全文获取类型
收费全文 | 1894篇 |
免费 | 255篇 |
出版年
2021年 | 25篇 |
2018年 | 23篇 |
2016年 | 24篇 |
2015年 | 38篇 |
2014年 | 32篇 |
2013年 | 50篇 |
2012年 | 68篇 |
2011年 | 67篇 |
2010年 | 35篇 |
2009年 | 44篇 |
2008年 | 60篇 |
2007年 | 59篇 |
2006年 | 65篇 |
2005年 | 60篇 |
2004年 | 76篇 |
2003年 | 52篇 |
2002年 | 53篇 |
2001年 | 64篇 |
2000年 | 65篇 |
1999年 | 51篇 |
1998年 | 32篇 |
1997年 | 22篇 |
1996年 | 29篇 |
1995年 | 30篇 |
1994年 | 19篇 |
1993年 | 30篇 |
1992年 | 40篇 |
1991年 | 36篇 |
1990年 | 56篇 |
1989年 | 54篇 |
1988年 | 54篇 |
1987年 | 50篇 |
1986年 | 48篇 |
1985年 | 51篇 |
1984年 | 37篇 |
1983年 | 28篇 |
1982年 | 31篇 |
1981年 | 34篇 |
1980年 | 26篇 |
1979年 | 31篇 |
1978年 | 24篇 |
1977年 | 28篇 |
1976年 | 33篇 |
1975年 | 29篇 |
1974年 | 29篇 |
1973年 | 30篇 |
1972年 | 25篇 |
1971年 | 21篇 |
1970年 | 20篇 |
1968年 | 18篇 |
排序方式: 共有2149条查询结果,搜索用时 15 毫秒
81.
M L Nochomovitz M Goldman J Mitra N S Cherniack 《Journal of applied physiology (Bethesda, Md. : 1985)》1981,51(5):1150-1156
The effects of diaphragm paralysis on respiratory activity were assessed in 13 anesthetized, spontaneously breathing dogs studied in the supine position. Transient diaphragmatic paralysis was induced by bilateral phrenic nerve cooling. Respiratory activity was assessed from measurements of ventilation and from the moving time averages of electrical activity recorded from the intercostal muscles and the central end of the fifth cervical root of the phrenic nerve. The degree of diaphragm paralysis was evaluated from changes in transdiaphragmatic pressure and reflected in rib cage and abdominal displacements. Animals were studied both before and after vagotomy breathing O2, 3.5% CO2 in O2, or 7% CO2 in O2. In dogs with intact vagi, both peak and rate of rise of phrenic and inspiratory intercostal electrical activity increased progressively as transdiaphragmatic pressure fell. Tidal volume decreased and breathing frequency increased as a result of a shortening in expiratory time. Inspiratory time and ventilation were unchanged by diaphragm paralysis. These findings were the same whether O2 or CO2 in O2 was breathed. After vagotomy, no significant change in phrenic or inspiratory intercostal activity occurred with diaphragm paralysis in spite of increased arterial CO2 partial pressure. Ventilation and tidal volume decreased significantly, and respiratory timing was unchanged. These results suggest that mechanisms mediated by the vagus nerves account for the compensatory increase in respiratory electrical activity during transient diaphragm paralysis. That inspiratory time is unchanged by diaphragm paralysis whereas the rate or rise of phrenic nerve activity increases suggest that reflexes other than the Hering-Breuer reflex contribute to the increased respiratory response. 相似文献
82.
N. A. Buskard D. A. Galton J. M. Goldman E. M. Kohner C. F. Grindle D. L. Newman K. W. Twinn R. M. Lowenthal 《CMAJ》1977,117(2):135-137
Two patients with Waldenström''s macroglobulinemia (WM), which had become resistant to cytotoxic drugs, were treated for features of the hyperviscosity syndrome by repeated plasma exchange with the continuous-flow blood-cell separator over periods of 36 and 28 months, respectively. After four initial weekly plasma exchanges the procedure was carried out every 4 to 6 weeks and both patients tolerated it well. Relative viscosity of the serum was maintained within the normal range in one patient, and both patients remained free of symptoms of the hyperviscosity syndrome. The results suggest that treatment of WM by long-term "maintenance" plasma exchange alone should be considered in any patient with complications due to chemotherapy or whose disease fails to respond to chemotherapy. 相似文献
83.
The thermal transitions of rat liver microsomes and isolated lipids were investigated by using differential scanning calorimetry. Endothermic transitions at ≈?5°C and between ≈18° and 40°C were detected in the membranes and at ≈?10°C and between ≈10° and 20°C in the extracted lipids.Interaction with of microsomal membranes and of extracted lipids influences the thermotrophic behaviour as revealed by differential scanning calorimetry and eliminates the break in the Arrhenius plot of the enzymic activity of . 相似文献
84.
A S Spiers J M Goldman D Catovsky C Costello D A Galton C S Pitcher 《BMJ (Clinical research ed.)》1977,2(6086):544-547
Twenty-five patients with acute myeloid leukaemia were treated with three quadruple drug combinations in predetermined rotation: TRAP (thioguanine, daunorubicin, cytarabine, prednisolone); COAP (cyclophosphamide, vincristine, cytarabine, prednisolone); and POMP (prednisolone, vincristine, methotrexate, mercaptopurine). Fifteen patients (60%) achieved complete remission and five (20%) partial remission. For maintenance, five-day courses of drugs were administered every 14 to 21 days and doses were increased to tolerance. The median length of complete remission was 66 weeks. In eight patients remission maintenance treatment was discontinued and some remained in complete remission for over two years. In this series the remission induction rate was comparable with that reported for other regimens and complete remission lasted longer with this intensive maintenance regimen than with others. Nevertheless, the TRAP programme must still be regarded as only palliative treatment for acute myeloid leukaemia. 相似文献
85.
