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921.
补肾益气活血方对胎儿宫内生长迟缓胎盘组织一氧化氮合酶活性的影响 总被引:6,自引:0,他引:6
为了探讨补肾益气活血方对胎儿宫内生长迟缓(IUGR)胎盘组织一氧化氮(NO)生成的影响,本文对正常孕妇、IUGR患者及补肾益气活血中药治疗后患者各12例,采用NADPH黄递酶法研究了一氧化氮合酶(NOS)在胎盘组织的分布,应用化学发光法测定胎盘组织NOS活性。结果表明:正常孕妇胎盘绒毛合体滋养层细胞NOS呈强阳性反应,绒毛干血管壁呈阳性反应,终末绒毛毛细血管壁呈阴性反应;IUGR患者绒毛合体滋养层细胞和绒毛干血管壁NOS染色明显变浅,而终末绒毛毛细血管壁呈阳性反应;中药治疗后合体滋养层细胞和绒毛干血管壁NOS染色明显加深。NOS活性测定中药组较IUGR未治疗组显著增高,与正常孕妇相比其差异无显著性。结果提示:NO参与IUGR的病理生理过程,补肾益气活血方通过增强NOS活性促进胎盘组织NO的产生 相似文献
922.
白介素-2(IL-2)广泛用于治疗恶性肿瘤,由于大剂量可引起严重的低血压且机制不明,限制了其大剂量的使用。本研究用国产重组人白介素-2(rhIL-2)复制大鼠低血压模型并探讨其机制。24只wistar大鼠随机分成3组(每组n=8):正常对照组,IL-2实验组(rhIL-2)和氨基胍(AG)治疗组。结果显示:(1)IL-2可使大鼠提睾肌微动脉扩张及MAP下降,肺、肾、肝组织Evan′sBlue含量明显增加。(2)AG可使rhIL-2引起的低血压回升及微动脉缩小,肺组织Evan′sBlue含量明显下降。提示:rhIL-2引起低血压,可能与IL-2诱导NO产生,使血管扩张及通透性增加有关。 相似文献
923.
离子注入不同辐射敏感性微生物自由基与存活关系的研究 总被引:9,自引:0,他引:9
以不同辐射敏感性微生物辐射异常微球菌和大肠杆菌为试材,用电子自旋共振波谱法研究了离子注入后在两种微生物细胞内产生的自由基及其存活的关系。 相似文献
924.
Kathleen Duncan Eleanor Jennings Susan Hettenbach William Potter Kerry Sublette Ganesh Subramaniam Ramesh Narasimhan 《Bioremediation Journal》1998,1(3):195-208
A remote site in the Tallgrass Prairie Preserve of Oklahoma (The Nature Conservancy) was contaminated with crude oil from a pipeline break and is being bioremediated using landfarming techniques. Landfarming is designed to stimulate microbial-based catabolism of petroleum through combined dilution/mixing and fertilization-based effects. To evaluate nitrogen-based effects during remediation, the site was sectioned and treated with urea, ammonium sulfate, or ammonium nitrate. Samples were obtained from prairie soil without chemical nitrogen addition and with or without hydrocarbon contamination. Nitrogen cycling dynamics were followed by measuring ammonium, nitrite, nitrate, and volatile nitric oxide (NOx) levels. Nitrifying and denitrifying bacterial numbers were estimated and compared to soil oxygen, carbon dioxide, and methane levels as well as to overall total petroleum hydrocarbon (TPH) reduction. For a prairie ecosystem of this type, a high level of fertilization, particularly with nitrogen, can have ecological effects almost as profound as the petroleum contamination itself. Fertilization of the oil-contaminated soil with the reduced and/or oxidized forms of nitrogen quickly resulted in elevated steady-state levels of both ammonium and nitrate, and exceptionally high levels of NOx released from soil. Although nitrogen fertilization increased microbial nitrogen metabolism and nitrogen cycling, it had minimal effects on the overall remediation efficiency. 相似文献
925.
The availability of O2 is believed to be one of the main factors regulating nitrification and denitrification and the release of NO and N2O. The availability of O2 in soil is controlled by the O2 partial pressure in the gas phase and by the moisture content in the soil. Therefore, we investigated the influence of O2 partial pressures and soil moisture contents on the NO and N2O release in a sandy and a loamy silt and differentiated between nitrification and denitrification by selective inhibition of nitrification with 10 Pa acetylene. At 60% whc (maximum water holding capacity) NO and N2O release by denitrification increased with decreasing O2 partial pressure and reached a maximum under anoxic conditions. Under anoxic conditions NO and N2O were only released by denitrification. NO and N2O release by nitrification also increased with decreasing O2 partial pressure, but reached a maximum at 0.1–0.5% O2 and then decreased again. Nitrification was the main source of NO and N2O at O2 partial pressures higher than 0.1–0.5% O2. At lower O2 partial pressures denitrification was the main source of NO and N2O. With decreasing O2 partial pressure N2O release increased more than NO release, indicating that the N2O release was more sensitive against O2 than the NO release. At ambient O2 partial pressure (20.5% O2) NO and N2O release by denitrification increased with increasing soil moisture content. The maximum NO and N2O release was observed at soil moisture contents of 65–80% whc and 100% whc, respectively. NO and N2O release by nitrification also increased with increasing soil moisture content with a maximum at 45–55% whc and 90% whc, respectively. Nitrification was the main source of NO and N2O at soil moisture contents lower than 90% whc and 80% whc, respectively. Higher soil moisture contents favoured NO and N2O release by denitrification. Soil texture had also an effect on the release of NO and N2O. The coarse-textured sandy silt released more NO than N2O compared with the fine-textured loamy silt. At high soil moisture contents (80–100% whc) the fine-textured soil showed a higher N2O release by denitrification than the coarse-textured soil. We assume that the fine-textured soil became anoxic at a lower soil moisture content than the coarse-textured soil. In conclusion, the effects of O2 partial pressure, soil moisture and soil texture were consistent with the theory that denitrification increasingly contributes to the release of NO and in particular N2O when conditions for soil microorganisms become increasingly anoxic. 相似文献
926.
