全文获取类型
收费全文 | 23711篇 |
免费 | 2032篇 |
国内免费 | 2篇 |
出版年
2021年 | 181篇 |
2020年 | 138篇 |
2019年 | 166篇 |
2018年 | 408篇 |
2017年 | 426篇 |
2016年 | 465篇 |
2015年 | 427篇 |
2014年 | 534篇 |
2013年 | 860篇 |
2012年 | 1510篇 |
2011年 | 1646篇 |
2010年 | 883篇 |
2009年 | 613篇 |
2008年 | 1415篇 |
2007年 | 1456篇 |
2006年 | 1393篇 |
2005年 | 1253篇 |
2004年 | 1219篇 |
2003年 | 1119篇 |
2002年 | 1141篇 |
2001年 | 858篇 |
2000年 | 970篇 |
1999年 | 475篇 |
1998年 | 263篇 |
1997年 | 210篇 |
1996年 | 248篇 |
1995年 | 225篇 |
1994年 | 203篇 |
1993年 | 214篇 |
1992年 | 217篇 |
1991年 | 188篇 |
1990年 | 192篇 |
1989年 | 181篇 |
1988年 | 177篇 |
1987年 | 173篇 |
1986年 | 152篇 |
1985年 | 207篇 |
1984年 | 221篇 |
1983年 | 179篇 |
1982年 | 230篇 |
1981年 | 199篇 |
1980年 | 175篇 |
1979年 | 174篇 |
1978年 | 150篇 |
1977年 | 137篇 |
1976年 | 129篇 |
1975年 | 119篇 |
1974年 | 129篇 |
1973年 | 111篇 |
1972年 | 93篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
41.
Friedrich Häusele 《Cell and tissue research》1932,16(2):484-496
Ohne ZusammenfassungFrühere Zahnstudien erschienen in dieser Zeitschrift von H. Marcus und seinen Schülern. 相似文献
42.
Werner Mittag 《Development genes and evolution》1932,126(1):104-122
Ohne Zusammenfassung 相似文献
43.
44.
Dr. M. P. Pistillo N. Tanigaki O. Mazzoleni E. Ciccone U. Hämmerling M. Park P I. Terasaki G. B. Ferrara 《Immunogenetics》1987,25(3):145-151
Peripheral B lymphocytes obtained from three healthy individuals who had been immunized against peripheral blood lymphocytes from appropriate HLA-incompatible donors were transformed by the use of Epstein-Barr virus. The transformed blastoid B cells were repeatedly subcultured by means of cluster picking, and the HLA antibody-producing cultures were identified by testing the culture supernatants by means of the cytotoxicity assay, using the corresponding donor cells. Thus far, four cell lines that secrete cytotoxic HLA antibodies (MP1, 3, 4, and 5) have been established. Specific immunoabsorption experiments revealed that the antibody activity is carried by lambda-type IgM for MP1, by kappa-type IgM for MP3 and MP5, and by both for MP4. Specificity analysis of a panel of HLA-pretyped cells indicated that MP1 detects DQw2, whereas MP5 recognizes B7. The specificity of MP3 was similar to a DQ specificity termed DC5 (probably equivalent to TA10) but not the same. In the case of MP4, both of the lambda-type and kappa-type antibodies appeared to be directed toward new HLA class 11 determinants.Abbreviations used in this paper HLA
human major histocompatibility
- EBV
Epstein-Barr virus
- B-LCL
Blymphoblastoid cell line
- NA
not absorbed
- PBS
phosphate-buffered saline
- SPA
Sepharose protein A
- NRS
normal rabbit serum 相似文献
45.
Summary The reductive cleavage of the aclacinomycins A (I), Y (II), and B (III) by intact mycelia or subcellular fractions of the producer strain S. spec. AM 33352/F43 is suppressed in the presence of uncouplers, complex-forming agents, detergents, and some metal anions such as chromate. Increased concentration of the latter in complete cultures caused rearrangement of I to III. 相似文献
46.
