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71.
72.
73.
Crystal spectra of a heme and some heme-protein complexes 总被引:3,自引:0,他引:3
74.
Identification of hair and feather remains in the gut and faeces of stoats and weasels 总被引:10,自引:0,他引:10
M. G. Day 《Journal of Zoology》1966,148(2):201-217
Qualitative analysis of the gut and faeces contents of stoates and weasels is complicated by the lack of readily identifiable bone fragments, teeth, feathers, etc., of mammalian or avian prey. Often the only evidence of such prey was hair or feather fragments. Since the bulk of food taken by stoats and weasels was from these two food classes, the problem of qualitative analysis resolved itself into that of identifying these hair and feather fragments.
By using the scale pattern, cross-section and medulla type, it was possible to construct a key which would identify guard hairs of small mammals of the generic level. Feather identification was based on the structural variations to the down barbules of coverts. Using such criteria a key to the main bird orders was devised. 相似文献
By using the scale pattern, cross-section and medulla type, it was possible to construct a key which would identify guard hairs of small mammals of the generic level. Feather identification was based on the structural variations to the down barbules of coverts. Using such criteria a key to the main bird orders was devised. 相似文献
75.
76.
Growth-associated modifications of low-molecular-weight thiols and protein sulfhydryls in human bronchial fibroblasts 总被引:2,自引:0,他引:2
Luigi Atzori Jeannette M. Dypbukt Kristina Sundqvist Ian Cotgreave Charlotte C. Edman Peter Moldus Roland C. Grafstrm 《Journal of cellular physiology》1990,143(1):165-171
The thiol redox status of cultured human bronchial fibroblasts has been characterized at various growth conditions using thiol-reactive monobromobimane, with or without the combination of dithiotreitol, a strong reducing agent. This procedure has enabled measurement of the cellular content of reduced glutathione (GSH), total glutathione equivalents, cysteine, total cysteine equivalents, protein sulfhydryls, protein disulfides, and mixed disulfides. Passage of cells with trypsin perturbs the cellular thiol homeostasis and causes a 50% decrease in the GSH content, whereas the total cysteine content is subsequently increased severalfold during cell attachment. During subsequent culture, transient severalfold increased levels of GSH, protein-bound thiols, and protein disulfides are reached, whereas the total cysteine content gradually declines. These changes in the redox balance of both low-molecular-weight thiols and protein-bound thiols correlate with cell proliferation and mostly precede the major growth phase. When the onset of proliferation is inhibited by maintenance of cells in medium containing decreased amounts of serum, the GSH content remains significantly increased. Subsequent stimulation of growth by addition of serum results in decreased GSH levels at the onset of proliferation. In thiol-depleted medium, proliferation is also inhibited, whereas GSH levels are increased to a lesser extent than in complete medium. Exposure to buthionine sulfoximine inhibits growth, prevents GSH synthesis, and results in accumulation of total cysteine, protein-bound cysteine, and protein disulfides. For extracellular cystine, variable rates of cellular uptake correlate with the initial increase in the total cysteine content observed following subculture and with the GSH peak that precedes active proliferation. The results strongly suggest that specific fluctuations in the cellular redox balance of both free low-molecular-weight thiols and protein sulfhydryls are involved in growth regulation of normal human fibroblasts. 相似文献
77.
Summary The effect of cold soils on stem sap flow, shoot gas exchange and water potential of Picea engelmannii (Parry) was investigated during the snowmelt period in the Medicine Bow Mountains, Wyoming, USA. Shoot net photosynthetic rates were higher in young trees (1.5–1.8 m in height) growing in cold soils (<3.5° C) associated with snowpack, than trees in warm soils until about 1500 h. Higher shoot photosynthetic rates of trees in cold soils continued after snow was removed and could not be completely explained by higher visible irradiance over highly reflective snow. Following soil warming higher photosynthetic rates were evident in these trees for five days. High nutrient availability associated with snowmelt may improve shoot nutrient status leading to higher gas-exchange rates during snowmelt. Shoot conductance to water vapor was higher in trees in cold soil until midday, when declining shoot conductance led to lower intercellular CO2 concentrations. Midday through afternoon shoot water potentials of trees in cold soils were similar or higher than those of trees in warm soils and the lower afternoon shoot conductances in cold soils were not the result of lower bulk shoot water potentials. Decline in net photosynthesis of trees in cold soils at 1500 h paralleled increases in intercellular CO2 concentrations, implying a nonstomatal limitation of photosynthesis. This scenario occurred consistently in mid-afternoon following higher morning and midday photosynthesis in cold soils, suggesting a carbohydrate feedback inhibition of photosynthesis. Diurnal patterns in stem sap flow of all trees (cold and warm soils) reflected patterns of shoot conductance, although changes in stem sap flow lagged 1–3 h behind shoot conductance apparently due to stem water storage. Total daily stem sap flow was similar in trees in cold and warm soils, although diel patterns differed. The morning surge and night-time drop in sap flow commenced 1–2 h earlier in trees in cold soils. Overnight stem sap flow was lower in trees in cold soils, possibly due to higher resistance to root water uptake in cold soils, which may explain lower predawn shoot water potentials. However, midday shoot water potentials of trees in cold soils equalled or exceeded those of trees in warm soils. Higher resistance to root water uptake in P. engelmannii in cold soils was apparently overshadowed by transpirational forces and significant shoot water deficits did not develop. 相似文献
78.
