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41.
42.
Robert F. Whitcomb Frank E. French Joseph G. Tully Patricia Carle Roberta Henegar Kevin J. Hackett Gail E. Gasparich David L. Williamson 《Current microbiology》1997,35(5):287-293
Twenty-one triply cloned spiroplasma strains from the United States east of the Rocky Mountains, all isolated from tabanid
(Diptera:Tabanidae) flies or serologically related to strains from tabanids, were compared reciprocally by spiroplasma deformation
(DF) and metabolism inhibition (MI) serological tests. Many of the strains were also tested against 28 antisera representing
known spiroplasma groups, subgroups, and putative groups isolated from nontabanid hosts. Relationships among strains were
indicated by reciprocal cross-reactivity in both DF and MI tests. The strains were found to represent 11 recognized spiroplasma
groups or subgroups. On the basis of serological, biochemical, and genomic data, strain BARC 1901 from Tabanus lineola appeared to represent a previously unrecognized candidate group. Strain BARC 2649, also from T. lineola, also appeared to represent a new group, but its morphology, arginine utilization, and some one-way serological crossing
patterns suggested that it may be distantly related to group VIII spiroplasmas. Morphological, serological, and genomic data
were used to place tabanid spiroplasma strains into three informal clusters. These are (i) groups IV (strain B31) and XXXI
(strain HYOS-1); (ii) the three existing subgroups and a new candidate subgroup of group VIII represented by strain BARC 1357
plus ungrouped strain BARC 2649; and (iii) 14 strains, including EC-1 and TATS-1 (group XIV); strains TN-1 and TAAS-2 (group
XVIII); strains TG-1, TASS-1, and BARC 4689 (group XXIII), strains TALS-2 (group XXVII), strain TABS-2 (group XXXII), and
strains TAUS-1 and TABS-1 (group XXXIII) and ungrouped but closely related strains BARC 1901, BARC 2264 and BARC 2555. Analysis
of tabanids from other geographic regions probably will substantially increase the number of known spiroplasma groups from
this insect family.
Received: 23 April 1997 / Accepted: 31 May 1997 相似文献
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Brooke E. Crowley Sandra Thorén Emilienne Rasoazanabary Erin R. Vogel Meredith A. Barrett Sarah Zohdy Marina B. Blanco Keriann C. McGoogan Summer J. Arrigo‐Nelson Mitchell T. Irwin Patricia C. Wright Ute Radespiel Laurie R. Godfrey Paul L. Koch Nathaniel J. Dominy 《Journal of Biogeography》2011,38(11):2106-2121
Aim We sought to quantify geographical variation in the stable isotope values of mouse lemurs (Microcebus) and to determine whether this variation reflects trophic differences among populations or baseline isotopic differences among habitats. If the latter pattern is demonstrated, then Microcebus can become a proxy for tracking baseline habitat isotopic variability. Establishing such a baseline is crucial for identifying niche partitioning in modern and ancient communities. Location We studied five species of Microcebus from eight distinct habitats across Madagascar. Methods We compared isotopic variation in C3 plants and Microcebus fur within and among localities. We predicted that carbon and nitrogen isotope values of Microcebus should: (1) vary as a function of abiotic variables such as rainfall and temperature, and (2) covary with isotopic values in plants. We checked for trophic differences among Microcebus populations by comparing the average difference between mouse lemur and plant isotope values for each locality. We then used multiple regression models to explain spatial isotope variation in mouse lemurs, testing a suite of explanatory abiotic variables. Results We found substantial isotopic variation geographically. Ranges for mean isotope values were similar for both Microcebus and plants across localities (carbon 3.5–4.0‰; nitrogen 10.5–11.0‰). Mean mouse lemur and plant isotope values were lowest in cool, moist localities and highest in hot, dry localities. Rainfall explained 58% of the variation in Microcebus carbon isotope values, and mean plant nitrogen isotope values explained 99.7% of the variation in Microcebus nitrogen isotope values. Average differences between mouse lemur and plant isotope values (carbon 5.0‰; nitrogen 5.9‰) were similar across localities. Main conclusions Isotopic data suggest that trophic differences among Microcebus populations were small. Carbon isotope values in mouse lemurs were negatively correlated with rainfall. Nitrogen isotope values in Microcebus and plants covaried. Such findings suggest that nitrogen isotope values for Microcebus are a particularly good proxy for tracking baseline isotopic differences among habitats. Our results will facilitate future comparative research on modern mouse lemur communities, and ecological interpretations of extinct Holocene communities. 相似文献
46.
Robert A. Boomsma Patricia A. Mavrogianis Harold G. Verhage 《Journal of molecular histology》1997,29(6):495-504
This study was undertaken to determine the immunocytochemical localization of transforming growth factor α, epidermal growth
factor and epidermal growth factor receptor in the endometrium of ovariectomized cats treated with oestradiol-17β and/or progesterone
and in the endometrium and placenta of pregnant cats. Specific immunostaining was observed for all three antibodies. Moderate
immunostaining for transforming growth factor α was observed in the epithelium of ovariectomized and oestrogen-treated cats.
