全文获取类型
收费全文 | 4599篇 |
免费 | 198篇 |
国内免费 | 3篇 |
出版年
2022年 | 15篇 |
2021年 | 54篇 |
2020年 | 25篇 |
2019年 | 47篇 |
2018年 | 74篇 |
2017年 | 45篇 |
2016年 | 84篇 |
2015年 | 129篇 |
2014年 | 163篇 |
2013年 | 320篇 |
2012年 | 316篇 |
2011年 | 283篇 |
2010年 | 200篇 |
2009年 | 188篇 |
2008年 | 307篇 |
2007年 | 285篇 |
2006年 | 299篇 |
2005年 | 281篇 |
2004年 | 309篇 |
2003年 | 282篇 |
2002年 | 270篇 |
2001年 | 39篇 |
2000年 | 46篇 |
1999年 | 41篇 |
1998年 | 61篇 |
1997年 | 48篇 |
1996年 | 40篇 |
1995年 | 39篇 |
1994年 | 36篇 |
1993年 | 35篇 |
1992年 | 40篇 |
1991年 | 47篇 |
1990年 | 35篇 |
1989年 | 41篇 |
1988年 | 37篇 |
1987年 | 18篇 |
1986年 | 23篇 |
1985年 | 21篇 |
1984年 | 26篇 |
1983年 | 24篇 |
1982年 | 19篇 |
1981年 | 13篇 |
1980年 | 15篇 |
1979年 | 7篇 |
1978年 | 9篇 |
1976年 | 8篇 |
1975年 | 14篇 |
1974年 | 9篇 |
1973年 | 7篇 |
1972年 | 6篇 |
排序方式: 共有4800条查询结果,搜索用时 31 毫秒
91.
When thiamine concentration in subculture medium was rapidlylowered to nil, soybean cells in suspension became necroticand stopped growing entirely. When it was gradually lowered,cell growth was vigorous until the concentration was reducedto 7.8?103 mg/liter. The cells at this level of thiamineceased growing for a time, but prolonged culture in the samemedium resulted in the appearance of fresh white cells whichcould be easily distinguished from the old brown, necrotic cellsin the aggregates. These new cell lines could be subculturedwith further reduction in the thiamine supply, growing as largeraggregates of about 4 mm in diameter. New cell lines were similarly obtained by prolonged culturesin media containing a thiamine precursor; three lines appearedto be habituated to the pyrimidine moiety and one to the thiazolemoiety. The latter cell line could be subcultured without thiamineand its precursors for at least eight passages. These habituatedcells were characterized by the increase of the dry to freshweight ratio and by their growth in large aggregates.
1Present address: Section of Phytochemical Research, Eisai Co.,Ltd., Kawashima, Gifu 483, Japan. (Received December 15, 1978; ) 相似文献
92.
On the basis of recent neurophysiological findings on the mammalian visual cortex, a selforganizing neural network model is proposed for the understanding of the development of complex cells. The model is composed of two kinds of connections from LGN cells to a complex cell. One is direct excitatory connections and the other is indirect inhibitory connections via simple cells. Inhibitory synapses between simple cells and complex cells are assumed to be modifiable. The model was simulated on a computer to confirm its behavior. 相似文献
93.
94.
95.
Koji Sode Masahiro Tatara Haruko Takeyama J. Grant Burgess Tadashi Matsunaga 《Applied microbiology and biotechnology》1992,37(3):369-373
Summary Versatility of gene transfer by transconjugation in marine cyanobacteria was demonstrated. In this study, seven different marine cyanobacteria were used as recipient cells. First, transconjugation was carried out using the mobilizable transposon (Tn5) carrying plasmid pSUP1021. Transconjugants were observed in all marine cyanobacteria tested. Second, the broad-host-range vector pKT230 (IncQ) was tested for transconjugation. pKT230 has been successfully transferred in a marine cyanobacterium Synechococcus sp. NKBG15041C, and replicated as an autonomous replicon without alteration in the restriction enzyme pattern. A maximum transfer efficiency of 5.2 × 10–4 transconjugants/recipient cell was observed, when mating was performed on agar plates containing low salinity (0.015 m NaCl) medium. This is the first study to demonstrate gene transfer in marine cyanobacteria via transconjugation.
Correspondence to: K. Sode 相似文献
96.