Two experiments were conducted to study effects of cloprostenol sodium (cloprostenol) and clenbuterol HCl (clenbuterol) during postpartum anestrus on subsequent reproductive performance in cows. In Experiment I, 96 cows received either 0.5 mg cloprostenol (PGF, n = 25), 364 mg clenbuterol (CLEN, n = 24), 0.5 mg cloprostenol and 364 mg clenbuterol (CLEN+PGF, n = 21) or no treatment (Control, n = 26) on Day 20 post partum. Treatments failed to influence postpartum interval, pregnancy rate or the incidence of short estrous cycles preceding the first normal estrous cycle. In Experiment II, anestrous cows were administered cloprostenol (0.5 mg) on either Day 20 (PGF20, n = 27) or Day 35 post partum (PGF35, n = 25), or served as untreated controls (Control, n = 26). Neither postpartum interval nor pregnancy rate were affected by cloprostenol treatment. In conclusion, treatment of postpartum cows with PGF did not alter the resumption of normal estrous cycles following parturition. 相似文献
79.
W N Yunghans N J Karin K Ogborne T Desmond D J Morré R N Day S C Schiavi 《Biochemistry international》1990,21(2):377-385
Plasma membranes were purified from deciduoma of pseudopregnant rats and rat liver. Preparations contained 80% plasma membrane-derived material as based on electron microscope morphometry and analysis of enzyme markers. Several plasma membrane enzymes were tested for direct response to hormones. NADH-ferricyanide reductase of plasma membranes from both tissues was stimulated by glucagon and inhibited by insulin but was unresponsive to steroids. For steroids, responsiveness was limited to a reduction in NaF-stimulated adenylate cyclase activity by the steroid R5020. Thus, interaction of steroid hormones with plasma membranes, unlike that of glucagon and insulin, is not reflected in an altered activity of plasma membrane-bound dehydrogenases but may be exerted directly on adenylate cyclase. 相似文献
80.
Relationship between tumor necrosis factor alpha and feline immunodeficiency virus expressions. 下载免费PDF全文
L A Kraus W G Bradley R W Engelman K M Brown R A Good N K Day 《Journal of virology》1996,70(1):566-569
The presence of feline immunodeficiency virus (FIV) proviral DNA, expression of FIV p26 core protein, and production of tumor necrosis factor alpha (TNF-alpha) were assessed in sequential biopsies of spleen and lymph node sections, of mononuclear cells of the peripheral blood, and of the serum of specific-pathogen-free cats during the acute phase of FIV infection. A temporal relationship between TNF-alpha production and FIV p26 expression was noted. Two months following FIV infection, and preceding the detection of FIV viremia, levels of TNF-alpha in serum increased significantly (P = 0.04), and they remained elevated during FIV viremia in the third month postinfection. Immunoprecipitates representing expression of TNF-alpha and of FIV p26 were localized in common foci of lymph nodes of FIV-infected cats during this period of active viremia. With the advent of anti-FIV antibodies, circulating levels of TNF-alpha and p26 antigen and expression of TNF-alpha and p26 in the lymph nodes decreased during the fifth month postinfection, and p26 production became undetectable. With clearance of viremia, burden of proviral DNA in peripheral blood mononuclear cells became reduced (P = 0.041), with provirus remaining integrated principally within lymph nodes (P = 0.046). During aviremia, p26 expression was undetectable in any tissue but remained inducible in vitro. During acute FIV infection, TNF-alpha production and p26 expression are intimately linked. 相似文献