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971.
Recent advances in the understanding of polyamine functions during plant development 总被引:15,自引:0,他引:15
Suggested roles for polyamine function, and the evidence for these functions, is reviewed. These include membrane stabilization, free radical scavenging, effects on DNA, RNA and protein synthesis, effects on the activities of RNase, protease and other enzymes, the interaction with ethylene biosynthesis, and effects on second messengers. It is concluded that in addition to interacting with plant hormones, polyamines are able to modulate plant development through a fundamental mechanism(s) common to all living organisms.Abbreviations ACC
1-aminocyclopropane-1-carboxylic acid
- ADC
arginine decarboxylase
- Chl
chlorophyll
- DAP
diaminopropane
- DFMA
DL--difluoromethylarginine
- DFMO
DL--difluoromethylornithine
- PAs
polyamines
- Put
putrescine
- SAM
S-adenosylmethionine
- Spd
spermidine
- Spm
spermine 相似文献
972.
F. León-Velarde J. Sanchez A. X. Bigard A. Brunet C. Lesty C. Monge-C 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1993,163(1):52-58
Capillarity, fibre types, fibre area and enzyme activities of different skeletal muscles (pectoralis, extensor digitorum longus), tibialis anterior, plantaris and the myocardium were compared in Andean coot (Fulica americana peruviana) native to high altitude (Junín, Perú, 4200 m) and the same species nesting at sea level. Numbers of capillaries per square millimeter were higher in all high-altitude muscles when compared with sea-level muscles (P<0.0001). Moreover, values for capillaries per fibre and capillaries in contact with each fibre were higher in digitorum and tibialis high-altitude muscles. Muscle fibres were classified as Type I, Type IIA or Type IIB on the basis of their myofibrillar ATPase pH lability. Pectoralis muscle of high-altitude and sea-level coots presented only fibres of Type IIA. In contrast, all the leg muscles studied showed a mosaic pattern of the three fibre types. Fibre areas were determined using a Leitz Texture Analysis System. Significant differences in fibre area were observed (P<0.01) between high-altitude and sea-level muscles. Mean muscle fibre diameters were also lower in the high-altitude group than in the sea-level group. The enzyme activities studied were hexokinase, lactate dehydrogenase, citrate synthase and 3-hydroxyacyl-CoA-dehydrogenase. The oxidative capacity, as reflected by citrate synthetase and hydroxyacyl-CoA-dehydrogenase activities, was greater for myocardial and pectoralis than for leg muscles. However, analysis of maximal enzyme activities showed that there were no significant differences between the glycolytic and oxidative enzyme activities of high-altitude and sea-level coots. These results suggest that in Andean coots genetically adapted to high altitude, changes in muscle capillarity and fibre size, in addition to high haemoglobin O2 affinity and low haemoglobin concentration, are sufficient to allow adequate energy production without increases in enzymatic activities.Abbreviations BSA
bovine serum albumin
- C:F ratio
Capillaries per fibre
- CAF
Capillaries in contact with each fibre
- CD
capillary density (mm-2)
- CS
citrate synthetase
- EDL
muscularis digitorum longus
- fra
fraction reduction area
- HA
high altitude
- HAD
hydroxyacyl-CoA-dehydrogenase
- HK
hexokinase
- LDH
lactate dehydrogenase
-
P
50
PO2 at which hemoglobin is half saturated with O2
-
P
aO2
arterial partial pressure of oxygen
- PAS
periodic acid-schiff
- PEC
muscularis pectoralis
- PLA
muscularis planaris
-
P
tO2
mean tissue oxygen pressure
-
P
vO2
mixed venous partial pressure of oxygen
- SD
standard deviation
- SL
sea level
- TA
muscularis tibialis anterior
- TAS
texture analysis system 相似文献
973.