Dark epithelial staining was observed throughout pregnancy. The epithelial cells in progesterone-treated and peri-implantation
animals contained dense deposits of reaction product, which were not reduced in intensity when immunoabsorbed antiserum was
used. For epidermal growth factor, light--moderate epithelial staining was observed in ovariectomized and steroid-treated
animals, and this increased in pregnant cats. Stromal staining for both the transforming and the epidermal growth factors
was limited in steroid-treated animals and increased as pregnancy continued. Dark staining for epidermal growth factor receptor
was observed in the epithelium and stroma in all the animals studied. The tips of surface epithelial convolutions in the non-implantation
sites were always more darkly stained than in other regions of the surface epithelium. Staining in the placental trophoblast
was limited to the syncytiotrophoblast for the two growth factors and the cytotrophoblast for the receptor during most of
pregnancy and was absent late in pregnancy. The placental maternal giant cells contained specific immunoreactivity for all
the immunogens from the middle of pregnancy to term. This study demonstrates that the two growth factors and the epidermal
growth factor receptor are present in the endometrium and placenta of cats and suggests that these growth factors may play
an autocrine/paracrine role during reproduction 相似文献
47.
48.
A simple modification of nuclear staining after acid hydrolysis has been made which provides easy identification of quail nuclear markings in a chick-quail chimera. This method also improves the histologic detail normally seen with hematoxylin and eosin when compared to the more commonly used Feulgen reaction. Embryonic tissues can be fixed in Zenker's or Helly's solution and the sections obtained are hydrolyzed in acid (3.5 N HCl at 37 C for 40-50 min). After acid hydrolysis the sections are stained with hematoxylin and eosin rather than Schiff reagent and fast green. The interphase nuclei of chick cells show homogeneous or mottled purplish blue staining, while quail nuclei contain a dark blue spot. This staining corresponds to the reddish purple staining of the quail's heterochromatin seen adjacent to the nucleolus in the standard Feulgen stain. This new technique facilitates identification of quail cell types in the chick host and provides superior histology of the chick tissues by demonstrating cytoplasmic detail. 相似文献
49.
Structure of the mammalian kinetochore 总被引:27,自引:0,他引:27
The structure of the mammalian trilaminar kinetocnore was investigated using stereo electron microscopy of chromosomes in
hypotonie solutions which unraveled the chromosome but maintained microtubules. Mouse and Chinese hamster ovary cells were
arrested in Colcemid and allowed to reform microtubules after Colcemid was removed. Recovered cells were then swelled, lysed
or spread in hypotonic solutions which contained D2O to preserve microtubules. The chromosomes were observed in thin and thick sections and as whole mounts using high voltage
electron microscopy. Bundles of microtubules were seen directly attached to chromatin, indicating that the kinetochore outer
layer represents a differential arrangement of chromatin, continuous with the body of the chromosome. In cells fixed without
pretreatment, the outer layer could be seen to be composed of hairpin loops of chromatin stacked together to form a solid
layer. The hypotonically-induced unraveling of the outer layer was found to be reversible, and the typical 300 nm thick disk
reformed when cells were returned to isotonic solutions. Short microtubules, newly nucleated after Colcemid removal, were
found not to be attached to the kinetochore outer layer, but were situated in the fibrous corona on the external surface of
the outer layer. This was verified by observations of thick sections in stereo which made it possible to identify microtubule
ends within the section. Thus, kinetochore microtubules are nucleated within the fibrous corona, and subsequently become attached
to the outer layer.
We dedicate this paper to Wolfgang Beermann on the occasion of his 60th birthday in appreciation of many years of friendship
and his pioneering contributions in the field of chromosome biology 相似文献
50.
Ochratoxin A, a nephrotoxin produced as a secondary metabolite by A. ochraceus, is a potent inhibitor of renal PEPCK activity, in vivo. When fed orally to rats for 2 days, renal PEPCK activity is reduced 50% by a total dose of 0.3-0.5 mg toxin. Renal gluconeogenic capacity is reduced only after PEPCK activity is inhibited by 50%. Hepatic PEPCK activity is unaffected up to 1.5-2.0 mg ochratoxin A, which were the highest doses tested. Other enzymes located in proximal convoluted tubules, including phosphatedependent glutaminase, γ-glutamyl transpeptidase, pyruvate carboxylase, and Na,K-ATPase, are not affected. Renal protein synthesis from [3H]phenylalanine or [3H]leucine is inhibited 30–40% by ochratoxin A in vivo. By covalently coupling the toxin to albumin with carbodiimide or mixed anhydride, the inhibitory effect on renal PEPCK activity is retained, but protein synthesis is not affected and cytological evidence of nephrotoxicity is lost. Injection of the ochratoxin A-albumin carbodiimide complex results in a decrease of hepatic PEPCK activity as well. Removal of the phenylalanine group from the toxin prevents the in vivo inhibition of PEPCK activity, as well as protein synthesis. We conclude that the decrease in renal PEPCK activity, in vivo, requires the phenylalanine group of ochratoxin A, and occurs by a mechanism independent of the known nephrotoxicity effects. 相似文献