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51.
Control of corneal differentiation by extracellular materials. Collagen as a promoter and stabilizer of epithelial stroma production 总被引:23,自引:0,他引:23
The primary stroma of the cornea of the chick embryo consists of orthogonally arranged collagen fibrils embedded in glycosaminoglycan (GAG) produced by the epithelium under the early inductive influence of the lens. The experiments reported here were designed to test whether or not the collagen of the lens basement lamina is capable of stimulating corneal epithelium to produce primary stroma. Enzymatically isolated 5-day-old corneal epithelia were grown for 24 hr in vitro in the presence of 35SO4 or proline-3H on various substrata. Epithelia cultured on lens capsule synthesized 2.5 times as much GAG (as measured by incorporation of label into CPC precipitable material) and almost 3 times as much collagen (assayed by hot TCA extraction or collagenase sensitivity) as when cultured on Millipore filter or other noncollagenous substrata. A similar stimulatory response was observed when epithelium was combined with chemically pure chondrosarcoma collagen, NaOH-extracted lens capsule, vitreous humor, frozen-killed corneal stroma or cartilage, or tendon collagen gels; in the latter case, the magnitude of the effect can be shown to be related to concentration of the collagen in the gel. All of the collagenous substrata stimulate not only extracellular matrix production, but also polymerization of corneal-type matrix, as judged by ultrastructural criteria and by the association of more radioactivity with the tissue than the medium. Since purified chondrosarcoma collagen is as effective as lens capsule, the stimulatory effect on collagen and GAG synthesis by corneal epithelium is not specific for basal lamina (lens capsule) collagen. 相似文献
52.
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54.
Integration is not necessary for expression of human immunodeficiency virus type 1 protein products. 总被引:38,自引:23,他引:15 下载免费PDF全文
M Stevenson S Haggerty C A Lamonica C M Meier S K Welch A J Wasiak 《Journal of virology》1990,64(5):2421-2425
A common feature in the life cycle of cytocidal retroviruses, including human immunodeficiency virus type 1 (HIV-1), is the accumulation of large amounts of unintegrated viral DNA. As yet, the role of unintegrated viral DNA in the cytopathogenesis of cytocidal retrovirus infections remains unresolved. HIV-1 mutants which were deleted in the integrase/endonuclease gene and which were unable to establish an integrated form of the virus were constructed. Despite an inability to integrate, these mutants were fully competent templates for HIV-1 core and envelope antigen production. HIV-1 antigen could be detected in the supernatants of lymphocyte cultures infected with HIV-1 integrase mutants. However, an inability to rescue infectious virus from these cultures indicated that HIV-1 integration was required for the production of infectious HIV-1. On the basis of the ability of unintegrated HIV-1 DNA to serve as a template for HIV-1 antigen production, it is plausible that unintegrated viral DNA can contribute to the HIV-1 antigen pool during HIV-1 replication. 相似文献
55.
Cloning and characterization of human immunodeficiency virus type 1 variants diminished in the ability to induce syncytium-independent cytolysis. 总被引:7,自引:5,他引:2 下载免费PDF全文
M Stevenson S Haggerty C Lamonica A M Mann C Meier A Wasiak 《Journal of virology》1990,64(8):3792-3803
The phenomenon of interference was exploited to isolate low-abundance noncytopathic human immunodeficiency virus type 1 (HIV-1) variants from a primary HIV-1 isolate from an asymptomatic HIV-1-seropositive hemophiliac. Successive rounds of virus infection of a cytolysis-susceptible CD4+ cell line and isolation of surviving cells resulted in selective amplification of an HIV-1 variant reduced in the ability to induce cytolysis. The presence of a PvuII polymorphism facilitated subsequent amplification and cloning of cytopathic and noncytopathic HIV-1 variants from the primary isolate. Cloned virus stocks from cytopathic and noncytopathic variants exhibited similar replication kinetics, infectivity, and syncytium induction in susceptible host cells. The noncytopathic HIV-1 variant was unable, however, to induce single-cell killing in susceptible host cells. Construction of viral hybrids in which regions of cytopathic and noncytopathic variants were exchanged indicated that determinants for the noncytopathic phenotype map to the envelope glycoprotein. Sequence analysis of the envelope coding regions indicated the absence of two highly conserved N-linked glycosylation sites in the noncytopathic HIV-1 variant, which accompanied differences in processing of precursor gp160 envelope glycoprotein. These results demonstrate that determinants for syncytium-independent single-cell killing are located within the envelope glycoprotein and suggest that single-cell killing is profoundly influenced by alterations in envelope sequence which affect posttranslational processing of HIV-1 envelope glycoprotein within the infected cell. 相似文献
56.
