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991.
R. Stephen Lloyd Charles W. Haidle Donald L. Robberson Marion L. Dodson Jr. 《Current microbiology》1978,1(1):45-50
Bleomycin treatment of PM2 DNA results in fragmentation of the genome at several specific sites. Application of restriction
endonuclease digestion followed by bleomycin treatment has provided the basis for constructing a physical map of bleomycin
fragmentation sites. Eleven sites have been located on the physical map relative toHpa II,Pst I, andHindIII cleavage sites. The fragmentation sites are not clustered in a particular region of the PM2 genome but 3 of the 11 sites
do occur between theHpa II andPst I cleavage sites, a segment of DNA which comprises 14% of the PM2 DNA length. 相似文献
992.
The taxonomic validity, present distribution, and specific threats to the existence of the freshwater sponge, Anheteromeyenia biceps (Lindenschmidt, 1950) were investigated. The species, reported only from the type locality, Bessey Creek and Maple River, two streams flowing into Douglas Lake, Michigan, is relegated to synonomy with Ephydatia mülleri. Habitat data from Bessey Creek and Maple River, particularly physicochemical data, greatly extend the known environmental parameters of Heteromeyenia tubisperma and Ephydatia mülleri. 相似文献
993.
Dr. Marion D. Kendall 《Cell and tissue research》1979,199(1):63-74
The cortex of enlarging thymic lobes from adult haemorrhaged Quelea quelea were found to be similar to those of wild birds where the thymic enlargement was occurring naturally. A detailed stereological analysis of cells broadly designated as lymphoid, and the construction of models to account for the results, indicates that the enlarging thymic lobe contains both large and small blast cells, a heterogenous group of medium lymphocytes, erythroid cells, and two types of very small lymphocytes. The distinction between early erythroid cells and some lymphocytes, despite this detailed analysis is very difficult, but it is possible in enlarging thymic lobes that up to 42% of the lymphoid cells may have erythroid characteristics. 相似文献
994.
Summary The multiple molecular forms of selected lysosomal enzymes, as determined by analytical isoelectric focusing electrophoresis, from mucolipidosis II fibroblasts have a highly simplified pattern demonstrating a failure to undergo normal oligosaccharide processing. On the other hand, the multiple molecular forms of these same enzymes in mucolipidosis II sera and culture media are indistinguishable from controls. 相似文献
995.
Two specific ribonucleoprotein fragments from rat liver 60S ribosomal subunits 总被引:1,自引:0,他引:1
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K+-depleted 60S ribosomal subunits from rat liver were submitted to a mild treatment with ribonuclease T1. Ribonucleoprotein fragments could be separated on sucrose gradients only when the digested subunits were partially deproteinized with a high KCl concentration (0.6 M) which removed seven proteins more or less completely and 5S RNA. The RNA and protein content of each fragment has been characterized. The largest ribonucleoprotein enclosed two RNA fragments of about 950,000 and 750,000 daltons and all the salt-resistant proteins except L5. The smallest one enclosed protein L5 (with L11, L17 and L26 in small amounts) and a 67,000 RNA piece. The subsequent hydrolysis of the large ribonucleoprotein produced several other ribonucleoproteins. One of them has been fully characterized: it enclosed a 250,000 RNA fragment and protein L12 (with L11, L25 and L30 in smaller amounts). 相似文献
996.
The accessibility of 28S RNA within the ribosomal subunits to ribonuclease T1 was studied, in comparing results obtained after enzyme treatment of compact, K+ deficient 60S subunits and of EDTA-treated 60S subunits. RNA, extracted from the subunits, using a mixture of sodium dodecyl sulfate and phenol was analyzed on sucrose gradients. The RNA from active subunits was only degraded in high enzyme concentrations. In the K+ deficient subunits, RNA is more accessible since it breaks down into 6 well-defined fragments, sedimenting between 4S and 18.5S. Within the EDTA-subunits, there is no more protection of the RNA. In fact, it is degraded by weak enzyme concentrations, as is the free 28S RNA, giving heterogeneous fragments. Comparison of the melting curves of subunits and free 28S RNA showed that it is only in EDTA subunits that proteins do not stabilize the secondary structure of RNA. In the case of 40S subunits, the action of ribonuclease T1 combines with the action of the endogenous nuclease which makes the degradation process more difficult to analyze. 相似文献
997.
