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91.
Patterns of oxygen consumption, ammonia and urea excretion were monitored during late embryogenesis, i.e. 5 days before mass hatching and 12 days during the free-swimming stage of whitefish larvae, Coregonus lavaretus. Oxygen consumption increased from 1.31 to 2.53 mgO2 h−1 × 103 eggs−1 at hatching. Fasted, free-swimming larvae showed increasing oxygen consumption to the tenth day after hatching when it reached 5.52 mgO2 h−1 × 103 larvae−1 . Ammonia and urea excretion increased during pre-hatching period from 52.1 to 163.2 and 26.8 to 51.4 μgh−1 × 103 eggs−1 , respectively. The nitrogen excretion rate increased between the sixth and tenth day of fasting, i.e. for ammonia from 117.7 to 160.9 and for urea from 35.8 to 52.5 μg h−1 × 103 larvae−1 . Cumulative data on nitrogen and energy metabolism indicated that during late embryogenesis, and up to the fifth day after hatching, protein dominated in the energy expenditure. During the free swimming stage, the ratio of fat to protein in energy expenditure rose from 0.86 to 1.99. Combined data for several fish species indicated high dependance of oxygen uptake during the hatching period on egg size and temperature. 相似文献
92.
We investigated the capacity of ovaries of yellow perch to produce steroid hormones in vitro and the ovarian response to gonadotropin and phorbol ester during the annual reproductive cycle. The effects of photothermal manipulation on perch gonadal steroidogenesis and its regulation have also been examined. Initially, all females kept indoors were exposed to the same water temperature and photoperiod. By the end of August, following the first sampling, fish were submitted to different photothermal regimes. Group A was maintained under photothermal conditions characteristic for southern Ohio. Group B was submitted to a condensed light/temperature regime designed to accelerate physiological changes that depend on photothermal stimuli. In group A, basal in vitro production of ovarian estradiol (E2) was the highest in October and November, and hCG significantly stimulated E2 secretion during the entire period of vitellogenesis (October-January). In this group, the highest production of basal testosterone (T) was observed before spawning. hCG-stimulated production of T was highest at the beginning of vitellogenesis. Gonadotropin stimulated T production before spawning, a time when gonadotropin was unable to stimulate E2 production. Phorbol ester (PDBu) stimulated E2 and T production during vitellogenesis at the same time points as hCG did (E2: December, January; T: December). hCG-stimulated T production was not mimicked by PDBu in April. Condensing of the photothermal cycle resulted in diminished ovarian production of E2 during vitellogenesis. Moreover, the fish submitted to a condensed photothermal cycle demonstrated augmented T production during the postvitellogenic stage of ovarian development. Ovaries of group B did not respond to PDBu. Generally, the seasonal fluctuations in ovarian capacity to produce E2 and T as well as in gonadal responsiveness to gonadotropin observed in female yellow perch illustrate the dynamic nature of ovarian endocrine function. The lack of response to gonadotropin with regard to E2 production prior to spawning is not due to insensitivity to gonadotropin, but rather due to some deficiency in steroidogenesis (e.g. reduced aromatase activity). It appears also that ovarian steroidogenesis and its regulation are dependent on annual changes of photothermal conditions. 相似文献
93.
Molecular architecture of the ribosome‐bound Hepatitis C Virus internal ribosomal entry site RNA 下载免费PDF全文
Justus Loerke Jochen Ismer Andrea Schmidt Tarek Hilal Thiemo Sprink Kaori Yamamoto Thorsten Mielke Jörg Bürger Tanvir R Shaikh Marylena Dabrowski Peter W Hildebrand Patrick Scheerer Christian MT Spahn 《The EMBO journal》2015,34(24):3042-3058
Internal ribosomal entry sites (IRESs) are structured cis‐acting RNAs that drive an alternative, cap‐independent translation initiation pathway. They are used by many viruses to hijack the translational machinery of the host cell. IRESs facilitate translation initiation by recruiting and actively manipulating the eukaryotic ribosome using only a subset of canonical initiation factor and IRES transacting factors. Here we present cryo‐EM reconstructions of the ribosome 80S‐ and 40S‐bound Hepatitis C Virus (HCV) IRES. The presence of four subpopulations for the 80S•HCV IRES complex reveals dynamic conformational modes of the complex. At a global resolution of 3.9 Å for the most stable complex, a derived atomic model reveals a complex fold of the IRES RNA and molecular details of its interaction with the ribosome. The comparison of obtained structures explains how a modular architecture facilitates mRNA loading and tRNA binding to the P‐site. This information provides the structural foundation for understanding the mechanism of HCV IRES RNA‐driven translation initiation. 相似文献
94.
Ewa Maczynska Karol Karnowski Krzysztof Szulzycki Monika Malinowska Hubert Dolezyczek Artur Cichanski Maciej Wojtkowski Bartlomiej Kaluzny Ireneusz Grulkowski 《Journal of biophotonics》2019,12(2)
Application of the air‐puff swept source optical coherence tomography (SS‐OCT) instrument to determine the influence of viscoelasticity on the relation between overall the air‐puff force and corneal apex displacement of porcine corneas ex vivo is demonstrated. Simultaneous recording of time‐evolution of the tissue displacement and air pulse stimulus allows obtaining valuable information related in part to the mechanical properties of the cornea. A novel approach based on quantitative analysis of the corneal hysteresis of OCT data is presented. The corneal response to the air pulse is assessed for different well‐controlled intraocular pressure (IOP) levels and for the progression of cross‐linking‐induced stiffness of the cornea. Micrometer resolution, fast acquisition and noncontact character of the air‐puff SS‐OCT measurements have potential to improve the in vivo assessment of mechanical properties of the human corneas. 相似文献
95.
