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51.
Summary A new case of ring chromosome 4 in a 2-day-old female child with multiple malformations is described. By means of the GTG-banding technique, a karyotype 46,XX,r(4), (p16q35) was determined. The characteristics of the child's karyotype and the relationship with the structure of the chromosome, especially the location of the deletion that produces the syndrome, are compared with previous reports.  相似文献   
52.
When exponentially growing KB cells were deprived of arginine, cell multiplication ceased after 12 h but viability was maintained throughout the experimental period (42-48 h). Although tritiated thymidine ([(3)H]TdR) incorporation into acid-insoluble material declined to 5 percent of the initial rate, the fraction of cells engaged in DNA synthesis, determined by autoradiography, remained constant throughout the starvation period and approximately equal to the synthesizing fraction in exponentially growing controls (40 percent). Continous [(3)H]TdR-labeling indicated that 80 percent of the arginine-starved cells incorporated (3)H at some time during a 48-h deprivation period. Thus, some cells ceased DNA synthesis, whereas some initially nonsynthesizing cells initiated DNA synthesis during starvation. Flow microfluorometric profiles of distribution of cellular DNA contents at the end of the starvation period indicated that essentially no cells had a 4c or G2 complement. If arginine was restored after 30 h of starvation, cultures resumed active, largely asynchronous division after a 16-h lag. Autoradiographs of metaphase figures from cultures continuously labeled with [(3)H]TdR after restoration indicated that all cells in the culture underwent DNA synthesis before dividing. It was concluded that the majority of cells in arginine-starved cultures are arrested in neither a normal G1 nor G2. It is proposed that for an exponential culture, i.e. from most positions in the cell cycle, inhibition of cell growth after arginine with withdrawal centers on the ability of cells to complete replication of their DNA.  相似文献   
53.
A survey of Guaymi Indians of Panama for the occurrence of genetic variants of 25 proteins of the erythrocytes and sera have revealed, in addition to seven well-known genetic polymorphisms, four rare variants and two "private polymorphisms," the latter involving erythrocyte acid phosphatase and lactate dehydrogenase. The significance of such private polymorphisms in tribal populations to the interpretation of rare variants in civilized populations is emphasized.  相似文献   
54.
Two strains ofAspergillus flavus Linkex Fr. and two strains ofA. parasiticus Speare were cultured on crushed moist wheat (Triticum durum var. Pané no. 247) for aflatoxin production studies in correlation with morphological changes. The toxicogenic strains were adapted to the substratum by means of successive transfers at regular intervals (72 h.)The amount aflatoxins synthesized by the toxicogenic strains decreased gradually after succesive subculturing. The decrease was accompanied by marked morphological changes. One of the strains studied,A. flavus NRRL 3251, lost completly the capacity of aflatoxin synthesis after several subcultures, presenting at the same time strong morphological variations.A. flavus CBS 120.62 also lost its toxicogenicity after six subcultures.  相似文献   
55.
Summary A polytrophic ovariole of the queen honeybee, Apis mellifera, is composed of a linear series of increasingly mature egg chambers, each consisting of an oocyte, an interconnected cluster of nurse cells, and a covering layer of follicle cells. This study describes changes in the volume of each of these components, as a function of the position of the egg chamber in the ovariole. An oocyte increases in volume from approximately 8.9 × 103 m3 to approximately 9.6 × 106 m3 over an average series of 20 egg chambers.  相似文献   
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A birefringence technique is used to determine the average magnetic moments <μ> of magnetotactic bacteria in culture. Differences in <μ> are noted between live and dead bacteria, as well as between normal density and high density samples of live bacteria.  相似文献   
58.
Mouse immune interferon (IFNγ) induced double-stranded RNA-independent protein kinase activity in the cytoplasmic fraction of mouse L cells as measured against a histone substrate. Chromatographic purification separated the activity into three distinct kinases of molecular weights of approximately 100K (kinase I), 70K (kinase II), and 70K (kinase III). Partially purified IFNγ was as effective as crude in inducing protein kinase activity. Induction was blocked by treatment of IFNγ with specific anti-IFNγ antibody or by treatment of the L cells with actinomycin D. Kinase II activity was different from that of kinases I and III in that it showed Ca-dependence in the absence of Mg2+, was inhibited in activity by the SH binding agent N-ethylmaleimide, and could use the cellular enzymes RNase A and hexokinase as substrates. The described protein kinases could play an important role in mediation of IFNγ effects, particularly where phosphorylated enzyme substrates were shown to have altered activity.  相似文献   
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60.
This study evaluates a DNA hybridization assay for salmonella with AttoPhos (JBL Scientific, San Luis Obispo, CA), a fluorescent substrate for alkaline phosphatase. The probe used (50 ng/ml) was a biotinylated 600 bp fragment consisting of a tandem repeat of an insertion sequence (IS200) found in most Salmonella spp. evaluated. The hybridization was carried out at 65 degrees C for 2 h without prior prehybridization and hybrids were detected by the addition of a streptavidin-alkaline phosphatase conjugate. Circles (5 mm) were cut from the membrane and placed in a cuvette containing 1 ml of 1 mmol/l AttoPhos. The reaction was evaluated after 30 min at 37 degrees C with a fluorometer with an excitation wavelength of 440 nm and an emission wavelength of 550 nm. The sensitivity of the probe was estimated to be 10,000 copies of target DNA or 5 x 10(-20) mol of DNA. All 74 salmonella strains tested reacted with the probe but none of the 98 heterologous species tested gave positive results. The results of this study indicate that our assay method, which employs a biotinylated tandem repeat of IS200 and AttoPhos, is a specific and highly sensitive quantitative method for the detection of salmonellas.  相似文献   
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