Detection of ischemia-reperfusion cardiac injury by cardiac muscle chemiluminescence 总被引:2,自引:0,他引:2
Kailash Prasad Paul Lee Subrahmanyam V. Mantha Jawahar Kalra Marion Prasad Jang B. Gupta 《Molecular and cellular biochemistry》1992,115(1):49-58
Various methods have been used in the past to assess the implication of oxygen free radicals (OFR) in ischemia-reperfusion-induced cardiac injury. Luminol-enhanced tert-butyl-initiated chemiluminescence in cardiac tissue reflects oxidative stress and is a very sensitive method. It was used to elucidate the role of OFR in cardiac injury due to ischemia and reperfusion. Studies were conducted on perfused isolated rabbit hearts in three groups (n = 8 in each): I, control; II, submitted to global ischemia for 30 min; III, submitted to ischemia for 30 min followed by reperfusion for 60 min. The heart tissue was then assayed for chemiluminescence (CL); content of malondialdehyde (MDA), an indicator of OFR-induced cardiac injury; and activity of tissue levels of antioxidants [superoxide dismutase (SOD), catalase, glutathione peroxidase (GSH-Px)].The control values for left and right ventricular CL and malondialdehyde were 81.1 ± 15.4 (S.E.) and 182.4 ± 50.3 (S.E.), mv-min-mg protein–1; and 0.024 ± 0.006 (S.E.) and 0.324 ± 0.005 (S.E.) nmoles-mg protein–1 respectively. Ischemia produced an increase in the cardiac CL (3.3 to 4.4 fold) and MDA content (2 to 2.6 fold). Reperfusion following ischemia also produced similar changes in CL and MDA content. The control values for activity of left ventricular SOD, catalase, and GSH-Px were 45.77 ± 1.73 (S.E.) U-mg protein–1 5.35 ± 0.51 (S.E.) K-10–3-sec–1-mg protein–1, and 77.50 ± 7.70 (S.E.) nmoles NADPH-min–1-mg protein–1 respectively. Activities of SOD and catalase decreased during ischemia but were similar to control values in ischemic-reperfused hearts. The GSH-Px activity of left ventricle was unaffected by ischemia, and ischemia-reperfusion. GSH-Px activity of the right ventricle increased with ischemia, and ischemic-reperfusion.These results indicate that cardiac tissue chemiluminescence would be a useful and sensitive tool for the detection of oxygen free radical-induced cardiac injury. 相似文献
998.
Marion T. E. Cornelissen Tom Bots Maarten A. Briët Maarten F. Jebbink Arie P. H. B. Struyk Jan G. van den Tweel Catherine E. Greer Henk L. Smits Jan ter Schegget 《Virchows Archiv. B, Cell pathology including molecular pathology》1992,62(1):167-171
By means of a consensus polymerase chain reaction (PCR) method, the prevalence of HPV types was determined in cervical biopsies
from 137 women referred to the gynecological outpatient clinic for colposcopy because of an abnormal cervical smear. The prevalence
of HPV was 80.3%. There was a statistically highly significant rise in the prevalence of the oncogenic HPV types (16, 18,
31, 33) with increasing severity of cervical intraepithelial neoplasia (CIN I to III), indicating a role for these HPV types
in the pathogenesis of cervical cancer. The prevalence of other HPV types decreased significantly with the severity of the
lesion, suggesting that these HPV types play a less significant role in this process. These data indicate that HPV typing
with PCR may be a valuable tool for distinguishing between highrisk and low-risk cervical lesions. Furthermore, our results
suggest that the detection of HPV types by consensus PCR in the cervix of patients with an abnormal smear but without histologically
detectable CIN is a useful tool for predicting which of these patiens will eventually develop CIN. Finally, a relatively low
percentage (3%) of HPV double infections is reported in this study. 相似文献
999.
Barbara Klughammer Marion Betz Roland Benzt Karl-Josef Dietz 《The Journal of membrane biology》1992,128(1):17-25
Summary A potassium-specific tonoplast channel was identified by reconstitution of tonoplast polypeptides into planar lipid bilayer membranes. Highly purified tonoplast membranes were solubilized in Triton X-100-containing buffer and fractionated by size-exclusion chromatography. The protein fractions were assayed for ion channel activity in a planar bilayer system, and the potassium channel was routinely recovered in specific fractions corresponding to an apparent molecular mass of 80 kDa. In symmetrical electrolyte solutions of 100 mM potassium chloride, the potassium channel had a single-channel conductance of 72 pS. Substates of the channel with conductances of 17, 33 and 52 pS were frequently observed. After identification of the channel in low or high KCl, addition of sodium acetate or sodium chloride caused only insignificant conductance changes. This result suggested that the channel was not or little permeable for sodium or chloride, whereas it had similar single-channel conductance for rubidium and caesium ions as compared with potassium ions. The channel is presumably responsible for the equilibration of potassium between the vacuole and the cytosol. The role of the channel in the physiology of the barley cell under salt stress is discussed.The authors would like to thank U. Heber for many helpful discussions. This work was supported by grants of the Deutsche Forschungsgemeinschaft (Sonderforschungsbereich 176, projects B3 and B7) and by the Fonds der Chemischen Industrie. 相似文献
1000.
Naturally occurring point mutation in the C terminus of the polymerase gene prevents duck hepatitis B virus RNA packaging.
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A duck hepatitis B virus (DHBV) genome cloned from a domestic duck from the People's Republic of China has been sequenced and exhibits no variation in sequences known to be important in viral replication or generation of gene products. Intrahepatic transfection of a dimer of this viral genome into ducklings did not result in viremia or any sign of virus infection, indicating that the genome was defective. Functional analysis of this mutant genome, performed by transfecting the DNA into a chicken hepatoma cell line capable of replicating wild-type virus, indicated that viral RNA is not encapsidated. However, virus core protein is made and can assemble into particles in the absence of encapsidation of viral nucleic acid. Using genetic approaches, it was determined that a change of cysteine to tyrosine in position 711 in the polymerase (P) gene C terminus led to this RNA-packaging defect. By site-directed mutagenesis, it was found that while substitution of Cys-711 with tryptophan also abolished packaging, substitution with methionine did not affect packaging or viral replication. Therefore, Cys-711, which is conserved in all published sequences of DHBV, may not be involved in a disulfide bridge structure essential to viral RNA packaging or replication. Our results, showing that a missense mutation in the region of the DHBV polymerase protein thought to be primarily the RNase H domain results in packaging deficiency, support the previous findings that multiple regions of the complex hepadnaviral polymerase protein may be required for viral RNA packaging. 相似文献