The pineal gland is involved in wound repair and collagen deposition in sponge-induced granulomas. The aim of this investigation was to discover whether the pineal gland was able to regulate collagen accumulation in the intact skin. Wistar rats were divided into five groups: control, sham-operated with vehicle application, sham-operated with melatonin injections (30 micrograms/100 g body wt), pinealectomized with vehicle, and pinealectomized with melatonin supplementation. After 8 weeks, the collagen content was estimated as hydroxyproline concentration in the dry tissue of the skin. The results showed that melatonin markedly (p < 0.001) reduced collagen accumulation in the skin. Pinealectomy enhanced collagen deposition in the skin (p < 0.02) and melatonin application reduced the pinealectomy-induced elevation of collagen content (p < 0.001). Results clearly indicate that collagen accumulation in the intact skin is under the control of the pineal gland, and that melatonin, the pineal hormone, is responsible for this control. 相似文献
96.
Total and regional blood flow was studied in femoral bone marrow of rats exposed to a short-term exhaustive exercise. The 10 micron microspheres labeled with 58Co were injected into femoral artery and the subsequent radioactivity yield was measured in 3 regions of the bone marrow (proximal metaphysis, diaphysis and distal metaphysis). Following exercise a rise of blood flow in the metaphyseal regions was accompanied by a fall in the diaphyseal area. The changes did not alter, however, the total blood flow rate in bone marrow which remained constant irrespective of the heavy exercise load. 相似文献
97.
S Moskalewski M Dabrowski A Hyc 《Folia histochemica et cytobiologica / Polish Academy of Sciences, Polish Histochemical and Cytochemical Society》1991,29(3):125-130
Bone cells isolated from the whole calvaria (2 x 10(6)) from either central or peripheral parts of parietal bones (1 x 10(6)) and from scapulas (2 x 10(6)) were allowed to adhere to devitalized calvarial bones in the number indicated in brackets and transplanted intramuscularly (supported transplants). Whole calvaria bone cells (2.4 or 8 x 10(6) cells per transplant) were also injected intramuscularly as free transplants. Calvarial cells produced solid bone islands with small intraosseous cavities, while bone formed by scapular cells contained large medullary spaces. The size of bone islands formed in transplants and the shortest distance between the neighbor islands were measured. The results of these measurements were similar in all groups of free transplants. The size of bone islands formed in supported transplants of cells from the whole calvaria or from central and peripheral parts of parietal bones was also roughly similar, but the shortest distance between islands was larger than in the free transplants. Furthermore, in these groups of transplants bone islands considerably larger than the largest islands in free transplants were present. Scapular bone cells formed islands much larger than those produced by calvarial cells. Bone islands formed by calvarial cells in free transplants were separated by bands of fibrous tissue which was absent in supported transplants. It appears that this tissue could limit growth and/or fusion of neighbor bone islands and in this manner influence their size. The population of transplanted scapular cells contained numerous stromal elements which could form an exclusion area inaccessible to local cells from the site of transplantation and thus favour formation of large bone islands within this area. 相似文献
98.
99.
Tomasz B. Owczarek Jaros?aw Suchanski Bartosz Pula Alicja M. Kmiecik Marek Chadalski Aleksandra Jethon Piotr Dziegiel Maciej Ugorski 《PloS one》2013,8(12)
It was recently proposed that UDP-galactose:ceramide galactosyltransferase (UGT8), enzyme responsible for synthesis of galactosylceramide (GalCer), is a significant index of tumor aggressiveness and a potential marker for the prognostic evaluation of lung metastases in breast cancer. To further reveal the role of UGT8 and GalCer in breast cancer progression, tumorigenicity and metastatic potential of control MDA-MB-231 cells (MDA/LUC) and MDA-MB-231 cells (MDA/LUC-shUGT8) with highly decreased expression of UGT8 and GalCer after stable expression of shRNA directed against UGT8 mRNA was studied in vivo in athymic nu/nu mice. Control MDA/LUC cells formed tumors and metastatic colonies much more efficiently in comparison to MDA/LUC-shUGT8 cells with suppressed synthesis of GalCer after their, respectively, orthotopic and intracardiac transplantation. These findings indicate that UGT8 and GalCer have a profound effect on tumorigenic and metastatic properties of breast cancer cells. In accordance with this finding, immunohistochemical staining of tumor specimens revealed that high expression of UGT8 accompanied by accumulation of GalCer in MDA-MB-231 cells is associated with a much higher proliferative index and a lower number of apoptotic cells in comparison to the MDA/LUC-shUGT8 cells. In addition, it was found that expression of UGT8 in MDA-MB-231 cells increased their resistance to apoptosis induced by doxorubicin in vitro. Therefore, these data suggest that accumulation of GalCer in tumor cells inhibits apoptosis, which would facilitates metastatic cells to survive in the hostile microenvironment of tumor in target organ. 相似文献
100.
David Corwin Clay Holdsworth Russell C. Rockne Andrew D. Trister Maciej M. Mrugala Jason K. Rockhill Robert D. Stewart Mark Phillips Kristin R. Swanson 《PloS one》2013,8(11)