M Hiraiwa Y Uda S Tsuji T Miyatake B M Martin M Tayama J S O'Brien Y Kishimoto 《Biochemical and biophysical research communications》1991,177(3):1211-1216
Sialidase isolated from human placenta is associated with several proteins including acid beta-galactosidase, carboxypeptidase, N-acetyl-alpha-galactosaminidase, and others. These proteins are thought to form an aggregated complex during isolation of sialidase. One of the proteins of 60 kDa was recently identified by Potier et al. (Biochem. Biophys. Res. Comm. 173, 449-456, 1990) as a sialidase protein: this protein also cross-reacted with anti-prosaposin antibodies. We have isolated this protein and from the following evidence identified it as a heavy chain component of immunoglobulin G and not sialidase or a derivative of prosaposin. On gel filtration HPLC, sialidase activity and the 60 kDa protein were clearly separated from one another. The 60 kDa protein cross-reacted not only with antibodies raised against human saposins A, C, and D, but also with second antibody (goat anti-rabbit immunoglobulin G antibody) alone. This 60 kDa protein strongly cross-reacted with anti-human immunoglobulin G antibodies. The sequence of the initial 15 amino acids from the N-terminus of the 60 kDa protein was identical to the sequence of an immunoglobulin G heavy chain protein Tie (gamma 1). 相似文献
97.
S Matsuda H Suzuki T Yoshimoto S Yamamoto A Miyatake 《Biochimica et biophysica acta》1991,1084(2):202-204
Arachidonate 12-lipoxygenase of porcine leukocytes, which was purified to homogeneity by immunoaffinity chromatography, was analyzed for iron content by atomic absorption spectrophotometry. The enzyme contained 0.70 +/- 0.09 g atom of iron per mol of enzyme (mean +/- S.D., n = 4). Inorganic iron, which was added to the enzyme solution as an internal standard, was recovered in almost 100% yield. Among various iron chelators tested, only 2,2'-dipyridyl at 1 mM inactivated the enzyme by 87%, but the enzyme was not reactivated by the addition of excess ferrous or ferric iron. 相似文献
98.
Haruo Nagayama Koji Nagano Akira Ikezaki Tetsuo Tashiro 《Chronobiology international》1991,8(3):203-209
To investigate the possibility of chronotherapy with antidepressants for patients with depression, we gave single daily doses of clomipramine 150 mg/day to 30 patients with depression at three different times of day, i.e., morning, noon, or before bedtime, using a double-blind method over a 4-week period. Beneficial effects differed according to the administration time of day, with the most effective result being found for the administration at noon. Time-dependent differences in side effects were observed in tremors and dryness of mouth. An additional 10 patients were administered their medications three times a day by traditional, equally divided doses, and the efficacy was inferior than daily single doses at noon. The study results showed the significance of the administration time of day for the benefits and side effects of antidepressant therapy for depression. 相似文献
99.
100.
Kiyoshi Ohkawa Takashi Hatano Naoko Takizawa Kazue Shinmoto Kyosuke Yamada Makoto Matsuda Koji Takada Yutaka Tsukada 《In vitro cellular & developmental biology. Animal》1992,28(6):449-454
Summary A human yolk sac tumor cell line, TG1, which was established from a testicular yolk sac tumor, was found to replicate continuously
in a chemically defined medium supplemented with Na2SeO3 (ISRPMI). TG1 produced several plasma proteins and growth factors: albumin, alpha-fetoprotein (AFP), ferritin, carcinoembryonic
antigen, beta-2-microglobulin, polyamine, neuron specific enolase, tissue polypeptide antigen, transferrin (Tf), epidermal
growth factor, and platelet derived growth factor. By analysis of lectin (LcHA)-affinity electrophoresis, to examine the microheterogeneity
of carbohydrate chains of synthetic glycoproteins, TG1 cells cultured with ISRPMI produced only LcHA reactive Tf and AFP based
on core fucose attached to asparagine-linkedN-acetylglucosamine residues instead of LcHA-nonreactive Tf and AFP produced by TG1 cells cultured with fetal bovine serum
(FBS)-containing medium.α1-6 Fucosyltransferase activity was significantly greater in the TG1 cells cultured with ISRPMI (39.9±1.5 pmol · h−1 · mg−1 protein) than cultured with FBS-containing media (18.2±1.2 pmol · h−1 · mg−1 protein). These results have indicated that the selective increase ofα1-6 fucosyltransferase occurred when the cells were cultured with the FBS-free synthetic media. 相似文献