Summary A mutant ofS.
chrysomallus with a D-glucose isomerase inducible by D-glucose or its catabolites was characterized. In contrast to the wild-type strain it showed a decreased catabolite repression by D-glucose of D-xylose consumption and a constitutive pentose phosphate pathway as well. A hypothesis concerning altered induction pattern of its D-glucose isomerase is discussed. 相似文献
47.
The applicability of the electron spectroscopic imaging technique for detection of the intracellular distribution of calcium in plant cells was tested with calyptra cells ofZea mays and with pollen tubes ofLilium longiflorum. After fixation in enhanced Ca2+ levels and embedding in resin, ultrathin sections were analyzed for the elemental distribution. Calcium and phosphorus were enriched in cell wall, plasma membrane, endoplasmic reticulum, mitochondria, and Golgi vesicles, mainly in granular or globular deposits appearing electron dense in transmission electron microscopy. The results demonstrated that the ESI-technique allows exact localization of calcium enrichment relative to specific cell organelles. 相似文献
48.
Paternal inheritance of chloroplast DNA in Larix 总被引:2,自引:0,他引:2
Restriction enzyme analysis was used to determine the inheritance of chloroplast DNA in conifers. The plant material studied included five individual trees of European larch (Larix decidua Mill.) and Japanese larch (Larix leptolepis Sieb. & Zucc.) and six hybrids from controlled crosses between these species. The chloroplast DNA fragment patterns generated by Bam-HI and Bcl-I were species-specific. Paternal inheritance of chloroplast DNA patterns was found in most Larix crosses. One hybrid showed maternal chloroplast DNA patterns. In addition, two other hybrids had mixed Bam-HI patterns suggesting recombination between maternal and paternal chloroplast DNA. The mechanisms favoring paternal inheritance in conifers are not known. Paternal inheritance of chloroplast DNA is suggested it to be a general phenomenon in conifers. 相似文献
49.
Werner Eckert 《Biogeochemistry》1987,4(1):15-26
The process of H2S oxidation by the phototrophic bacteriaThiocapsa roseopersicina andChlorobium phaeobacteroides, respectively, was monitored using a Pt-glass-Ag0, Ag2S electrode combination without liquid junction. Due to the resulting pe(pH) and pH2S plottings three steps can be distinguished: oxidation of H2S to an S(0) state, oxidation of S (0) to SO4
2–, and oxidation of the remaining H2S directly to SO4
2–. Differences between the investigated bacteria exist with respect to their individual oxidation strategies.Thiocapsa apparently stops oxidizing H2S at pH2S 7.5 (e.g. 10–7.5M H2S) and shifts to the utilization of the intracellularly stored S (0). In contrastChlorobium utilizes its extracellularly stored sulfur parallel to the extracellular H2S fraction. The corresponding Pt-sensor responses (pe7 values) were found to be similar to the corresponding partial redox equilibria (p7 values) of H2S oxidation stoichiometries as proposed by Van Niel (1931) and Trüper (1964). It is concluded that the recording of pe enables investigators to understand (and control) in situ redox processes, independent of their thermodynamic equilibration, only bound to changes of electroactivity vs. sensor. 相似文献
50.
Summary Phenylalanine production from E. coli KA 197/pJN6 (plasmid harboring genes for aro F, phe AFBR, AmpR and TcR) was studied under varying nutritional conditions in batch and continuous cultures. In batch culture experiments where growth was deliberately interrupted by limiting concentrations of sulphate and phosphate the phenylalanine production continued from the non-growing cells. However, the depletion of phosphate resulted in an immediate cessation of phenylalanine production but thereafter a low specific rate of phenylalanine formation resumed, while the decrease in specific rate of product formation was less after sulphate depletion. In the chemostat experiments, however, phosphate limitation was the only case where the specific rate of phenylalanine formation remained constant, while at the corresponding time in sulphate and glucose limited chemostats it was declining respectively had ceased. 相似文献