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21.
Yoshihiro Kikkawa Hideki Abe Masahiro Fujita Tadahisa Iwata Yoshio Inoue Yoshiharu Doi 《Macromolecular chemistry and physics.》2003,204(15):1822-1831
Direct visualization of crystal growth in poly(L ‐lactide) thin films was carried out by using a temperature‐controlled atomic force microscopy (AFM). At the initial stage of crystallization, edge‐on lamellar crystals have nucleated and elongated. Subsequently, the edge‐on lamellar crystals showed S‐shaped morphology and changed their orientation from edge‐on manner to flat‐on one. The curvature of edge‐on lamellar crystal has been discussed in terms of inclination and distortion of polymer chains in the crystal. In addition, mechanism on the formation of flat‐on crystal from edge‐on lamellae was proposed as derivative growth on the basis of in situ AFM observation of crystal growth and enzymatic degradation.
22.
Farquhar J Finlay G Ford PA Martin-Smith M 《Journal of pharmaceutical and biomedical analysis》1985,3(3):279-285
A stability-indicating assay is described for the determination of N-acetylcysteine in aqueous pharmaceutical formulations. The sample is diluted to an appropriate concentration with dilute aqueous orthophosphoric acid. An aliquot of the solution, containing added l-tyrosine as an internal standard, is chromatographed using a 10-mum C(18) stationary phase with dilute orthophosphoric acid (pH 2.0) containing 0.5% w/v of sodium perchlorate as the mobile phase. The assay, which has a relative standard deviation of about 0.8%, can also be used as a test for related impurities in N-acetylcysteine. It is also suitable for determining the N-acetylcysteine content of the drug substance. 相似文献
23.
Summary The effect of human growth hormone on arterial basement membrane-like (BM) material was studied. BM-like material was obtained from the cell layer of cultured aortic myomedial cells using a sonication-differential centrifugation technique. After the addition of small amounts of growth hormone (1 ng/ml) to the cultures, we observed a 26% increased incorporation of amino acids into BM-like material (2p<0.005). However, further increase in the incorporation was not observed using either 3 ng or 10 ng growth hormone per ml. Growth hormone inhibited removal/degradation of BM-like material by 16% (2p<0.01). However, pinocytosis rate and activity of major lysosomal enzymes: cathepsin D, acid phosphatase and -N-acetyl-glucosaminidase were unchanged. Incorporation of glycosaminoglycans as evaluated by [35SO4]-labelling was reduced by 8% when cells were exposed to growth hormone (2p<0.01). The present study demonstrates an effect of growth hormone on the turnover and composition of BM-like material in cultured arterial myomedial cells. 相似文献
24.
Michael F. Powell 《Pharmaceutical research》1987,4(1):42-45
The degradation of lidocaine in aqueous solution obeys the expression k
obs = (k
H+[H +] + k
o ) [H+]/([H + ] + K
a + ko
K
a([H + ] + K
a) where k
H+ is the rate constant for hydronium ion catalysis, and k
o and ko are the rate constants for the spontaneous (or water-catalyzed) reactions of protonated and free-base lidocaine. At 80°C, the rate constants for these processes are 1.31 × 10–7
M
–l sec–1, 1.37 × 10–9 sec–1, and 7.02 × 10–9sec–1; the corresponding activation energies are 30.5, 33.8, and 26.3 kcal mol–1, respectively. It was found that the room temperature pH of maximum stability is 3–6 and that lidocaine is more reactive in the presence of metal ions such as Fe2+ and Cu2+. The dissociation constant, K
a, for lidocaine at 25–80°C was also measured at 0.1 M ionic strength and a plot of pK
a versus 1/T gave a slope of (1.88 ± 0.05) × 103 K–1 and intercept 1.56 ± 0.16. 相似文献
25.
研究了以甲基丙烯酸酯端基不饱和取酯树脂为主链,用甲基丙烯酸甲酯取代苯乙烯作为交联剂制成的甲基丙烯酸酯树脂(MAER)与通用型不饱和聚酯树脂(GUPR)的热裂解机理、燃烧现象。结果表明:MAER的裂角产物中苯环化合物含量(14.9%)少于GUPR(74.5%)。MAER燃烧时的发烟量和毒性也远低于GUPR。在MAER中加入三水合氧化铝(ATH)后,裂解产物中有毒物质的各类和数量更少,在燃烧时只有少量 相似文献
26.
血中纤维蛋白降解产物和D—二聚体水平对硅沉着病早期诊断意义 … 总被引:4,自引:1,他引:3
目的:探讨纤维蛋白降解产物(FDP)和D-二聚体(D-Dimer)两项指标在硅沉着病(原称矽肺)早期诊断中的意义和价值。方法:用ELISA法测定正常人、接尘工人和不同期别的硅沉着病病人血中FDP和D-Dimer含量变化并测定其他指标。结果:硅沉着病早期FDP和D-Dimer水平很高,随着硅沉着病的晋期,FDP和D-Dimer水平逐渐下降。结论:FDP和D-Dimer作为硅沉着病早期诊断指标具有一下 相似文献
27.
