全文获取类型
收费全文 | 9857篇 |
免费 | 463篇 |
国内免费 | 4篇 |
专业分类
10324篇 |
出版年
2023年 | 43篇 |
2022年 | 46篇 |
2021年 | 117篇 |
2020年 | 130篇 |
2019年 | 160篇 |
2018年 | 317篇 |
2017年 | 282篇 |
2016年 | 394篇 |
2015年 | 368篇 |
2014年 | 469篇 |
2013年 | 682篇 |
2012年 | 598篇 |
2011年 | 717篇 |
2010年 | 425篇 |
2009年 | 327篇 |
2008年 | 546篇 |
2007年 | 603篇 |
2006年 | 592篇 |
2005年 | 550篇 |
2004年 | 501篇 |
2003年 | 528篇 |
2002年 | 439篇 |
2001年 | 216篇 |
2000年 | 178篇 |
1999年 | 130篇 |
1998年 | 96篇 |
1997年 | 45篇 |
1996年 | 39篇 |
1995年 | 32篇 |
1994年 | 30篇 |
1993年 | 27篇 |
1992年 | 31篇 |
1991年 | 29篇 |
1990年 | 22篇 |
1989年 | 23篇 |
1988年 | 24篇 |
1987年 | 28篇 |
1986年 | 16篇 |
1985年 | 39篇 |
1984年 | 30篇 |
1983年 | 26篇 |
1982年 | 29篇 |
1981年 | 29篇 |
1980年 | 22篇 |
1979年 | 26篇 |
1978年 | 22篇 |
1977年 | 31篇 |
1953年 | 18篇 |
1952年 | 40篇 |
1887年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
13.
Anna Nowakowska-Waszczuk Andrzej Sokoŀowski 《Applied microbiology and biotechnology》1987,26(4):363-364
Summary In an air-lift fermenter, the following production was obtained from 125 g sucrose in mineral medium at pH 2.5 : 15.76 g mycelium dry wt, 107.2 g citric acid anhydrous and 0.594 mol CO2 within 138 h (run I) and 13.72 g mycelium dry wt, 114.28 g citric acid and 0.516 mol CO2 within 144 h (run II). Initially, the carbon content of consumed sugar and products did not balance. At the end of fermentation, the carbon content of the products was 0.9%–5.5% higher than that of the consumed sugar. For the purpose of the calculations the carbon content in mycelium was accepted as 0.462.The work was a part of Project No 04.11 CPBP, topic No 2.24 相似文献
14.
When cells are briefly exposed to cis-diamminedichloroplatinum (II) before lysis in high sodium dodecyl sulfate-urea solutions, the high molecular-weight nucleic acids pelleted by ultracentrifugation contain an increased level of bound proteins when compared to a similar fraction from untreated cells. Subsequent shearing of the pelleted DNA followed by treatment with DNase permits electrophoretic and immunoblot analysis of the crosslinked proteins. In the present study such experiments were carried out with reference to nuclear envelope pore complex proteins in the differentiating L8 rat skeletal muscle cells. The results show that (i) whereas the major lamin proteins crosslinked to DNA in both myoblast and myotubes, lamin B is crosslinked to a greater extent to DNA in myotubes; (ii) a 62-kDa lectin-binding glycoprotein is apparently situated differently with respect to DNA in myotube nuclei; and (iii) the crosslinking pattern of the nuclear matrix proteins to DNA is qualitatively similar in myoblast and myotubes. In addition, lamin C′, a modified form of lamin C, not observed in intact nonmuscle cells previously [[31.] J. Biol. Chem. 260, 1895–1900], exists as a native component of the nuclear lamina in rat skeletal myotubes but not in myoblasts. These results point to significant structural alterations in the proteins of the nuclear lamina-pore complex during myogenesis. 相似文献
15.
Improvement in stability of an immobilized fungal laccase 总被引:4,自引:0,他引:4
Andrzej Leonowicz Jawed M. Sarkar Jean-Marc Bollag 《Applied microbiology and biotechnology》1988,29(2-3):129-135
Summary A laccase of the basidiomyceteTrametes versicolor was immobilized on porous glass beads that were activated with 3-aminopropyltriethoxysilane and glutaraldehyde. The support immobilized 100% of the enzyme, whereupon 90% of the original activity was retained. After immobilization, the enzyme was active in a wider pH and temperature range, and its heat stability and reuse were greatly improved compared to those of the free laccase. The immobilized enzyme was found reusable in treating different substrates, either recycled alone or in a sequential order. 相似文献
16.
