全文获取类型
收费全文 | 3496篇 |
免费 | 203篇 |
国内免费 | 1篇 |
出版年
2022年 | 19篇 |
2021年 | 42篇 |
2020年 | 25篇 |
2019年 | 43篇 |
2018年 | 57篇 |
2017年 | 48篇 |
2016年 | 72篇 |
2015年 | 118篇 |
2014年 | 143篇 |
2013年 | 241篇 |
2012年 | 214篇 |
2011年 | 234篇 |
2010年 | 142篇 |
2009年 | 143篇 |
2008年 | 219篇 |
2007年 | 207篇 |
2006年 | 217篇 |
2005年 | 168篇 |
2004年 | 184篇 |
2003年 | 193篇 |
2002年 | 185篇 |
2001年 | 50篇 |
2000年 | 59篇 |
1999年 | 60篇 |
1998年 | 46篇 |
1997年 | 29篇 |
1996年 | 31篇 |
1995年 | 18篇 |
1994年 | 29篇 |
1993年 | 22篇 |
1992年 | 42篇 |
1991年 | 31篇 |
1990年 | 29篇 |
1989年 | 24篇 |
1988年 | 51篇 |
1987年 | 24篇 |
1986年 | 27篇 |
1985年 | 20篇 |
1984年 | 18篇 |
1983年 | 9篇 |
1982年 | 12篇 |
1981年 | 12篇 |
1980年 | 11篇 |
1979年 | 11篇 |
1977年 | 10篇 |
1975年 | 13篇 |
1974年 | 17篇 |
1973年 | 14篇 |
1972年 | 20篇 |
1971年 | 12篇 |
排序方式: 共有3700条查询结果,搜索用时 328 毫秒
61.
Motohiro Morioka† Kohji Fukunaga† Setsuko Yasugawa† Shinji Nagahiro Yukitaka Ushio Eishichi Miyamoto† 《Journal of neurochemistry》1992,58(5):1798-1809
We have investigated regional and temporal alterations in Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) and calcineurin (Ca2+/calmodulin-dependent protein phosphatase) after transient forebrain ischemia. Immunoreactivity and enzyme activity of CaM kinase II decreased in regions CA1 and CA3, and in the dentate gyrus, of the hippocampus early (6-12 h) after ischemia, but the decrease in immunoreactivity gradually recovered over time, except in the CA1 region. Furthermore, the increase in Ca2+/calmodulin-independent activity was detected up to 3 days after ischemia in all regions tested, suggesting that the concentration of intracellular Ca2+ increased. In contrast to CaM kinase II, as immunohistochemistry and regional immunoblot analysis revealed, calcineurin was preserved in the CA1 region until 1.5 days and then lost with the increase in morphological degeneration of neurons. Immunoblot analysis confirmed the findings of the immunohistochemistry. These results suggest that there is a difference between CaM kinase II and calcineurin in regional and temporal loss after ischemia and that imbalance of Ca2+/calmodulin-dependent protein phosphorylation-dephosphorylation may occur. 相似文献
62.
Phenylalanine Ammonia-Lyase Genes from Pisum sativum: Structure, Organ-Specific Expression and Regulation by Fungal Elicitor and Suppressor 总被引:3,自引:0,他引:3
63.
Masayuki Nakamichi Shinji Imakawa Yasuo Kojima Ayuko Natsume 《Primates; journal of primatology》1992,33(3):413-418
Parturition behavior of a multiparous female and her interactions with group members throughout the birth process were recorded
for a free-ranging Japanese monkey (Macaca fuscata). The female showed evidence of 18 contractions during the 35 min prior to delivery, with a mean duration and a mean intercontraction
interval of 30 sec and 96 sec, respectively. These values were similar to those in individually caged Japanese monkeys. Some
adult females remained in proximity to the female who was giving birth during the prepartum phase, and her 2-year-old daughter
watched the delivery of the infant. Even during the prepartum phase the female moved in order to keep up with the group which
traveled from the feeding site to a sleeping site in the forest. 相似文献
64.
Shinji Kakudo Kazumasa Yoshikawa Mikio Tamaki Etsuo Nakamura Hiroshi Teraoka 《Applied microbiology and biotechnology》1992,38(2):226-233
Summary In order to obtain a large quantity of glutamic-acid-specific endopeptidase of Staphylococcus aureus ATCC12600 (SPase) without cultivating its pathogenic host bacterium, expression plasmids enabling secretion of SPase from Bacillus subtilis were constructed by inserting the SPase gene into B. subtilis-Escherichia coli shuttle vectors. B. subtilis harbouring a simple recombinant plasmid containing the coding and the 5-flanking regions of SPase in the shuttle vector pHY300PLK secreted 22 mg/l of SPase into the medium. As this level was lower than that of the natural strain (45 mg/l), we tried to increase the expression level by constructing a series of hybrid plasmids with the following features: (1) the terminator sequence of the alkaline protease gene from B. subtilis, (2) the promoter and the leader sequences of the -amylase gene or of alkaline protease gene from B. amyloliquefaciens, (3) the vector pHY300PLK and the fused vector of pHY300PLK and pUB110. By using a variety of hybrid plasmids, the resulting transformants secreted SPase at levels of 33–120 mg/l. The recombinant SPase isolated from the medium was indistinguishable from the natural one with respect to its behaviour on sodium dodecyl sulphate-polyacrylamide gel electrophoresis and Western blotting as well as its enzyme activity.Correspondence to: S. Kakudo 相似文献
65.