Several approaches to the separation of four stereoisomers, 1–4, of a novel, topically active, carbonic anhydrase inhibitor, 1, with two chiral centers in the molecule and four isomers, 5–8, of its chiral metabolite, 5, were evaluated. These methods include nonchiral derivatization followed by separation on chiral stationary phases (CSPs) and chiral derivatization and separation on nonchiral columns and on CSPs. Baseline separation of stereoisomers 1–4 was achieved in less than 15 min after chiral derivatization with (S)-(+)-l-(l-naphthyl)ethyl isocyanate (NEIC) and chiral chromatography on a (R)-N-(3,5-dinitrobenzoyl)phenyl glycine (DNBPG) column under normal phase (NP) conditions. Similarly, isomers 5-8 were baseline separated in less than 20 min after derivatization with NEIC and chromatography on nonchiral (nitrophenyl) and chiral [(S)-(3,5-dinitrobenzoyl)leucine; DNBL] columns in series under the same NP chromatographic conditions. Only partial separation of the diastereomeric derivatives was observed on a variety of nonchiral columns. In addition, all other direct and indirect chiral separation approaches gave only partial separation of at least two stereoisomers within the group of 1–4 or 5–8. The details of chiral separations using various methods and separation () and capacity factors (k) of the derivatized isomers 1–8 on a series of chiral and nonchiral columns are presented. Using these methods, the absolute configuration of the human metabolite of 1 was established as S
1
S
2 (5), and the heat (HD) and light (LD) degradation products of 1 as R
1
S
2 (3) and S1
S
2 (5), respectively. 相似文献
28.
Marianne Dalene Kristina Jakobsson Agneta Rannug Gunnar Skarping Lars Hagmar 《International archives of occupational and environmental health》1996,68(3):165-169
The object of this study was to investigate whether exposure of pipe-layers to thermal degradation products of diphenylmethane diisocyanate (MDI) could be assessed by analysing 4,4-methylenedianiline (MDA) in hydrolysed plasma and urine, and whether the genotype for N-acetylation affected these biomarker levels. Blood and urine samples were drawn from 30-pipe-layers who had been welding polyurethane (PUR) insulated pipes during the preceding 3 months. MDA in hydrolysed plasma and urine was determined with a gas chromatography-mass spectrometry technique, and genotype for N-acetylation was analysed with a polymerase chain reaction technique. MDA in plasma was detected in 18 of the 30 pipe-layers. Their plasma concentrations of MDA varied from 0.05 to 8.48 g/1. There was a significant negative correlation between time since last welding of PUR-insulated pipes and P-MDA (r
s = 0.50, P = 0.005). There was also a significant positive correlation between the estimated number of welded PUR-insulated pipes during the preceding 3 months and P-MDA (r
s = 0.68, P = < 0.001). No significant association between genotype of N-acetylation and P-MDA was observed in a multiple regression analysis when adjustment was made for the estimated cumulative exposure to thermal degradation products of MDI. MDA in urine was detected in only four of the 30 pipe-layers. These four subjects had been welding PUR pipes on the same day as the sampling, or on the day before. The present results indicate the spot plasma samples analysed for MDA may give a rather good estimate of exposure to MDI during the preceding months. P-MDA, but not U-MDA, therefore seems to be a useful biomarker of long-term exposure to MDI. The individual N-acetylation capacity did not affect the plasma levels of MDA. 相似文献
29.
Summary Six patients with recently ruptured intracranial aneurysms were treated preoperatively with tranexamic acid (AMCA). Two patients received 6 g daily in i.v. infusion, two had 6 g daily by i.v. injection, and two patients were given AMCA 9 g daily by mouth during the first week after bleeding. Serial assays of AMCA and fibrin/fibrinogen degradation products (FDP) in cerebrospinal fluid (CSF) were performed during 6–13 days after the initial subarachnoid haemorrhage (SAH). Judged from the decline in CSF-FDP, an assumed therapeutic level of 1 mg/l of AMCA in CSF was reached within 24–36 hours after the first dose when the drug was administered intravenously and within 48 hours when the drug was given orally. 相似文献
30.
S. A. Volgushev V. A. Kosykh E. A. Podrez D. K. Novikov S. M. Khlynin R. S. Karpov 《Bulletin of experimental biology and medicine》1991,111(3):313-315
Research Institute of Cardiology, Tomsk Scientific Center, Academy of Medical Sciences of the USSR. Research Institute of Experimental Cardiology, All-Union Cardiologic Scientific Center, Academy of Medical Sciences of the USSR, Moscow. Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 111, No. 3, pp. 254–256, March, 1991. 相似文献