[3H]Glutamate uptake into astrocytes in primary culture was potently inhibited by the aspartate analoguesl- andd-aspartic acid,Dl-threo--hydroxy-aspartic acid,l-aspartic acid--hydroxymate (IC50's: 136, 259, 168, and 560 M, respectively) and by -Dl-methylene-aspartate, a suicide inhibitor of asparate aminotransferase (IC50: 524 M), and by the endogenous sulphur-containing amino acidl-cysteinesulfinic acid (IC50: 114 M). [3H]Glutamate uptake was not significantly affected by either N-methyl-d-aspartate orDl-homocysteine thiolactone. These results demonstrate that other excitatory amino acids including aspartate andl-cysteinesulfinic acid (but excludingl-homocysteic acid) interact with the glutamate transport system of astrocytes. Inhibition of glutamate uptake may significantly increase the level of neuronal excitability. 相似文献
57.
B. Meier 《Human Evolution》1989,4(2-3):223-229
Extinction of small, closed populations in captivity as well as in the wild is believed to be nearly inevitable, because inbreeding
will adversely effect reproductive success, mortality, sex ratio and also the susceptibility to epidemic diseases and environmental
stress. An ever increasing number of primate species exist only in small isolated populations, which contain only a part of
the original genetic variability. In captive breeding programs research about genetic management strategies is, therefore,
of essential importance. In 1980 we imported 9Loris tardigrdus nordicus (4 females, 5 males) from NE-Sri Lanka. The founders came from one natural breeding population. All sexual mature females
are breeding. Up to now the colony contains 36 living individuals. The main goal of our long-term genetic management plan
was to minimize inbreeding and to preserve the genetic diversity. Therefore, we try to pass the founder bottleneck rapidly
by enlarging the population to a desired minimum population size of 25 pairs and to equalize the founder representation within
any generation. The need to control the spread of sublethal genes, introduced by one of the founders, conflicts directly with
the aim of equalizing the founder representation. A solution of this problem is discussed. To produce a sufficiently large
population we intend to give animals to other institutions and to build up an exchange-system for offspring individuals, which
should lead to an international studbook. 相似文献
58.
M Repetto J C Maziere D Citadelle R Dupuis M Meier S Biade D Quiec C Roux 《Teratology》1990,42(6):611-618
AY 9944 [trans-1,4-bis(2-chlorobenzylaminomethyl) cyclohexane dihydrochloride] is an amphiphilic cationic molecule. This chemical is an established inhibitor of cholesterol synthesis and is teratogenic in rats. The mechanisms of this teratogenicity remain to be clarified. This study used cultured rat whole embryos to ascertain whether AY 9944 had a direct effect on embryos, or whether its action was indirect, via the maternal cholesterol metabolism. Four experimental conditions were investigated: (A) controls; (B) 10 day untreated embryos were cultured in serum of treated rats; (C) 10 day untreated embryos were cultured in serum containing added AY 9944 (0-1,000 micrograms/ml); and (D) 10 day embryos from females treated on day 4 of gestation were cultured in normal serum. In group B there was no growth retardation; some slight nonspecific abnormalities were not significant. In group C, direct addition of AY 9944 to culture medium retarded growth and differentiation in a dose-dependent manner. No malformation was observed, but histological examinations showed numerous areas of cell necrosis, especially in the CNS. In group D, not only was growth retardation observed, but also characteristic malformations of AY 9944 teratogenesis, including pituitary agenesis. These results show that AY 9944 teratogenicity is initiated prior to day 10. 相似文献
59.
Mice bearing the H-2
bhaplotype are susceptible to the development of experimental autoimmune myasthenia gravis (EAMG), induced by acetylcholine receptor (AChR) autoimmunity. One of the genes influencing EAMG susceptibility has been mapped to the A
blocus of the major histocompatibility complex, and the A chain has been implicated in the pathogenesis. Mice of the H-2
bhaplotype, including C57BL/10 (B10), have a genomic deletion of the E
gene and therefore fail to express the E molecule on their cell surface. To test the hypothesis that failure to express the cell surface E molecule in B10 mice contributes to EAMG pathogenesis, E
inf
supk
transgenic B10 mice expressing the T molecule were examined. Expression of the E molecule in E
inf
supk
transgenic B10 mice partially prevented the development of EAMG. 相似文献
60.
Dr. Edward B. Blanchard Peter J. Cornish David A. Wittrock Steve Fahrion 《Applied psychophysiology and biofeedback》1990,15(2):145-159
Reports of subjective experiences of 73 hypertensive patients who were treated with thermal biofeedback for hand warming were obtained over 16 treatment sessions. Most of the differential responding in subjective report occurred in the first 5 sessions. Differences in reports of throbbing were associated with medication status during treatment (presence of sympatholytic antihypertensive agent). From 4 to 9% of patients report negative subjective experiences at any one session. When short-term clinical successes (either elimination of medication or reduction of BP) were compared with short-term failures, it was found that successes reported more warmth, more likelihood of falling asleep, and more dreamlike experiences. The latter were more likely to occur suddenly for the successes. Correlational analyses revealed consistent positive associations between reports of warmth and relaxation with highest temperature achieved in the session and consistent negative associations between experiencing physical sensations and degree of temperature change within the session.This research was supported in part by grants from NHLBI, HL-27622 and HL-31189. 相似文献