全文获取类型
收费全文 | 2914篇 |
免费 | 196篇 |
学科分类
生物科学 | 3110篇 |
出版年
2023年 | 8篇 |
2022年 | 21篇 |
2021年 | 36篇 |
2020年 | 14篇 |
2019年 | 31篇 |
2018年 | 44篇 |
2017年 | 44篇 |
2016年 | 59篇 |
2015年 | 105篇 |
2014年 | 135篇 |
2013年 | 155篇 |
2012年 | 199篇 |
2011年 | 192篇 |
2010年 | 126篇 |
2009年 | 138篇 |
2008年 | 188篇 |
2007年 | 198篇 |
2006年 | 157篇 |
2005年 | 177篇 |
2004年 | 160篇 |
2003年 | 145篇 |
2002年 | 141篇 |
2001年 | 39篇 |
2000年 | 53篇 |
1999年 | 47篇 |
1998年 | 23篇 |
1997年 | 30篇 |
1996年 | 17篇 |
1995年 | 22篇 |
1994年 | 21篇 |
1993年 | 16篇 |
1992年 | 29篇 |
1991年 | 24篇 |
1990年 | 34篇 |
1989年 | 33篇 |
1988年 | 36篇 |
1987年 | 28篇 |
1986年 | 21篇 |
1985年 | 17篇 |
1984年 | 15篇 |
1983年 | 32篇 |
1982年 | 15篇 |
1981年 | 11篇 |
1980年 | 9篇 |
1979年 | 15篇 |
1978年 | 7篇 |
1977年 | 10篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1973年 | 4篇 |
排序方式: 共有3110条查询结果,搜索用时 0 毫秒
21.
Kimio Fukami Shinya Nishimura Masamichi Ogusa Miki Asada Toshitaka Nishijima 《Hydrobiologia》1997,358(1-3):245-249
A continuous culture system for a benthic food diatom Nitzschia sp. wasestablished by using properties of high nutrient and clean of deep seawater(DSW). DSW collected from 320 m depth in Muroto City, Japan, was introducedinto a glass-pipe bioreactor (14 cm length, 3 cm diam.) containing glassbeads of 0.5 cm diam. as substrata for the alga, and it was incubated at18°C · 80Em–2sec–1 · L:D=14:10. The chlorophyll a yield of benthicdiatoms in a reactor as a unit of surface area of the substratum was only0.001–0.003 g cm–2 when the flow rate of DSW was 0(batch culture conditions). However, when DSW was supplied continuously to areactor, the yield increased to 1.4 g-chl.a cm–2 alongwith the increase in flow rate of DSW. Moreover, amounts of chl.a washed outof the system were negligible, 0.0014 to 0.0045%, even though theflow rate of DSW was as much as 25 times h–1, suggesting thatsloughing of benthic diatoms from the substratum was minimized. Although theyield of diatoms fluctuated significantly at the time that the DSW wascollected, the variation could be minimized by increasing the flow rate ofDSW. These results indicate that the continuous culturing system with DSWsupports the stable and effective mass culture of benthic food diatom. 相似文献
22.
Shinya Nomoto Michiaki Takasaki Hiroshi Naraoka Kaoru Harada 《Origins of life and evolution of the biosphere》1984,14(1-4):123-130
Flames of flammable gases, when blown against a surface of an aqueous solution of organic compounds, were found to induce oxidation as well as other reactions in the solution. This reaction would be regarded as a new model for formation of bioorganic molecules in the primitive hydrosphere exposed to some radical-containing atmosphere. 相似文献
23.
Effect of salt on photocycle and ion-pumping of halorhodopsin and third rhodopsinlike pigment of Halobacterium halobium 总被引:2,自引:0,他引:2 下载免费PDF全文
The cytoplasmic membranes of Halobacterium halobium contain at least three retinal pigments: bacteriorhodopsin (bR), halorhodopsin (hR), and a third rhodopsinlike pigment (tR). The amplitudes of the phototransient in the photolysis of hR and tR were measured in various salt solutions. Halogen ion (except fluoride) was required to retain the photocycle of hR. Parallels between the amplitude of the phototransient of hR and the magnitude of the photo-induced tetraphenylphosphonium (TPP+) uptake suggests that hR is a light-driven halogen pump, which supports the hypothesis by Schobert and Lanyi (J. Biol. Chem., 1982, 257:10306-10313). The order of effectiveness of halogen was Br- greater than Cl- greater than I-. On the other hand, no specific ion was required to retain the photocycle of tR, and tR was concluded to be nonelectrogenic. 相似文献
24.
