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81.
用鸡胚细胞(CEC)和Madin-Darby Canine Kidney(MDCK)两个宿主细胞系统,检查甲型流感病毒各亚型不同时期流行株的温度敏感性状(ts),发现自然界存在许多宿主依赖的温度敏感性突变株(hd-ts)。它们在CEC上是ts,在MDCK上却是ts~ 。检出的hd-ts株中有些曾经过人体接种观察证明为减毒株。这表明在CEC中鉴定的ts表型与对人减毒性状密切相关。 相似文献
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83.
马立克氏病毒单克隆抗体的研究 总被引:1,自引:0,他引:1
获得了4株分泌马立克氏病毒(MDV)特异性单克隆抗体(McAb)的杂交瘤细胞:4BS10对MDV所有毒株呈阳性反应;4CN8 对MDV血清1,3型毒株发生反应;2BN90和4CN24只对MDV血清1型毒株有阳性反应。3个McAb属IgG1,1个为IgG2b,均不中和MDV,免疫扩散试验也无沉淀线。对禽白血病毒(ALV)无交叉反应。 以2BN90和辣根过氧化物酶、异硫氰酸荧光素的结合物进行直接酶联免疫吸附试验和直接荧光抗体试验,均获得成功。抗体滴度前者为1/51,200,后者为1/640。对ALV无交叉反应。 相似文献
84.
85.
乙型脑炎病毒减毒株(2-8株)和野毒株(SA14株)在生物学性质上有明显的不同,特别是嗜神经毒力方面,2-8株已丧失了对小白鼠、马,猴等敏感动物的脑内致病力。为了探讨这些生物学性质变化的物质基础,我们开展了乙脑强、弱毒株聚丙烯酰胺凝胶 相似文献
86.
Total cellular calcium content (determined by atomic absorption spectrometry) of Rat-1 cells transformed by temperature-sensitive Rous sarcoma virus decreases with cell density, but is found not significantly different at permissive and at non-permissive temperature. Kinetic analysis of 45Ca efflux from preloaded cells exhibits three separable pools of exchangeable calcium. The ratio of pool size of the fast-exchanging Ca-compartment (bound to cell surface) to pool size of the intermediate Ca-compartment (cytoplasmic) was found to decrease from 2.5 to 1.3 upon shift from non-permissive to permissive temperature. The slowly exchanging Ca-pool (presumably mitochondrial) did not change significantly upon temperature shift. These and further data demonstrate a close correlation between distribution of cellular Ca among different cellular compartments and characteristics of cellular proliferation, both attributable to the function(s) of a single oncogene. 相似文献
87.
A technique involving culture in soft agar was used for the assay of forward mutation of V79 cells to 6-thioguanine (6TG) resistance. The main reason for the use of soft agar was to prevent reduction in recovery of mutants depending on the cell density plated for mutation selection, which is the chief problem in the liquid method, and which results mainly from metabolic co-operation due to cell-to-cell contact.V79 cells grew well in fortified soft agar medium (DMEM + 20% FBS) showing cloning efficiencies (>80%) as high as in liquid culture. Therefore, V79/HGPRT mutagenesis could be assayed quantitatively in soft agar culture.The frequency of 6TG-resistant colonies in agar selective medium increased linearly with increase in concentration of EMS. Toxicity and mutagenic responses were greater in soft agar than in liquid culture.In cultures of untreated and EMS-treated cells, more than 95% of the 6TG-resistant colonies isolated were aminopterin-sensitive.Use of soft agar for selection prevented the reduction in the number of mutants with increase in the size of incula on plating up to 1?2 × 106 cells per 9-cm dish: in liquid culture, even with a lower plating number (2 × 105 cells per 9-cm dish), a notable reduction in numbers of mutants was observed. This character was re-examined in a reconstruction experiment. The results show that, when up to 2 × 106 cells were plated per 9-cm dish, 6TG-resistant cells were almost completely recovered from the soft agar medium, whereas only 10% were recovered from liquid culture. 相似文献
88.