Martin Vaupel Julia A. Vorholt R. K. Thauer 《Extremophiles : life under extreme conditions》1998,2(1):15-22
N
5,N
10-Methenyltetrahydromethanopterin cyclohydrolase (Mch) is an enzyme involved in methanogenesis from CO2 and H2 which represents the energy metabolism of Methanopyrus kandleri, a methanogenic Archaeon growing at a temperature optimum of 98°C. The gene mch from M. kandleri was cloned, sequenced, and expressed in Escherichia coli. The overproduced enzyme could be purified in yields above 90% in one step by chromatography on phenyl Sepharose in 80% ammonium
sulfate. From 3.5 g cells (250 mg protein), approximately 18 mg cyclohydrolase was obtained. The purified enzyme showed essentially
the same catalytic properties as the enzyme purified from M. kandleri cells. The primary structure and properties of the cyclohydrolase are compared with those of the enzyme from Methanococcus jannaschii (growth temperature optimum 85°C), from Methanobacterium thermoautotrophicum (65°C), and from Methanosarcina barkeri (37°C). Of the four enzymes, that from M. kandleri has the lowest isoelectric point (3.8) and the lowest hydrophobicity of amino acid composition. Besides, it has the highest
relative content of glutamate, leucine, and valine and the lowest relative content of isoleucine, serine, and lysine. Some
of these properties are unusual for enzymes from hyperthermophilic organisms. They may reflect the observation that the cyclohydrolase
from M. kandleri is not only adapted to hyperthermophilic conditions but also to the high intracellular concentrations of lyotrophic salts
prevailing in this organism.
Received: July 14, 1997 / Accepted: August 28, 1997 相似文献
927.
Dead cells do tell tales 总被引:14,自引:0,他引:14
The most recent major advances in the study of programmed cell death (PCD) in plants include the observation that peptide inhibitors of caspases inhibit the hypersensitive response. Nitric oxide has been shown to be required for the induction of disease related PCD. Mutant analysis has led to the cloning of the first genes involved in PCD related disease resistance, LSD1 and MLO. 相似文献
928.
Yury V. Matsuka Deborah A. Dilts Susan Hoiseth Rasappa Arumugham 《The protein journal》1998,17(7):719-728
An outer membrane PIA protein fromNeisseria gonorrhoeae strain FA19 was expressed inEscherichia coli and refoldedin vitro in the presence of zwitterionic detergent. Its proper folding and subunit organization was confirmed by comparison with the
native counterpart. The unfolding of PIA has been investigated using fluorescence spectroscopy and analytical size-exclusion
chromatography methods. Analysis of the denaturation pathway of the PIA revealed that it forms an unusually labile quaternary
structure. In the presence of 1 M guanidinium chloride (GdmCl) or upon heating up to 50°C, dissociation of the PIA oligomer
was observed resulting in the formation of folded monomeric intermediates. Unfolding of monomers occurs at 80°C or in the
presence of 4.3 M GdmCl, indicating high intrinsic stability toward both GdmCl and elevated temperatures. Both oligomeric
and monomeric forms of PIA exhibited affinity to the hydrophobic probe 1-anilinonaphthalene-8-sulfonic acid (ANS) and bind
withK
d=80 and 130 μM, respectively. Denaturation of the PIA completely abolished affinity to ANS, suggesting that hydrophobicity
is a property of the folded state of the porin. 相似文献
929.
I El Menyawi S Looareesuwan S Knapp F Thalhammer B Stoiser H Burgmann 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1998,706(2):2373
Previous studies have reported increased serum concentrations of nitrite/nitrate – the degradation products of nitric oxide – in Plasmodium vivax malaria and uncomplicated Plasmodium falciparum malaria. In all these studies, however, nitrite/nitrate has been measured spectrometrically using Griess reagent which carries major disadvantages in the determination of serum nitrite/nitrate. The method does not allow an exact differentiation of nitrite and biogenic amines that are physiologically present in plasma. In the present study we introduce high-performance liquid chromatography as a new, accurate and cost effective method for determination of serum nitrite/nitrate levels. Significantly increased nitrate concentrations were found in malaria patients and serum values remained above normal levels for at least 21 days. It could be shown that our HPLC method is a sensitive and cost-effective method for direct determination of nitrite/nitrate in serum samples, which is not influenced by the presence of biogenic amines. 相似文献
930.
In ribosomal protein S12 mutant or L24 mutant the expression of λN gene was depressed at translational level. To study its
mechanism the λN gene region of λN -lacZ gene fusion was trimmed from its 5′ end to 3′ end with DNA exonuclease III (DNA cxoIII) in order to alter the TIR (translational
initiation region) and the ding region of λN gene. After DNA sequencing 23 species of different λN-lacZ fused genes were obtained.
The β-galactosidase activities of these deletants in ribosomal protein mutant were compared with that in wild type strain.
The result indicated that (i) S12 mutant could affect 305 subunit’s binding to the TIR of λN gene messenger and cause the
difficulty in forming 30s initiation complex and then decrease the efficiency of translational initiation; (ii) in S12 mutant
the coding region of λN gene alw affected the expression λN gene; (iii) in L24 mutant the inhibition of λN gene expression
was not related to translational initiation and the 5′ end of the coding region of λN gene, but related to the 3′ end of λN
gene.
Project supported by the National Natural Science Foundation of China (Grant Nos. 39480014, 39570162) and Chinese Academy
of Sciences. 相似文献