A 37-year-old woman with typical features of pseudohypoparathyroidism (chronic tetany, paresthesia, persistent hypocalcemia, round face, short stature, short metacarpals and metatarsals, cucutaneous calcification and lack of response to exogenous and endogenous parathyroid hormone as regards urinary phosphate and cyclic AMP excretion) was treated with oral administration of 2 microgram/day of 1alphaOH-vitamin D3. Serum calcium started to rise within 3 days returning to the normal level with disappearance of symptoms referrable to hypocalcemia. Such a favorable effect of a small dose of 1alphaOH-vitamin D3 in a patient with typical hypoparathyroidism suggests an important role of disturbance of 1alpha-hydroxylation of vitamin D3 by the kidney in the pathogenesis of calcium and phosphorus abnormality in this disease. Forty-four cases of pseudohypoparathyroidism in the Japanese literature were briefly reviewed. 相似文献
25.
A rapid method is described for the preparation of serum alpha1-acid glycoprotein from rats with inflammation induced with turpentine oil injection. The protein obtained by two purification steps, batchwise adsorption with DEAE-cellulose followed by chromatography on CM-cellulose, was proved to be native alpha1-acid glycoprotein in a high degree of purity by electrophoretical, immunological, ultracentrifugal and carbohydrate analysis. The monospecific and potent antiserum to this protein was prepared by immunizing rabbits with the desialyzed material emulsified with Freund's incomplete adjuvant. Using purified alpha1-acid glycoprotein and its specific antiserum, the concentration of alpha1-acid glycoprotein in rat serum was determined by single radial immunodiffusion. Abnormally high levels of its concentration (5-6 times higher than the control) were observed in inflammatory and tumor bearing rats. 相似文献
26.
K Baba N Tsuda H Yabuuchi S Konishi A Fujinami G Tsujino M Takahashi 《Biken journal》1980,23(2):89-94
For the purpose of preventing spread of infection to high risk children whose immunities were severely impaired by intensive chemotherapy or for some other reason, when cases of varicella occurred in a children's ward or in a family, healthy adults (mothers and a doctor) were immediately given live varicella vaccine, blood was collected from these adults 5 to 7 days after vaccination and the whole blood or plasma including the buffy coat was transferred in the high risk children. Subsequently the children showed little or no clinical reaction, and follow-up studies by the neutralizing test and skin test with varicella antigen indicated that their inapparent or subclinical varicella infection occurred in them and that their immunity to varicella was lasting. Skin tests with varicella antigen showed that booster reaction occurred in adults with a previous history of varicella as early as 5 to 7 days after vaccination. The cellular immunity thus induced in the donors may have played a role in preventing a clinical reaction in the high risk children. Thus passive transfer of vaccine-induced immunity seems a convenient and effective method for preventing infection in subjects whose immune capacities are severely impaired. 相似文献
27.
Abstract Polyvinyl alcohol (PVA) was utilized by a symbiotic mixed culture which was composed of Pseudomonas putida VM15A and Pseudomonas sp. VM14C. The PVA oxidase was found in the culture fluid, membrane, and cytosol fractions of VM15C. The membrane-bound PVA oxidase was purified by several steps of chromatography. The enzyme (p I = 9.6) exhibited the maximum activity at pH 8.0 to 8.4 and 45°C, and utilized secondary alcohol as well as PVA. The enzyme showed the PVA dehydrogenating activity linking with phenazine ethosulfate, indicating the possibility that PVA oxidation is coupled with an electron transport chain on the bacterial membrane. 相似文献
28.
K Kariya A Yamauchi S Hattori Y Tsuda Y Okada 《Biochemical and biophysical research communications》1982,107(4):1461-1466
To explore the possibility that cyclic nucleotides control green algal growth and division, chemostat cultures were assayed for cyclic nucleotides. Substantial qualities of cAMP were found in cells and in extracellular millieu. Most cGMP molecules were extracellular. Slowing cell growth by slowing chemostat dilution caused reversible changes in cellular morphology and cyclic nucleotide levels. During slowed growth cAMP level increased dramatically; cGMP level decreased. New cells resulting from division were not released from original cell wall. 相似文献
29.
Hiroyuki Horitsu Yasushi Takahashi Junkō Tsuda Keiichi Kawai Yoshio Kawano 《Applied microbiology and biotechnology》1983,18(6):358-360
Summary Living Aspergillus terreus cells were entrapped in polyacrylamide gels and employed in both replacement batch and continuous column reactors to produce itaconic acid from glucose.With the replacement batch reactor, maximum itaconic acid productivity was observed under the following conditions: pH 2.50, temperature at 35°C, addition of NH4H2PO4 and MgSO4·7H2O. Using the continuous reactor, the maximum itaconic acid yield was 60 mg/h/40 g of gel. The biocatalyst activity or half-life was about 10 days. 相似文献
30.
The mouse S-antigen gene. Comparison with human and Drosophila 总被引:2,自引:0,他引:2