Determination was made of the proportion of selected by-products (acetaldehyde, ethyl acetate, methanol, propanol, isobutanol, 2-methyl-butanol, 3-methyl-butanol) of batch and continuous ethanol fermentation carried out with the use of yeastSaccharomyces cerevisiae, strain 0–11, cells immobilized by adsorption on selected carriers (foamed polystyrene, bone shot, beech wood chips, porous glass) as well as by entrapping in calcium alginate and calcium pectinate gel. 相似文献
17.
Jerzy Szykuła Cezary Hebda Józef Orpiszewski Klaudia Sagańska 《Biotechnology letters》1991,13(12):917-922
Summary Microbial transformations of neutral fraction (NF) and upgraded neutral fraction (UNF) of Polish tall oil byMycobacterium sp. MB 3683 were performed. Final metabolites and yields were compared to bioconversion of pure -sitosterol. Additionally, origin of a new metabolite —5-androsta-3,6,17-trione was proved by transformation of UNF in the presence of labeled -sitosterol. 相似文献
18.
Juliusz Perkowski Jerzy Chełkowski Ronald D. Plattner Piotr Goliński 《Mycotoxin Research》1991,7(2):115-120
Maize cobs withFusarium ear rot were collected at 1986 season and five infected byFusarium graminearum were analyzed for presence of triohothecenes and zearalenone. Collected material was subsampled forFusarium damaged kernels and corresponding axial stems and healthy looking kernels. All investigated cobs contained deoxynivalenol (DON) (range 18.0–131.5 mg/kg) and zearalenone (ZEA) (range 0.38–2.17 mg/kg), in four cobs 15-acetyl-deoxynivalenol (15-AcDON) (range 5.2–6.2 mg/kg) was present and two cobs besides three all metabolites contained 3-acetyl-deoxynivalenol (3-AcD0N) (range 0.5–0.8 mg/kg).The average of individual toxins amount in axial stems: in mg/kg was equal to: DON — 110.36, ZEA — 4.57, 15-AcD0N — 16.66, and 3-AcD0N — 1.32.Fusarium damaged kernels contained in average the following amount (mg/kg) of: DON 77.00, ZEA 0.98, 15-AcD0N 3.78 and 3-AcD0N 0.06. Healthy looking kernels contained DON 1.96 mg/kg and ZEA 0.07 mg/kg only. Cooccurrence of 3-AcDON and 15-AcDON in two samples was an interesting finding. The amount of DON in total cob was highly correlated (r = 0.94) with percentage ofFusarium damaged kernels in given ear. 相似文献
19.
Paleoecological reconstruction of changes in the productivity of a small,meromictic lake in Southern Ontario,Canada 总被引:1,自引:0,他引:1
Some aspects of the paleoproductivity of meromictic Crawford Lake, near Toronto, are inferred from a study of its sedimentary pigments, and diatoms. Several stages of lake development are observed over the 35 cm-deep sediment core removed from the center of Crawford Lake. Evidence of changes in lake productivity during the last 300 years was reflected by significant stratigraphic sediment pigment changes which were associated with European settlement in the Crawford Lake watershed and recent alterations associated with the area's operation by the Conservation Authority (1969 — present). One of the most important factors correlated with paleoproductivity was land clearance (mainly logging of white oak and pine). Deforestation during the last century is correlated with an increase in the amount of algal pigments deposited in the lake's sediments during the 1800's. During the last 10 years a striking increase in the accumulation of chlorophyll derivatives was observed. This is correlated with a dramatic increase in the number of visitors to the lake.Stratigraphic changes in the ratio of cyanobacterial to phototrophic bacterial pigment accumulation are used to infer changes which occurred during the shift from mesotrophy to eutrophy in Crawford Lake. 相似文献
20.
Janusz Dabrowski Michael Hauck Elzbieta Romanowska Andrzej Gamian 《Carbohydrate research》1988,180(2):163-174
The main features of the primary structure of the octasaccharide, -
-Glcp-(1→2)--
-Glcp-(1→2)-[-
-GalpNAc- (1→3)]--
-Galp-(1→3)--
-Glcp-(1→3)-[-
-Hepp-(1→7)]--
-Hepp-(1→3)--
-Hep, have been determined in the ab initio manner by 1H-n.m.r. spectroscopy without resorting to biochemical methods of analysis. Several nontypical interresidue n.O.e. values point to a preferred solution conformation of the molecule. 相似文献