86.
The effect of free NH3 inhibition on short-term photosynthesis was investigated in three microalgal species: the freshwater chlorophyte Scenedesmus obliquus, the marine diatom Phaeodactylum tricornutum and the marine chlorophyte Dunaliella tertiolecta. By performing a series of assays at various concentrations of added NH4Cl and culture pH, we demonstrated that the inhibitory compound was free NH3 and that pH played no role in determining the magnitude of inhibition, other than in establishing the degree of dissociation of nontoxic NH4+ to toxic NH3. When corrections were made for pH, all three species displayed the same sigmoidal response curve to free NH3 concentration; 1.2 mM NH3 led to 50% reduction in photoassimilation of 14C. Based on literature values, some marine phytoplankton appear to be significantly more sensitive to free NH3 than were the test species, which are noted for their excellent growth characteristics. However, the combination of low algal biomass and strong pH buffering commonly found in most marine and many freshwater environments probably limits the possibilities for NH3 toxicity to low alkalinity freshwaters and intensive algal cultures in which NH4+ is the main source of N. Such conditions occur commonly in algal wastewater treatment systems. 相似文献
87.
Allan R. J. Eaglesham Mohamed H. Ahmad Salah Hassouna Barbara J. Goldman 《Applied microbiology》1982,44(3):611-618
During a program of screening rhizobia from West Africa, it was found that some strains produced nodules of unusually dark appearance on cowpeas, but not on peanuts, soybeans, pigeon peas, or mung beans. The dark pigmentation was in the bacteroid zone, was not correlated with nodule effectiveness, and was additional to the leghemoglobin pigment. Only rhizobial strains with a nongummy (“dry”) colony morphology produced dark nodules. Visually distinguishable pink and dark nodules formed on the same root when a mixture of pink and dark strains was applied as inoculum. The dark-nodule phenotype was therefore appraised as a marker and found to be useful for studying nodulation competition with strains of the orthodox pink-nodule type. The competitiveness of 10 pink-nodule strains was examined relative to a black-nodule strain, IRc 256; a range of competitiveness was obtained of less competitive than, equally competitive to, or more competitive than IRc 256. Patterns of primary (early) nodulation were generally the same as patterns of secondary (later) nodulation. Mixed infections by dark and pink strains produced piebald nodules, the frequency of occurrence of which was much greater among primary than among secondary nodules. 相似文献
88.
89.
The regulation of intermediate filament reorganization in mitosis. p34cdc2 phosphorylates vimentin at a unique N-terminal site 总被引:7,自引:0,他引:7
The disassembly of vimentin-containing intermediate filament (IF) networks during mitosis in BHK-21 cells is accompanied by increased phosphorylation of vimentin (Chou, Y.-H., Rosevear, E., and Goldman, R. D. (1989) Proc. Natl. Acad. Sci. U. S. A. 86, 1885-1889). We have recently identified p34cdc2 as the catalytic subunit of one of the two endogenous vimentin kinases in mitotic baby hamster kidney cells (Chou, Y.-H., Bischoff, J. R., Beach, D., and Goldman, R. D. (1990) Cell 62, 1063-1071). To begin to characterize the biochemical basis of the p34cdc2-mediated IF disassembly process, we have purified and sequenced the 32P-labeled tryptic peptides derived from in vitro-phosphorylated vimentin. The results demonstrate that Ser-55, in the N-terminal non-alpha-helical domain of vimentin, is the most favored phosphorylation site. This finding supports the idea that the N-terminal domain of type III IF protein plays a crucial role in regulating IF structure and supramolecular organization. 相似文献
90.
L S Reidl D F Friedman J Goldman R R Hardy L C Jefferies L E Silberstein 《Journal of immunology (Baltimore, Md. : 1950)》1991,147(10):3623-3631
Our laboratory has previously investigated the relationship of autoimmune disease and B cell neoplasia in a patient with a diffuse, well differentiated splenic B cell lymphoma and associated autoimmune hemolysis due to an anti-Pr2 antibody. EBV-immortalized B cell clones, established from this lymphoma, were shown to secrete the same pathologic anti-Pr2 antibody. The antiidiotypic mAb, RI.1, defined a private Id (IdRI.1) of the anti-Pr2 antibody that was related to the Ag-binding site and was expressed by both the lymphoma and derived cell lines. This unique Id was expressed by the majority of splenic tumor B cells and also was conserved over a period of 4 yr. In this report, the structural basis of IdRI.1 expression was investigated by analysis of Id- variants isolated by flow microfluorimetry using RI.1. Six Id- cell lines that secrete IgM kappa but lack Pr2 specificity were generated from an Id+ cell line, LS2. These lines were shown to be related to LS2 and the lymphoma by karyotype and by restriction fragment analysis of Ig gene rearrangements. Shared and unshared nucleotide substitutions in the VH and VL regions of the six independent clones were used to construct a genealogic tree relating the Id- clonal members to a common Id+ precursor. The tree illustrates that the base changes occurred sequentially, suggesting that they were introduced by somatic point mutation. Only one VH CDR3 bp difference from the LS2 nucleic acid sequence is common to all Id- sequences, resulting in an amino acid substitution of cysteine 108 to tyrosine. Taken together, these findings suggest that both the expression of IdRI.1 and Ag binding are affected by a single mutation localized to the D region of the anti-Pr2 antibody. 相似文献