Laboratory and field studies were conducted to evaluate freezing as a control measure against Brennandania lambi (Krczal) which infests cultivated mushrooms (Agaricus bisporus) in Shanghai primarily through contaminated spawn. Laboratory experiments showed that exposure of contaminated spawn at -10° C for 24 h killed all stages of B. lambi. These mites probably died due to the freezing of body tissues during sustained exposure at -10° C for 24 h. because the supercooling points for the egg, active larva, quiescent larva, non-gravid adult and gravid adult of B. lambi were respectively -11.34, -10.96, -11.43, -7.65 and -11.20° C, whereas the freezing points were respectively -6.68, -6.84. -6.56, -3.96 and -6.75 °C. Semi-field experiments showed that compost inoculated with B. lambi-infested spawn that had been exposed at -10 °C for 24 h had no mite infestation during spawn running and thus mycelium growth was normal. Laboratory and field experiments during 1989 to spring 1990 showed that freezing spawn had no effect on mushroom yield. Further field experiments in two farms during fall 1990 showed no effect of freezing spawn on yield in one farm and increased yield in the other farm. A field experiment during 1991 to 1992 also indicated that freezing spawn -10 °C for 24 h to 34 h had no effect on mushroom yield. 相似文献
974.
Growth factors were studied as a means of increasing the development of in vitro matured (IVM) and in vitro fertilized (IVF) oocytes into morulae or blastocysts. Cell numbers of blastocysts were also counted. In Experiment 1, 2- to 8-cell embryos derived from bovine IVM/IVF oocytes were randomly allotted to one of 3 culture groups: a) synthetic oviduct fluid (SOF); b) SOF + 10 ng/ml epidermal growth factor (EGF); or c) SOF + 100 ng/ml EGF; all 3 culture media contained 10% fetal bovine serum. Culture resulted in 12%, 23% and 14% (P>0.05), respectively, developing into morulae and blastocysts. In Experiment 2, 5 ng/ml of transforming growth factor B (1) (TGFB (1)) added to CR(1aa) medium containing BSA increased the percentage of blastocysts to 56% vs 40% for the control (P<0.05). In Experiment 3, EGF and TGFB(1), added singly and in combination to CR(1aa) did not produce a synergistic effect. More embryos developed into morulae and blastocysts (45%) in a bovine oviduct epithelial co-culture than in any other treatment except in CR(1aa) + EGF (34%; P>0.05). In Experiment 4, 0, 1 and 5 ng/ml of platelet derived growth factor (PDGF) added to CR(1aa) yielded 39%, 70% and 52% morulae and blastocysts, respectively (P<0.05). Cell number was not increased, indicating that growth factors can increase the proportion of embryos that develop into morulae and blastocysts without an increase in the cell number. 相似文献
975.
Superovulated Holstein heifers (n = 32) were given a depot injection of 500 mg recombinant bovine somatotropin (rBST) or vehicle at Day 4 of the estrous cycle (7 days before the first FSH injection); at Day 11, coincidentally with the first FSH injection; or at Day 15, the time of artificial insemination. Embryos were collected nonsurgically, and the number of corpora lutea was counted by ultrasonography at Day 7 after insemination. Blood samples were taken every second day, from Day 2 of the superovulatory cycle until the day of embryo collection, and were analyzed for progesterone, somatotropin and insulin-like growth factor-1 (IGF-1). Somatotropin-treated heifers at Day 11 had a significantly higher mean number of corpora lutea than the controls (18.1 vs 13.4; P = 0.05). Day 4 treatment tended to increase the mean number of corpora lutea (15.4; P <- 0.10), and significantly increased the overall percentage of transferable embryos (74.6 vs 58.6%; P = 0.01). In the control animals, plasma IGF-1 was uncorrelated to somatotropin (P > 0.63), but it was negatively correlated with progesterone (P = 0.01), suggesting that IGF-1 production in the superovulated heifer may be related to ovarian development. 相似文献
976.
978.
