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排序方式: 共有1719条查询结果,搜索用时 15 毫秒
1.
Juana Magdalena Mats Forsman Mauro V. Lenzini Alain Brans Jean Dusart 《FEMS microbiology letters》1992,99(1):101-105
Two beta-lactamase genes called blaL and blaU have been cloned independently in Liège and in Ume?, from Streptomyces cacaoi. Genes blaL and blaU were found to differ largely in their nucleotide sequences, although the encoded proteins both belonged to the class A of beta-lactamases (active-site serine penicillinases). DNA-hybridization and polymerase chain reaction assays have now demonstrated that both blaL and blaU genes were present in the S. cacaoi strains used in Liège and in Ume?. 相似文献
2.
Climate change is expected to affect natural populations in many ways. One way of getting an understanding of the effects of a changing climate is to analyze time series of natural populations. Therefore, we analyzed time series of 25 and 20 years, respectively, in two populations of the citril finch (Carduelis citrinella) to understand the background of a dramatic increase in wing length in this species over this period, ranging between 1.3 and 2.9 phenotypic standard deviations. We found that the increase in wing length is closely correlated to warmer winters and in one case to rain in relation to temperature in the summer. In order to understand the process of change, we implemented seven simulation models, ranging from two nonadaptive models (drift and sampling), and five adaptive models with selection and/or phenotypic plasticity involved and tested these models against the time series of males and females from the two population separately. The nonadaptive models were rejected in each case, but the results were mixed when it comes to the adaptive models. The difference in fit of the models was sometimes not significant indicating that the models were not different enough. In conclusion, the dramatic change in mean wing length can best be explained as an adaptive response to a changing climate. 相似文献
3.
4.
Mats Thulin 《Nordic Journal of Botany》1993,13(1):49-50
It is argued that the original material of Maerua macrocarpa consists of elements from three different species: M. denhardtiorum, Thilachium thomasii and Capparis tornentosa . A lectotypification is proposed that makes M. macrocarpa a synonym of M. denhardtiorum . 相似文献
5.
6.
O L Segal V N Mats I V Bobrova 《Nauchnye doklady vysshe? shkoly. Biologicheskie nauki》1989,(5):59-64
The protein content has been determined by means of cytointerferometry in neurons of fields CA-1 and CA-3 of the dorsal hippocampus in rats, which were trained in a conditioned reflex of two-way avoidance (CRTA) with the action of subcutaneously injected enkephalin cyclic analogue (ECA) in a dose 10 mkg. It has been found that after ECA injection the protein content in the neuronal nuclei of the hippocampal CA-3 field reduces. The acceleration of the CRTA elaboration occurring during the action of ECA is accompanied by a drastic increase of the protein content in the neuronal nuclei of the CA-3 field. The ECA administration to the rats of the active control groups to which were presented the same number of unpaired conditioned and unconditioned stimuli as during the CRTA elaboration also enhances the protein content in the neurons of the CA-3 field. The rats of all investigated groups in the neurons of the CA-1 field display no such significant shifts. The conclusion has been drawn that ECA produces a regulating influence on protein metabolism in hippocampal neurons depending on their functional state. 相似文献
7.
Methanol production resulting from the demethoxylation of lignin-related substances by Phanerochaete chrysosporium K-3 was studied in the presence or absence of glutamic acid in order to determine if methanol formation involved the ligninolytic system of the fungus. The general pattern was that methanol formation, calculated as percentage of theoretical yield, decreased in the order guaiacyl > syringyl > veratryl (3,4-dimethoxy) compounds. Methoxyhydroquinone and vanillic acid were most easily demethoxylated, while methanol production decreased with increasing molecular weight for the same type of structure (i.e. guaiacyl). Glutamic acid inhibited the demethoxylation of many of the compounds tested. The demethoxylation of the 4-methoxy group of veratric acid was particularly inhibited by glutamic acid suggesting a participation of the ligninolytic system, while the 3-methoxy group was influenced to a lesser extent.
The demethoxylating enzyme acting on lignin-related phenols is probably a peroxidase, while the identity of the enzyme demethoxylating dimethoxy compounds is not known with certainty, although a peroxidase type of enzyme reaction is anticipated also here. 相似文献
The demethoxylating enzyme acting on lignin-related phenols is probably a peroxidase, while the identity of the enzyme demethoxylating dimethoxy compounds is not known with certainty, although a peroxidase type of enzyme reaction is anticipated also here. 相似文献
8.
Competition between freshwater fish and goldeneyes Bucephala clangula (L.) for common prey 总被引:6,自引:0,他引:6
Mats O. G. Eriksson 《Oecologia》1979,41(1):99-107
9.
10.
Pernilla Christensen Frauke Ecke Per Sandström Mats Nilsson Birger Hörnfeldt 《Population Ecology》2008,50(2):169-179
There has been a long-term decline in spring and fall numbers of Clethrionomys rufocanus in boreal Sweden in 1971–2005. Previous studies on permanent sampling plots in the centre of 2.5 × 2.5 km landscapes suggested
that habitat fragmentation (sensu destruction) could have contributed to the decline. Therefore, we tested these findings
in a field study and compared trapping results on the central sampling plots of landscapes with a low degree of fragmentation
(LDF) and of “hot spot” type with trapping results in managed forest landscapes with a high degree of fragmentation (HDF).
We predicted that C. rufocanus would be more common on the LDF plots. We used our permanent plots supplemented with a new sample of plots, mainly of the
rare LDF type, inside or just outside the long-term study area. Very few voles were trapped on both plot types, and no difference
was found. However, a subsequent pilot study with trapping in a national park with large areas of pristine, unfragmented forest
yielded more voles than in the managed, more fragmented, areas. Consequently, the initial field study data and some other
recent data were also re-analysed from a “local patch quality” perspective. This alternative approach revealed the positive
importance of large focal patches of forest >60 years old and their content of old-growth (pine) forest (>100 years). Interestingly,
at the landscape level, the frequency distribution of patches of forest >60 years old, old-growth (>100 years), and especially
of old-growth pine forest (>100 years), relative to the properties of plots with C. rufocanus, suggested that there are few forest patches left that are suitable for C. rufocanus. Our current results suggest that habitat fragmentation cannot be excluded as a contributing cause to the long-term decline
of C. rufocanus in boreal Sweden. 相似文献