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21.
Of 25 commercial lipases, nine were able to catalyse the hydrolysis of ethyl D,L-2-amino-4-phenylbutyrate (D,L-APBAE) to optically active D-APBAE, an intermediate for the synthesis of inhibitors of angiotensin-converting enzyme, with specific selectivity ranging between 3.7 and 12.5. Optimal conditions for porcine pancrease lipase-catalyzed reaction gave a 68% conversion and the D-ester was obtained by a simple extraction with an optical purity of 98%. Saponification of the ethyl ester of D-APBA in 1 M NaOH gave the optically active D-APBA with a chemical purity greater than 99%. 相似文献
22.
The hydrolysis of sunflower oil using Candida cylindracea lipase in reversed micelles of AOT/isooctane was investigated. The
inhibition caused by substrate and hydrolysis products has been found in the process of reaction. It was revealed that the
extent of inhibition caused by oleic acid was higher than that caused by glycerol, and was much more serious in the case of
the mixture of hydrolysis products. Moreover, with the initial addition of glycerol into the reaction mixture, the stability
of lipase could be increased during the hydrolysis of sunflower oil in reversed micelles.
We thank the National Natural Science Foundation of China for the financial support of this work. We also thank Prof. Xu,
Jia-li for his contributions to this work. 相似文献
23.
MicroRNAs (miRNAs) regulate the progression of human malignancy by targeting oncogenes or tumor suppressors, which are 12 promising targets for cancer treatment. Increasing evidence has suggested the aberrant expression and tumor-suppressive function of miR-1298 in cancers, however, the regulatory mechanism of miR-1298 in breast cancer (BC) remains unclear. Here, our findings showed that miR-1298 was down-regulated in BC tissues and cell lines. Lower level of miR-1298 was significantly correlated with the advanced progression of BC patients. Experimental study showed that overexpression of miR-1298 inhibited the proliferation, induced apoptosis and cell cycle arrest in BC cells. The in vivo xenograft mice model showed that highly expressed miR-1298 significantly reduced the tumor growth and metastasis. Further mechanism analysis revealed that miR-1298 bound the 3′-untranslated region (UTR) of a disintegrin and metalloproteinase 9 domain (ADAM9) and suppressed the expression of ADAM9 in BC cells. ADAM9 was overexpressed in BC tissues and inversely correlated with miR-1298. Down-regulation of ADAM9 induced apoptosis and cell cycle arrest of BC cells. Moreover, ectopic expression of ADAM9 by transiently transfecting with vector encoding the full coding sequence of ADAM9 attenuated the inhibitory effects of miR-1298 on the proliferation and cell cycle progression of BC cells. Collectively, our results illustrated that miR-1298 played a suppressive role in regulating the phenotype of BC cells through directly repressing ADAM9, suggesting the potential application of miR-1298 in the therapy of BC. 相似文献
24.
The 231-residue capsid (CA) protein of human immunodeficiency virus type 1 (HIV-1) spontaneously self-assembles into tubes with a hexagonal lattice that is believed to mimic the surface lattice of conical capsid cores within intact virions. We report the results of solid-state nuclear magnetic resonance (NMR) measurements on HIV-1 CA tubes that provide new information regarding changes in molecular structure that accompany CA self-assembly, local dynamics within CA tubes, and possible mechanisms for the generation of lattice curvature. This information is contained in site-specific assignments of signals in two- and three-dimensional solid-state NMR spectra, conformation-dependent 15N and 13C NMR chemical shifts, detection of highly dynamic residues under solution NMR conditions, measurements of local variations in transverse spin relaxation rates of amide 1H nuclei, and quantitative measurements of site-specific 15N–15N dipole–dipole couplings. Our data show that most of the CA sequence is conformationally ordered and relatively rigid in tubular assemblies and that structures of the N-terminal domain (NTD) and the C-terminal domain (CTD) observed in solution are largely retained. However, specific segments, including the N-terminal β-hairpin, the cyclophilin A binding loop, the inter-domain linker, segments involved in intermolecular NTD–CTD interactions, and the C-terminal tail, have substantial static or dynamical disorder in tubular assemblies. Other segments, including the 310-helical segment in CTD, undergo clear conformational changes. Structural variations associated with curvature of the CA lattice appear to be localized in the inter-domain linker and intermolecular NTD–CTD interface, while structural variations within NTD hexamers, around local 3-fold symmetry axes, and in CTD–CTD dimerization interfaces are less significant. 相似文献
25.