The possibility of solving the mass balances to a multiplicity of substrates within a CSTR in the presence of a chemical reaction following Michaelis-Menten kinetics using the assumption that the discrete distribution of said substrates is well approximated by an equivalent continuous distribution on the molecular weight is explored. The applicability of such reasoning is tested with a convenient numerical example. In addition to providing the limiting behavior of the discrete formulation as the number of homologous substrates increases, the continuous formulation yields in general simpler functional forms for the final distribution of substrates than the discrete counterpart due to the recursive nature of the solution in the latter case.List of Symbols
C{N. M} mol/m3
concentration of substrate containing N monomer residues each with molecular weight M
-
{N, M}
normalized value of C{N. M}
-
C
{M} mol/m3 da
concentration of substrate of molecular weight M
-
in
normalized value of C
{M} at the i-th iteration of a finite difference method
-
{M}
normalized value of C
{M}
-
C
0{N.M} mol/m3
inlet concentration of substrate containing N monomer residues each with molecular weight M
-
{N ·M}
normalized value of C0{N. M}
-
0
i
normalized value of C
0
{M} at the i-th iteration of a finite difference method
-
C
0
{M} mol/m3
da initial concentration of substrate of molecular weight M
-
C
tot mol/m3
(constant) overall concentration of substrates (discrete model)
-
C
tot
mol/m3
(constant) overall concentration of substrates (continuous model)
-
D
deviation of the continuous approach relative to the discrete approach
-
i
dummy integer variable
-
I
arbitrary integration constant
-
j
dummy integer variable
-
k
dummy integer variable
-
K
m
mol/m3
Michaëlis-Menten constant for the substrates
-
l
dummy integer variable
-
M da
molecular weight of substrate
-
M
normalized value of M
-
M
da
maximum molecular weight of a reacting substrate
-
N
number of monomer residues of a reacting substrate
-
N
maximum number of monomer residues of a reacting substrate
-
N
total number of increments for the finite difference method
-
Q m3/s
volumetric flow rate of liquid through the reactor
-
S
inert product molecule
-
S
i
substrate containing i monomer residues
-
V m3
volume of the reactor
-
v
max mol/m3 s
reaction rate under saturating conditions of the enzyme active site with substrate
-
v
max{N. M} mol/m3 s
reaction rate under saturating conditions of the enzyme active site with substrate containing N monomer residues with molecular weight M
-
max{N · M}
dimensionless value of vmax{N. M} (discrete model)
-
max{M}
dimensionless value of v
max
{M} (continuous model)
-
mol/m3 s
molecular weight-averaged value of vmax (discrete model)
-
mol.da/m3s
molecular weight-averaged value of vmax (continuous model)
-
v
max
{M} mol.da/m3s
reaction rate under saturating conditions of the enzyme active site with substrate with molecular weight M
-
max
{M}
dimensionless value of vmax{M}
-
max, (i)
dimensionless value of vmax{M} at the i-th iteration of a finite difference method
-
v
max
mol/m3 s
reference constant value of v
max
Greek Symbols
dimensionless operating parameter (discrete distribution)
-
dimensionless operating parameter (continuous distribution)
-
M da
(average) molecular weight of a monomeric subunit
-
M
selected increment for the finite difference method
-
auxiliary corrective factor (discrete model) 相似文献
979.
Hong-Bin Zhang Gregory B. Martin Steven D. Tanksley Rod A. Wing 《Molecular genetics and genomics : MGG》1994,243(6):613-621
Constructs carrying the entire or part of the tobacco nitrate reductase cDNA (NIA) cloned between the promoter and terminator sequences of the 35S RNA of the cauliflower mosaic virus were introduced into tobacco, in an attempt to improve nitrate assimilation. Several transgenic plants that had elevated NIA mRNA and nitrate reductase (NR) activity were obtained. In addition, a few plants that exhibited a chlorotic phenotype characteristic of NR-deficient mutants were also obtained. One of these plants contained no NIA mRNA, no NR activity and accumulated nitrate. This phenotype was therefore assumed to result from co-suppression of 35S-NIA transgenes and host NIA genes. NR-deficient plants were also found among the progeny of transformants overexpressing NIA mRNA. Genetic analyses indicated that these NR-deficient plants were homozygous for the 35S-NIA transgene, although not all homozygous plants were deficient for NR. The ratio of normal to NR-deficient plants in the progeny of homozygous plants remained constant at each generation, irrespective of the state of expression of the NIA genes (active or inactive) in the previous generation. This ratio also remained unchanged when field trials were performed in two areas of France: Versailles and Bergerac. The analysis of homozygous plants revealed that co-suppression was reversible at some stage of sexual reproduction. Indeed, host genes and transgenes reactivated at each generation, and co-suppression always appeared after a lag period of normal growth, suggesting that the phenomenon is developmentaly regulated. We observed that the triggering of cosuppression was delayed when plants were initially grown under limited light and/or watered with limited nitrate supply (light and nitrate both being required for the expression of the host NIA genes). However, this delay did not affect the final ratio between normal and NR-deficient plants after transfer to nitrate-fertilized fields. Independent transformants exhibited either different co-suppression ratios or no co-suppression at all, irrespective of the transgene copy number, suggesting that genomic sequences surrounding the transgene might play a role in determining co-suppression. 相似文献
980.