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991.
The effects of metabolic and protein synthesis inhibitors on NH4
+ uptake by Pisum arvense plants at low (0.05 mM) and high (1 mM) external ammonium concentration were studied. In short-time experiments cycloheximide
decreased the ammonium uptake rate at low level of NH4
+ and increased the absorption of NH4
+ from uptake medium containing high ammonium concentration. Arsenate and azide supplied into uptake solutions at low ammonium
concentration strongly decreased or completely suppressed the NH4
+ uptake rate, respectively. When the experiments were carried out at high level of ammonium only azide decreased the uptake
rate of NH4
+ and arsenate stimulated this process. Dinitrophenol very strongly repressed the uptake rate of NH4
+ at both ammonium concentrations. After removing dinitrophenol from both solutions, neither at low nor high external ammonium
level the recovery of NH4
+ uptake rate was achieved within 150 min or 3 h, respectively. The recovery of NH4
+ uptake rate after removing azide was observed within 90 min and 3 h at low and high ammonium concentrations, respectively.
The regulation of NH4
+ uptake by some inhibitors at low external ammonium level was investigated using plasma membrane vesicles isolated from roots
by two-phase partitioning. Orthovanadate completely suppressed the uptake of NH4
+ by vesicles and quinacrine decreased the NH4
+ uptake which 55 suggests that ammonium uptake depends on activities of plasma membrane-bound enzymes. On the other hand,
it was found that dinitrophenol completely reduced the NH4
+ uptake by vesicles.
The various effects of inhibitors on ammonium uptake dependent on external ammonium concentration suggest the action of different
ammonium transport systems in Pisum arvense roots. The ammonium transport into root cells at low NH4
+ level requires energy and synthesis of protein in the cytoplasm.
The research was supported by grant of KBN No. 6PO4C 068 08 相似文献
992.
Helona Havelková Marcela Kosařová Magdalena Krulová Peter Demant Marie Lipoldová 《Mammalian genome》1999,10(7):670-674
Lymphocytes of mouse strains BALB/cHeA (BALB/c) and STS/A (STS) differ in their response to CD3 antibody (anti-CD3). We analyzed
the genetic basis of this strain difference, using the Recombinant Congenic Strains (RCS) of the BALB/c-c-STS/Dem (CcS/Dem)
series. Each of the 20 CcS/Dem strains carries a different, random combination of 12.5% genes from the nonresponding strain
STS and 87.5% genes of the intermediate responder strain BALB/c. Differences in the magnitude of anti-CD3-induced response
among CcS/Dem strains indicated that in addition to Fcγ receptor 2 (Fcgr2) other genes are involved in the control of this response as well, and we have already mapped loci Tria1 (T cell receptor-induced activation 1), Tria2, and Tria3. In order to map additional Tria genes, we tested F2 hybrids between the high responder RC strain CcS-9 and the low responder strain CcS-11. Proliferation in complete RPMI medium
without anti-CD3 is controlled by locus Sprol1 (spontaneous proliferation 1) linked to the marker D4Mit23 on Chr 4. At concentration 0.375 μg/ml anti-CD3 mAb, the response was controlled by a locus Tria4, which maps to the marker D7Mit32 on Chr 7. The response to the higher concentration of mAb, 3 μg/ml, was controlled by Tria5, which mapped to the marker D9Mit15 on Chr 9. Anti-CD3 is being used for modulation of lymphocyte functions in transplantation reactions and in cancer treatment.
Study of mechanisms of action of different Tria loci could lead to better understanding of genetic regulation of these reactions.
Received: 28 October 1998 / Accepted: 17 March 1999 相似文献
993.
Ana Magdalena Hurtado Kristen Hawkes Kim Hill Hillard Kaplan 《Human ecology: an interdisciplinary journal》1985,13(1):1-28
Anthropologists have frequently proposed that sexual division of labor is produced by childcare constraints on women's subsistence work. We present data on the forest activities of Ache women that show that differences in parental investment partially account for variation in food acquisition among individual women. Data also suggest that childcare constraints are important in understanding the sexual division of labor. 相似文献
994.
995.
Streptomyces coelicolor DNA homologous with acyltransferase domains of type I polyketide synthase gene complex 总被引:1,自引:0,他引:1
Katarzyna Kuczek Krzysztof Pawlik Magdalena Kotowska Marian Mordarski 《FEMS microbiology letters》1997,157(1):195-200
An acyltransferase-homologous DNA fragment was amplified in a PCR reaction on a cosmid DNA template from the genomic DNA library of the soil bacterium Streptomyces coelicolor A3(2). The putative amino acid sequence of the fragment resembles acyl-CoA:ACP acyltransferase domains from several bacterial enzymatic complexes of polyketide synthase. There is a high similarity with acyltransferase domains from so-called type I polyketide synthases. Such synthases catalyze production of the aglycone portion of macrolides and polyethers that are important as antibiotics or immunosuppressants. The amplified fragment is considered to be a part of a larger gene complex. 相似文献
996.
997.
Magdalena Frańska Dobrochna Ginter-Kramarczyk Andrzej Szymański Tomasz Kozik Rafał Frański 《International biodeterioration & biodegradation》2009,63(8):1066-1069
Biodegradation of a commercially available mixture of octylphenol ethoxylates (Triton X-100) under the condition of OECD 301E screening test was studied by using electrospray ionisation mass spectrometry. It was found that ethoxylate containing six ethoxylene units (OPEO6) is more resistant to the biodegradation process than other ethoxylates (e.g. than OPEO5 and OPEO7). After 40 days of biodegradation process the signal of OPEO6 was clearly seen, but signals of OPEO5 and OPEO7 were not detected. After 40 days, all OPEOn with n > 4 were converted into carboxylated derivatives. Carboxylated derivatives were observed in negative ion mode as OPEOn-CH2COO? ions. Biodegradation of OPEO5-CH2COOH (carboxylated derivative correspondent of OPEO6) occurred slower than biodegradation of the others, as resulted from obtained ESI mass spectra. 相似文献
998.
Magdalena Endová Milena Masojidková Ivan Rosenberg 《Nucleosides, nucleotides & nucleic acids》2013,32(12):2151-2164
Abstract The use of (chloromethylene)diakylammonium chloride in selective transprotection of N-benzoylated nucleobase derivatives is reported along with the evaluation of the stability of various protecting groups widely used in nucleoside and/or nucleotide chemistry. 相似文献
999.
Sieprawska Apolonia Skórka Magdalena Bednarska-Kozakiewicz Elżbieta Niedojadło Katarzyna Janiak Agnieszka Telk Anna Filek Maria 《Plant and Soil》2021,461(1-2):389-405
Plant and Soil - As drought threatens the yield and quality of maize (Zea mays L.), it is important to dissect the molecular basis of maize drought tolerance. Flavonoids, participate in the... 相似文献
1000.