Li-Yu Chen 《遗传学报》2018,45(3):121-123
正In flowering plants,the pollen grain generates a pollen tube to deliver two immotile sperm cells to the embryo sac for double fertilization.After landing on the stigma of the pistil,the pollen grain hydrates and germinates to produce a pollen tube,which penetrates the style and grows into the transmitting tract.The pollen tube then emerges onto the surface of the septum,grows along the funiculus,responds to the attraction signals from the synergid cells of the embryo sac and targets the ovule micropyle. 相似文献
26.
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28.
Spatial aspects of the interaction between the aphid host,Aphis gossypii, and its parasite,Allo-thrombium pulvinum larvae, on cotton plants were examined in seven fields in China. For both the host and the parasite, sample variance increased
with the mean according to Taylor's power law, which explained a substantial proportion (84–97%) of the variation in the data.
Although both the host and parasite showed aggregated distribution on cotton plants, the host aphids aggregated more strongly
than the parasites. The host dispersion pattern was not significantly affected by the presence of parasites. Increasing the
spatial scales of observation from individual plot to the entire field also had no significant effects on host and parasite
dispersion patterns. Parasites aggregated in cotton plants with higher aphid densities in five out of the seventeen samples.
Spatial patterns of parasitism were mostly host density-independent (71% of the samples) and sometimes inversely density-dependent
(29% of the sample). The processes underlying these patterns were discussed. 相似文献
29.
30.
Fenglei Chen Yujing Wang Qinguang Liu Jiahui Hu Jiaqi Jin Zhiyu Ma Jinlong Zhang 《Journal of cellular physiology》2020,235(7-8):5666-5678
ER oxidoreduclin 1α (ERO1α) is an oxidase, participating in formation of secretory and membrane proteins. However, the other physiological functions ERO1α is not well known. We found that ERO1α is high in the Leydig cells of the testis. Therefore, the purposes of the current study are to explore the role of ERO1α and the possible mechanisms in regulating cell proliferation, apoptosis, and testosterone secretion of Leydig cells. ERO1α was mainly localized in Leydig cells in the adult mice testes by immunofluorescence staining. Western blot analysis showed that ERO1α was higher in Leydig cells than that in the seminiferous tubules. The effect of ERO1α on cell proliferation, apoptosis, and testosterone secretion was detected by transducing ERO1α overexpression and knockdown lentiviruses into cultured primary Leydig cells (PLCs) together with hCG exposure. Flow cytometry analysis showed that ERO1α promoted cell proliferation by increasing cell distribution at the S phase and decreasing that at the G0/G1 phase. Western bolt analysis showed that ERO1α increased CDK2 and CDK6 expression. Cell apoptosis determination found that ERO1α inhibited PLC apoptosis. Western bolt analysis showed that ERO1α increased the ratio of BCL-2/BAX, and decreased BAD and Caspase-3 expression. Enzyme-linked immunosorbent assay analysis demonstrated that ERO1α enhanced testosterone secretion. Western bolt analysis found that ERO1α increased StAR, 3β-HSD, and CYP17A1 expression. Furthermore, ERO1α could activate the PI3K/AKT/mTOR signaling pathway. In summary, these results suggest that ERO1α might play proliferation promotion and antiapoptotic roles and enhance testosterone secretion in PLC, at least partly, via activation of the PI3K/AKT/mTOR signaling pathway. 相似文献