全文获取类型
收费全文 | 23835篇 |
免费 | 359篇 |
国内免费 | 750篇 |
专业分类
24944篇 |
出版年
2023年 | 1165篇 |
2022年 | 819篇 |
2021年 | 562篇 |
2020年 | 366篇 |
2019年 | 742篇 |
2018年 | 720篇 |
2017年 | 646篇 |
2016年 | 212篇 |
2015年 | 253篇 |
2014年 | 453篇 |
2013年 | 502篇 |
2012年 | 282篇 |
2011年 | 1643篇 |
2010年 | 524篇 |
2009年 | 545篇 |
2008年 | 568篇 |
2007年 | 652篇 |
2006年 | 591篇 |
2005年 | 589篇 |
2004年 | 743篇 |
2003年 | 565篇 |
2002年 | 732篇 |
2001年 | 1080篇 |
2000年 | 1066篇 |
1999年 | 1089篇 |
1998年 | 1130篇 |
1997年 | 1016篇 |
1996年 | 519篇 |
1995年 | 295篇 |
1994年 | 184篇 |
1993年 | 159篇 |
1992年 | 135篇 |
1991年 | 164篇 |
1990年 | 118篇 |
1989年 | 130篇 |
1988年 | 137篇 |
1987年 | 128篇 |
1985年 | 217篇 |
1984年 | 503篇 |
1983年 | 478篇 |
1982年 | 394篇 |
1981年 | 363篇 |
1980年 | 377篇 |
1979年 | 345篇 |
1978年 | 212篇 |
1977年 | 179篇 |
1976年 | 178篇 |
1975年 | 156篇 |
1974年 | 126篇 |
1973年 | 93篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
J De Coninck I Verdier-Denantes F Duyme S Bouquelet V Dumortier 《Journal of industrial microbiology & biotechnology》2000,25(1):58-61
Oxygen concentrations stimulated growth (maximum number of cells) and protease secretion by Tetrahymena thermophila. Agitation and aeration conditions for growth and protease secretion were optimised by a central composite design. The best
optimised combination was a stirrer speed of 338 rpm and an aeration of 1 vvm. Journal of Industrial Microbiology & Biotechnology (2000) 25, 58–61.
Received 24 September 1999/ Accepted in revised form 06 March 2000 相似文献
13.
A selective system toxic towards mammalian cells expressing the liver-specific isozyme of alcohol dehydrogenase (L-ADH) has been developed. A number of alpha-unsaturated primary and secondary alcohols were assayed for their ability to serve as substrates for rat liver ADH and were screened for cytotoxicity towards L-ADH+ and L-ADH- cells. 1-Propen-3-ol and 1-penten-3-ol were identified as agents showing selective cytotoxicity. Reconstruction experiments demonstrated that 1-propen-3-ol at a concentration of 15 microM could be used to recover L-ADH- clones from mixed populations of L-ADH+ and L-ADH cells. Cells expressing the non-allelic S-ADH isozyme were not killed under these conditions. The selective system defined in this report is thus isozyme-specific. 相似文献
14.
15.
In this study we construct a phylogenetic hypothesis for the relatedness among disjunct subspecies of Cyclamen repandum and its two allopatric congeners, C. creticum and C. balearicum in order to examine the evolutionary divergence of currently isolated populations across the western Mediterranean. The most
parsimonious phylogenetic tree obtained from sequencing the cpDNA trnL (UAA) intron suggests a major phylogeographic divide in southern Greece between two clades. The first clade comprises samples
of C. repandum subsp. peloponnesiacum (from the Peloponnese) and C. creticum (from Crete). The second comprises samples of C. repandum subsp. repandum (from Croatia, Italy, southern France, Corsica, Sardinia and Sicily), C. repandum subsp. rhodense (from Rhodes and Kos) and C. balearicum (from the Balearic Islands and southern France). These data suggest that C. creticum has evolved in allopatry from C. repandum subsp. peloponnesiacum and that C. balearicum and C. repandum ssp. rhodense have diverged from C. repandum subsp. repandum at its western and eastern distribution limits. At one small site on Corsica, a population of C. repandum may have introgressed with relictual populations of C. balearicum. These divergence patterns illustrate how a phylogenetic perspective can be used to better understand the evolution of endemism
in the Mediterranean flora.
Received February 19, 2001 Accepted August 22, 2001 相似文献
16.
Focal contacts of spreading platelets with the substratum 总被引:1,自引:0,他引:1
Contacts with glass substratum formed by the spreading rabbit platelets were examined by an antibody-exclusion method; monoclonal antibodies against 80 kD bovine serum protein were used. It was found that platelets form focal contacts in the course of spreading. The size of the largest focal contacts formed by platelets is smaller than that of the contacts formed by fibroblasts. The antibody-exclusion method revealed focal contacts of platelets much more clearly than interference reflection microscopy (IRM). The similarity of reactions involved in spreading platelets and of large nucleus-containing tissue cells is discussed. 相似文献
17.
Abstract The growth, biomass δ13C values, and ability to accumulate titratable acidity at night were compared in eight environmental treatments for Cremnophila linguifolia, Sedum greggii, and their F1 hybrid. In the phytotron, differences in treatment daylength, day/night temperature and water availability were all found to have effects on total plant dry weight, nocturnal accumulation of titratable acidity and biomass δ13C value of at least some of the genotypes. However, there were differences between the genotypes both in the magnitude and direction of response of the phenotypic properties to the treatment variables. The phytotron δ13C values ranged from -12.9 to -19.2‰ for C. linguifolia, from -22.2 to -33.4‰ for S. greggii, and from -19.2 to -24.9‰ for the hybrid. After with-holding water for 76 h both C. linguifolia and the hybrid had midday Ψleaf values of -0.23 MPa; however, S. greggii had a value of -1.05 MPa. In contrast to past observations of other species, the daily watered plants of C. linguifolia had less negative δ13C values than did the plants watered only weekly. 相似文献
18.
A simple apparatus was developed to allow 12 petri plates to be poured simultaneously by hand. It was used when screening
bacterial isolates from sewage and dog feces for their ability to detect phages from these sources. This was done to assess
the ease with which source-specific phage hosts can be isolated from these sources of fecal pollution. Host bacteria that
consistently detected phages from sewage were easily isolated from sewage. These bacterial isolates did not detect phages
from dog feces. Host bacteria were not isolated from dog feces even after screening hundreds of colonies from fecal samples
from six dogs. Journal of Industrial Microbiology & Biotechnology (2000) 24, 124–126.
Received 06 July 1999/ Accepted in revised form 05 November 1999 相似文献
19.
20.
Cortinarius sarcoflammeus is proposed as a new species belonging to subgenus Dermocybe, on the basis of its morphological, chemical and ecological characters. The strong red-orange colour of the context and stipe
base, large spores, sphagnicolous habitat and high dermorubin content are characteristic for the new species. Holotypes of
C. huronensis and C. huronensis var. olivaceus have been examined for comparison, and their differences discussed. Photographs and line drawings of C. sarcoflammeus are added.
Received February 13, 2001 Accepted March 23, 2001 相似文献