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971.
Sexual maturation was examined in underfed or amino acid-deficient rats. We have demonstrated a highly significant negative linear relationship (r = -0.80, P less than 0.001) between the age at puberty and the growth rate in rats under conditions of food restriction. The weight at puberty in animals growing at different rates because of undernutrition was not constant but behaved as a quadratic function of growth rate, as predicted from the assumption that growth rate was an independent variable. Growth rate is therefore more important than arrival at a particular fixed weight in determining the timing of puberty. Feeding of low valine diets resulted in delayed sexual maturation. Both the weight at vaginal opening (182 +/- 5.9 g) and the weight at first estrus (187 +/- 6.1 g) were significantly greater in the valine-deficient group when compared with growth-matched control (139 +/- 10.7 g and 161 +/- 9.3 g, respectively, P less than 0.05). The valine-deficient group also had significantly later vaginal opening (98.8+/- 4.7 days) than growth-matched controls (76.6 +/- 6.6 days, P less than 0.02). Valine deficiency seemed to have a specific effect on the hypothalamic-pituitary-gonadal axis since puberty in valine-deficient animals was delayed more than could be accounted for by impairment of growth. 相似文献
972.
A galactosidase immunosorbent test for human immunoglobulin E 总被引:1,自引:0,他引:1
We report here the development of a galactosidase-immunosorbent test (GIST) for immunoglobulin E (IgE) antibodies in which the amount of galactosidase adsorbed to a cellulose disc is a single valued function of IgE concentration in human serum. Rabbit anti-IgE immunoglobulin insolubilized on cellulose discs is incubated sequentially with human serum, sheep anti-IgE serum, and a covalent conjugate of rabbit antisheep immunoglobulin with the enzyme beta-D-galactoside galactohydrolase (E.C.) 3.2.1.23). Colorimetric assay of enzyme conjugate adsorbed to discs permits quantitation of 1.0 to 25 ng of IgE per test. Concentrations of IgE in 48 sera as measured by the GIST gave a linear correlation coefficient of 0.97 with IgE concentrations as determined by radioimmunoassay. Preliminary studies indicate that the GIST makes possible nonisotopic measurement of ragweed-specific IgE antibiotics in human serum. The GIST for IgE is simple to perform and requires neither short-lived radioisotopes, expensive scintillation detection equipment, nor scarce, purified IgE. 相似文献
973.
974.
A simple, inexpensive modification in the elevator mechanism of a liquid scintillation counter allows for radioimmunoassay tubes (12 X 75 mm) containing the antibody-bound radioligand to be counted directly, thereby obviating the need for counting vials and considerably decreasing the amount of fluor used. Furthermore, because assay and counting are all done in the same tube, the modification shortens assay time and increases precision by avoiding what is often the most time consuming and inaccurate step, the transfer of antibody-bound radioligand to a counting vial. We find that use of this modification results in about a 75% decrease in the overall cost for materials and a substantial decrease in assay time. 相似文献
975.
976.
977.
Children's behavior toward adults who differed from them along 2 dimensions was examined from a developmental perspective. A total of 80 White kindergartners and 4th graders were tested individually by either a Black or a White female adult who either was or was not seated in a wheelchair. Three kinds of behavior toward the adult were measured: physical distancing, imitation, and helping. On the basis of previous findings, it was predicted that children at both age levels would show more physical avoidance, less imitation, and less helping in the presence of other-race and handicap cues, as compared with own-race and nonhandicap cues. On all 3 types of behavior, the White E was favored over the Black E in both the wheelchair and nonwheelchair conditions. In addition, there were interaction effects involving race, handicap, age, and sex that suggest the operation of complex developmental processes in the formation of attitudes toward different types of stigmatized individuals. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
978.
Trained male Wistar albino rats (10 experimental and 9 control Ss) to barpress for food reinforcement in a 2-bar cyclic response chain situation. Responding on 1 bar led also to a punishment (footshock) on either an intermittent or constant schedule. Both punishment schedules led to increased responding on the nonpunished bar and to initial response suppression followed by recovery on the punished bar. For Ss on the intermittent schedule, the response increase on the nonpunished bar was seen only after a punishment on the other bar. Similar effects were found for transfer time between the 2 bars. The effects of punishment on response to both bars were more pronounced for the intermittent punishment groups. Results are discussed in terms of the motivational constructs of A. Amsel and of R. K. Banks. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
979.
The pressure-volume (PV) response of the opossum gallbladder was studied under basal conditions and after the continuous intravenous infusion of gastrin I, secretin, and cholecystokinin (CCK). The hormone effects were examined individually and in combination. The unstimulated gallbladder was capable of accommodating increases in intraluminal volume with only slight changes in intraluminal pressure. Cholecystokinin significantly increased the pressure recorded from the gallbladder. The pressure generated depended on the concentration of CCK and the intraluminal volume. Gastrin I had no independent effect on the PV response of the gallbladder but reduced the stimulatory affect of CCK. Secretin, alone, decreased the PV response of the gallbladder. Secretin also antagonized the stimulatory response to CCK. These findings suggest that the regulation of gallbaldder motor function and pressure generation exclusive of neural input, may depend on the interaction of CCK with gastrin and secretin and the intraluminal volume of the organ at the time of stimulation. 相似文献
980.
The general mechanism of martensitic nucleation by faulting from groups of existing dislocations, as proposed in Part I, is
applied to the fcc → bcc, bcc → fcc, bcc → hcp, and related transformations, including mechanical twinning. Where thermodynamic
data are available, the conditions at the observedM
s temperatures are consistent with nucleation from a defect composed of four or five properly spaced lattice dislocations.
Examples of nucleation by faulting on the planes predicted are found in published electron microscopy. The faults are observed
at the types of sites where the required dislocation groups are expected. These include grain boundaries, incoherent twin
boundaries, and inclusion particle interfaces. Having defined the function of a nucleation site, mechanisms of strain induced
nucleation and autocatalysis are then considered.
This paper is Part II of a three-part series based on a thesis submitted by G. B. Olson for the degree of Sc.D. in Metallurgy
at the Massachusetts Institute of Technology in June 1974. 相似文献