66.
Inflammatory pseudotumor of the lung diagnosed as granulomatous lesion by preoperative brushing cytology. A case report 总被引:1,自引:0,他引:1
The clinical and cytologic features of a case of inflammatory pseudotumor of the lung are presented. Chest roentgenograms revealed a solitary circumscribed round mass in a nine-year-old boy. The mass was diagnosed as a granulomatous lesion by bronchoscopic brushing cytology. Although smears and cultures of sputum and brushing specimens were negative for tuberculosis, a tuberculin reaction was positive and antitubercular therapy was instituted. Since the mass had grown further after six months of therapy, an open lung biopsy was performed to resect the lesion and establish the diagnosis. Imprint smears of the cut surface of the lesion showed cytologic features similar to those of the brushings: short, spindle-shaped cells with a tendency to be arranged in stori-form patterns against a background of minimal necrotic debris. Histopathology established the final diagnosis of inflammatory pseudotumor, a rare granulomatous lesion radiologically resembling a true tumor. Since this lesion usually occurs in younger patients, inflammatory pseudotumor should be considered in pediatric cases with an intrapulmonary lesion that shows histiocytic spindle-shaped cells in stori-form patterns, but whose smears and cultures test negative for tuberculosis. 相似文献
67.
The relationship between dissipation of the flash-induced membranepotential across the thylakoid membrane and the high energystate was studied in Zea mays leaves. The dark decay of theflash-induced 515-nm absorbance change was accelerated by shortpreillumination of the leaf. No acceleration of the decay bypreillumination was observed when leaves were incubated in argonor CO2 gas or treated with DCMU. These effects of preilluminationand incubation were reversible. The delayed fluorescence from chlorophyll a was reversibly decreasedby incubating leaves in argon or CO2 gas, though the modes ofdepression were somewhat different from each other. In leavesincubated in argon or CO2 gas, the phase of slow decrease ofthe intensity of prompt fluorescence during illumination reversiblydisappeared. The results suggested that the dissipation of membrane potentialgenerated by a flash was accelerated after the energizationof chloroplasts in leaves, probably by increased H permeabilityof the thylakoid membrane. O2 was important in maintaining (indarkness) and forming (under illumination) the high energy statein chloroplasts in intact leaves. (Received October 1, 1980; Accepted December 15, 1980) 相似文献
68.
Cartilage-derived factor (CDF) : II. Somatomedin-like action on cultured chondrocytes 总被引:2,自引:0,他引:2
Yukio Kato Yoshio Nomura Mitsuko Tsuji Hiroaki Ohmae Masahiko Kinoshita Shinji Hamamoto Fujio Suzuki 《Experimental cell research》1981,132(2):339-347
Previously, we showed that fetal bovine cartilage contains a polypeptide that stimulates the incorporation of [35S]sulfate into proteoglycans synthesized by rat and rabbit costal chondrocytes in culture. In this paper, we report that the cartilage-derived factor (CDF) increases not only [35S]sulfate incorporation but also [3H]thymidine incorporation into rabbit chondrocytes in monolayer culture. The dose-response curve of CDF stimulation of DNA synthesis was similar in profile to that of CDF stimulation of proteoglycan synthesis. In addition, CDF markedly enhanced [3H]uridine incorporation into rabbit chondrocytes and significantly enhanced [3H]serine incorporation into total protein. These findings indicate that fetal bovine cartilage contains a factor that shows somatomedin-like activity in monolayer cultures of rabbit chondrocytes. 相似文献
69.
Adult chicken hemoglobin is heterogeneous and contains two major components, AI and AII (1). The amino acid sequence of the alpha chain of the AI component from white leghorns (small A type) was determined and compared with that of the alpha chain of the AII component, previously determined by the authors (2). An unexpectedly large difference of 65 amino acids was found between these two chains. 相似文献
70.
The aminoethylated beta polypeptide chain in AII component from the hemoglobin of adult chicken was digested with trypsin [EC 3.4.21.4] and the resulting peptides were separated and purified by ion exchange chromatography, paper chromatography, and gel filtration. Eighteen tryptic peptides, which were nonoverlapping, accounted for all of the amino acid residues in the beta polypeptide chain. The amino acid sequences of the tryptic peptides were established by a combination of enzymatic digestion and subtractive Edman degradation. 相似文献