Factors involved in the dissolution of polyhedra of Autographa californica nuclear polyhedrosis virus (AcNPV) by digestive fluid collected from fifth stage Trichoplusia ni larvae were studied in vitro. Observations were made at timed intervals using phase contrast microscopy and transmission electron microscopy. When digestive fluid was heated at 50°C proteases retained activity. Exposure of polyhedra to digestive fluid previously heated to 50°C resulted in polyhedral matrix dissolution and envelope disruption in a manner similar to that of unheated digestive fluid, only delayed slightly. After exposure of polyhedra for 3 min, only enveloped virons were observed. Heating the digestive fluid to 60° or higher inactivated the proteases and altered the effect on polyhedra. Dissolution of the occlusion body matrix occurred but the polyhedral envelope remained and only a few weakened areas were observed in its structure. Within the polyhedral envelope, enveloped virons were not observed, only nucleocapsids and capsids. Exposure of polyhedra to 0.1 m sodium carbonate buffer at pHs of 9.5 or higher had effects similar to those of the digestive fluid with heat (60°C)-inactivated proteases. The addition of trypsin and chymotrypsin to the 0.1 m sodium carbonate buffer had no effect, while the addition of a bacterial protease (Streptomyces griseus) at pHs of 9.5 or higher resulted in dissolution of the matrix and disruption of the polyhedral envelope like the digestive fluid. Material infectious to TN-368 cells was obtained by exposure of AcNPV to T. ni digestive fluid. Maximum infectivity resulted from a 5-min exposure to unheated digestive fluid, with a dramatic decrease in infectivity with longer exposure. Exposure to digestive fluid with heat (60°C)-inactivated proteases resulted in a slower release of infectious material from the occlusion body, with a steady increase in the level of infectivity throughout the 30-min digestion period. 相似文献
89.
Nonoccluded baculovirus-and filamentous virus-like particles were found in nuclei of hemocytes or midgut cells of field-collected spotted cucumber beetles. Each type of particle was associated with a different type of virogenic stroma containing various viral components similar to those referred to as capsid, nucleocapsid, viroplasm, and viral envelope in other known baculovirus infections. Nucleocapsids of the virus which occured only in hemocytes were rod-shaped particles approximately 230 nm long and 52 nm wide and were enveloped singly by a trilaminar unit membrane. Enveloped and partly enveloped particles appeared to be released from the nucleus to the cytoplasm by budding through the nuclear envelope acquiring additional membranes. The nucleocapsids of the virus which occurred only in nuclei of midgut cells were filamentous particles with an average diameter of 25 nm and variable length up to 2 μm. Some extremely long particles were bent almost 360° near the middle, resulting in a hairpin-like configuration. The particles were always enveloped singly. No particles budding through the nuclear envelope were observed. 相似文献
90.
The rabbit C family of short, interspersed repeats. Nucleotide sequence determination and transcriptional analysis 总被引:9,自引:0,他引:9
When the entire adeno-associated virus (AAV) genome is inserted into a bacterial plasmid, infectious AAV genomes can be rescued and replicated when the recombinant AAV-plasmid DNA is transfected into human 293 cells together with helper adenovirus particles. We have taken advantage of this experimental system to analyze the effects of several classes of mutations on replication of AAV DNA. We obtained AAV mutants by molecular cloning in bacterial plasmids of naturally occurring AAV variant or defective-interfering genomes. Each of these mutants contains a single internal deletion of AAV coding sequences. Also, some of these mutant-AAV plasmids have additional deletions of one or both AAV terminal palindromes introduced during constructions in vitro. We show here that AAV mutants containing internal deletions were defective for replicative form DNA replication (rep-) but could be complemented by intact wild-type AAV. This indicates that an AAV replication function, Rep, is required for normal AAV replication. Mutants in which both terminal palindromes were deleted (ori-) were also replication defective but were not complementable by wild-type AAV. The cis-dominance of the ori- mutation shows that the replication origin is comprised in part of the terminal palindrome. Deletion of only one terminal palindrome was phenotypically wild-type and allowed rescue and replication of AAV genomes in which the deleted region was regenerated apparently by an intramolecular correction mechanism. One model for this correction mechanism is proposed. An AAV ori- mutant also complemented replication of AAV rep- mutants as efficiently as did wild-type AAV. These studies also revealed an unexpected additional property of the deletion mutants in that monomeric single-stranded single-stranded DNA accumulated very inefficiently even though monomeric single-stranded DNA from the complementing wild-type AAV did accumulate. 相似文献