全文获取类型
收费全文 | 12520篇 |
免费 | 916篇 |
国内免费 | 4篇 |
专业分类
13440篇 |
出版年
2022年 | 65篇 |
2021年 | 95篇 |
2020年 | 70篇 |
2019年 | 96篇 |
2018年 | 120篇 |
2017年 | 133篇 |
2016年 | 185篇 |
2015年 | 247篇 |
2014年 | 339篇 |
2013年 | 715篇 |
2012年 | 572篇 |
2011年 | 577篇 |
2010年 | 402篇 |
2009年 | 381篇 |
2008年 | 605篇 |
2007年 | 598篇 |
2006年 | 567篇 |
2005年 | 569篇 |
2004年 | 589篇 |
2003年 | 592篇 |
2002年 | 559篇 |
2001年 | 461篇 |
2000年 | 478篇 |
1999年 | 386篇 |
1998年 | 159篇 |
1997年 | 158篇 |
1996年 | 131篇 |
1995年 | 141篇 |
1994年 | 149篇 |
1993年 | 123篇 |
1992年 | 277篇 |
1991年 | 246篇 |
1990年 | 245篇 |
1989年 | 240篇 |
1988年 | 231篇 |
1987年 | 190篇 |
1986年 | 201篇 |
1985年 | 172篇 |
1984年 | 126篇 |
1983年 | 138篇 |
1982年 | 117篇 |
1981年 | 77篇 |
1980年 | 83篇 |
1979年 | 122篇 |
1978年 | 75篇 |
1977年 | 75篇 |
1975年 | 56篇 |
1973年 | 58篇 |
1972年 | 54篇 |
1970年 | 52篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Isono S.; Tanaka A.; Sho Y.; Konno A.; Nishino T. 《Journal of applied physiology》1995,79(6):2132-2138
62.
Summary A novel cultivation method using a microporous membrane (membrane-surface liquid culture) was developed, in which moulds are grown on the membrane surface with its opposite side being in contact with a liquid medium. The amount of neutral protease from Aspergillus oryzae produced was more than 10 times higher than that produced by the conventional liquid culture. 相似文献
63.
Zhao Ying Hiromasa Tojo Takanori Komatsubara Manabu Nakagawa Masami Inada Sumio Kawata Yuji Matsuzawa Mitsuhiro Okamoto 《生物化学与生物物理学报:疾病的分子基础》1994,1226(2):201-205
Enzyme activity, protein contents, and mRNA contents of group II phospholipase A2 (PLA2) in hepatocellular carcinoma (HCC) surgically obtained from 8 patients were compared with those in either its neighboring liver tissues or control liver tissues. The PLA2 specific activity towards the mixed micelles of 1-palmitoyl-2-oleoyl-phosphatidylglycerol and cholate was significantly greater in the tumor tissues (6.62 ± 1.46 nmol/min/mg) than those in the surrounding liver tissues (1.33 ± 0.22 nmol/min/mg) and controls (0.43 ± 0.04 nmol/min/mg). The results of immunoblot analysis using a specific anti-human group II PLA2 antibody and of Northern blot analysis using a human group II PLA2 cDNA as a probe demonstrated that group II PLA2 was responsible for the increased enzyme activity. The contents of immunoreactive group II PLA2 in the tumor tissues (8.81 ± 1.24 ng/mg) were significantly higher than those in the surrounding liver tissues (1.77 ± 0.27 ng/mg); those in the control tissues were below the analytical range of the method used. The group II PLA2 mRNA was also significantly increased in the tumor tissues, compared with that in the surrounding liver tissues, whereas it was not detectable in th controls. This indicates that group II PLA2 in HCC is induced at the pretranslational level. 相似文献
64.
Ayaaki Ishizaki Tomoko Ueda Kenji Tanaka Peter F. Stanbury 《Biotechnology letters》1993,15(5):489-494
Summary The relative contributions of lactate inhibition and the generation of sterile (undividing) cells to the low xylose utilisation rate of Lactococcus lactis IO-1 was investigated. The lactate inhibition constant of xylose grown cells was shown to be 9.3 times more than that of glucose grown cells. However, the sterile cell production rate and LDH inactivation rate of the xylose cultures were at least 10 times less than the glucose cultures. Thus, it is suggested that the slower substrate consumption rate in xylose medium is caused mainly by the large inhibition constant for the end product. 相似文献
65.
66.
67.
Kawarabayasi Yutaka; Tanaka Ayako; Ohara Osamu; Arakawa Taku; Oka Masanori; Kato Hisako; Morita Miyo; Fujisawa Hisao 《DNA research》1994,1(6):289-296
To sequence a DNA segment inserted into a cosmid vector underthe directed sequencing strategy, we established a simple andrapid method for generating nested deletions which uses thein vitro packaging system of bacteriophage T3 DNA. The principleis based on the previous finding that this system can translocateany linear double-stranded DNA up to 40 kb into the phage capsidin a time-dependent manner and the encapsulated DNA becomesDNase-resistant. For this purpose, we constructed a cosmid vectorthat carries two different antibiotic selection markers at bothsides of the multiple cloning site, and after insertion of aDNA segment, the clone was linearized by -terminase at the cossite. After the packaging reaction in vitro followed by DNasetreatment, the encapsulated DNA was introduced into Escherichiacoli cells to give clones with unidirectional deletions by differentialantibiotic selection. Restriction and sequence analyses of deletionclones demonstrated that an ordered set of clones with nesteddeletions, ranging from less than 1 kb to 25 kb, was createdfrom either the end of the DNA segment. Thus, nested deletionclones that cover the entire region of a 40-kb cosmid insertcan be obtained by a single packaging reaction, and its restrictionmap can be simultaneously obtained. 相似文献
68.
69.
To study the roles of m5C in the differentiation of rice calli derived from protoplasts (protoclones), the m5C level of the total DNA was analyzed using the32P post-labeling method. The level of m5C in regenerable and nonregenerable protoclones was similar, as was in calli and leaves of plants regenerated from the same
protoclones. Treatment with 0.5 mM 5-azacytidine caused significant reduction of the level of m5C and of the regeneration frequency of callus. Significantly increased m5C levels were observed during prolonged culture. 相似文献
70.
Masao Suzuki Chizuru Tsuruoka Tatsuaki Kanai Takeshi Kato Fumio Yatagai Masami Watanabe 《Biological Sciences in Space》2003,17(4):302-306
We investigated the difference in cell-killing effect and mutation induction between carbon- and neon-ion beams in normal human cells. Carbon- and neon-ion beams were accelerated by the Riken Ring Cyclotron (RRC) at the Institute of Physical and Chemical Research in Japan. Cell-killing effect was measured as the reproductive cell death using the colony formation assay. Mutation induction at the HPRT locus was detected to measure 6-thioguanine-resistant clones. The mutation spectrum of the deletion pattern of exons of induced mutants was analyzed using the multiplex polymerase chain reaction (PCR). Cell-killing effect was almost the same between carbon- and neon-ion beams with similar linear energy transfer (LET) values, while there observed a large difference in mutation frequency. Furthermore, in the case of neon-ion beams 60% of mutants showed total deletions and 35-40% showed partial deletions, while 95-100% of carbon-ion induced mutants showed total deletions. The results suggest that different ion species may cause qualitative and quantitative difference in mutation induction even if the LET values are similar. 相似文献