-thymidine uptake paralleled morphological changes within the nucleus. However, these periods of increased uptake were not observed in the eggs treated with hypertonic sea water for 60 min. During exposure to hypertonic sea water, the3H-thymidine-uptake by eggs activated with butyric acid decreased gradually. When the uptake of14C-valine by eggs was measured, a very low level was seen in unfertilized eggs. The level of uptake increased strikingly when the eggs were activated with butyric acid but was suppressed by the hypertonic treatment. However, removal of the eggs to sea water allowed the uptake to return to the former high level. This pattern suggests that the hypertonic treatment has an inhibitory effect on the synthesis of protein (or enzymes) which obstruct cleavage induction. 相似文献
34.
Two major glycoproteins of bovine peripheral nerve myelin were isolated from the acid-insoluble residue of the myelin by a procedure involving delipidation with chloroform/methanol (2:1, v/v) and chromatography on Sephadex G-200 column with a buffer containing sodium dodecyl sulfate. The separation patterns of the proteins on the gel were affected considerably by the dodecyl sulfate concentration in the elution buffer. At above 2% dodecyl sulfate concentration in the elution buffer, the glycoproteins could be separated clearly on the gel and were purified. The purified proteins, the BR protein (mol. wt. 28 000) and the PAS-II protein (mol. wt. 13 000), were homogeneous on dodecyl sulfate-polyacrylamide gel electrophoresis. The NH2-terminal amino acids of the BR and the PAS-II proteins were isoleucine and methionine, respectively. The BR protein contained glucosamine, mannose, galactose, fucose and sialic acids and the PAS-II protein contained glucosamine, mannose, galactose, fucose and glucose. Neither the BR protein nor the PAS-II were a glycosylated derivative of a basic protein of bovine peripheral nerve myelin, a deduction based on the results of amino acid analysis. The two major glycoproteins were observed commonly in the peripheral nerve myelin of cows, pigs, rabbits and guinea pigs, using dodecyl sulfate-polyacrylamide gel electrophoresis. 相似文献
35.
Doctor Masaru Wada 《Cell and tissue research》1975,159(2):167-178
The cells of the adenohypophysis of the Japanese quail were studied by both light and electron microscopy after exposure to long photoperiods or injection of lutenizing hormone-releasing hormone (LRH). Six cell types were identified in the adenohypophysis by examining alternate thick and thin sections by light and electron microscopy. In the cephalic lobe, there are four types of glandular cells. They are the prolactin cells, ACTH cells, TSH cells, and gonadotropic cells (FSH?). In the caudal lobe, there are two types of cells, STH cells and gonadotropic cells (LH?). After exposure to long daily photoperiods, gonadotropic cells in both lobes were strongly activated. They became larger and accumulated many granules. ACTH cells became vacuolated; granules were sparse. Synthetic LRH injection (10 mug/0.2 ml/day) for 10 days to the non-photostimulated quail stimulated certain numbers of the gonadotropic cells in the both lobes, although the response of the cells was less than that induced by photostimulation. No response was seen in the other cell types. 相似文献
36.
37.
38.
Fumiya Noguchi Masaru Kawato Takao Yoshida Yoshihiro Fujiwara Katsunori Fujikura Kiyotaka Takishita 《The Journal of eukaryotic microbiology》2013,60(2):158-165
It has recently been unveiled that a wide variety of microbial eukaryotes (protists) occur in chemosynthetic ecosystems, such as hydrothermal vents and methane seeps. However, there is little knowledge regarding protists associated with endemic animals inhabiting these environments. In the present study, utilizing PCR techniques, we detected fragments of the small subunit ribosomal RNA gene (SSU rRNA gene) from a particular protist from gill tissues of a significant fraction of the vesicomyid clams Calyptogena soyoae and C. okutanii complex and of the mussel Bathymodiolus platifrons and B. japonicus, all of which harbor chemosynthetic endosymbiont bacteria and dominate methane seeps in Sagami Bay, Japan. Based on the phylogeny of SSU rRNA gene, the organism in question was shown to belong to Alveolata. It is noteworthy that this protist did not affiliate with any known alveolate group, although being deeply branched within the lineage of Syndiniales, for which the monophyly was constantly recovered, but not robustly supported. In addition, the protist detected using PCR followed by sequencing was localized within gill epithelial cells of B. platifrons with whole‐mount fluorescence in situ hybridization. This protist may be an endoparasite or an endocommensal of Calyptogena spp. and Bathymodiolus spp., and possibly have physiological and ecological impacts on these bivalves. 相似文献
39.
Keitarou Suzuki Yoshikazu Terasaki Masaru Uyeda 《Journal of enzyme inhibition and medicinal chemistry》2013,28(3):183-186
The inhibitory effects of various fatty acids on three hyaluronidases (h-ST, h-SH and h-SD) and four chondroitinases (c-ABC, c-B, c-ACI and c-ACII) were examined, and their structure-activity relationships and mechanism of action were studied. The fatty acids used in this experiment showed various inhibitory activities against the enzymes. None of the fatty acids did not inhibit h-ST and h-SH. The saturated fatty acids (C 10:0 to C 22:0) showed very weak or no inhibition against h-SD, c-ABC, c-B, c-ACI and c-ACII but the unsaturated fatty acids (C 14:1 to C 24:1) with one double bond strongly inhibited the enzymes, and the inhibitory potency increased with increase in carbon chain length of the fatty acids. In contrast, the increase in number of double bonds caused a decrease in inhibitory potency against the enzymes. The position of the double bond and the stereochemistry of the cis - trans form of oleic acid (C 18:1) did not influence the inhibitory potency against the enzymes. Carboxyl and hydroxyl groups in the fatty acid molecule were concerned in the inhibition of c-ACI. Among the fatty acids, eicosatrienoic acid (C 20:3) generally inhibited h-SD, c-ABC, c-B and c-ACI, and nervonic acid (C 24:1) was a potent inhibitor of c-ACII, and the fatty acids inhibited the enzymes in a noncompetitive manner. 相似文献
40.
John Paul Wanner Roopashree Subbaiah Yelenna Skomorovska-Prokvolit Yousef Shishani Eric Boilard Sujatha Mohan Robert Gillespie Masaru Miyagi Reuben Gobezie 《Arthritis research & therapy》2013,15(6):R180